软土地区新建城市轨道交通线路路基对邻近既有线路路基水平变形的影响分析

Impact Analysis of Newly Constructed Urban Rail Transit Line Subgrade in Soft Soil Area on the Horizontal Deformation of Adjacent Line Subgrade

依托东部沿海软土地区某城市轨道交通路基帮宽工程,利用同济大学L-30土工离心机进行土工离心模型试验,研究既有CFG桩(水泥粉煤灰碎石桩)复合地基路基在邻近堆载作用下土体和桩体的水平变形规律。利用有限元数值模拟方法,研究既有路基和新建路基的不同加固形式对既有路基水平变形规律的影响。研究表明:在邻近堆载的作用下,软土地区城市轨道交通线路路基坡脚外2 m土柱的水平变形呈现“弓”型变化规律,随埋深增加,水平变形先增大后减小;路基CFG桩复合地基中的CFG桩的水平变形呈现漏斗型变化规律,桩顶水平位移最大,随埋深的增加,水平变形逐渐减小;新建路基中桩基的存在,可有效减小既有路基的水平位移;在CFG桩桩顶增加筏板,能将CFG桩的水平变形规律由漏斗型改变为“弓”型,同时减小桩体的最大水平变形。

Based on an urban rail transit subgrade widening project in eastern coastal soft soil area of China,a geotechnical centrifugal model test is conducted by using the L-30 geotechnical centrifuge of Tongji University,to study the horizontal deformation patterns of soil and pile in existing CFG(cement fly ash gravel)pile composite foundation subgrade under the action of adjacent loading.Then,the finite element numerical simulation method is used to study the influence of existing subgrade and new subgrade reinforcement forms on horizontal deformation law of the existing subgrade.The result shows that under the adjacent loading,the horizontal deformation of the soil pillars,which are located 2 meters away from the subgrade slope foot of urban rail transit line in soft soil area,demonstrates a pattern of bow-shaped deformation,the horizontal deformation increases first and then decreases during the continuous increase of burial depth.The CFG piles in CFG pile composite centrifuge subgrade demonstrate a funnel-shaped pattern deformation,the horizontal displacement is the biggest at the pile top,and decreases during the continuous increase of burial depth;the existence of pile foundation in the newly built line subgrade can effectively reduce the horizontal displacement amount of the existing subgrade,while adding a plank on top of the CFG pile can change the horizontal deformation pattern of the CFG piles from the funnel-shaped to the bow-shaped,the maximum horizontal deformation of the pile body can also be reduced.