Experimental Analysis Of Hydro-mechanical Coupling Properties Of Clay Rock In The Tamusu Pre-selected Area

Clay rock is considered as one of the good alternative host rocks for geological repository of high-level radioactive waste.In this paper,clay rock in the Tamusu pre-selected area is taken as the research object.Through scanning electron microscope experiment,mercury injection experiment,point load experiment,uniaxial triaxial experiment,permeability experiment,and using FLAC3D finite difference software to carry out numerical simulation,the physical and mechanical characteristics,microscopic structural characteristics and hydro-mechanical coupling properties of clay rock in the Tamusu pre-selected area are studied.The main research results are as follows:?1?The basic physical properties of clay rock in the Tamusu pre-selected area were tested.The experimental results show that the average block density of clay rock in the Tamusu pre-selected area is 2.37g/cm³,the particle density is 2.59².74g/cm³,the average water content is 5.79%⁶.75%,and the porosity is 0.4%¹9.0%.With the increase of depth,the density of blocks increases and the porosity tends to decrease.The pore throats of claystone are mainly nano pore throats and micro capillary pore throats.The clay rock is an extremely dense rock sample.?2?Through uniaxial and triaxial tests of clay rock in the Tamusu pre-selected area,the stress-strain characteristics of clay rock were studied and some mechanical characteristic parameters were obtained.Research shows that with the increase of depth,the peak strength,elastic modulus and poisson's ratio of clay rock increase.The relationship between stress and volume strain of clay rock satisfies exponential function.?3?Gas and liquid permeability experiments were carried out for clay rock in the Tamusu pre-selected area.The experimental results show that the gas permeability of clay rock is generally 10^-17m² and the liquid permeability is 10^-20m².The permeability of clay rock in parallel bedding direction is higher.In the process of confining pressure loading,the permeability of clay rock decreases.In the process of confining pressure unloading,the permeability increases,but cannot return to the original value.Under the same osmotic pressure,with the increase of confining pressure,the peak strength increases and the permeability decreases.Under the same confining pressure,with the increase of osmotic pressure,the peak strength decreases and the permeability increases.The confining pressure plays a dominant role in the peak strength of clay rock,and the influence degree of osmotic pressure is relatively small.?4?The permeability evolution laws of clay rock in the Tamusu pre-selected area were studied.The study shows that the relationship between permeability and confining pressure satisfies exponential function in the loading stage.In the unloading stage,this relationship satisfies power function.The relationship between permeability and stress before peak value satisfies negative power exponential function.Moreover,deformation has more obvious influence on permeability for clay rock with low porosity.?5?FLAC3D finite difference software was used to simulate clay rock and the chamber of the repository in the Tamusu pre-selected area.The simulated peak strength is close to the experimental value.In addition,the pore water pressure on the tunnel wall is equal to atmospheric pressure.The further away from the tunnel wall,the larger the pore water pressure is,which is close to the value of the original rock.The biggest deformation of host rock occurs at the top of roadway.The problem of chamber deformation instability is not easy to occur.