Research Of Technique And Application Of Expressway Widening Project

At present, with the rapid development of society and economy in our country, the traffic volume is largely increasing. Also the constructed double direction-four roadway expressways in 1990s couldn't fit the quickly increased traffic, which needs widening and improving. Moreover, quite a lot of these expressways have been constructed on soft ground. Two pivotal problems of widening the used expressway on soft ground must be solved. One is to decrease the uneven settlement between the old and the widening section, the other is to reinforce the structural association between the used & reconstructed embankment, and make them entire.The selection of reasonable foundation treatments to reduce the uneven settlement between the used and reconstruced embankment is a crucial problem to ensure the engineering quality. Geosynthetic-reinforced and pile supported system can be used as an effective treatment in the process of widening the used expressway on soft ground. Soil arching, membrane/plate effect and stress concentration are identified as the system's mechanisms. The GRPS system can increase the bearing capacity of soft ground and reduce the settlement of the subgrad, and greatly reduce uneven settlement of the used and reconstructed embankment. In addition, grouting in the joint of used and reconstructed embankment can enhance the structural integrity. The practice indicated that this foundation treatment has advantages of fast and convenient construction, no effect on the traffic and cost-effective etc.In this paper, based on a project example, by using finite element software PLAXIS, the author analyzed the effects of different treatments of widening the used expressway on soft ground which reducing the uneven settlement of the used and reconstructed embankment with the theory of soil mechanic. According to the study of uneven settlement, deformation characteristics and settlement rule of the widening embankment, the author systematically analyzed the mechanism of GRPS used in widening the used expressway, which can provide the theoretical evidence for practical project, then presented a new and rational foundation treatment technique of widening expressway in soft ground.