Rock socket transmission line foundation performance

A major goal of overhead transmission line design is to achieve a minimum cost for a given level of reliability and safety. The greatest uncertainty in this process is in foundation design. Recognizing this opportunity to improve the economics of transmission line design, the Electric Power Research Institute (EPRI) has sponsored, since 1977, a comprehensive program of activities in foundation design. Since little high quality foundation test data existed, a task involved performing well documented full-scale load tests of drilled shafts and direct embedment pole foundations for single transmission line poles partially or totally socketed in rock and subjected to high lateral forces and overturning moments. A summary of the results obtained for fourteen load tests is presented. Based on the load tests, a provisional design guideline is also proposed