In the underground environment with large buried depth and high ground stress, man-made disturbance is very easy to cause the rapid expansion of primary fractures in the rock, and then developed into the macrodynamic performance of rock. Based on the propagation law of elastic waves in discontinuous media, the application of acoustic emission detection technology can quickly determine whether there are primary fractures in the rock and predict its approximate location. In this work, CT scanning experiments of intact sandstone specimens and fractured sandstone specimens were performed. The gray value distribution of intact sandstone specimens and fractured sandstone specimens was studied. The sandstone specimens were divided into 4 zones (I~IV) from top to bottom. The height of each zone is from 0 mm to 25 mm, and the upper end face of each zone is the starting face. Acoustic emission experiments of intact sandstone and fractured sandstone are carried out based on the equilateral triangle sensor array. The dispersion of AE wave velocity and amplitude in intact sandstone specimens and fractured sandstone specimens is studied. The results show that the crack evolution law of sandstone specimens before and after preloading is closely related to the density distribution. The regular trend is from low density to high density. And the decay law of AE eigenvalue before and after preloading of sandstone specimen is consistent with the change trend of gray value. This shows that it is feasible to explore the spatial location of primary fractures and the degree of development of primary fractures in the rock through the equilateral triangle sensor array. In the actual project, it can provide some guidance and suggestions for related projects.

The thermomechanical (TM) coupling effects of rock bursts have attracted considerable attention from researchers owing to the high geothermal and geostresses in deep tunnels in regions such as Western China. To study the brittleness and rock burst mechanism under TM conditions, various tests, such as splitting, uniaxial compression, rock burst tendency, and rock burst physical model tests, were conducted at temperatures ranging from 20°C to 80°C. The results revealed that, when granite samples were heated, their tensile strengths decreased in the splitting tests. Their peak stresses and the corresponding strains increased; their macroscopic tensile fracture surfaces became more evident; and the microcosmic tensile properties of intergranular fractures became prominent under uniaxial compression. Rock burst physical model tests and acoustic emission monitoring results revealed that, at higher temperatures, the fracture degree and failure range were larger, the energy was higher and more concentrated during failure, and failure occurred earlier. The brittleness index B, rock burst tendency Wet, and σθ/σc all exhibited a clear increasing tendency with an increase in temperature. The rock burst mechanism, considering the temperature effect, can be summarized as follows: the increase in brittle tensile fracture components and geostress caused by temperature increasing is conducive to the rapid release of energy, which will promote the occurrence of rock burst. The researching result is of great academic value and practical significance for the prevention, design, and safe construction of rock burst in deep high geothermal tunnels.