Interpretation of high pressure pack tests for design of impervious barriers under high-head conditions

High pressure packer test (HPPT) is an enhanced constant head packer test widely applied for characterizing the permeability or coupled hydromechanical properties of fractured rocks under high water pressure condition, but it remains an issue about how to choose a representative quantity from the test data for the design of impervious barriers in high-head geotechnical projects. In this study, the typical type curves of HPPTs are summarized and related to the intactness of rocks, flow condition in fractures and the possible hydraulic fracturing phenomenon in the tested rocks. Based on an interpretative model recently developed for HPPTs, a criterion is proposed to determine a proper permeability rate from the HPPT data for design of grout curtains by taking into account the type curves and the transition of flow conditions, and is applied to illustrate the implication of the proposed criterion for the design of impervious barrier in a high arch dam foundation. The proposed criterion could be of significance in the design of impervious barriers for reducing the risk of leakage in rocks under high water pressure condition.