Geotechnical Engineering

DHARM

776 GEOTECHNICAL ENGINEERING

(ii) The depth can be decided as the sinking progresses, since the nature of the strata

can be inspected and tested, if necessary, at any desired stage. Thus, it is possible to

ensure that it rests upon a suitable bearing stratum of uniform nature and bearing

power.

(iii) A well foundation can withstand large lateral loads and moments that occur in the

case of bridge piers, abutments, tall chimneys, and towers; hence it is preferred to

support such structures.

(iv) There is no danger of damage to adjacent structures since sinking of a well does not

cause any vibrations.

These advantages are not obtainable in the case of pile foundations, especially for large

structures.

Well foundations have been found to be economical for large structures when a suitable

bearing stratum is available only at large depths.

19.8.2Elements of a Well Foundation
The elements of a well foundation are: (i) Cutting edge (ii) Curb (iii) Concrete seal or Bottom
Plug (iv) Steining (v) Top Plug, and (vi) Well Cap.
These shown in the sectional elevation of a typical well foundation of circular cross
section (Fig. 19.10).

R.C.C. slab

Pier

Well cap

Top plug

Di

De

D

Curb

Cutting

edge

Concrete seal

or Bottom plug

D : Internal diameter

D : External diameter

D : Depth of penetration

t : thickness of steining

i

e

s

Steining

Sand filling

ttSS

Fig. 19.10 Elements of a well foundation