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The ultimate bearing capacity of an eccentrically loaded strip footing above twin square tunnels buried in rock masses was examined using the generalized Hoek-Brown (GHB) yield criteria. To get reliable findings, the stability assessments were carried out using finite element limit analysis (FELA) code in combination with a sophisticated adaptive remeshing approach. Case studies with two different tunnel layouts, parallel and symmetrical, were examined. Comprehensive parametric analyses were given to demonstrate the effect of load eccentricity, rock mass strength parameters, and tunnel position on the stability of the strip footing. The visualized results of the FELA programme were presented to show how the failure mechanism would change with different influential factors. Moreover, the results were validated by comparing them to earlier investigations. [ABSTRACT FROM AUTHOR]

Random adaptive finite element limit analysis (RAFELA) is introduced to investigate the stability of the footing-voids system with random soils. The emphasis of this study is, for the footing-void system, on quantifying the influence of spatial variability on its bearing capacity and the failure probability. Of particular interest is that random field theory is utilized to characterize the spatial variability of soil, and at the same time, failure probability is calculated by imposing Monte-Carlo simulations on independent cases. Strict close bearing capacity could be obtained within the scope embraced by upper bound (UB) results and lower bound (LB) results. By imposing the proposed modelling, comprehensive parametric studies were carried out, especially for the soil spatial correlation parameters and geometry parameters. The results indicated that the failure probability would increase with the farther distance between the void and the footing, the greater coefficient of variation (COV) and the smaller vertical correlation length. Detailed design tables were presented to assess potential failure probability under different conditions. Typical failure patterns are also summarized, revealing a positive correlation between the failure probability and the diffusion degree of failure curves. [ABSTRACT FROM AUTHOR]

The undrained stability of dual circular tunnels buried in spatially random soils is investigated by imposing the random adaptive finite element limit analysis (RAFELA). The emphasis is on quantifying the effect of influential factors including the geometry parameters and spatially variability parameters on the bearing capacity and failure probability of tunnels by assuming a lognormal distribution on undrained shear strength within a spatial correlation structure. Predictions were obtained by the scope enclosed by upper bound (UB) and lower bound results (LB) results within 5% relative errors. To account for a combined effect simultaneously caused by depths of tunnels, spaces between tunnels, soil weights, and spatially variability parameters on the stability of tunnels, all independent variables are involved in parametric studies in pairs. Results revealed several failure patterns and announced how the stability evolves with changes in tunnel geometry and soil spatial variability. [ABSTRACT FROM AUTHOR]

In this study, finite element limit analysis (FELA) is employed to investigate the undrained seismic bearing capacity of strip footings placed on two-layered slopes. Upper bound theorem (UB), lower bound theorem (LB) and adaptive meshing technique were used in parametric studies to investigate the effects of various factors on seismic bearing capacity N cs and failure mechanism, especially the seismic coefficient k h and the shear strength ratio of top layer and bottom layer c u1 / c u2. The angle of the slope β , the absolute strength of top layer c u /γ B , horizontal offset distance b and the thickness of top layer D are also taken into consideration. Furthermore, the comparisons between present study and previous studies are provided. Detailed design tables are presented to distinguish the failure patterns and estimate the seismic bearing capacity of slopes under different conditions. [ABSTRACT FROM AUTHOR]

Finite element limit analysis (FELA) is used to study the undrained bearing capacity of strip footing above voids in two-layered clays. Based on the FELA results, design charts and equations are provided to calculate the undrained bearing capacity factor N s . The impact of parameters on N s also has been investigated, including undrained shear stress ratio of the soil, thickness of the top layer, location, size, width, height and spacing of the voids. The failure mechanisms for a single void maybe classified into three categories: roof failure, combined roof and wall failure, bearing failure without void failure. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the stability of dual circular tunnels in a rock mass subjected to surcharge loading using adaptive finite element limit analysis (AFELA). The tunnels are modelled under plain-strain conditions, and the rock mass is assumed to be a homogeneous and isotropic material obeying the Hoek-Brown failure criterion. For the studied problem, numerical kinematic and static approaches are employed to calculate the rigorous upper and lower bounds of the stability number N , which has been bracketed within ±5% from above and below. The calculated results are presented in the form of dimensionless stability charts, and the typical failure mechanisms are discussed through parametric studies of the problem variables using the visualized results of AFELA. [ABSTRACT FROM AUTHOR]