Remedies for tilt and shift of well

Tilt is the inclination of the axis of the well from the vertical, and shift is the horizontal displacement of the well from its intended position. The permissible tilt is 1 in 80 and the permissible shift is about 150 mm at the founding level (IRC 78). They are corrected during sinking.

Causes

Uneven dredging, obstructions (boulders, logs), non-uniform soil, uneven kentledge, sudden slipping of the well and eccentric load.

Remedial measures for tilt

1. Dredging unevenly: remove more soil from the high side and none from the low side so that the well sinks more on the high side.
2. Eccentric kentledge: place extra load (kentledge) on the high side.
3. Water jetting: jet water at the high side to reduce skin friction (or pump out water there).
4. Pulling with wire ropes (winches): pull the top of the well against the tilt using ropes anchored to piles or to deadmen, with a jack.
5. Strutting the low side against a firm abutment (props or anchor) to prevent more tilt.
6. Blasting or removing the obstruction (boulders, wood) on the high side, where it holds the cutting edge up.
7. Pushing with jacks against the sides, in sand, if only a small tilt remains.

Remedial measures for shift

1. Pulling the well sideways with wire ropes/winches anchored to a fixed anchor.
2. Excavation on the side towards which the well must move, so that the well can move into the dredged space.
3. Intentional tilt: tilt the well deliberately towards its correct position, then sink it vertically so that it comes back to position.
4. Eccentric sinking and the use of jacks against the sides.

 Tilted well       Correction
   \   \         kentledge   -> 
    \   \        dredge high side
     \___\       pull rope  <---

Measures during sinking: keep the well central with guides, sink uniformly with dredging symmetrical about the centre, check levels and verticality regularly, and use the soil information.