脆性岩石卸围压强度特性试验研究

岩样的承载能力由材料强度和围压共同确定，轴向压缩和卸围压二者都能导致岩样破坏，但由于应力路径不同，两种条件导致岩样的破坏过程并不相同。对取自位于雅砻江上的锦屏二级水电站辅助洞内的白山组大理岩进行了常规三轴试验和峰前、峰后卸围压试验，通过对试验曲线和岩样破坏特征的分析表明：无论是峰前还是峰后卸围压，岩样都表现出脆性破坏的特征，而岩样破坏表现出的脆性峰前卸围压比峰后卸围压更为强烈；岩样在加、卸载条件下的变形均随主应力差的增大而增大，但在相同的主应力差下，卸载产生的扩容量比加载的扩容量更大；峰前卸围压试验当围压卸到初始围压值的60 %左右时，岩样发生破坏；峰后卸围压试验当围压卸到初始围压值的80 %左右时，岩样发生破坏。结论对相关工程稳定性分析、设计和施工具有一定的指导意义和参考价值。

Experimental research on strength characteristic of brittle rock unloading confining pressure

The bearing capacity of rock sample is determined by material strength and confining pressure together. Both axial compression and unloading confining pressure can induce the failure of rock sample, but because of different stress paths, the failure processes under two conditions are different. The tests of conventional triaxial, pre-peak unloading confining pressure and post-peak unloading confining pressure are done to the Baishan marble which comes from access tunnel in Jinping Hydropower Station lying on Yalong River. The test curve and the rock sample failure characteristics indicate that rock samples are all showing brittle failure in pre-peak and post-peak unloading confining pressure tests; and the brittle characteristics in pre-peak test is more stronger than that in post-peak test. The deformations of rock sample in loading and unloading are increasing with the increase of principal stress difference; but dilatancy in unloading is bigger than that in loading under the same principal stress difference. Rock sample fails as confining pressure unloaded to about 60 % of initial confining pressure in pre-peak unloading confining pressure test; and as confining pressure unloaded to about 80 % of initial confining pressure in post-peak unloading confining pressure test, it fails. The conclusion can be for reference in internal correlative engineering stability analysis, design and construction.