基于岩溶三维地质模型的桩基承载力特性研究

Bearing Capacity Characteristics of Piles Based on Three-dimensional Geological Model of Karst

本文依托中铁十九局集团有限公司岑大公路YTHJ4标桥梁桩基项目,通过Civil 3D软件建立了三维地质模型;并介绍了桩基作用下溶洞两种不同的破坏模式;然后采用基于FLAC 3D数值分析软件的单因子变量法分析了不同溶洞顶板厚度、顶板跨度、洞高、溶洞中心偏离桩轴线距离等对嵌岩桩承载力特性(极限承载力、极限侧摩阻力、桩土相对滑移距离等)的影响。研究结果表明:溶洞顶板是影响桩基极限承载力的主要因素;溶洞极限状态下的破坏模式强烈依赖于溶洞顶板厚度、顶板跨度和岩体力学性质;当溶洞顶板厚度达到三倍的桩径时,桩侧摩阻力可完全发挥;溶洞顶板跨度和偏心距离对桩基承载力特性的影响存在一个稳定点。这些研究结论为岩溶地区的嵌岩桩设计提供了一定的参考依据,进一步丰富了岩溶地区桩基设计理念。

This article is based on the YTHJ4 project of the Cen-Da Highway by China Railway 19th Bureau Group Co.,Ltd.,and a 3D geological model was built by Civil 3D.Two different failure modes of the cave under the action of pile foundation were introduced.Then,the single factor variable method based on FLAC 3D was used to analyze the effects of different cave roof thickness,roof span,cave height,and distance from the cave center from the pile axis on the bearing capacity characteristics of rock-socketed piles(ultimate bearing capacity,ultimate side friction resistance,relative slip distance of pile-soil,etc.).The results show that the thickness of cave roof is the most significant factor to affect the pile bearing capacity.The failure mode in the ultimate limit state of the cave strongly depends on the roof thickness,the roof span and the mechanical properties of the rock mass.When the roof thickness reaches three times the pile diameter,the pile side friction resistance can be fully exerted.There is a stable point for the influence of the span and eccentricity distance of the cave roof on the bearing capacity characteristics of the pile foundation.The research conclusions provide a certain reference basis for the design of rock-socketed piles in karst area,and enrich the design concept of pile foundation in karst area.