饱水对煤层顶板砂岩单轴压缩破坏能量影响的分析

为研究饱水对砂岩力学参数和能量特征的影响,利用RMT-150B岩石力学系统对煤层顶板砂岩自然和饱水试样进行单轴压缩试验。试验结果表明:饱水对砂岩试样的强度和变形参数均有不同程度的影响,软化系数为0.79,弹性模量降幅为5.25%,变形模量降幅为5.92%;饱水后砂岩试样峰值前吸收能量、可释放弹性能和耗散能均有不同程度降低,吸收能量降幅36.8%,可释放弹性能降幅为34.4%,耗散能降幅为57.7%;饱水后砂岩储蓄能量的能力有较大减弱,脆性减弱,塑性明显增强;饱水砂岩试样压缩过程中积蓄可释放能难以使试样滑移破坏,仍需要吸收部分能量使试样逐步失稳破坏;饱水对砂岩试样压缩过程吸收能量、可释放能量比例关系的影响较小,而对耗散能比例关系的影响较大;自然状态下砂岩试样峰值前相同应变条件下吸收能量、可释放能均明显高于饱水试样对应能量值;深部巷道位置确定和支护设计时应充分考虑水对巷道围岩弱化的影响,对于完整坚硬围岩采用高压注水软化可有效防止冲击地压发生和减缓灾害程度。

On the Effect of Water-saturated State on Failure Energy of Sandstone from Coal Seam Roof subjected to Uniaxial Compression

In order to study the effect of water-saturated state on mechanical properties and energy mechanism of sandstone,uniaxial compression experiment for natural and water-saturated sandstone samples taken from coal seam roof was carried out by using RMT-150B rock mechanics system.Experimental results show that water-saturated state has effect on strength and deformation parameters of sandstone specimen in different degrees.The softening coefficient of sandstone is 0.79,the elastic modulus and deformation modulus decrease by 5.25％ and 5.92％,respectively.Compared with natural sample,the total absorbed energy,releasable elastic energy and dissipated energy of water saturated sample before strain-stress curve peak decrease by 36.8％,34.4％ and 57.7％,respectively.Compared with natural sandstone,the energy accumulation capacity of saturated sandstone decreases and saturated sandstone has obvious plastic characteristics and weak brittleness.The releasable elastic energy is difficult to make sliding failure of saturated sandstone in compression process;it still needs to absorb energy from outside to gradually make samples failure on post-peak stage.Water-saturated state has little influence on the ratio of the releasable elastic energy to total absorbed energy,while has a great effect on the ratio of the dissipated energy to the total absorbed energy.The total absorbed and releasable elastic energy of the natural sandstone before strain-stress curve peak are much larger than those of the saturated sandstone under same strain condition.The influence of water on roadway surrounding rock weakening should be fully considered in deep roadway position determination and support design.For the intact and hard surrounding rock,high pressure water injection can effectively prevent the occurrence of rock burst and reduce the degree of disaster.