A Study on The Evaluation of Pile Bearing Capacity Factor and Adhesion Factor in IS 2911-Paper

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The study examines the bearing capacity factor (Nq) and adhesion factor (α) used to estimate pile resistance under IS 2911 (2010). Because the Indian standard presents these factors as charts without clearly identifying their sources, the charts can be difficult to interpret, digitize, and use reliably in automated design.<br /><br />The authors digitized the IS 2911 charts and compared them with models proposed by researchers and provisions in other national and international standards. They found that the Nq values for driven piles (IS 2911 Sections 1 and 3) closely follow Berezantsev et al. (1961) up to a soil friction angle of about 40°, with the remaining portion resembling Skempton (1951). For bored piles (Sections 2 and 4), the Nq chart is similar to Thurman’s (1964) method. The IS 2911 adhesion-factor chart is also similar to the one in German standard DIN 4014 (1990).<br /><br />To support faster and more reliable calculations, the researchers developed nonlinear regression equations for Nq for driven and bored piles, and for α. The models were fitted to the IS 2911 charts using NCSS software and achieved coefficients of determination greater than 0.995. The equations provide alternatives to reading values from charts, reducing manual effort and the risk of data-entry errors while facilitating automation and optimization of pile-foundation design.<br /><br />Overall, the study clarifies the likely origins of the IS 2911 factors and provides regression-based tools for applying them.

Keywords

IS 2911

bearing capacity factor

adhesion factor

pile resistance

driven piles

bored piles

nonlinear regression

pile foundation design

soil friction angle

chart digitization