刚性长短桩软基预处理对堆载邻近桩基的变位影响分析及处理效果评价  

Analysis on Influence of Rigid Long-short-pile Soft Foundation Pretreatment on Deformation of Adjacent Surcharged Pile Foundation and Treatment Effect Evaluation

作　　者：冯忠居[1] 何静斌 董芸秀 冯凯[1] 朱彦名 FENG Zhong-ju;HE Jing-bin;DONG Yun-xiu;FENG Kai;ZHU Yan-ming(School of Highway,Chang'an University,Xi'an Shaanxi 710064,China)

机构地区：[1]长安大学公路学院

出　　处：《公路交通科技》2019年第8期67-77,共11页Journal of Highway and Transportation Research and Development

基　　金：中央高校基本科研业务费资助项目(300102218115)

摘　　要：在河谷地区修建桥梁桩基础时,常会遇到因桥台后高路基填土而导致路基一侧桩基础发生偏位的工程事故,尤其是当地基土中存在软弱土层时,发生事故的可能性大大增加。为探明刚性长短桩在处理侧方路基填土下软弱土层时的应用效果,研究不同因素对刚性长短桩处理效果的影响以及采用刚性长短桩处理对高路基填土侧桩基础的影响,依托马里河Ⅱ桥实体工程,采用数值模拟软件Marc分析了不同布置形式和不同处理距离下的刚性长短桩对填土侧桩基础受力分布特性的影响,对不同工况的处治效果进行了工程评价并依此提出了相关的工程建议。结果表明:堆载作用下,软弱土层的侧向挤压变形对桩身位移、桩侧土抗力和桩身弯矩等均有明显影响,桩身位移在16 m(即软土层与强风化岩层的分界面)处出现明显拐点,桩侧土抗力和桩身弯矩在16 m处达到最大值;不同距离下的桩基桩身位移等各项数值变化规律基本一致但影响程度大小不同,最靠近堆载外侧的桩处于最不利位置,设计时可适当提高边侧桩基的承载性能;梅花桩布置形式的刚性长短桩相较于正方形布置和交错布置对减少软弱土层侧向挤压变形对桥梁桩基础影响的效果最显著;梅花形布置形式的加固区在不同处理距离下的处治效果差异显著,加固区处理距离范围不宜距离桩基础过近,也不宜过远,8 m左右距离的处理效果最优。When building bridge pile foundation in valley area, it often meets the engineering accident caused by high subgrade filling behind the abutment, which results in the deviation of pile foundation on one side of subgrade, especially when there is the soft soil layer in the underlying soil, the possibility of accident is greatly increased. In order to explore the application effect of rigid long-short-pile in treating the soft soil layer under the side subgrade filling, and analyze the influence of different factors on the treatment performance of rigid long-short-pile and the influence of using rigid long-short-piles on the lateral pile foundation in high subgrade filling, relying on the practical project of Mali River bridge Ⅱ, the influence of rigid long-short-piles on the stress distribution characteristics of pile foundation at filling side under different layouts and different treatment distances are analyzed by using numerical simulation software Marc. The treatment effects under different conditions are evaluated and the related engineering proposals are proposed accordingly. The result shows that (1) Under surcharge load, the lateral compression deformation of the soft soil layer has a significant influence on the pile displacement, the soil resistance on the pile side and the pile bending moment. There is a significant inflection point of the pile displacement in the depth of 16 m (the interface between soft soil layer and strong weathered rock layer), and the resistance of the pile side soil and the bending moment of the pile body reach a maximum in the depth of 16 m.(2)The change rule of displacements of pile foundation and pile body in different positions is basically the same but the degree of influence is different. The pile closest to the outside of the surcharge load is in the most disadvantageous position, and the bearing capacity of the side pile foundation should be increased properly in the design.(3) Compared with the square and staggered layouts, the quincuncial stakes arranged rigid long-a

关 键 词：桥梁工程 地基处理 数值模拟 软弱土层 堆载 刚性长短桩 

分 类 号：U443.15[建筑科学—桥梁与隧道工程] TU447[交通运输工程—道路与铁道工程]