冻融循环作用下伊犁盐渍化黄土力学特性

Mechanical properties of Ili salinized loess under freeze-thaw conditions

为研究冻融循环次数、围压和含盐量等因素对伊犁盐渍化黄土力学特性的影响,开展室内冻融循环作用下含盐黄土的三轴试验,分析盐渍化黄土在冻融和盐蚀作用后的劣化机制,提出盐渍化黄土的强度劣化公式和本构模型。结果表明:在冻融循环作用下,盐分的增多使应力-应变曲线由软化型转向硬化型;当含盐量较高时,黄土的抗剪强度随着冻融循环次数的增多迅速衰减。黏聚力与冻融循环次数呈指数关系;内摩擦角随冻融循环次数的增加先增大后减小、随含盐量的增大而减小。建立冻融作用下黏聚力的劣化模型,该模型能预测不同含盐量试件的黏聚力劣化特性;冻融作用对黏聚力衰减的权重大于盐蚀作用。提出考虑多因素作用下修正的Duncan-Chang模型,该模型能更准确地反映冻融和盐蚀作用后盐渍化黄土的强度和变形特性。

In order to study the influence of factors such as the number of freeze-thaw cycles,confining pressure,and salt content on the mechanical properties of salinized loess in Ili,triaxial tests of salinized loess under the action of indoor freeze-thaw cycles were carried out.The deterioration mechanism of salinized loess after freeze-thaw and salt erosion was analyzed,and the strength deterioration formula and constitutive model of salinized loess were proposed.The results show that the increase of salt makes the stress-strain curve shift from softening type to hardening type under the action of freeze-thaw cycles.When the salt content is higher,the shear strength of loess decreases rapidly with the increase of the number of freeze-thaw cycles.The cohesion is exponentially related to the number of freeze-thaw cycles.The internal friction angle shows an increase and then a decrease with the increase in the number of freeze-thaw cycles and decreases with the increase in salt content.A degradation model of cohesion under freeze-thaw is established,which can predict the degradation characteristics of cohesion in specimens with different salt contents.The weight of the freeze-thaw effect on cohesion degradation is greater than that of salt corrosion.A modified Duncan-Chang model with multi-factors is proposed,which can more accurately reflect the strength and deformation characteristics of salinized loess after freeze-thaw and salt erosion.