Ultimate Bearing Capacity Of Strip Research Articles

Numerical Analysis of the Ultimate Bearing Capacity of Strip Footing Constructed on Sand-over-Clay Sediment

This paper analyzes the bearing capacity of two-layered soil medium using finite element (FE) software ABAQUS/CAE 2023. Although geotechnical engineers design foundations for layered soil, majorly current geotechnical studies emphasize single homogenous soil. So, this research has significant novelty as it focuses on layered soil and adds to the current literature. A nonlinear FE model was prepared and analyzed to determine the ultimate bearing capacity of two-layered soil (sandy soil over clayey soil). The Drucker–Prager and Mohr–Coulomb models were used to represent sandy soil and clayey soil layers, respectively. Strip footing material properties were considered isotropic and linearly elastic. This study performed parametric studies to understand the effects of thickness, unit weight, and the modulus of the elasticity of sandy soil on the ultimate soil bearing capacity. Additionally, it also analyzed the effect of the cohesive strength of clayey soil on layered soil bearing capacity. Results showed that an increase in sandy soil layer thickness strengthens the layered soil, and thus, improves the bearing capacity of soil. Increasing the sandy soil layer thickness over footing width (h1/B) ratio from 0.15 to 2.0 improved the ultimate bearing capacities with elastic settlements of 350 mm and 250 mm by 145.62% and 101.66%, respectively. Additionally, for a thicker sandy soil layer, an increase in the unit weight and modulus of the elasticity of sandy soil led to higher ultimate bearing capacity. Furthermore, it was concluded that an increase in clayey soil’s cohesive strength from 20 kPa to 30 kPa resulted in a 24.31% and 3.47% increase in soil bearing capacity for h1/B = 0.15 and h1/B = 2.0, respectively. So, the effect of cohesion is prevalent in the case of a thicker clayey soil layer.

New Failure Mechanism for Evaluating the Static and Seismic Ultimate Bearing Capacity of Strip Footings Adjacent to Slope

The seismic slip line field theory (SLFT) is derived based on the method of characteristic, and the critical slope contour calculated by the SLFT is a convex shape when a high surcharge is imposed on the slope top surface. A simple and robustness failure mechanism is proposed to calculate the static and seismic ultimate bearing capacity of strip footing adjacent to the cohesion-frictional slopes where the critical slope contour shifts from the inside of the slope to the outside of the slope with the increase of the boundary load, and the slope is at the limit state when the critical slope contour is tangent to the slope surface. The influence of slope and footing geometric features, soil parameters, and the seismic load on the bearing capacity is analyzed. The ultimate bearing capacity decreases as the strength parameters decreases, and the slope angle and the seismic coefficient increases. The static and seismic bearing capacity calculated by the proposed method does not require the failure models to be initially assumed, and the results are consistent with those of the other methods.

Ultimate bearing capacity of strip footing resting on rock mass using adaptive finite element method

An essential requirement during the design of structures is a rational assessment of the ultimate bearing capacity of the footing resting on rock mass (qu). The qu is influenced by several parameters, and the simultaneous consideration of all such factors during the assessment of ultimate bearing capacity is a cumbersome process. Considering that the available literature lacks in providing the influence of various parameters of the rock mass on qu, an attempt has been made in this study to evaluate qu of a strip footing resting on a rock mass, which was presumed to follow the latest form of Hoek-Brown failure criterion using finite element modeling. The results obtained in this study were validated with the previous findings of the bearing capacity factors (Nσ0) for a footing resting on weightless rock mass. A comprehensive study has been performed to get an insight into the factors affecting the qu of a footing resting over the rock mass by varying the Geological Strength Index (GSI) ranging from 10 to 100, as well as the disturbance factor (D) at 0 and 1, together with the embedment depth of the footing (Df). The qu is determined by the load-settlement response obtained from numerical simulations and the observed potential failure planes from the simulations are analyzed and discussed. The results showed that the qu was greatly influenced by the GSI of the rock mass and the effect of D reduces with higher values of GSI. The study recommends that the qu of a poor mass can be increased by placing the footing at a deeper depth (Df).

The implementation of improved radial movement optimization to calculate the ultimate bearing capacity of strip footing on unsaturated soil under inclined loading

The implementation of improved radial movement optimization to calculate the ultimate bearing capacity of strip footing on unsaturated soil under inclined loading

Ultimate bearing capacity of strip footing resting on clay soil mixed with tire-derived aggregates

Ultimate bearing capacity of strip footing resting on clay soil mixed with tire-derived aggregates

Ultimate bearing capacity of strip and circular foundations using power type yield criterion using the method of stress characteristics

For determining the bearing capacity of foundations, the existing investigations have been mainly performed by using a linear yield criterion in shear stress (τ)-normal stress (σn) domain, for instance, the Mohr-Coulomb (MC) and Tresca yield criteria. However, the yield criteria for most granular soils are generally nonlinear with continuously increasing friction angle at decreasing stress level. In the present research, the method of stress characteristics has been employed to compute the ultimate bearing capacity of circular and strip foundations considering a power type (PT) nonlinear yield criterion which depends on three material parameters rather than two in the MC yield criterion. Rigorous solutions have been generated for both rough and smooth footing bases and the results have been expressed in terms of the variation of the bearing capacity factor Nσ with the changes in different material parameters and the overburden pressure. The slip line patterns and the variation of the vertical normal pressure below the footing base have also been examined. Further, the effectiveness of the PT nonlinear yield criterion in determining the bearing capacity of foundations has been discussed. The solutions obtained have been found to compare well with different computational and experimental results reported in literature.

Study on the ultimate bearing capacity of a strip footing influenced by an irregular underlying cavity in karst areas

This study investigates the ultimate bearing capacity and typical failure mechanisms of a rough strip footing constructed above an irregular cavity using the upper bound finite element limit analysis (UBFELA) method. A novel method based on the inverse discrete Fourier transform (IDFT) theory is employed to generate and quantitatively describe the irregular shape of natural cavities. Parametric studies are performed to study the influence of several variables, including the ratio of the cavity size to the strip footing width (D/B), the ratio of the cover depth to the footing width (H/B), the internal friction angle (φ), the direction angle of the long axis of the cavity (θ) and the shape descriptors of the cavity (D2, D3, and D8). Numerical results are presented in the form of dimensionless charts for the bearing capacity numbers (Pu/c). The obtained failure modes present significant asymmetry and a critical region is found to be greatly affected by the size of the cavity (D/B), the cavity depth (H/B) and the internal friction angle (φ).

Ultimate bearing capacity of strip footing resting on soil bed strengthened by wraparound geosynthetic reinforcement technique

In the recent past, the wraparound geosynthetic reinforcement technique has been recommended for constructing the geosynthetic-reinforced soil foundations. This paper presents the development of an analytical expression for estimating the ultimate bearing capacity of strip footing resting on soil bed reinforced with geosynthetic reinforcement having the wraparound ends. The wraparound ends of the geosynthetic reinforcement are considered to provide the shearing resistance at the soil-geosynthetic interface as well as the passive resistance due to confinement of soil by the geosynthetic reinforcement. The values of ultimate load-bearing capacity determined by using the developed analytical expression agree well with the model footing load test values as reported in the literature.

The feasibility of PSO–ANFIS in estimating bearing capacity of strip foundations rested on cohesionless slope

This study aimed to assess particle swarm optimization (PSO) optimized with an adaptive network-based fuzzy inference system (ANFIS) for the prediction of the ultimate bearing capacity of strip footing resting on a sloping crest. To make datasets, a 2524 finite element model (FEM) simulation analysis was performed. In this sense, the k-fold validation technique selected for the selection of the testing and validation purposes. Also, the variables of the ANFIS algorithm (i.e., the number of clusters), and the PSO algorithm (the population size were optimized using a series of trial and error process. The second main objective of the current study was to assess the applicability of PSO–ANFIS in estimating the ultimate bearing capacity of the strip footing resting on a single cohesionless slope when it was subjected to an external vertical applied stress. The input parameters were the soil properties (Stype) (classified into five different classes from the weakest, shown as S1, to the strongest type, displayed in higher order), slope angle (β), setback distance ratio (b/B) (the distance of the footing from the slope crest to the footing width), and vertical settlement (Uy) of the footing, while the main output was the applied vertical stresses (Fy) that can be applied on the footing. Note that the ultimate bearing capacity (Fult) is the maximum vertical stress when Uy = 0.1 B. A thorough comparison between the measured FEM simulations, the proposed ANFIS and PSO–ANFIS models were carried out to demonstrate their effectiveness in predicting a reliable Fult resting on cohesionless slopes.

Ultimate bearing capacity of strip footing on sands under inclined loading based on improved radial movement optimization

Improved radial movement optimization (IRMO) is adopted to investigate the critical slip surface and ultimate bearing capacity of a rough embedded strip footing on sands under inclined loading using the upper-bound limit analysis. Based on the Mohr–Coulomb yield criterion, a planar kinematically admissible multi-block failure mechanism of strip footing under inclined loading is formulated. The soil is assumed to be elastic–perfectly plastic material with an associated flow rule, and a solution procedure for the ultimate bearing capacity is established based on the virtual work principle. The results show that IRMO can calculate the ultimate bearing capacities efficiently, accurately and stably. The size and shape of normalized failure envelopes and inclination factors depend on the friction angle and embedment ratio. Moreover, the errors of the joint and individual influences of soil unit weight and surcharge for the bearing capacity of strip footing decrease with increasing load inclination angle α.

Effective Width Rule in the Analysis of Footing on Reinforced Sand Slope

Abstract This paper presents the results obtained from an experimental programme and numerical investigations conducted on model tests of strip footing resting on reinforced and unreinforced sand slopes. The study focused on the determination of ultimate bearing capacity of strip footing subjected to eccentric load located either towards or opposite to the slope facing. Strip footing models were tested under different eccentricities of vertical load. The obtained results from tests conducted on unreinforced sand slope showed that the increase in eccentricity of applied load towards the slope facing decreases the ultimate bearing capacity of footing. Predictions of the ultimate bearing capacity obtained by the effective width rule are in good agreement with those proposed from the consideration of total width of footing subjected to eccentric load. The ultimate bearing capacity of an eccentrically loaded footing on a reinforced sand slope can be derived from that of axially loaded footing resting on horizontal sand ground when adopting the effective width rule and the coefficient of reduction due to the slope. When increasing the distance between the footing border to the slope crest, for unreinforced and reinforced ground slope by geogrids, the ultimate bearing capacity of footing is no more affected by the slope ground.

Modelling and optimization of ultimate bearing capacity of strip footing near a slope by soft computing methods

This paper presents the results of an investigation into several non-linear machine learning and soft computing-based models, namely, feedforward neural network (FFNN), radial basis neural network (RBNN), general regression neural network (GRNN), support vector machine (SVM), tree regression fitting model (TREE) and adaptive neuro-fuzzy inference system (ANFIS). The data sets are from extensive finite element modelling (FEM) of a shallow strip footing located near a homogeneous sandy slope. The FEM outputs are used for training and testing the models. Furthermore, the predicted and calculated models are compared and evaluated using different statistical indices and the most accurate model is presented as a simple formula. After model evaluation process the most accurate model is proposed to estimate the solution. The predicted results are compared with the FEM data, and a good agreement is obtained representing good reliability for FFNN (R2 = 0.9233 for training and 0.9095 for testing) solutions in this study. Moreover, the soft computing model is presented as a simple formula and excellent agreement is obtained representing a high degree of reliability for the proposed model.

Bearing capacity of foundations on rock mass using the method of characteristics

SummaryThe method of stress characteristics has been used for computing the ultimate bearing capacity of strip and circular footings placed on rock mass. The modified Hoek‐and‐Brown failure criterion has been used. Both smooth and rough footing‐rock interfaces have been modeled. The bearing capacity has been expressed in terms of nondimensional factors Nσ0 and Nσ, corresponding to rock mass with (1) γ = 0 and (2) γ ≠ 0, respectively. The numerical results have been presented as a function of different input parameters needed to define the Hoek‐and‐Brown criterion. Slip line patterns and the pressure distribution along the footing base have also been examined. The results are found to compare generally well with the reported solutions.

Bearing Capacity of Foundations with Inclusion of Dense Sand Layer over Loose Sand Strata

The lower- and upper-bound finite-element limit analysis in conjunction with second-order conic programming (SOCP) was used to estimate the ultimate bearing capacity of strip and circular footings with an inclusion of a layer of dense sand over existing loose sand strata. The analysis followed the Mohr-Coulomb yield criterion and an associated flow rule. The results are expressed in terms of an efficiency factor that increases quite significantly with increases in the (1) thickness and (2) friction angle of the upper densified layer. While keeping the same thickness of the upper dense sand layer, the circular footing exhibits greater efficiency-factor values as compared to strip footing. The numerical results compare well with data available from the literature. (C) 2017 American Society of Civil Engineers.

An Investigation on the Estimation Methods for the Equivalent Mohr-Coulomb Strength Parameters of Generalized Hoek-Brown Rock Mass

Many practical engineers are often accustomed to understanding the strength of the rock mass in terms of friction angle and cohesion. Therefore, it is necessary to provide a resonable tool implementing the Generalized Hoek-Brown (GHB) failure condition in the framework of the Mohr-Coulomb (M-C) criterion. In this study, the features of Lee (2015) and Hoek et al. (2002) methods for calculating the equivalent friction angle and cohesion of GHB rock masses were briefly reviewed. Subsequently, in order to compare the accuracy of the two methods, the ultimate bearing capacity of strip footing resting on the M-C rock mass was assessed by performing the 2D FE analysis incorporating the equivalent M-C strength constants from both approaches. The results show that Lee (2015)’s method, which exploits the upper bound solution of ultimate bearing capacity, is superior to that of Hoek et al. (2002)’s approach.

기초의 크기효과에 관한 수치해석

Abstract Finite element analyses were conducted to investigate the size effect on the bearing capacity and settlementof shallow foundations, and the results were compared with those of theoretical equations. The calculated bearing capacity of the plate by numerical analysis and the theoretical equation was similar. Numerical analyses showed thatthe ultimate bearing capacity of strip footing on sand was affected by the size effect, whereas the ultimate bearingcapacity of strip footing on clay was not affected by the size effect. Numerical analyses showed that the square footing was unaffected by the size effect regardless of the type of foundation soil. In contrast to theoretical equations,settlement of the footing was affected by the size effect and was proportional to the footing width. Key Words : Size effect, Finite element analysis, Plate, Strip footing, Square footing * Corresponding Author : Jin-Tae Han(Korea Institute of Construction Technology)Tel: +82-31-910-0259 email: jimmyhan@kict.re.krReceived July, 29, 2014 Revised(1st September, 25, 2014, 2nd October, 1, 2014) Accepted January, 08, 2015

Stochastic analysis of ultimate bearing capacity of strip footing considering spatial variability of undrained shear strength

Stochastic analysis of ultimate bearing capacity of strip footing considering spatial variability of undrained shear strength

Comparison of Analytical Solutions with Finite Element Solutions for Ultimate Bearing Capacity of Strip Footings

The finite element method is used to compute the ultimate bearing capacity of a fictitious strip footing resting on the surface of c-φ weightless soils and a real strip footing buried in the c-φ soils with weight. In order to compare the numerical solutions with analytical solutions, the mainly existing analytical methods are briefly introduced and analyzed. To ensure the precision, most of analytical solutions are obtained by the corresponding formulas rather than table look-up. The first example shows that for c-φ weightless soil, the ABAQUS finite element solution is almost identical to the Prandtls closed solutions. Up to date, though no closed analytical solution is obtained for strip footings buried in c-φ soils with weight, the numerical approximate solutions obtained by the finite element method should be the closest to the real solutions. Apparently, the slip surface disclosed by the finite element method looks like Meyerhofs slip surface, but there are still some differences between the two. For example, the former having an upwarping curve may be another log spiral line, which begins from the water level of footing base to ground surface rather than a straight line like the latter. And the latter is more contractive than the former. Just because these reasons, Meyerhofs ultimate bearing capacity is lower than that of the numerical solution. Comparison between analytical and numerical solutions indicates that they have relatively large gaps. Therefore, finite element method can be a feasible and reliable method for computations of ultimate bearing capacity of practical strip footings.

Model studies of bearing capacity of strip footing on sand slope

An experimental investigation into the ultimate bearing capacity of strip footing on sand slope is reported. The parameters investigated are the effect of setback distance of the footing to the slope crest, slope angle, relative density of sand and footing width on the ultimate bearing capacity of strip footings. A series of finite element analyses was additionally performed on a prototype slope to ascertain the validity of the findings from the laboratory model tests and to supplement the results of the model tests. The agreement between observed and computed results is found to be reasonably well in terms of load-settlement and general trend of behavior. The results show that the ultimate bearing capacity increases with increase in setback distance, relative density of sand, footing width and decrease in slope angle. At a setback distance of five times of the width of the footing, bearing capacity remains constant like that of a footing on level ground.

Bearing Capacity of Shallow Foundation on Two Clay Layers by Numerical Approach

Natural soils are often deposited in layers. The estimation of the bearing capacity of the soil, using conventional bearing capacity theory based on the properties of the top layer, introduces significant inaccuracies if the thickness of the top layer is comparable to the width of the rigid footing placed on the soil surface. Saturated normally consolidated and lightly overconsolidated clays indicate that under undrained condition the cohesion of soil mass increases almost linearly with depth. A few theoretical studies have been proposed in the literature to incorporate the variation of cohesion with depth in the computation of the ultimate bearing capacity of strip and circular footings. In this paper, after reviewing previous works, numerical computations using the FLAC code (Fast Lagrangian Analyses of Continua) are reported to evaluate the two layered clays effect on the bearing capacity beneath rigid strip footing subject to axial static load. The results of the bearing capacity relating to the relative thickness of the top layer, the strength ratio of the soil two-layered clays and the rates of the increase of soil cohesion with depth are presented in Tables and graphs. The obtained results are compared with previous published results available in the literature.