Lifecycle Liquefaction Hazard Assessment and Mitigation

Decisions about risk intervention, such as ground improvement to mitigate soil liquefaction, should be made based on the expected cost and lifecycle benefit (i.e., reduction in loss over the life of an infrastructure asset). In the jargon of performance-based earthquake engineering, vulnerability functions predict loss, and thus, are central to risk management strategy. However, field measurements of loss due to liquefaction have historically been poorly quantified, slowing the development of vulnerability functions requisite for studying the lifecycle economics of ground improvement. Accordingly, aided by engineering and economic data from the 2010–2011 Canterbury, New Zealand, earthquakes—the quantity and combination of which are unprecedented—this study proposes practical functions for predicting liquefaction-induced loss. These functions are: (i) applicable to lightweight structures on shallow foundation systems; (ii) developed as extensions to CPT-based liquefaction analytics already in popular use; and (iii) allow for lifecycle benefits to be quantitatively weighed for a range of intervention strategies. Ultimately, these functions can be used to decide whether, and how, liquefaction should be mitigated, or to demonstrate the economic feasibility of a new type of ground improvement (e.g., bio-inspired and bio-mediated technologies). Towards this end, the proposed functions are demonstrated via application to a liquefiable site in the SODO district of Seattle, USA, wherein a lifecycle cost-benefit analysis of ground improvement is performed.