细粒含量对冻结粉质黏土力学特性的影响

Effect of fine particle content on mechanical properties of frozen silty clay

季节冻土力学性能对工程影响显著,季节冻土中细粒含量是其力学性质的重要参数。为研究细粒含量对季节冻土强度的影响,通过冻土三轴试验,研究了不同细粒含量(40%、45%、50%、60%、70%)、不同冻结温度(-5℃、-10℃、-15℃)、不同围压(50 kPa、80 kPa、120 kPa)下冻结粉质黏土的力学性质。结果表明:试样的三轴应力-应变曲线均为软化型。同一细粒含量下,随着冻结负温的降低,土样峰值强度逐渐增大,其中-10~-5℃增长比-15~-10℃更加剧烈。随细粒含量的增加,土体脆性指数分布呈现抛物线形,土样黏聚力呈现上升趋势,而土样内摩擦角减小。同时,采用测温法得出了各细粒含量下未冻水含量分布,建立了冻土黏聚力在不同负温下随细粒含量变化的计算模型,能较好地预估任意冻结负温及任意细粒含量下冻土黏聚力。

The mechanical properties of seasonal permafrost have a significant impact on engineering,and the fines content in seasonal permafrost is an important parameter of its mechanical properties.To study the effect of fines content on the strength of seasonal frozen soil,the mechanical properties of frozen chalky clay at different fines contents(40%,45%,50%,60%,70%),different freezing temperatures(-5℃,-10℃,-15℃),and different surrounding pressures(50 kPa,80 kPa,120 kPa)were investigated by triaxial tests on frozen soil.The results show that the triaxial stress-strain curves of the specimens are all softening type.At the same fines con⁃tent,the peak strength of the soil samples gradually increased with the decrease of the negative freezing tempera⁃ture,where the increase was more drastic at-10~-5℃than at-15~-10℃.With the increase of fines content,the distribution of soil brittleness index showed a parabolic shape,the cohesion of soil samples showed an in⁃creasing trend,while the internal friction angle of soil samples decreased.At the same time,the distribution of unfrozen water content at each fines content was obtained by thermometric method,and the calculation model of the change of permafrost cohesion with fines content at different negative temperatures was established,which can better predict the permafrost cohesion at any negative freezing temperature and any fines content.