基于直剪试验的金坛盐岩力学特性研究

 采用RMT–150C试验机对江苏金坛拟建储气库埋深段盐岩试样进行一系列直剪试验研究。将盐岩作为多晶聚合体考虑，深入分析试验过程中的剪切应力、剪切变形、剪胀以及破坏特性。试验结果表明：盐岩剪切破坏是一种延性破坏，盐岩剪切峰值对应的剪切位移一般为4～6 mm，个别试样可达7～8 mm，且整个剪切应力–剪切位移曲线都较平缓，剪切峰值不明显，这主要是由于局部位错交替导致的；得到盐岩抗剪强度参数c，? 值分别为3.16 MPa，44.7°；发现残余强度基本上与法向应力呈正比例关系，且残余应力较大，约为峰值应力的50%～80%，表明盐岩摩擦承载能力较强；盐岩剪胀终止发生在峰值应力之后、残余应力之前，且在较大法向应力作用下剪胀起始应力与剪胀终止应力接近；盐岩的剪切破坏位置不是一个面，而是一个破碎带，破碎带上下一定范围内有不同程度损伤；表面局部有明显擦痕，类似于摩擦学的“犁沟效应”，有利于提高其抗剪能力。试验研究成果对深入理解金坛盐岩破坏机制及地下盐岩储气库稳定性研究具有一定的参考价值。

STUDY OF MECHANICAL PROPERTIES OF JINTAN SALT ROCK BASED ON DIRECT SHEAR TESTS

A series of direct shear tests are carried out by using testing machine RMT–150C to investigate the characteristics of salt rock in Jintan gas storage. The shear stress of dilatancy and failure characteristics are deeply analyzed by considering the salt rock as a kind of polycrystalline polymer. The results show that shear failure of salt rock is ductile failure，and the shear displacement corresponding to ultimate shear strength is generally 4–6 mm；the shear displacements of several specimens even reach 7–8 mm. The whole curves are relatively flater，the shear strength is not very clear，which is mainly due to the grain dislocation alternatively. Finally，the shear strength parameters c and   is 3.16 MPa，44.7°，respectively. The residual strength and the normal stress is basically a positive correlation，and the residual strength is much higher，about 50%–80% of shear strength which indicates a strong bearing loading capacity for salt rock only by friction. Salt rock shear dilatancy occurs before the residual stress and after peak stress，and the initial stress of shear dilatancy is close to the stress for termination under much higher normal stress. Shear failure section of salt rock is not a plane but a fracture zone. It can be seen that part of the section has clear scrape which is similar to the“plow effect”. This will help to improve the shear capacity of salt rock. The results also have great reference for understanding the mechanism of Jintan salt rock and investigating the stability of underground gas storage.