Hydraulic Conductivity Evaluation of Vertical Cutoff Walls Bearing Filter Cake From Slug Test Analysis

Abstract

The hydraulic conductivity of a vertical cutoff wall can be estimated through a slug test analysis. A filter cake is a thin and impervious layer formed on the interface between the vertical cutoff wall and the natural soil formation. The conventional line-fitting methods for a slug test analysis have never considered the presence of the filter cake. Therefore, results of a slug test analysis using the line-fitting methods for the vertical cutoff wall is believed to be inaccurate due to the effect of the filter cake. In this study, the hydraulic conductivity of the filter cake was evaluated using a modified fluid loss test. The result of the test indicated that a very low hydraulic conductivity is an important characteristic of the filter cake. The slug test analysis with the consideration of the filter cake in the line-fitting method was then employed to estimate the hydraulic conductivity of the cutoff wall in a case study. Result of the case study proves the significance of the filter cake in the estimation of the hydraulic conductivity of a vertical cutoff wall through a slug test.