The Optimal Design Of The Slab In Major Highways Of Shanghai Urban

As one of the important problems of road safety,bump at bridgehead has affected the social benefits of the highway seriously.Finding both economic and effective measures to treat bridgehead of soft subgrade have very great practical significance.They can minimize or even eliminate the phenomenon of the problem of bump at bridgehead,satisfaction the requirements for high-speed,safety and comfort of the highway and extend the service life of road and so on.To resolve these questions,except,of using a number of technical measures to minimize ground settlement and the approach roads outside their own compression settlement,setting slabs is one of the most commonly used methods.But the deal with the slab region is still not clearly defined.The slabs do not design specially in general practice,and the theoretical basis are not reasonable.So,the research in this paper aims design and calculation method of the backfill area and the slab in the bridge-subgrade transition,by using of the general-purpose finite element software--ABAQUS.First of all,this article simulation the difference between contact status of the slab and the filling and different settlement patterns of the foundation by compiling the corresponding procedures of ABAQUS;Secondly,this article discusses the influence on the backfill area of bridge-subgrade transition section of the Settlement Calculation by ABAQUS,including the elastic modulus,severe,permeability and other soil parameters;finally,it verifications the project example in Shanghai by using the methods of calculation and analysis,and then predicts the post construction settlements and optimizes the design.The main conclusions are as follows:(1)The different mechanical behavior of the status contact analysis of slab and the roadbed shows that when elastic slab supported entirely up to the subgrade soil, the plate flexural tensile stress at the end is smaller;when the cavity length is less than 0.54m,it builds the slab's stress not to affect.As the cavity length increasing,the bending tensile stress in the end of the plate significantly increases.When the slab and the subgrade soil is completely unable to empty,its status with the force is similar to simply supported plate.Therefore,the cavity length of the slab is a major factor of affecting the force status of the slab.It can be conservative by simply supported plate slab calculation of internal forces in design.(2)The performance of the slab's adaptive of foundation settlement is:the foundation settlement of the 6m length slab applies to the handling of less than 2cm at bridge-subgrade transition section;the foundation settlement of 8m slab length applies to the handling of less than 4cm at bridge-subgrade transition section,and the foundation settlement of the 10m length slab applies to the handling of less than 5cm at bridge-subgrade transition section.(3)For the low reclamation embankment in the soft soil foundation,the most important factor arising from the settlement is the settlemen of the foundation, followed by the settlemen of back filling.Therefore dealing with the differences in bridge-subgrade transition section,first of all,it resolve the settlement of the foundation,and then deal with the settlement of backfill material itself.(4) Backfill materials should be lightweight,high strength,high modulus,good permeability,and should be to extend the preloading time without the influence of the job time,so that the foundation has full consolidation.Finally,it makes the difference of longitudinal gradient bad under control by using slab effectively.