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为了弄清深埋硬岩的加、卸荷破坏机制,系统开展了深埋大理岩的常规三轴试验、保持σ_1不变的卸围压试验和变σ_1的卸围压试验等。以裂纹体应变为主要分析变量,结合体应变、等效塑性应变等参量深入分析上述不同应力路径下硬岩的破坏过程。运用裂纹体应变-轴向应变曲线、等效塑性应变-轴向应变曲线和轴向应力-应变曲线来解释岩石破坏过程所产生的现象与规律。结果表明:在裂纹闭合阶段岩样裂纹闭合的变化程度(裂纹体应变改变的大小)可以反映岩石的初始损伤程度;裂纹闭合阶段对岩石弹性模量的计算有重要的影响,需要根据合适的阶段划分,消除裂纹闭合阶段对弹性模量计算的影响,进而得到较为准确的弹性模量;在卸围压点处岩石的可闭合程度突然增加,裂纹体应变-轴向应变曲线发生突变;岩石卸荷破坏过程中裂纹扩展存在滞后性。研究成果有助于进一步理解深埋硬岩的加、卸荷破坏过程和机制,为深埋隧洞的灾害防治提供理论依据。
In order to clarify the mechanism of loading and unloading of deep hard rock, the system conducts the conventional triaxial test of deep buried marble, maintains unloading confining pressure test with constant σ_1 and unloading confining pressure test with variable σ_1. Taking cracked body strain as the main analysis variable, combined with body strain, equivalent plastic strain and other parameters, the failure process of the hard rock under different stress paths was deeply analyzed. The phenomenon and regularity of rock failure process are explained by the crack body strain-axial strain curve, equivalent plastic strain-axial strain curve and axial stress-strain curve. The results show that the degree of change of crack closure (the change of crack strain) can reflect the initial damage degree of rock during the crack closure stage. The crack closure phase has an important influence on the rock elastic modulus calculation. Then the influence of crack closure phase on the calculation of elastic modulus is eliminated and a more accurate elastic modulus is obtained. At the point of unloading pressure, the closure degree of the rock suddenly increases and the strain-axial strain curve of the crack body changes suddenly. There is lag in the crack propagation during the failure process. The research results are helpful to further understand the process and mechanism of the loading and unloading damage of the deep hard rock and provide a theoretical basis for the prevention and control of the deep tunnel disaster.