Programme
Tuesday 13 October 2026
13.10.2026
08:30 - 10:00
Room 0.4
Congress Conference
A. Sustainable solutions to environmental challenges
INNOVATIVE TECHNIQUE OR PROJECT
Chairmen : François RENAULT (Nanterre, France), Reza TAHERZADEH (Chatenay Malabry, France)
08:30-08:40
Introduction
08:40-09:00
Carbon Reduction and Innovation: The Successful Challenge of the Chiltern Tunnels in Addressing Environmental Challenges (UK)
Karine BEN KEMOUN (Guyancourt, France)
09:00-09:20
Performance-Based Durability Assessment of Low-Carbon Tunnel Segment Concrete for the Grand Paris Express
Thomas PERNIN (Epernon, France)
09:20-09:40
Design and Construction of the Montreal Blue Line Extension
Verya NASRI (Jersey City, United States)
09:40-10:00
Refurbishment of a TBM: feedback and life cycle analysis applied to the TBM for the Grand Paris Express Line 18-3A
Clement GAUDRY (Paris, France) Lucille BAUCAL--POYAC (Bron, France)
As part of the HS2 project, the new high-speed rail linking London to Birmingham, the Chiltern Tunnels illustrate the ambitious integration of sustainability in a major infrastructure site. Led by Bouygues Travaux Publics (BYTP) and its partners Sir Robert McAlpine and VolkerFitzpatrick (ALIGN consortium), this project aims to reconcile technical performance with environmental objectives, with a clear goal: drastically reducing its carbon footprint. Key measures included design optimization (reduced concrete volumes, steel fibres in segments, and rationalized cross-passages), use of low-carbon materials (GGBS concrete), alternative fuels, and 100% green electricity. Spoil and water management were redesigned to protect the aquifer: the FLOPAM polymer replaced lime and sulfuric acid, improving safety and reducing emissions, while a closed-loop system recycled most of the slurry. Circular economy and biodiversity measures created 127 hectares of grasslands and wetlands, achieving an 86% biodiversity net gain. Overall, these initiatives avoided over 475,000 CO₂ tons, a 45.5% reduction from the baseline, demonstrating that sustainability can be achieved without compromising technical performance or safety, and providing a transferable experience for future infrastructure projects. --- This paper presents the development of a low-carbon, steel fiber-reinforced concrete designed for the XA3 exposure conditions of the Grand Paris Express – Line 15 tunnel segments. Using the performance-based methodology FD P18-480, the CEM III/A formulation—non-compliant with prescriptive binder limits—was shown to meet all required mechanical and durability criteria, including chloride ion migration and flexural Class 4c performance. Sensitivity analyses confirmed robustness to typical batching variations. A carbon assessment (A1 module) indicates a 53% reduction in CO₂ emissions compared with a traditional CEM I segmental concrete. These results demonstrate the suitability of performance-based approaches for deploying reliable, low-carbon solutions in major underground infrastructure projects. --- Several mega transit projects are currently under design or construction in soft rock of Montreal, Canada. An innovative design method to reduce the excavation, the volume of concrete and the carbon footprint of the construction has been adopted for these projects resulting in significant cost and time saving and a more sustainable infrastructure. The main principle of this method is to only use permanent structural elements in the design of initial excavation support such as permanent bolts combined with permanent shotcrete and spray on waterproofing membrane. The mechanical and hydraulic properties of local rock allow for a drained design concept, and this has been successfully implemented in the existing underground transit structures in Montreal. Rock mass grouting is used to bring down the water infiltration to an acceptable level; this is combined with applying drainage strips over the rock leaking fractures to relieve the hydrostatic pressure. An additional drainage grid is sandwiched between the layers of shotcrete to make sure the final liner surface remains dry. This method had been successfully applied to all the new metro projects in Montreal including 3 underground stations of Réseau express métropolitain (REM) project ($9.3 B), 5 underground stations, 5 emergency exit buildings and one NATM tunnel of Blue Line Extension project ($7.6 B) and 8 underground stations of REM Est project ($10.0 B). The application of this locally adopted tunneling method resulted in significant cost and schedule savings, and as much as 67% decrease in liner carbon footprint which constituted a major success. This paper discusses the design and construction details of this New Montreal Tunneling Method and its obvious benefits to the underground engineering. --- The civil engineering sector is facing increasing sustainability requirements, particularly in large-scale infrastructure projects such as tunnel construction. Historically, tunnel boring machines (TBM) were designed for single use. Today, this practice is changing. Lot 3A of Line 18 of the Grand Paris Express (GPE) is a concrete example: the tunnel boring machine used to dig the 6.7 km of this section was refurbished after digging 6 km on Lot 1 of the same line. This TBM is the case study for this article. It provides feedback on the refurbishment and reuse of a tunnel boring machine on a second site in the immediate vicinity, without returning it to the manufacturer. It describes the organisation put in place, the technical and scheduling challenges, and the role of each of the parties involved. The quality control and validation methodology used by the project designer and the project owner will also be discussed. Secondly, the Life Cycle Assessment (LCA) methodology was applied to this case study in order to assess the potential environmental impacts and quantify the benefits of reuse, comparing the environmental performance of a new tunnel boring machine with that of a refurbished one. This study therefore aims to provide a comprehensive understanding of the technical, organisational and environmental issues associated with reuse.
13.10.2026
08:30 - 10:00
Room 0.5
Congress Conference
B. Technological and digital innovations in underground work
NEW DIGITAL TECHNOLOGIES
Chairman : Pierre TISSIER (Lyon, France), Nataliya DIAS (Chatenay-Malabry, France)
08:30-08:40
Introduction
08:40-09:00
Use of 3d model generated at tunnel front face for geological tunnel face mapping and further developments – case study of TELT CO08
Arnaud HOCHART – Implenia (Le Bourget Du Lac, France)
09:00-09:20
Artificial intelligence for underground works
Florent ROBERT – Cetu (Bron, France)
09:20-09:40
Human-centered Digitalization in Tunnelling
Charlotte KIESELE (Schwanau, Germany)
09:40-10:00
Is it worth implementing a digital twin for road tunnel operation?
Florent ROBERT (Bron, France)
Accurate observation of ground conditions at the tunnel face is essential for defining temporary support in drill-and-blast tunneling. Traditional geological face mapping relies on geologist observations which present limits in term of precision and consistency. Georeferenced 3D models generated directly at the face offer a faster, safer, and more accurate alternative, improving documentation quality and design decisions. On the TELT C008 project, Implenia and partners standardized tunnel face mapping by photogrammetry. This large-scale 3D geological model enables early detection of anomalies, supports back-analysis, and helps refine support strategies. It also provides measurable records for verifying support installation, profiling shotcrete thickness, and improving quality control. Photogrammetry simplifies the production of as-built documentation, unfolded views, stereograms, and accurate overbreak evaluations. It further contributes to a digital twin integrating all construction stages within a BIM-compatible framework. The paper presents implementation methods, challenges, and the evolving role of photogrammetry as a multi-purpose digital tool that strengthens safety, accuracy, collaboration, and long-term asset management. --- Artificial intelligence (AI) is profoundly transforming engineering professions, and the underground works sector is no exception. This trend is all the more significant in this field, where the technical challenges, human risks and environmental constraints are particularly high. By integrating AI, project managers and contractors can optimise planning, improve safety and increase productivity on underground sites. One of the main advantages of AI is its ability to perform predictive analyses. By exploiting geotechnical, historical and real-time data, the algorithms are able to anticipate ground movements, detect structural anomalies or predict wear and tear on equipment. This capability helps to avoid accidents, reduce unscheduled stoppages and optimise digging methods according to ground conditions. We present four use cases where AI is being used operationally on construction sites. These are: Detecting the clogging of a TBM; Predicting settlement as work progresses; Using a ‘Ground Machine Interaction’ indicator for tunnel boring machines; Optimising the advance speed of an earth pressure tunnel boring machine as a function of geology. These four use cases illustrate how AI is currently being deployed on real construction sites, and help us to understand its advantages and limitations. Finally, an analysis of the regulatory and legal issues associated with the use of AI and data is proposed. --- Digitalization in tunnelling is accelerating—but often in directions that overlook the real levers for improvement. While advanced solutions like AI-powered monitoring and digital twins are being developed for complex, infrequent edge cases, the day-to-day efficiency losses are frequently underprioritized. In practice, project teams struggle not only with slow or fragmented information flows, but with limited access, poorly structured interfaces, and non-intuitive data representations. This contribution calls for a redirection: toward pragmatic, human-centered IoT platforms that focus on simplifying the operational reality—not adding layers of complexity. Interfaces must be clean, logic-driven, and role-specific. Transitions between digital systems and physical processes should be seamless and standardized, not improvised. AI bots and context-aware logic can deliver real value—only when embedded within accessible, well-designed tools. Bridging OT, IT, and IoT environments in tunnelling requires more than integration; it demands design thinking. The goal isn’t just data collection—it’s clarity, speed, and relevance. By prioritizing user experience and modular standards, digitalization can finally become a tool that accelerates the site instead of slowing it down. --- While Building Information Modelling is becoming increasingly widespread in underground infrastructure projects, the use of Digital Twins for tunnel operation remains at an early and largely experimental stage. Their ability to enhance asset management, support incident analysis and maintenance strategies, and ensure seamless digital continuity has yet to be demonstrated under real operating conditions. In this context, a collaboration has been initiated between the Centre d’Études des Tunnels (CETU) and the Société Française du Tunnel Routier du Fréjus (SFTRF) to design, test, and evaluate a digital twin applied to an operational road tunnel. The Fréjus Road Tunnel, consisting of two tubes, one in service since 1980 and a second recently opened in 2025, provides an ideal case study. The coexistence of legacy and modern structures, combined with technical systems, offers a realistic environment for experimenting with DT concepts. The objective of the project is to develop a functional digital twin integrating both static and dynamic data. The first phase focuses on BIM modelling of a representative section, with particular emphasis on equipment, especially the ventilation system, whose digital behaviour aligns closely with existing DT applications in the building and industrial sectors. Subsequent stages will gradually extend the scope to additional equipment and, later, to the civil engineering structures. This initiative forms part of the CETU’s broader digital transformation strategy and aims to deliver concrete feedback for the tunnelling community. It also seeks to identify the technical and organisational barriers specific to underground assets and propose operational solutions to overcome them.
13.10.2026
10:00 - 11:00
COFFEE BREAK
COFFEE BREAK
13.10.2026
10:10 - 10:50
e-poster station 1
Commented e-posters
COMMENTED E-POSTERS SESSION 3
10:10 - 10:18
Durability of sprayed concrete for the rehabilitation of old railway tunnels
Julie PHAMMAVANH - Sncf Réseau (La Plaine Saint Denis, France)
10:20 - 10:28
Towards a more reliable carbon footprint: A review of the gaps between forecasts and reality
Rémi LE GARS - Setec Als (Lyon, France)
10:40 - 10:48
Safety upgrade works of the Grand’ Mare road tunnel in Rouen
Céline MUSEUX-CASTEL - Setec Tpi (Paris, France)
The French National Railway Network includes over 1,090 operational tunnels, with an average age exceeding 135 years. Since the 1970s, many of these tunnels have been reinforced with sprayed concrete (shotcrete) to extend their service life. While laboratory studies on shotcrete durability are widespread, long-term in situ assessments remain limited. This study reports results from a nationwide testing campaign on core samples from nine representative railway tunnels across France, covering diverse geological and environmental conditions. The investigation focused on key degradation mechanisms affecting shotcrete durability in underground railway tunnels. Laboratory analyses included compressive strength, bulk density, porosity, chemical composition, carbonation depth, freeze–thaw resistance, and water aggressiveness. The results show that chloride ingress, carbonation, sulfate attack, and alkali–silica reactions were generally limited, indicating low immediate risk in the studied assets. However, the compressive strength tends to decrease with the age of shotcrete, due to changes in materials and construction methods and, possibly, as a result of leaching, which dissolves the cement paste, increases porosity, and thus promotes the development of other degradation mechanisms. Freeze–thaw resistance was generally low and variable, while steel fibers appeared to enhance performance. These findings emphasize the importance of characterizing environmental conditions, mix design, and application quality to ensure the long-term durability of shotcrete. They provide important guidance for asset maintenance strategies and rehabilitation planning of aging tunnel infrastructure. --- The Mont-Cenis Base Tunnel, the main work of the new Lyon-Turin railway line managed by Tunnel Euralpin Lyon Turin (TELT) is a perfect example of a large-scale project whose intrinsic value is linked to the environmental gains generated by the modal shift from the road to the rail in relation to the emissions induced by its completion, for which the carbon footprint is the model of the calculation tool. This article presents the framework and methodology for calculating greenhouse gas emissions during design phase and execution phase of operational sites 6 and 7 of the TELT project, in order to highlight the challenges and difficulties that can be encountered on a construction site of this scale, as well as the sources of bias observed between the assessments for the different phases of the project. During the design phase, quantity estimates can only be made on the basis of design studies and feedback from similar projects, leading to a potentially substantial margin of error in greenhouse gas emission assessments. During the execution phase, the monitoring system put in place by the construction companies is key to ensuring the reliability of the quantities taken into account in the calculation of emissions, but it is also the greatest difficulty in a large-scale project. In both cases, defining the scope of the assessment and ensuring the reliability of the quantities used remain essential to guarantee the consistency of the results and associated conclusions. A closer look at the assumptions used to calculate emissions from concrete and steel does not invalidate any particular method, but rather highlights the need to take a step back when interpreting the results, which is closely linked to the choice of emission factors and quantities considered. --- The Grand’ Mare Tunnel is a dual-tube unidirectional road tunnel, each tube comprising two traffic lanes, with a length of 1,534 m for the uphill tube and 1,516 m for the downhill tube. The tunnel has a clearance of 4.50 m and is closed to vehicles transporting dangerous goods (Category E). Setec tpi and terrasol have been providing full project management services for Phase 2.2 of the safety upgrade works of the Grand’ Mare road tunnel since early 2020. The construction contract, awarded by the Interdepartmental Road Directorate North-West (DIRNO) to the EIFFAGE consortium, was carried out between 2021 and 2024. Phase 2.2 primarily consisted in the construction of seven new intertube cross‑passages and the installation of their associated safety and operating equipment, together with the full replacement of the tunnel’s ventilation system and the upgrade of the SCADA system to integrate both the modifications made to refurbished subsystems and the newly deployed installations. All these works were carried out while the tunnel remained in operation, in compliance with the minimum operating conditions. For the excavation of the intertube cross-passages, in addition to being carried out mostly under traffic, the excavation and support methodologies required tailored and specialised solutions, due on the one hand to the relatively small cross-sectional area of the passages (13 m²), and on the other hand to the steep gradients (up to 45%) affecting many of them, resulting from the increasing elevation difference between the two tubes towards the northern portal. Finally, regarding tunnel equipment, the implementation of airflow control for the ventilation and smoke extraction system was primarily driven by the need to simplify the minimum operating conditions, in view of the very frequent traffic congestion within the tunnel.
13.10.2026
10:10 - 10:50
e-poster station 2
Commented e-posters
COMMENTED E-POSTERS SESSION 3
10:10 - 10:18
Comparative analysis of different 2D and a 3D structural modelling for tunnel segmental ring design
Joe KHALIL - Systra France (Paris, France)
10:20 - 10:28
Basal heave analysis in deep circular shafts: a case study of a ventilation shaft along the Grand Paris Express Line 15 West-South Section
Amine BEN YUSEF - Geos Ingénieurs Conseils (Rueil-Malmaison, France)
10:30 - 10:38
Reconstruction, extension, and widening of an avalanche gallery converted into a tunnel at Lautaret pass
Guillaume CHAMPAGNE DE LABRIOLLE - Arcadis Esg (Lyon, France)
10:40 - 10:48
3D Structural Modeling for Post Drilled Rebar Design at Tunnel–Cross Passage Interfaces
Joe KHALIL - Systra (Paris, France)
In shield-driven tunnel linings, the behaviour of segmental joints is of main importance for the segmental lining design. The lining ring is composed of individual segments connected to each other via longitudinal joints. Modelling of a homogeneous ring without a consideration for the effect of the joints leads to higher structural internal forces. To account for the effect of longitudinal joints in-between segments, two main methods are used: Muir-wood method, using a homogenized flexural rigidity of the ring. This method is usually combined with a transfer ratio ζ, representing the bending moment redistribution between longitudinal joints and across adjacent rings. Janssen method, modelling longitudinal joints by means of hinges with rotational stiffness, resulting in non-linear behavior that depends on the geometry of the contact and the load. This study presents a comparative analysis between both methods and a complete 3D structural model in a driven tunnel in Grand Paris area, in addition to several methods for estimating the transfer ratio. --- The West-South section of the Grand Paris Express Metro Line 15 was awarded by Société des Grands Projets (SGP) to a consortium that includes GEOS, responsible for the construction of a ventilation shaft located in between the suburbs of Nanterre and Puteaux. The circular shaft is embedded in a heterogeneous soil layer known as “Fausses Glaises” (FG). Excavation reaches 50 meters, intersecting the groundwater table 23 meters above the wall base and 12 meters above the excavation level. FG consists of clayey intercalations within a sandy-silty matrix with poor shear strength. For deep circular shafts, the Prandtl failure mechanism for basal heave verification was found unsuitable. Although French standard NF P94-282 acknowledges this limitation, it proposes no adaptations for circular diaphragm walls. Calculations using this analytic method indicated a safety factor of 0.5, resulting in failure. Consequently, a finite element analysis was performed using PLAXIS 2D with an axisymmetric model and a deformation analysis. This approach accounted for ground water flow through sandy layers (drained parameters) and clayey layers (undrained parameters). A safety analysis confirmed a significant effect of shape on basal heave stability in circular shafts. Finally, a parametric study proposed a modified plastic failure mechanism for circular excavations in fine-grained soils, prior to introducing a simplified analytical approach incorportating shape factor, excavation depth, and seepage effects. --- On the RD 1091, the “Lautaret Pass” reaches an altitude of 2058 meters in the Hautes-Alpes department (France). Its purpose is to remain open throughout the winter (2nd highest French pass with this requirement). To combat snowdrifts, an avalanche gallery was built in 1964 and then extended in 1976 to reach 380 meters. It is an openwork gallery on the downstream side, consisting of a 3.50-meter-wide gravity wall, a 50 cm prestressed concrete roof, and columns on shallow or semi-deep foundations on the downstream side. Nearly 60 years later, as the structure was in poor condition and snow drifts were not sufficiently controlled, the CD05, assisted by its project management advisor Elegia Group, launched a design-build competition in 2022 to: Construct a closed tunnel in place of the existing structure, extending it by 110 meters towards the Lautaret Without interrupting traffic during the construction seasons from April to October This competition was won by the Razel-Bec / Arcadis / Stam / Lavigne-Chéron consortium, whose main approach was to regenerate the upstream gravity wall and to opt for a largely prefabricated structure founded on micropiles where bedrock is deep. The consortium also carried out the complete design of the equipment and handled the tunnel safety dossier submission. --- To connect the main tunnel to a cross passage, several construction methods can be employed. One such method involves the use of post drilled reinforcement bars to resist shear forces at the interface between the two structures. Designing this connection and determining the required reinforcement necessitates the use of a 3D structural model that accounts for interface between the tunnel and the cross-passage variation along all three spatial axes. This study presents detailed 3D models for various cross passage geometries, analyzes the 3D projection of forces transferred from the tunnel along the contact interface, and compares reinforcement design approaches based on the Eurocodes and the Model Code. The objective is to evaluate the influence of cross passage geometry and the selected design methodology on the required reinforcement, within the framework of applicable regulatory codes.
13.10.2026
10:10 - 10:50
e-poster station 3
Commented e-posters
COMMENTED E-POSTERS SESSION 3
10:10 - 10:18
HyperB’Assist™: The essential tool for hyperbaric interventions in tunnel boring machines
Jean-Camille BROCHARD (Saint-Jory, France)
10:20 - 10:28
Integration of soil elastic anisotropy into the HSM constitutive law: application to the new Metro Line C in Toulouse, France
Abdelilah ERRAHALI - Univ Gustave Eiffel, Gers-Sro, F-77454 Marne-La-Vallée, France (Neuilly-Plaisance, France)
10:30 - 10:38
Optimizing rock valorization by accurate pre-characterization strategy on a transalpine tunnel
Claire GUILLIN - Arx (Saint Martin De La Porte, France)
10:40 - 10:48
Innovative Low-Carbon Concretes and Performance-Based Approach: A Combined Strategy for Durable and Environmentally Sustainable Underground Structures
Nadia MASSOUSSI - Artelia (Choisy-le-Roi, France)
In underground construction projects using Earth Pressure Balance (EPB) and Slurry Tunnel Boring Machines (TBMs), hyperbaric maintenance operations are inherently complex, high-risk activities that are subject to increasingly stringent regulatory requirements. These interventions demand rigorous management of procedures, personnel qualifications, safety measures and operational traceability. To address these challenges, BESSAC, through Tunnel Factory innovation program, has developed HyperB’Assist™, a digital platform dedicated to the preparation, monitoring and management of hyperbaric interventions. Designed to provide real-time assistance to air-lock operators, the solution enhances operational safety while ensuring compliance with applicable regulations. HyperB’Assist™ supports teams throughout the entire intervention process, including verification of personnel qualifications and medical fitness, intervention planning and preparation, real-time monitoring of critical parameters, automatic calculation of decompression schedules, generation of alerts in the event of abnormal conditions, and automatic generation of intervention reports. The platform also ensures full traceability through automatic data recording and generation of detailed intervention reports. Already deployed on several tunnelling projects and compatible with TBMs from various manufacturers, HyperB’Assist™ significantly improves the safety, regulatory compliance and reliability of hyperbaric operations while providing a standardized and efficient management framework across projects. --- Population growth and urban densification are driving increased use of underground infrastructures. However, tunnel excavation in urban environments causes ground deformation that can lead to surface settlement and affect the stability of existing structures, particularly deep foundations. Despite extensive modelling work, reliably predicting these deformations remains a major challenge. Recent research has highlighted the importance of mechanical anisotropy in the formation and geometry of settlement troughs. Taking into account reduced shear stiffness between the vertical and horizontal directions leads to narrower troughs than those obtained using isotropic models. Parametric studies have confirmed the decisive influence of this anisotropy on soil response. In practice, the Hardening Soil Model (HSM) is widely used by engineers because of its robustness, its simplicity of calibration from laboratory tests, and its implementation in many calculation software packages. This justifies proposing a model formulation that explicitly incorporates transverse isotropy in order to better represent the actual behaviour of soils. This paper aims to propose an anisotropic extension of the HSM, while retaining the structure and mechanisms of the original model. The evaluation of this new model is based on its application to the case of the new Toulouse metro line, allowing evaluation of its ability to accurately reproduce the observed settlement trough in terms of depth, width, and overall shape. --- CO6 and CO7 are two of the nine operational construction sites dedicated to excavating the ongoing Lyon-Turin transalpine railway line base tunnel, between France and Italy (TELT = Tunnel Euralpin Lyon-Turin). This bi-tubes tunnel (57.5 km-length) is bored within the Alps, by both conventional and TBM excavation methods. CO6 and CO7 (VINCI CONSTRUCTION and WEBUILD contractors) sites are the longest section (ca. 20 km-length) of the French side of the right of way of the base tunnel, between Saint-Julien-Montdenis and Modane (Western Alps). Starting in 2021, CO6/7 excavation operations are expected to generate approximately 11 Mt of rocks by the end of the project, within a highly complex and space-related changing geological background. The aim of the present paper is then to display the different stages of the ongoing strategy for the pre-characterization of the excavated rocks on CO6 & CO7. This process is divided into several stages. During the Tender phase, preliminary geological exploration (on field and by core drilling from ground surface) - this phase was done years prior CO6 and CO7 excavation sites took place. Here the main purpose is the identification of the reuse potential of geological units. Their macro-characteristics analysis will help to determine the compatibility with aggregate manufacturing or earthworks depending on the class of the material (four different classes defined in our contract). Then, during the execution phase, by sampling the destructive and core drilling performed during investigation phases, we then tend to precise these characterizations. Pre-characterization is based on coupled mechanical, chemical, and mineralogical data through every work and part of the tunnel. Finally, the pre-characterization is confirmed by investigating the excavation faces with visual inspection combined with mechanical characterization. Establishing production planning (excavated and evacuated rocks amount), is crucial for the project to design valorization flows and processes efficiency. --- With millions of tons of concrete used every year in major underground construction projects, reducing the carbon footprint has become a key strategic objective. Construction companies are increasingly adopting innovative low-carbon or ultra-low-carbon concrete mixes, incorporating mineral additions and optimizing binder content to reduce CO2 emissions from the early design phase. By combining low-carbon concretes with a performance-based approach, they are pioneering a new construction model: more sustainable, more responsible and more in line with carbon neutrality objectives, while maintaining the required structural performance. In this context, the article explores the complementarity of these two levers and briefly highlights the relevance of considering the carbon footprint as a true performance criterion, on par with mechanical strength and durability. This approach places environmental performance at the core of infrastructure project priorities.
13.10.2026
10:30 - 11:00
Agora
Lecture
LECTURE - SAINT-GOBAIN
LECTURE - SAINT-GOBAIN
13.10.2026
11:00 - 12:30
Room 0.4
Congress Conference
B. Technological and digital innovations in underground work
EXPERIMENTS AND DIGITAL MODELLING (PART 1)
Chairmen : Nicolas BERTHOZ (Bron, France), Pierre TISSIER (Lyon, France)
11:00-11:10
Introduction
11:10-11:30
TBM–Soil–Pile Interaction under Steady-State and Transient Conditions: 3D Numerical Modelling and Experimental Validation
Ali ABDALLAH - Centre D’études Des Tunnels (cetu), 25 Avenue François Mitterrand, 69500 Bron, France (Bron, France)
11:30-11:50
French Research Project E-PILOT: Static and Dynamic Experimental and numerical studies of Tunnel – Deep foundations interaction
Alain LE KOUBY (Paris, France)
11:50-12:10
Analytic method for estimation of settlements of bored tunnels in soft soil
Pierre ARISTAGHES - Bouygues Tp (Guyancourt, France)
12:10-12:30
Numerical study of the influence of temporary support stiffness on the short- and long-term loading of the final lining – The case of drifts excavated in Callovo-Oxfordian claystone
Blaise-Pascal ALLO (Marne-La-Vallée, France)
Predicting the impact of tunnel boring machine excavation on deep foundations is still a current topic in urban tunnelling. Such predictions usually necessitate a numerical analysis of the interaction between the TBM, soil and foundation due to the complexity of the mechanisms involved. This paper presents a numerical model recently developed by ENTPE and CETU to address this issue. While this 3D numerical model is based on well-established methods for modelling TBM–soil interaction, what makes this work original is the way the modelling choices and boundary conditions — intended to replicate the action of the TBM in the field — were defined, calibrated and validated using full-scale experimental observations from the TULIP research project. The modelling procedure was developed based on a rigorous phenomenological analysis of the observed responses of the soil and piles, including surface settlements, subsurface displacements, and pile behaviour (displacements and forces). The developed model satisfactorily reproduces the soil displacements and pile–soil interaction mechanisms observed at the TULIP experimental site under both quasi-stationary excavation conditions and transient accidental events (pressure drops in the excavation chamber, increase of the grouting pressure). The study also emphasises the importance of certain modelling choices, such as using a nonlinear elastic–plastic soil model (HSM type) and implementing an elastic–plastic pile–soil interface model with normal and tangential stiffness and a sliding threshold calibrated from qs values. It also highlights the need to explicitly consider confined water–soil fluid along the shield. --- Urban centers in major cities worldwide are progressively densifying, due to the enormous population growth over the last years. These changes strain existing infrastructure, requiring expansion or construction of new underground transportation systems, for example in Paris and Toulouse. , tunnel excavation near adjacent structures and in particular piled structures outcomes could be significantly limited or controlled by predicting foundations behaviour during and following tunnel construction as well as operations phases. In particular, it would help to limit financial provision for constructions phases and improve environmental performance of the infrastructure project. In this context, the Gustave Eiffel University has set up a research project called E-PILOT (Study of the impact on Piles During the passage of a Tunnel Boring Machine), funded by the ANR, which brings together 10 partners (the Gustave Eiffel University, the University of Lille (LGCgE), the Cerema, the CETU, the ENTPE, GDS, Itech, Terrasol, SGP, Tisséo Ingénierie) to deepen the understanding of the mechanisms of interaction tunnel boring machine-soil-foundations. The research work proposed by the consortium will help to manage impact on existing structures during tunnelling and tunnel operation phase in the framework of actual important infrastructure projects in a metropole area. --- The calculation of settlements induced by tunnels excavated with a TBM is carried out using two types of methods: empirical methods, with all the limitations of this type of "black box" method, based on an assumed "ground loss" factor ; numerical methods, adapted to various geotechnical configurations. Analytical methods exist, but they generally require intermediate parameters such as convergence and ovalization, which refers to the limitations of empirical methods. The proposed method is purely analytical and needs only measurable parameters. It provides settlements that are relatively close to the results obtained by finite element calculations, except in the cases of very shallow tunnels, or of soils covered by a layer significantly stiffer than the excavated soil. Apart from these cases, the deviations are within the required accuracy for settlements, and negligible compared to the precision with which the moduli of soil layers are generally determined.It allows to study easily a great number of sections, and simplifies retro-analysis of measured settlements. --- The Meuse/Haute-Marne Underground Research Laboratory has been operated by Andra since the early 2000s to investigate the feasibility of a deep geological disposal for radioactive waste in the Callovo-Oxfordian claystone (Cigéo project). The laboratory consists of a network of drifts excavated along the directions of the principal horizontal in-situ stresses. Observations have shown that drift excavation induces the development of an asymmetric fractured zone around the openings, leading to anisotropic convergence depending on the drift orientation. To investigate the interaction between the rock mass and the support system, several experimental drifts have been dedicated to testing different support systems. Monitoring of these drifts includes convergence measurements, as well as stress and strain measurements within the supporting structures. The analysis of in situ measurements, complemented by numerical simulations, highlights the role of compressible wedges installed in the shotcrete support on the mechanical response to both the temporary support and the final lining. The implementation of various experimental configurations in a numerical model, in which the fractured zone induced by excavation is explicitly represented, makes it possible to assess the long-term response of the various support structures.
13.10.2026
11:00 - 12:30
Room 0.5
Congress Conference
C. Opportunities offered by the city and underground infrastructures
URBAN PLANNING AND USE
Chairman : Michel DEFFAYET (Lyon, France), Arnaud TAILLANDIER (Chambery, France)
11:00-11:10
Introduction
11:10-11:30
The S-PASS research project: resources and uses of the subsurface in the Grand Paris metropolitan area
Jocelyn BARBARAND - Brgm (Orsay, France)
11:30-11:50
Planning the Invisible City: Underground Energy Infrastructure as a Strategy for Urban Futures
Antonia CORNARO - Amberg Engineering (Zurich, Switzerland)
11:50-12:10
Reuse and Repurpose of Underground Space
Wout BROERE (Delft, The Netherlands)
12:10-12:30
Promoting the work of the National Project Ville 10-D
Jean-François DAVID (Paris, France), Monique LABBE (Paris, France)
For the city, the subsoil represents fundamental challenges for its development and evolution. It is the foundation for surface developments, a place that houses public transportation and technical networks. It is also a source of geothermal energy that is still insufficiently exploited in urban areas. In the context of climate change, the effects of which will be particularly marked over the coming decades in major metropolises, the subsoil can also become a new space to be developed as an alternative to urban sprawl. The S-PASS scientific research project, part of the “Subsurface: a common good” research program funded under the France 2030 plan, is built around these issues, on the geographical perimeter of the Greater Paris metropolis. The project covers the first 200 m of the subsoil, and aims to (1) gain a better understanding of the geological formations, their associated variability, and their geomechanical properties, and to test new geophysical methods in urban areas; (2) build a 3D digital model coupling the 3D geological model of the Cenozoic geological formations, with existing underground public transport infrastructures. The merging of these two models will enable the creation of a digital twin prototype of the Parisian urban underground; (3) to place these underground spaces in the public imagination and in its perception of future developments, to analyse the environmental footprint of underground use in the urban development model in comparison with surface developments; and finally (4) to consider innovative methodologies for increasing circular economy applications, i.e. reclaiming excavated soil from underground works and using low enthalpy geothermal solutions. This research project, with a budget of 3 million euros and a duration of 7 years, started in 2023. It brings together eleven academic and institutional partners. This article describes the stakes, content and prospects of this project. --- This feasibility study investigates how underground heat production and seasonal thermal energy storage could be integrated into the planning of Zurich’s inner city. It treats subsurface energy infrastructure as a strategic urban resource that can support decarbonisation, use limited space efficiently, and strengthen social resilience. The study examines how existing underground spaces could be reused, or new facilities developed, to expand Zurich’s district heating and cooling network. Seasonal thermal energy storage is a particular focus because it can help balance heating and cooling demand across the year. Locating these systems underground could also preserve surface space for cultural, civic, and community uses. From this perspective, the study questions the planned conversion of the Selnau substation, currently a cultural and civic hub, into a surface energy plant. It explores alternatives that would retain public use of the site while moving energy production underground. Key planning scenarios include a centralised cavern system beneath Zurich’s University District and the adaptive reuse of existing underground infrastructure such as the decommissioned Letten Tunnel. These scenarios are evaluated in terms of spatial integration, compatibility with current and future land uses, and their contribution to long-term urban resilience and climate goals. The study concludes that underground energy infrastructure should be planned as part of broader urban strategies. Coordination among energy providers, planners, engineers, and local communities is essential to establish technical feasibility, spatial quality, and public acceptance. --- Reuse and Repurpose is a concept of growing importance towards keeping existing urban areas liveable and achieving sustainability. In existing cities there is a growing potential and intent to reuse and repurpose existing facilities; however considerations need to be given to inherent limitations of the existing facilities given their original use and purpose as well as their functional, safety and spatial features during their renewed use. Primary sources of underground spaces that might be candidates for reuse and repurpose are abandoned mines; old military, transportation and logistics facilities; previous parking and storage spaces, and unused civilian shelters. Cities that embarked on reviving these facilities, providing them with a new needed purpose, improved on resiliency of their communities.
13.10.2026
12:30 - 14:00
LUNCH BREAK
LUNCH BREAK
13.10.2026
13:10 - 13:50
e-poster station 1
Commented e-posters
COMMENTED E-POSTERS SESSION 4
13:10 - 13:18
Evaluation of the Reliability of Reference Geological Models: Comparison Between the R-Index Method and the Purely Geometric Approach Used in 3D Modelling Tools
Gianpino BIANCHI - Artelia Group (Choisy-le-Roi, France)
13:20 - 13:28
Bouygues and the Mechanised cross passages – a 10 year success story
Bruno COMBE - Tunnel Method Manager (VOISINS LE BRETONNEUX, France)
13:30 - 13:38
The Hermillon headrace tunnel or an example of risk management related to the presence of sulphatic rocks in EDF’s hydraulic fleet
Florian CARRAZ - Edf Cih (SAINT MARTIN LE VINOUX, France)
The evaluation of the reliability in reference geological models for underground projects is essential to evaluate possible construction and financial risks of the project. The reliability of the geological model must be evaluated throughout all the design stages to predict the expected ground behaviour and to provide an effective contribution for the definition of excavation methods, of ground support and to prevent the occurrence of unexpected behaviour during the excavation. Conversely, geological models inevitably involve a certain degree of uncertainty, and the achievement of a full reliable model is someway not possible due to, e.g. geological complexity of the project area, logistic difficulties and constraints related to project cost and schedule. The reliability is often based on qualitative evaluations without standardized criteria. In this respect, the R-Index method represents an example for a quantitative evaluation of the reliability of RGM (Bianchi et al. 2009). This is an empirical procedure that allows to consider the complexity of the ground conditions together with the quantity and quality of available geological investigations. Originally conceived for linear underground structures, the R-Index has been commonly applied on 2D geological profiles. However, the use of 3D geological models has undergone a continuous growth, demonstrating their usefulness in ever expanding geological contexts. This paper provides a first attempt to compare the R-Index method with 3D tools for evaluation of model uncertainties. It demonstrates that these tools can effectively contribute to the evaluation of the uncertainties of geological models. Nevertheless, some improvements are needed to increase the effectiveness of 3D tools by importing the R-Index principles into the 3D evaluation tools. --- The technology of mechanized cross passage (CP) construction involves using the pipe jacking methodology to create CPs between tunnels. Bouygues developed specific designs, methods, and equipment for this technology 10 years ago for the Tuen Mun Check Lap Kok (TMCLK) project in Hong Kong, aiming to protect workers from adverse ground conditions in 46 CPs. A few years later, the neighbouring HKT2 Trunk Road project decided to adopt the same approach, while making some adjustments based on lessons learned from TMCLK. Recently, Bouygues led joint ventures have been awarded the contracts to execute two major road tunnel projects: the Lower Thames Crossing (LTC) in the UK and Torrens to Darlington (T2D) in Australia, where the mechanized CPs solution will be applied. Through its innovation and engineering, Bouygues is tackling the new challenges of these two projects, from complex spoil management requirements to the use of an EPB machine on T2D and implementing tunnel steel segments as temporary and permanent support for openings.. On LTC the team are designing a bespoke tympanum, and will be launching from a recessed platform within the main gallery to align the final CP level with the planned road level. The current article presents an overview of the various challenges and design, methods, equipment, and performance achievements delivered across the four projects listed above. --- The occurrence of significant damages to tunnels passing through sulfatic rock led EDF to re-examine its knowledge and understanding of the mechanisms of change in this type of geological environment. Thanks to appropriate monitoring, in 2022, important leakages were detected early in the Hermillon power plant’s intake tunnel (5,200 meters long, circular section with a diameter of 5.3 meters, an essential link in hydroelectric production in Savoie). Emergency work was carried out in the fall of 2022 to restore the watertightness of the structure, while a long-term reinforcement solution was studied. This study phase, completed in the spring of 2024, resulted in the award of a works contract to the temporary consortium "Bouygues TP RG / Solétanche Bachy France." The work was divided into two campaigns due to seasonal constraints related to hydraulicity and electricity consumption. The first campaign (2024) consisted of filling the cavities in the extrados and consolidating the ground by appropriate grouting. The second phase (initially planned for 2025 and postponed to 2027) will consist of creating a new 160-meter-long reinforced concrete lining associated to a PVC geomembrane waterproofing system installed on the existing lining. A custom-made formwork tool was designed to accommodate the access constraints within the gallery. Enhanced monitoring by EDF's operations and engineering teams during the filling of the gallery and in the months that followed confirmed the effectiveness of the initial work undertaken.
13.10.2026
13:10 - 13:50
e-poster station 2
Commented e-posters
COMMENTED E-POSTERS SESSION 4
13:10 - 13:18
Probabilistic risk assessment of rockburst phenomenon during deep tunnel design: a case study of the Mont-Cenis base tunnel
Baptiste FENNETEAU (Aix les bains, France)
13:20 - 13:28
SIKAPROOF®-110 revolutionizes waterproofing tunnel
Pascal FRISON (Le Bourget, France)
This paper aims to present a methodology for a probabilistic rockburst risk assessment with an explicit consideration of geological and geotechnical uncertainties. The methodology is based on the approach proposed by Diederichs in 2018 for the early assessment of dynamic rupture hazards, which calculates the Burst Hazard Potential (BHP) and assigns corresponding hazard classes. As Diederichs’s method is based on a deterministic approach, it has been improved to allow the introduction and propagation of uncertainties through Monte Carlo simulations. The probability of being in each of the hazard classes can then be obtained for the whole tunnel sections, as well as some information regarding the geological and geotechnical conditions associated with these hazard classes. Explicitly accounting for these uncertainties allows better risk management and adaptability during construction, as the maximal possible rockburst intensity is directly linked to the geological and geotechnical conditions. The proposed approach has been applied to a 15 km section of the deepest part of the Mont-Cenis based tunnel, where major uncertainties exist regarding the rock properties and the in-situ stress state. The results indicate that two zones are prone to minor to moderate rockburst. The first zone was not initially suspected to be at risk, but the probabilistic analysis suggests that the risk of rockburst cannot be excluded mostly due to the large uncertainties regarding the in-situ stress state. The second zone was already considered at risk, and the obtained results provide a more refined interpretation of risk based on the expected values and variations of intact rock and rock mass properties. --- Sika has developed a new generation of tunnel waterproofing using FPO (flexible polyolefin) membranes, fully and doubling bonded to the concrete. This waterproofing concept combines well established systems over the last 50 years with optimized application. The technology using fully bonded membranes in tunnels was first developed in South Korea and successfully applied in many projects. This results in a material reduction of 40% and a carbon footprint (CO2) of 20% compared to a PVC DEG (Waterproofing Geomembrane Device) of 2 mm, as well as increased reliability compared to the current system. The application is simplified, reducing work steps, such as compartmentalization by waterbars and injection hoses, while using heat welding for the assemblies The new generation tunnel waterproofing fits the drained tunnels as well as the pressurized systems.
13.10.2026
13:10 - 13:50
e-poster station 3
Commented e-posters
COMMENTED E-POSTERS SESSION 4
13:10 - 13:18
Parametric approach and predictive modelling of Life Cycle Assessment applied to Tunnel Boring Machine tunnelling
Lucille BAUCAL—POYAC (Bron, France)
13:20 - 13:28
Influence of extraction exhaust vents position on smoke removal efficiency in underground, mechanically ventilated areas: a numerical study
Poeiti DORADO (Choisy-le-Roi, France)
13:30 - 13:38
Sustainability – New Life Cycle for TBMs and used products
Karin BÄPPLER (Schwanau, Germany)
13:40 - 13:48
Constraints, design, and construction method of a 1.5km long cut‑and‑cover tunnel on Line 18, Paris, France – Feedback from Lot 3C
Aymene LAIREDJ (Paris, France)
Life Cycle Assessment (LCA) is a multicriteria method used to assess the potential environmental impacts throughout the life cycle of a system. This methodology has been applied to TBM tunnelling. Existing studies usually focus on a single Tunnel Boring Machine (TBM) tunnelling case, which restricts the generalisation of results to other tunnel designs. Moreover, system boundaries most often include the construction materials for segments and backfilling grout as well as TBM electricity consumption. The manufacturing of the TBM itself, although needed to be integrated, is rarely considered. This study presents a parametric approach to generalise the LCA of TBM tunnelling. It is based on a database compiling the technical characteristics of 525 TBM tunnelling projects. The developed parametric LCA inventory relies on 47 parameters covering tunnel geometry, TBM technical and driving characteristics, geology and transport distances. Two predictive models were developed to estimate the global warming potential per meter of tunnel as a function of tunnel length and TBM mass. Linear regression offers a simplified approach, while the use of XGBoost – a machine learning algorithm – significantly improves prediction accuracy. This study paves the way for simplified environmental impact assessment tools aimed at sustainable tunnel design. --- This numerical study examines the influence of mechanical extraction vent position on smoke removal efficiency in confined underground spaces, such as metro platforms. Using FDS software, three vent configurations were analysed on a simplified representative geometry: a vertical position opposite the air inlet, a horizontal ceiling position opposite the air inlet, and a horizontal position near the air inlet. For each configuration, the influence of smoke curtain height and extraction flow rate was investigated for a 1 MW fire source. Simulations revealed the existence of a critical phenomenon for evacuee safety, termed partial confinement, characterised by parasitic recirculation of smoke initially exiting the fire compartment and subsequently reinjected inside. Comparison of different evaluation methods for smoke control system efficiency demonstrates that the global efficiency coefficient based on energy balance proves insufficient to detect transitions between confinement regimes. Velocity analysis at openings proves more sensitive for identifying the flow rate required for total smoke confinement. These results emphasise the importance of an approach coupling energy balances and local flow analysis for optimal smoke control system design. Among the configurations studied, the vertical position opposite the air inlet exhibits the best performance, requiring lower extraction flow rates to achieve total smoke confinement. --- According to United Nations projections there will be nine billion people living on Earth in 2050. This is closely linked with consumer market growth, increase in consumption of raw materials and also increasing environmental pollution. Thus, it is apparent that global industry and business activities must assume responsibility and find new paths. In the tunnel industry this has started already in designs for upgrading or constructing new infrastructure systems. Our common goal should be to bring re-use and eco-efficiency to our industry to minimize our carbon footprint by reducing the demand for new raw materials. This paper describes the reuse of valuable TBM components in order to save valuable resources in the form of material and energy whilst giving individual TBM components, assemblies or complete TBMs a completely new life cycle. --- As part of the Grand Paris Express Line 18 project – lot 3C (Western sector), upstream of the future Saint-Quentin Est (SQE) station in Guyancourt, the construction of a 1.5 km cut-and-cover trench (TC) is planned. The TC structure, designed as a reinforced concrete frame, has a usable width of 8.10 m in straight alignment. It is buried at an average depth of 10.5 m. Its alignment crosses the Golf National and passes under Avenue de l’Europe in Guyancourt. Two ancillary structures, spaced about 600 m apart, are connected to the TC. Construction of the cut-and-cover trench requires large-scale earthworks with slopes up to 15 m high. In certain areas, to overcome constraints related to utility networks or limited space, temporary retaining structures are implemented. Two techniques are used: a nailed wall (H ≈ 7 m) over approximately 700 m and a braced Berlin-type wall (H ≈ 10 m) over 2 × 100 m. This configuration meets technical requirements, ensures site safety, and supports urban integration. The geological profile extends from the Plateau loams down to the Fontainebleau Sands at a depth of 15 m, with the structure mainly located within the intermediate formations of Meulière clays. Piezometric levels and foundation depth led to the design of reinforced concrete structures to ensure stability and counteract hydrostatic uplift. Civil works for the TC over such a long section required an on-site production chain operating in a quasi-industrial mode, achieving a rate of up to 60 m of cut-and-cover trench per week.
13.10.2026
14:00 - 15:30
Room 0.4
Congress Conference
B. Technological and digital innovations in underground work
EXPERIMENTS AND DIGITAL MODELLING (2)
Chairmen : Emilio ABI AAD (France), Denis BRANQUE (Vaulx En Velin, France)
14:00-14:10
Introduction
14:10-14:30
General instability in deep underground structures - Considerations and assessment approaches
François LAIGLE (Lyon, France)
14:30-14:50
Integrated 3D SSI modelling - Agnettes station, Line 15 West North, Grand Paris Express
Xuan-Phu NGUYEN (Lyon, France)
14:50-15:10
Shotcrete Support Systems: Key Lessons from 20 Years of Application and Monitoring at Andra’s Underground Research Laboratory
Jad ZGHONDI (Bure, France)
15:10-15:30
From Field to Model: Optimized Design of Support and Lining Systems in Complex Geological Settings – The Lyon–Turin Case Study
Thomas ROSSI (Lyon, France)
Underground structures are generally designed and verified in relation to two categories of limit states: ultimate limit states (ULS) and serviceability limit states (SLS). Verification against SLS is particularly relevant for shallow structures, where excavation may affect neighbouring structures. For ULS, verifications focus on structural (STR) and geotechnical (GEO) states. STR states involve verifying that the lining is not overloaded, while GEO states involve protecting against ground failure. Some AFTES recommendations describe the approach for justifying concrete lining and the consistency of this approach with the Eurocodes. This method is suitable for structures whose stability relies on rigid support or lining. In the case of deep tunnels, stability often depends more on the rock mass itself. Assessing the safety margin therefore becomes more complex, requiring a good understanding of the behaviour of the ground and geotechnical uncertainties. There are three main situations: • The instability mechanism is identifiable, and this allows justification by limit equilibrium. • The mechanism is uncertain, but the geotechnical model is sufficiently robust for numerical simulation, using a c-φ reduction approach and deformation limitation. • Neither the mechanism nor the parameters are understood justification is then based on an observational approach and real-time monitoring. The article develops some thoughts on these approaches, emphasising the need to propose a method for assessing the safety margin when stability depends mainly on the contribution of the rock mass. --- The Agnettes station (AGN) on section 2 of the Grand Paris Express Line 15 West (L15) is located adjacent to the eponymous RATP Line 13 (L13) station. The project involves a main station box constructed with diaphragm walls, approximately 35 m deep, and an interconnection corridor, constructed with secant piles, providing connectivity with L13. The L15 tunnel runs a few metres below the toe of L13 diaphragm walls, while the closest point of the station endwall is about 13 m away. The vulnerability study for L13 and other neighbouring structures with respect to the L15 construction was carried out using a global 3D ISS model, incorporating L15 station and tunnel as well as the L13 structure. Each diaphragm wall panel, slab plot and each waterproof joint of the existing L13 cut-and-cover trench and station were explicitly represented. The main structural elements of the L15 station and tunnel were also modelled, simulating all construction phases. The article will detail the modelling methodology, with particular attention to the joint modelling of the station, tunnel and neighbouring structures within a single model, enabling accurate consideration of the cumulative effects of all planned works on existing structures. The results obtained will be analysed, among others, in terms of deformation and L13 waterproof joint relative displacements. --- Various types of primary linings have been constructed and monitored at Andra’s Underground Research Laboratory (URL CMHM), operated by the French National Agency for Radioactive Waste Management (Andra). These structures form part of a scientific and technological demonstration programme, which aims to strengthen the knowledge required for the design and construction of the future facilities of the Cigéo project. Such design is particularly important in view of the operational lifetime and the time-dependent behaviour of the host rock (Callovo-Oxfordian claystone, at a depth of approximately 500 m). This paper focuses on selected elements of the knowledge gained regarding the behaviour of shotcrete primary linings. At the material scale, several characterisation campaigns were carried out, based on specimens taken from dedicated test panels, cores extracted from in situ support systems or multilayer wall panels. In particular, the paper presents shear and permeability tests performed at the interface between two layers of shotcrete applied with a 48 h time interval and under various confinement levels, showing good mechanical bonding at the interface. At the support system scale, selected results related to the construction procedures, instrumentation, adequacy of integrating compressible layers and support loading are discussed. The paper highlights the importance of proper shotcrete application and modelling, as well as its contribution to the structural design of the final structure. --- The Mont-Cenis base tunnel, a key component of the Lyon–Turin railway link, crosses highly tectonised formations, including the Houiller (coal bearing) facies near the Briançonnais Front thrust fault. These zones exhibit significant squeezing behaviour, with diametral convergences up to 2 meters and convergence rates reaching 50 mm/day under overburden exceeding 600 meters. Based on over a decade of monitoring data from the Saint-Martin-la-Porte access tunnel, a robust geomechanical model was developed to calibrate both instantaneous and time-dependent rock mass behaviour. The S2IP design consortium adopted an innovative approach that integrates time-dependent effects at each excavation step, using a viscoplastic Norton law and a cohesion degradation model. This methodology was applied to the R23 cross-passage, located in the Moderate-deformability Houiller facies, and modeled in 3D using FLAC3D. The simulation enabled assessment of excavation phasing, support performance, and long-term lining loads over a 120-year horizon. Results were validated against analytical convergence-confinement methods, confirming stress levels and guiding design adjustments. The proposed approach improves understanding of rock mass/support/lining interaction and supports optimized design in complex geological settings.
13.10.2026
14:00 - 15:30
Room 0.5
Congress Conference
C. Opportunities offered by the city and underground infrastructures
COMPLEX URBAN PLANNING
Chairmen : Sam HUCKLE (Amstelveen, The Netherlands), Reza TAHERZADEH (Chatenay Malabry, France)
14:00-14:10
Introduction
14:10-14:30
Kwu Tung station on East Rail Line in Hong-Kong: Build a new underground station on top of a running Railway line
Ludovic JEANNE - Contractor Representative (Hong-kong, Hong kong)
14:30-14:50
Engineering a new underground infrastructure in Marseille: Design of a New Tunnel and Station for the Future Côte d’Azur Line
Francis LANQUETTE - Setec Tpi (Paris, France)
14:50-15:10
Service shafts of Grand Paris Express Line 18-3A: Design, optimization and construction methods of the structures
Clement GAUDRY – Arcadis (Paris, France)
15:10-15:30
The new underground Rail link between the central station and Geneva Airport, Switzerland
Brice GAUDIN (Nyon, Switzerland), Oumaima SEDRATI (Nyon, Switzerland)
Upon completion, Kwu Tung Station (KTU) on the East Rail Line (EAL) will become the MTR Corporation’s 100th station, marking a major milestone in Hong Kong’s rail development. As the first station built directly above an operational tunnel 20 meters underground, KTU is a landmark engineering achievement. Originally planned over thirty years ago, the station is now a key part of the Northern Metropolis, serving the future Kwu Tung North New Development Area (NDA), which will accommodate 130,000 residents. KTU’s underground location enables efficient and sustainable transit, reducing travel time between Kwu Tung and Sheung Shui from 15 minutes to just 3 minutes when it opens in 2027. The station will also be an interchange and terminus for the future Northern Link (NOL), a 10.7 km underground railway with five new stations, scheduled for completion by 2034. The project reflects long-term urban planning and is being delivered in three phases: the Kwu Tung tunnel was completed in 2006; the EAL station will open in 2027; and the NOL section is set for 2034. Early works in 2002 included provisions such as an underslab drainage system and reserved openings, facilitating efficient future construction. KTU stands out as a large-scale project entirely within a brownfield environment, requiring precise engineering to avoid affecting existing rail operations. Unlike conventional methods, the tunnel box uses a raft foundation, subject to 200 kPa underslab buoyancy pressure due to groundwater, demanding constant monitoring and adjustment. This paper describes the solutions developed to overcome these engineering and logistical challenges. --- The Underground Crossing of Marseille (TSM) is a strategic component of the phase 2 of the New Provence Côte d’Azur Line (LNPCA), managed by SNCF Réseau. Currently in the concept design stage, the project proposes the construction of 8 km long twin bore tunnel beneath the city of Marseille. This tunnel is connected to the existing railway lines by cut-and-cover access structures, built in direct interface with the existing tracks. The tunnel comprises two tubes, each with an internal diameter of 7.80 meters, built using a pressurized tunnel boring machine. The alignment crosses the Oligocene geological formation in the Marseille area with a maximum cover of 66 meters beneath a densely built and sensitive area. The tunnel serves an underground high-speed train station, connected to the historic train station, the Saint-Charles metro station, and the planned extension of the T2 tramway. This station, measuring 406 meters long by 46 meters wide, can accommodate up to four double high-speed trains simultaneously on two central platforms. This infrastructure provides significant volumes on the upper levels, facilitating the development of underground parking. The station is managed by SNCF Réseau and SNCF Gares et Connexions. Junction tunnels at the ends of the station connect the four platform tracks to the two tunnel tracks. These four junction tunnels, up to 120 meters long, are constructed using traditional methods under low coverage and existing buildings. Their sections vary between 100 and 200 m² to adapt to the loading gauge and allow the tunnel boring machines to pass through to the station. The project includes significant fire safety challenges. --- Line 18 of the Grand Paris Express will connect Orly Airport to Versailles Chantiers by 2030. The infrastructure works on lot 3A was awarded to the Spie Batignolles - Ferrovial consortium and began in 2023. This lot is notable for its sparsely urbanized context, with the future 6.7 km line stretching across the municipalities of Guyancourt and Versailles. This article presents the design approach, the consideration of local constraints, and the progress of the service shafts representative of this lot. Some of the guidelines are based directly on the local context, but also on the feedback from lot 1, while allowing for variations in the construction methods used by the contractor. Most of the ancillary structures have an emerging building that integrates the technical premises due to the availability of land, allowing the dimensions of the shafts to be optimized. The methods used to construct the shafts and the connection gallery to the main TBM tunnel have been adapted to the geological and hydrogeotechnical context, as well as to the depth (in relation to the tunnel layout), enabling feedback on the various methods. Groundwater management was one of the major challenges and led to specific considerations that will be detailed in the article. --- The Léman 2030 project is a major initiative aimed at modernizing and increasing the capacity of the railway network between Lausanne and Geneva, in response to the significant growth in passenger traffic in the Lake Geneva region. A central component of this programme is the expansion of the Geneva-Cornavin station rail hub, which is facing increasing saturation. This article outlines the technical aspects of the geotechnical design and the tunnel of the “Airport Sector”. This sub‑project consists of creating a new 3‑km underground link between Geneva-Cornavin station and the existing surface tracks leading to the airport. To excavate the double‑track tunnel, a slurry pressure‑balance tunnel boring machine (TBM) with a diameter of 12.30 metres—unprecedented in the Geneva region—is planned for use in soft soils that are partially saturated with water. In order to minimize the impact on urban traffic, compensate for the lack of available installation space, and optimize material management, an aerial conveyor system is planned to transport the excavated materials from the TBM logistics area to a remote processing site located 3 km from the urban work zone, and to organize the reuse of part of the excavated material. From there, a dedicated rail platform is envisaged to evacuate the non‑reusable materials by train to disposal sites, thereby drastically reducing the number of trucks on the road and the associated nuisances. In terms of interfaces, the TBM launch and reception zones are located in dense urban areas where several infrastructure projects are underway or planned. Coordinating these projects, combined with works carried out adjacent to an operating railway line, represents a major challenge.
13.10.2026
15:00 - 15:30
Room 2.3
Lecture
A. Sustainable solutions to environmental challenges
LECTURE - VINCI
15:00 - 15:30
Facing the Unexpected: Lessons Learned from VINCI Construction Grands Projets
François RENAULT (Nanterre, France)
13.10.2026
15:30 - 16:30
COFFEE BREAK
COFFEE BREAK
13.10.2026
15:40 - 16:20
e-poster station 1
Commented e-posters
COMMENTED E-POSTERS SESSION 5
15:40 - 15:48
Urban railway transportation tunnels: Twin tube vs. Single Tube
Nima NOROOZIPOUR (Choisy-le-Roi, France)
15:50 - 15:58
Geological and Hydrogeological Modelling of the TEOL Tunnel (Lyon, France): Methodology and Alignment with Engineering Practice and IAEG C25 Guidelines
Johan KASPERSKI (Bron, France)
16:00 - 16:08
Feedback on the construction of the PTR adit: ground improvement using Biocalcis® and tunnel opening on lot 4 of the Toulouse Metro Line C project
Annette ESNAULT FILET (Rueil Malmaison, France)
16:10 - 16:18
Temporary Retention with Permanent Impact: GFRP Ground Anchors at IGNOU Metro Station New Delhi India
Kunal SHANKER (New DELHI, India)
In a context where sustainability and resilience drive infrastructure development, choosing between single-tube or twin-tube tunnels for urban underground rail systems is a strategic decision. This choice affects design, financing, construction, operation, and maintenance, while meeting environmental, social, and economic requirements. To support this complex decision, the article proposes a multi-criteria analysis framework that incorporates technical and contextual factors as well as lessons learned from past projects. Solutions are assessed based on key factors—safety, urban integration, performance, and environmental impact—weighted according to local priorities. The goal is to improve transparency and decision quality, reduce impacts, optimize long-term costs, and ensure infrastructure adaptability for the future --- The West Lyon Tramway Express (TEOL) project, led by SYTRAL Mobilités, includes a nearly 3 km tunnel designed to overcome the 100‑metre elevation difference between the right bank of the Saône River to the east and the plateau of Lyon’s 5th district to the west. Conceptual design studies (CD) were completed in 2024, and the tunnel design has now entered the basic design (BD) phase. The eastern portal lies on the steep slope of the “Balmes lyonnaises,” notable for its heterogeneous glacial superficial formations overlying older Miocene and Pliocene deposits. With limited site investigations, understanding the structure of these terrains remains highly uncertain. The associated hydrogeological system is also complex, with multiple springs and mineral‑rich waters. In addition, the local history of slope instabilities in Lyon increases the challenges for geological and hydrogeological modelling. This paper analyses the methodology used to develop geological and hydrogeological models for the project at two study levels (CD and BD) and compares it with the state‑of‑the‑art approach presented by the International Association for Engineering Geology (IAEG) in its C25 guideline, “Engineering geological models.” Teams were reorganised and new investigations were carried out between these two studies phases, allowing significant improvements to the models despite remaining uncertainties. Comparison with the C25 highlights the importance of having engineering geologist experts in the team, and the need to produce graphical documents to clarify the models and their uncertainties. --- The adit presented in this paper provides the connection between the Terrasse shaft (PTR) and the tunnel of the future Line C of the Toulouse metro network. The adit has a length of 6 m and a maximum excavated section area of 30 m². Its future function is to serve as emergency access to the tunnel. Excavation is to be conducted in Toulouse molasse under a cover of 33 m and a hydrostatic head of 12 m. The presence of a thick layer of sandy molasse at the crown of the adit excavation, identified during the TBM excavation, required the implementation of specific risk mitigation measures. These included groundwater drainage works and ground improvement by Biocalcis® injection to address the risks of instability during excavation. This paper describes the measures implemented to ensure the safe excavation of the adit. It also presents the subsequent works, in particular the arrangements adopted to avoid the use of temporary tunnel support frames during tunnel opening, made possible thanks to monitoring data and 3D tunnel deformation scans. --- IGNOU Metro Station one of the deepest stations in metro infrastructure in India presented formidable geotechnical challenges in a weathered quartzite formation with micaceous schist. The initial support system, comprising rock bolts and shotcrete, was redesigned with maximum of six-level pre-stressed ground anchor system along with two layers of strut walers keeping both safety and sustainability as priorities. Advanced finite element modelling was utilized to arrive at the anchor forces, wall stability, and global factor of safety. The adoption of Glass Fiber Reinforced Polymer (GFRP) anchors, selected for their lightweight, corrosion-resistant, and non-toxic nature are more environmentally sustainable and can be safely left in situ after fulfilling their temporary function without impacting long term soil quality and reducing carbon footprint. A comprehensive Instrumentation and Monitoring scheme was deployed to measure pre-stressing forces and the load behavior during excavation. While GFRP is conventionally used in sacrificial roles, this project marks a significant departure by using GFRP as a structural and long-term solution in an actively loaded retention system. This paper outlines how GFRP as an anchoring solution provided a high-performance and environmentally conscious response to heterogeneous and challenging geology offering a blueprint for projects aiming to balance structural resilience with sustainable construction practices. Keywords: Sustainable GFRP Anchors, Deep Excavation, Urban Infrastructure System, Instrumentation and Monitoring
13.10.2026
15:40 - 16:20
e-poster station 2
Commented e-posters
COMMENTED E-POSTERS SESSION 5
15:40 - 15:48
Asset Management at SNCF Réseau: the specific case of old railway tunnels
Christine THUAUD (LA PLAINE SAINT DENIS, France)
15:50 - 15:58
Towards responsible innovation in the use of cements for bolting: balancing sustainability, environmental impact and production efficiency
Coline LE SAËC (Stockholm, Sweden)
16:00 - 16:08
Sustainable Tunneling, a carbon footprint evaluation tool for tunnels
Romain PROST (EPAGNY-METZ-TESSY, France)
The infrastructure of the French National Rail Network (RFN) is an exceptional asset, both in terms of the large number of railway assets it includes and the diversity of asset types that make up the system (e.g., engineering structures, earthworks and hydraulic works, tracks, Signalling systems, Overhead line equipment). Some assets are tangible, while others are intangible. The network’s highly varied geographical context is also a key factor in asset management. Service lives differ widely across asset categories: the oldest tunnel in France is nearly 200 years old and remains in good condition, whereas some assets have service lives of only a few years. In recent years, SNCF Réseau has implemented a structured asset management approach. This has required a paradigm shift from historically organised maintenance towards asset management based on a differentiated strategic vision, ensuring the long-term sustainability of the RFN as a public asset. Managing assets across their entire life cycle, while integrating both internal railway-system conditions and external contextual factors, enables the company to address today’s and tomorrow’s industrial, societal, and environmental challenges. This strategy supports improves knowledge of assets (inventory consistency, condition, and use), and rationalises decision-making by seeking an appropriate balance between investment costs, maintenance expenditures, and the network’s commercial performance with a high level of safety. Given their technical specifications and the age of much of the portfolio, railway tunnels have been among the first asset classes to apply asset management principles, supported by the development of a dedicated structured methodology. --- In bolting, a cement grout is injected into the borehole, where it meets the rock, and this grout must meet certain requirements. One of these requirements is the water/cement ratio. A low ratio produces a dense grout with low porosity and excellent mechanical strength. This verified data, together with a pull-out test, ensures the quality of the bolt installation. However, the lower the W/C ratio, the thicker and more difficult to inject the mixture becomes, which increases the risk of blockages in the pumps. At the same time, in Sweden, the cement industry is moving towards reducing its environmental impact. There is therefore a shift from CEM I to CEM II cement. CEM I is composed of more than 95% clinker, the production of which accounts for the largest share of CO₂ emissions. Conversely, CEM II replaces part of the clinker with additives in order to reduce greenhouse gas emissions by up to 30%. In this context, we are studying the addition of superplasticizer to improve the fluidity of low VCT grout. Finally, technical innovation is hampered by traditional methods that work. However, in a world in transition, it is becoming necessary to rethink certain bolting practices, including the composition of cement. --- The growing focus on infrastructure sustainability requires accurate assessment of the carbon footprint of different construction methods. To meet this need, the Sustainable Tunneling (SusT) tool has been developed to assess the carbon impact of tunneling works, taking into account the excavation method, thereby facilitating decision-making in the early stages of the project. SusT is based on realistic assumptions drawn from feedback on numerous projects, mainly in France, and on expert consultations. The technical data comes mainly from AFTES data sheets and international projects. Unlike existing solutions, SusT incorporates a comprehensive analysis in accordance with standard EN 17472, a specific database of emission factors (A0-A3), and a detailed LCA covering the entire life cycle of equipment and materials, including the specific characteristics of tunnel boring machines and conventional methods. We will present the methodology and assumptions adopted for the single-criterion analysis, then the influence of parameters such as location and geology. Finally, we will propose ways to reduce the carbon footprint of tunnel construction and future developments.
13.10.2026
15:40 - 16:20
e-poster station 3
Commented e-posters
COMMENTED E-POSTERS SESSION 5
15:40 - 15:48
Design of a small underground gallery as part of the reconstruction of the RTE substation in Arly
Amélie LEBOURG (EPAGNY-METZ-TESSY, France)
15:50 - 15:58
TBM break-in and break-out on lot 4 of the Toulouse metro line C project
Philippe CHOUC (Guyancourt, France)
16:00 - 16:08
Minimizing construction risk through parametric tunnel
Mikhail SEMENENKO (Gentilly, France)
16:10 - 16:18
Reducing the carbon footprint of underground works: feedback from a rehabilitation project on a walk-through sewer structure using SEVE TP
Julien LANDAUD (Pantin, France)
As part of RTE’s equipment replacement policies, the Arly substation, located in the municipality of Ugine in Savoie, is undergoing a complete reconstruction on a separate plot of land. The current substation is set back from the Arly hydroelectric power plant operated by EDF Hydro Alpes on the slopes of the Aravis massif. The new substation is being built on a plot acquired by RTE on the other side of the power plant, about 200 meters away. The current substation’s connections, both from the power plant and via overhead-underground pylons, must be linked to the new Metal-Clad Substation building (PSEM). To achieve this, following preliminary studies, RTE has opted to create a small-section gallery (maximum 30 m²), excavated using traditional methods, with a length of approximately 300 meters. The gallery’s route interfaces with sensitive neighboring structures such as the hydroelectric power plant and its penstock, the passage beneath the departmental road providing access to the Arly gorges, and RTE’s operational facilities. The project is entirely excavated in recent detrital soils (alluvium and moraine), Jurassic schistose limestone, and Triassic cargneules. At the interface between the latter two formations, a fault and a crushed zone several meters long were discovered during the project phase, representing one of the main identified risks of the project. After presenting the project and its context, the article focuses on the design choices made by EGIS, the project manager, in response to the major challenges of the project. Finally, the article will address the contractual aspects specific to the project. --- From the tender stage, the Horizon joint-venture proposed a technical optimization for the TBM break in and break out at the Ormeau, Limayrac, and Jean-Rieux stations. This optimization was accepted, subject to providing supporting documentation during the detailed design phase. The construction sequencing for lot 4 involves bringing the TBM into the station after full excavation and completion of the base slab. Technical optimization consists of: For “break-in” (from station to ground), replacing the use of a bell with a steel seal and soil treatment by desaturating the molasse using subhorizontal drains. For ‘break out’ (from the ground to station), carrying out an atmospheric breakthrough after previously desaturating the molasse with subhorizontal drains. In this article, the design section will present the geotechnical investigations and the supporting calculations using a Plaxis 3D model. Finally, the monitoring of instrumentation covering the excavation phases at both the entry and exit points will be described, confirming the validity of this optimization. --- This article presents a parametric workflow used on a large twin-tube road tunnel project in the United Kingdom. The project required frequent design updates, strict geometric tolerances and close coordination between several disciplines working in a confined underground space. The methodology is built around two practical components. First, the tunnel is generated automatically with Dynamo, using the alignment and a small set of inputs stored in Excel. This allows the entire model to be updated within minutes whenever the design evolves. Second, tolerances between the two tubes are analysed with Grasshopper through Rhino.Inside.Revit, where different positional shifts are simulated and each scenario is checked automatically for constructability and clearance compliance. All resulting models are exported to IFC, enabling teams and external partners to review and use the geometry in their own environments. The workflow proved efficient and reliable, helping to avoid late clashes and reducing the overall design risk. The experience presented here shows how a straightforward parametric approach can support consistent decision-making throughout the development of a complex tunnel project. --- The reduction of greenhouse gas emissions has become a central objective in the design of underground infrastructure projects. This study presents feedback from the rehabilitation of concrete accessible (walkable) sewer structures, combining injection grouting and structural lining techniques, as well as the replacement of house connections. The carbon footprint assessment was carried out using the SEVE TP software, developed by the French National Federation of Public Works. A dedicated database was implemented in the tool to reflect the specific materials, processes and equipment used for underground sewer works.Three design variants were modelled: a reference solution based on conventional trenchless rehabilitation methods; an improved solution incorporating the use of biofuels, a reduced thickness of sprayed concrete with carbon mesh reinforcement, and a direct connection to the drinking water network; and an optimal solution which, in addition, includes the use of electric equipment supplied from the grid. The results show a 34% reduction in emissions for the improved variant and a 55% reduction for the optimal variant.This approach highlights the value of integrating a carbon assessment from the design stage in order to steer technical choices towards more sustainable solutions, without compromising the structural performance of the rehabilitated assets.
13.10.2026
16:30 - 18:00
Room 0.4
Congress Conference
D. Worker health and safety in underground environments
FIRE SAFETY MANAGEMENT
Chairmen : Didier DE BRUYN (Brussels, Belgium), Emmanuel HUMBERT (Chambery, France)
16:30-16:40
Introduction
16:40-17:00
Fire safety in tunnels during construction phase: contributions from R&D
Come LECLERC - Lemta, Université De Lorraine, Cnrs (Saint-Denis, France)
17:00-17:20
Ventilation of construction sites during Grand Paris Express system works
Luc FOURNIER - Egis (Paris, France)
17:20-17:40
Acculturation of emergency services to underground interventions during construction work on Line C of the Toulouse metropolitan subway system
Bastien ESCANDE - Tisséo Ingénierie (Toulouse cedex 6, France)
17:40-18:00
Study on the influence of the water mist system on the dust distribution characteristics during tunnel excavation
Yunxiao XIN (Xi'an, China)
During the construction of tunnels and underground networks, the construction phase poses specific fire safety issues. We have carried out experimental model and numerical studies using the Fire Dynamics Simulator to answer questions raised by the Société des Grands Projets, particularly regarding: the potential heat release of the fire, smoke management, and the possibility of confining the fire zone using water curtain-type devices. The absence of operational ventilation during the construction phase and the complexity of the connections between galleries and structures with access to the outside air influence the oxygenation of the fire and the stratification of smoke. In the event of a fire in a gallery during the excavation phase, the smoke produced spreads to the upper part of the gallery in a stratified profile. A return layer remains in all simulated cases in the lower part downstream of the fire, supplying it with oxygen, even if only partially. This smoke-free layer forms naturally despite the absence of operational ventilation due to the buoyancy forces of the smoke, which is hotter than the incoming air. This air layer, with a thickness of around 40 to 50% of the total height of the gallery, can allow access for rescue and firefighting services in the event of a fire. However, its thickness is reduced in the case of sloping galleries. An external wind above the access shaft is also likely to impact this smoke stratification, or even destroy it completely by disrupting the plume of smoke pouring into the access shaft. Similarly, the use of a water curtain to confine the fire zone is counterproductive: it causes a loss of stratification without blocking the smoke produced or the layer of air returning to the fire zone. The smoke and incoming air are simply mixed and diluted by the spray. --- As part of the work on lines 15 South and 16-17 of the Grand Paris Express, the large scale of the project and the presence of interconnected tunnels, as well as the multitude of stakeholders involved, required a holistic approach coupled with a high degree of adaptability for the temporary ventilation system. An audit of the temporary ventilation systems was commissioned by the project owner. Following this, the owner appointed a design consultant to carry out an interdisciplinary study for lines 15 South and 16-17. The methodology implemented was based on an assessment of the current situation, where possible, followed by the definition of a general principle. This was then combined with a verification phase through the sizing calculations and digital simulation of a likely specific case. The proposed methodology was tested theoretically through anticipated development phasing. Finally, this methodology was implemented with the involvement of the project owner, including: -the identification of measures and technical means compatible with the constraints of the work, -an organizational approach that was more or less collaborative depending on the contractual and organizational context of the project. --- Metropolitan Line C of Toulouse is 27 km-lined-major project of construction whose 21 km are underground. The tunnelling phases raise significant safety issues for workers, particularly due to the presence of blind tunnels extending up to 1,800 m length. Thanks to first meetings between the project owner, construction companies and emergency services, they highlighted the necessity of clarification of the tunneling methods and contraints linked to thes activities in order to adapt the emergency responses. Indeed, these gaps represented a risk for the management of emergency situations in underground environments. This paper presents feedback from an approach initiated well before the start of construction works, based on close cooperation between Tisséo Ingénierie and the Haute-Garonne Fire and Rescue Department. Thanks to this method, project specific accident scnarios could have been defined and intervention procedures could be adapted. They have also been able to acquire dedicated equipment and implement an extensive awareness and training program. Beyond information sharing, this process resulted in genuine interdisciplinary acculturation between project stakeholders and emergency services, validated through both theoretical and operational exercises. The lessons learned highlight the importance of integrating such initiatives at an early stage while anticipating their impact on construction organisation and productivity. --- The dust generated during tunnel excavation can severely pollute the construction environment inside the tunnel, thereby affecting the health of workers. The dust distribution in the tunnel face area is relatively concentrated and difficult to eliminate. This paper takes the Fangyushan tunnel as a case study. Physical model tests were established to examine the influence of different parameters on dust reduction efficiency. The results show that the dust concentration near the tunnel face is highest during the blasting stage, and the workers' operation area highly overlaps with the high-concentration dust distribution area in space and time. The air humidity difference inside the tunnel has a significant impact on the distribution of dust concentration. When the pressure at the nozzle is constant, the dedusting efficiency generally decreases with the increase in the nozzle diameter. However, when the diameter of the nozzle is less than 0.3 mm, the diffusion area of the water mist is insufficient to cover the tunnel cross-section, resulting in a decrease in dust removal efficiency. When the nozzle diameter is fixed, as the nozzle pressure increases, the dust reduction efficiency shows an increase, and the growth rate changes from a sharp increase to a slow increase, and gradually converges. When the fine water mist is within a certain range from the nozzle, its dust reduction efficiency has little relationship with the distance from the nozzle. While outside this range, the dust reduction efficiency will sharply decrease with increasing distance. Key words: Tunnel excavation, Mining method, Dust distribution, Water mist system, Model experiment.
13.10.2026
16:30 - 18:00
Room 0.5
Congress Conference
E. Complex underground projects: financial and organizational challenges
ORGANISATIONAL AND CONTRACTUAL CHALLENGES
Chairmen : Yann LEBLAIS (Paris, France), Jean GUILLAUME (Montrouge, France)
16:30-16:40
Introduction
16:40-17:00
Underground works: a fertile ground for innovative contractual practices
Joanna CLOSA (Paris, France)
17:00-17:20
Requirements management in a metro Design & Build contract: Grand Paris Express, Line 15 West, South section
Gerardo TORRES (Saint-Ouen-Sur-Seine, France)
17:20-18 :00
Follow-up to the Contractual Practices Observatory: progress of the work carried out by Working Groups GT17, GT25 and GT32
Maud MACARY (Lyon, France)
Elena CHIRIOTTI (Paris, France)
Jean GUILLAUME (Montrouge, France)
Underground construction projects are characterised by structural uncertainty arising from subsurface conditions, technical complexity and significant operational constraints. In this context, disputes are not isolated incidents but are often the result of a gradual accumulation of deferred decisions, contractual ambiguities and/or inadequate governance. Conflict thus emerges as the symptom of a project that has lost its capacity for cooperation. Too often, the contract is conceived as a defensive instrument, mobilised only at a late stage, once dialogue has already broken down. Yet in projects where uncertainty is inherent, this approach reveals its limitations and tends to fuel claims rather than to prevent them. By contrast, more mature practices seek to make the contract a genuine project management and steering tool. The development and active use of risk matrices, the implementation of real-time dispute resolution mechanisms (Dispute Boards), early warning procedures, collaborative approaches and project mediation, all help to organise uncertainty, share responsibilities and address tensions before they become entrenched. In conclusion, the article advocates a view of Contract Management as a fully-fledged governance discipline. In underground projects, contractual maturity does not lie in legal sophistication, but in the ability of stakeholders to identify risks, preserve dialogue and maintain cooperation in the face of the unexpected — an essential condition for performance and long-term trust. --- In the Line 15 West section of the Grand Paris Express, delivered under a design and build scheme, the management of the client’s requirements serves as a governance lever to ensure compliance, infrastructure–systems integration, and the effective control of technical and contractual risks across the project lifecycle. This section (approximately 15 km of tunnels, five underground stations, and seventeen service structures; €2.7 billion, 2023–2031) relies on more than 5,600 requirements spanning functional, technical, site, operations, maintenance, and FMD (RAMS) dimensions, thereby requiring disciplined traceability and continuous monitoring. The contractual framework specifies expectations for traceability and compliance demonstration, while leaving the consortium the latitude to define the operational arrangement. In the absence of established standards and off-the-shelf solutions comparable to those in industries (e.g., aerospace and nuclear) for managing cross-disciplinary requirements in an integrated infrastructure and systems context, the consortium implemented a phase-adaptive requirements management arrangement grounded in clarified responsibilities and validation criteria, structured management of deviations and changes, and a progressive coverage strategy aligned with design and approval milestones. The approach organises evidence production by distinguishing “structuring” requirements that drive architectural choices and system integration from those that can be demonstrated at later stages, thereby limiting rework and securing key trade-offs. Supported by a dedicated coordination team involving more than 300 contributors, this initiative has structured a requirements-oriented governance model, transforming the requirements baseline into a transversal steering instrument serving compliance, integration, and risk control within an integrated design and build schedule
13.10.2026
16:30 - 17:30
Agora
European Session
EUROPEAN SESSION: PROJECTS AND PERSPECTIVES PART 2
Chairman: Eric LECA (Paris, France)
16:30 - 16:40
Introduction
Eric LECA (PARIS, France)
16:40 - 16:50
AUTRICHE
Dietmar BACH (Salzburg, Austria)
16:50 - 17:00
GRECE
Andreas BENARDOS (Athens, Greece)
17:00 - 17:10
PAYS-BAS
Peter VAN WESTENDORP (MAARSSEN, The netherlands)
17:10 - 17:30
Discussion
13.10.2026
19:30 - 00:00
GALA DINNER
GALA DINNER