Numerical Analysis On Differential Settlement Of High Liquid Limit Clay Subgrade Expansion And Corresponding Solutions

The development of domestic economy greatly enhances people’s well-being,bringing growing numbers of cars in use.As a result of that,the traffic volume is improved,directly affecting the carrying capacity and service life of the highway.In order to meet growing needs of the highway traffic volume,it is necessary for people to widen the original embankment.While the problems of the old and new embankment splicing,stress changes,settlement and other related issues are brought about.Considering the economy and environmental protection,high liquid limit clay has to be used as the material of subgrade since it is widely distributed around highways.It is practical to study high liquid limit clay with the analysis of numerical simulation by the finite element software of highway embankment in Changzhang expressway road,from Nanchang City to Zhangshu City in Jiangxi Province,expansion project.The main work and findings are as follows:First of all,based on the statistics from indoor soil test,the graphs reflecting the relationship of compaction and water content,expansive capacity and water content,CBR(California bearing ratio)value,water content and compaction work are designed.According to the analysis of these graphs,the engineering characteristics of high liquid limit clay have been studied.It is concluded that scope of moisture in construction with direct use of high liquid limit clay is Wopt～Wopt+5%.To those high liquid limit clay which cannot be used directly as soil filling,it can be modified by adding lime and gravels.By comparing the CBR value,optimum moisture,maximum dry density and expansive capacity,adding 40%rubbles can not only establish a general foundation subgrade expansion model but also meet the requirement of economy and safety in construction.Hence the two models basing on final construction of embankment project have been set up.One is to build subgrade widening model above the normal foundation and other is on subgrade widening model above the soft soil foundationTo know the Changzhang high speed expansion embankment settlement rate,settlement rate of Layered construction,pore-water pressure,settlement rate and safety are of various subgrades in the two above-mentioned models are studied respectively by the Geostudio software.It shows that the average settlement of normal subgrade is 4.1 cm one layer and the soft one is 5.2 cm one layer.The pore-water pressure dissipation of soft subgrade takes much longer than that of normal subgrade,hence making soft subgrade spending more time on drainage and consolidation.Higher the subgrade is,more dangerous it is.This essay briefly introduces several kinds of common damage by expanding subgrades which are mainly caused by differential settlement.To minimize the damage,setting up steps and geogrids is adopted in subgrade expansion.ABAQUS software is also put into use to simulate various treatments to prove the effectiveness of them and introduce the use and construction method of all treatments.