Creep characteristics and constitutive model of gas coal mass under high temperature and triaxial stress

Abstract：Utilizing the 20 MN servo-controlled triaxial rock testing machine with high temperature and high pressure developed by China University of Mining and Technology,experimental study was carried out on the creep properties of large size gas coal specimens of 200 mm×400 mm under two temperature points of triaxial stress at 200 ℃ and 400 ℃.The research results indicate that the gas coal experiences the first and second phases of creep at 200 ℃,but without acceleration of creep;and phase that creep accelerates appears after a short time at 400 ℃.In the joint action of temperature and stress,the gas coal specimens show typical sticky-elastic-plastic deformation;because of the moment and subsequent deformation in the loading process,coal specimens are always accompanied by significant plastic deformation.By the analysis of the permeability and porosity of gas coal under different temperatures,it was initially judged that 300 ℃ is the critical temperature of the change of creep characteristics about gas coal.On the basis of high-temperature creep characteristics of gas coal,a new type of nonlinear dashpots was introduced,and a creep constitutive model under high temperature aimed at gas coal was built,which theoretical curves of axial creep could agree well with the experimental curves,which indicating that this constitutive model can preferably simulate the creep characteristics of the gas coal under high temperature.