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针对岩石传统直接拉伸试验方法面临的偏心受拉和应力集中两大难题,提出了一种新型直接拉伸试验方法:应用水刀切割将岩石加工成与金属标准拉伸试样尺寸一致的试样,然后用夹具连接在试验机上直接拉伸。2种砂岩试验结果表明,岩样为典型的脆性拉断破坏;单轴抗压强度为单轴抗拉强度的25~30倍,压缩弹性模量为拉伸弹性模量的5~8倍。通过对拉压强度试验结果的分析发现,经过拉伸截断修正的莫尔库仑准则更能合理地描述岩石在拉压状态下的巨大强度差异。
Aiming at two major problems of eccentric tensile test and stress concentration in traditional direct tensile test of rock, a new direct tensile test method is proposed: the test of processing rock to the same size as that of metal standard tensile test Like, and then use the fixture connected to the test machine directly stretched. The results of the two kinds of sandstone tests show that the rock samples are typical brittle fracture failure; the uniaxial compressive strength is 25 to 30 times of the uniaxial tensile strength, and the compressive elastic modulus is 5 to 8 times of the tensile elastic modulus. Through the analysis of tensile and compression strength test results, it is found that the modified Morton-Coulomb criterion after tensile truncation can more reasonably describe the great strength difference of rock under tension and compression conditions.