Commonly used shapes of well foundations are as follows:
- Circular wells:
Most common shape of well foundations preferably used everywhere is circular wells. It is featured with very high structural strength and is convenient in sinking; additionally the chances of tilting are exclusively minimum. These circular well foundations are perfectly suitable for piers of the single-line railway bridges and the double-lane road bridges. But for excessively lengthier piers it turns out to be uneconomical. Thus, the maximum diameter of circular well is principally limited to 9m.
- Double-D wells:
These wells are usually employed on the piers and abutments of the bridges that are excessively long to be accommodated on a circular well of 9m diameter. These wells can be sunk easily. But considerable bending moments are introduced in the steining because of difference in pressure between outside and inside of the well. Additionally the square corners at the partition well provide maximum resistance to sinking.
- Double-octagonal wells:
These wells are considered to be better than Double-D wells in numerous aspects. Most preferably the square corners are eliminated such that bending stresses are reduced considerably. Additionally these wells provide higher resistance against sinking than double-D wells because of increased area.
- Twin- circular wells:
Two circular identical wells are sunk very close to one another such that they are held with a common well-cap. These wells are sunk simultaneously, adjacently. These wells are preferable where the length of pier cannot be accommodated on a double-D or double-octagonal well. These wells are found advantages where the depth of sinking is smaller and the soil strata bearing capacity is greater.
- Rectangular wells:
Rectangular wells are principally employed on bridge foundations with depths up to 7m-8m. In case of larger foundations double-rectangular wells can be used. The loading stresses at the steining are very high in rectangular wells.