不同溶洞条件下穿越溶洞桩基础竖向荷载传递机制  

Vertical Load Transfer Mechanism of Pile Foundations Under Different Cave Conditions

作　　者：郑涛 郭嘉 刘衍文 牟飞 牛瑞 李辉[2] ZHENG Tao;GUO Jia;LIU Yanwen;MOU Fei;NIU Rui;LI Hui(Zhongjian Railway Investment and Construction Group Co.Ltd.,Wuhan 430014,China;College of Civil Engineering and Water Resources,Shandong University,Jinan 250100,China)

机构地区：[1]中建铁路投资建设集团有限公司,武汉430014 [2]山东大学土建与水利学院,济南250100

出　　处：《河南科学》2024年第8期1163-1169,共7页Henan Science

基　　金：泰山产业领军人才工程资助(tscy20230660)。

摘　　要：穿越溶洞桩基础竖向荷载传递机制是特殊岩溶发育地区桥梁基础设计的核心问题.依托新建沪渝蓉高速铁路马河特大桥24#号墩岩溶桥基工程,开展区域地层(上覆粉质黏土层,下部风化灰岩)中桩基础竖向受荷现场试验.结合有限元数值模拟方法,研究有无溶洞、不同溶洞直径和不同溶洞位置等因素对穿越溶洞桩基础竖向荷载传递机制的影响规律.研究结果表明:(1)相比于无溶洞条件,溶洞存在导致桩基竖向承载力降低,溶洞以上的桩侧摩阻力减小,溶洞以下的桩侧摩阻力增大,桩身压缩量增加;此外,溶洞存在降低了桩身侧阻的荷载分担比,有利于发挥端阻.(2)在不同地层中,溶洞直径变化对桩侧摩阻力的影响有所不同.下部岩层中桩侧摩阻力随着溶洞直径的增大而增大,而上覆土层中变化不明显;整体看来,桩侧摩阻力的荷载分担比随溶洞直径的增大而减小,端阻力占比随之增大.(3)随着溶洞深度的增大,溶洞以上岩层中桩侧摩阻力减小,溶洞以下在1倍溶洞直径范围内桩侧摩阻力增大,桩身压缩量和桩身荷载分配的变化不明显.Vertical load transfer mechanism of pile foundation through cavern is the core problem of bridge foundation design in special karst development area.Relying on the karst bridge foundation project of No.24 pier of Mahe Bridge of the new Shanghai-Chongqing-Rongzhou high-speed railroad,the field test of vertical loading of pile foundation in the regional stratum(overlying powdery clay layer and lower weathered grey rock)is carried out.Combined with the finite element numerical simulation method,the study investigates the influence of factors such as the presence or absence of cavities,different cave diameters and different cave locations on the vertical load transfer mechanism of pile foundations.The results show that:(1)compared with the no-cave condition,the presence of the cave leads to a reduction in the vertical load carrying capacity of the pile foundation,a decrease in the pile lateral resistances above the cave,an increase in the pile lateral resistances below the cave,and an increase in the compression of the pile body.In addition,the presence of the cave reduces the load sharing ratio of the pile lateral resistances,which is favorable to the exertion of the end resistances.(2)In different strata,the influence of the cave diameter on the pile side friction resistance is different.In the lower rock layer,the pile lateral friction resistance increases with the increase of the diameter of the cavern,while the change is not obvious in the overlying soil layer.Overall,the load sharing ratio of the pile lateral friction resistance decreases with the increase of the diameter of the cavern,while the proportion of the end resistance increases.(3) As the depth of the cavern increases,the pile lateral resistance decreases in the rock layer above the cavern,while increases in the range of 1 time the diameter of the cavern below the cavern,and the changes of the pile compression and pile load distribution are not obvious.

关 键 词：穿越岩溶桩基础 现场试验 数值模拟 桩侧摩阻力 荷载分担比 

分 类 号：TU473[建筑科学—结构工程] U441.1[建筑科学—土工工程]