Elastoplastic behavior of frozen sand—concrete interfaces under cyclic shear loading

Abstract

The resilient modulus, accumulated plastic strain, peak shear stress, and critical shear stress are the elastoplastic behaviors of frozen sand—concrete interfaces under cyclic shear loading. They reflect the bearing capacity of buildings (e.g. high-speed railways) in both seasonal frozen and permafrost regions. This study describes a series of direct shear experiments conducted on frozen sand—concrete interfaces. The results indicated that the elastoplastic behaviors of frozen sand—concrete interfaces, including the resilient modulus, accumulated plastic strain, and shear strength, are influenced by the boundary conditions (constant normal loading and constant normal height), initial normal stress, negative temperature, and cyclic-loading amplitude. The resilient modulus was significantly correlated with the initial normal stress and negative temperature, but not with the cyclic-loading amplitude and loading cycles. The accumulated plastic shear strain increased when the initial normal stress and cyclic-loading amplitude increased and the temperature decreased. Moreover, the accumulated plastic shear strain increment decreased when the loading cycles increased. The accumulated direction also varied with changes in the initial normal stress, negative temperature, and cyclic-loading amplitude. The peak shear stress of the frozen sand—concrete interface was affected by the initial normal stress, negative temperature, cyclic-loading amplitude, and boundary conditions. Nevertheless, a correlation was observed between the critical shear stress and the initial normal stress and boundary conditions. The peak shear stress was higher, and the critical shear stress was lower under the constant normal height boundary condition. Based on the results, it appears that the properties of frozen sand—concrete interfaces, including plastic deformation properties and stress strength properties, are influenced by cyclic shear stress. These results provide valuable information for the investigation of constitutive models of frozen soil—structure interfaces.

Abstract

目的

冻结砂–混凝土结构接触面在循环剪切荷载作用下的弹性剪切模量和累积塑性应变是决定冻土区结构承载力的关键因素。本文旨在探讨冻结砂–混凝土接触面在循环加载条件下的变量(循环加载次数、法向应力、冻结温度和循环加载幅值)对初始弹性剪切模量、循环弹性剪切模量、累积塑性变形和剪切强度的影响, 了解冻结接触面在循环剪切过程中的弹塑性, 为建立循环剪切荷载作用下冻结接触面本构模型提供重要的试验数据支撑。

创新点

1. 对冻结接触面施加两种不同边界条件(常法向应力和常法向位移), 并通过对冻结接触面施加循环剪切荷载得到不同试验条件下冻结接触面的弹性特性、塑性变形特性以及强度特性; 2. 建立冻结接触面塑性变形模型, 探讨不同因素对塑性变形的影响。

方法

1. 通过试验分析, 得到不同条件下的塑性变形值、强度值以及不同阶段的弹性剪切模量, 并对其进行定性分析; 2. 构建累积塑性体应变–累积塑性剪应变经验公式(公式(5)), 并通过理论推导, 得到累积塑性应变方向(公式(6)); 3. 绘制不同参数与法向应力、温度和循环加载幅值的关系曲线, 并研究不同因素对累计塑性应变方向的影响(图11、13和15)。

结论

1. 温度和法向应力对初始弹性剪切模量和循环弹性剪切模量影响很大; 2. 冻结接触面塑性剪应变和累积塑性体应变随着循环剪切次数的增加、温度的降低和法向应力的增大而增大, 但其增量随着循环次数的增加而逐渐减小; 3. 累积塑性剪应变与累积塑性体应变呈指数关系; 4. 峰值剪应力随法向应力的增大、温度的降低和循环幅值的增大而增大。