Optimization of Empirical Methods in Determining the Load Capacity of Rock Socketed Piles

Rock socketed piles have emerged as an efficient foundation support for heavy superstructures over weak soil layer present at shallow depth underlain by rock stratum. The stability of these piles is governed by the end bearing mechanism which is practically determined using pile load test as per Indian Standard codal provisions. However, the piles are never loaded till its ultimate capacity due to its catastrophic failure tendency at much lower settlement. To overcome this problem, various extrapolation techniques have been formulated whose applicability is susceptible to the strength profile of the socketed rock. This study attempts to ascertain the suitability of five extrapolation techniques, namely, De Beer's method, Tangent-Tangent method, Mazurkiewicz method, Hansen method, and Chin-Kondner method in determining the ultimate load capacity of rock socketed piles using formerly available pile load test data conducted at five locations in Khordha, Odisha region. The ultimate loads so obtained for various methods are compared for rock profiles of various locations. The trend of variation of ultimate load and factor of safety are collectively analyzed to ascertain the suitability of above techniques. De Beer method and Mazurkiewicz method have shown superior results for almost all site conditions while other methods have shown aberrations in the analysis. This study may be extended by comparing other extrapolation techniques for variable diameter piles subjected to a combination of static and dynamic loading for different site locations.