In-situ partially penetrating variable head tests

Abstract

Variable head tests (slug tests) represent one of the in-situ permeability tests that can be performed to characterise the hydraulic properties of porous media. Groundwater quality remediation projects and the associated risk assessment studies have increased the need for improved methods of analysis of data collected from in-situ tests. Analysis procedures were developed in the present study for slug tests performed in monitoring wells partially penetrating confined or unconfined, anisotropic, finite depth aquifers with the ultimate goal of estimating the hydraulic parameters as accurately as possible. To this end, a new set of governing equation and boundary conditions were analysed which were free from some inherent assumptions utilised by previously established methods of analysis. The effect of skin friction, well bore and aquifer storage characteristics were incorporated. The applicability of the present model for confined and unconfined aquifers was investigated by analysing slug test data obtained from the literature. The results indicated close matches with actual field values. The effect of specific yield of the aquifer on the response of well-aquifer systems under unconfined conditions was studied. The results suggested that the wellaquifer response is influenced by the specific yield towards the later times of the test.