Abstract
This paper describes a horizontal finite element technique which can analyze a confined groundwater flow around a partially penetrating cut-off wall. A partially penetrating cut-off wall is widely used in the construction of dewatering systems. Since the flow becomes almost vertical on the wall, a vertical two-dimensional or axisymmetric analysis is used to analyze the flow in its vicinity. A horizontal two-dimensional analysis is a suitable method for designing the arrangement of pumping wells and their operations, but it can only be applied to cases with a completely penetrating cut-off wall or without any kind of cutting-off structure. In the method presented here, the effect of the wall is modeled by low permeable elements whose permeability is determined by a theoretical formula. To obtain reliable results from the horizontal seepage analysis, all the nodes must be placed at points where the flow is almost horizontal. Therefore, the elements of the cut-off wall should not be too small. The results of vertical analyses show that the distance between the wall and the nearest node must be equal to the penetrating depth of the wall or larger. Additional calculations are necessary to estimate the groundwater level on the wall because no nodes exist there. Another theoretical formula is used to obtain it from the groundwater level around the cut-off wall elements and the flow rate through them. The results obtained with this method are shown and then compared with a solution from a three-dimensional analysis. It is concluded that the proposed technique is applicable to both steady and unsteady analyses.
