Shaft resistance of a pile embedded in rock

A rational calculation procedure is proposed for establishing the shaft resistance of a pile embedded in rock, based upon the Hoek and Brown failure model. The state of the art of the calculation of the pile shaft resistance is analysed. Nearly all the recommendations that have appeared in the technical literature, for calculating the ultimate shear strength of a shaft embedded in rock (tau(ult)) propose that tau(ult) = alphasigma(c)(k) (sigma(c); tau(ult)en MN/m(2)) where the coefficient alpha, considered as a constant dimensional value, ranges from 0.1 to 0.8, if the unconfined compressive strength (sigma(c)) is expressed in MN/m(2). In most cases, the exponent k is 0.5. A comparison is made between the results yielded and the different empirical theories that have been put forward with respect to this shaft resistance. It can generally be stated that the results obtained with this theory are reasonable for long and deeply socketed piles (high confining pressures) but the results are on the safe side in some cases where short piles (low confining pressures) are involved. This paper is a continuation of the works developed by the same authors with piles working at the tip, socketed in rock. (C) 2003 Elsevier Ltd. All rights reserved.