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

In expressway widening, sub-grade difference settlement is inevitable. How to ensure thedifferential settlement’s control standards and take action to reduce the differential settlementbetween new and old ground become the key problem of expressway design and construction.In this paper, the finite element software ADINA is used to seriously analyze the settlementdeformation and controlling measure of the expressway widening sub-grade, the conclusions arelisted as follows:1. The finite element software is used to establish the differential settlement calculationmodel of expressway widening project. Then analyze the differential settlementcharacteristics’ change before and after the subgrade widening from the following fouraspects: the embankment and foundation’s vertical displacement, horizontal displacement,vertical stress and shear stress.Then in-depth analyze the differential settlement rules causedby the impact factor such as the width and height of embankment, embankment filling’sparameters, foundation material’s modulus and so on.2. Finite element method was used to calculate the stress states of pavement under thedifferential settlement, the influence of pavement structure parameters on additional stress isanalyzed, and the sensitivity of structure parameters with orthogonal design is introduced. Theresult is that the thickness and modulus of the grass-roots are the main factors to affect theadditional stress of the pavement layer.3. To determine the control standards of new and old roadbed’s differential settlement,firstly take the pavement structure’s functional safety into consideration, using the CementStabilized Macadam’s spliting tensile strength as a failure criterion, anti-calculating thedifferential settlement’s limit of the new and old roadbed; Then considering the roadmaterial’s fatigue failuer to calculate the material’s allowable tensile stress, and using it as adestruction standard to anti-calculate the differential settlement’s limit of new and old roadbed.Finally, considering the combined effect of them and using their weighted average as the finalcontrol standard of new and old roadbed’s differential settlement.4. The finite element analysis software was used to set up foundation settlementcalculation model. Through fitting the foundation settlement curve and exerting it to the pavement structure bottom as a restrain condition, to analyze the settlement property of theembankment surface and anti-calculate the limit value of the foundation’s differentialsettlement. Finally, the control standard of differential settlement of the foundation isobtained.5. Using numerical analysis methods to analyze the differential settlement’s controlmeasures in expressway widening project, the result shows that the application of theprestressed pipe pile composited foundation has a good effect on controlling the differentialsettlement. Based on this, this paper comparative analyze the pile length, pile modulus, pilespacing, cushion material modulus and the grille material modulus’s effects on reducing thesettlement.