The Stock-en-socle project aims at acquiring the necessary knowledge for the periodic storage of sensitive heat in hardrock aquifers characterized by their low permeability. Though geothermal energy storage boreholes remain the only existing solutions proposed in a low-permeability environment, Stock-en-socle examines the possibilities of heat storage through semi-open circulation of water in a well. This is, typically, a SCW (Standing Column Well) and takes advantage of the strong heterogeneity of hardrock aquifers, targeting zones that are the least favorable for water-resource exploitation. The main identified scientific problems facing the project concern the minimum level of permeability required around the well and its evolution with time (increase and decrease) through water-rock interaction processes. A scientific and technical program, including modeling and experimental laboratory and fieldwork, will study the thermal, hydraulic and geochemical processes involved. The study area for field tests, located in French Brittany, will test different geological settings (granite, gneiss and schist). Tracer tests and a long-term circulation test by injection of warm water within a single well (push-pull), will be carried out. Hydrothermal modeling will study the effects of permeability structures on the capacity of storage and recovery of thermal energy, while reactive-transfer modeling will simulate the evolution of permeability under the impact of dissolution and precipitation reactions. Based on the obtained results, technical solutions will be studied for drilling and equipping an SCW well in a low-permeability context. This work will be completed by a technical/economic feasibility study for proposing an investment and operations model. The end result will be description of the suitability of heat storage in SCW well connected to a small heat-distribution network. To reach the defined goals, Stock-en-Socle will be based on a public/private partnership with two public institutions devoted to research activities, a university and a public establishment with an industrial and commercial character, and two private companies working in the field of geothermal energy and soil technology. In addition to the dissemination of its results to the scientific community, Stock-en-socle will identify the possibilities for further work as part of the project, in terms of setting up an industrial research project to be implemented in Brittany.

The ISOLATE project aims at improving the characterization of the liquefaction potential of saturated natural soils and their physical and numerical modelling in order to assess the response of actual geostructures and to reduce the liquefaction hazard (through mitigation) accounting for the current seismic requirements. The academic and industrial teams of the project thus propose: WP1/ the characterization at the scale of the material (cyclic triaxial tests, resonant column, shear box, calibration chamber, in situ pressuremeter), WP2/ the characterization at the scale of the foundation soil and the assessment of scale effects (centrifuge experiments, shaking table tests, innovative laminar boxes), WP3/ the analysis of the effects of liquefaction on structures (physical and numerical modelling), WP4/ to reduce the hazard and assess an innovative mitigation technique (improvement by biocalcification), WP5/ to edit practical recommendations and promote the technical results (database for soil parameters, reference results from physical models, scientific papers, design charts and practical recommendations). WP1: this WP aims at defining the soil parameters for the numerical models as well as the procedures able to characterize the behavior of saturated soils under dynamic excitations (sandy soils with various fine contents). WP2: laboratory tests (centrifuge and shaking table) on a reference sand column characterized in WP1 will be performed. An experimental database will allow to analyze scale effects and to verifying the numerical models for the foundation soil. WP3: this WP aims at: designing interaction tests between the foundation soil and a structure under controlled conditions; validating simulations from experiments; defining reliable proxies to quantify the stability and the damage of structures through performance-based approaches; check simplified criteria for the assessment of the liquefaction hazard with respect to observations. WP4: the efficiency of the mitigation technique (biocalcification) will be assessed from treated physical models (shaking table and centrifuge) with respect to the specifications from WP2 and WP3 and numerical simulations will be performed to model the phenomenon. WP5: the project will propose additional recommendations to the AFPS 2020 working group. It will bring to the engineering community validated assessment tools allowing to reduce the cost of the studies. The consortium of the project is fully relevant since the research partnership involves public research centers (CEA, IFSTTAR), academics (CentraleSupélec, ENPC), private companies (EDF, SolétancheBachy), with complementary expertises and skills in experiments, modelling and geotechnical engineering. The involved research teams have a long experience and a strong know-how in the field of mechanical and dynamic tests on soils and geostructures, and bring their expertise in physical and numerical modelling, in order to improve the knowledge on complex phenomena from the grain scale to the structural scale, as well as engineering practice. Indeed, the contribution to the project of renowned private companies ensures that the economic players will take advantage of the scientific and technical advances: as a hydraulic facilities owner, EDF is able to identify the needs for engineering and to target appropriate promotions; Solétanche-Bachy proposes an innovative mitigation methodology and may use its national and international network to disseminate the results of the project.