冻结粉质黏土-桩基接触面剪切特性试验研究

在寒区工程中， 建筑物的冻拔病害和冻土-桩基接触面间的剪切特性密切相关。借助自制的试验模具， 采用压桩法对冻结粉质黏土中埋置的混凝土桩、 钢桩以及木桩进行了不同负温条件下的剪切试验。结果表明： 在负温下随着剪切位移的增加， 剪切力经历线性增长、 骤降的脆性破坏、 维持恒定三阶段。温度越低， 桩与冻土间的冰胶结力越大， 冻结强度越大， 残余强度越大， 破坏允许位移也越大。在-30 ℃时， 木桩与冻土间的冻结强度最大， 混凝土桩与冻土间的冻结强度次之， 钢桩与冻土间的冻结强度最小。混凝土桩、 钢桩对应的冻结强度及残余强度与温度的关系可用线性拟合， 木桩对应的冻结强度及残余强度与温度的关系可用二次多项式拟合， 三种桩的破坏允许位移与温度的关系均呈现线性规律。研究成果可为寒区结构物抗冻拔病害防治提供参考。

Experimental study on shear characteristics of the interface between the frozen silty clay and the pipe foundation

The pile foundation freezing uplift in cold region engineering is closely related to the shear behaviors of interface between the frozen soil and pile foundation. With the help of a self-design apparatus， series of the shear tests for concrete piles， steel piles and wood piles embed in gen-he silty clay at different freezing temperatures were carried out by using the static pressed pile method. Some conclusions can be obtained. At negative temperature， with the increased of shear displacement， the shear force experienced three stages： linear increased stage， brittle failure with an abrupt drop stage， and a stability stage. The lower the temperature， the greater the cementation force of ice between the pile and frozen soil. As a result， the freezing strength， the residual strength， and the allowable displacement of failure was higher in the lower negative temperature. It was worth mentioning that the freezing strength between the wooden pile and frozen soil interface was the highest， followed by that between the concrete pile and frozen soil interface， all big than that between the steel pile and frozen soil interface. The freezing strength and residual strength of the concrete pile and the steel pile had a linear relationship with the frozen temperature. However， the freezing strength and residual strength of the wooden pile has a quadratic function relationship. The allowable displacement of failure of the three kinds of piles had linear correlation with frozen temperature. This study is expected to provide a reference for the research on the shear characteristics between the frozen soil and the pile interface， and also supposed to help solving the pile foundation freezing uplift problem in cold region engineering.