Dewatering Methodsmitpolytechnic.ac.in/.../SEM-3/BCO/PPT/DewateringMethods.pdf · 2018-04-19 ·...
Transcript of Dewatering Methodsmitpolytechnic.ac.in/.../SEM-3/BCO/PPT/DewateringMethods.pdf · 2018-04-19 ·...
CIVIL ENGINEERING
Dewatering Methods
Methods of Dewatering
Ditches & sumps
Well point system
Shallow well system
Deep well system
Vacuum method
Electro-osmosis method
1. Ditches & Sump
Ditches & Sumps
• Simplest form of dewatering in shallow excavation in coarse grained soil.
• Shallow pits sumps are dug along the periphery of area drainage ditches.
• Water flows under gravity on the slopes.
• To avoid piping in the sump bottom because of upward flow an inverted filter is placed at bottom of sump.
Well Point System
Well Point system (cont….)
Well Point System
• More complicated than previous method,
• Flow is under gravity.
• Well point which is perforated pipe .5 – 1 m long & 5 – 8 cm in dia. is used.
• Conical steel drive point is attached at lower end of pipe with neoprine ball valve to allow jetting of water to pass through it for driving.
• Well points placed in a ring or row.
• Well points placed by jetting water through nozzle.
• Depth – 6 m, Spacing – 1-2 m.
Well Point system (cont….)
Deep Well System
Deep Well System
• Depth is more than 16 m.
• 15 – 60 cm hole is bored and casing with long screen 5 – 25 cm is inserted.
• Submersible pump with capacity ht 30 m pumping inserted near bottom.
DEEP WELL SYSTEM
• Used for fine grained, non cohesive soils like silty sands & other fine sands.
Electro-osmosis method
CIVIL ENGINEERING
COFFERDAM