分级加卸载下深部巷道围岩蠕变特性试验研究

Experimental Study on Creep Properties of Surrounding Rock in Deep Roadway of Coalmine under Stepwise Loading and Unloading

采用分级增量循环加卸载方式,对湖南湘煤集团牛马司矿业公司水井头煤矿-300m东大巷二煤层底板粉砂岩进行了单轴蠕变特性试验,探讨了轴向蠕变和各蠕变阶段的非线性粘弹塑性变形特征。试验结果表明,当应力水平低于岩石的长期强度时,粉砂岩只发生衰减蠕变;瞬时塑性应变和粘塑应变随轴向应力的增大而增大,瞬时弹性模量随应力水平增大而增加,而变形模量随应力水平增大和时间的增长逐渐减小,直至趋于某一稳定值;随着应力水平增大,粘弹性应变、粘塑性应变和总蠕变均先减小然后增大,表明低应力下因岩石内部微裂纹不断压密产生应变硬化,高应力下因岩石材料性质不断劣化产生内部损伤发生应变软化。

By means of stepwise incremental cycling loading and unloading, the experiment was done on uniaxial creep properties of siltstone at the floor of coal seam II in east roadway beneath 300m of Shuijingtou coalmine of Niumasi Mining Company of Hunan Xiangmei Group. The prop- erties of the axial creep deformation and the nonlinear elastovisco-plastic deformation characteristics of siltstone in each creep stage were discussed. The test results show that the attenuation creep neous neous occurs when the stress level is lower than the long-term strength of siltstone. The instanta plastic strain and visto-plastic strain increase with the growth of axial stress. The instanta elastic modulus increases with the growth of stress level, while deformation modulus decrease gradually with the increase of stress level and time until it tends to be a certain stable val- ue. With the increase of stress level, visco-elastic strain,visco-plastic strain and the total creep all decrease firstly and then increase. This phenomenon indicates that strain hardening forms because of the continous compaction of microcrack inside the rock under low stress, and strain softening occurs because of the constant degradation of the material properties of the rock under high stress.