Reliability and Sustainability Trade-Offs for Drilled Shaft Designs in Sand

There has been a paradigm shift in geotechnical engineering design from working or allowable stress design (WSD/ASD) to limit state design (LSD) to better tackle the uncertainties in design and soil parameters. Using reliability-based design (RBD) methods, designers can quantify the reliability of designs and make informed decisions to avoid excessively conservative designs. Thus, RBD can help reduce environmental impacts indirectly through optimization of reliability and performance of geotechnical structures. However, current design practice primarily focuses on achieving cost-effective and reliable designs, with limited attention paid to the potential environmental impacts associated with the designs. In particular, the relationship between reliability and environmental impacts of geotechnical designs has not been systematically studied to guide designers toward achieving sustainable designs. Among several influencing factors, the choice of reliability index (i.e., probability of failure) plays a key role in deep foundation design. Higher reliability often necessitates larger shaft dimensions, leading to increased construction material usage and greenhouse gas emissions. This paper provides a comprehensive analysis into the relationship between design reliability and global warming impact for drilled shafts in sandy soils, considering uncertainties in soil properties, applied loads, models, and shaft dimensions. Parametric and sensitivity analyses are systematically conducted using the first-order reliability method (FORM), Monte Carlo simulations (MCSs), and life cycle assessment (LCA). Charts are developed to enable practitioners to estimate global warming impacts of drilled shafts across a range of target probabilities of failure, applied loads, and design configurations.