Study On Deformation Features Of Widening Of Expressway On Soft Groundwork

The widening of the expressways that are built on soft groundwork are faced with many problems, such as the interaction and differential settlement between the new and old embankments. Although there have been many engineering practices in China and abroad, The theoretical research still lag behind the engineering practices, the corresponding systematic research is still lacked. This thesis offers a comprehensive introduction to the present research in China and abroad. Focusing on interaction mechanism and deformation characteristics of the new and old embankments, a systematic research is carried out in this thesis.Firstly, with the use of elastic-plastic plane strain finite element method(FEM) , the deformation of the new and old embankment and groundwork owing to directly widening are analyzed, and the characteristics of the distribution of additional stress and the curves of additional settlement are gained. Through calculation, a further analysis of those factors that influence the settlement properties is carried out, including the width and height of the new embankment, the thickness and deformation module of the groundwork, and the degree of consolidation of the old embankment.Based on the above analysis, an analysis of reinforcement with geogrid along the joint between the new and old embankments is made, in those aspects: horizontal displacement, transverse slope ratio and shearing strength, with those factors of being taken into consideration, the effects of reinforcement are yielded. A further analysis of factors that influence the effects of the reinforcements is made, including the thickness of the groundwork, the height of embankment, the modulus of the reinforcement and the layer-number and position of reinforcements. Some insightful conclusions are reached.In order to reduce uneven settlement, the calculation of the effects of some treatment techniques is carried out, including surcharge preloading, separating wall, Dry Jet Mixing (DJM) and light embankment. By comparisons between some computational schemes, the discussion includes space distribution of pile, pile length and deformation modulus of pile on groundwork settlement. A suggestion of choosing treatment technique is put forward.Finally, with the additional stress caused by the new embankment being considered, some improvements of program for calculation of settlement is made, as being convenient application for the calculation.