Laterally loaded drilled shafts embedded in soft rock

The current design criterion for laterally loaded drilled shafts embedded in weathered Piedmont rock profiles requires a challenging effort on the part of the engineer. A substantial cost saving could be realized, while maintaining an acceptable and safe performance, if a rational method were developed for the analysis and design of drilled shafts in such a profile. In a current research project, the primary objective is to develop and validate a procedure for design and analysis of laterally loaded drilled shafts embedded in the Piedmont weathered rock profiles. A major component of this research is a field-testing program. Presented are the results of the first in a series of several lateral load tests performed on two drilled shafts 0.762 m (30 in.) in diameter embedded in Piedmont weathered rock. These shafts were instrumented with inclinometers and strain gauges. Field data obtained from the instrumented shafts were used to develop P-y curves. Field testing also encompassed the use of a borehole dilatometer to establish correlations between the rock strength and deformation parameters and potential P-y curves. A comparison is made between backcalculated P-y curves, P-y curves predicted by using Reese's method, and P-y curves from the rock dilatometer. Load-deformation results are presented and discussed for all methods used.