Determining Acceptance Criteria to Optimise the Foundation Design and Installation-PPT Presentation

PPT Presentation

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The presentation describes how site-specific pile acceptance criteria were developed for a 110 kV substation in northern Netherlands. The foundation used 290 mm and 320 mm prestressed concrete piles, designed to penetrate dense to very dense sand. However, cone penetration tests (CPTs) could not reach the planned toe depths because the bearing layer was extremely dense, leaving uncertainty about soil conditions, pile capacity, and the risk of early refusal.<br /><br />Two test piles were driven and monitored using a wireless pile-driving analyzer. Signal matching of end-of-driving measurements estimated mobilized static capacities of 3.5 MN and 4.0 MN—well above the required design capacity of 850 kN. The observed final driving resistance was about 70 and 80 blows per 0.25 m. These results were used to calibrate the hammer, pile, and soil models and generate soil-resistance-to-driving (SRD) curves. The curves incorporated the required safety factor and reductions for negative skin friction.<br /><br />The resulting acceptance range was 20–40 blows per 0.25 m, provided piles were driven with the same 7-ton Junttan hydraulic hammer and settings used in the tests. This approach gave the structural engineer assurance of adequate capacity while allowing the contractor to stop before excessive driving resistance risked pile damage.<br /><br />During construction, the criteria were met. Piling proceeded quickly, with no reported structural damage or delays. The case demonstrates how integrating pile testing and design can reduce uncertainty, improve execution efficiency, and limit damage risk, emissions, material use, and carbon footprint.

Keywords

pile acceptance criteria

110 kV substation

northern Netherlands

prestressed concrete piles

cone penetration tests

pile driving analyzer

signal matching

soil resistance to driving

static pile capacity

hammer calibration