Bearing Capacity Of Strip Research Articles

Effect of eccentric and inclined loading on the bearing capacity of strip footing placed on rock mass

Effect of eccentric and inclined loading on the bearing capacity of strip footing placed on rock mass

Seismic bearing capacity of strip footing on partially saturated soil using modal response analysis

Seismic bearing capacity of strip footing on partially saturated soil using modal response analysis

Effect of interface adhesion factor on the bearing capacity of strip footing placed on cohesive soil overlying rock mass

Effect of interface adhesion factor on the bearing capacity of strip footing placed on cohesive soil overlying rock mass

Probabilistic study on the bearing capacity of strip footing subjected to combined effect of inclined and eccentric loads

This paper investigates the importance of inherent variability of soil under strip footing subjected to combined effect of inclined and eccentric loads using probabilistic analysis. Plastic analysis is performed using lower bound formulation of finite element limit analysis. Soil is considered as cohesionless, and modelled as a random field. The random field is discretized using Karhunen-Loéve expansion method. Stochastic results of the collapse load for various conditions of internal friction angle, load inclination angle, eccentricity, vertical correlation distance and coefficient of variation of the tangent of internal friction angle are determined using Monte Carlo Simulation technique. Failure probability results are plotted as contour charts to show the effect of combined loading as well as the spatial variability of soil on the bearing capacity of strip footing. For all the cases of higher vertical correlation distances, the mean bearing capacity factor is found to be higher than the deterministic value. However, the probability of failure of the footing is reported to be more than 50% for the same case, addressing the need for probabilistic analysis. Failure contours are presented for some representative cases to display the behavior of footing due to different loading and spatial variability conditions.

Numerical Investigation of the Bearing Capacity of Strip and Rectangular Shallow Footings on Cohesive Frictional Soils Under Eccentric Loads

Numerical Investigation of the Bearing Capacity of Strip and Rectangular Shallow Footings on Cohesive Frictional Soils Under Eccentric Loads

Effect of Intermediate Principal Stress on the Bearing Capacity of Footings in Soft Rock

The bearing capacity for footings is a fundamental scientific problem in civil engineering. The evaluation of the bearing capacity of footings usually does not take into account the effect of the intermediate principal stress. In practice, the intermediate principal stress has certain influences on the strength of geomaterials (e.g., rock and soil) or concrete. In this paper, a series of numerical solutions are presented to evaluate the bearing capacity of footings in a soft rock foundation via a two-dimensional finite difference code (FLAC) with a strain hardening/softening constitutive model based on the unified strength theory (UST). The values of the bearing capacity factor Nc and Nγ for strip, circular and square footings in a soft rock foundation were evaluated using the strain hardening/softening constitutive model. The effect of the intermediate principal stress on the bearing capacity of strip, circular and square footings in a soft rock foundation was analyzed. The results of the numerical computation show that the intermediate principal stress has a significant influence on the bearing capacity and failure mechanisms of a soft rock medium. The influence of the intermediate principal stress on the peak and residual values of the bearing capacity for a strip footing is much greater than for circular and square footings. Research works for the reasonable estimation of the bearing capacity of footings in soft rock are facilitated by this study.

Effect of geosynthetic reinforcement on the bearing capacity of strip footing on sandy soil

Due to the increasing presence of problematic soils, expansive clays and highly compressive sand engineers are using a verity of soil improvement techniques to treat such soils. While geosynthetics are extensively used for improving soil characteristics in roads, pavements and embankments, it can also be used to increase the lack of bearing capacity of residential housing or lightweight structures constructed on sandy soils. In order to simulate site conditions in the laboratory environment, a laboratory-scale testing platform has been manufactured to assess the behaviour of geosynthetics reinforced and un-reinforced strip footing. The first group of tests were performed on the unreinforced compacted sandy soils with different densities where the other group of tests were carried out in the soil that has been reinforced individually with three different types of geosynthetic materials having distinct tensile strengths. Furthermore, interface direct shear tests and consolidated undrained triaxial tests have been carried out to determine the shear parameters which is directly influencing the bearing capacity a strip footing. Geosynthetic reinforcement has considerably enhanced the mechanical behaviour of sandy soil in regarding the type of geosynthetic. Furthermore, it was observed that coir geosynthetic has provided increased interfacial friction when compared to other geosynthetic types and improved bearing capacity. Moreover, the adopted testing method found to represent well the behaviour of such materials in the laboratory environment.

Effect of inclined and eccentric loading on the bearing capacity of strip footing placed on the reinforced slope

The present study considers the influence of inclined and eccentric loading on the bearing capacity of a strip footing placed on the reinforced cohesionless soil slope by using lower bound finite element limit analysis technique. The effects of other parameters such as soil friction angle, embedment depth of reinforcement layer below the footing, interface friction angle between soil and reinforcement, and vertical spacing between two reinforcement layers are also investigated. Results are presented as the variation between reinforcing efficiency and various combinations of above-mentioned parameters. The bearing capacity of strip footing reduces under combined effects of inclined and eccentric loading. However, with the inclusion of reinforcement layers at the optimum depth, the bearing capacity enhances significantly. The reinforcing efficacy increases with the increasing value of load inclination. The reinforcing efficiency reduces with the consideration of partial roughness between soil and reinforcement layer. Stress contours are also plotted in the two-dimensional object space to understand the failure mechanism of slopes.

Pseudo-static bearing capacity of strip footing with vertical skirts resting on cohesionless slopes by finite element limit analysis

ABSTRACT Using vertical skirts as soil reinforcement in conjunction with strip footing can increase the bearing capacity of a footing located near a cohesionless slope. This paper adopted lower and upper bounds of finite element limit analysis (FELA) to compute the bearing capacity of a strip footing with vertical skirts resting on the cohesionless slope under pseudo-static condition. A wide range of efficient factors on the bearing capacity and the failure pattern are investigated. Design tables are presented to obtain the bearing capacity of a strip footing with vertical skirts resting on cohesionless slopes in terms of bearing capacity ratio (BCR). The results showed that the BCR is improved notably, by using vertical skirts in conjunction with a strip footing in all cases. Furthermore, the BCR is affected markedly by increasing kh . Also, the results of this study are compared with available solutions in the literature.

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.

Probabilistic bearing capacity of strip footing on reinforced anisotropic soil slope

The probabilistic bearing capacity of a strip footing placed on the edge of a purely cohesive reinforced soil slope is computed by combining lower bound finite element limit analysis technique with random field method and Monte Carlo simulation technique. To simulate actual field condition, anisotropic random field model of undrained soil shear strength is generated by using the Cholesky-Decomposition method. With the inclusion of a single layer of reinforcement, dimensionless bearing capacity factor, N always increases in both deterministic and probabilistic analysis. As the coefficient of variation of the undrained soil shear strength increases, the mean N value in both unreinforced and reinforced slopes reduces for particular values of correlation length in horizontal and vertical directions. For smaller correlation lengths, the mean N value of unreinforced and reinforced slopes is always lower than the deterministic solutions. However, with the increment in the correlation lengths, this difference reduces and at a higher correlation length, both the deterministic and probabilistic mean values become almost equal. Providing reinforcement under footing subjected to eccentric load is found to be an efficient solution. However, both the deterministic and probabilistic bearing capacity for unreinforced and reinforced slopes reduces with the consideration of loading eccentricity.

An Investigation on the Effect of Intermediate Principal Stress on the Solution of Bearing Capacity Problems by the Method of Stress Characteristics

This paper aims to investigate the effect of assuming different values of intermediate principal stress σ2, in the solutions obtained for stability problems in soil engineering. The bearing capacity of strip and circular footings has been selected for this purpose which represent typical plane strain and axisymmetric stability problems. Investigations has been made using the method of stress characteristics as usual; but with yield criteria other than Tresca and Mohr–Coulomb that allow variation in σ2. Variation in σ2 has been considered in the form of usual parameter b which is the ratio of differences of principal stresses. At the outset; the parameter b is set to match these criteria with Tresca or Mohr–Coulomb. This is based on usual assumptions of associativity in plane strain, and Haar–von Karman flow-regime in axial symmetry. The value of b has then been changed from these values to see how the solution is affected by variation in σ2. Results indicate that the usual solutions are not generally on the safe side; and if the material behavior is really different from our assumptions, this should be considered in calculations.

Bearing capacity of strip footings on sand over clay

Estimation of the bearing capacity of shallow foundations on layered soil profiles, such as a sand layer of finite thickness over clay, is mainly based on empirical models resulting from the interpretation of experimental test results. While it is generally accepted that such models may be applicable to soil properties and footing geometries outside the range tested experimentally, they offer limited insights on how the assumed failure mechanism affects their range of application. In particular, the contribution of the sand layer to the overall capacity is accounted for via simple considerations, which are valid only for a specific range of problem parameters. This paper addresses the estimation of the undrained bearing capacity of a rigid strip footing resting on the surface of a sand layer of finite thickness overlying clay, using finite element limit analysis (FELA). The rigorous upper and lower bound theorems of plasticity are employed to bracket the true bearing capacity of the footing, and identify the geometry of possible failure mechanisms. Insights gained from FELA simulations are used to develop a new simple bearing capacity model, which captures the variation in shear resistance from the sand layer with the dimensionless undrained strength of the clay layer. The proposed model provides results that are in close agreement with published experimental studies, and allows treating simple problems, such as the design of working platforms, without having to resort to numerical simulations.

Effect of Fuzzy Boundaries on the Bearing Capacity of Footings on Two-Layered Clay

In this study, fuzzy logic was implemented to formulate the fuzziness of layer boundaries for a two-layered clay soil. A field of two-layered clay with fuzzy boundaries between layers was generated, and then the bearing capacity of strip footing on this field was calculated by the assumption of plane-strain conditions. The Mohr-Coulomb failure criterion was used and bearing capacity calculations were based on finite difference method. The effect of fuzziness in layer boundaries was investigated for the case of strong-over-weak clay. It is concluded that the analyses by applying fuzzy boundaries yielded more conservative results than classical two-layered bearing capacity calculations when the ratio of thickness of upper layer to the width of footing exceeds 1. When the ratio of thickness of upper layer to the width of footing is lower than 1, the bearing capacity of footing on two-layered clay is higher by considering fuzzy boundaries.

Bearing Capacity of Strip Footing on Clay Slope Reinforced with Stone Columns

Bearing capacity is very important in geotechnical engineering, which depends on factors such as footing shape, stress distribution under footing and failure mechanism of soil. One of the methods for improving the bearing capacity and reducing settlement in soft and fine soils is adding column like elements to soil which called stone column. In this research using model tests and numerical modeling, the effect of existence and location of stone column on bearing capacity of strip footing near soft clay slope is studied. In fact, reinforced and unreinforced stone columns in different locations are added to slope and the effect of them on load-settlement behavior of strip footing rested on top of the slope was investigated. Group stone columns are also studied, and efficiency of them is investigated. Also numerical modeling is carried out with Plaxis 3D Foundation program, and finally the results of experimental and numerical modeling were compared. Results show that reinforcing clay slope with stone column in all situations leads to increase in bearing capacity of strip footing. Moreover, reinforcing stone columns with encasing cause better performance of stone columns and increase in bearing capacity of footing compared with the same unreinforced stone columns. The maximum effect of stone column on bearing capacity of strip footing occurs when the stone column is located beneath the footing, and with increase in distance between the column and footing, the bearing capacity of footing is decreased.

The Effect of Rigidity of Reinforced Stone Columns on Bearing Capacity of Strip Footings on the Stabilized Slopes

The effect of slope-stabilizing stone columns on the bearing capacity of a rigid strip footing placed on a sand slope has experimentally and numerically investigated in this paper. A broad series of conditions has been tested by varying parameters such as the rigidity of stone columns and their spacing in a row. Different types of stone columns were studied including ordinary stone columns, encased stone columns, and concrete piles. Soil displacement fields were obtained via particle image velocimetry method. The results were analyzed to find qualitative and quantitative relationships among bearing capacity and various parameters. A series of finite-element analyses was additionally carried out on a prototype slope and the findings were compared with the results from the laboratory model tests. They were also used to complement the results of the model tests. The agreement between observed and computed results is found to be reasonably good in terms of load–settlement behavior and optimum parameters. Findings of the study showed that increasing rigidity and decreasing the stone columns spaces result in increasing bearing capacity of footing. This enhancement in bearing capacity is attributed to arching effect of soil between stone columns. The rigidity and spacing of stone columns had a significant effect on soil arching. Moreover, the load–settlement behavior of rigid footing is improved.

A Comparative Study on Bearing Capacity of Shallow Foundations in Sand from N and ϕ

This work presents a comparative study on the bearing capacity of strip, square, circular footings and raft foundations in sand, estimated from the standard penetration resistance, N, and the angle of shearing resistance, ϕ. The net safe bearing capacity estimated directly from N using Teng’s equation is compared with that obtained from ϕ as per IS:6403. Likewise, the net safe settlement pressure determined from IS:8009 (Part 1), based on N, is compared with that attained from the semi-empirical approach of Schmertmann et al. A parametric study quantifies the effects of the standard penetration resistance and the size and depth of foundation on the net safe bearing capacity and the net safe settlement pressure of strip, square, circular footings and raft foundations in sand. Interactive charts are prepared in terms of the standard penetration resistance to highlight the appropriate method for the benefit of civil engineers.

Bearing Capacity of Strip Footings Resting on Granular Soil Overlying Soft Clay

In the present research, an analytical method is applied to determine the bearing capacity of strip footing on two layers of soil. Bearing capacity is calculated according to soil resistance beneath the foundation and a virtual retaining wall method. To determine the bearing capacity of the footing in the said method, the active and passive forces on the retaining wall are considered equal along the edges. The active and passive forces of each of the two soil layers are found, and the results are applied to calculate the footing bearing capacity. Among the many advantages of this method are the possibility to determine depth of the rupture surface beneath the footing, and the ability to study the effects of the soil’s second layer on the footing bearing capacity. This study also examines the effects of soil improvement beneath the footing, as well as the depth and width of the compacted area on bearing capacity. A thorough analysis is conducted on soil layer thickness, soil cohesion and friction angle, footing depth and width, the width of the compacted soil beneath the footing, and the depth of underground water. A MATLAB program was used for calculation and deduction. In order to study the effects of various parameters on two layers of soil, results were compared with the bearing capacity of the footing on one soil layer in various situations. The bearing capacity of the footing was then compared with previous experimental methods, and the results obtained were reliable.

Seismic bearing capacity of strip footing above an unsupported circular tunnel in undrained clay

By applying the lower bound theorem of limit analysis in conjunction with finite element, the bearing capacity of a strip footing located above an unlined long circular tunnel in undrained clay is computed with the inclusion of pseudo-static horizontal seismic body forces. The effects of varying the tunnel diameter and the embedment depth of tunnel below the ground level on the seismic bearing capacity of foundation are studied in detail. The design charts are provided for a wide range of pseudo-static earthquake forces. It is expected that the charts provided in this note will be quite helpful for the practicing engineers. Failure patterns are also studied in detail to understand the extent and the type of failure zone which may generate during the collapse.

Bearing capacity of strip footings on two-layered clay under combined loading

In this paper, a lower bound limit analysis in conjunction with finite elements and second-order cone programming (SOCP) is used to determine the bearing capacity of a rigid strip footing placed on two-layered clay subjected to inclined or eccentric loading. The footing is founded on the free surface of the soil mass with no surcharge applied. Two types of footing–soil interfaces are considered: (1) zero tensile capacity and (2) non-zero tensile capacity. The numerical results are presented in the form of failure envelopes in the loading plane, and the corresponding failure mechanisms are also presented. The size and shape of the failure envelopes are dependent on (1) the undrained shear strength ratio (cu1/cu2), where cu1 and cu2 are the undrained shear strength of the top and bottom clay, respectively, and (2) the normalized thickness D/B of the upper clay, where D is the thickness of the top clay layer and B is the width of the footing.