旧路拓宽地基差异沉降形成机理及控制对策

依托沪宁高速公路(上海段)拓宽工程,选取典型断面,应用分层总和法进行特征点位的地表总沉降和差异沉降计算,并与有限元计算结果进行比较,确认分层总和法适用于旧路拓宽沉降计算。基于分层总和法的基本原理,针对道路拓宽工程的荷载形式,综合分析初始自重应力场、一次附加应力场和二次附加应力场的分布特征,以及应力水平与压缩模量的关系,指出一次附加应力和二次附加应力相向增长的叠加效应是导致旧路边坡区域浅层地基差异沉降显著的主要原因,土层压缩性高是导致深层地基差异沉降的主要原因。结合道路拓宽工程的施工特点,指出旧路路面区域饱和软土层差异沉降控制应通过新路拓宽区域地基处理改变其二次附加应力场分布,降低二次附加应力水平,减小总沉降量以控制差异沉降。

Mechanism and Control of Differential Settlement of Widening Road Foundation

The total and differential settlements of representative sites were computed with layer wise summation method in conjunction with typical section of Shanghai-Nanjing expressway.The coincident results with layer wise summation method and finite element method approve the applicability of layer wise summation method in analysis of differential settlement of road widening.Furthermore,based on the basic theory of layer wise summation method,under the condition of widening road load,the distribution of gravity stress field,firstly additional stress field,and secondly additional stress field,and the relationship between compression modulus and primary stress were analyzed.The conclusion shows that,the remarkable differential settlement between the top and bottom of existent embankment slope is caused by the opposite increase of primary and secondary additional stress,and the differential settlement of deep-seated foundation results from the high compressibility mainly.Finally,it was advised that the differential settlement of deep-seated saturated soft clay under the existed pavement should be controlled by changing the distribution of secondary additional stress field and reducing the stress level.