岩溶地基加固前后超长桩基承载效果研究

Study on Vertical Bearing Characteristics of Super Long Pile Foundation in Reinforced and Unreinforced Karst Subgrade

以南玉高速铁路跨黎湛特大桥132号墩桩基建设工程为背景,采用有限元方法分析了岩溶地基加固前后高速铁路桥梁超长桩基承载特性.结果表明:无填充和部分填充岩溶地基中桩基荷载-沉降曲线呈陡降型,全填充地基中桩基荷载-沉降曲线呈缓变型.地基加固能显著提高桥梁桩基的极限承载力,且素混凝土填充方案效果最佳;如填充溶洞数量条件受限时,应优先填充上层溶洞.岩溶空洞高度对于桩基承载力影响较大,随着高度从4 m依次增加到12 m,桩基承载力降低约25%.串珠状溶洞较易在地基中形成拱效应,进而影响桩基受力.研究成果可为岩溶区高速铁路桥梁超长桩基建设提供技术参考.

Based on the construction of No.132 pier pile foundation of Litang-Zhanjiang super large bridge in Nan'ning-Yulin high-speed railway engineering,the bearing characteristics of super long pile in karst foundation are analyzed by finite element method before and after foundation reinforcement.The results show that the load settlement curves of pile foundation in unreinforced and partially reinforced karst foundation present steep drop type,while that in fully reinforced foundation presents slow change type.The ultimate bearing capacity of bridge pile foundation can be significantly improved by foundation reinforcement,and the plain concrete reinforcement scheme has the best effect.If the number of karst caves to be reinforced is limited,the upper karst caves shall be reinforced firstly.The height of karst cavity has a great impact on the bearing capacity of pile foundation.With the height increasing from 4 m to 12 m,the bearing capacity of pile foundation decreases by about 25%.Beaded karst caves are easy to form arch effect in the foundation,and then affect the stress of pile foundation.The research results can provide technical reference for the construction of super long pile foundation of high-speed railway bridges in karst areas.