Mechanical Properties Of Clay Rocks From Tamusu Area

Clay rock is one of host rocks for high-level radioactive waste(HLW) disposal repository. Tamusu area, Inner Mongolia Autonomous Region, is an important area for HLW disposal repository candidate site of clay rock. Physical, chemical and mechanical properties of clay rock are important to the evaluation of candidate sites. Physical, chemical and mechanical properties of clay rocks from Tamusu area has been studied systematically by experiment, the variation of mechanical properties and the reason has been analyzed. Obtain some understandings below:(1) Clay rock has compact structure and high level degree of consolidation. It is mainly composed of clay mineral, Albite, Dolomite and Analcite, and the mineral particles are fine and evenly distributed.(2) The natural moisture of clay rock is 1.11~2.52%, the natural bulk density is 2.25~2.65 g/cm3, the particle density is 2.41~2.72 g/cm3, the porosity is 2.58~6.64%. The Specific surface area is 10.24~39.78m2/g which means it has outstanding adsorption properties. The permeability coefficient is 10-8~10-9 cm/s which belongs impermeable rock materials. Its properties stratify the requirements of repository.(3) The deep intact clay rocks in Tamusu area have the properties of high velocity, high mechanical strength and low strain and brittleness. It’s wave velocity, tensile strength, compressive strength is related to the bulk density. Its mechanical strength is uncorrelated with depth because of the compact structure. Its mechanical strength and deformation increased with increasing of the confining pressure, and peak stress decreased rapidly accompanied by the rapid expansion of the volume after destruction which shows the characteristic of strain softening. The deformation characteristic is brittle fracture because the micro cracks of clay are non-stable fracture propagation. Furthermore, its mechanical strength decreased with increasing of the temperature, and clay rock shows plastic deformation characteristic in the condition of 30 MPa and 90℃.(4) The deformation feature in the condition of uniaxial compressive pressure has been simulated by FLAC 3D, and the displacement during the loading process has been recorded. The result is similar with the actual situation by compared with the actual texting, which means the Mohr-Coulomb constitutive model and relative material parameters could reflect the status of clay rock to some extent.(5) Compared with the overseas clays as the host rocks for HLW repository, such as the Opalinus Clay in Switzerland and Callovo-Oxfordian clay-stone in France, the clays from Tamusu represented higher mechanical strength and elastic modulus. It provides an important basis for selection of host rocks of HLW disposal repository.