冻融循环对含砂粉土力学性质的影响

为了探究多年冻土区地表层的土体在冻融循环过程中力学性质的变化，通过对不同环境冷却温度、压实度、冻融循环次数、含水率和围压下的含砂粉土试样进行室内不固结不排水三轴试验，研究冻融循环后土体应力-应变关系曲线、破坏强度、弹性模量、抗剪强度参数的变化规律，然后借助正交试验的显著性分析理论，研究以上因素以及各因素间交互作用对破坏强度和弹性模量的影响程度.结果表明：含砂粉土的破坏强度和弹性模量随冻融循环次数增加，在围压300 kPa或冷却温度-5 ℃的情况下呈先增加后减小最后稳定的趋势，且在冻融循环3次后达到最大值；随冻融循环次数的增加，内摩擦角在冷却温度为-5 ℃的情况下逐渐减小并趋于稳定，在冷却温度为-10 ℃和-15 ℃的情况下先增加后减小最后趋于稳定；围压、含水率、压实度、冻融循环次数对破坏强度和弹性模量影响显著，冷却温度的影响较弱，压实度和含水率、冻融循环次数和围压的交互作用对破坏强度影响显著.综上分析得出，在研究冻融循环对土体力学性质的影响时应综合考虑各因素及其之间的交互作用.
To investigate mechanical properties of active layer in permafrost due to the freeze-thaw cycles, a series of the unconsolidated and undrained triaxial shear tests were conducted by considering the factors of different freezing temperatures, degree of compaction, numbers of freeze-thaw cycles, moisture content and confining pressures. The stress-strain curve, failure strength, elastic modulus and shear strength parameters of sandy silt were determined and analyzed, and significance analysis of the five factors and interactions among of them were carried out. Results show that with the increase of freeze-thaw cycles, the failure strength and elastic modulus, measured at the confining pressures of 300 kPa and at the freezing temperatures of -5 ℃, increase at the first three freeze-thaw cycles and then attain a stable status. Cohesion force decreases gradually and tends to be stable at the freezing temperatures of -5 ℃, and increase firstly and then drop, finally attain a stable status at the freezing temperatures of -10 ℃ and -15 ℃. All factors have a significant influence on the mechanical properties except freezing temperature. Interactions between degree of compaction and moisture content, confining pressure and number of freeze-thaw cycles exhibit a significant effect on failure strength. Significant analysis indicates that interactions of factors should be considered in the test design.