Case study of the dewatering of a major excavation in a glacial aquifer

Abstract

This thesis presents the findings of a case study of dewatering a major staged 3.5 km excavation in a heterogeneous, unconsolidated aquifer, the Mid-Kildare Aquifer. The objectives were to compile all the information available on the hydrogeological properties of the aquifer and on the dewatering project, and to analyse this information to compare the parameters predicted from the ground investigation with those back-analysed from the recorded aquifer response using traditional methods. This information was used to develop a conceptual model of the 200 km2 Mid-Kildare Aquifer and finite-element numerical models of increasing complexity until both the seasonal groundwater level variation of the aquifer, which is generally about 2 m, and the dewatering were adequately represented. The finite-element numerical model was used to assess the influence of time varying recharge and the construction sequence on the dewatering exercise.