Method of Testing Mountain Rocks for Cracking Resistance in Longitudinal Shear

Purpose. Justification of the methodology of rock research for crack resistance during longitudinal shear for the developed test device. Method. Method of laboratory investigation of fracture toughness of rocks under tension; methods of laboratory investigation of fracture toughness of rocks under transverse and longitudinal shear; analytical method for calculating shear stresses under torsional moment; analytical method for calculating the fracture toughness of rocks under longitudinal shear. Results. To predict roof collapse, the parameters of crack propagation in the rock mass above the mined-out area, the formation of rock falls, and gas-dynamic phenomena, it is necessary to take into account the processes of rock failure and fracturing of the rock mass. Laboratory investigation of the fracture resistance of rocks is a crucial task for forecasting roof collapse, rock falls, and gas-dynamic events. Therefore, the aim of this study is to justify the testing methodology for determining the fracture resistance of rocks under longitudinal shear using a specially designed device. A device has been developed and implemented for testing the fracture resistance of rock samples under longitudinal shear. To study the rock failure process in laboratory conditions, considering each failure mode, auxiliary testing tools were developed, and a methodology was substantiated for determining the fracture toughness parameters of rocks under longitudinal shear. A validated analytical method was proposed for calculating the fracture toughness parameters of rocks under longitudinal shear. Scientific novelty. For the first time, devices were developed to determine the fracture toughness of rocks taking into account the following types of fracture: tensile fracture toughness, transverse and longitudinal shear fracture toughness. For the first time, the method of testing rocks for crack resistance during longitudinal shear is substantiated. For the first time, the dependence of the calculation of the fracture toughness of test samples during longitudinal shear was established. Practical significance. The practical significance lies in determining the fracture toughness of rocks during tension, transverse and longitudinal shear.