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The paper presents axisymmetric FEA solutions for the bearing capacity of conical footings embedded in anisotropic and inhomogeneous clays using NGI-ADP model. The bearing capacity factor of conical footings is defined to be a function of three dimensionless parameters: (i) the cone apex angle, (ii) the increasing strength gradient ratio, and (iii) the anisotropic shear strength ratio. A series of parametric studies is carried out to portray the influence of all input parameters on the bearing capacity factors. Based on the FEA results of 216 investigated cases, the artificial neural network (ANN) is adopted to capture the relationship between input parameters and output bearing capacity factors. The complex relationship between input parameters and output bearing capacity is studied through the use of design charts and failure patterns. A new accurate equation with a high value of R2 is proposed and the sensitivity of each input parameter on the output results is scored by adopting the results from the ANN model. This study has provided some practical insights into the performance of conical footings embedded in anisotropic and inhomogeneous clays. [ABSTRACT FROM AUTHOR]

Geotechnical engineers are faced with great uncertainty with regard to the stability design of soil structures such as retaining walls, foundations, and slope stability. Instead of using a deterministic approach by replacing the design parameter with a single mean number, Monte Carlo simulations could be used to provide better decisions by considering all possible outcomes under parametric uncertainty. This paper studies probabilistic failures of classical passive trapdoors in shallow depths with spatially random soils. The effects of soil strength variability are investigated for various spatial correlation lengths and trapdoor depths using the latest adaptive finite-element upper-bound limit analysis with second-order cone programming. In addition, probabilistic stability results are compared with those published in renowned literature, and a comprehensive probability of design failure (PF) charts is developed for a practical range of deterministic factors of safety. The extensive results reported in this paper would be of great interest to engineering practitioners because better decisions can be made in the design process and design confidence improved. [ABSTRACT FROM AUTHOR]

Tunneling in soft clay requires accurate estimation of the inner support pressure to prevent undesired ground settlement and maintain the overall soil stability. Previous researchers have shown that the stability factor approach, which is analogous to Terzaghi's bearing capacity factors [critical stability number (Nc), Ns, and Nγ)], is effective and efficient to determine the limit loads of many geotechnical stability problems. Therefore, this paper aims to study the stability factors of four various tunnel shapes in undrained clay: the two-dimensional (2D) tunnels of circular, square, and heading in plane strain, and the three-dimensional (3D) circular tunnel heading. Using the advanced finite-element limit analysis (FELA), rigorous upper-bound (UB) solutions of the undrained stability factors (Fc, Fs and Fγ) will be produced for various tunnel depth ratios (C/D). Numerical UB results are compared with lower bound (LB) solutions. Comprehensive design charts, tables, and equations will be presented for practitioners to estimate the critical tunnel support pressure at collapse. [ABSTRACT FROM AUTHOR]

Axisymmetric solutions for the bearing capacity of ring foundation resting on anisotropic and heterogenous clays are presented in this paper using finite element analysis (FEA). The NGI-ADP model in PLAXIS FEA, a widely used anisotropic soil model, is adopted to study the stability responses of ring foundations, with special consideration given to the effects of increasing undrained shear strength with the depth. Numerical results are formulated in terms of a dimensionless stability number (bearing capacity ratio) that is a function of three dimensionless input parameters: namely, the ratio of inner and outer radius, the increasing strength gradient ratio, and the anisotropic shear strength ratio. The influence of each dimensionless input parameter on the bearing capacity ratio is investigated using design charts and failure mechanisms, and they are scored by relative importance indexes in multivariate adaptive regression splines (MARS) model—a machine learning approach. A highly accurate equation generated from the MARS model is proposed as an effective tool for engineering practitioners. [ABSTRACT FROM AUTHOR]

Ring foundations are widely used to support various types of offshore structures because of the cost-effective reason. Unlike the traditional circular foundations, very few studies were reported with regard to the bearing capacity of ring foundations. In addition, the study on the stability effects of anisotropic and nonhomogeneous clays is yet to be found in the current literature. The purpose of the technical note is therefore to bridge the current research gap. By using the robust lower and upper bound finite-element limit analysis in axisymmetric conditions, new stability solutions of ring footings on anisotropic and nonhomogeneous clays are obtained using dimensionless parameters. The associated failure mechanisms are also examined and discussed, while the design equations are proposed for predicting the bearing capacity of ring foundations. The findings in this study provide a reliable solution to improve the current design standard for ring footings in anisotropic and nonhomogeneous clays. [ABSTRACT FROM AUTHOR]

The stability of a plane strain tall rectangular tunnel in undrained clay is investigated in this paper using shear strength reduction technique. The finite difference program FLAC is used to determine the factor of safety for unsupported tall rectangular tunnels. Numerical results are compared with upper and lower bound limit solutions, and the comparison finds a very good agreement with solutions to be within 5% difference. Design charts for tall rectangular tunnels are then presented for a wide range of practical scenarios using dimensionless ratios ~ a similar approach to Taylor's slope stability chart. A number of typical examples are presented to illustrate the potential usefulness for practicing engineers. [ABSTRACT FROM AUTHOR]