Coupled Multichannel Analysis of Surface Waves and Electrical Resistivity Imaging Methods for Assessing Sinkhole-Impacted Railroad Embankment: Case Study

This study characterizes a sinkhole-impacted railroad embankment site through a comprehensive geophysical investigation encompassing eight electrical resistivity imaging (ERI) lines, four multichannel analysis of surface waves (MASW) lines, and three LiDAR datasets. Geophysical data from the coupled ERI and MASW at the south embankment mid-slope and toe revealed low resistivity (<50 Ω·m) and low shear-wave velocity (Vs) to depths of 25 to 30 ft, indicating moisture-weakened or void-prone zones. Increased Vs values beyond a 30 ft depth indicated stiffer soil or bedrock. Confined moisture pockets were highlighted along the sinkhole parallel to the slope’s toe. Widespread low-resistivity zones and low Vs were found at the mid-slope and toe to 30 ft, suggesting saturated, softened zones in those areas. Low resistivity and low Vs were found at several locations in the crest, railway track, and subgrade zones between 10 and 40 ft and at ∼240 ft lateral distances along the investigation lines at the crest of the railroad embankment, mostly within 15- to 30-ft depths. Low-resistivity and low-Vs zones beneath and adjacent to known sinkholes at the north slope toe indicated saturated voids and potential zones of instability. Resistivity and Vs variations indicated active seepage, hydraulically active zones, and potential sinkhole depths on both sides of the embankment. The coupled MASW and ERI investigation method revealed subsurface anomalies associated with sinkhole formation, narrowing down the critical areas for potential interventions. This noninvasive approach enabled rapid and cost-effective screening of railroad assets for prioritized proactive maintenance, particularly following extreme weather events.