冻融循环条件下淤泥黏土力学特性试验研究

Experimental Study on Mechanical Properties of Silt Clay under Freeze-thaw Cycles

为研究冻结温度及冻融循环次数对冻结作用下黏土强度的影响,对福州富水地层黏土进行不同温度和不同冻融循环次数下的力学试验,研究其单轴瞬时抗压强度及蠕变规律。结果表明,随着冻结温度的降低,冻土单轴抗压强度逐渐增大,增加幅度逐渐减小,最大达6.56 MPa;随着冻融循环次数的增加,冻土单轴抗压强度逐渐减小,且减少幅度也逐渐减小,最小达1.30 MPa;加载应力水平较低时,冻土的蠕变速率较小,主要为衰减阶段及稳定阶段,加载应力水平较高时,冻土的蠕变速率较大,出现加速蠕变阶段;多次冻融循环后,对单轴抗压强度及蠕变曲线形状影响逐渐减小;未做冻融循环试样在较高蠕变系数时土体基本发生塑性变化,曲线呈硬化型,多次冻融循环后或在较低蠕变系数时,曲线呈软化型。

In order to study the influence of freezing temperature and freezing-thawing cycles on the strength of clay under freezing action,the mechanical tests of Fuzhou water-rich clay under different temperatures and freezing-thawing cycles are carried out to study the uniaxial instantaneous compressive strength and creep law.The results show that,(a)with the decrease of freezing temperature,the uniaxial compressive strength gradually increases and its maximum is 6.56 MPa,but the increments gradually decreases;(b)with the increase of freeze-thaw cycle times,the uniaxial compressive strength gradually decreases and its minimum is 1.30 MPa,but the reduction also gradually decreases;(c)when the loading stress level is lower,the creep rate of frozen soil is small,mainly in the attenuation stage and the stability stage,and when the loading stress level is higher,the creep rate of frozen soil is large,and the accelerated creep stage appears;(d)after the actions of a large number of freeze-thaw cycles,the influences on the uniaxial compressive strength and the shape of the creep curve are gradually reduced;and(e)the plastic change of the soil mass is basically occurred at higher creep coefficient when the specimen is not subjected to freeze-thaw cycles,the curve is of hardening type,and after repeated freeze-thaw cycles or at lower creep coefficient,the curve shows a softening type.