The design of large diameter bored piles socketed into rock has received considerable attention in sedimentary rocks but has only occasionally been addressed in igneous and metamorphic rocks. Design methods based on the performance of sockets in sedimentary rocks have been proposed in literature, but it is uncertain how applicable they are to other rock types. Large diameter (> 600 mm) rock-socketed piles were used in several recent developments in I-long Kong, which involved 13 large-scale pile-load tests in various decomposed rocks. The test piles varied in length from 20 to 60 m and in diameter from 1.0 to 1.3 m. The test loads were as high as 30 MN. This provides a golden opportunity for a study of the performance of piles socketed in igneous, volcanic, and metasedimentary rocks decomposed as a result of subtropical weathering. In total, 35 pile tests (including 13 in Hong Kong) in decomposed rocks together with 44 other tests in sedimentary rocks are reviewed. Side resistance is analyzed with regard to rock type and is compared to the findings and correlations published by others. The rate of mobilization of side resistance was generally scattered in the test results, as were the general shapes of the resistance-displacement relationships. A trend line was established relating the unconfined compressive strength to side resistance for granitic rocks. During bidirectional multistage tests, a reduction in the socket stiffness was observed with the second test stage. For a given displacement, the side resistance mobilized in the second stage was less than in the first.
