Deformation Behaviors And Treatment Effect Of Plastic Drainage Plate And Powder Spraying Pile For Widened Expressway Embankment Over Soft Ground

In order to meet the growing traffic volume, expressway embankment widening engineering over soft ground in southeast coastal area is being carried out on a large scale,so that to form a wide width of embankment.Because the load form and loading time of new embankment are different from those of old embankment,it’t bound to result in large differences of mechanical behaviors between widened embankment and newly built embankment who have the same embankment width when the new embankment loading on the ground in the form of edge load.Existing researchs show that the key problem of expressway embankment widening engineering over soft ground it to control the differential settlements.Because of the differential settlements are mainly caused by soft ground,the choice of treatment measures of soft ground under widened embankment is important.Deformation behaviors and treatment effect of plastic drainage plate and powder spraying pile for widened expressway embankment over soft ground are studied based on the finite element numerical simulation.Accurate calculation of the settlement of widened embankment engineering is the basis of treatment measures selection for soft ground. Existing domestic industry standards, a part of the settlement computing softwares and analytical calculation methods of widened embankment settlement were summarized, deficiencies and defects of the traditional method were pointed by using Settle3D (version2.0) to calculate the settlement of widening embankment.The results show that using analytical calculation method to calculate the settlement of embankment widening can get the date of ground surface settlement usually,but can’t get the date of embankment surface settlement,and it can not reflect the interaction between the new and old embankment and the lateral deformation.Therefore,it is necessary to introduce the numerical calculation methods, such as the finite element method, finite difference method,etc.In order to study the deformation behaviors of expressway embankment over soft ground during the whole widening process, numerical models of newly built narrow embankment, newly built wide embankment and widened embankment were established based on the finite element numerical simulation. The developments of ground surface settlement, embankment surface settlement and ground lateral displacement of each model were compared and analyzed. The results show that widened embankment’s deformation behaviors are much more complicated than those of newly built embankment, settlement curve of widened embankment will change from W-type, to U-type, then to W-type. The ground under the old embankment toe lateral displacement moves to the side of old embankment, and then to the side of new embankment and later retracts. The interaction between old and new embankment should be taken seriously. Not only the post-construction settlement should be controlled, but also the settlement and differential settlement of old embankment during the new embankment construction should be paid attention to.The choice of treatment measures of soft ground under widened embankment is important to control the differential settlements. Simplified method of plastic drainage plate and powder spraying pile was introduced, refined numerical models of plastic drainage plate and powder spraying pile used for soft ground under widened embankment were established based on the finite element software PLAXIS, mechanical responses such as construction settlement, post-construction settlement and lateral displacement of each method were compared, mechanisms of the two treatment measures for soft ground under widened embankment were elaborated by the excess pore water pressure distribution of soft ground. The correctness of the conclusions of numerical simulation were verified by the results of embankment construction on-site test. The results show that although plastic drainage plate can reduce the post-construction settlement and construction lateral displacement, the effect of drag and uplift and the disturbance of construction to old embankment are significant, powder spraying pile can greatly reduce construction and post-construction settlement, and also can limit the lateral displacement effectively.According to the results of numerical simulation, through literature research and engineering research,noting that the physical and mechanical properties of soft soil and the differences between widened embankment and newly built embankment,improved and optimized suggestions and corresponding key points of construction technology were proposed to plastic drainage plate and powder spraying pile used for soft ground under widened embankment from the point of practical engineering,including the spacing, length, and location of plastic drainage plate,the spacing of powder spray pile and composable treatment methods,which might suggest lessons for the future familiar engineering.