岩石孔洞试件变形破坏的电测法实验

Electrometric experimental study on the deformation and failure of the rock with borehole

剪切裂纹(breakout or spalling)是硬岩地下洞室开挖损伤区的主要破裂形式,对实际岩体工程的稳定性起到了控制作用.选取了粉砂岩圆孔试件进行了双向不等压加载,采用贴应变片的电测法作为监测手段,对剪切裂纹形成演化规律及进一步诱发的破坏形式进行了实验研究.得到了试件表面观测点应力演化规律,在此基础上分析了不等压条件下剪切裂纹的发生机理:不等压下脆性硬岩洞壁不容易破坏,但当加载到一定水平时,破坏很突然,并迅速诱发了"V"形区;孔壁附近发生的是剪切破坏,孔壁深处发生的是拉剪复合型的破坏.

＂Breakout or spalling＂ often occurs at the excavation damage zone of hardrock underground chamber, which controls the stability of rock body. Experiment of circular borehole sample of siltstone in hidireetional unequal pressure loading is conducted, and strain gauge is adopted to monitor the defo mation, then the ＂breakout and spalling＂ formation, evolution, and further destruction form are inves- tigated. By experimental studying the stress evolution curves of the observation point on the borehole specimen surface, the mechanism of ＂breakout or spalling＂ is analyzed. It showed that the brittle hardrock borehole wall is not easy to damage in bidirectional unequal pressure loading, but when the loading reach a particular level, the borehole wall form develop rapidly. It is found that shear failure mixed failure is deep inside the borehole wall. begin to damage suddenly and the breakout-＂ V＂ is near the borehole wall, while compression-shear