Seepage Coupled With Consolidation To Analyze Earth Pressure And Deformation Due To Dewatering And Excavation

So far Geotechnical engineers at home and abroad have made many important achievements on foundation pit. Precious design and construction experiences of excavation even ultra-deep and ultra-large foundation pit have also been accumulated. However, with economic developing, large quantity of tall buildings or some important structures have had to build on the soft soil in the areas of Coastal, which leads the foundation geological conditions to become worse. Another significant problem in the soft soil area is that the process of excavation accompanied with the dewatering problems when the excavated surface is under the underground water lever. It has been proved that the earth can produce negative pore water pressure when the pit is excavating and the soil mass excavation unloading. At the same time, dewatering in the pit will also bring about seepage of underground water; these two factors would lead the earth pressure changing over time on the concrete diaphragm wall. This paper deals with that dissipation of excess pore water pressure due to unloading effects which lead by the excavating, and earth pressure changes which is caused by the factors of seepage coupled with the consolidation also called Fluid-solid coupling effects. Do some researches on deformation law of foundation pit which is caused by consolidation. Based on the results, then to get the methods of calculating on the earth pressure and analysis the ground subsidence which considering the fluid-solid coupling effects.In the process of excavation, pore fluid pressure will reduce gradually, and the effective stress in the soil will increase, which leads soil to consolidation settlement and deformation. The consolidation of soil in foundation pit will make the soil permeability change. The article concludes the foundation pit in system, sums up the results of precious studies on the basis of mechanism analysis, examples of comparison. And do a brief introduction and conclusion to the classic earth pressure which is considering fluid and soil interaction. Derivation improved model of the earth pressure which considering the seepage force in foundation pit base on the Prandtl theory. And prepare to use the MATLAB software to write the earth pressure programs for retaining wall in deep excavation, which is to calculate the nonlinear earth pressure in theoretical study. Then to sum up a non-linear model of earth pressure that can reflect displacement and time-effects. At the same time conducts distribution pattern and size of the water pressure and earth pressure in excavation. Based on theoretical analysis of coupling seepage with consolidation, this paper have been made analysis deformation which includes the pit bottom heaving and the character of settlement and its impact factor in deep excavation at the soft soil area. It analyzes the role of soil reinforcement due to the pre-pressure and changing of earth pressure on the retaining wall when dewaters in the foundation pit, and also construes undermine caused by seepage.While carries out the consolidation effects and deformation of the retaining wall in foundation pit. Do the surface subsidence formula derivation due to dewatering and exaction in the excavation works.At the same time, using the general commercially software ABAQUS to found two pit models, one is based on the total stress theory without considering the role of water, another pit method is based on effective stress theory with considering the fluid-solid interaction effect due to dewatering and excavation. Comparison the two results which obtain by finite element analysis, receiving the changing disciplines of water-earth pressure, ground settlement surrounding the foundation pit, pit bottom heaving and the deformation of concrete diaphragm wall, which deduce by the effects of seepage coupled with consolidation during the process of foundation pit excavating accompanying with dewatering. And the change of the water pressure on the retaining structure and analysis active or passive earth pressure on the retaining structure which are also on the impact of groundwater seepage and pit supporting structure. Then get the conclusion is that the seepage force can not be ignored.