Risk management of groundwater drawdown in settlement sensitive areas.

Abstract: A new method for estimation of risks at settlement calculations is presented. By quantifying uncertainties of settlement calculations, it is possible to make risk analysis and to compare the costs of risk reducing efforts with the benefit these efforts would lead to. The settlement estimations are done by combining uncertainties about soil data, groundwater drawdown and settlement calculations. This master degree thesis describes how the groundwater drawdown is estimated using a numerical model. The model reflects the groundwater decrease around a drainage well with respect to estimated groundwater recharge, dependent on the geology and precipitation. There are four parameters in the model which are connected to soil properties and precipitation; hydraulic conductivity for clay, hydraulic conductivity for till, hydraulic conductivity for sand and mean annual net precipitation. Drawdown is estimated in a deterministic and a probabilistic model, where the probabilistic model uses stochastic parameter values in a Monte Carlo simulation. The risks concerning settlements are found when the groundwater model is integrated with a soil model and a settlement model. When integrated, the new model estimates risks related to all three separate models. Results of groundwater drawdown and ground settlement estimations are spatially presented in a sensitivity and risk analysis. By finding and comparing the most influencing parameters of the settlement, project decision makers will have an easier task deciding on what further measures should be focused on.