Study On The Different Settlement Of Subgrade In Highway Widening Project

Highway widening engineering can not only ease the traffic pressure, but also save investment. But with the development of highway widening project, problems as embankment instability and pavement cracks has become increasingly exposed. The reason is mainly due to the excessive different settlement between the new and the old subgrade, which occurs with improper design and construction. In view of the different settlement between the new and the old subgrade, combined Hang Jinqu highway widening project, Using theoretical analysis method and ANSYS finite element software, the paper analyzes the influence factors and control measures of the different settlement of the new and old subgrade.On the basis of investigating the influence factors and control measures of subgrade’s uneven settlement both at home and abroad, this paper preliminary analyzes the existence problems of road widening.This paper uses theoretical analysis method to reckon the foundation’s additional stress formula causing by the new subgrade, and calculates it to find out the stress distribution in the old and new foundation. In order to study the different settlement between the new and old subgrade.Using ANSYS finite element software to establish the numerical model of the new and old subgrade, this paper analyzes the influence of the width, height and the new subgrade material on the uneven settlement between the new and old subgrade. Results show that the different settlement between the new and the old subgrade increases with the rising of the width, height and the widening subgrade material’s weight.The paper uses ANSYS finite element software to establish vehicle load model to analyze the influence of static and dynamic vehicle loads on uneven settlement. Results show that: the influence of dynamic vehicle load on the different settlement is greater than the static vehicle load; The dynamic vehicle load’s speed has little effect on the different settlement of the new and old subgrade, and the traffic flow and vehicle weight have bigger influence on the different settlement, the different settlement increases with the increase of the traffic flow and vehicle weight.Combined with Hang Jinqu highway widening project, this paper proposes reinforcement measures such as excavation steps, geocell and retaining wall. Then analyzes the applicability of the three measures with ANSYS to provide basis for design. Results show that the effect of geocell on reducing the different settlement between the new and old subgrade is not obvious, and the combined action of excavation steps and retaining wall can effectively reduce the uneven settlement. In addition, the paper gives the matters need attention during construction process in order to provide guidance for construction.