Experimental investigation on the nonlinear characteristics of energy evolution and failure characteristics of coal under different gas pressures

Studying the energy evolution characteristics of coal in a deep underground engineering environment will help people to understand the evolution process and induced mechanism of geological disaster and risk. To explore the influence mechanism of gas pressure on coal deformation, failure, and energy evolution, triaxial compression tests of coal under different gas pressure conditions were conducted in this study. Based on the test data, the mechanical properties, acoustic emission (AE) energy characteristics, and nonlinear characteristics of the energy evolution of coal containing gas were obtained. A theoretical formula for analyzing energy evolution is introduced. After this theoretical formula is verified by test data, the evolution characteristics of three energy rates (derivative of energy to stress) of coal are obtained based on this formula. It is found that energy rate can be used as a new effective mechanical parameter to analyze and predict the damage and failure characteristics of coal. The energy dissipation characteristics before the peak can be divided into two types: high dissipative energy rate type (HDERT) and low dissipative energy rate type (LDERT), which indicates different failure modes (plastic failure and brittle failure). On this basis, the ratio of dissipative energy rate and input energy rate is further defined to effectively distinguish the two types of dissipative energy rates of coal mass. The research results are helpful to explore the fracturing evolution and energy driving mechanism of coal, and then play a guiding role in rock instability prediction and support and reinforcement measures selection.

Automated summary

This study conducted triaxial compression tests on coal under different gas pressure conditions to explore the influence mechanism of gas pressure on coal deformation, failure, and energy evolution. The mechanical properties, acoustic emission energy characteristics, and nonlinear characteristics of coal containing gas were obtained based on the test data. A theoretical formula for analyzing energy evolution was introduced and verified by test data. The research results indicate that energy rate can be used as a new effective mechanical parameter to analyze and predict the damage and failure characteristics of coal. The findings on energy dissipation characteristics and the defined ratio of dissipative energy rate and input energy rate provide insights for understanding the fracturing evolution and energy driving mechanism of coal.