Design-Bid Build to Design-Build-PPT Presentation

PPT Presentation

Pdf Summary

The Duluth, Minnesota, lakefront project expanded from a 100,000-square-foot warehouse built under design-bid-build (Phase 1) to a 400,000-square-foot production and shipping addition delivered through design-build (Phase 2). Both phases used 9⅝-inch pipe piles. Phase 1 installed 632 piles totaling about 79,526 feet; Phase 2 installed 1,424 piles totaling about 158,456 feet.<br /><br />The site’s challenging conditions included contaminated urban fill, highly organic and moisture-rich backwater deposits, lacustrine sand and clay, and glacial till at roughly 100–120 feet below grade. Extensive historical records and new borings, CPT soundings, and test pits informed the geotechnical design.<br /><br />Dynamic pile testing and restrikes revealed substantial time-dependent gains in skin resistance. In Phase 1, resistance increased by 120–500% between initial driving and restrikes three to seven days later. The project team concluded that initial design assumptions underpredicted pile resistance and that longer restrike periods were valuable. For Phase 2, the team recommended 12 test piles with initial, 14-day, and 28-day testing. Resistance increased by an average of 240% by days 11–14, with a further 25% average increase from day 14 to day 28.<br /><br />Using Phase 2 testing data, the team adopted less restrictive driving criteria and reduced minimum penetration from 120 to 110 feet. Design-build PDA results supported an 11.6% reduction in average pile length, from 125.8 feet in Phase 1 to 111.2 feet in Phase 2. Production also increased from 1,900 to 2,700 linear feet per shift, despite pile-joint welding remaining the main bottleneck.<br /><br />The presentation demonstrates how dynamic testing, delayed restrikes, and collaboration between the geotechnical and construction teams can refine pile design, avoid overconservative assumptions, and improve construction efficiency.

Keywords

Duluth Minnesota

lakefront project

pipe piles

design-build

design-bid-build

geotechnical design

dynamic pile testing

restrike

skin resistance

pile driving criteria