Deformation Modulus of Soil at the Tip of a Bored Pile

In this study, variation with load was analyzed in terms of the settlement/diameter ratio, of deformation modulus Kp of soil at the tip of a precased concrete pile as bored, defined as the slope of a straight line extending from the point of origin of its stress-settlement curve at its tip as determined through a vertical loading test and intersecting with such curve at the point corresponding to the settlement at each load level as applied during such loading test. Data were taken from a series of vertical loading tests conducted on 18 piles. From the study, the deformation modulus Kp was found: (1) to decrease exponentially with an increase in settlement/diameter ratio Sp/Op, (2) to range from 200 to 300 kN/m3, when ultimate load was taken for the one at which a given pile settled by 10% of its tip diameter at its tip, independent on its diameter, length, and the type of soil at its tip, (3) to be from 600 to 2,000 kN/m3 and 300 to 600 kN/m3 at settlement/diameter ratios of 2% and 4% at pile tip respectively, these settlements being deemed as reasonable criteria to determine the ultimate bearing load of a pile by means of a conventional loading test, and (4) to converge to a certain value with an increase in settlement/diameter ratio Sp/Dp, regardless of the diameter of the pile, and therefore such modulus can be identified through a loading test on a small diameter pile rather than a large diameter pile, resulting in an economy