Frozen sand—concrete interface direct shear behavior under constant normal load and constant normal height boundary

Abstract

The shear strength properties of the frozen sand—structure interface are critical for evaluating the serviceability of pile foundations in frozen ground. The shear characteristics of the frozen sand—concrete interface were studied with two boundary conditions (constant normal load (CNL) and constant normal height (CNH)), at three normal stresses (100, 200, and 300 kPa), and at three temperatures (−2,−5, and −8 °C). A detailed comparative analysis was performed to explore the principal factors affecting the shear/normal-shear displacement. The results showed that the shear behavior of the frozen sand—concrete interface under CNL was similar to that under CNH. The shear stress—shear displacement exhibited strain softening. The temperature and normal stress were the major influences on normal properties. The lower the temperature and the higher the normal stress, the greater was the elastic shear modulus. The peak shear stress and critical shear stress exhibited a dependence on normal stress. An exponential growth in the peak shear stress was observed as the temperature decreased. Critical shear stress was dependent on temperature. The value and percentage of peak ice-cementation in peak shear stress was affected by temperature and normal stress. 目的 探究不同边界条件下，初始法向应力和温度对冻结砂-混凝土接触面剪切变形和强度特性、法向变形特性以及冰胶结特性的影响。 创新点 1. 在不同边界条件下对冻结砂-混凝土结构进行直剪试验，了解接触面法向和切向特性；2. 建立试验模型，成功模拟弹性剪切模量和强度随温度及初始法向应力的变化关系。 方法 1. 通过实验分析，得到冻结接触面弹性模量和强度特性随温度和初始法向应力的变化（图14∼21和表2∼5）；2. 通过理论推导，构建温度、法向应力与弹性剪切模量和剪切强度之间的关系，得到相应的计算模型（公式(1)∼(6)）。 结论 1. 不同边界条件下，冻结接触面均表现出应变软化特性；2. 弹性剪切模量随初始法向应力的增加和温度的降低呈线性增长趋势；3. 冻结接触面剪切强度随初始法向应力的增加线性增长，而随温度的降低呈指数增长。