Modelling the geotextile tube dewatering process

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Abstract
The geotextile tube dewatering process consists of multiple cycles of slurry filling and drawdown in order to achieve a desired final volume reduction and solids concentration increase. Relatively simple relationships have been developed in the past to calculate these final volumes and solids concentration values, but the rate of volume reduction and solids concentration increase (i.e. the time periods over which these occur) requires a more sophisticated analysis and modelling approach. The paper develops an analytical model that accounts for dewatering behaviour over multiple dewatering cycles. The model is based on the maintenance of a mass–volume balance at all points in time. Fundamental to the analytical model are two empirically derived dewatering parameters that characterise behaviour during the filling and drawdown phases. Two full-scale field test cases that involve the dewatering of gypsum slurry and contaminated sediments are presented to demonstrate the validity and accuracy of the analytical model. Very good agreements are obtained for the profiles of geotextile tube heights with time, incoming and exiting volumes and final solids concentrations when comparing the modelled results with the actual results.