| 摘要 |
A prefabricated drain for vertical drainage of soil comprises an inner core 1 comprising a helix or a plurality of rings that are parallel to each other, the core being surrounded by an outer porous filtering layer 4. Protrusions 2 on the turns of the helix prevent the drain being over-compressed and straps 3 contacting each turn of the helix prevent the drain from being over-extended. <IMAGE> |
