دانلود رایگان مقاله انگلیسی ظرفیت باربری لرزه ای فونداسیون سطحی در زمین شیبدار منسجم - الزویر 2018

ABSTRACT

Engineers often assume undrained conditions in stability calculations of shallow foundations resting on soil with fine content as this assumption yields conservative results. Calculation of undrained bearing capacity of shallow foundations on level ground is a well-defined problem and when the footing is located on or near slopes, empirical equations or design charts produced based on limit equilibrium, upper bound plasticity calculations or finite element method (FEM) analyses are used. On the other hand, available studies that consider seismic bearing capacity of foundations on cohesive soils do not consider the influences of all influential parameters. Therefore, their use in design practice is rather limited. Accordingly, this study attempts to develop design charts that consider the influences of all parameters that affect the undrained bearing capacity factor of surficial strip footings under seismic conditions (Ncse). These influences are footing width, slope angle, slope height, footing position, undrained shear strength and pseudo-static acceleration coefficient. As the number of parameters to be considered is high, a parametric study is conducted using FEM models. Obtained results are consistent with the results of available studies in literature. Proposed design charts allow the selection of problem specific Ncse values. A design procedure is defined and two design examples are presented for the calculation of the magnitude of undrained bearing capacity under seismic conditions.

8. Conclusions

Bearing capacity check is required for satisfying the stability criteria when designing shallow foundations. Even though calculation of static bearing capacity is a straightforward task for horizontal ground conditions, there is no well-defined way for considering the influences of seismicity and ground inclination. Accordingly, this parametric study proposes design charts for selecting suitable seismic bearing capacity factors for strip foundations located on or near cohesive slopes. Presented design charts are developed based on the results of numerous FEM models corresponding to different geometries, pseudo-static accelerations and undrained soil properties. Owing to the large number of influential parameters, it is not possible to quantify the results using mathematical functions. Therefore a methodology based on the selection of appropriate seismic bearing capacity factors from the proposed charts using interpolation and extrapolation is devised. Inherent and explicit assumptions used in the analysis stage and during the development of charts are all geared towards obtaining conservative estimates of the factors for calculating the ultimate seismic bearing capacity value. Obtained results were compared with similar but more limited studies available in literature for verification purposes and the results are shown.