层状盐岩中裂纹扩展规律的细观实验研究

 层状盐岩力学行为的研究是地下盐岩储库建设的科学基础。借助可以进行原位加载下实时观测的SEM实验系统，对载荷作用下层状盐岩开裂破坏时的裂纹扩展规律进行研究，并从能量耗散及释放的角度探讨层状盐岩破坏的细观机制。观察发现，层状盐岩中岩盐与泥岩夹杂的细观结构有着较大差异，从而影响着盐岩的宏观力学行为。层状盐岩中裂纹扩展路径一般不是沿着岩盐与夹杂的界面，而是在岩盐或夹杂中扩展。且当裂纹在泥岩夹杂中扩展时，能量耗散明显，形成不规则的裂纹，其分形维数大于1，并有可能出现分叉，此时盐岩承载能力较弱，外载做功还较小时就会导致破坏；当裂纹在岩盐中扩展时，伴随较多的弹性能快速释放，形成较平直的裂纹，其分形维数近似为1，并有可能出现较大张开，此时盐岩承载能力较强，吸收外载做功的能量较高。

MESO-EXPERIMENTAL INVESTIGATION ON CRACK EVOLUTION IN BEDDED SALT ROCK

Investigation of mechanical behavior of bedded salt rock is the scientific fundamental for constructing storage cavern in underground salt rocks. By means of an advanced testing system which can be used to observe real-time SEM images of samples under the condition of loading in situ，the evolution of cracks was investigated during bedded salt rock samples have being broken and the meso-mechanism is discussed based on the analysis of energy dissipation and energy release. It is observed that there exists large different between the meso-structure of rock salt and that of mud rock impurity in bedded salt rock，and such difference affect the micro mechanical behavior of bedded salt rock. Cracks never develop along the interface of rock salt and mud rock impurity，and they usually develop in rock salts or mud rock impurities. When cracks are developing in the mud rock impurity，energy dissipation plays an important role so that the path of cracks is irregular which fractal dimension is large than 1 and even branch out sometimes，and under this case the load-bearing capacity of bedded rock is weak so that it would rupture although the work of external load is still small. When cracks are developing in the rock salt，more elastic energy is released quickly so that the path of cracks is straight which fractal dimension is nearly equal to 1 and even open more large distance sometimes，and under this case the load-bearing capacity of bedded rock is strong so that it could absorb more energy due to the work of external load.