• David Maloney, Student, University of Washington


• Robert Holtz, Professor, University of Washington


• Glen Mann, Creative Engineering Options

The focus of this study was to increase our understanding of the testing and performance of small diameter steel pipe piles, or pin piles. Pin piles are a cost-effective and efficient foundation solution for transferring light structural loads to shallow bearing strata. The economic value of pin piles means engineers are more inclined to rely on local standards of practice instead of using load tests; this often leads to overly conservative foundation designs. This study involved testing of three 2-inch pin piles, each driven to a specific driving criterion of 1, 4, and 8 inches of penetration per minute of driving with a 90-lb pneumatic jackhammer. The piles were driven at a test site on the west bank of the Duwamish River, near the West Seattle Bridge in Seattle, Washington. The test site primarily consisted of soft to medium stiff, low plasticity sandy silt, increasing significantly to a very stiff sandy silt at about 20 feet below the ground surface. Steel reaction beams were constructed over the pin piles using drilled and grouted micropiles as reaction anchors, from which static load tests were performed to failure. Failure consisted of plunging the piles anywhere from 3-6 inches. Dynamic load tests were also performed by using a homemade 370-lb drop hammer. The Pile Dynamic Analyzer (PDA) collected the data, which is currently being analyzed with the Case Pile Wave Analysis Program (CAPWAP). Although the dynamic analysis is incomplete, results from the static load tests indicate an ultimate bearing capacity in the range of 10-14 kips, which is an increase of 2-6 kips compared to local standards of practice.

• Druebert, H. H. and Yamane, G., 1980 "Small Diameter Pipe Piles".
• Haggard, K.K., Holtz, R.D., and Mann, G., 2001 "Ultimate Bearing Capacity of Small Diameter Steel Pipe Piles".
• Vetsberg, H.G., Mann, G., and Holtz, R.D., 2005 "Penetration Resistance and the Bearing Capacity of Small-Diameter Steel Piles".
• Mann, G., Vestberg, H.G., and Holtz, R.D., 2005, “Ultimate Bearing Capacity of Small Diameter Pin-Piles and the Influence of Driving Penetration Resistance”