Abstract
Evidence supporting the implementation of three-dimensional (3D) slope stability analysis in geotechnical engineering practice has been mounting since the nineteen-seventies. Current levels of computational power and its accessibility has allowed researchers to investigate the significance of the 3D numerical analysis output compared to conventional 2D limit equilibrium approach. This study compares results of stability analyses of unsupported vertical cuts in the vadose zone using both 2D (GeoStudio 2019 R2) and 3D (FLAC3D) software. Numerical analyses are carried out for various dimensions of unsupported vertical cuts excavated in an unsaturated glacial till. The findings from two different methods (i.e. 2D and 3D) and the limitations of 2D stability analysis are discussed.
Highlights
Most engineering projects involving foundations, landfills, pipelines, storm drains, etc. are initiated with an excavation or a trench prior to the installation of infrastructure
Many construction projects involve excavation or trenching and installing infrastructure in the vadose zone; the critical height of an unsupported cut should be determined by extending the mechanics of unsaturated soils
Critical heights were estimated using SLOPE/W and FLAC3D (3D) and the results were compared for a case where the ground water table (GWT) is 1 m below the ground surface
Summary
Most engineering projects involving foundations, landfills, pipelines, storm drains, etc. are initiated with an excavation or a trench prior to the installation of infrastructure. Many construction projects involve excavation or trenching and installing infrastructure in the vadose zone; the critical height of an unsupported cut should be determined by extending the mechanics of unsaturated soils. The critical height of an unsupported cut in the vadose zone can be estimated by conducting a slope stability analysis while considering the influence of matric suction. In this case, two different approaches can be used; namely, 2D and 3D methods. Field workers intuitively know that the narrower the width of the crosssection, the higher the factor of safety This can give an impression that the stability of the cross-section of an unsupported vertical cut is not of concern even if the width of a cross-section is wide enough not to be affected by 3D effects. An attempt is made to compare the critical heights of unsupported vertical cuts in an unsaturated glacial till (i.e. Indian Head till) for various dimensions of cross-sections using SLOPE/W (GeoStudio 2019, 2D method) and FLAC3D (3D method)
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