Capacity Of Strip Footings Research Articles

Seismic Bearing Capacity of Strip Footing on Excavations Considering Soil Strength Anisotropy Using Modified Pseudo‐Dynamic and Pseudo‐Static Approaches

ABSTRACTAlthough considerable research has explored the static and seismic bearing capacity of strip footings on slopes or excavations, the influence of clay strength anisotropy on the bearing capacity of strip footing near excavations, specifically considering pseudo‐dynamic conditions, remains unexplored. This study used the finite element limit analysis (FELA) method to evaluate the impact of clay strength anisotropy on the seismic bearing capacity of strip footings. The effects of various dimensionless parameters on the bearing capacity were examined, which include shear wavelength, the setback distance ratio, vertical height ratio, soil strength ratio, soil strength heterogeneity, anisotropic ratio, and horizontal and vertical acceleration coefficients. Design charts were developed to compute the seismic bearing capacity of strip footings on nonhomogeneous and anisotropic excavations under pseudo‐static conditions. Furthermore, the effects of vertical acceleration coefficients and shear wavelength on the seismic bearing capacity of strip footing near excavation in nonhomogeneous and anisotropic soils were investigated.

Drained Bearing Capacity of Strip Footings on Two-Layered Sand Soil Slope

Drained Bearing Capacity of Strip Footings on Two-Layered Sand Soil Slope

Effects of inclined loads on strip footings with an underlying tunnel

The self-developed Finite Element Limit Analysis (FELA) code was utilized to examine the ultimate bearing capacity of strip footings positioned above tunnels affected by inclined loads. Bearing capacity factors were predicted using both upper bound (UB) and lower bound (LB) solutions, with a variance of less than 3 %. The primary focus of this study lies in assessing the influences of underlying tunnels and inclined loads on potential failure modes. In particular, the concept of failure envelopes was introduced, by which the load properties (inclination angle), the tunnel location (relative lateral distance and longitudinal distance from the footing) and the material properties of rock masses (GSI, mi, sci, g) were involved in to facilitate preliminary designs. In addition to envelopes, the transition among failure patterns was summarized, resting with any possible factors.

Estimation of ultimate bearing capacity of strip footings on cohesive-frictional soils using non-linear shear strength model

This study widely investigated the applicability of the ultimate bearing capacity formula from the Architectural Institute of Japan (AIJ) while considering the effect of footing width. An in-house RPFEM program was developed using a non-linear shear strength model that is sensitive to confining stress. The research focuses on evaluating how footing width and soil properties affect the ultimate bearing capacity of strip footings. Coefficients within the AIJ formula were calculated and compared to those derived from the RPFEM, considering different combinations of cohesive and frictional soil strengths across various footing widths. The RPFEM results closely matched those obtained from the AIJ formula. This suggests that using a non-linear shear strength model can accurately estimate the ultimate bearing capacity of strip footings on cohesive-frictional soils, taking into account the footing width.

Probabilistic Analysis of the Seismic Bearing Capacity of Strip Footings Using RAFELA and MARS

Probabilistic Analysis of the Seismic Bearing Capacity of Strip Footings Using RAFELA and MARS

A numerical investigation into the equivalent parameters of a compressible soil treated by stone columns

A series of triaxial test simulations are adopted to estimate the equivalent strength parameters for compressible soil samples reinforced with stone columns. The simulations utilize the finite difference code, Fast Lagrangian Analysis of Continua in three dimensions FLAC3D. An elasto-plastic model is applied to utilize a Mohr-Coulomb yield criterion. The equivalent strength parameters are estimated using newly proposed formulas for geo-composite materials. The researchers compare the obtained results to the analytical formulas proposed in the literature. Additionally, the equivalent parameters are used in equivalent area models. This study investigates the effect of the replacement area ratio. This study offers two applications. Firstly, it evaluates the safety factor of embankments constructed on compressible soil improved with stone columns. Secondly, it estimates the bearing capacity of strip footings on compressible soil treated with stone columns. In all applications, both individual column and equivalent area models are considered. The proposed equations for the equivalent elastic parameters (E, ν) and the mechanical properties, equivalent cohesion, and internal frictional angle (c and φ) give results that agree with the solutions reported in the existing literature.

Appraisal of numerous machine learning techniques for the prediction of bearing capacity of strip footings subjected to inclined loading

Appraisal of numerous machine learning techniques for the prediction of bearing capacity of strip footings subjected to inclined loading

Seismic bearing capacity of strip footings placed on reinforced soil slopes using slip line method

This study investigates the seismic vertical bearing capacity of strip footings positioned on reinforced soil structures employing a two-phase approach and the slip line method. The investigation aims to establish a slip line field and determine the critical slip surface without any assumptions of predefined surfaces. The obtained results are compared with previous studies, demonstrating a good agreement and validating the accuracy of the proposed approach. The variation of the bearing capacity factor with the horizontal seismic coefficient, soil internal friction angle, setback distance normalized by footing width, and slope incline angle. An increase in the horizontal seismic coefficient leads to a decrease in bearing capacity factor, while an increase in the soil internal friction angle has the opposite effect. The influence of the setback distance on the bearing capacity is also examined, highlighting significant improvements with increased setback distances. Additionally, the study investigates the impact of the tensile strength ratio and setback distance on the ultimate bearing capacity factor and the bearing capacity ratio. The distribution of reinforcement forces beneath the footing is analyzed and presented through contour plots, providing valuable insights into the seismic behavior of footings on reinforced soil slopes.

Seismic Bearing Capacity of Strip Footings with Modified Pseudo-dynamic Method

Current research has shown a nonlinear trend in the failure of soil, and the single tangent method is commonly adopted when coping with nonlinear problems of soil failure. However, the method equates a nonlinear criterion to an optimizable linear criterion, which may differ from the actual situation, resulting in conservative results. In this paper, two types of piece-wise log-spiral failure mechanisms for bearing capacity estimations, including symmetrical and unilateral mechanisms were proposed with the nonlinear Mohr-Coulomb criterion. The static bearing capacity of foundations was evaluated using the symmetric failure mechanism, while the seismic bearing capacity of foundations was evaluated adopting a modified pseudo-dynamic method based on the unilateral failure mechanism. The result shows that the bearing capacity calculated in the paper is smaller compared to the result using the linear Mohr-Coulomb criterion. For London clay, the static bearing capacity is reduced by about 45% at a foundation width equal to 1m. From the comparisons, it is found that the proposed approach of piece-wise log-spiral failure mechanism for bearing capacity estimation is effective. In addition, parametric studies show that the nonlinear parameters, the initial factor of seismic acceleration, the normalized frequency, and the damping ratio all have obvious effects on the seismic bearing capacity. A significant reduction in the seismic bearing capacity of the foundation occurs when the normalized frequency ωsH/Vs is equal to (0.5 + n)π (n = 0, 1, 2, …). Considering that the approach proposed provides a strict upper bound to the bearing capacity, the result imparts confidence in the approach of analysis presented.

Experimental Investigation for Failure Mechanism and Bearing Capacity of Strip Footing on Soil Reinforced with Geotextile Following the Shukla's Wraparound Reinforcement Technique

Experimental Investigation for Failure Mechanism and Bearing Capacity of Strip Footing on Soil Reinforced with Geotextile Following the Shukla's Wraparound Reinforcement Technique

Bearing capacity of strip footings seated on unreinforced and reinforced granular layers over random homogeneous and isotropic spatially variable undrained soft clay

The bearing capacity of a footing seated directly on a soft clay foundation with constant undrained shear strength is the classical Prandtl geotechnical problem. However, a footing seated directly on an undrained clay soil is an unlikely arrangement in practice. Rather, a granular layer is used as a working platform for the construction of the footing and to dissipate the footing loads over a wider area of the clay foundation surface. This paper revisits the footing problem for the case of a footing seated directly on the clay foundation, and seated on an unreinforced and geosynthetic reinforced granular layer overlying the clay foundation. Both deterministic and stochastic numerical modelling of the bearing capacity problem using the program FLAC 2D were carried out. The relationship between the design factor of safety and probabilistic margins of safety is explored for clay foundations with random homogenous and isotropic spatially variable undrained shear strength with mean strengths from 5 to 25 kPa (very soft to soft clay). For practical target probabilistic margins of safety against exceeding a design bearing capacity, the random homogenous soil condition is shown to be the most critical case for design.

Optimized neural network-based state-of-the-art soft computing models for the bearing capacity of strip footings subjected to inclined loading

Determining the bearing capacity of a strip footing under inclined loading is crucial in designing foundations. Due to the complex correlations, the subject area remains predominantly unexplored, or it has been simulated using only limited datasets. This paper presents the development of a prediction model based on machine learning (ML), leveraging advanced hybrid artificial neural network (ANN) models for estimating the bearing capacity of strip footings under inclined loading. The ANN models are hybridized with four different optimization algorithms, ant colony optimization (ACO), artificial lion optimization (ALO), the imperialist competitive algorithm (ICA), and shuffled complex evolution (SCE), which enhance the accuracy and efficiency of the predictive capabilities of ANN. The models are trained on a dataset of 920 records, and their performance is evaluated using a range of significant performance metrics. The ANN-ICA model achieved the highest rank in the score analysis (R2 =0.912, RMSE=0.165 in testing), followed by ANN-ALO and ANN-ACO. To reinforce the trustworthiness of the predictions, external validation is employed, and visual analysis is conducted using the Taylor diagram. The findings suggest that the proposed models are robust, and the incorporation of optimization techniques has improved the performance of traditional ANNs. The research findings have significant implications for the field of geotechnical engineering, providing engineers and researchers with valuable insights into the applicability of hybrid artificial neural network (ANN) models and alternative machine learning (ML)-based prediction models in assessing the bearing capacity of strip footings.

Ultimate bearing capacity of strip footings on Hoek-Brown rock slopes – A stress characteristics solution

The present study addresses the ultimate bearing capacity of strip footings on rock slopes under seismic conditions. The stress characteristics method (SCM) is combined with the modified pseudo-dynamic (MPD) approach for the intended purpose. Unlike the solutions available in the literature, the generation of the stress characteristics network within the framework of the SCM automates the potential failure mechanism of the slope medium at the limiting state of collapse. The MPD approach enables the analysis to capture realistic earthquake inertia forces induced in the slope, considering the material damping properties of the slope. The non-linear nature of the rock mass strength is captured using the generalized Hoek-Brown failure criterion. The seismic ultimate bearing capacity of strip footings is reported as non-dimensional charts. Additionally, the impact of relevant dynamic characteristics of seismic waves and rock mass properties is thoroughly assessed by conducting a detailed parametric investigation. The results reveal a substantial reduction in the ultimate bearing capacity of footings resting on rock slopes under earthquake conditions. The efficacy of the proposed methodology is validated with the existing solutions reported by various researchers.

On the Potential of Using Random Forest Models to Estimate the Seismic Bearing Capacity of Strip Footings Positioned on the Crest of Geosynthetic-Reinforced Soil Structures

Geosynthetic-reinforced soil structures are often used to support shallow foundations of various infrastructure systems including bridges, railways, and highways. When such infrastructures are located in seismic areas, their performance is linked to the seismic bearing capacity of the foundation. Various approaches can be used to calculate this quantity such as analytical solutions and advanced numerical models. Building upon a robust upper bound limit analysis, we created a database comprising 732 samples. The database was then used to train and test a model based on a random forest machine learning algorithm. The trained random forest model was used to develop a publicly available web application that can be readily used by researchers and practitioners. The model considers the following input factors: (1) the ratio of the distance of the foundation from the edge and the width of the foundation (D/B), (2) the slope angle (β), (3) the horizontal seismic intensity coefficient (kh), and (4) the dimensionless geosynthetic factor, which accounts for the tensile strength of the geosynthetic. Leveraging the model developed in this study, we show that the most important features to predict the seismic bearing capacity of strip footings positioned on the crest of geosynthetic-reinforced soil structures are D/B and kh.

Reliability-based analysis of seismic bearing capacity of shallow strip footings resting on soils with randomly varying geotechnical and earthquake parameters

Seismic bearing capacity of strip footings is a challenging task for geotechnical engineers due to its stochastic framework instigated by the natural uncertainties incorporated into geotechnical properties and earthquake parameters. Consequently, the introduction of the random field theory into reliability analysis may provide power tools to succor designers check how reliable their designs. This paper aims to assess the seismic bearing capacity of shallow strip footings resting on soils with randomly varying parameters. Bearing capacity formulas for purely cohesive and cohesive-frictional soils are considered. The influence of the type of the autocorrelation functions (ACFs), the scale of fluctuations (SOFs) and the coefficient of variation (COV) of the random parameters are investigated. Statistical moments, probability density function (PDF) and failure probability (Pf) of the seismic bearing capacity are computed. It is shown that the Single Exponential (SNE) ACF is the most appropriate function to characterize the spatial variability of the soil properties since it provides conservative results. On other hand, the results indicate that the increase in the coefficients of variation (COV) of the cohesion or the friction angle increases the variability of the seismic bearing capacity while this variability remains unaffected when the COV of the seismic coefficient increases. The results also highlight that the effect of the vertical SOF on the PDF and the failure probability is much more significant than that of the horizontal SOF. In addition, the mean seismic bearing capacity fluctuates slightly as the horizontal or vertical SOF increases so that the increment of variation is between 0.4% and 2% for the both two soil types.

Bearing capacity and failure mechanism of strip footings lying on slopes subjected to various rainfall patterns and intensities

Footing on slope is a prevalent construction encountered in geotechnical engineering, and its safety is receiving increased attention. A natural rainfall event will inevitably have adverse influences on the stability and bearing capacity of strip footings lying on slopes; however, the conventional practice to simulate the rainfall is realized by varying the soil moisture content and the actual rainfall characteristics cannot be fully reflected. As a result, the finite element (FE) software ABAQUS is employed in this study to model the temporally varying rainfall, and the bearing capacity, as well as failure mode of the strip footing placed at the top of slopes, is estimated accordingly. A series of FE analyses are carried out to quantify the influences of rainfall pattern, rainfall intensity, soil strength properties (i.e., effective cohesion c′ and effective friction angle φ′) and several geometric parameters associated with the location of embedded footing with B in width, such as the edge distance ratio L/B and the embedded depth ratio D/B. Results show that the bearing capacity will be decreased and the failure mode evidently changes under rainfall condition. Moreover, it is noted that the rainfall pattern produces less substantial impact on the bearing capacity and failure mode, compared with the rainfall intensity.

An Analytical Framework for Assessing the Unsaturated Bearing Capacity of Strip Footings under Transient Infiltration

The evaluation of the bearing capacity of strip footings generally assumes that the soil is either dry or fully saturated, which contradicts the actual condition in nature where the soil is often in a partially saturated state. Furthermore, infiltration has a significant impact on the shear strength of the soil. Following the upper bound theory of the limit analysis, this article provides a theoretical framework for assessing the bearing capacity under transient flow with linear variation in infiltration intensity for the first time. Firstly, the closed form of suction stress under linear transient infiltration is derived using Laplace transform and introduced into the Mohr–Coulomb criterion. A discrete failure mechanism with fewer variables and higher accuracy is provided to ensure kinematic admissibility. The upper bound solution for bearing capacity is obtained by solving the power balance equation. The present results are compared with results from the published literature and the finite element, confirming the validity and superiority of the theoretical framework provided. A parametric analysis is also conducted on three hypothetical soil types (fine sand, silt, and clay), and the results show that unsaturated transient infiltration has a positive influence on increasing the foundation bearing capacity. The magnitude of the influence is comprehensively controlled by factors such as soil type, saturated hydraulic conductivity, infiltration intensity, infiltration time, and water table depth. The increase in bearing capacity due to unsaturated transient infiltration can be incorporated into Terzaghi’s equation as a separate component presented in tabular form for engineering design purposes.

Ultimate bearing capacity of rigid strip footings on c-ϕ soil subjected to combined eccentric and inclined loading

The present study calculated the maximum bearing capacity of a strip footing against eccentrically inclined coupled loading on c-ϕ soil, by means of the plane strain rigid plastic finite element method (RPFEM). The influence of soil strengths and footing width on the V-H and H-M failure envelopes (presenting the vertical load V, horizontal load H, and moment M) was thoroughly surveyed to assess the uniqueness of the V-H-M failure envelope. Based on the obtained results, the V-H-M failure envelope was found to be distinct for each value of normalized cohesion c/γB and internal friction angle ϕ. A novel equation, which is a function of c/γB and ϕ, was achieved to predict the failure envelope of the V-H-M limit load space.

Seismic Bearing Capacity of Strip Footings Placed Adjacent to Rock Slopes

ABSTRACT The bearing capacity of strip footings placed adjacent to the rock slopes subjected to pseudo-static horizontal earthquake body forces has been investigated by using the upper bound (UB) finite element limit analysis (FELA) in combination with a mesh adaptive strategy. The generalized Hoek–Brown (GHB) failure criterion is applied to describe the strength properties of rock masses, which can be treated as its native form without the smoothing of the yield surface while employing the second-order cone and power cone programming to solve the optimization models. Based on the UB FELA method, the seismic bearing capacity factor is determined considering the effect of different governing parameters, namely the horizontal earthquake acceleration coefficient k h , the normalized slope height H/B, the rock strength ratio σ ci /γB, the geological strength index GSI and the material constant m i . For design purpose, a series of non-dimensional charts are provided, and typical failure mechanisms are also discussed in detail.

Numerical Modeling of the Effect of a Weak Zone on the Bearing Capacity of Strip Footings

Numerical Modeling of the Effect of a Weak Zone on the Bearing Capacity of Strip Footings