Alteration of the Permeability Coefficient by Back Analysis of the Dewatering Pumping Data

One of the design procedures for determination of a dewatering method for excavation of a construction pit beneath groundwater table is the numerical modeling. In this method, results are extremely dependent on the value of ground layers hydraulic conductivity. This parameter could be affected by various sampling, testing and judgments, and this leads to error in the calculation result. In order to evaluate a realistic value of the permeability and, therefore, more accurate calculations, the back analysis of the pumping data during stage construction of the excavation could be helpful. This method is described in this article and results for a case history are evaluated. Observation during construction and good agreement between predictions with recorded data show the applicability of this method. This method - especially in regions with coarse-grained sub-layer with low fine contents - is useful because, in these cases, the transfer of the fine materials by water seepage could lead to the increase in permeability and discharge.