考虑初始饱和度影响的冻结渠坡膨胀土力学特性

Effect of initial saturation on mechanical properties of frozen canal expansive soil

为探究初始饱和度对渠坡膨胀土低温力学特性的影响,以不同初始饱和度渠坡膨胀土为研究对象,通过开展试验温度分别为-2℃、-5℃、-10℃和-15℃下的无侧限抗压强度试验,研究温度与初始饱和度对渠坡膨胀土强度及变形特征的影响。试验结果表明:试样的应力-应变曲线随初始饱和度的增加逐渐从软化型过渡到硬化型,两种不同类型的应力-应变关系可分别采用双曲线方程和复合指数本构方程来描述;试样的破坏形态根据其破坏特征可划分为垮塌破坏、鼓胀破坏和整体压缩破坏3种形式;-2℃下,试样的抗压强度整体随初始饱和度的增加而减小,但在-5℃、-10℃和-15℃下,试样的抗压强度随着初始饱和度的增加先增大后减小,也即存在一个“临界饱和度”使得试样的抵抗破坏能力最强,并且该“临界饱和度”随着试验温度的降低而减小;此外,随着试验温度的降低,试样的弹性模量和抗压强度均逐渐增大,但试样的硬化模量却呈现出先增大后减小的变化规律。

In order to explore the influence of initial saturation on the low-temperature mechanical properties of canal expansive soil,the unconfined compressive strength tests under-2℃,-5℃,-10℃and-15℃were carried out on canal expansive soil with different initial saturation.The effects of temperature and initial saturation on the strength and deformation characteristics of canal expansive soil are discussed.The results show that:the stress-strain curves of the samples gradually transform from softening type to hardening type with the increase of initial saturation.Two different types of stress-strain relationship can be described by hyperbolic equation and composite index equation respectively.According to the failure characteristics,the failure modes of the samples can be divided into three types:collapse failure,bulging failure and overall compression failure.At-2℃,the compressive strength of the sample decreases with the increase of initial saturation,but at-5℃,-10℃and-15℃,the compressive strength increases first and then decreases with the increase of initial saturation,there is a“critical saturation”that makes the sample have the strongest resistance to failure,and this“critical saturation”decreases with the decrease of test temperature.In addition,with the decrease of test temperature,the elastic modulus and compressive strength of the sample increase gradually,but the hardening modulus of the sample increase first and then decreases.