隧道开挖对邻近桩基变形及承载能力影响的弹塑性解答

发布时间：2018-06-15 05:22

本文选题：隧道工程 + 桩基变形　；参考：《岩石力学与工程学报》2017年01期

【摘要】：采用球形孔和圆柱孔扩张(收缩)理论研究桩基与隧道的相互作用。首先,基于Mohr-Coulomb屈服准则,采用圆柱形孔收缩模型模拟隧道开挖过程,得到Pasternak地基上隧道开挖引起的邻近单桩弹塑性水平位移。其次,提出隧道开挖对邻近桩基承载能力弹塑性影响的计算方法。桩基总承载能力由桩端极限承载能力和桩身极限侧阻摩擦力两部分组成。其中,采用无限介质中球形孔扩张模型计算桩端小孔极限压力,并得到桩端极限承载能力;采用修正的?法计算临界状态下桩身等效平均剪应力分布,进而得到桩身极限侧阻摩擦力,该方法考虑隧道开挖对桩身剪应力的削减作用。在此基础上,计算隧道开挖过程对周围土体弹塑性应力的影响;分析隧道和桩基相对位置对桩基承载能力的影响;定义桩基总承载力降低到85%时桩基发生破坏,研究桩端与隧道中心相对间距与桩基破坏时隧道体积损失临界值的关系,并考察土体黏聚力、内摩擦角、密实度、土体模量以及桩径等参数的影响。结果表明,柱孔收缩弹塑性模型可以较好地模拟隧道开挖对邻近桩基弹塑性水平位移的影响;隧道开挖后在一定范围内形成一个塑性区,在该区域内土体有效应力影响因子Rp值小于1,表明对桩基承载能力有削减作用,当桩身全部处于塑性区以外时,其承载能力不受隧道开挖的影响;隧道和桩基相对位置对桩基承载能力有较大影响,当桩端与隧道中心的间距一定时,随着隧道埋深的增加,桩端极限承载力影响因子Rqb逐渐趋于1,说明增加隧道埋深对桩基承载力更加有利;桩基破坏时隧道体积损失临界值与桩端隧道中心间距平方呈线性关系,桩基承载能力对土体模量比较敏感。
[Abstract]:The interaction between pile foundation and tunnel is studied by the expansion (contraction) theory of spherical and cylindrical holes. Firstly, based on Mohr-Coulomb yield criterion, the tunnel excavation process is simulated by cylindrical hole shrinkage model, and the elastic-plastic horizontal displacement of adjacent single pile caused by tunnel excavation on Pasternak foundation is obtained. Secondly, the method of calculating the influence of tunnel excavation on the bearing capacity of adjacent pile foundation is presented. The total bearing capacity of pile foundation consists of two parts: the ultimate bearing capacity of pile end and the ultimate friction force of pile body. The limit pressure of the small hole at the end of the pile is calculated by using the spherical hole expansion model in infinite medium, and the ultimate bearing capacity of the pile end is obtained. The equivalent mean shear stress distribution of the pile body under critical state is calculated by the method, and the ultimate friction force of the pile body is obtained. This method considers the effect of tunnel excavation on the shear stress reduction of the pile body. On this basis, the influence of tunnel excavation on the elastoplastic stress of surrounding soil is calculated, the influence of the relative position of tunnel and pile foundation on the bearing capacity of pile foundation is analyzed, and the failure of pile foundation is defined when the total bearing capacity of pile foundation is reduced to 85. The relationship between the relative distance between pile end and tunnel center and the critical value of tunnel volume loss when pile foundation is destroyed is studied. The influence of soil cohesion angle of internal friction compactness modulus of soil and pile diameter are investigated. The results show that the elastic-plastic model can simulate the influence of tunnel excavation on the elastoplastic horizontal displacement of adjacent pile foundation, and a plastic zone is formed in a certain range after tunnel excavation. The effective stress factor R p is less than 1 in this region, which indicates that the bearing capacity of pile foundation can be reduced. When the pile body is outside the plastic zone, its bearing capacity is not affected by tunnel excavation. The relative position of the tunnel and the pile foundation has great influence on the bearing capacity of the pile foundation. When the distance between the pile tip and the center of the tunnel is fixed, with the increase of the buried depth of the tunnel, The influence factor Rqb of ultimate bearing capacity of pile end gradually tends to be 1, which indicates that increasing the buried depth of tunnel is more favorable to the bearing capacity of pile foundation, and the critical value of tunnel volume loss is linearly related to the square of center distance between pile end and tunnel when pile foundation is destroyed. The bearing capacity of pile foundation is sensitive to soil modulus.
【作者单位】：上海理工大学环境与建筑学院;国土资源部丘陵山地地质灾害防治重点实验室;重庆交通大学山区桥梁与隧道工程国家重点实验室培育基地;中国建筑科学研究院;
【基金】：上海自然科学基金项目(15ZR1429400) 国土资源部丘陵山地地质灾害防治重点实验室课题(2015k005) 重庆交通大学山区桥梁与隧道工程国家重点实验室培育基地课题(CQSLBF Y15 1)~~
【分类号】：U452

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