Physical Simulation and Acoustic Emission Characteristics of Sandstone Hydraulic Fracturing under True Triaxial

In order to reveal the rock breaking mechanism of hydraulic fracturing, a set of indoor rock hydraulic fracturing physical simulation system was established by using a true triaxial loading system, acoustic emission instrument and high pressure piston pump, which can study the rock breaking mechanism of hydraulic fracturing. Based on the Griffith strength criterion, the critical water pressure and the location of rock fracture initiation are established. The experimental results are as follows: When the water pressure is far below the critical pressure, the acoustic emission characteristics of sandstone are more obvious in the rising period of water pressure, and the acoustic emission characteristics of sandstone are quiet in the maintaining period of water pressure, and the signal is that the primarily closed microfractures of sandstone are pressed open; When the water pressure is close to the critical pressure, the impact number, amplitude and energy of acoustic emission of sandstone increase in the rising period and maintaining a period of water pressure, and the signal is the expansion and coalescence of new fissures caused by sandstone fracture; The direction of fracture initiation and propagation is perpendicular to the direction of the minimum principal stress, and the primary fractures control the direction of fracture initiation and propagation. The research results provide a reference for the hydraulic fracturing treatment of coal mine fine sandstone thick main roof.