层状盐岩及泥岩夹层动态力学特性对比试验研究

为对比研究盐岩和泥岩夹层的动态力学特性,以应城盐矿的盐岩及泥岩夹层为研究对象,利用带围压的分离式Hopkinson(SHPB)试验装置,进行不同围压(5,15,25 MPa)下的动载冲击试验研究,分析盐岩和泥岩夹层动力特性的围压效应与应变率效应,基于联合的热活化与黏性机制相互竞争的材料强度–应变率依赖的简化模型拟合出盐岩及泥岩夹层的动力强度公式。研究结果表明:(1)盐岩和泥岩夹层均属于率敏感性材料,其峰值应力和延性随应变率的增大而增加,但低围压(如5 MPa)作用下应变率强化效应较高围压(如25 MPa)作用下更加显著;(2)盐岩和泥岩夹层在动力荷载条件下的力学行为的围压效应没有静力荷载条件下明显,动力放大系数(DIF)随着围压增加而减小,泥岩夹层的围压效应要小于盐岩的围压效应;(3)动力强度计算公式拟合效果较好,盐岩平均相对误差为2.51%,泥岩夹层平均相对误差为6.58%。

Comparative experimental study on dynamic mechanical properties of bedded salt rock and mudstone interbed

In order to compare the dynamic mechanical characteristics of salt rock and mudstone interbed，the salt rock and mudstone interbed from Yingcheng were studied with the split Hopkinson pressure bar(SHPB) apparatus under triaxial confining pressures of 5，15 and 25 MPa. The formula for the dynamic strength of salt rock and mudstone interbed were derived by data fitting according to a simplified strength-strain rate model on competition between the mechanisms of thermal activation and the macro-viscosity. The results show that the salt rock and mudstone interbed are sensitive to the strain rate，that their peak stress and ductility increase as the strain rate increases，but that the strengthening effect of strain rate under the low confining pressures(such as 5 MPa) is more obvious than that under the high confining pressures(such as 25 MPa). The confining pressure effect on the mechanical behavior of salt rock and mudstone interbed under the dynamic loading condition is less obvious than that under the static loading condition. The dynamic increasing factor(DIF) decreases as the confining pressure increases，and the confining pressure effect of mudstone interbed is smaller than that of salt rock. The formula for dynamic strength fits data well with the average relative errors of 2.51% and 6.58% for salt rock and mudstone interbed respectively.