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INSTRUCTORS:
Abhishek Kumar Tiwari
Alomir Favero
Sina Javankhoshdel, P.Eng., Ph.D.
Siamak Yoosefi, S.M.ASCE
Mohamed Hassan, E.I., S.M.ASCE
Purpose and Background
These presentations were recorded at the Geo-Extreme 2025 conference.
Seepage Dynamics of Geosynthetic-Reinforced Dikes Under Normal and Extreme Wave Condition in Coastal Louisiana (10 minutes)
This presentation examines the seepage behavior and stability of geosynthetic-reinforced earthen dikes subjected to both normal water levels and extreme wave and drawdown conditions typical of coastal Louisiana. The study highlights limitations of traditional steady-state seepage analyses and emphasizes the importance of transient hydraulic conditions during hurricanes and storm surges. Numerical modeling was conducted to evaluate pore water pressure evolution and slope stability under rapid filling and drawdown scenarios. Results show that transient drawdown conditions can significantly reduce factors of safety compared to steady-state assumptions. The effectiveness of geogrid reinforcement in improving dike stability under critical conditions is also evaluated. The findings provide practical guidance for resilient coastal dike design in soft soil environments.
Large Deformation and Critical State Analysis of the Fundao Tailings Dam (11 minutes)
This presentation focuses on the large-deformation behavior and post-failure mechanisms of the Fundão tailings dam failure using a critical state soil mechanics framework. A meshless numerical method, Smoothed Particle Hydrodynamics (SPH), was employed to model both failure initiation and run-out processes. The analysis incorporates a critical state constitutive model calibrated using laboratory data from tailings materials. Results demonstrate the model’s ability to capture liquefaction, large displacements, shear band formation, and observed field behaviors during failure. The study also provides estimates of flow velocity and run-out characteristics relevant to downstream risk assessment. This work advances understanding of tailings dam failure consequences beyond traditional triggering analyses.
Probabilistic Analysis of a Landslide under an Extreme Rainfall Considering Spatial Variability of Soil Strength and Hydraulic Parameters (15 minutes)
This presentation presents a probabilistic framework for analyzing landslide stability under extreme rainfall by incorporating spatial variability of both soil strength and hydraulic parameters. Unlike conventional deterministic approaches, the method quantifies probability of failure using stochastic random fields and advanced limit equilibrium techniques. The study demonstrates how rainfall-induced infiltration and suction loss affect slope stability over time. Results highlight that spatial variability in soil strength plays a dominant role in instability, while hydraulic variability influences failure probability when coupled with strength variability. Comparisons between deterministic, single random variable, and fully stochastic analyses show significant differences in predicted risk. The findings underscore the importance of probabilistic methods for realistic landslide risk assessment.
Determination of Void Ratio Distribution within a Coastal Soil Sample using Laboratory Test Methods and Image Analysis of X-Ray CT Scans (10 minutes)
This presentation investigates the internal void ratio distribution of coastal soils using X-ray computed tomography (CT) imaging combined with conventional laboratory measurements. Traditional void ratio calculations provide average values but fail to capture spatial variability within intact samples. CT imaging allows non-destructive visualization and quantification of air, water, and mineral phases within soil cores. Various image segmentation and thresholding techniques were evaluated to assess their influence on void ratio estimation. Results demonstrate that scan duration and image processing methods significantly affect measurements. The study highlights the value of CT imaging for improving understanding of coastal soil structure and heterogeneity.
Application of Direct Shear Testing to Assess the Influence of Mangrove Root Structures on the Shear Strength of Coastal Wetlands (14 minutes)
This presentation evaluates the influence of mangrove root systems on the shear strength of coastal wetland soils using modified direct shear testing methods. Field samples were collected from multiple coastal basins with varying geomorphic and sedimentary conditions. Laboratory modifications enabled direct shear testing of intact soil–root cores while preserving natural structure. Results show that near-surface shear strength is strongly influenced by live root biomass, exhibiting strain-hardening behavior. Differences between river-dominated and tide-dominated environments highlight the combined effects of roots and sediment type. The findings provide mechanistic insight into how vegetation contributes to coastal wetland stability.
Benefits and Learning Outcomes
Upon completion of these sessions, you will be able to:
- Explain how transient seepage conditions influence the stability of geosynthetic-reinforced coastal dikes.
- Describe how large-deformation numerical modeling can be used to evaluate tailings dam failure and run-out behavior.
- Discuss the role of spatial variability in soil and hydraulic properties in probabilistic landslide analysis.
- Identify how X-ray CT imaging enhances characterization of void ratio distribution in coastal soils.
- Explain how mangrove root structures affect the shear strength of coastal wetland soils.
Assessment of Learning Outcomes
Students' achievement of the learning outcomes will be assessed via a short post-test assessment (true-false, multiple choice, and/or fill in the blank questions).
Who Should Attend?
- Geotechnical Engineers
- Structural Engineers
- Civil Infrastructure Designers
- Researchers and Academics
- Risk and Resilience Analysts
- Construction and Project Managers
How to Earn your CEUs/PDHs and Receive Your Certificate of Completion
To receive your certificate of completion, you will need to complete a short post-test online and receive a passing score of 70% or higher within 1 year of purchasing the course.
How do I convert CEUs to PDHs?
1.0 CEU = 10 PDHs [Example: 0.1 CEU = 1 PDH]