Research on Progressive Stabilization Filter System of Silt Foundation around Tube Well

Table 2

Critical hydraulic gradient of different graded filters.

Serial number	Filter material	0–2 cm from the interface	2–4 cm from the interface
1	U.S. water and soil conservation agency filter media	2	4
2	Terzaghi upper covered wire filter material	2	4.2
3	Terzaghi undercover filter material	1.5	5
4	Water Research Institute filter material	0.8	5
5	Witt filter	0.8	4
6	Outsourcing coarse particle filter	0.8	2