Determination of dewatering behavior of slurry in multiple filling cycles for one- and two-dimensional filtration test methods

Efficient dewatering of fly ash slurry is critical for minimizing storage requirements, improving material handling, and enhancing ash management performance. This study investigates the dewatering behavior of Seyitömer thermal power plant Class F fly ash under repeated filling cycles using one-dimensional (1DFT) and two-dimensional filtration test (2DFT) systems. A novel 2DFT apparatus was developed to independently quantify radial and vertical filtration, enabling closer simulation of full-scale geotextile tube drainage. The influence of three anionic polymers with varying molecular mass and charge density, combined with 1% synthetic fiber addition, was evaluated. Results show that repeated filling cycles significantly modified filtration mechanisms. In the 2DFT system, successive fillings reduced radial filtration and increased vertical filtration. Approximately 85% of test cell capacity was reached after the fifth filling stage, beyond which efficiency gains diminished. Polymer characteristics significantly influenced filtration performance. Fiber addition enhanced vertical filtration rates in the 2DFT system but did not significantly affect total filtration duration. In contrast, fiber addition reduced dewatering time in the 1DFT system by up to 42%. These findings highlight the governing roles of cyclic filling, additives, and filter cake evolution. The proposed 2DFT system provides an improved experimental basis for predicting and optimizing geotextile tube dewatering.