冻融循环作用下泥炭土强度劣化研究

Study on Strength Deterioration of Peat Soil in Freeze-Thaw Cycles

为研究泥炭土在高海拔季节温差作用下其力学特征变化规律,通过室内冻结和冻融下的抗剪强度试验,分析土体在冻结和融化过程中其强度变化规律,并建立冻融循环下泥炭土黏聚力拟合曲线。结果表明:降低冻结温度和延长冻结时间会增强土体抗剪强度,且冻结时间对强度影响更加显著;土体冻融过程中融化阶段对土体强度劣化作用大于冻结阶段的强化作用,含水率越低,这种劣化效应越大;随着冻融次数增加,土体黏聚力对含水率敏感程度降低,而内摩擦角对含水率敏感性增高;含水率为51%~63%是冻融作用和润滑作用对土体黏聚强度的控制阈值;冻融过程强度的劣化既受孔隙水相变的影响,也一定程度上受有机质含量的干扰。冻融次数、含水率与土体黏聚力的关系曲线被拟合,该曲线能够较好预测土体强度的劣化进程。

To study the mechanical characteristics of peat soil under the action of seasonal temperature differences at high altitudes,through the shear strength tests in freeze and freeze thawing in the laboratory,the strength variation law of soil during freeze-thaw was analyzed,and the fitting curve for cohesion of peat soil in freeze-thaw cycles was obtained.The results showed that reducing freeze temperatures and prolonging freeze times could increase shear strength of soil,and the freeze time had a more significant effect on the strength;in the process of freeze-thaw,the deterioration effect at the thaw stage on soil strength was greater than that at the freeze stage.The lower the water content was,the greater the deterioration effect was.With the increase in rounds of freeze-thaw cycles,the sensitivity of soil cohesion to the water content decreased,while the sensitivity of internal friction angle to the water content increased.The water content of 51%to 63%was the control threshold of freeze-thaw and lubrication for soil cohesive strength;the deterioration of freeze-thaw strength was not only affected by the phase change in pore water,but also affected by the organic matter content.The relation among the round of freeze-thaw cycles,the water content and the soil cohesion was fitted,which could better predict the deterioration of soil strength.