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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]

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]

An asymmetric failure mode of soil in front of laterally loaded piles at the slope crest is presented to estimate the pile bearing capacity in this study. The effect of soil shear strength below the rotation center is taken into account by postulating the suppositional sliding curve and corresponding mobilization coefficient of soil strength. Subsequently, the soil resistances above the rotation center at soil failure can be obtained by upper bound theorem of limit analysis. Employing static equilibrium equations, the analytical solution of lateral bearing capacity of piles is assessed by adopting the concept of effective embedment depth. The analytical solution, considering the the slope effect on limiting force profile, is then validated by numerical predictions and full-scale tests. Furthermore, a non-dimensional coefficient, capacity ratio, is proposed to characterize the slope effect on the bearing capacity of laterally loaded piles, and the range of capacity ratio for different internal friction angles are differentiated as different distribution areas. The effect of distance between the pile and slope crest on pile bearing capacity is further investigated, and the capacity ratios appear to be approximatively linear with normalized distance λ and would increase to 1 until λ exceeds the critical value. [ABSTRACT FROM AUTHOR]