地下水渗流对冻土区模型桩力学特性的影响分析

为了研究冻土区地下水的渗流效应对桩基的荷载传递规律的影响，考虑到桩身轴力、桩侧冻结应力和桩周土温度对桩基承载力均有影响，依据室内模拟试验，分别模拟了无地下水、桩顶水有温度效应、桩底水有温度效应、桩顶水有温度及渗流效应、桩底水有温度及渗流效应5种不同工况下地下水对冻土桩基承载力的影响。试验结果表明：无论是桩顶水还是桩底水，在接近地下水处，同时有温度效应及渗流效应的轴力值变化比仅有温度效应时的小，当地下水为桩底水时加载后的桩轴力小于地下水为桩顶水时的轴力值；桩底水引起的桩侧冻结应力变化幅度比桩顶水大，地下水的温度效应使得部分冻土温度升高而融化，而地下水的渗流效应进一步增大了冻土融化范围，使得桩基力学特性发生改变，进而影响了桩基承载力。

Analysis of the influence of groundwater seepage on the mechanical properties of model piles in frozen soil region

In order to understand the effect of the groundwater seepage on pile foundation in permafrost, considering the axial force and lateral frozen stress of pile, and soil temperature affecting the bearing capacity of pile foundation, a simulation test have carried out. The effects of groundwater on the bearing capacity of permafrost pile foundation under five different working conditions have been simulated, respectively, including there is no groundwater, the pile bottom water has temperature effect only and the pile bottom water has temperature effect and seepage effect both, the pile top water has temperature effect only and the pile top water has temperature effect and seepage effect both. The following conclusions can be drawn:Under the five working conditions, the axial force of the pile is the maximum when there is no groundwater and the axial force decreases downward, when the condition of temperature effect and seepage effect is less than that under the condition of temperature effect only. Compared with no groundwater, the effect of groundwater on frozen stress is more obvious; the water at the top of the pile has a great influence on the lateral frozen stress of the upper half of the pile and the water at the bottom of the pile has a great influence on the lateral frozen stress on the lower half of the pile. As a whole, the variation range of the lateral frozen stress caused by the ground water is larger than that caused by the top water. The temperature effect of water at the pile bottom only is more significant than that the temperature effect together with seepage effect, and the temperature effect and seepage effect of water at the pile top both result in frozen stress on the pile side more serious than that with temperature effect only. At the same depth, groundwater temperature and seepage effect together result soil temperature rise more than only groundwater temperature effect, making frozen stress acting on the pile rapidly decrease, at the same time, the temperature effect of groundwater makes the adjacent frozen soil warm and thawing, and the seepage effect also makes a wider range of frozen soil warm and thawing, the mechanical properties of pile foundation changed, resulting in changing bearing capacity of pile foundation.