Bearing Capacity Of Rectangular Footings Research Articles

Prediction of the Settlement and Long-Term Bearing Capacity of Rectangular Footing

Prediction of the Settlement and Long-Term Bearing Capacity of Rectangular Footing

Lower bound analysis of rectangular footings with interface adhesion factors on nonhomogeneous clays

Solutions based on lower bound limit analysis provide a safe estimate of stability, and thus they are valuable for design and analysis in practice. In this paper, new lower bound solutions of the undrained bearing capacity of rectangular footings are first presented with consideration of adhesion factors at soil–footing interfaces and linearly increasing strength with the depth of clays. The new solutions of the problem are numerically derived using three-dimensional lower bound finite element limit analysis with semidefinite programming. The new solutions are expressed in terms of dimensionless parameters, including footing aspect ratios, adhesion factors at soil–footing interfaces, and normalized strength gradient factors. A statistically algebraic equation of the undrained bearing capacity of rectangular footings is also proposed for the first time.

Scale effects on the ultimate bearing capacity of rectangular footings placed on slopes

Evaluating the bearing capacity of footing near slopes is typically performed under two-dimensional conditions. However, rectangular footings, particularly with footing aspect ratios approaching unity do not adhere to the assumption of plane-strain conditions. In this study, the scale effects of rectangular footings near slopes are investigated by using upper- and lower-bound finite element limit analysis. The results indicate that when the longitudinal directions of a footing and slope are parallel, ignoring scale effects may result in overly conservative design for bearing capacity. However, when the longitudinal directions of a footing and slope are orthogonal, rectangular footings may have more significant scale effects than square footings and it may not be conservative to simplify three-dimensional conditions to plane-strain solutions. In addition, footing shape has a significant influence on the observed failure mechanism, demonstrating a transition in failure mechanism with changing aspect ratio. Generally, the presence of a larger internal friction angle amplifies observed bearing capacity scale effects. However, contrasting behavior may occur when the longitudinal direction of footings is perpendicular to the longitudinal direction of slope face. Finally, bearing capacity scale effects become most significant when the footing is embedded with rough sidewalls near tall and steep slopes.

Numerical study of ultimate bearing capacity of rectangular footing on layered sand

Purpose: The purpose of this study is to investigate the ultimate bearing capacity of the rectangular footing resting over layered sand using finite element method. Design/methodology/approach: Finite element analysis was used to investigate the dimensionless ultimate bearing capacity of the rectangular footing resting on a limited thickness of upper dense sand layer overlying limitless thickness of lower loose sand layer. The friction angle of the upper dense sand layer was varied from 41° to 46° whereas for the lower loose sand layer it was varied from 31° to 36°. Findings: The results reveal that the dimensionless ultimate bearing capacity was found to increase up to an H/W ratio of about 1.75 beyond which the increase was marginal. The results further reveal that the dimensionless ultimate bearing capacity was the maximum for the upper dense and lower loose sand friction angles of 46° and 36°, while it was the lowest for the upper dense and lower loose sands corresponding to the friction angle of 41° and 31°. For H/W = 0.5 and 2, the dimensionless bearing capacity decreases with the increase in the L/W ratio from 0.5 to 6 beyond which the dimensionless ultimate bearing capacity remains constant for all combinations of parameters. The results were presented in nondimensional manner and compared with the previous studies available in literature. Research limitations/implications: The analysis is performed using a ABAQUS 2017 software. The limitation of this study is that only finite element analysis is performed without conducting any experiments in the laboratory. Further the study is conducted only for the vertical loading. Practical implications: This proposed numerical study can be used to predict the ultimate bearing capacity of the rectangular footing resting on layered sand. Originality/value: The present study gives idea about the ultimate bearing capacity of rectangular footing when placed on layered sand (dense sand over loose sand) as well as the effect of thickness of top dense sand layer on the ultimate bearing capacity. The findings could be used to calculate the ultimate bearing capacity of the rectangular footing on layered sand.

Numerical analysis of bearing capacity of rectangular footing

This study investigates the effects of the soil bearing pressure values of the rectangular shape footing located on the horizontal ground surface using PLAXIS software. It is Finite element method based software, used to analysis deformation and stability in engineering projects. It has a wider application in constitutive soil model (stress-strain-time relationship). PLAXIS software is a good tool which can be used for explaining the soil behaviour and settlement under different loading conditions. The two dimensional (2D) and three dimensions (3D) model of rectangular footing were analysed and compared. The results showed that the 3D analysis provides more accurate results as compared to the 2D analysis and also observed the failure mechanism of the soil model.

Theoretical Analysis of Bearing Capacity of Shallowly Embeded Rectangular Footing of Marine Structures

In this paper, the finite element analysis software ABAQUS is used to analyze the ultimate bearing capacity of three-dimensional rectangular footing of marine structures. The deformation law and the failure mode of homogeneous seabed soil beneath the rectangular footing are analyzed in detail. According to the equivalent plastic strain of soil under rectangular footing, an allowable velocity field of homogeneous seabed soil is reasonably constructed. Based on the plastic limit analysis theory of soil mass and by using the Mohr-Coulomb yield criterion, an upper bound solution of the ultimate bearing capacity of three- dimensional rectangular footing on general homogeneous seabed soil is derived, and a correction factor of ultimate bearing capacity of three-dimensional rectangular footing is given. To verify the rationality and applicability of this theoretical solution, some numerical solutions are achieved using the general-purpose FEM analysis package ABAQUS, and comparisons are made among the derived upper bound solution, the solution of Vesic, and the solution of Salgado et al. The results indicate that the upper bound solution of the three-dimensional shallowly embedded rectangular footing proposed in this paper is accurate in calculating the bearing capacity of homogeneous seabed soil. For undrained saturated clay foundation and sandy foundation with smaller internal friction angle, this upper bound solution can evaluate the ultimate bearing capacity of rectangular footing; with the gradual increase of the internal friction angle of the soil, the ultimate bearing capacity of the proposed upper bound solution is slightly higher than that of the rectangular footing.

Bearing capacity of rectangular footings in uniform clay with deep embedment

This letter is concerned with the undrained bearing capacity of rectangular footings with various aspect ratios and embedment ratios in uniform clay. It covers thin plate foundations with low aspect ratios and high embedment depth with embedment ratio up to 150. The work is based on small strain finite element analysis (FEA). After verification of the FEA model against existing solutions of the bearing capacity factors of rectangular footings, a series of FEA results are obtained. Based on the FEA results, a simple formulation is proposed to calculate the bearing capacity factor for rectangle footing with different aspect ratio in any embedment depth, extending the existing solutions to cover a wider ranges of footing aspect ratios and embedment ratios.

BIFURACATION PHENOMENA UNDERLYING THE BEARING CAPACITY OF RECTANGULAR FOOTINGS ON DENSE SAND

基礎の支持力問題や斜面の安定問題といった地盤工学の応用分野では, その簡便性や信頼性から, 極限解析に基づく算定式が古くから用いられてきた. しかし近年, より合理的な評価のためには, 進行性破壊や分岐の考慮が必要であるとの認識が広まりつつある. 本論文は, 遠心載荷実験を行うことにより基礎の支持力特性を求め, そのメカニズムを分岐理論により明らかにするものである. 基礎の支持力特性の3次元効果について考察すると共に, 漸近的分岐理論の手法を用いて, 荷重-変位曲線をもとに分岐現象の介在を検証し, 基礎形状などによる強度や破壊モードの変動が分岐現象として説明可能であることを示す.

Bearing Capacity of Rectangular Footings on Geogrid‐Reinforced Sand

A study was undertaken to investigate the bearing capacity of rectangular footings on geogrid‐reinforced sand by performing laboratory model tests as well as finite‐element analyses. The effects of the depth to the first layer of reinforcement, vertical spacing of reinforcement layers, number of reinforcement layers, and the size of reinforcement sheet on the bearing capacity were investigated. Both the experimental and analytical studies indicated that there was an optimum reinfprcement embedment depth at which the bearing capacity was the highest when single‐layer reinforcement was used. Also, there appeared to be an optimum reinforcement spacing for multi‐layer reinforced sand. The bearing capacity of reinforced sand was also found to increase with reinforcement layer number and reinforcement size when the reinforcement was placed within a certain effective zone. In addition, the analysis indicated that increasing reinforcement stiffness beyond a certain value would not bring about further increase in the bearing capacity.