Geotechnical engineering & seismic risk
Geotechnics plays a role in many current societal issues relating to the sustainable maintenance of infrastructure assets, the safety of property and people (land movements, earthquakes, dykes and dams, etc.), environmental protection and natural resource conservation, energy management, and energy and ecological transitions (low-temperature geothermal energy, wind turbines, offshore devices, etc.).
The Geotechnical Engineering & Seismic Risk (IG & RS) theme brings together 25 research executives and 15 ITA staff. It unites four laboratories in the GERS department (CG, GIE, RRO, and SRO) located at the Marne-la-Vallée, Nantes, and Lyon sites. The expertise brought together within this theme relates to civil engineering, particularly soil and rock mechanics (geotechnics), but also geology, geophysics, seismology, physics, mineralogy, and soil and rock chemistry.
Research is conducted from several angles, enabling observation, understanding, and modeling. It is based on large-scale networks (RAP and Observil, for example), laboratory experiments, physical modeling on reduced models (particularly in geotechnical centrifuges), full-scale in situ experiments—including through the monitoring of actual construction sites—and the development and use of numerical models.
The teams have access to laboratory experimental platforms for analyzing and studying the mechanical properties of soils on the Nantes and Marne la Vallée campuses, as well as in situ measurement and instrumentation equipment (drilling machine, removable extensometers and jacks for foundation testing, self-drilling pressure gauge, etc.). In addition, two remarkable pieces of equipment complete this experimental arsenal: the Nantes geotechnical centrifuge for the physical modeling of geotechnical structures, including under seismic stress (thanks to the onboard earthquake simulator), and the Montagnole rockfall station in Isère for testing rockfall protection devices. Collaborations with the Navier UMR, CEREMA, and other departments also provide access to other equipment: MRI and large triaxial press (Navier), large shear box (CEREMA in Lyon), and 1.2 MJ hydraulic catapult for horizontal impact testing (TS2 department). Finally, the department's staff have contributed significantly to the development and coordination of the permanent accelerometric network (RAP), which is now part of IR Epos-France.
The main current research topics are:
the study of the mechanical behavior of interfaces and, in particular, the fatigue of foundations and anchors subjected to cyclic mechanical or thermal stresses (wind turbine foundations or geothermal foundations),
evaluating methods for treating and implementing fine soils in order to promote the use of materials in civil engineering,
measuring and modeling the complex response of soils during earthquakes,
evaluating and predicting the seismic response of structures.
Two research topics related to natural hazards have emerged in recent years:
the study of the behavior of structures, particularly earth structures under impact stress, around rockfall stations,
and the study of scouring processes in river and coastal structures.