循环载荷下干燥及饱和砂岩的变形及声发射特征

对取自陕西榆横矿区小纪汗煤矿顶板砂岩的干燥和饱和试件进行单轴循环加卸载试验及声发射监测,分析了不同含水状态岩石的强度以及变形特征、声发射特征和加卸载响应比变化情况.结果表明,水对上述性质具有显著影响:饱和试件强度和滞回环数量均低于干燥试件,压密阶段轴向应变比干燥试件增加18.9%,峰值强度前轴向应变比干燥试件降低17.4%,干燥和饱和试件在循环加载过程中弹性模量均有增大趋势;干燥试件在整个加卸载过程中声发射能量累积为3.87×10-11J,饱和试件声发射能量累积为2.58×10-11J,仅为干燥试件的66.67%;干燥和饱和试件的加卸载响应比呈现类似的变化规律,但饱和试件的加卸载响应比峰值特征时间比干燥试件短,宏观裂纹形成得更早.

Deformation and Acoustic Emission Characteristics of Dry and Saturated Sand Under Cyclic Loading and Unloading Process

Uniaxial cyclic loading/unloading experiments were conducted on dry and saturated sandstones from Xiaojihan coal mine in Shaanxi province to study the deformation and strength characteristics， acoustic emission (AE) and load/unload response ration (LURR) in the failure process of sandstones. The results show that water has a significant influence on the properties mentioned above. The compressive strength and plastic hysteresis loops number of water-saturated specimens are less than that of dry specimens， and the axial strain in the compaction stage of water-saturated specimens is 18.9% larger than that of dry specimens， but the axial strain prior to peak strength of water-saturated specimens is 17.4% less than that of dry specimens. The elastic moduli of dry and saturated specimens both tend to increase during the cyclic loading/unloading process. AE cumulative energy of dry and saturated specimens is 3.87×10^-11J and 2.58×10^-11J respectively， and the latter is reduced by 33.3%. Furthermore， the LURR of dry and saturated specimens shows similar changing laws， but the characteristic peak time of saturated specimens appears earlier， which means the macroscopic crack generates earlier in saturated specimens.