In general, the design of pile and pile cap shall conform to provisions of IRC:78. The various specific assumptions to be made for the design of pile and pile cap shall be as follows:
(a) The vertical load carrying capacity of the pile shall be determined based on static formula given in Appendix-5 of IRC:78-2000. The following limiting values shall be considered for computation of safe load:
- Results of sub-soil investigation shall be used for adopting the value of angle of internal friction “?” and cohesion “C” of the soil.
- Angle of wall friction ‘?’ to be taken as equal to Angle of internal friction ‘?’.
- The coefficient of earth pressure, ‘K’ shall be taken as 1.5 while calculating the safe load carrying capacity.
- The entire overburden shall be assumed fully submerged for the purpose of calculation of safe load.
- Maximum overburden pressure at the bottom of pile for the purpose of calculation of shaft friction and end bearing shall be limited to 20 times the diameter of the pile.
- Factor of safety shall be taken as 2.5
(b) The vertical load carrying capacity as calculated by static formula shall be verified by conducting initial load tests on piles conforming to IS:2911 (Part 4).
(c) The lateral load carrying capacity of the pile shall be determined by using empirical formula given in IS:2911 (Part-1/Sec-2) by limiting the lateral deflection of 5 mm at its tip considering it as fixed headed pile under normal conditions. The capacity so evaluated will be used purely for the purpose of arriving at the upper bound of lateral load capacity. This deflection limitation will not be applicable in load combination with seismic conditions for which the resulting stresses and the structural capacity of the section would be the governing criteria.
(d) Soil stiffness for lateral loads shall be taken from IS:2911 (Part-1/Sec-2), Appendix – C. Unconfined compressive strength shall be calculated from the results of Geotechnical Investigation Reports. Cohesion as calculated using unconsolidated undrained test with required modification of angle of internal friction will be used for working out unconfined compressive strength.