Bearing Capacity Factor Research Articles

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.

Numerical analysis of shape coefficients and bearing capacity factors of shallow foundations on heterogeneous soil

We often face heterogeneous foundation soils in geotechnics, which significantly influence shallow foundations' shape coefficients and bearing capacity factors. The evaluation of these factors introduces significant uncertainties in the thickness of the upper layer is comparable to the width of the rigid footing placed on the soil surface. This ambiguity depends on the geometry of the footing, the mechanical properties of the soil, and other geotechnical factors. Conducting thorough geotechnical studies and performing specific analyses are essential to accurately assess the effect of clay layering on the shape coefficients and bearing capacity factors of circular and square footings. A numerical analysis using the FLAC 2D and 3D software is carried out to evaluate the effect of the superposition of two undrained clay layers on the bearing capacity and shape factors of circular and square footings subjected to a static axial load. The aspects of homogeneous and heterogeneous shear strength profiles were addressed at various positions of the height of the first clay layer. It was found that the critical depth of the first clay layer necessary to optimize the bearing capacity of a foundation resting on stratified soil is 2, 1.5, and 1, respectively, for strip, square, and circular footings. The shape coefficient values range between 1.14 and 1.22 for square footings and between 0.98 and 1.64 for circular footings. The results are compared to previously published values in the literature.

The performance of waste glass aggregate concrete GFRP-steel double-skin tubular columns under axial compression: Experimental study

In an attempt to alleviate the problem of growing waste glass and fully utilize the excellent material properties of fiber-reinforced polymer (FRP), a novel composite structure, waste glass aggregate concrete glass fiber reinforced polymer (GFRP)-steel double-skin tubular column (WGAC-DSTC), was proposed based on the FRP-concrete-steel double-skin tubular column (DSTC). In the present research, eight WGAC-DSTCs and four waste glass aggregate concrete-filled GFRP tubular columns (WGAC-CFFTs) were investigated to explore their mechanical performance under axial compression. Effects of diverse replacement ratio of waste glass aggregate, GFRP tube thickness, and hollow ratio of column on the mechanical performance of twelve columns were investigated. Meanwhile, this research analyzed and discussed the failure characteristics of columns, load-displacement relationship, ductility coefficient, stiffness coefficient, parameter analysis, ultimate bearing capacity, load-strain relationship and constraint factor. Besides, predicted formulae for estimating the ultimate bearing capacity of WGAC-CFFTs and WGAC-DSTCs were proposed. The research results indicated that (1) Failure mode of the WGAC-DSTCs displayed axial compression failure or shear failure and failure mode of WGAC-CFFTs exhibited mainly axial compression failure; (2) WGAC-DSTCs with 10 % replacement ratio of waste glass aggregate and hollow ratio of 0.4 indicated an increase in the ultimate bearing capacity by 17.24 % and 45.78 %, respectively, as the GFRP tube thickness increased from 1.5 mm to 2 mm and 3 mm. As the column's hollow ratio enhanced from 0.27 to 0.68, the column's ultimate bearing capacity significantly decreased by 7.08 %-60.55 %. The ultimate bearing capacity of WGAC-CFFTs showed a trend of first increasing by 8.33 %-9.41 % but then decreasing by 1.52 % when the replacement ratio of waste glass aggregate rose from 0 % to 30 %; (3) WGAC could replace natural aggregate concrete in traditional DSTC and the bearing capacity could be guaranteed. Besides, it's recommended to utilize 20 % replacement ratio of waste glass aggregate for the WGAC-DSTC whose ultimate bearing capacity enhanced by 15.17 % and possessing optimal mechanical performance; (4) The results calculated utilizing predicted formulae matched well with results of experiment. The application of waste glass aggregate concrete in DSTC can contribute to economic growth and environmental protection and meet the concept of sustainable development.

Hybrid artificial neural network models for bearing capacity evaluation of a strip footing on sand based on Bolton failure criterion

This paper employs the Bolton failure criterion, incorporating strength-dilatancy relationships, to analyze the bearing capacity factor of a strip footing on dense sand. Utilizing finite element limit analysis (FELA) based on the lower and upper bound theorems, the study presents the results as average bound solutions. By using the Bolton model, the b parameter is first calibrated and found that it should be about 3.50 to align the ultimate bearing capacity (qu) from FELA to have a good agreement with that from experimental test results from previous studies. The influence of parameters relevant to the Bolton failure criterion is analysed, showing that an increase in relative density (DR) significantly affects the variation in the bearing capacity factor (Nγ) at higher Q values, while lower Q values inhibit dilatancy due to soil crushing. The width of the strip footing (B) has a decreasing effect on Nγ at higher Q values, and the unit weight (γ) changes minimally impact Nγ within the range of 16–22 kN/m3. Additionally, an increase in the critical state friction angle (ϕcv) consistently increases Nγ, highlighting its direct correlation with soil shear strength. A hybrid artificial neural network (ANN) model integrates machine learning with four optimization algorithms: Imperialist Competitive Algorithm (ICA), Ant Lion Optimization (ALO), Teaching Learning Based Optimization (TLBO), and New Self-Organizing Hierarchical Particle Swarm Optimizer with Jumping Time-Varying Acceleration Coefficients (NHPSO-JTVAC). Comparative rank analysis of hybrid ANN models based on the selection of the optimal number of hidden neurons demonstrates that the ANN-TLBO model excels in predicting the bearing capacity factor, achieving a score of 48. This conclusion is corroborated by an error heatmap matrix, which indicates a minimized percentage of error relative to other hybrid ANN models. Importance analysis identifies particle crushing strength (Q) as the most significant factor influencing the bearing capacity factor (Nγ).

Effect of soil spatial variability on the stability of pipelines under horizontal loading

Submarine pipeline has been utilized more and more widely in offshore oil and gas transportation engineering. Given that these pipelines frequently subject horizontal loading during operation, thus precise predicting their horizontal bearing capacity is essential. However, most previous studies employ deterministic analysis without considering soil spatialvariability. This article introduces a two-dimensional (2D) random finite element analysis to study the horizontal pullout behaviour and failure mechanisms of a pipeline in a spatial variability soil. It is observed that the effect of soil spatial variability on the horizontal bearing capacity factor and failure mechanisms is remarkably substantial, with the distribution of the former showing a close approximation to a log-normal distribution. Furthermore, the average horizontal bearing capacity typically falls below the corresponding deterministic value. Consequently, the deterministic estimation of the horizontal bearing capacity tends to be inflated. Eventually, a reliability-based approach is formulated, where a factor of safety is incorporated to account for the uncertainties arising from spatial variability and ensure a sufficient safety margin. This methodology enables engineers to determine appropriate factor of safety tailored to the specific requirements of each project.

FELA evaluated bearing capacity factors for circular, planar, and interfering cutting edges of open caisson

ABSTRACT In the study, a thorough analysis of the drained bearing capacity factors of cutting edges of open caissons with and without interference has been carried out which helps in planning the controlled sinking of caissons. Five different conditions are analysed in this study: single circular, single planar, V-shape planar, interfering planar, and interfering V-shape planar cutting edges. Implementing upper and lower bound finite element limit analysis (FELA) in accordance with Terzaghi's conventional bearing capacity equation, the bearing capacity factors of the cutting edge of open caissons are evaluated. The design charts for the bearing capacity of cutting edges are determined by accounting for the effects of the radii ratio of the circular caisson, distance ratio of planar cutting edges, cutting angle of cutting edge, soil internal friction angle, and spacing between the cutting edges. The soil failure planes corresponding to the aforementioned aspects of the cutting edges are also evaluated.

Experimental studies on lateral bearing capacity of modified tripod suction caissons for offshore wind turbines in silty clay

In recent years regular tripod suction caissons are commonly used in offshore wind farm projects because of economic feasibility and environment-friendly work principles. The design of a modified tripod suction caisson composed of three caissons with different diameters can improve the capacity behaviour in the direction of strong wind within a considered construction cost. This paper carried out model tests to study the lateral bearing capacity of modified tripod suction caissons in silty clay. Based on the equilibrium equation of vertical force of modified tripod suction caissons the average vertical subgrade reaction modulus is proposed to investigate the relationship between it and rotation, which is of paramount importance to the nonlinear lateral bearing capacity. The results show that the range of bearing capacity factors increases with the increasing effective diameter-height ratio indicating that modified tripod suction caisson with reasonable combinations can effectively improve its bearing capacity in a certain loading direction. The sum of the bearing capacity factors of three monopod suction caissons falls in the range of the capacity factors of the tripod foundation consisting of the above caissons. Suction under the lid increases with the increasing lateral load and seems to be not related to the combinations of suction caissons with different diameters. By fitting the experimental data, it is found that there is a power exponential relationship between the average vertical subgrade reaction modulus and rotation of the foundation.

Influence of the ribbed steel core on the inner interface mechanical behavior of the ESDCM pile

By virtue of the high strength, cost-efficiency and green construction, the expanded stiffened deep-cement-mixing (ESDCM) piles with steel cores own a great prospect to be applied for soft soil treatment in coastal and riverside regions. The dual-interface feature is a crucial factor affecting the bearing capacity of the ESDCM piles. However, the confining pressure characteristics of pile cores and the interface characteristics of steel pipe-soil-cement are unclear, limiting the practical application of ESDCM piles. Hence, in this work, we investigate the mechanical characteristics of the inner interface of ESDCM piles with steel cores via confining pressure transfer test and inner interface shear tests. The results demonstrate that the soil-cement column can withstand over 90 % of the confining pressure exerted on the outer interface, suggesting that the pile core may not be affected by confining pressure. Model piles with different steel cores have different interface failure modes, which can be described using either a three-segment or two-segment constitutive equation. Changing the inner interface structure has been proven to be a highly efficient pathway for enhancing the bearing capacity and adhesion conversion factor of the ESDCM pile. Compared with the smooth steel cores, the adhesion conversion factor can be reinforced up to 114.3 % by employing ribbed steel cores. Then, a model-pile bearing capacity calculation formula was established and verified for reliability. Moreover, the formula of a single pile based on inner interface shaft resistance was further proposed in combination with the actual operating conditions. This study highlights the mechanical characteristics of the inner interface of ESDCM piles, which guides engineering design and construction.

Large deformation assessment of the bearing capacity factor for rigid footing: effect of soil heterogeneity

Large deformation assessment of the bearing capacity factor for rigid footing: effect of soil heterogeneity

Bearing capacity evaluation of embedded circular footing considering presence of an overload adjacent

The bearing capacity of axially loaded embedded foundations has been widely studied using analytical and numerical methods. However, there are many discrepancies in the literature results regarding the bearing capacity factors and depth factors of circular embedded footings proposed by different authors. Terzaghi's hypothesis has been used to assess the bearing capacity of shallow foundations and several analytical solutions have been proposed for computing bearing capacity factors, even though a superposition of individual contributions may lead to some error in the computed bearing capacity. This assumption has sometimes been criticized as being more conservative. This article aims to study two problems; The first part is focuses on the numerical evaluation of the superposition hypothesis in the calculation of the bearing capacity for rough circular foundations embedded in sand. In this section, the bearing capacity factors contributing to the conventional solution have been evaluated and superposition errors are indicated and compared with those found by different authors. The latter part of the work is devoted to studying the depth effect on the estimation of the bearing capacity of a rough circular footing embedded in the sand considering presence of an overload adjacent. For both analyses, the finite-difference code Flac2d (FLAC 2007) was used to reach the bearing capacity for embedded circular footings, the ground friction angles are between 25° and 40° and a depth ratio Df/D varies from 0.1 to 2. The calculation results are presented in tables and graphs and compared to previously published results available in the literature.

Soft Computing-Based Models for Estimating Undrained Bearing Capacity Factor of Open Caisson in Heterogeneous Clay

Soft Computing-Based Models for Estimating Undrained Bearing Capacity Factor of Open Caisson in Heterogeneous Clay

Effect of padeye offset ratio on keying behaviours and capacity of square plate anchors in clay

This paper reports the effect of padeye offset ratio on the keying behaviours and capacity of square plate anchors in clay. The investigation is conducted through three-dimensional large deformation finite element analyses using the Remeshing and Interpolation Technique with Small Strain in ABAQUS. Strain rate dependency of the undrained shear strength and soil remoulding are accounted for adopting an extended Tresca model. The results from LDFE analyses are compared with existing analytical solutions, centrifuge test data, and numerical results; with reasonable agreement obtained. Parametric analyses are then carried out varying several critical factors including initial embedment depth, load eccentricity, padeye offset ratio, soil sensitivity, and soil strength heterogeneity. It is seen that the padeye offset has significant influence on the ultimate loss of embedment and capacity under vertical loading. To assess the keying behaviour of square plate anchors in clay, an equivalent soil strength incorporating strain rate dependency and remoulding is adopted. A combined factor defined as a function of the initial embedment depth and equivalent soil strength is used to estimate the ultimate loss of embedment. An equivalent ultimate bearing capacity factor is shown to be a function of the initial embedment depth, padeye offset ratio, and load eccentricity.

Finite element and evolutionary polynomial regression analyses of the effect of a cavity on the bearing capacity factor $${{\varvec{N}}}_{{\varvec{c}}}$$ of strip footing

Finite element and evolutionary polynomial regression analyses of the effect of a cavity on the bearing capacity factor $${{\varvec{N}}}_{{\varvec{c}}}$$ of strip footing

Probabilistic design optimization of rectangular skirted mudmats under combined loading in spatially variable soil

Natural soil exhibits inherent spatial variability due to complex physical and chemical formation processes, making it necessary to analyze, evaluation and design foundations using probabilistic method. In this study, the bearing capacity of rectangular skirted mudmats in spatially variable soil is investigated by three-dimensional random finite element analysis (3D-RFEA). Given the high computational cost of 3D-RFEA, an active learning probabilistic method based on Kriging surrogate model is proposed to predict the mean and coefficient of variation of bearing capacity factor of mudmats. Then, considering the effects of the skirt depth ratio of mudmats and the variation coefficient and scales of fluctuation of the undrained shear strength of soil, a prediction model of probabilistic failure envelope is proposed by combining the normalized deterministic failure envelope and the cumulative distribution function (CDF) of the uniaxial bearing capacity factor. Based on the prediction model of probabilistic failure envelope, an example of probabilistic design optimization of mudmats is finally given. Compared with the normative method, the design method based on the prediction model can design mudmats directly with the permissible failure probability.

Semi‐analytical solution for ultimate bearing capacity of smooth and rough circular foundations on rock considering three‐dimensional strength

AbstractThis paper proposes a semi‐analytical solution for the ultimate bearing capacity qu of both smooth and rough circular shallow foundations on rock mass. Specifically, a three‐dimensional (3D) Hoek–Brown (HB) is adopted, in conjunction with equilibrium equations under axisymmetric conditions, to derive the governing equations. The method of characteristics is utilized to solve the stress and failure characteristics mesh to determine the qu. The proposed solution is verified by using it to analyze test foundations. Comparison with an HB criterion‐based solution is performed to highlight the importance of 3D strength. Furthermore, parametric studies are performed to investigate the effects of rock mass properties (intact rock constant , geological strength index GSI, intact rock unconfined compressive strength σc) and foundation diameter (B) on the qu, failure surface size, and vertical stress distribution on the foundation base. The results indicate that ignoring the 3D strength and the rock mass weight would lead to underestimation of qu. Besides, the ultimate bearing capacity factor (ratio of qu to σc) increases with , GSI and B but decreases with . The failure surface size is significantly affected by , GSI, B, and rock mass unit weight. The stress distribution on the foundation base has higher variance (higher possibility of stress concentration) at smaller , GSI, and larger B, rock mass unit weight.

Fast Lagrangian analysis of the short-term bearing capacity of shallow foundations in clays on the basis of the cone penetration test

Based on a numerical modelling of the cone penetration test CPT as well as the vertical response of shallow foundation in saturated clays, derivation of the cone factor Nk led to propose a CPT-based method of computation of the bearing capacity. This study was carried out by launching a detailed parametric study using the software FLAC-2D (Fast Lagrangian Analyses of Continua) based on the finite difference method. The soil material was modeled as a homogeneous elastic-perfectly plastic medium obeying the Mohr-Coulomb criterion, and the effects of the soil rigidity index Ir, the cone-soil interface, and the initial depth of the penetration on the cone factor Nk were investigated leading to an analytical formulation of Nk. After a comparative study with those proposed in the literature, the cone factor Nk was used to derive the bearing capacity factor Kc of a shallow foundation. Compared to current CPT-based methods proposed in the literature, this method reasonably predicts the short-term bearing capacity of shallow foundations in saturated clayey soil.

Bearing Capacity Factors of Helical Piles Embedded in Cohesive Soils

Bearing Capacity Factors of Helical Piles Embedded in Cohesive Soils

A large deformation finite element investigation of SEPLA: Failure mechanism and bearing capacities when loaded differently

The Suction Embedded Plate Anchor (SEPLA) is an innovative deep-sea anchoring measure with precise positioning, easy installation, and high anchoring capacity. Most current research on SEPLA revolves around vertical pullout mechanism and thus its vertical bearing capacity. There are relatively few studies concerning its bearing behavior and failure mechanism when SEPLA is subjected to horizontal and moment loading. The latter is practically relevant when SEPLA is exposed to extreme environmental conditions or keyed under preloading. A more in-depth understanding of its failure mechanism under horizontal and moment loading is thereby equally important. In this work, the Coupled Eulerian-Lagrange (CEL) method is used to conduct large-deformation finite element analyses of SEPLA under vertical, horizontal, and moment loading. Emphasis is placed on ascertaining the dissimilarity of soil flow and failure mechanisms when SEPLA is loaded in different directions. Parametric investigation is done to explore the effect of anchor shape and thickness, embedment depth, and soil-anchor interfacial roughness. Semi-theoretical closed form solutions are developed to estimate the uniaxial bearing capacity factor of plate anchors in three directions. These research outcomes are likely helpful in deepening the understanding of SEPLA failure mechanism when loaded in different directions and obtaining more rational estimates of anchor bearing capacity.

Experimental analysis of the behavior of capping beams across the piles in loose sand

The test program was conducted on 1G models capping beams over the tops of the group of 2x2 piles, the purpose of which was to reduce the settlement of the structure. The test program included six experiments, three of which were conducted on capping beams without piles and three on capping beams across the tops of the piles, with pile distances 3d, 4d and 5d, where d is the pile diameter and the pile length is 40 d. Test results show that the current conventional approach to the design of capping beams across the tops of the piles, where the entire load is entrusted to the piles, is too conservative and irrational. Instead, it is more economical to apply a low bearing capacity factor for piles as settlement reducers and maximize use of raft bearing capacity to carry part of the external load.

Bearing capacity factor for strip foundations on unsaturated clay

ABSTRACT The matric suction in unsaturated soil depends on the type of soil and various flux conditions i.e., infiltration, evaporation and no flow. The shear strength of unsaturated soil changes with change in matric suction leading to varying resistance of soil under various flow conditions. In this study, the bearing capacity of strip foundations resting over unsaturated clay considering variation of matric suction with depth for different surface flux conditions and position of water table, has been obtained using finite element lower bound limit analysis. Modified Mohr-Coulomb yield criteria based on unified effective stress approach has been employed to incorporate the contribution of matric suction stress to the failure condition. A non-dimensional bearing capacity factor was introduced to estimate the bearing capacity of strip foundations and presented as a function of different influencing parameters such as foundation width, water table depth, soil properties, various flow conditions and their flow rate, and surcharge pressure. The influence of variation of unit weight of soil in the unsaturated zone, air entry and pore size distribution parameters, residual degree of saturation of soil, specific gravity of soil solids, and foundation-soil interface roughness on the bearing capacity has also been examined and found to be insignificant.