Research On The Behavior Of Foundation Pit Dewatering Considering The Effect Of Groundwater Seepage

Groundwater is a very important factor in properties of deep foundation pit engineering; groundwater problems were inevitable during the foundation pit excavation process in moisture-rich areas. Deep well drainage method can drastically reduce the ground water level, avoid quicksand, piping and the collapse of the soil pit wall effectively, and guarantee the safety of construction and engineering quality. However, the seepage field and stress field of the foundation pit will be changed because of the changes of groundwater level, so it is necessary to study on the seepage field of foundation pit and to focus on analyzing the properties by groundwater seepage effects. In this paper, the following work has been done about these problems:Firstly, through the development process of the seepage theory, the development of groundwater seepage research at home and abroad were introduced in detail, as well as the basic theory of seepage analysis. Then, the design principle and basic methods of the foundation pit dewatering was introduced, and the applicable conditions of the water lowering method was summarized. Combined with an engineering example in Wuhan, the influence between the formula of Dupit and Theis under the steady flow theory and unsteady flow theory was discussed.Secondly, the seepage field of the dewatering in the foundation pit is simulated by computer software based on project case and the influence on drawdown and foundation settlement caused by the dewatering well arrangement, pump-out and the depth of well. Especially the influence of the waterproof curtain on the water levels of deep foundation pit. And a simplified method was proposed which was proved to be practical by the observation results of precipitation engineering.Finally, the seepage calculation theory of FLAC3D was introduced simply, and the FLAC3D was used to numerical simulation analysis an engineering project. In the condition of the same parameters such as pumping water, the seepage field of the dewatering in the foundation pit and the surface settlement around it were calculate under five different depths of waterproof curtain(0m,22m,32m,48m,54m) then the head drawdown in the stable state and the initial water level were compared. The related curves between peripheral head and the distance of leaving the foundation, between lateral head of foundation pit and curtain depth, between inside and outside head of waterproof curtain and curtain depth,between the ground settlement around the foundation pit and the distance of leaving the foundation were founded under different curtain depth. Under the situation of the depth of water curtain are 32m and 48m respectively, the head buried depth in the foundation pit with four different single well pumping water conditions were calculated and the related curve between the buried depth of head in the foundation pit and amount of ground water pumping was founded.