Abstract red sandstone was tested in the freeze-thaw cycle under open and saturated conditions, and the mechanical properties of samples after different freeze-thaw cycles (0, 5, 10, 20, and 40 freeze-thaw cycles) were tested under the four kinds of confining pressures (0 MPa, 2 MPa, 4 MPa, 6 MPa). The whole process characteristics of deformation and failure of red sandstone were analyzed, and the effects of freeze-thaw cycles and confining pressure on red sandstone mechanical properties were studied. According to the characteristics of rock material non-uniformity and randomness, the effect of freeze-thaw and load coupling effect on the total damage was quantitatively expressed, and established a damage model can reflect the whole process of rock deformation. The theoretical expression of model parameters were derived by using the multivariate function to obtain total differential method, and the damage mechanical properties of rock were analyzed. The results has shown that: With the increase of the freeze-thaw cycles and confining pressure, the compressibility of rock is continuously enhanced, the peak strain is gradually increasing, the plastic yielding section is becoming more and more obvious, the post-peak stress reduction rate slows down, and the failure mode is transformed from brittleness to ductility. Meanwhile, the elastic modulus, peak stress and residual strength increase with the increase of confining pressure, and decrease with the increase of freeze-thaw cycles. The damage model reflects the process of deformation and failure of frozen-thawed rock under the action of load, especially the characteristics of post-peak strain softening and residual strength. The rock total damage evolution path reflects that the meso-mechanical response was consistent with the macro-deformation and failure characteristics, and the nonlinear influence characteristics of freeze-thaw and load on the rock total damage propagation are described. Furtherly, the deformation failure of rock is revealed by the mechanical damage mechanism.

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冻融循环和围压作用下岩石力学特性及损伤模型研究

摘要 对红砂岩进行了开放和饱和条件下的冻融循环试验，测试了不同冻融循环（0、5、10、20和40次冻融循环）后样品在四种不同条件下的力学性能。各种围压（0 MPa、2 MPa、4 MPa、6 MPa）。分析了红砂岩变形破坏的全过程特征，研究了冻融循环和围压对红砂岩力学性能的影响。根据岩石材料的非均匀性和随机性特点，定量表达了冻融和载荷耦合效应对总损伤的影响，建立了能够反映岩石变形全过程的损伤模型。采用多元函数求全微分法，推导出模型参数的理论表达式，分析岩石的损伤力学特性。结果表明：随着冻融循环和围压的增加，岩石的压缩性不断增强，峰值应变逐渐增大，塑性屈服截面越来越明显，峰值后应力逐渐增大。还原速度减慢，破坏模式由脆性转变为延性。同时，弹性模量、峰值应力和残余强度随着围压的增加而增加，随着冻融循环次数的增加而减少。损伤模型反映了冻融岩石在荷载作用下的变形破坏过程，尤其是峰后应变软化和残余强度的特性。岩石总损伤演化路径反映细观力学响应与宏观变形破坏特征一致，描述了冻融和载荷对岩石总损伤扩展的非线性影响特征。此外，岩石的变形破坏是通过机械损伤机制来揭示的。