(1. Institute of Mining Technology，Taiyuan University of Technology，Taiyuan，Shanxi 030024，China； 2. School of Mining Engineering，China University of Mining and Technology，Xuzhou，Jiangsu 221008，China)
Abstract：By utilizing the self developed “600 ℃ 20 MN servo-controlled rock triaxial testing machine with high temperature and high pressure”，the investigation into deformation characteristics of anthracite specimen with 400 mm in length and 200 mm in diameter was carried out at constant stress corresponding to the in-situ stress at the depth of 500 m (axial pressure is 12.5 MPa and confining pressure is 15 MPa)，increasing temperature from room temperature(20 ℃) to 600 ℃ at a rate of 10 ℃/h. The study results indicate that the process of temperature-dependent deformation of anthracite can be divided into three stages，i.e. thermal dilatation stage with temperature rising from room temperature to 200 ℃，slow volume compression stage from 200 ℃ to 400 ℃ and serious volume compression stage from 400 ℃ to 600 ℃. The critical temperature range of anthracite deformation mechanism transition from brittle to ductile is from 400 ℃ to 450 ℃. Temperature and pressure are the main factors which influence the brittle-ductile transition of coal mass. The principle of transition condition is temperature-pressure equivalent，i.e. higher critical temperature needs lower transition pressure. The deformation of coal mass is significantly influenced by thermo-mechanical coupling and pyrolysis gas，while the main factor at a high temperature is pyrolysis gas.
