Triaxial Creep Behavior of Coal Containing Gas in Laboratory

Abstract

Based on laboratory results of time-dependent mechanical behavior tests, the creep property of coal containing gas is investigated under different load conditions, using servo-controlled triaxial rheology testing machine at room temperature. The effect of effective axial stress, effective confining pressure and gas pressure on the creep behavior of coal containing gas is discussed respectively in detail. At primary creep stage, creep strain rate of coal samples, which can be described by a power function, decreases gradually with testing time. At steady-state creep stage, effective axial stress, effective confining pressure and gas pressure are important factors which affect the creep strain rate of coal samples. An exponential function is proposed to model the effect of effective axial tress on creep strain rate, at the same time, a linear equation can be used to describe the effects of effective confining pressure on creep strain rate. While, gas pressure influences indirectly the creep behavior of coal containing gas through making a change of the value of effective stresses. Accelerating creep stage is the last stage of non-attenuating creep and the beginning of coal samples failure, as well. Macro-cracks will be produced and lead to the failure of coal samples finally as far as accelerating creep stage appears.