季节冻土区正融粉质黏土强度影响因素敏感性分析

针对季节冻土区路基填土春融时常处于强度不稳定的状态， 根据季节冻土特性选取冻结温度、 融化温度、 围压、 含水率4种影响因素， 对张家口季节冻土区粉质黏土进行了模拟正融土的常规三轴试验， 采用灰色关联分析法对试验结果进行分析， 给出了4种影响因素对强度的敏感性排序。结果表明： 含水率、 融化温度、 冻结温度的敏感性超过60%， 需要重点考虑。9%含水率时， 土样强度较高， 发生脆性破坏， 随着含水率的增大， 向延性破坏转变； 融化温度主要影响土体剪切过程中融化速度和排水固结的速度， 温度越低， 土样强度越高； 冻结温度通过改变土颗粒和冰晶体的胶结程度来影响强度， 冻结温度越低， 胶结作用越强， 但低于-10 ℃后， 强度增长缓慢； 围压越大， 土体强度越大， 不同围压影响下， 应力-应变曲线的形状和走势却大致相同， 分析结果可为季节冻土区实际工程提供一定的参考。

Sensitivity analysis of the influencing factors on strength of silty clay in seasonally frozen regions

In seasonal frozen areas， subgrade fill soil is often in the state of unstable state when spring thawing. In this paper， four influencing factors including freezing temperature， thawing temperature， confining pressure and moisture content were selected to conduct a triaxial test on the silty clay specimen from Zhangjiakou. The test results were analyzed by grey relational analysis method， and a sensitivity order of each factor to the strength was given. The results show that the sensitivity of moisture content， thawing temperature and frozen temperature is more than 60%， which should be considered importantly. When the moisture content is 9%， the strength of the specimen is high and brittle failure will occur. With the moisture content increase， the failure will change to ductile failure. Thawing temperature mainly affects the thawing rate and the rate of drainage consolidation in the shear process. The lower the temperature， the stronger the soil specimen； freezing temperature affects the strength by changing the degree of cementation between soil particles and ice crystals； the lower the freezing temperature， the stronger the cementation. However， below -10 ℃， the strength increases slowly. The strength of soil increases with the increase of confining pressure. Under the influence of different confining pressures， the shape and trend of stress-strain curves are almost the same. This analysis results will be useful for the practical projects in seasonal frozen areas.