Rock bearing resistance of bored piles socketed into rock

Abstract

In view of the large movement required to mobilise the base resistance of bored piles and difficulty in base cleaning, the end bearing resistance often ignored in current design practice that will result in excessive rock socket length. Many attempts have been made to correlate the end bearing resistance with the uniaxial compressive strength of intact rock and the RQD but it is uncertain how applicable they are to rock type in Malaysia. This paper attempts to review the applicability of the formulas from previous studies to rock type in Malaysia. A program of field tests for 13 bored piles with diameter varying from 1000 mm to 1500 mm constructed in granite was conducted to measure the axial response of bored piles, tested using static load test and high strain load dynamic test to verify its integrity and performance. The results were evaluated and compared to the predicted rock bearing resistance. Based on the result obtained, the method by AASHTO gives the best prediction of rock bearing resistance for granite in Malaysia. However the relationship between compressive strength and rock discontinuities with the rock bearing resistance showed scattered results.