单轴循环荷载对煤弹塑性和能量积聚耗散的影响

为了研究循环加载对煤岩弹塑性和能量积聚耗散的影响,对二2煤进行了单轴压缩循环加载实验,分析得出首次加载、卸载、再加载弹性模量呈正相关关系;随着循环数的增加,弹性应变会表现出倒"U"形变化,塑性应变表现出"U"形变化的规律,由应变引起的弹性模量E、弹性能量指数Wet和能量耗散率Wed都表现出倒"U"形变化的规律,首个平均弹性模量变化率η为30%,耗散的能量j sd呈"U"形变化,当弹性能量指数Wet达到最大值时,冲击现象最容易发生;分析出微裂纹的萌生传播速度随应力振幅的增加而增加,微塑性变形速度也随之增加,弹性能量指数在压密和线弹性阶段随加载程度的增加表现出先增加后减小的趋势,在"弹塑性临界点"达到最大值.

Influence of cyclic uniaxial loading on coal elastic-plastic properties and energy accumulation and dissipation

In order to investigate the influence of cyclic loading on the coal-rock elastic-plastic properties and energy accumulation & dissipation,the cyclic loading test on uniaxial compression on Coal 22 was conducted in this study.Based on the analysis results,the first loading and unloading,and reloading are positively correlated with elasticity modulus.With the increase of cycle number,the elastic strain appears in an inverted U-shape rateηof elasticity modulus is 30%,and the energy dissipation j sd follows a U-shape change.When elastic change while the plastic strain exhibits a U-shape change.All the elasticity modulus E,elastic energy index Wet and energy dissipating rate Wed caused by strain follows an inverted U-shape change.The first average variation energy index Wet reaches its maximum,a burst phenomenon will easily occur.With the increase of stress amplitude,the speed of production and propagation of micro-crack will increase,as well as the micro-plastic deformation speed will also increase.With the increase of loading level,the elastic energy index shows a tendency of increasing earlier and decreasing later during the compression and linear elasticity period,and reaches the maximum at "elastic-plastic critical point".