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为探讨寒区边坡工程岩体受冻融循环和开挖卸荷双重作用的影响规律,对经历不同冻融循环次数的砂岩进行单轴、三轴压缩及峰前卸围压3种力学试验,重点研究冻融循环后砂岩在卸荷应力路径下的力学性能和破坏特征。试验结果表明:(1)冻融循环次数增加导致岩样峰值强度和弹性模量逐渐减小。(2)相同围压降低量下,岩样径向应变与体应变变化较大,轴向应变变化相对较小。(3)冻融损伤越大,径向应变和体应变对围压降低越敏感。(4)岩样变形模量在卸围压过程中逐渐降低,冻融循环次数越高降低速率越小,且初始变形模量越低。(5)泊松比在卸围压过程中逐渐增大,冻融循环次数越高增速越低,泊松比增长初期与体应变大致呈线性关系。(6)不同冻融循环次数下岩样单轴压缩破坏模式均为劈裂破坏;常规三轴压缩破坏模式均为剪切破坏,剪切带大致沿端面对角开展,并伴随局部岩块掉落;峰前卸围压破坏模式为介于单轴和常规三轴间的混合模式。
In order to investigate the influence law of rock mass affected by the freeze-thaw cycles and excavation unloading in the cold area, three kinds of mechanical tests were carried out on uniaxial and triaxial compression and pre-peak unloading confining pressure of sandstone subjected to different freeze-thaw cycles , Focusing on the mechanical properties and failure characteristics of sandstone under unloading stress path after freeze-thaw cycles. The experimental results show that: (1) The increase of the number of freeze-thaw cycles leads to the gradual decrease of the peak strength and elastic modulus of rock samples. (2) Under the same confining pressure reduction, the radial strain and bulk strain of rock specimen change greatly, and the axial strain change is relatively small. (3) The greater the freeze-thaw damage, the more sensitive the radial strain and body strain to the confining pressure decrease. (4) Deformation modulus of rock samples decreases gradually during unloading confining pressure. The higher the number of freeze-thaw cycles, the lower the rate of decrease and the lower the initial deformation modulus. (5) The Poisson’s ratio increases gradually during unloading confining pressure. The higher the number of freeze-thaw cycles, the lower the growth rate, and the initial Poisson’s ratio increase is roughly linear with body strain. (6) The uniaxial compression failure modes of rock specimens under different freeze-thaw cycles are all splitting failure. The conventional triaxial compression failure modes are all shear failure. The shear bands are generally diagonally along the end face and accompany the local rock mass Drop; Pre-peak unloading pressure failure mode is between the single-axis and conventional three-axis mixed mode.