SuperPile 2017 Online Proceedings, (DFI)
Dulles Metrorail/Silver Line (Phase 2) Drill Shaft Load Testing Program
William Billiet, P.E.
The Dulles Silver Line Phase II (DSP2) is an 11.4 mile extension of the Washington Area Metro Transit Authority's Silver Line. The three miles of elevated guideway are supported on 188 large diameter monoshafts founded within the Triassic Geologic Aged Culpeper Fault Basin. Lateral loads are produced along the guideway by transit braking, rail/structure interaction and centrifugal forces on curves. These lateral loads produce large moments at the foundation level due to mono-drilled shafts, socketed into rock, were selected to provide the most economical support of the moments and later loads are resisted by the stiffness of the shaft and the rock socket. A load testing program consisting of three Osterberg load-cell axial load tests and three lateral load tests were performed on fully instrumented test shafts. The challenge in developing the load testing program was to reproduce the effects of the extremely high design loads along the test shafts, considering the limitations of the load test equipment. Developing and executing the load test program, and analyzing the test results are discussed. The load testing program was vital to the verification of the lateral load performance of the foundation on the project and was a significant factor in the overall success of the foundation installation.
|article #2691; publication #1031 (SP-2017)|