Mapping of Slope Failures on Highway Embankments using Electrical Resistivity Imaging (ERI), Unmanned Aerial Vehicle (UAV), and Finite Element Method (FEM) Numerical Modeling for Forensic Analysis

Abstract

Highway Embankment Fill Slope is one of the significant components of transportation geo-infrastructures assets. Embankmets failure is a common problem that occurs due to various geotechnical, climatological, and environmental contributing parameters. Major influential factors include high temperature, high rainfall volume, and type of soil or a combination of all the above. For instance, when a slope built on high swell-shrinkage clay soil fails abruptly, it is due to the weakened self-retaining ability of the soil due to excess pore water pressure from high rainfall events. In Mississippi, rainfall is very intense, and lately, it is often characterized by aggressive showers. This rainfall generates significant soil strength losses that can endanger the safety and durability of embankments. Most embankments in the Jackson metro areas are constructed using Yazoo clay which is a typical High Swell-Shrinkage Clay Soil. These embankments have been found to experience shallow to deep failures a few years after construction due to the shrink-swell cycles during seasonal variations. These frequent failures have caused a significant maintenance problem for the Mississippi Department of Transportation (MDOT). Therefore, methods and approaches to evaluate embankment failures have been subject to careful examination by the MDOT by employing multiple investigations means, including Non-Destructive Testing (NDT) methods. To this end, in this study, Unmanned Aerial Vehicle (UAV), Electrical Resistivity Imaging (ERI), and Finite Element Method (FEM) numerical modeling were used to analyze shallow failure mechanisms within slopes. Several failed slopes located in the Jackson metro area in Mississippi were considered as references. The objective of the current study is to highlight the differences between pre and post-monitoring, evaluative, and analytic actions regarding embankments experiencing failure. During this study, four failed embankments were investigated using ERI and UAV to identify and locate the failed geometry, including slip surfaces. To better understand the failure mechanism, the identified embankments failure slip surfaces were numerically modeled using the FEM software package Plaxis 2D. Soil-strength parameters at failure were extracted through back calculation, and failure/slip surface depth was numerically characterized. The finding of this study helps post-embankments failure forensic evaluations significantly in terms of understanding failure mechanisms, identifying contributing failure parameters, better managing the decision-making process, and selecting an optimized stabilization technique.