软土场地路堤-加筋碎石桩复合地基工作状态分析

Analysis on working status of composite foundation with geosynthetic-encased stone column and embankment in the soft soil

软土场地碎石桩因具备桩体侧向变形大、超孔隙水压力消散慢的问题,导致出现基础沉降大、土体固结排水速度慢等工程病害。路堤下采用加筋碎石桩复合地基是处理软土场地的主流方法。本文采用二维有限元方法,建立考虑路堤填筑过程的软土场地路堤-加筋碎石桩复合地基数值模型,探讨了加筋碎石桩复合地基承载力的影响因素。基于达西定律和比奥固结理论,分析高地下水位场地条件下加筋体刚度和桩数对加筋碎石桩复合地基工作状态的影响规律。研究表明:增大褥垫层厚度和减小褥垫层模量均能够提高桩土应力比,改善桩顶应力集中的问题。与传统碎石桩相比,高地下水位条件下加筋碎石桩复合地基中超孔隙水压力消散速率快,桩数增加可以有效提高复合地基排水速率。

The gravel pile foundation in soft soil field has the problems of large lateral deformation of pile body and slow dissipation of excess pore water pressure,which lead to engineering diseases such as large settlement of foundation and slow speed of soil consolidation and drainage.Geosynthetic-encased stone column composite foundation is the main method to treat soft soil under embankment.2D finite element program is used to construct the numerical model of soft soil embankment and geosynthetic-encased stone column composite foundation.The process of embankment filling is simulated in the calculation model and the influencing factors of reinforced gravel pile on bearing capacity of composite foundation are discussed.Based on Darcy law and Biot's consolidation theory,the influence of stiffened body stiffness and pile number on the working state of geosynthetic-encased stone column composite foundation under high underground water level is analyzed.The results show that increasing cushion thickness and decreasing cushion modulus can improve pile-soil stress ratio and improve pile top stress concentration.Under the condition of high groundwater level,the dissipation rate of excess pore water pressure in geosynthetic-encased stone column composite foundation is higher than that of gravel pile.In addition,increasing the number of geosynthetic-encased stone columns can also effectively improve the composite foundation drainage rate.