Experimental Study On Freeway Soft Subgrade Reinforced By Vacuum & Surcharge Preloading Method

Littoral fades and fluvial facies depositional soft soil distributes widely in the Zhujiang River Delta of China. The long highway on soft soil foundation is hard to dispose, and the construction cost on it is much higher, so soft soil roadbed treatment has become the key technical of the road construction, and the technical level relates to the economic and social returns of the investor. The "normal" sand drain preloading treatment can not reduce total settlement, as well as post-construction settlement and non-homogeneous settlement. Furthermore the cost of composite foundation is too high. Vacuum & surcharge preloading method is a practical, economic, reliable large range soft foundation treatment method. The stability in the loading procedure is good, and post-construction settlement and non-homogeneous settlement are little.But the use of vacuum & surcharge preloading method is few. The reasons are below.(1) Vacuum & surcharge preloading method is always used to treat large range of soft surbgrade, however soft subgrade is a lathy area, this effect the treatment effect.(2) The number of cases study of soft subgrade treated by vacuum & surcharge preloading method is few. Many technical problems are not solved yet, such as sand layer between the sand dains.(3) Lack of synthetical analysis on economic efficiency and treatment effect.These limit the application of vacuum & surcharge preloading method. Aim at these problems, much researches are done based on the Taisan working section of Guangdong Western Seashore Highway. Main contents are listed as below.(1) Whole data of experiment on site or laboratory test is aceived, as can offer nessesary experiment material to the theory research and numerical calculation.(2) Research on the reinforcement mechanics and strength increasing mechanics of the vacuum & surcharge preloading method.(3) Through camparing the reinforcement effect, the construction procedure and the technical economy with sand drain preloading method and various composite foundation methods, evaluate the vacuum & surcharge preloading method.This paper gets a further understanding of the reinforcement mechanics, promots the development and progress of new technology of soft subgrade treatment and accumulates precious experience.