While there has been considerable attention made of the design of drilled shafts socketed into rock in the context of sedimentary rock, the context of weathered/decomposed gneiss of higher intact rock strength has only occasionally been addressed. This research investigated the load-transfer mechanisms of drilled shaft socketed into weathered gneiss. For the investigation, five 1.0 m diameter drilled shafts were constructed, and static axial load tests and load-transfer measurements were performed. A comprehensive field/laboratory testing program on weathered rock was also performed at the field test sites, in order to quantitatively describe the in situ rock mass conditions. Following this, the effect of rock mass condition on the load transfer mechanism was investigated. The results of the investigation revealed that the ground investigation data regarding the rock mass conditions, which represented the degree of weathering (e.g., rock mass strength, pressuremeter modulus, Geological Strength Index, Rock Mass Rating), closely correlated with the side shear resistance of drilled shafts socketed into weathered gneiss.
Abstract