The term "extreme event" is frequently applied in policy, media, and colloquial settings. The Pipeline and Hazardous Materials Safety Administration (PHMSA) Mega Rule presents requirements for natural gas transmission pipeline operators to inspect their pipelines following an "extreme weather event" or "natural disaster." However, these terms are poorly defined, and stakeholders have expressed concern that identifying the onset/cessation of an extreme event is unclear, muddying compliance. Here, we present a framework and thresholds for defining an "extreme event" as major streamflow, rainfall, or an earthquake that produces large-scale geomorphic change, rather than "associated hazards" like landslides and channel scour that directly produce ground deformation. Thresholds for streamflow and rainfall are defined in terms of frequency, where the 1% exceedance storm or flood (i.e., the 100-year event) is considered "extreme." Earthquakes are classified as "extreme" with absolute ground shaking thresholds over which the probability of pipeline damage is considered non-negligible. The definitions of "extreme event" outlined in this paper were formulated within the context of pipeline integrity management but are potentially applicable to other buried or aboveground infrastructure.
Climate change is spurring the transition from power generated by fossil fuels to power generated by wind, solar, and nuclear systems. These developments are often constructed at suboptimal sites that face geotechnical and geologic hazards requiring mitigation for operational resiliency. This paper presents the results of an extensive ground improvement program applied to a 41-turbine wind power project in the Mississippi River Delta. The site is subject to significant seismic demand from the nearby New Madrid Seismic Zone (NMSZ) and contains loose alluvial soil that is susceptible to soil liquefaction when loaded to the design Peak Ground Accelerations (PGA) of up to 0.44g. The ground improvement system was required to mitigate liquefaction-induced settlements of up to 5 in., which would render the turbines inoperable. Further, the design seismically induced shear stresses would result in significant soil shear strength reduction and lead to bearing instability. This paper discusses the design methods used to provide a robust and economical solution and summarizes the results of the post-installation cone penetration test (CPT) soundings used to validate performance. This paper is of particular importance because it provides a design framework for the effective treatment of Central United States soil liquefaction when loaded to NMSZ motions, an effort that resulted in greatly improved geotechnical performance and resiliency.
Plastics have become an essential part of human life; however, the increased dependence on single-use disposable plastic items has led to the ubiquity of microplastics (MPs) in our environment. As plastics in the environment degrade into MPs, they can spread through various means, entering the ground and causing implications for the health and well-being of the surrounding environment as well as for the properties of the soil in which the contaminants can reside. A current gap exists in the geotechnical engineering community's understanding of the effects of MPs on the dynamic properties of soils. The influence of MPs on soil behavior under dynamic loading is assessed through a series of constant volume strain-controlled cyclic simple shear tests in conjunction with bender elements (BE). This study examines the behavior of medium-dense specimens of clean Ottawa sand and Ottawa sand mixed with 10% MPs by dry mass. The MPs utilized in this investigation are composed of polyethylene terephthalate (PET) with a particle diameter range of 50 to 100 microns. Equivalent pore pressure ratio curves vs. increasing cyclic strain percentages were developed for both clean Ottawa sand and contaminated Ottawa sand. Monotonic simple shear tests are performed on the liquefied specimens following cyclic testing. The post-liquefaction stress-strain curves of clean and contaminated sand are also developed and compared. The results determined from this study improve the assessment of the liquefaction potential of highly contaminated soils in seismic-prone areas such as dense urban communities, which can reduce the potential loss of lives and resources.
Climate change poses unprecedented challenges to railway infrastructure through increased frequency of extreme geotechnical events and intense rainfall patterns, necessitating enhanced monitoring capabilities for ballast stability. This research enhances railway resilience by integrating Electrical Resistivity Imaging (ERI) with open-source Internet of Things (IoT) sensors to complement existing ballast monitoring systems. The synergy between IoT technology and ERI creates new opportunities for continuous assessment of water accumulation, subgrade deformation, and potential washout conditions in railway ballast structures. While ERI applications in ballast monitoring have been limited by contact resistance challenges, our cost-effective open-source sensor array design addresses these constraints while providing continuous monitoring capabilities across varying geotechnical conditions. The system creates a comprehensive digital twin of ballast moisture conditions and subsurface stability, delivering real-time insights into water retention patterns, ground movement, and potential ponding locations that precede washout failures. Field implementations demonstrated the system's effectiveness in identifying critical water accumulation zones and subsurface anomalies under extreme weather and geotechnical events, enabling proactive maintenance planning. This climate-adaptive approach enhances maintenance strategies by providing continuous data streams that complement routine inspections, strengthening infrastructure resilience against both hydrological and geotechnical challenges. The integration of IoT with ERI expands the toolkit available for railway asset management, offering an economically viable solution for continuous ballast monitoring under diverse ground conditions. This methodology provides railway operators with additional tools for climate adaptation, supporting informed decision-making for maintenance interventions and contributing to more resilient and sustainable rail infrastructure systems.
Internal erosion in levees is a primary embankment failure mechanism that can sometimes be caused by the presence of conduits designed to support water drainage and mitigate ponding or flooding. According to the US Army Corps of Engineers (USACE), failures often arise due to erosion along a pipe, pressurized pipe leakage, erosion into a pipe, seepage at the pipe outlet, or due to ponding. Current internal erosion inspection methods rely on closed-circuit television (CCTV) and sonar, which require site-specific equipment and travel. As a proactive alternative, ongoing efforts to develop a culvert inspection system that uses AI/ML on internal images of the pipes are promising, but more data, especially data that showcases indicators of failure, is needed to train useful algorithms. The USACE and its stakeholders are using physical modeling of culvert failure modes to identify these predominant indicators of collapse. This study investigates the internal erosion into a culvert failure mode. Using centrifuge modeling to simulate complex erosion behaviors, four tests examining the failure mode at different locations within the levee are discussed. The methodology combines visual symmetry modeling and image edge detection to show how void location affects erosion channel progression and surface propagation. Findings from these tests provide critical insights into erosion rates, facilitating improved detection and mitigation strategies and contributing to embankment safety across the US.
