Rock-socketed drilled shaft design for lateral loads [overhead power line foundations]

This paper describes the analytical studies and seven full-scale foundation load tests that were conducted to study the behavior and improve the analysis and design of laterally loaded drilled shaft overhead power line foundations partially or totally socketed in rock. Finite element analyses were conducted to develop new theoretical pressure versus displacement (p-y) relationships for the four-spring subgrade modulus MFAD model. The results of the drilled shaft tests are discussed and compared to the behavior predicted by MFAD. The Rock Mass Rating (RMR) system was used to evaluate the strength and deformation parameters of the rock strata. The foundation behavior predicted by the modified version of MFAD using these rock strength and deformation parameters and the p-y relationships developed from the finite element analyses agreed well with the behavior observed in the seven full-scale drilled shaft foundation load tests.