考虑开挖卸荷影响的桩侧摩阻力等效计算方法

发布时间：2018-06-03 14:29

本文选题：开挖卸荷 + 均布上拔荷载　；参考：《岩土力学》2016年10期

【摘要】：基坑开挖后的卸荷回弹会导致桩侧摩阻力减小,但这一影响仅局限于基坑底部一定深度范围内。在计算开挖后的桩侧摩阻力时,可将卸荷视为作用在坑底的均布上拔荷载。当荷载作用在地表以下,土体附加应力应采用Mindlin应力解。定义基于Mindlin解计算开挖后桩侧摩阻力与开挖前变化为5%时的深度为开挖影响计算深度Hc,开挖深度和宽度对Hc的影响明显,土体内摩擦角的影响较小,而泊松比的影响可以忽略。据此推导出Hc的计算公式。开挖卸荷导致的竖向附加应力,Boussinesq解求得的结果大于Mindlin解,但随着深度增加,二者差异逐渐减小。分别针对开挖深度、宽度和内摩擦角不同取值的216种组合进行计算,结果表明,Hc范围内基于Mindlin解求得的桩侧摩阻力与基于Boussinesq解结果的比值ω最大为1.124,最小为1.001。工程实践中为偏于安全,可直接采用Boussinesq解进行桩侧摩阻力计算。
[Abstract]:The unloading springback after excavation of foundation pit will result in the decrease of pile side friction, but this effect is limited to a certain depth range of foundation pit bottom. In calculating the pile side friction after excavation, the unloading can be regarded as the uniformly distributed pull-out load acting on the bottom of the pit. When the load is below the surface, the additional stress of soil should be solved by Mindlin stress. The calculation of pile side friction after excavation based on Mindlin solution and the depth of change before excavation to 5 are defined as the calculation depth of excavation effect, the influence of excavation depth and width on HC is obvious, the influence of soil internal friction angle is relatively small, and the influence of Poisson's ratio can be neglected. Based on this, the calculation formula of HC is deduced. The results obtained by the Boussinesq solution due to excavation unloading are larger than those obtained by the Mindlin solution, but the difference between them decreases with the increase of depth. Two hundred and sixteen combinations with different values of excavation depth, width and angle of internal friction are calculated. The results show that the ratio 蠅 of pile side friction based on Mindlin solution and Boussinesq solution is 1.124 and 1.001 respectively. For the sake of safety in engineering practice, the Boussinesq solution can be directly used to calculate the lateral friction of pile.
【作者单位】：浙江省建筑设计研究院;浙江大学岩土工程研究所;
【分类号】：TU473.1

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