Safety Evaluation Of Precipitation And Seepage In Construction Of Sand And Gravel Foundation

Sandy gravel foundation are widely distributed in our country,it is a complex foundation that often met in water conservancy engineering.Due to its complex features such as high porosity and strong permeability,resulting in a series of adverse problems to the engineering.The number of seepage accidents and failure due to the improper foundation seepage control accounted for about 40%~50% of total accidents,so it is very important to analyze the foundation seepage correctly.The dissertation introduces the south-to-north water transfer project’s strategic significance to China’s economic development,reviews the development process of foundation pit dewatering and seepage study.Starting from the factors affecting the seepage and stability of foundation pit,introduce five kind of methods that control groundwater while foundation pit is excavated,and also make a further explanation for the comprehensive utilization of water resources after dewatering.By introducing the adverse effects generated from groundwater seepage to civil engineering,doing set the stage for the necessity of later seepage analysis.In this dissertation,SG6 bid section middle route’s excavation dewatering in the south-to-north water transfer project is taken for example to study sandy gravel foundation pit seepage analysis.First accomplished of routine test of replacing and filling earth, indoor compaction test of replacing and filling earth, rolling earthwork test in the field of replacing and filling earth, relative density test of sandy gravel in downstream primary basal plane and relative density test of sandy gravel used landfill. The plentiful experimental data have been obtained. The indoor and field test skills have been added. The design requirements have been satisfied and the reliable test parameters have been also offered for seepage analysis. Then combining with test data using Vensim PLE and numerical calculate software MATLAB to analyze channel seepage.The following conclusions are drawn:First, The limited time construction drawdown unable lead to plentiful groundwater decrement, and it is already enough small so as to ignore in the region away from the canal 1500 m.Second, The various canal excavation speeds have direct effect on the maximum of groundwater discharge of permeability, but basically no influence on the end value of groundwater discharge of permeability.The above conclusions have been verified by observing the changing wells level in the distance of 1500-2000 meters surrounding construction site’s village in the actual project.