Geotechnical Engineering

DHARM

648 GEOTECHNICAL ENGINEERING

2. The choice of type of foundation for a given situation may sometimes involve difficult judgement;
   relative economy of possible types must be studied before a final choice is made. No rigid rules
   can be made but only approximate guidelines stated.


3. Bearing capacity of footings on sands is invariably governed by settlement criterion, while that
   on clays by shear failure.


4. The settlement of footings may be considered to consist of contributions due to immediate or
   elastic compression, consolidation and secondary compression.


5. Proportioning of several footings supporting a structure is done such that settlement is nearly
   equal for all footings under service loads, which are a judicious combination of dead and live
   loads.


6. Eccentrically loaded footings or footings subjected to moments are usually designed based on the
   useful width concept; according to this the area symmetrical to the applied load is considered to
   be the effective or useful area.


7. Combined footings may be rectangular or trapezoidal in plan shape; the latter are used when
   space restrictions due to the proximity of the property line exist, and when the column loads are
   very unequal.


8. Raft foundations are preferred on poor soils where spread footings are not practicable; they are
   designed either by the conventional rigid approach, assuming uniform contact pressure or by the
   concept of modulus of subgrade reaction approach.


9. Foundation design in non-uniform soil deposits is rather complex; especially so when a dense or
   stiff layer overlies a soft deposit; great care is required in coming to conclusions in such cases.

References

1. Alam Singh and B.C. Punmia: Soil Mechanics and Foundations, Standard Book House, Delhi-6,
   1970.


2. Bharat Singh and Shamsher Prakash: Soil Mechanics and Foundation Engineering, Nem Chand
   & Bros., Roorkee, India, 1976.


3. IS: 1080-1985: Code of Practice for Design and Construction of Simple Spread Foundations (Second
   Revision), New Delhi, 1985.


4. IS: 2950 (Part-I) 1974: Code of Practice for Design and Construction of Raft Foundations—Part I-
   Design, ISI, New Delhi, 1974.


5. G.A. Leonards: Foundation Engineering, ed., McGraw-Hill Book Co., NY, USA, 1962.


6. D.F. McCarthy: Essentials of Soil Mechanics and Foundations, Reston Book Co., Va., USA, 1977.


7. G.G. Meyerhof: Ultimate Bearing Capacity of Foundations, Geotechnique, Vol. 2., 1951


8. G.G. Meyerhof: The Bearing Capacity of Footings Under Eccentric and Inclined Loads, Proceed-
   ings—Third International Conference on Soil Mechanics and Foundation Engineering, Zurich,
   1953.


9. G.G. Meyerhof: Ultimate Bearing Capacity of Footings on Slopes, Proceedings Fourth Interna-
   tional Conference on Soil Mechanics and Foundation Engineering, London.


10. V.N.S. Murthy: Soil Mechanics and Foundation Enegineering, Dhanpat Rai & Sons, Delhi-6, 2nd
    ed., 1977.


11. H.P. Oza: Soil Mechanics and Foundation Engineering, Charotar Book Stall, Anand, India, 1969.


12. R.B. Peck, W.E. Hanson and T.H. Thornburn: Foundation Engineering, John Wiley & Sons, lnc.,
    NY, USA, 2nd ed., 1974.