Small-scale testing of water-saturated wooden discs for determining the strength properties of timber foundation piles

The compressive strength properties of timber foundation piles in Amsterdam were characterised by small-scale compression tests on saturated round wooden discs. The discs were extracted from the head, middle, and tip of five spruce (Picea abies) piles dating back to 1727, 1886, 1922, and 2021. Several piles were subjected to underwater bacterial decay, causing a reduction of their load-carrying capacity over time. The amount of decay was determined with micro-drilling measurements. The results of small-scale tests were compared to large-scale axial compression tests to assess the feasibility of retrieving equivalent strength properties, considering the influence of diameters, decay, and wood knots.