Lamellar shale has stronger anisotropy than bedding shale, the compressive strength (deviatoric stress) and elastic modulus of lamellar shale are both lower than those of bedding shale, and it is more prone to tension fracture. The results demonstrate the following points. In addition, the mechanical mechanism was discussed combined with the CT scanning tests results from a microscopic point of view. In this study, using the lamellar shale in the continental stratum of the southern Ordos Basin, the mechanical properties of lamellar shale were studied by compression tests considering the effect of lamellar structure and hydration from a macroscopic point of view. This is because of that the mechanical properties (compressive strength, elastic modulus, etc.) of lamellar shale surrounding the borehole, which is rich in clay minerals, will decrease significantly after hydration. It is well known that the effect of shale hydration causes wellbore instability due to water phase invasion of drilling fluid to lamellar shale rich formations. The proposed rock shear apparatus can advance the quantitative study of the shear creep properties of rock samples during moisture content changes and has certain practical application value for the prediction of engineering rock mass stability during rainfall. The experimental results revealed that there are significant differences in the long-term shear strength and deformation of argillaceous shale under different moisture content conditions. Shear creep tests of argillaceous shale were conducted under both constant and dynamic moisture conditions, and the results were described by the Nishihara model. By using silicone gasket and seals in the shear box, fluid injection at a pressure of 5 MPa was achieved without leakage. Since three prefabricated holes are drilled in the upper part of the rock sample, the water injection device and the gas injection device can be used to inject water and gas into the rock sample alternately during the test to adjust the moisture content without removing the normal load and shear load. In order to investigate the effect of moisture content change on long-term shear strength and deformation behavior, a shear apparatus for intact rock was developed. Under field conditions, the moisture content of rock changes with the weather during prolonged creep.
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