论文部分内容阅读
为明确冻结过程中环境温度对土体冻融循环效应的影响规律,以青藏高原粉质黏土为对象,首先选择冻结环境温度(-5℃、-10℃、-15℃、-20℃、-25℃、-30℃)和冻融循环次数(0、1、3、6、9、12、15)为变量进行了一系列冻融循环试验,然后,以围压(50、100、150kPa)为变量,对经历冻融循环试验后的试样进行三轴压缩试验。研究结果表明:冻结环境温度会显著影响土体经历冻融循环后的物理力学性质。冻融循环后试样的破环强度整体上有所减小,并随冻结环境温度的降低呈先减小、后增大的变化规律,-15℃时破坏强度达谷值。虽然土体冻结后的表观体积增大,但膨胀变形分量和收缩变形分量在冻结过程中同时存在,而且随着环境温度的降低,冻胀先于冻缩达到极限状态,因此表观体积呈先增大、后减小的变化规律,相应地破坏强度呈相反的变化规律。此外,随着冻融循环次数的增加,破坏强度呈先减小、后逐渐稳定的变化规律。同时,冻结环境温度越低,破坏强度达到稳定值所需的冻融循环次数越少。试样冻结过程中的水分迁移速率和迁移量随环境温度的降低而减小,水分迁移对土体结构的影响也随之减小。抗剪强度指标表现为与破坏强度一致的冻融循环效应,其中内摩擦角对冻结环境温度变化的响应程度大于黏聚力的影响程度。
In order to clarify the effect of ambient temperature on freezing and thawing cycles of soils, aiming at the silty clay in the Qinghai-Tibet Plateau, the first choice of freezing environment temperature (-5 ℃, -10 ℃, -15 ℃, -20 ℃, - 25 ℃, -30 ℃) and freeze-thaw cycles (0, 1, 3, 6, 9, 12 and 15) were used as variables to conduct a series of freeze- thaw cycles. As a variable, subjected to a triaxial compression test on a sample subjected to a freeze-thaw cycle test. The results show that the freezing environment temperature will significantly affect the physical and mechanical properties of the soil after the freeze-thaw cycles. After the freeze-thaw cycle, the breaking strength of the sample decreases as a whole, and decreases with the decrease of the freezing ambient temperature first and then increases, and the breaking strength reaches the valley value at -15 ℃. Although the apparent volume of the soil increases after freezing, the deformation components and shrinkage deformation components coexist in the freezing process, and as the ambient temperature decreases, the frost heave reaches the limit state before the freezing and shrinking. Therefore, the apparent volume First increase, then decrease the law of change, corresponding to the destruction of the opposite trend of change. In addition, with the increase in the number of freeze-thaw cycles, the failure strength first decreases and then gradually changes steadily. In the meantime, the lower the freezing ambient temperature, the less the number of freeze-thaw cycles required for the breaking strength to reach a steady value. The moisture migration rate and migration amount decreased with the decrease of ambient temperature during the sample freezing process, and the influence of water migration on the soil structure also decreased. The shear strength index shows the freeze-thaw cycle effect consistent with the failure strength. The response of the internal friction angle to the temperature change in the freezing environment is greater than that of the cohesion.