Sinking of the Well Foundation

The Sinking of the Well Foundation is carried out through the following Steps.

  • Laying of Curbs, Sinking of the Well Foundation

In dry ground excavate up to 50 cm in river bed and place the cutting edge at the required position. If the curb is to be laid under water and depth of water is greater than 5 m, prepare Sand Island and lay the curb. If depth of water exceeds 5 m built curb in dry ground and float it to the site. A typical sand island is shown in Fig.1 below.

a typical sand island

Construction of Well Steining, Sinking of the Well Foundation

The steining should be built in short height of 1.5 m initially and 3 m after a 6 m grip length is achieved. The verticality should be maintained. The aim of the well sinking is to sink the well vertically and at the correct position. The following precautions are to be taken as far as possible.

Precautions

The following precautions should be taken during well sinking.

  • Outer surface should be regular and smooth.
  • Radius of the curb should be 2 to 4 cm larger than the radius of the steining.
  • Cutting edge should be of uniform thickness and sharpness.
  • Dredging should be done uniformly on all sides.

Sinking Operation

The following operation is carried out while sinking the caisson.

  • Excavate material under the inside of well curb mechanically or manually
  • Allow the well to remain vertical.
  • Up to a depth of 1 m, excavation underwater can be made manually. When the depth of water exceeds 1 m excavate by Jhams or grabs.
  • When well goes on sinking skin friction increases and weight of well decreased due to buoyancy.
  • When the well does not sink, sunk by applying kentledge. If this operation is not sufficient jet outside the well or grease the outside. A typical loading on steining by kentledge is shown in Fig 2.
  • Go on adding sections of steining (2 to 5 m in length) up to the required founding strata.

loading steining by kentledge

Problem of Sinking, Sinking of Well the Foundation

Generally the following problems are encountered while sinking a well.

Tilt and Shift- Adopt the following measures if tilt exceeds 1/60. Dredge at the higher side. Not effective at greater depths. This is shown in Fig.3 and 4 below.

dredging the wall 1

 

dredging the wall 2

Make a hole on steining on higher side, hole is made near the ground level and excavation is carried out by diving. If possible de-water and excavate on the higher side. This is shown in Fig.5 below.

Construct eccentric welded framed bracket and load the platform thus made with 400 to 600 tons load. This is shown in Fig.5 below.

eccentric loading

Jett on the high side of well. Excavate under cutting edge by dewatering or by divers.

Insert wooden slippers or hooks under the cutting edge. This is shown in Figs.6 and 7 below.

provision of wooden slipper

 

hooking the well

Pull the well. This is shown in fig.8 below.

pulling the well

 

Strut the well. This is Shown in figure 9 below.

strutting of the well

Push the well. This is shown in figure 10 below.

pushing of thw wellMore article on well foundation

  1. Component parts of well foundation
  2. Design of Pile Foundation | Efficiency of Pile group

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2 Thoughts to “Sinking of the Well Foundation”

  1. sharad funde

    we are constructing a intake well. inside reservoir area. now it is standing on rock we have to go another 10 meater depth from reservoir bed level. we facing lot of problems. because we not succsed to full diwatring. and strarta also hard divers are working under the water but progress is very low. what we do please suggest to us.

    thank you.

  2. Manoranjan Swain

    Why wells are tilting during well shink foundation…?

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