Using hydrogeological numerical modelling to predict drainage to excavations – findings from four Norwegian case studies

Abstract

Urban ground work such as deep excavations performed in soft clay may cause damage to neighbouring buildings and structures as a consequence of settlements partly caused by drainage. The costs related to settlement damage can be substantial and there is a considerable potential for reducing these costs. To assess the risk of drainage caused by a particular set of construction methods, as well as the effect of various mitigation measures, it is necessary to quantify the expected groundwater drawdown in the zone of influence surrounding the groundwork site. This may be done with hydrogeological modelling. As part of the work towards general recommendations regarding the use of hydrogeological numerical modelling to predict the pore pressure reduction caused by drainage to excavations, four modelling cases are presented and summarised. The case studies vary from being purely research-based with the purpose of assessing a model's ability to predict or replicate pore pressure reductions, to being part of consulting work with the purpose of assisting in the decision-making regarding the use of mitigation measures.