冻融及细粒含量对粗粒土力学性质影响的试验研究

Influences of freeze-thaw and fines content on mechanical properties of coarse-grained soil

以粗粒土填料在冻土地区铁路路基中的应用和推广为研究背景,针对冻融作用及细粒含量对粗粒土填筑路基稳定性的影响,通过室内三轴试验深入研究和分析了冻融次数、细粒含量以及围压对粗粒土试样强度特性的影响规律。研究结果表明,随着细粒含量的增加,粗粒土的应力应变曲线由冻融前的应变软化现象过渡到冻融后的应变硬化现象;同时,随着细粒含量的增加,未经历冻融时,细粒土的黏结性有效地提高了粗粒土的剪切强度,而经历冻融后,细粒土的冻胀性反而削弱了粗粒土的剪切强度;粗粒土的剪切强度和抗剪强度指标随冻融次数的增加而减小并在经历6次冻融后达到稳定状态;围压的"围箍"作用有效地提高了粗粒土的抗剪强度;通过讨论和分析,建议冻土区铁路路基粗粒土填料的合理细粒含量为5%,并将粗粒土填料经历6次冻融后的力学指标作为工程设计值。

For the promotion and application of coarse-grained soil fillings in the railway subgrade in frozen regions, the shear strength properties of coarse-grained soil with fines content under freeze-thaw cycles are directly related to the subgrade stability. The influencing rules of freeze-thaw cycles, fines content and confining pressure on the shear strength properties of coarse-grained soil are therefore thoroughly studied and analyzed in laboratory tests. The results show that with the increasing increment of fines content, the stress-strain curve of coarse-grained soil changes from strain-softening before freeze-thaw cycles to strain-hardening after freeze-thaw cycles. With the increasing of fines content, the cohesion function of fines effectively enhances the shear strength of coarse-grained soil before freeze-thaw cycles, but the frost heave properties of fines decrease the shear strength of coarse-grained soil after freeze-thaw cycles. The shear strength indexes of coarse-grained soil decrease and then are steady after 6 freeze-thaw cycles. The confining pressure effectively enhances the shear strength of coarse-grained soil. Finally, the reasonable fines content of 5% is recommended for the railway subgrade coarse-grained soil fillings in frozen regions, and the mechanical indexes of the 6th freeze-thaw cycle are suggested for the engineering design values.