盐岩力学特性应变率效应的试验研究

 以层状盐岩体矿床中的NaCl岩盐与无水芒硝盐岩为研究对象，在实验室内进行10－5～10－3 s－1范围内单轴压缩强度与变形特性的应变率效应研究。研究结果表明：在上述应变率范围内，NaCl岩盐与无水芒硝盐岩的单轴抗压强度与弹性模量基本不随加载应变速率而变化；同一应变速率条件下，无水芒硝盐岩强度略高于NaCl岩盐；两类盐岩的泊松比均随加载应变速率的增大而减小；随加载应变速率的增大，试件在峰值应力点处的应变减小，其变形模量与加载应变速率呈对数关系；试件破裂方式不随加载应变速率而变，NaCl岩盐试件破裂为柱状劈裂或楔型剪切，而无水芒硝盐岩则表现为单斜剪切。对扩容应力与极限强度之比统计结果表明，盐岩扩容应力与极限强度之比(平均值)为87.3%～91.0%，表明盐岩在扩容之前均具有很强的变形能力。由试验结果可知，在其他安全稳定条件满足的前提下，盐岩溶腔储气库运营中、腔壁应变率在10－5～10－3 s－1范围之内，可以保证储气库腔体的安全稳定运营。

TEST STUDY OF STRAIN RATE EFFECTS ON MECHANICAL PERFORMANCES OF SALT ROCK

Halite and thenardite,which are the main constitutes in bedded salt rock deposits,are chosen as the experimental samples. The uniaxial compression behaviors of the samples are recorded and analyzed with loading strain rates increasing from 10~(-5) s~(-1) to 10~(-3) s~(-1). It is found that the ultimate strength and the elastic modulus of the two lithologies hardly change with loading strain rate in the test scale. The uniaxial compressive strength of thenardite is larger than that of halite when they are loaded with the same strain rate. Opposite to the trend of the elastic modulus,the Poisson's ratios of the two lithologies decrease with strain rate for the halite and thenardite specimens. Similarly,the strains of the test specimens at the point of peak strength decrease with loading strain rate. A logarithmic relationship between deformation modulus and loading strain rate is also established with the test results. During the experiments,it is found that all the halite specimens are broken in the type of brittle tensile fracture around the specimen column face,while single shear failure along an inclined plane in the specimens is the characteristic of thenardite breakage. The damage characteristics of the halite and thenardite hardly change with the loading strain rate. Stress ratio at the point of the onset of volumetric increase to the ultimate compressive strength of the tested specimens is also calculated and analyzed;and an average value of 87.3%-91.0% of the ratio is recorded,which is obviously larger than those of general rocks. The large ratio demonstrates that salt rocks possess large deformation capacity before volumetric increase occurs during compression. It is concluded that a salt cavern wall of strain rate between 10~(-5)-10~(-3) s~(-1) during salt cavern storage operations can guarantee the safety and stability of the cavern,while other operational demands are satisfied.