Vertical and Lateral Load Testing of Drilled Shafts Socketed into Rock at the Pomeroy-Mason Bridge over the Ohio River

Abstract

Drilled shafts socketed into rock have been widely used as a foundation for bridges to resist both vertical and lateral loads. Although numerous research efforts on rock socketed drilled shafts under vertical loads have been carried out, research on rock socketed shafts under lateral loads has been lacking. This paper presents the results of a testing program designed to validate the design capacity of the drilled shafts socketed into rock for both vertical and lateral loads. The test was conducted on two 8 feet (2.44 m) diameter drilled shafts. The two shafts were instrumented with Osterberg load cells (O-CellTM) for bi-directional vertical load testing, and fully instrumented for lateral load testing as detailed in the paper. The effect of the overburden soil around test shaft 2 was isolated by installing 11 feet diameter casing which was advanced to the top of rock. Test shaft 1 was terminated in shale while test shaft 2 was constructed 10 feet deeper to bear on hard siltstone bedrock. With a maximum applied load of 36,100 Kips (161 MN), the vertical load testing on shaft 2 broke the world record in 2003. The lateral load test was conducted after the vertical testing was completed, and the maximum load induced a movement of approximately 0.25 inches at the top of rock. The results of this load testing program verified the adequacy of the design assumptions and was used to verify the existing published analysis methods that are still in their early stage of development due to limited lateral load test data.