冻融及含水率对压实黏质土力学性质的影响

针对自然环境因素对季冻区路基强度与稳定性的影响，以京哈高速公路四平-长春段沿线的黏质土为研究对象，对不同含水率的土样进行0～16次冻融循环试验。通过室内三轴试验，分析了冻融次数和含水率对压实黏质土试样力学特性的影响规律，并探讨了其影响机制。研究结果表明，当试样的含水率小于最佳含水率时，随着冻融次数和含水率的增加，压实黏质土的应力-应变曲线由应变软化型向应变硬化型转变，试样的破坏形式逐渐由脆性破坏转为塑性破坏；压实黏质土的极限强度、弹性模量和黏聚力整体上均随冻融次数的增加而呈衰减趋势，内摩擦角与冻融次数的关系并无规律可循，但各个力学参数均在经历8次冻融循环后基本趋于稳定；含水率对压实黏质土的力学性质影响显著，极限强度、弹性模量、黏聚力和内摩擦角均随含水率的增加大幅减小。综合考虑冻融循环和含水率对压实黏质土力学性质的影响规律，建议季冻区路基应做好排水工作以降低路基含水率水平，并将经历8次冻融循环后的力学指标作为工程设计参考值。

Effect of freeze-thaw and water content on mechanical properties of compacted clayey soil

In view of the effect of environmental factor on the strength and stability of subgrade, the clayey soil taken from Siping- Changchun section of Beijing-Harbin expressway was investigated，and its variations of mechanical properties affected by freeze-thaw cycles and water content were thoroughly studied and analyzed in laboratory tests. The influence mechanism was also discussed. The test soil samples with different water contents went through 0 to 16 freeze-thaw cycles, and then the triaxial compression tests were carried out indoor. Results show that with the increasing of freeze-thaw cycles and water contents, the stress-strain curve of the compacted clayey soil changes from strain-softening to strain-hardening when the water content is less than the optimum water content, and the failure mode of the test sample gradually changes from brittle failure form to plastic failure form. The ultimate strength, elastic modulus and cohesion all decrease with the increasing of freeze-thaw cycles, while there is no obvious relationship between the internal friction angle and the freeze-thaw cycle. However, the aforementioned mechanical parameters of the compacted clayey soil all tend to stabilize after 8 freeze-thaw cycles. In summary, the effect of water content on mechanical properties of compacted clayey soil is significant. Ultimate strength, elastic modulus, cohesion and internal friction angle all decrease drastically with the increasing of water content. Based on the consideration of the effect of freeze-thaw cycles and water contents on mechanical properties of compacted clayey soil, the drainage work of subgrade in the seasonal frozen area should be well conducted to keep the subgrade in a lower level of water content, and the engineering design values of mechanical parameters should be those of the soil that undergoes no less than 8 freeze-thaw cycles.