DOI: 10.4121/7875af76-7341-49d5-8a86-80ae5da9ebb5.v1
title: Test data underlying the PhD thesis: Characterization of the mechanical properties of wooden foundation piles (G. Pagella) - TU DELFT

description: An extensive experimental campaign was conducted in this PhD research to characterize the mechanical properties along: 70 “new” full-size saturated spruce (<em>Picea abies</em>) and pine (<em>Pinus sylvestris</em>) foundation piles; 60 historical full-size saturated spruce (Picea abies) and fir (Abies) piles retrieved from two bridges in the city of Amsterdam, 100-300 years old and with different levels of decay. The data were collected from the experimental test campaign on the wooden foundation piles extracted from the soil in Amsterdam. The following methodology is adopted for achieving the main goals:The mechanical properties along the full-size “new” piles are investigated through the execution of large-scale axial compression tests on pile segments, extracted from their head, middle-part and tip. Pile segments with different diameters are investigated (ranging from 130 mm to 280 mm), with the goal of investigating the variability of saturated compressive strength and stiffness along the pile. The relationships between the saturated compressive strength and parameters characterized with visual and machine grading were investigated. On this basis, possible strength classes for the characteristic compressive strength based on visually-graded parameters were determined for spruce and pine piles. The results provide a basis for the engineering design and assessment of timber foundation piles and they can be used together with the provisions given in the new standard (Eurocode 5 2023).The second objective of this work is the detailed characterization, in terms of material and mechanical properties, of the historical saturated piles, with specific reference to the influence of bacterial decay on their remaining saturated compressive strength. The historical piles have been exposed in the soil for approximately 100, 135 and 295 years. Thus, it is possible to assess the remaining compressive strength of the piles in relation to bacterial decay after three distinct periods of service time. Large-scale compressive tests on full-size segments extracted from head, middle-part and tip were conducted to study the effect of decay along the pile. Small-scale compression tests were carried out on samples retrieved from the pile’s cross section, to study the influence of decay radially within the pile. Several techniques are adopted for this characterisation: micro-drilling measurements, computer tomography (CT) scans, and light microscopy observations.The applicability of micro-drilling measurements is studied to assess the amount of decay in the historical piles, as an alternative to the current extraction of drill cores. Correlations between the material and mechanical properties of the samples and the micro-drilling signals are investigated, to check the reliability of micro-drilling in identifying decay both from a qualitative and quantitative point of view. Based on a large database of micro-drilling signals collected from every historical pile segment, an algorithm is developed to determine the amount of decay within the pile at the position of the measurement.Two prediction models are presented: one for the saturated compressive strength of “new” spruce and pine piles, based on machine grading of their dynamic modulus of elasticity, measurable in practice with frequency response measurements. One for the direct prediction of the remaining saturated compressive strength along in-situ historical timber piles, based on the remaining sound cross-sectional area determined with underwater micro-drilling performed on the pile head.The novelty of this research lies in the characterization of the mechanical properties along the length of saturated spruce and pine piles, providing reliable saturated compressive strength values and grading specifications which enable engineers to adequately design timber foundation piles. These values can be used together with the provisions in the new Eurocode 5 2023. An innovative application of micro-drilling measurements is introduced, for the in-situ assessment of historical timber foundation piles and estimation of their remaining short-term compressive strength. This serves as basis for engineering retrofitting of timber foundations currently in use under historic buildings and strategical structures such bridges and quay walls in the city of Amsterdam. The micro-drilling approach contributes to the research framework in the city of Amsterdam, supporting testing and modelling methods for estimating decay, (residual) load-carrying capacity, and remaining service life models of timber pile foundations. This knowledge has broader applicability and potential extension to de delta cities across European countries, such as Stockholm (SE), Hamburg (DE) and Venice (IT), but also overseas locations including Boston (US).