Dewatering of foundation Excavation by engineerTrip.com

Dewatering of foundation Excavation

• Excavations carried out dewatering sub-soil water.

1. Sumps and Ditches
2. Shallow Well System
3. Deep Well System 
4. Well point System
5. Vacuum Method
6. Cement Grouting
7. Chemical Process
8. Freezing Process
9. Electro-Osmosis Method 

Sumps and Ditches 

• This is the dewatering utilized in shallow unearthings soils. 
• these sumps are connected by ditches or drains of semicircular in shapes or sides flows diameter along the periphery of the excavations. 
• This is the simplest dewatering used in shallow excavations in soils
• these sumps are connected by ditches or drains of semicircular in shapes or sides flow diameter along the periphery of the excavations. 

Shallow Well System :

• in this strategy an opening of 30 cm in width, or more is drilled into the ground to a profundity not surpassing 10 cm underneath the pivot of the siphon. 
• The section pipes from a number of such wells may be connected to one common header connected to the pumping unit.
• A rock channel is conformed to the strainer tube by bit by bit evacuating the packaging tube and all the while pouring the channel material, such rock.
• Deep Well System 

Deep Well System :

·  In this framework is progressively reasonable when the profundity of exaction is in excess of 16 m or where artesian water is available. 

·     A submersible pump with a capacity to push the water up to a height of 30 m or more is installed near the bottom of the well.

Wellpoint System:

·   This is technique for keeping an uncovered territory dry by catching the stream groundwater with pipe wells crashed into the ground. 

·  In this main points system are :

1.   The well points

2.   The riser pipe

3.   The swinger arm

4.   The header pipe

5.   The pumps

• Well focuses are introduced in a bored gap yet for the most part, a these are introduced by flying. 

• After all the well centers are presented and related, the suction siphons commitment to errands.

• Well points are suitable for lowering the water table by 5 to 6 m in soils with a coefficients of permeability between 1X10`4 to 1X10`6 m/sec.

• It is basic to keep siphoning once it might end up being grievous.

Vacuum method :

• Well focuses can not be utilized effectively for depleting silty sands and other fine sands with a powerful size not exactly about 0.05mm.

• For installations of vacuum well points, a hole about 25cm diameter is format around the good points and riser pipe by  settings waters under pressure.

•  However, the pressure  is slow and it may take several weeks for the soil to become stiff.

• As the effective pressure on the soil is increased, consolidations take place.

Cement groutings :

• Groutings solidifies and strengthen the formations to increase its load bearings capacity.

• It also reduces or eliminates the flow of water through a formation.

• Groutings also reduces hydraulic uplift pressure.

 The materials commonly used for grout include :

1.     Cement, rock flour and water

2.     Cement and water

3.     Cement,  clay, and water

4.     Cement, clay sand and water

5.     Asphalt

6.     Clay and water

7.     Chemical

·         Grouting required the size depth and spacings of injection holes should be planned so as to get the best results at the minimum cost.    

Chemical process :

• In the methods, a chemical in the liquid form can be pumped into and through very small openings, which other grout cannot penetrate.

• The concoction structure boundary to the progression of water through arrangements by changing structures a fluid to a gel at a foreordained occasions after it enter the developments.