To determine the ultimate load capacity of drilled shaft socketed into rock under axial compression loading, it is necessary to predict both the ultimate side shear resistance and the base resistance based on field load test or/ and laboratory tests. In geotechnical engineering there are several methods proposed the relationship between rock properties (the unconfined compressive strength) and the ultimate side shears resistance and base resistance. This paper presents the review of design methods of ultimate side shear and base resistance for rock-socketed pile. These empirical functions depend on the socket type and the range of the unconfined compressive strength of rock.

The paper presents a case study of 65 pile tests under axial compression load. These piles were installed at different sites (including in situ and laboratory tests), with the unconfined compressive strength of the different rock layers ranging from 0.48 to 55 MPa (from very soft to relatively hard rock). To evaluate several empirical design methods for calculatinge the base resistance of piles embedded into rock, a comparison was made between the measured base resistance from the loading tests and the predicted values from the different empirical methods. The Zhang and Einstein method gives the best prediction when considering the number of the extreme cases; while the Vipulanandan et al. method gives the best prediction when considering the number of the conservative and non-conservative range of the measured data.