柔性荷载作用下桩筏加固地基变形特性试验研究

摘要

针对深厚软土地区桩筏加固地基,通过原位长期观测试验,研究柔性荷载作用下桩筏加固地基与天然地基的地基面总沉降、地基分层沉降和侧向变形、地基土孔隙水压力等,对比分析两种地基变形规律的差异性,总结提出了柔性荷载作用下桩筏加固地基的受力变形机理.研究结果表明:桩筏结构相对于天然地基,其总沉降减小至24％、差异沉降减小至0.9％,说明其整体刚度较大,有利于均化地基荷载、约束地基侧向变形,使地基总沉降和差异沉降都有很大程度降低;桩筏加固地基沉降主要发生于下卧层,占总沉降的90％;路堤荷载大部分由桩筏结构承担,桩筏结构地基中超孔隙水压力相对于天然地基降低了70％,从而减小了地基沉降量.%To study the pile-raft foundation in thick soft clay ground,total settlements of foundation surface,layered settlements,lateral deformations,and pore water pressures of foundation soil for pile-raft foundation and natural foundation were observed and analyzed by long-time in-situ test.The load and deformation mechanism of pile-raft foundation under flexible load was proposed by the comparative analysis of the deformation differences between the two types of foundations.The results show that the total settlement of pile-raft foundation is reduced to be the 24％ total settlement of the natural foundation,and the differential settlement is reduce to be 0.9％.This means that the pile-raft foundation has lager integral rigidity,which can homogenize the load and restrict the lateral deformation,and lead to the reduction in the total settlement and differential settlement.The settlement of the pile-raft foundation in substratum is the main part of total settlement,which accounts for the 90％ total settlement.The pile-raft structure bears the most subgrade load.Compared with that of the natural foundation,the excess pore water pressure of the pile-raft foundation is reduced by about 70％;therefore,the settlement of foundation is reduced.