干湿循环作用下弱胶结砂岩声发射特征及其细观劣化机理

针对弱胶结砂岩遇水软化和泥化现象，采用饱水实验、QEMSCAN扫描电镜以及声发射试验，对不同干湿循环次数作用下弱胶结砂岩的物理力学性质及其细观结构特征变化进行了探讨。研究表明:弱胶结砂岩遇水软化宏观特性分为4类，其宏观特性的差异主要取决于弱胶结砂岩细观颗粒胶结方式、胶结物成分和含量相关等细观参数;弱胶结砂岩遇水软化细观特征，一方面在饱水过程中胶结物溶蚀逐渐减少、颗粒自身膨胀产生细粒碎屑，另一方面饱水过程中导致岩样内部次生孔隙率增大;随着干湿循环次数的增加AE事件计数率与能量释放率也不断的降低，主要是干湿循环次数增加，砂岩内部骨架颗粒与胶结物质均得到不同程度的软化，颗粒胶结性能变差，裂纹发展速度较缓，规模较小，释放的能量较小，因此，随着干湿循环作用增加砂岩破坏时出现较低的试件计数率和能量释放率，反映出干湿循环次数增加后应力扰动敏感性降低进而导致破坏程度降低，为进一步研究弱胶结砂岩变形破坏机理奠定基础。

Influence of wetting-drying cycles on acoustic emission characteristics and mi-crostructure deterioration of weak cementation stratum

The softening and argillation of weakly cemented sandstone by water are studied with saturation water experiment,QEMSCAN electron microscopy,and acoustic emission test,so as to explore the changes of the physical and mechanical properties as well as the microstructure characteristics of weakly cemented sandstone under the influences of dry and wet conditions which are imposed in cycles.The results show that the macroscopic characteristics of the softening of weakly cemented sandstone with water are divided into four types.The dif-ferences of such characteristics depend on the way how microscopic particles cement with each other and the mi-croscopic parameters relating to the composition and content of the cement.As of the microscopic features of the softening of the weakly cemented sandstone with water,on one hand,the corrosion of the cements decreases gradually during water saturation,and the self-inflation of the particles generates fine scraps and grains.On the other hand,during water saturation,the secondary porosity within the rock sample increases.With the increase of the number of dry and wet condition cycles,AE event count rate and energy release rate continue to decrease.The reason is that with the increase of the number of dry and wet cycles,the internal skeleton particles and cements within the sandstone are both softened to different extent,and the crack develops slower with smaller scale and less energy released.Therefore,with more cycles of dry and wet conditions,the damage of the sandstone features lower time count rate and energy release rate,while the severity of the damage towards the sandstone sample is also alleviated.