循环荷载下煤岩弹塑性损伤的能量机制分析

Energy mechanism analysis on elastoplastic damage of coal under cyclic loading

为探究采动应力周期性扰动下煤岩的损伤变形及能量演化机制,利用含瓦斯煤热-流-固耦合三轴伺服渗流试验装置,开展不同稳定时间下煤岩三轴循环荷载试验;基于能量参数分析,推导出循环荷载作用下煤岩弹塑性损伤变量计算公式,分析煤岩弹塑性损伤演化行为。研究结果表明:不同稳定时间下煤岩主应力差-轴向应变曲线呈现周期性滞回环演化趋势,在稳定时间和外部荷载下弹性模量并没有随循环次数的增大而减小,煤岩损伤机制发生变化;煤岩吸收的总能量U与耗散能Ud随循环次数的增加总体变化趋势为L型,弹性能Ue逐渐减小而后趋于稳定;基于能量计算的煤岩弹塑性损伤变量值在30次循环荷载过程中,均在一稳定值附近呈波动性稳定变化趋势。

In order to explore damage deformation and energy evolution mechanism of coal under periodic disturbance of stress,cyclic loading tests with different time lengths of stabilization were carried out by using servo-controlled triaxial seepage device for thermo-fluid-solid coupling of coal containing methane.Then,based on analyses of energy parameters,a calculation formula of damage variables of coal under cyclic loading was derived,and evolution behaviors of its elastoplastic damage were analyzed.The experimental results show that the principal stress difference-axial strain curves of coal under different stability time conditions present a periodic hysteresis loop trend,elastic modulus do not decrease with the increase of cycle numbers under stability time and external load,and damage mechanism changes.The total energy absorbed U and dissipative energy Udchange with the increase of cycle numbers in an overall trend of L,and elastic strain Ueis gradually reduced and tends to be stable.In the process of 30 cyclic loads,elastoplastic damage variables of coal based on energy calculation show a tendency of fluctuating and stable changes around a stable value.