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AbstractSimilar to pile group, the process of designing an anchor group requires the determination of an efficiency factor that describes the overlapping effects of neighboring anchors. This research article introduces an efficiency factor denoted as ξ, which represents the ratio of the ultimate uplift pressure of a single anchor within a group to the ultimate uplift pressure of an isolated anchor. The primary approach employed involves advanced 3D finite element limit analysis with an adaptive meshing technique, which can be utilized to examine the uplift stability problem of 3D anchor groups. Numerical findings are compared with those obtained from previous research, incorporating both experimental and analytical results. This would ensure that our results are validated and provide valuable information into the performance of anchor groups. In addition to these findings, we introduce a MARS machine learning model, which has been trained using a dataset of 875 data points. This model is designed to establish an empirical equation that can be practically used for design purposes. To further enhance our understanding, we present the relative importance index (RII). This index allows us to identify which factors have the most significant impact on the behavior of anchor groups. In conclusion, the results presented in this article are of practical significance for the geotechnical engineering community. [ABSTRACT FROM AUTHOR]

Pit-in-pit (PIP) excavations in an aquifer-aquitard system likely undergo catastrophic failures under the hydraulic uplift, the associated undrained stability problem, however, has not been well analyzed in the past. To this end, a hypothetical model of PIP braced excavation in typical soil layers of Shanghai, China is developed using the finite element limit analysis (FELA) tool. The FELA solutions of safety factors (FSs) against hydraulic uplift are verified with the results from the finite element analysis with strength reduction technique (SRFEA) and existing design approaches. Subsequently, FELA is employed to identify the triggering and failure mechanisms of PIP braced excavations subjected to hydraulic uplift. A series of parametric studies considering the various geometric configurations of the PIP excavation, undrained shear strengths of aquitard, and artesian pressures are carried out. The sensitivities of relevant design parameters are further assessed using a multivariate adaptive regression splines (MARS) model that is capable of accurately capturing the nonlinear relationships between a set of input variables and output variables in multi-dimensions. A MARS-based design equation used for predicting FS is finally presented using the artificial dataset from FELA for practical design uses. [ABSTRACT FROM AUTHOR]

The ultimate lateral resistance of free- and fixed-headed piles in cohesive soil is examined in this paper using the three-dimensional finite element limit analysis with upper and lower bound theorems. A special concern, and that is the novelty of this study, is devoted to the combined effect of the three important dimensionless parameters; namely, the overburden stress factor (n), the pile length-diameter ratio (L/D), and the ratio of eccentric length to diameter (e/D). Numerical results are expressed by using Broms's horizontal load factor, and comparisons are made with several published solutions. In addition, the associated failure mechanisms are investigated with respect to the three parametric effects. The adopted new technique has been successfully used to study a number of different geo-stability problems. It is thus the aim of this paper to produce accurate and practical results with design equations and charts that can be used by practitioners to predict the undrained lateral capacity of fixed- and free-headed piles. [ABSTRACT FROM AUTHOR]

The stability of unsupported rectangular excavations in undrained clay is examined under the influence of anisotropy and heterogeneity using the three-dimensional finite element upper and lower bound limit analysis with the Anisotropic Undrained Shear (AUS) failure criterion. Three anisotropic undrained shear strengths are considered in the study, namely triaxial compression, triaxial extension, and direct simple shear. Special considerations are given to the study of the linearly-increased anisotropic shear strengths with depth. The numerical solutions are presented by an undrained stability number that is a function of four dimensionless parameters, i.e., the excavated depth ratio, the aspect ratio of the excavated site, the shear strength gradient ratio, and the anisotropic strength ratio. To the authors' best knowledge, this is the first of its kind to present the stability solutions of 3D excavation considering soil anisotropy and heterogeneity. As such, this paper introduces a novel approach for predicting the stability of unsupported rectangular excavation in undrained clays in 3D space, accounting for soil anisotropy and non-homogeneity. Notably, it develops a basis to formulate a mathematical equation and design charts for estimating the stability factor of such type of excavation, which should be of great interest to engineering practitioners. [ABSTRACT FROM AUTHOR]

This paper presents rigorous plasticity solutions to the classical active and passive earth pressure problems. The primary method adopted is a conventional equation based on the soil property and three stability factors (F c , F s, and F γ), that are analogous to Terzaghi's bearing capacity factors (N c , N s , and N γ) of strip footings. The proposed method is considered as a practical yet smart approach to the determination of earth pressures and is one of the main novelties in this study. To achieve this, the finite element limit analysis (FELA) of upper and lower bounds solutions, a powerful tool in studying the behaviour of soil stability, is employed to compute the three stability factors for a wide range of soil internal friction angles, wall roughness, and surcharge pressures. In addition, analytical solutions based on statistically admissible stress fields are adopted to validate the proposed FELA solutions. The validation satisfactorily demonstrated the accuracy and reliability of the proposed solutions. It follows that the numerical results are presented in the form of tables, figures, and several examples provided to demonstrate the practical use of the three factors in estimating active and passive earth pressures with various backfill soils, wall roughness, and surcharge pressure. The study should, therefore, be of value to practitioners. [ABSTRACT FROM AUTHOR]