Experimental Study on Ultimate Capacity of Large Screw Piles in Beijing

Abstract

This paper presents static load test results of ultimate uplift and compression capacities of screw piles with torque measurements performed in China, where the application of large size screw pile is currently not widespread. The 5 test piles have 114 mm shaft diameter and single/double helix of 406/508 mm diameter, and were installed in sandy silt and silty clay at a test field in Beijing, China. Torques during screw pile installation were measured by differential hydraulic pressure method which was calibrated with a wireless torque-meter. The piles were tested to their ultimate tension capacities, unloaded and then reloaded to their ultimate compression capacities. Load test results show that the screw piles have similar uplift and compression capacities. It is demonstrated that the empirical torque-capacity ratio can well predict the actual ultimate pile capacities of test piles. The “individual bearing” calculation method with consideration of shaft friction can also well predict the ultimate pile capacities of multi-helix screw piles.