Installation Effects on the Capacity of Open-Ended and Closed-Ended Pipe Piles

The base and shaft capacities of piles depend on the method of pile installation, pile type, soil type, and stress state. Fully instrumented, open-ended, and closed-ended pipe piles were load tested side-by-side statically following a slow-maintained testing protocol at two sites in Indiana, USA. The piles were instrumented following a hybrid, dense instrumentation scheme with both vibrating-wire and electrical-resistance strain gauges along the entire length of the shafts. The open-ended piles were specially designed and assembled following a double-wall system to facilitate separation of the external and internal unit shaft resistances in every layer of the soil profile. The plug length ratio (PLR) and incremental filling ratio (IFR) were measured for the open-ended test piles. To gain insights on the impact of the formation and evolution of the soil plug during installation on the base capacity of pipe piles, one open-ended model pile and one closed-ended model pile were installed under similar conditions in a calibration chamber with digital image capabilities. This paper summarizes and discusses the results of the pile load tests. The load test results are compared with predictions obtained using modern CPT-based pile design methods available in the literature. An assessment of the design methods is made based on the field test results.