Development and application of a novel ring shear apparatus

The total stress, pore water pressure and effective stress of the sample can be obtained by developing a new ring shear apparatus for measuring and controlling pore water pressure, and the stress-strain-pore water pressure characteristics of the sample can be effectively revealed. In this paper, the self-developed automatic ring shear apparatus can control the drainage conditions, and realize the control of pore water pressure during the ring shear process, and measure the pore water pressure, sample drainage volume, torque and axial displacement. Taking the slip zone soil of Huangtupo landslide as an example, the consolidated drainage ring shear test, consolidated undrained ring shear test, variable pore pressure ring shear test and constant head permeability test were carried out respectively. The test results show that the ring shear chamber can withstand 0~1000kPa pore water pressure by using side seal and top and bottom tee valve. When the inlet valve at the bottom of the lower ring shear box is opened and the volume pressure controller is connected, the pore water pressure can be controlled and the volume of drainage or absorption of the sample under a certain pore pressure can be measured with a measuring range of 0~200cm3. When the outlet valve at the top of the upper ring shear box is opened and the pore water pressure sensor is connected, the pore water pressure inside the sample under undrained conditions can be measured with a range of 0~1000kPa. During the test, the shear dilatancy or shear contraction was measured by the axial displacement sensor with a measuring range of 0~10mm. The ring shear force is measured by a torque sensor with a range of 0~300N·m. In addition, the influence of dynamic change of pore water pressure on ring shear strength and the change of sample permeability coefficient during consolidation or ring shear can also be tested with the new ring shear apparatus. A novel ring shear instrument can accurately carry out mechanical tests of specimens under large deformation and different pore pressure conditions to provide technical supports for revealing the evolution mechanism of pore water pressure during long distance landslide sliding.