Study On The Differential Settlement And Controlling Technology Of Expressway Widening Subgrade

Many widening expressways have been constroctde in our country recently, but differentia settlement occurs universally between the new embankment and the old one, which arouses more distress on the pavement and embankment. Therefore, the comfort and speediness of vehicles are affected, the capacity is reduced, and the economical and social benefit is affected too. So the differentia settlement in widening project should be paid attention to, and efficient joint of the new and old embankment should be ensured, so it is necessary to study the differentia settlement and its controlling technology. The main achievements of this paper are as follows:(1) The differentia settlement characteristics and variational rules of influencing factorsOn the basis of investigating the expressway widening projects at home and abroad, the distress and its reasons are analyzed. Aiming at expressways at plain, combining the widening modes and practical conditions of Anxin widening expressway, selecting typical section, the differentia settlement characteristics is elaborated from these aspects such as settlement, level displacement and stress with finite element method. The variational rules of influencing factors are thoroughly analyzed, the notable degree of these factors are arranged by perpendicular test, and engineering measures are proposed to reduce the differentia settlement based on these.(2) Mechanical influence of differentia settlement on pavement structureBy establishing finite element model, the influence of differentia settlement on additional stress of pavement structure and their variety at different deepness are calculated.The rules of additional stress with different thickness and modulus in every structure layer are found out, the sensitivity of structure parameters is analyzed, and the main factor is put forward.(3) Controlling criterion of differentia settlement and its classificationBased on analysis of pavement structure, taking into account the request of structure and functionality of pavement, the controlling criterion of differentia settlement is put forward. And the corresponding classification is done combining the supporting project.(4) Analysis on controlling technology of differentia settlement and effectThe controlling technology of differentia settlement and effect are analyzed from such aspects as grade reduction of the old embankment, the dimension of digging steps, every performance of geocell and the application of percussive compaction. On basis of calculation and analysis, corresponding measures are suggested.(5) Centrifugal model test and the pave and analysis of test section Selecting test section, adopting manifold scheme, combining the theory and field test, the main technologies and effect of depressing differentia settlement are studied. The schemes of several geosynthetics mainly with geocell are firstly carried out by use of centrifugal model test and their economic analysis are made, rational technological measures are advanced.The controlling technology of differentia settlement in allusion to widening expressway at plain provides valuable reference for scientific research, designing work, construction and specifications of correlative projects, which has much economical and social benefit.