岩溶地区桩基础设计研究及工程问题分析

Research on the design of pile foundation and analysis of engineering problems in a karst area

岩溶发育场地地质构造复杂,溶洞勘探由于缺乏理论指导,容易造成溶洞误判而引起场地开发成本增加,且岩溶地区桩基础贯穿溶洞的设计方法容易造成工程浪费。结合贵州岩溶强发育场地某部分框支剪力墙结构基础设计、施工遇到的工程问题,研究了溶洞误判,溶洞顶板破坏模式、溶洞对桩基承载力设计影响及贯穿溶洞设计方式的合理性。结果表明:岩溶地区选择科学的工作方法和适当的勘探方法可以减少场地“未知数”,减少溶洞误判带来的损失,更好地指导工程建设;溶洞顶板因厚度不同呈现冲切破坏、剪切破坏和弯拉破坏三种破坏模式;桩基遇串珠状溶洞及较大溶洞时,承载力计算可仅考虑桩端阻力;水平荷载较小且满足地基规范时可不穿洞;水平荷载较大时应贯穿溶洞发挥其嵌岩桩承载力。

The geological structure of the karst development site is complex,and the lack of theoretical guidance for karst cave exploration may easily lead to misjudgment of the karst cave and increase the site development cost,and the design method of the pile foundation penetrating the karst cave in the karst area is likely to cause engineering waste.Combining with the engineering problems encountered in the design and construction of the frame-supported shear wall structure in a certain part of the strong karst development site in Guizhou,the misjudgment of the karst cave,the failure mode of the karst cave roof,the influence of the karst cave on the bearing capacity of the pile foundation,and the rationality of the design method of the karst cave are studied.The results show that choosing scientific working methods and appropriate exploration methods in karst areas can reduce the“unknowns”of the site,reduce the loss caused by misjudgment of the karst cave,and better guide the construction of the project;the roof of the karst cave presents punching damage and shearing damage due to different thicknesses.There are three failure modes:failure and bending-tension failure;when the pile foundation encounters beaded karst caves and large karst caves,only the pile end resistance can be considered in the bearing capacity calculation;when the horizontal load is small and the foundation specification is satisfied,no hole is required;when the horizontal load is large,the bearing capacity of the rock-socketed pile shall be exerted through the karst cave.