Ifsttar PhD subject

French version
Detailed form :

Title : Structural behaviour of compressible segments ring of a deep tunnel : structural health monitoring via embedded sensors

Main host Laboratory - Referent Advisor MAST - EMGCU  -  SCHMIDT Franziska      tél. : +33 181668344

Director of the main host Laboratory MARTIN Renaud-Pierre  -

PhD Speciality Génie Civil

Axis of the performance contract 2 - COP2017 - More efficient and resilient infrastructure

Main location Marne-la-Vallée

Doctoral affiliation UNIVERSITE GUSTAVE EIFFEL

PhD school SCIENCES, INGENIERIE ET ENVIRONNEMENT (SIE)

Planned PhD supervisor SCHMIDT Franziska  -  Université Gustave Eiffel  -  MAST - EMGCU

Planned financing Contrat doctoral  - Université Gustave Eiffel

Abstract

This thesis is part of the technological and demonstration tests of the Cigéo project, the French project for a deep storage center (500 m) for radioactive waste in connection with the sizing of the works for a future operating period of the order of 150 years. When digging, the surrounding clayey rock presents an initially anisotropic convergence which evolves over time.
Andra with its partners has developed an innovative solution to limit the effect of terrain convergence on the loading of the concrete covering by “capping” the forces in the segments. This solution is based on the use of a compressible layer integrated into the upper surface of the segment. This compressible layer has the effect of limiting the radial stresses transmitted to the segment ring throughout the operating phase.
Faced with the challenge of the program, Andra contacted the Gustave Eiffel University in order to develop a test bench allowing this ring to be subjected to an isotropic or anisotropic field of displacements reproducing the convergence of the terrain at different ages of the life of the works. Since 2021, tests have been carried out on a ring of segments with different types of loading – isotropic, anisotropic with variable ratios, with or without compressible layers. As of December 1, 2022, four tests have been carried out in a program of fifteen tests carried out by the end of 2025. These large-scale tests are exhaustively instrumented, generating a large volume of raw data. Among the 250 sensors used, around a hundred are sensors embedded in the segments.
In this context, the objectives of this thesis are multiple and multidisciplinary. The doctoral student will actively participate in monitoring the scale 1 test campaign. Thanks to the results of these tests, he/she will develop a tool to characterize the structural health of a ring of instrumented segments based on the only internal instrumentation. This tool will be able to take into account the service requirements required by the galleries of the Cigéo project. He/she will be able to combine the analytical methods already developed by the EMGCU laboratory with numerical calculation methods such as finite elements and inverse analysis.
This study will be directed by F. Schmidt (Doctor HDR), deputy director of the EMGCU laboratory, supervised by the leaders of this study: B. Terrade (Doctor) and L. Kerner (Doctor) for the Gustave Eiffel University and J. Zghondi (Doctor) for Andra.

Keywords : Compressible arch segment ; full scale testing, SHM ; tunnel ; deep geological storage

Main host Laboratory - Referent Advisor	MAST - EMGCU - SCHMIDT Franziska tél. : +33 181668344
Director of the main host Laboratory	MARTIN Renaud-Pierre -
PhD Speciality	Génie Civil
Axis of the performance contract	2 - COP2017 - More efficient and resilient infrastructure
Main location	Marne-la-Vallée
Doctoral affiliation	UNIVERSITE GUSTAVE EIFFEL
PhD school	SCIENCES, INGENIERIE ET ENVIRONNEMENT (SIE)
Planned PhD supervisor	SCHMIDT Franziska - Université Gustave Eiffel - MAST - EMGCU
Planned financing	Contrat doctoral - Université Gustave Eiffel
Abstract This thesis is part of the technological and demonstration tests of the Cigéo project, the French project for a deep storage center (500 m) for radioactive waste in connection with the sizing of the works for a future operating period of the order of 150 years. When digging, the surrounding clayey rock presents an initially anisotropic convergence which evolves over time. Andra with its partners has developed an innovative solution to limit the effect of terrain convergence on the loading of the concrete covering by “capping” the forces in the segments. This solution is based on the use of a compressible layer integrated into the upper surface of the segment. This compressible layer has the effect of limiting the radial stresses transmitted to the segment ring throughout the operating phase. Faced with the challenge of the program, Andra contacted the Gustave Eiffel University in order to develop a test bench allowing this ring to be subjected to an isotropic or anisotropic field of displacements reproducing the convergence of the terrain at different ages of the life of the works. Since 2021, tests have been carried out on a ring of segments with different types of loading – isotropic, anisotropic with variable ratios, with or without compressible layers. As of December 1, 2022, four tests have been carried out in a program of fifteen tests carried out by the end of 2025. These large-scale tests are exhaustively instrumented, generating a large volume of raw data. Among the 250 sensors used, around a hundred are sensors embedded in the segments. In this context, the objectives of this thesis are multiple and multidisciplinary. The doctoral student will actively participate in monitoring the scale 1 test campaign. Thanks to the results of these tests, he/she will develop a tool to characterize the structural health of a ring of instrumented segments based on the only internal instrumentation. This tool will be able to take into account the service requirements required by the galleries of the Cigéo project. He/she will be able to combine the analytical methods already developed by the EMGCU laboratory with numerical calculation methods such as finite elements and inverse analysis. This study will be directed by F. Schmidt (Doctor HDR), deputy director of the EMGCU laboratory, supervised by the leaders of this study: B. Terrade (Doctor) and L. Kerner (Doctor) for the Gustave Eiffel University and J. Zghondi (Doctor) for Andra.
Keywords :	Compressible arch segment ; full scale testing, SHM ; tunnel ; deep geological storage

List of topics

Applications closed