Freeway Expansion Project In The Soft Ground Between The Old And New Roadbed Convergence Technology

China is now just in the early stage of rehabilitation & expansion of expressway, hence no detailed design and construction specification can be found within the mainland of China. In comparison with the expressway to be constructed, the works of rehabilitation & expansion is characterized by the following features: difficult & tough construction techniques and high-quality requirements etc. Especially, for the core technique along the interface between the new and existing subgrade in the softground area. The research of this technique is a new subject in our country. Therefore, it is of much bright prospect.The article has elaborated theoretical analysis and discussion focusing on the technique along the interface between the new and existing subgrade, with combination of considering the features of rehabilitation & expansion of expressway. Furthermore, a comprehensive study has been made with regard of the design and construction techniques along the interface between the new and existing subgrade. To minimize the transverse and longitudinal cracks along the interface and find the optimal design and construction techniques, the analysis & summary has been undertaken by means of the on-site experiment and surveyed data. This article has summarized some helpful conclusions. It is expected that all these experiences can help the ongoing rehabilitation & expansion of expressway projects such as Shenyang to Dalian, Shanghai to Ningbo and Shanghai to Hangzhou etc.It is strongly believed that these techniques would be successfully implemented for the actual projects, with further constant development and perfection, to effectively upgarde the quality and economize the project cost.