A section through a well foundation is shown in Fig.1. The various component of a well foundation are briefly described in the following.
Well Cap – The well cap is a RCC slab of sufficient strength to transmit the forces from pier to the body of well. It is generally kept at low water level. The dimension of the well cap should be sufficient to accommodate the pier. The recommended minimum thickness is 0.75 m.
Steining – It is the wall of well & is built over a wedge shaped portion called well curb. The steining is designed such that it can be sunk under it own weight. The thickness should be sufficient so as to overcome skin friction developed during sinking by its own weight. The minimum reinforcement in the well staining should be 5 to 6 kg/m3 of which 75 % is to be provided as vertical and 25 % as lateral ties or hoop rings. The minimum thickness is 0.45 m or 1/ 8 of the external dia. of well for brick masonry and 1/10 for wells with cement concrete. The thickness is increased by 12 cm per each 3 m depth after sinking the 3 m of steining for brick well and 15 cm for each 6 m depth after sinking the first 6 m of cement concrete well. The thickness can be computed as:
t = D/2[ 1 – √(1-4qs/ÏD) ]
Where D is the diameter of well, qs is the unit skin friction, Ï is the unit weight of concrete or Brick masonry. The thickness of the steining is a function of the size of the well. The recommended thickness is: