灰岩在三轴变围压循环压缩中的变形特征研究

STUDY OF DEFORMATION BEHAVIOURS OF LIMESTONE UNDER CYCLE TRIAXIAL COMPRESSION WITH DIFFERENT CONFINING PRESSURES

岩石在周期荷载作用下的力学性能是影响岩体工程长期稳定性的重要因素之一,需研究循环荷载作用下岩石的特性及演化规律。首先采用声波纵、横波波速测量方法,对岩样进行筛选。设计灰岩在施加不同围压和恒定循环上限应力作用下,三轴变围压循环加卸载下岩石变形特征测试方案。三轴变围压循环试验在GCTS-1000型岩石力学测试系统上进行,通过对试验结果的分析表明:(1)灰岩在变、恒围压加、卸载循环中,形成一封闭的塑性滞回环。在轴向变形上滞回环面积逐次缩小;而变围压循环在径向变形上滞回环面积逐次增大,而恒围压循环在径向变形上滞回环面积几乎相等。(2)在三轴变围压循环压缩试验中,围压增加和循环上限应力不变,残余变形量随着循环次数的增加而呈现出一个递减的趋势,轴向应变和径向应变的发展趋势是相反的。(3)在整个循环加卸载过程中,各个加卸载阶段变形模量值不同,卸载阶段变形模量高于加载阶段变形模量。(4)变围压循环加、卸载阶段变形模量的值大于恒围压循环加、卸载阶段下变形模量的值。通过试验,揭示灰岩在三轴变围压循环下,加载和卸载2种力学状态时变形特性的差异。同时分析变围压循环和恒围压循环状态下岩石弹性参数的差异性。

The mechanical behavior of rock under cycle load is the one of most important factors which could effect on the long-term stability of rock matrix. So the rock behavior and evolving regular of rock under circulation load are needed to be researched. The samples are selected through the wave velocities of compression wave and shear wave. The rock deformation tests are measured under different confining pressures, constant cycle upper limit confining pressures and triaxial altering confining pressure cycle loading. Triaxial altering confinement pressure cycle test is performed on the GCTS - 1 000rock mechanic test system. The test results are as follows： （1） The deformation of limestone forms a closed plastic sluggish winding when the limestone is loaded or unloaded under altering or constant confining pressure. The areas of plastic sluggish winding diminish succession on the axial deformation; the areas of plastic sluggish winding under altering confining pressure increase succession on the radial deformation the areas of plastic sluggish winding under constant confining pressure are almost equal. （2） In the triaxial altering confining pressure test, the residual deformation displays a scaling down tendency in condition that the confinement pressure increases and the cycle upper limit stress does not change. The developing trend of axial deformation and radial deformation is contrast to the result of residual deformation. （3） The deformation moduli of cycle loading or unloading progress are different and the deformation moduli of unloading progress are bigger than the value of loading progress. （4） The deformation moduli measured under altering confinement pressure are bigger than the deformation moduli measured under constant confinement pressure. Through experiments, the deformation character and rock elastic parameters of limestone under triaxial altering confinement pressure cycle exist divergence.