Study On The Seepage-stress-damage Coupling Model And Permeability Self-healing Of Clay

Clay-rich rock is a transitional material, with properties intermediate between soils and hard rock. under consideration as host rock for nuclear waste repositories.Clay formations are considered to be well suited for hosting radio-active waste repositories, because of their very low hydraulic conductivity, good creep,good sorption capacity of radio-nuclide and potential for self-sealing (of openings or gaps in formations). In Europe, France, Beigium and Switzerland have construeted underground laboratory in clay formations to investigate hydro-mechanical coupled behaviour of clay. The main research work of the dissertation has been constructed on elastoplastic damage constitutive model, seepage-stress-damage coupling model and self-healing model of clay. Through experimental research, theoretical analysis and numerical simulation, the mechanism of rock damage evolution, the mechanism of EDZ permeability evolution and the mechanism of self-healing are revealed, the mathematical models are established to describe the effect of excavation disturbance and self-healing, the basises for rock stability control and safety evaluation of nuclear waste repository are provided. The main achievements are stated as follows:(1) Failure characteristics and mechanical behavioral characteristics of typical clay repositories are systematically analyzed, excavation damaged mechanism of clay is revealed, and failure criterion is proposed, using the least energy consumption principle, the damage evolution equation is derived to describe the macro-micro failure characteristics and mechanical behavior, and the elastoplastic damage constitutive model is established. Using ABAQUS software, the corresponding numerical simulation program is compiled, the applicability and validity of the program is verified, the evolution of clay repository EDZ affected by the excavation is analyzed.(2) Penetration characteristics and permeability evolution of typical clay repositories are systematically analyzed, the dynamic evolution mechanism of clay permeability is revealed; according to the evolution curve of permeability in complete stress-strain process, the curve is divided into three phases in deformation and failure process: permeability decreases, permeability increases and permeability stabilizes; mutation characteristics for permeability near the expansion point, based on percolation theory, percolation characteristics of clay permeability is analyzed, the permeability evolution equation is derived, which can describe the macro mesoscopic hydraulics behavior of clay, the seepage-stress-damage coupling model is established, the coupled constitutive model is embedded into ABAQUS calculation software, and the numerical simulation calculation is implemented, using the model, the tunnel construction process is simulated, and space-time evolution laws of pore pressure, damage, permeability coefficient and so on are studied.(3) the laboratory and field tests on clay self-healing of typical disposal repository are systematically analyzed, the factors affecting self-healing process and the influence of various factors on the permeability are studied, the self-healing factors that should be considered in this paper are obtained, the self-healing mechanism of clay is revealed, the self-healing model of permeability is established, As a platform for secondary development of ABAQUS, the corresponding numerical calculation program is compiled, and the construction process of clay tunnel is numerically simulated, the self-healing effect on the evolution of pore pressure, damage, permeability coefficient and so on is analyzed.(4) Taking the Connecting Gallery of HADES underground research laboratory in Belgium for example, combined with the research results about clay mechanical properties, the elastic-plastic constitutive model, and permeability evolution model, For Connecting Gallery surrounding rock the simulation analysis on stress, deformation and pore pressure changes, the damage evolution, and the permeability evolution and so on is carried on, the deformation mechanism of clay nuclear waste repository and the groundwater migration law are revealed, which provide the basis for surrounding rock stability control and safety evaluation provide...