METHOD FOR CONSTRUCTION OF DRAINAGE SYSTEM IN WATER-LOGGED SOILS Russian patent published in 1994 - IPC

FIELD: irrigation and drainage. SUBSTANCE: soil over drain route is frozen and ditch 3 is excavated simultaneously with freezing. Freezing is carried out along walls of ditch at height of ground water crop-out. Excavation of ditch 3 is effected continuously with simultaneous laying of filtering material in form of multilayer filter. In so doing, first, strips of band of rigid macroporous filtering material 6 are placed on ditch bottom and covered with crushed stone layer 7. Then, layers of sand-gravel mixture 8 and sand 9 are laid and drainage pipes 10 are placed in them. Placed from atop is band-like microporous filtering material 11. Band strips of macroporous filtering material 6 and microporous filtering material 10 are symmetrically laid with bulge in the middle in mutually opposite sides relative to one another. Ditch 3 is backfilled with ground 12. EFFECT: higher efficiency. 2 cl, 2 dwg