串珠状岩溶区桩基沉降计算与稳定分析

Settlement and stability analysis of pile foundation in string-beaded karst area

为探讨串珠状岩溶区桥梁桩基的沉降变形特性及其稳定问题,给出了按桩顶变形控制桩身竖向承载力的简化荷载传递法。结合位于深度逾百米的串珠状岩溶区桥梁群桩基础进行了沉降对比计算,并采用ADINA软件对桩端是否压浆进行了有限元数值分析。结果表明:桩端不压浆时,两种简化方法与规范法计算结果较接近,但与有限元分析结果相差较大;而桩端注浆时,理论与数值计算结果吻合较好,证明了"短摩擦桩+桩端压浆"的处理方案较长摩擦桩方案不仅能降低施工难度、有效控制沉降,且能满足整体稳定性要求,是串珠状岩溶区桩基设计的一种有效处理方法。

In order to analyze the settlement and stability of pile foundation in string-beaded karst area,simplified load transfer method was used to calculate the settlement,in which the bearing capacity of pile foundation was determined by the allowable deformation.A pile-group foundation of a bridge in string-beaded karst area of more than 100m deep was calculated by the present methods respectively.The ADINA software was used to analyze the stability considering whether grouting under the pile tip is carried out or not.Results show that,when the pile tip is not grouted,calculated settlement values by two simplified methods are close to that by the current code method,but have a big difference with the finite element analysis result.However,for a grouting under the pile tip,good agreement between the theoretical and numerical results was obtained.This verified that the treatment method（i.e.,short friction pile plus base grouting） is more effective than long pile without grouting in reducing the construction difficulty,controlling the settlement and stability of pile foundation in string-beaded karst area.