Editorial Note – Issue 3 (2018)

Abstract

Dear Journal readers, we are pleased to present a truly international issue of the DFI Journal with a particularly practical focus on foundation design and a collection of great case studies. Our issue begins with the 2018 DFI student paper competition winner, Alexandre Almeida, a graduate student at Ryerson University in Toronto, Canada. Alexandre and his advisor, Professor Jinyuan Liu, both in the Department of Civil Engineering, studied a total of 47 full-scale micropile load tests to determine the most suitable design method to predict the geotechnical capacity of micropiles in Ontario soils. The study revealed the Federal Highway Administration (2000) method, modified with a consideration of diameter expansion parameter, as suggested by Bustamante and Doix (1985), to provide the most reasonable estimations for the geotechnical capacities in Ontario soils. Alexandre Almeida presented his work in the Young Professional session during the 43 Annual DFI conference in Anaheim, California. Moving across continents, from Canada to Turkey, Chiarabelli, Miranda, and Pagliacci, describe the technologies and performance controls utilised to provide a special geotechnical engineering solution for the Galataport Project, in Istanbul, Turkey. The comprehensive project includes the construction of diaphragm walls, deep foundation systems, liquefaction mitigation, and implementation of dewatering systems. Two sites are described in the paper, while one of the sites also required the preservation of historical buildings on site. The paper presents valuable details from design to construction and highlights the use of state-of-the-art technologies for ground improvement on large areas of construction space. In addition, results of in-situ and laboratory tests carried out on the improved soil during the preliminary field trial test and after the completion of work are presented. Jamie John Crispin, the runner-up award winner of the 2018 student paper competition, and his Ph.D. advisor Professor Colm Leahy, both at the University of Bristol, provide a closed-form analytical solution for the derivation of interaction factors between piles in a group configuration embedded in inhomogeneous soil. The method is suitable for implementation in a designoriented software package and design charts have been provided by the authors for use in hand calculations. In addition, the authors developed a simplified methodology which, combined with an error correction factor, reduces the discrepancy between the simplified method and the complex analytical solution to less than 10%. This analytical tool is ideal for most practical configurations and has shown to have good agreement with experimental results. Crispin received his award during the 43rd DFI annual conference in Anaheim, CA. Spagnoli, Tsuha, Oreste, and Mendez Solarte present a sensitivity study on the uplift capacity of helical piles with different helix to shaft ratios. Two uplift capacity equations and two torque models were considered by the authors. The soil properties have been selected to simulate typical values offshore North Sea clays. The analyses were performed in terms of undrained conditions to simulate the torsional resistance during installation and the short-term pile capacity. The authors also performed a Montecarlo simulation to assess the variability of the geotechnical parameters for assessing the design depth. Results of the comparative analysis indicated that a potential application of helical piles in an offshore environment (aka, for the pile diameters considered in this study) is highly dependent on the geotechnical models used to calculate the depth and the torque. This issue closes with a technical note by Siegel, Day, Turner, and Faust, who present a local relationship for the end resistance of continuous flight auger piles and drilled displacement piles for San Francisco Bay area clays. Fully mobilised end resistance from fifteen high quality axial compression loading tests performed on cast-in-place piles are compared to the average net cone resistance for one diameter below the pile tip. The interpretations of these test data indicated that the accepted approach using a bearing 2018/19 DFI Board of Trustees