软土地区公路拓宽工程的力学响应分析

Analysis of Mechanical Responses for Highway-widening Engineering on Soft Soil Foundation

针对路基拓宽工程中新老公路修建历史的差异、沉降变形的特点及其对路面结构的显著影响,建立了软土地区公路拓宽的平面非线性有限元分析模型,详细分析了老路地基为天然地基和复合地基两种工况下的力学响应。计算结果表明,拓宽荷载可致使地基产生显著的二次沉降,并在老路坡脚处地基内形成较大的超孔隙水压力;既有路基顶面的不均匀变形由新建路基的"盆形"逐渐发展为"倒钟形",而基层顶面的应力也逐步由压应力发展为拉应力,从而产生路基拓宽工程的特殊损坏模式-基层顶面弯拉开裂。同时,新老地基处理的强度差异对拓宽工程性状具有极其重要的影响。上海沪宁高速公路所采用的桩网复合地基,可充分减少由于拓宽附加荷载引起的二次沉降。

Based on the construction sequence of the existing highway and widening one,the differential settlement and its impact on pavement structure are introduced in this paper,and the plane strain finite element model is established.And then,the numerical analyses are conducted by considering two major computation conditions： untreated foundation and composite foundation.It is shown that due to the widening load,there are significant settlement at the top of foundation and excess pore pressure in foundation at the toe of existing fill,the deformation characteristics at the top of old subgrade change from basin feature to reverse slope,and then a special top-down tensile cracking of pavement is induced.Meanwhile,the foundation deformation-resistant capacity difference between old and widening highways has important impact on the mechanical responses of subgrade and pavement,the pile-geosynthetics composite foundation used in Huning Expressway is useful to reducing the differential settlement of old subgrade.