Characteristics And Effects Of Improving Large Area Soft Ground By Vacuum-surcharge Preloading Method

As a new method to improve the soft ground, the vacuum-surcharge preloading method has been used widely in civil engineering. But the theory of vacuum-surcharge preloading method develops more slowly than its engineering practice. Many problems have not been solved yet.Based on the literature review of vacuum-surcharge preloading method to improve the soft ground, combined with the project characteristics of Wugang Port, the data measured from monitoring, field test and laboratory experiment, it was studied that the characteristics and effects of large area soft ground improvement through vacuum-surcharge preloading method .Firstly, the construction technique of vacuum-surcharge preloading method is introduced in detail, then some improvements of construction technique were suggested.It was investigated the characteristics and effects in improving large area soft ground with vacuum-surcharge preloading method based on the combined analysis of the data measured from monitoring, field test and laboratory experiment. A pressure box-culvert near the reinfoecement region needs to be protected, cement mixing piles were adopted and the good effects are achieved.The plane-strain finite element method was used to simulate the improvement of large area soft ground by vacuum-surcharge preloading method. In the numerical simulation, according to the equivalent transform relationship between sand-drain foundation and sand-wall foundation, the 3-D problems are transformed into the 2-D plane-strain problems, at the same time, the well resistance and smear were considered. After the data calculated through the FEM and data measured from monitoring are compared, the difference of improvement effects between vacuum-surcharge preloading and surcharge preloading are pointed out. The results show that based on the Biot consolidation theory, FEM is feasible in the numerical simulation of vacuum-surcharge preloading. Furthermore, under same geological conditions vacuum-surcharge preloading method has significant advantages than surcharge preloading in construction period and effect.