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Sponsored by ASCE Continuing Education the Geo-Institute (G-I).
INSTRUCTOR: Xiaoyu Song, Ph.D., M.ASCE
Purpose and Background
Strain localization or shear banding is a ubiquitous failure phenomenon observed in geomaterials under both saturated and unsaturated conditions. Strain localization in unsaturated soils have been studied experimentally, theoretically, and numerically in recent years because of the importance of the coupled solid deformation and partially fluids flow in practical civil engineering problems, for instance, landslides or landfill slope failures involving unsaturated soils. This webinar covers strain localization phenomena and the physical and mechanical behavior (e.g., soil water characteristic curves, shear strength, volume change) of unsaturated soils. It also covers the continuum porous media theory and the governing equations for modeling coupled hydro-mechanical processes in unsaturated soils as well as the numerical method (e.g., the mixed finite element method) widely used in the research code and commercial software in geotechnical engineering, along with typical simulation results. The instructor discusses the triggering factors of the inception of strain localization in unsaturated soils through numerical modeling (e.g., material heterogeneity, coupled hydro-mechanical processes, and loading rates). Lastly, this webinar covers the practical approach for liquefaction mitigation using the concept in unsaturated soil mechanics (e.g., nitrogen gas generation in sands for a short-term liquefaction mitigation).
Primary Discussion Topics
- Strain localization phenomenon in unsaturated soils – definition and practical importance
- Coupled solid deformation and fluid flow in unsaturated soils
- Numerical modeling of strain localization in unsaturated soils
- Triggering factors on the inception of strain localization in unsaturated soils
- Short-term liquefaction mitigation in sands by desaturation
Learning Outcomes
- Understand the strain localization phenomenon in unsaturated soils and its importance in civil engineering practice
- Discuss the mechanism of coupled hydro-mechanical processes that will occur in unsaturated soils
- Learn how to conduct numerical modeling of strain localization in unsaturated soil through the mixed finite element method
- Explain how the coupled hydro-mechanical processes will affect the volume change and shear strength of unsaturated soils
Webinar Benefits
- Determine the basic concepts of unsaturated soils such as the effective stress concept and soil water characteristic curve
- Understand strain localization phenomenon in unsaturated soils and its practical implication
- Discover the latest research on experimental study of strain localization in unsaturated soils
- Recognize the assumptions behind the numerical method for modeling hydro-mechanical processes in unsaturated soils
- Find out the factors triggering the inception of strain localization in unsaturated soils
- Understand the fundamental underlying hydro-mechanical mechanism governing unsaturated slope failures
- Discuss the latest research on short-term liquefaction mitigation by gas generation in soils
Intended Audience
- Geotechnical engineers
- Geologists
- Hydrologists
- Transportation engineers
Webinar Outline
- Strain localization phenomenon in unsaturated soils and its civil engineering applications
- Strain localization in unsaturated soils at the field scale
- Strain localization in unsaturated soils at the laboratory specimen scale
- Unsaturated soil slope failure: case study
- Landfill slope failure: case study
- Laboratory tests of strain localization in unsaturated soils
- Triaxial tests of unsaturated soils
- Plane strain tests of unsaturated soil slope failures
- Unsaturated fluids flow in unsaturated soils
- Concepts and governing equations
- Analytical and numerical solutions
- Coupled solid deformation and unsaturated flow in unsaturated soils
- Concepts and governing equations
- Numerical solutions
- Triggering factors of strain localization in unsaturated soils
- Numerical modeling
- Material heterogeneities in suction and degree of saturation
- Loading rates and boundary conditions
- Short-term liquefaction mitigation by gas generation in sands