史向阳 张泽 李东庆 张中琼

摘 要：结合工程实际，通过室内模型试验方法，研究锥柱式桩基础明挖基坑回填土在模拟实际环境温度条件下的回冻过程.结果表明，在模拟平均温度为-2.71 ℃的环境温度条件下，正温极值时刻表层土体融化深度约6.1 cm，回填土冻结深度随着冻融次数的增加而增厚，经历13次冻融循环，冻结层厚度达20.0 cm；桩基沿着水平向和纵向对回填土回冻过程产生影响，但其影响范围有限；土体和桩基与空气界面温度存在差异，桩基和空气界面处温度接近低温试验箱内空气温度，土体和空气界面处与空气温度差别较大，正温极值状态，空气温度高于土表温度5.0 ℃，负温极值状态，空气温度低于土表温度6.7 ℃.试验结果有助于进一步认识此类桩基回填土实际回冻过程，为确定模型试验控温条件及数值模拟边界条件提供参考.

关键词：锥柱式桩基础；模型试验；回冻过程；回填土

中图分类号： TU47 文献标志码：A

文章编号：1674—2974（2018）07—0125—10

Abstract： Based on the engineering construction method，the refreezing process of backfill is investigated by model test method under simulated ambient temperature. The results indicate that the frozen layer thickness increases with the freeze-thaw cycles when the simulated average temperature is -2.71 ℃. The thawing depth is about 6.1 cm at maximum ambient temperature in every freeze-thaw cycle， and the frozen layer thickness increases to 20.0 cm after 13 freeze-thaw cycles. The pile foundation has an effect on the refreezing process of backfill in the horizontal and longitudinal directions， but its scope of influence is limited. The interface temperature between air and pile is close to the air temperature， but the interface temperature between air and soil is very different from air temperature. The air temperature is higher than air-soil interface temperature by 5.0 ℃ at the maximum ambient temperature， and lower than air-soil interface temperature by 6.7 ℃ at the minimum ambient temperature. This experiment results help to further understand the actual refreezing process of backfill， and provide reference for determining the control conditions in model test and the boundary conditions of numerical simulation.

Key words： cone-cylindrical pile foundation；model tests；refreezing process；backfill

冻土指处于零摄氏度以下并含有冰的各类岩石和土壤，其工程性质复杂[1]，与基础工程之间作用密切.桩基础因其埋置深度大，相对其他浅基础而言受环境影响较小，能够为上部结构提供较大的承载力，在冻土区得到了广泛的应用.有关冻土区桩基础方面的研究，多集中于钻孔灌注桩的回冻[2]，环境升温和太阳辐射[3]及特殊地质条件下[4-5]的桩基热力稳定性研究，研究方法包括现场原型试验、模型试验、数值模拟等.在多年冻土……