下伏空洞桥梁群桩桩端岩层极限承载力计算方法研究  

Calculation method of ultimate bearing capacity for rock layer of pile tip of bridge pile groups with underground karst cave

作　　者：雷勇[1] 陈于斯 谭豪 李鹏甲 刘运思[1] 于艺林 LEI Yong;CHEN Yu-si;TAN Hao;LI Peng-jia;LIU Yun-si;YU Yi-lin(Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring,Hunan University of Science and Technology,Xiangtan,Hunan 411201,China;China Construction Municipal Engineering Corporation Limited,Beijing 100071,China)

机构地区：[1]湖南科技大学岩土工程稳定控制与健康监测湖南省重点实验室,湖南湘潭411201 [2]中建市政工程有限公司,北京100071

出　　处：《岩土力学》2023年第12期3339-3348,共10页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.51878270);湖南省自然科学基金(No.2022JJ30253)。

摘　　要：为探究下伏空洞桥梁群桩桩端岩层的承载机制和破坏模式,进行了单桩及不同桩数群桩的室内模型试验研究,得到了不同桩数群桩桩端岩层的极限承载力和破坏模式。根据下伏空洞桥梁群桩桩端岩层破坏模式的特点将破坏面分为两个部分,结合极限分析法提出了下伏空洞桥梁群桩桩端岩层极限承载力计算方法,理论计算值与室内试验值吻合良好,验证了计算方法的合理性。同时分析了桩端岩层极限承载力随桩数增加的变化规律,可为岩溶区桥梁桩基工程建设提供参考。试验及理论计算结果表明:(1)下伏空洞群桩桩端岩层发生整体冲切破坏时,破坏体整体可视为与单桩破坏体等效的大型墩基;(2)当桩间距较小时,群桩桩端岩层极限承载力随外围基桩外包络线长度增大而增加,当外包络线长度相同时,内部基桩布置方式对群桩桩端岩层极限承载力无影响;(3)群桩效应系数随桩间距的增大而增加,临界桩间距为5d~6d(d为桩径)。To explore the bearing mechanism and failure mode for rock layer of pile tip of bridge pile groups with underground karst cave,laboratory model tests of single pile and pile groups with different numbers of piles were carried out.The ultimate bearing capacity and failure modes for rock layer of pile tip of pile groups with different numbers of piles were captured.The failure surface was divided into two parts according to the characteristics of the failure mode for the rock layer with underground karst cave,and a calculation method for ultimate bearing capacity was developed by combining with limit analysis method.The theoretical calculation values match well with the experimental values,which verifies the rationality of the proposed method.Meanwhile,the relationship between the ultimate bearing capacity for the rock layer has been analyzed and it can provide reference for bridge pile foundation construction in karst area.The experimental and theoretical calculation results indicate that:(1)When the rock layer of pile tip of pile groups with underground karst cave is overall destroyed,the whole destroyed body can be regarded as a large pier foundation similar to destroyed body of single pile.(2)When the pile spacing is smaller,the ultimate bearing capacity for the rock layer increases with the increase of the length of the outer envelope line of outer foundation pile.Furthermore,when the length of outer envelope lines are the same,the arrangement of internal foundation piles has no effect on the ultimate bearing capacity for the rock layer.(3)The coefficient of pile group effect increases with increasing the pile spacing,and the critical pile spacing is 5d−6d(d is the pile diameter).

关 键 词：桥梁群桩 空洞地基 极限承载力 极限分析 群桩效应系数 

分 类 号：TU473[建筑科学—结构工程]