Shear Load-transfer Characteristics of Drilled Shafts in Weathered Rocks

In this study the shear transfer curves of drilled shafts placed in granite-gneiss rocks were investigated based on small-scale tension load tests performed on nine instrumented piles. Special attention was given to the load-transfer at the interface between shafts and surrounding rocks. For the tension load test. a constant load was applied to the pile and sustained for 15 minutes at each load level. This procedure was repeated until anticipated ultimate load was reached and total of eight load increments was applied. It is shown that the shear transfer curves can be categorized typically into two different types such as hyperbolic and elastic-perfectly plastic models. Based on the analysis, a single-modifed hyperbolic type is proposed for shear transfer function of drilled shafts in rocks through the normalization of transfer curves and linear regression analysis.