软黏土带压冻融循环下不固结力学特性试验研究

Experimental study on unconsolidated mechanical properties of soft clay under freeze-thaw cycles with confining pressure

人工冻结法和季节性冻土地区土体通常在一定围压下经历冻融循环作用。受到冻融围压和不排水条件影响,融化后土体残存超孔压,并非完全固结状态,开展此工况下土体不排水力学性能研究具有重要工程和科学意义。通过自主改进的温控三轴仪,对重塑软黏土开展冻融后未完全固结不排水三轴剪切和微观试验,分析了冻融围压、次数和冻结温度对冻融后软黏土力学特性影响。结果表明:与零围压相比,带围压冻融后土体中絮凝结构和孔隙数量增大,加剧了冻融对土体强度和模量的弱化作用;随着冻结温度降低和冻融次数增大,土体力学性能弱化效应越明显。

The artificial freezing method and the soil in seasonally frozen soil areas usually undergo freeze-thaw cycles under a certain confining pressure.Affected by the freeze-thaw confining pressure and undrained conditions,the residual excess pore pressure of the melted soil results in that the soil is not in a fully consolidated state.Therefore,conducting researches on the undrained mechanical properties of soil under this condition is of great engineering and scientific significance.In this study,the undrained triaxial shear tests and microscopic scanning tests on the remolded muddy clay after freeze-thaw cycles using the self-developed temperature controlled triaxial apparatus are conducted.The effects of freeze-thaw confine pressure,the freeze-thaw cycles and freezing temperature on the mechanical properties of post-freezing and thawing silty clay are analyzed.Compared with that without no confining pressure,the number of flocculation structures and pores in the soil increases after freeze-thaw under confining pressure,thus the weaking effects of freeze-thaw cycles on the strength and modulus of soil are accelerated.As the freezing temperature decreases and the number of freeze-thaw cycles increases,the weakening effects of muddy clay become more obvious.