Abstract: Fine sand particles entering the filter layer and borehole of dewatering well tubes in silty sand stratum will reduce the dewatering efficiency and even lead to well tube failure. Meanwhile, loss of a large number of fine particles is prone to cause progressive seepage failure and even affect the overall stability of the foundation pit. In order to ensure the dewatering works, we conducted indoor simulation test to design and compare schemes of filter screen selection. The expansion project of Qinhuai River Sluice was taken as the engineering background. Results suggest that double-layer screens of 80 meshes and 120 meshes are suitable for the dewatering well in silty sand foundation. It was applied to engineering practice and obtained good result.

Key words: fine silty sand ground, tube well filter, optimization scheme, seepage failure, sluice of Qinhuai river