Civil Engineering Association

Rock-Socketed Shafts for Highway Structure Foundations

For the past 25 years, much knowledge and experience has been acquired by the engineering and construction industries on the use of rock-socketed shafts for support of transportation structures. This synthesis collected, reviewed, and organized the most salient aspects of this knowledge and experience to present it in a form useful to foundation designers, researchers, contractors, and transportation officials. The objectives of this report were to collect and summarize information on current practices pertaining to each step of the design process, along with the limitations; identify emerging and promising technologies; determine the principal challenges in advancing the state of the practice; and provide suggestions for future developments and improvements in the use and design of rock-socketed shafts. For this TRB synthesis report a literature review was conducted on all topics related to drilled shaft in rock or intermediate geomaterials. A questionnaire was developed and distributed to the principal geotechnical and structural engineers of U.S. state and Canadian provincial transportation agencies. Questions were grouped into the following categories: use of rock-socketed shafts by the agency, evaluation of rock and intermediate geomaterials, design methods for axial loading, design methods for lateral loading, structural design, construction, and field load and integrity testing.