The Application And Numeral Analysis Of Vacuum Preloading In Improving Soft SubSoil

With the rapid development of the economic construction in coastal areas in China, dredger-reclamation as a kind of land-reclaiming technology, which makes the silt or sand with the sea water into paste by some certain proportions and transport the paste to the assigned regions to form land after drainage and solidification, has been developed rapidly.However, the silt will deposit underground as a thick layer during the dredger- reclamation process, which can not meet the requirement of engineering as the construction foundation that built on the natural dredger-reclaiming land will has much deformation. Therefore, the natural dredger-reclaiming land should be solidified before the application for construction.Vacuum preloading as a kind of method to drainage consolidation, which has the advantage of short consolidation time, low price and simple techniques, is much suitable for large area soft soil foundation management. Vacuum preloading has been widely used in actual engineering such as port and dock with excellent solidification effect since it was first put forward by professor W.Kjellman of Sweden Royal Geological Institute in 1952. With the further research goes deeper, the Vacuum pressure will get more widely used.Based on the former research and plentiful experimental data, especially on the researching results of groundwater level change laws, this paper has deduced the new explanation of"vacuum degree"and the concept of"vacuum suction"and"vacuum seeping field". With the actual application of vacuum pressure method in a soft soil foundation management engineering and the local monitoring data observation, this paper went deep in the research of the effect on vacuum degree and pore-water pressure with the change of groundwater level, and the rule of the change of the underground water level, the vacuum degree and pore-water pressure by theoretically analyzing and numerically calculating. The land subsidence mathematical model is built by soil-water model for the area. Based on the actual engineering geological condition and hydrogeological condition of the area, theconcept model of hydrogeological condition is built. The process of the clay band which is in the aquifer releases a large amount of water that result in the compaction of soil layer and land subsidence, which was caused by pumping from the aquifer, has been simulated. This study applied three-dimensional finite-difference groundwater model-ModFlow and another modular program-IBS to simulate the water table and land subsidence synchronously, and established the mathematical model of water table-land subsidence and analyzed the result by adjusting the hydrogeology parameters for many times.