Geotechnical stability analysis
TL;DR: In this paper, the authors describe recent advances in stability analysis that combine the limit theorems of classical plasticity with finite elements to give rigorous upper and lower bounds on the failure load.
Abstract: This paper describes recent advances in stability analysis that combine the limit theorems of classical plasticity with finite elements to give rigorous upper and lower bounds on the failure load. These methods, known as finite-element limit analysis, do not require assumptions to be made about the mode of failure, and use only simple strength parameters that are familiar to geotechnical engineers. The bounding properties of the solutions are invaluable in practice, and enable accurate limit loads to be obtained through the use of an exact error estimate and automatic adaptive meshing procedures. The methods are very general, and can deal with heterogeneous soil profiles, anisotropic strength characteristics, fissured soils, discontinuities, complicated boundary conditions, and complex loading in both two and three dimensions. A new development, which incorporates pore water pressures in finite-element limit analysis, is also described. Following a brief outline of the new techniques, stability solutions ...
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TL;DR: In this article, a modification of the so-called Davis approach is proposed to estimate the factor of safety of slopes, even for extreme cases of steep slopes with friction angles in excess of 40° and zero dilatancy.
115 citations
TL;DR: In this article, a field case of operated metro shield tunnel disrupted by unexpected extreme surcharge in Shanghai is reported, where deformational responses of segmental lining, in terms of convergences, settlements and joint open width, are highlighted.
Abstract: A field case of operated shield tunnel disrupted by unexpected extreme surcharge in Shanghai is reported in this paper. The deformational responses of segmental lining, in terms of convergences, settlements and joint open width, are highlighted. The surcharge caused by unexpected dumped soils with a maximum height of 7 m is six times larger than the design value of surcharge. Three hundred and sixty segmental lining rings of the operated metro shield tunnel below this surcharge are severely affected. The measured horizontal convergence to outer-diameter ratio (ΔD/Dout) ranges from 16.6 to 35.7‰, which is far beyond the averaged value for normal condition, i.e. 5.1‰. The trend of tunnel deformation (e.g. horizontal convergence and settlement) varying with surcharge level is found to be significantly non-linear. Correspondingly, the longitudinal joints are also severely disrupted and have large open widths. The rubber packer for joint near-tunnel springline loses its function of waterproof due to th...
90 citations
TL;DR: In this article, an approximate closed-form solution was proposed for three-dimensional undrained tunnel face stability in clays with constant or linearly increasing shear strength profiles with depth.
85 citations
TL;DR: In this paper, the authors compare the strength reduction method with rigorous limit analyses which are based on collapse theorems of plasticity, and investigate if a shortcoming of strength reduction methods, namely possible numerical instabilities for non-associ...
Abstract: In practical geotechnical engineering the factor of safety is still determined by means of simple limit equilibrium analysis in many cases. However, because displacement finite-element analysis is routinely applied for assessing displacements and stresses for working load conditions, this technique is increasingly being used to calculate ultimate limit states and, consequently, factors of safety, usually by means of the so-called strength reduction technique, and results which are comparable to those obtained with limit equilibrium methods have been reported in the literature. However, owing to the inherent assumptions of limit equilibrium analyses, they do not always provide unique factors of safety. The purpose of this paper is on the one hand to compare the strength reduction method with rigorous limit analyses which are based on collapse theorems of plasticity, and on the other hand to investigate if a shortcoming of the strength reduction method, namely possible numerical instabilities for non-associ...
82 citations
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TL;DR: A method is described for the minimization of a function of n variables, which depends on the comparison of function values at the (n 41) vertices of a general simplex, followed by the replacement of the vertex with the highest value by another point.
Abstract: A method is described for the minimization of a function of n variables, which depends on the comparison of function values at the (n 41) vertices of a general simplex, followed by the replacement of the vertex with the highest value by another point. The simplex adapts itself to the local landscape, and contracts on to the final minimum. The method is shown to be effective and computationally compact. A procedure is given for the estimation of the Hessian matrix in the neighbourhood of the minimum, needed in statistical estimation problems.
27,271 citations
"Geotechnical stability analysis" refers methods in this paper
...The resulting unconstrained optimisation problem requires the ratio of the internal and external energy dissipation rates to be minimised, and was solved using the simplex method of Nelder & Mead (1965)....
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4,474 citations
"Geotechnical stability analysis" refers methods in this paper
...Following this work, Arai & Tagyo (1985) used constant-stress elements, and the sequential unconstrained minimisation technique with the conjugate gradient algorithm of Fletcher & Reeves (1964), to obtain a statically admissible stress field for geotechnical problems....
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4,215 citations
"Geotechnical stability analysis" refers methods in this paper
...…yield constraints directly, converted the constrained optimisation problem to an unconstrained one using the extended penalty method of Kavlie & Moe (1971), and computed the optimal solution (best lower bound) using a variant of the sequential unconstrained minimisation technique (Powell, 1964)....
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2,139 citations
"Geotechnical stability analysis" refers methods in this paper
...Indeed, early examples of widely used slope stability methods include those of Janbu (1954, 1973), Bishop (1955), Morgenstern & Price (1965), Spencer (1967) and Sarma (1973, 1979)....
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Book•
01 Jan 1984
TL;DR: In this paper, a front-tracking method is used to solve moving boundary problems and an analytical solution of seepage problems is proposed. But this method is not suitable for solving free boundary problems.
Abstract: 1. Moving boundary problems: formulation 2. Free boundary problems: formulation 3. Analytical solutions 4. Front-tracking methods 5. Front-fixing methods 6. Fixed-domain methods 7. Analytical solution of seepage problems 8. Numerical solution of free boundary problems References Author index Subject index
1,880 citations