Risk Estimation of Groundwater Drawdown in Subsidence Sensitive Areas

Groundwater drawdown induced ground subsidence is a severe problem in many regions around the world. Leakage of groundwater into a sub-surface construction, resulting in drawdown and subsequent subsidence, can lead to immense damage costs on buildings and installations in urban areas. To reduce the risk for damages safety measures can be implemented. Safety measures include design change of the construction, sealing of fractures in bedrock and permeable formations in soil, and infiltration of water to maintain stable groundwater heads. However, such measures can be very expensive and extensive investigation programs are therefore commonly realized as a basis for decision support on the need for safety measures. Since the sub-surface consists of heterogeneous and anisotropic materials which cannot be investigated in its entirety, decisions on safety measures have to be taken under uncertainty. In this thesis, a generic framework is presented on how to assess the risk for groundwater drawdown induced subsidence (Paper I). As specific tools for modelling uncertainties in the groundwater drawdown – subsidence – damage chain, a method for probabilistic modelling of bedrock levels and soil stratification (Paper II) and a method for probabilistic modelling of ground subsidence at the city scale (Paper III) are presented