Sensitivity of the stability assessment of a deep excavation to the material characterisations and analysis methods
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ORIGINAL ARTICLE
Sensitivity of the stability assessment of a deep excavation to the material characterisations and analysis methods Mohsen Ghadrdan . Tahereh Shaghaghi . Ali Tolooiyan
Received: 2 July 2020 / Accepted: 22 September 2020 Springer Nature Switzerland AG 2020
Abstract Due to the spatial variability of material characterisations in deep and large scale excavations, stability assessment is often a challenging task. Numerous slope stability analysis methods based on a range of assumptions and principles are implemented in commercial software packages to ease the process of stability assessment of non-homogeneous and multi-layered slopes. However, the selection of a suitable method remains crucial as the application of an unrealistic or unsuitable method may lead to catastrophic consequences. Besides material shear strength parameters, and analysis methods, nonstrength characterisations such as permeability and creep can affect the result of slope stability analysis significantly. In this study, the sensitivity of the stability assessment of a deep excavation in Australia to material characterisations such as friction angle, cohesion and permeability and creep is investigated by the use of different formulations and assumptions of the Limit Equilibrium Method (LEM) and the Finite Element Method (FEM) as the two most common
M. Ghadrdan T. Shaghaghi Geotechnical and Hydrogeological Engineering Research Group (GHERG), Federation University Australia, Churchill, VIC, Australia A. Tolooiyan (&) School of Engineering, College of Sciences and Engineering, University of Tasmania, Hobart, TAS, Australia e-mail: [email protected]
slope stability methods. The results show that the stability assessment is highly sensitive to the applied method and assumptions. Moreover, the role of material strength and non-strength parameters and the selection of a suitable constitutive model in slope stability assessment is presented. Keywords Slope stability Sensitivity analysis Factor of safety LEM FEM List of Abbreviations LEM Limit Equilibrium Method FEM Finite Element Method FOSM First Order Second Moment LE Limit Equilibrium FoS Factor of Safety SSR Shear Strength Reduction SRF Strength Reduction Factor FE Finite Element bgl Below ground level SI Scenario 1 SII Scenario 2 SIII Scenario 3 SIV Scenario 4 LEMC Linear Elastic model combined with perfectly plastic Mohr–Coulomb failure criterion HS Hardening Soil SSC Soft Soil Creep NEPWP Negative Excess Pore-Water Pressure
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Geomech. Geophys. Geo-energ. Geo-resour. (2020)6:59
List of symbols E Interslice normal force X Interslice shear force s Shear strength c’ Effective cohesion /’ Effective friction angle c* Reduced cohesion /* Reduced internal friction angle E0 Elastic modulus m0 Poisson’s ratio Eref Reference stiffness modulus related to the 50 reference stress (here 100 kPa) Eref Tangent stiffness for primary oedometer oed loading ref Eur Unloading/reloading stiffness K0 Earth pressure coefficient at rest k* Modified compression
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