冻融对粉质黏土强度指标的影响

Effect of Freeze-Thaw on Strength Index of Silty Clay

依托同三高速公路扩建工程方正—哈尔滨段加宽一侧粉质黏土路基,采用室内三轴试验方法,研究了不同压实度、不同含水率下不同冻融次数后土体强度指标的变化规律。试验结果表明粉质黏土冻融后强度指标发生规律性变化:土的黏聚力损失随着冻融次数增多而增大,同一压实度下含水率高的土体黏聚力损失幅度较大;土的内摩擦角随着冻融次数的增多有逐渐增长的趋势,但增长幅度较小。运用Matlab对试验数据进行回归分析,建立了同一压实度下粉质黏土黏聚力、内摩擦角与含水率和冻融次数的回归方程。该方程能够直观模拟冻融对粉质黏土强度指标的影响规律,计算结果与实测结果吻合良好,可用于冻融后粉质黏土黏聚力和内摩擦角的计算。

Triaxial shear tests were applied to study the variation in strength index of soil mass under different degrees of compaction,moisture contents,and different numbers of freeze-thaw cycles based on the silty clay subgrade in the expansion project from Fangzheng to Harbin along Tongjiang-Sanya Highway.Results show that the strength indices change regularly after the silty clay was frozen and thawed.The loss of cohesion increases with increasing numbers of soil freeze-thaw cycles.The cohesion of soil with high moisture content loses more under the same degree of compaction.With increasing numbers of soil freeze-thaw cycles,the internal friction angle grows gradually,but the growth rate is smaller.A regression equation of silty clay expressing the relationships between cohesive force,internal friction angle and moisture content,number of freeze-thaw cycles were established under the same degree of compaction through regression analysis of the experimental data using Matlab software.This equation can directly simulate freeze-thaw effects on strength indices of silty clay,and the calculation results are in good agreement with experimental results.The equation can be applied to the calculation of internal friction angle and cohesion after silty clay is frozen and thawed.