深部冲击倾向煤岩循环加卸载的纵波波速与应力关系试验研究

Study of correlation between stress and longitudinal wave velocity for deep burst tendency coal and rock samples in uniaxial cyclic loading and unloading experiment

研究了单轴循环加卸载条件下深部冲击倾向煤岩样应力与纵波波速的耦合关系,基于煤岩试样在弹性阶段纵波波速变化梯度大,塑性阶段波速变化趋于平缓的特征建立了应力与纵波波速之间的试验关系模型,并对模型参数进行了分析。研究表明:①由于闭合的孔隙和裂隙又重新张开,颗粒之间的压实程度减弱,煤岩试样卸载过程中,随着应力的降低,波速也降低;②部分裂隙和孔隙在压密阶段发生永久闭合,造成应力降低后再无法张开,因此下一循环的开始纵波波速值要大于第一个循环开始时的波速值;③与实测值的相关系数计算结果表明,试验关系模型具有较高的拟合度,很好地体现了试样纵波波速变化对载荷的敏感程度。

Through the laboratorial research, the coupling correlation between stress and P wave velocity are studied under uniaxial cyclic loading and unloading ways to create the experimental model based on the characteristic that the velocity gradient is usually high at elastic stage and then begins to level out at plastic stage for burst tendency coal and rock samples from deep coal mine. Also the parameters of the derived model are analyzed. Studies indicate that： ①In the unloading process, the P wave velocity decrease with the drop of stress because of the reopen of closed crack and weakening in the compaction degree between grains; ②The starting P wave velocity of next cyclic is higher than the starting of first cyclic, because that partial crack and pore that closed permanently in the compression phase can not reopen when stress decrease; ③The calculated correlation coefficients to measured value show that the experimental model has the better fitness, and can be well applied to describe the P wave changing sensitivity degree of samples under stress.