Development of meso-shear test equipment for coal rock containing gas and its application

A self-developed meso-shear test equipment for coal rock containing gas is introduced. It is composed of main structure, loading system, gas-charging system, crack observation system and acoustic emission system. The equipment has the following features: (1) The shear mechanical tests for coal based on the fluid-solid coupling can be carried out, which provides reliable experimental means to study the mechanism of coal and gas outburst from micro level. (2) It has good airtightness, which can guarantee adequate adsorption of gas on coal sample. (3) The lateral loading system is designed, so both restrictive and non-restrictive shear tests can be carried out. (4) It has diverse methods to test experimental data. The curve of shear load and shear strain, images of meso-cracks and acoustic emission signal can be acquired synchronously. (5) From the view of its overall design, the equipment has simple structure, low processing cost, good reliability and easy operation. By using the equipment, non-restrictive direct shear tests under the gas pressures of 0.5, 1.0 and 2.0 MPa are carried out. Shear load-shear stain curve and meso-evolution of shear plane cracks are obtained. Based on the test results, the mechanical processes of the formation, extension, penetration and instability are analyzed. The experiment results show that the equipment has good practicality and reliability, and it provides new test means to study the meso-shear mechanical characteristics of coal.