Pile capacity Testing for Reusing the existing Foundation-Paper

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The paper describes how rapid pile load testing supported the reuse of an existing foundation at a petrochemical plant in Moerdijk, Netherlands. The foundation, built in the early 1970s, was required to carry a replacement furnace superstructure about 30% heavier than the original. Records of the piles’ dimensions, lengths, and installation were incomplete, creating uncertainty about their capacity.<br /><br />Original and new cone penetration tests identified suitable bearing layers, while magnetometer CPTs indicated that the existing pile toes were at approximately NAP −15 m. Calculations were complicated by uncertain pile geometry, changing design factors, and negative skin friction from soft peat and fill.<br /><br />Rather than test the existing piles, the team installed five new 400 × 400 mm precast concrete piles in similar ground conditions and tested them about 100 m from the foundations. After a four-week setup period, the piles were tested using the StatRapid rapid load testing system. Results were interpreted with the Unloading Point Method and corrected for loading-rate effects.<br /><br />The measured static capacities ranged from 2,394 to 3,340 kN, exceeding calculated values of 1,703 to 2,177 kN by 13–53% (an average of 38%). The test results supported using a higher pile-toe resistance factor than the reduced factor in current standard calculations, and indicated that shaft resistance could also be greater than initially assumed.<br /><br />The authors conclude that rapid load tests on nearby trial piles can provide reliable evidence for assessing existing foundations when direct testing is impractical. In this case, the testing demonstrated sufficient capacity to justify reusing the foundation for the increased loads, avoiding the materials and emissions associated with replacing it.

Keywords

rapid pile load testing

foundation reuse

petrochemical plant

Moerdijk Netherlands

precast concrete piles

StatRapid system

cone penetration tests

pile capacity

Unloading Point Method

pile toe resistance