Estimation & Comparison of Safe Axial Compression Capacity of Bored Cast In-situ Piles as per Indian and International Standards-Paper

Paper

Pdf Summary

The paper compares theoretical axial compression capacities of 1.2 m diameter bored cast-in-situ piles using Indian and international standards. Soil cases include cohesive clay and cohesionless sand profiles; rock cases cover moderately strong rock and highly weathered, weak rock. The methods examined include IS 2911, IRC 78, API, AASHTO, BS 8004 and Eurocode 7, with IS 14593 also used for stronger rock.<br /><br />Capacity differences mainly reflect standards’ treatment of shaft friction and end bearing, including adhesion factors, critical-depth limits, bearing caps and safety or partial factors. In clay, IS 2911 predicts higher capacity than IRC 78, while in sand IRC 78 predicts higher capacity. For clay, API predicts higher capacity than AASHTO; for sand, AASHTO predicts higher capacity. End bearing is generally a limited share of capacity in soil, particularly where standards impose critical-depth or unit-bearing restrictions. Eurocode 7 does not impose the same component limits; its design approaches produce different capacities through their partial factors. For clay, capacities rank from lowest to highest as DA1C2, DA3, DA2 and DA1C1; for sand, the order is DA3, DA1C2, DA1C1 and DA2.<br /><br />For moderately strong rock, IRC 78 Method 1 gives a higher allowable capacity than IS 14593, largely because of differences in safety factors and minimum socket length. For weathered rock, IS 2911 Annex B and IRC 78 Method 2 produce similar ultimate capacities, though IS 2911 gives a higher allowable capacity. The study emphasizes that code-based capacity estimates can differ substantially, so designers should understand each standard’s assumptions and resistance limits when selecting pile dimensions and socket lengths.

Keywords

axial compression

bored cast-in-situ piles

pile capacity

Indian standards

international standards

shaft friction

end bearing

clay and sand

rock socket

Eurocode 7