多年冻土区斜坡地带锥柱基础初始回冻过程模型试验

青海—西藏±400 kV直流联网工程沿线穿越多年冻土区565 km，其塔基将不可避免地遇到大量的冻土工程地质问题。锥柱型基础具有承载能力强并可消减切向冻胀力的特点，因而成为该条线路多年冻土区杆塔基础的主要形式。本文以青藏±400 kV直流联网工程为背景，对多年冻土地区斜坡地带锥柱型基础在回冻过程中的稳定性开展研究。主要通过相似比为1∶10的室内模型试验，监测地基土回冻过程中基础所受的冻胀应力，以及基础位移在水平与垂直方向的变化规律，并基于试验结果和研究现状对工程设计、施工与维护提出建议。试验结果显示：在冻结过程中随着地基土温度的降低冻胀力逐渐增大，基础顶部的水平冻胀力最大达到130 kPa，基础底部的法向冻胀力最大可达80 kPa。冻结过程中基础有冻拔现象，最大为5.5 mm。试验中基础顶部的水平位移最大达到3.8 mm。

Model tests on initial freezing process of column foundation on slope in permafrost regions

The Qinghai-Tibet ±400 kV electrical transmission line traverses more than 550 km in permafrost regions, which may lead to a lot of frozen soil engineering problems for the foundations of transmission tower. Since the column foundation can not only reduce frost heave force but also provide higher bearing capacity, it has been accepted as the first choice of foundation design in permafrost regions. Considering the engineering background of the electrical transmission line, the stability of the column foundation in the initial freezing process is highlighted. In the laboratory, the model tests with a scale of 1:10 are carried out, and both the frost heave and the heave force of the column foundation are monitored. Based on the test results as well as engineering experience, suggestions for the design, construction and maintenance of the project are addressed. The model tests show that the heave force increases with the decreasing temperature in the foundation soil, and the horizontal heave force on the top of the foundation can rise to 130 kPa, while the normal heave force at the bottom can rise to 80 kPa. During the freezing process, the frost heave of the foundation is much greater. The vertical displacement of the foundation can reach 5.5 mm, and the horizontal displacement at the top of the foundation can reach 3.8 mm.