Pile Group Settlement Analysis for Weak Rock Foundation Sockets Designed Using a Modified Corelation Factor

Deep foundations in weak rock have traditionally been designed as friction elements, and most of the published correlations estimate the frictional capacity using shaft frictional resistance (fs) calculated from the unconfined compressive strength (UCS) of rock. Tall tower foundations in weak carbonate rocks have historically been designed using conservative correlations, and settlements are often overpredicted when conservative geotechnical deformation parameters are used, even with advanced numerical modelling techniques. This paper presents a review of a revised correlation factor to estimate fs from UCS of the weak carbonate rocks developed by back-analysis of high-capacity load 44-test dataset in the range of 100 to 320MN, and presents a case study where settlement calculations using 3D finite element modelling are compared against the load test results to check whether serviceability limits are met when the revised correlation coefficient is used to design the foundations. The case study uses the revised correlation and ground stiffness parameters based on the small-strain modulus Ed from geophysics, resulting in an overall saving of about 30 to 35% of concrete volume, thus resulting in a reduction of foundation cost and a reduction of the carbon footprint and its effects on climate change.