Research On Maximum Differential Settlement Of Expressway Subgrade Widening Under Traffic Load

With the economic development,the demand for expressway transportation continues to grow.The capacity of many existing highways is close to or has reached saturation,and it is no longer able to meet the increasing traffic demand.In order to resolve this contradiction,and in order to alleviate traffic pressure and provide better travel conditions for the people,more and more highways need to be rebuilt and expanded.With the development of more and more highway widening projects,problems such as staggered subgrade,instability of subgrade,uneven settlement of subgrade and cracking of pavement are gradually increasing.Based on the uneven settlement of the old and new foundation,the factors affecting the difference of the settlement of the subgrade are analyzed by using the finite element model numerical simulation analysis method and the orthogonal model experimental analysis method.First,establish a traffic dynamic load model to compare the differential settlement between the 3D model and the new and old subgrade under the 2D model.Although the three-dimensional model can highly restore the actual situation,it has little difference from the maximum difference settlement value under the two-dimensional model.Then,the new and old roadbed widening model is established,and the influence of the difference of the roadbed settlement is explained from four aspects: the height of the embankment,the width of the widening,the severity of the roadbed filling and the size of the splicing step between the old and new roadbed.On this basis,the maximum differential settlement changes under the two-fold widening and one-side widening are compared.Finally,four factors of appeal are selected to establish an orthogonal simulation test model to analyze the main factors affecting differential settlement.The orthogonal test method is used to study the maximum differential settlement value under the action of subgrade height,packing gravity ratio and joint step size at the joint.Impact.And the mathematical function is fitted to provide guidance for the future roadbed widening and reconstruction project.Taking the G4 Beijing-Shijiazhuang Expressway as an example,the reliability of the orthogonal results is verified.