冻融循环对软土力学性质的影响分析

为探究冻融循环过程中软土的冻胀融沉规律、力学性质及力学参数特性等,对松花江避暑城战备路工程软土试样进行室内冻融循环试验。通过改变冻融循环次数测定试件体积膨胀与收缩率,并通过室内三轴试验,测得不同冻融循环次数及不同围压条件下的软土抗剪强度。宏观试验数据及微观分析结果表明:软土在冻胀融沉过程中体积变化率随冻融循环次数的增加逐渐增大,6次冻融循环后,土体冻胀率、收缩率基本保持不变,冻胀融沉现象趋于稳定;随着冻融循环次数的增加,软土抗剪强度先增大后减小,且在第6次冻融循环作用下达到最小值,在后续6~15次冻融循环过程中,抗剪强度逐渐增大,且接近冻融循环作用之前的抗剪强度值;冻融循环作用对软土黏聚力c有显著影响,而与内摩擦角φ无相关性。

Effect of Cyclic Freezing and Thawing on Physical and Mechanical Properties of Soft Soil

Indoor cyclic freeze-thaw test was carried out to examine the law of heave and settlement of soft soil under cyclic freezing and thawing as well as the changes in mechanical properties. The expansion and shrinkage of specimen’s volume were measured by changing the number of freeze-thaw cycle; in the meantime, the shear strength of soft soil under different freeze-thaw cycles and varying confining pressure were measured by indoor triaxial test. Test data and microscopic analysis revealed that the rate of volume change augmented with the proceeding of cyclic freezing and thawing; after six freeze-thaw cycles, the heaving rate and settlement rate of soft soil maintained unchanged in general. With the proceeding of cyclic freezing and thawing, the shear strength of soft soil increased first and then decreased, reaching the minimum at the sixth cycle; but finally recovered in the subsequent 6-15 cycles, approa-ching to the value before freezing and thawing. Moreover, freeze-thaw cycle had significant effect on the cohesion of soft clay, but had no correlation with internal friction angle φ.