循环荷载作用下煤岩强度及变形特征试验研究

EXPERIMENTAL STUDY ON CHARACTERISTICS OF STRENGTH AND DEFORMATION OF COAL UNDER CYCLIC LOADING

采用MTS815.03电液伺服岩石试验系统,对鲍店矿3煤在循环荷载作用下的强度、变形及疲劳损伤过程进行研究。研究结果表明,煤岩比其他坚硬岩石更容易发生疲劳破坏,单轴循环荷载作用下鲍店矿3煤的疲劳破坏“门槛值”不超过其单轴抗压强度的81%,且在疲劳破坏“门槛值”以下进行循环加、卸载时,也会产生一定程度的疲劳损伤;煤岩轴向变形可划分为初始变形、等速变形和加速变形3个阶段,横向变形可划分为稳定变形和加速变形2个阶段,当横向变形明显加大,且卸载时变形恢复很小时,则预示着煤岩将发生破坏。循环荷载作用下,煤岩随循环次数的疲劳破坏过程可反映从压密、应变硬化到软化的发展过程,也可反映其损伤演化过程。

The strength,deformation and fatigue damage process of coal samples No.3 from Baodian Colliery under cyclic loading are studied through experiments by MTS 815.03 servo-controlled rock mechanical test system.The results indicate that the coal is more inclined to fatigue breakage than other harder rocks.Under uniaxial cyclic loading,the fatigue failure “threshold value” of coal samples No.3 from Baodian Colliery is smaller than 81% of the uniaxial strength;and there will also be a certain extant of fatigue damage when cyclic loading and unloading experiment are carried out below the fatigue failure “threshold value.”Axial deformation can be divided into three stages：initial deformation,constant velocity deformation and accelerating deformation.Radial deformation can be divided into two stages：stable deformation and accelerating deformation.When radial deformation obviously increases and the deformation resumes only a little while removing the load,the coal is going to break.Under cyclic loading,the fatigue damage process with cyclic loading times of coal reflects the process from compressive close,strain hardening to strain softening,as well as the damage evolvement process.