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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。
Qinghai-Tibet ± 400 kV DC network project will cross 565 km of permafrost along the line, and its base will inevitably encounter a large number of engineering geological problems in permafrost. The cone-column foundation has the characteristics of strong carrying capacity and can reduce the tangential frost heaving force, which has become the main form of the tower foundation of the permafrost zone. Based on the ± 400 kV DC network project in Qinghai-Tibet, this paper studies the stability of cone-and-column foundation in the frozen zone of permafrost in the process of refreezing. Mainly through the indoor model test with the similarity ratio of 1:10, the frost heave stress and the variation rule of the basic displacement in horizontal and vertical direction during the process of backfilling are monitored. Based on the experimental results and the research status, , Construction and maintenance make recommendations. The experimental results show that the frost heaving force gradually increases with the decrease of the temperature of the foundation soil during the freezing process. The maximum horizontal frost heaving force at the top of the foundation reaches 130 kPa and the maximum frost heaving force at the bottom of the foundation reaches 80 kPa. The freezing process based on the phenomenon of freezing, the maximum 5.5 mm. The maximum horizontal displacement of the foundation at the top of the test reached 3.8 mm.