黄土地区存在冻融灾害,冻融循环、冻结温度和冻结速率的研究对于冻融灾害工程预防有着重要的意义。在封闭环境下不同含水率土样分别进行0,-5,-10,-15,-20 ℃的冻结,随后15 ℃融化后测定黄土力学特性的变化规律,试验研究了试样经历不同最低冻结温度的单次冻融循环后的无侧限抗压强度、抗剪强度及压缩性等力学特性的变化规律。试验结果表明:在历经不同冻结温度的冻融作用后,不同含水率黄土的无侧限抗压强度均减小,冻结温度越低,无侧限抗压强度下降就越快;不同含水率土样的黏聚力也呈现出随冻结温度的降低而下降的趋势,黄土内摩擦角先减小后增加,变化幅度处于0°~2°;含水率为14%和26%黄土的压缩系数在-20 ℃冻结后的增幅都呈现>0.1 MPa^-1的增量,其余低温条件下的浮动变化很小,而含水率为18%和22%黄土的压缩系数随着冻结温度的下降而呈现出较均匀的波动变化,相邻负温情况下的波动值≤±0.1 MPa^-1。

Researching the freeze-thaw cycle, freezing temperature and freezing rate is of vital significance for engineering prevention of freezing-thawing hazard of loess. In this paper, the changes in unconfined compressive strength, shear strength, and compressibility of loess samples after a single freezing-thawing cycle at different freezing temperatures were studied. Samples of different moisture contents were frozen at 0, -5, -10, -15, -20 ℃ in a closed environment, respectively, and then heated at 15 ℃. Results showed that after freezing and thawing at different freezing temperatures, the unconfined compressive strength of loess with different water content decreased; and the lower the freezing temperature, the faster the unconfined compressive strength decreased. The cohesion of soil samples with different moisture contents also exhibited a tendency of decreasing with the drawdown of freezing temperature. The friction angle of loess decreased firstly and then increased within a range between 0° and 2°. For loess with 14% and 26% moisture content, the increment in compression coefficient was larger than 0.1 MPa^-1 under -20 ℃ freezing temperature, while under other low temperature conditions, the changes in compression coefficient were slight; whereas loess of 18% and 22% moisture content showed a more uniform fluctuation with the decrease of freezing temperature, with the fluctuation value in the case of adjacent negative temperature did not exceeding ±0.1 MPa^-1.