The main methods used in civil engineering to eliminate the drawbacks due to the presence of water in the ground are divided into two groups:
1) Stop water flow methods include those systems that, once applied, prevent the water from flowing into the ground:
a) metal sheet piles;
b) concrete sheet piles;
c) concrete and plastic diaphragms;
d) injections;
e) freezing.
2) Dewatering methods include those systems that, once applied, determine a controlled lowering of the level of water in the soil.
If the water is intercepted within the excavation area, we have:
a) drainage with free embedding;
b) drainage with draining trenches;
c) drainage with booster wells.
If the water is intercepted before it reaches the excavation area, we have:
a) drainage with vertical wellpoint;
b) drainage with deep wells;
c) drainage with horizontal wellpoint;
d) welldrill drainage;
e) jet-eductor drainage;
f) electroosmosis drainage.
The table on the next page summarizes the various methods with the methods of execution and the types of soil suitable for their application.
Method | Type of soil | Execution |
Metal sheet piles | All types of terrain except for those large-sized rocky and gravelly pits | Mechanical driving by percussion or vibration |
Concrete diaphragms Plastic diaphragms |
All types of terrain including rocky ones | With clamshell buckets and bentonite sludge circulation |
Concrete sheet piles | All types of loose soil | Mechanical and water pressure piling |
Injections | All types of saturated soil, even rocky ones | With core drilling and high pressure filling |
Freezing | All types of saturated soils | With core drilling (liquid nitrogen and CaCI2 brine) |
Free draining | Carry-over and gravels | Direct suction |
Draining trenches | Stratified clays | Excavation and filling with drainage material |
Booster wells | Carry-over and gravels | Excavation and filling with drainage material |
Vertical Wellpoint | Sands, gravels, silts and clays | Pitching at water pressure and / or compressed air |
Drainage wells | Sands, gravels and rock layers | Percussion or rotation drilling |
Horizontal Wellpoint | Fine sands and stratified sands | Laying with open excavation or with soil-laying machines |
Wellpoint jet-eductor | Sands, silts and fissured soils | Piling up by water pressure, rotary drilling |
Electroosmosis | Lime, clayey silts and peat | With coring and / or driving |