寒区渠道粉土质砂换填料力学特性试验研究

Experimental study on mechanical properties of silty sand as a filling material for canals in cold regions

膨胀性渠基土性质受外部环境影响易发生劣化,由此造成膨胀土渠道边坡失稳破坏。为解决这一难题,人们采用粉土质砂对膨胀性渠基土进行换填。本文开展湿干循环、冻融循环及湿干−冻融耦合循环下粉土质砂换填料三轴剪切试验,研究粉土质砂换填料的应力−应变关系、弹性模量、破坏强度和抗剪强度指标的变化特征,对比分析粉土质砂换填料与膨胀泥岩的力学特性,从颗粒级配的角度揭示粉土质砂换填料强度演化特征的形成机理。研究结果表明:湿干循环、冻融循环和湿干−冻融耦合循环过程使得粉土质砂换填料的力学性能指标出现一定程度的衰减,其衰减幅度为0.3%~10.0%,显著低于膨胀性渠基土的最大衰减幅度(约40%);相较于膨胀性渠基土,寒区复杂环境下粉土质砂换填料的力学性质更加稳定;粉土质砂换填料的颗粒级配受湿干循环、冻融循环和湿干−冻融耦合循环的影响程度较低,可见复杂环境下粉土质砂换填料的内部结构较稳定。

The properties of expansive soil are easy to deteriorate when expansive soil is exposed to external environment,resulting in the instability of expansive soil canal slope.In order to solve this problem,the silty sand was used to replace the shallow expansive soil of canals.Triaxial shear tests on silty sand subjected to wet−dry,freeze−thaw and coupled wet−dry−freeze−thaw cycles were conducted.The characteristics of stress−strain relationships,elastic modulus,failure strength and shear strength indexes were described and the mechanical properties of silty sand and expansive soil were compared.The formation mechanism of strength evolution characteristics of silty sand was revealed from the perspective of particle size distribution.The results show that the wet−dry,freeze−thaw and coupled wet−dry−freeze−thaw cycles make the mechanical property indexes of silty sand show a downward trend,and the attenuation range is 0.3%−10.0%.It is significantly lower than the attenuation range of expansive soil,which is approximately 40%.Compared with the expansive soil,the mechanical properties of silty sand are more stable when silty sand is exposed to complex environment in cold regions.The influence of wet−dry,freeze−thaw and coupled wet−dry−freeze−thaw cycles on particle size distribution of silty sand is low,which indicates that the internal structure of silty sand is relatively stable in complex environment.