Bearing Capacity Of Square Footings Research Articles

BEARING CAPACITY OF SHALLOW FOOTINGS RESTING ON DUNE SAND

As a result of the growth of economic, demographic and building activities in Iraq, that necessitates carrying out geotechnical investigations for the dune sand to study behavior of footings resting on these soils. To determine these properties and to assess the suitability of these materials for resting shallow foundation on it, an extensive laboratory testing program was carried out. Chemical tests were carried out to evaluate any possible effects of the mineralogical composition of the soil on behavior of foundation rested on dune sands.Collapse tests were also conducted to trace any collapse potential. Loading tests were carried out for optimum water content and different shapes of footing. Loading test recommends manufacturing of steel box and footing models with different shapes and dimensions. The results indicated that, Affek dune sand is predominantly fine sand with non-plastic fines.Because the content of sulphate (as SO3) is only 0.05%, and the alkalinity of dune sand, which reduces the corrosion potential, ordinary Portland cement can be used in concrete foundation construction in/on dune sands. The results of collapsing tests showed that Affek dune sand exhibit a slight to moderate potential depending on stress level. Due to Soaking by water, the reduction in bearing capacity of optimum state was about 45%. The bearing capacity of square footing was greater than those of the circular and rectangular footings.

Three-dimensional limit analysis with Lade–Duncan criterion

The paper describes the three-dimensional numerical implementation of the Lade–Duncan criterion in a finite-element limit analysis code. Validation is done using examples with a known solution. To conclude the proposed numerical tool is applied to the calculation of the ultimate bearing capacity of square footing.

Application of Machine Learning Techniques in Predicting the Bearing Capacity of E-shaped Footing on Layered Sand

The paper presents the prediction of bearing capacity equation of E-shaped footing subjected to a vertical concentric load and resting on layered sand using machine learning techniques and the data used in the analysis has been extracted from finite element modelling of the same footing. The input variables used in the developed neural network model were the bearing capacity of square footing, thickness ratio, friction angle ratio and the output were the bearing capacity of E-shaped footing on layered sand. Multiple layer perceptron (MLP) and multiple linear regression (MLR) prediction models were used for the determination of error metrics and the ultimate bearing capacity of E-shaped footing resting on layered sand. Finally, for the ANN model development, a model equation was developed with the assistance of weights and biases, based on the MLP and MLR model using open-source WEKA and Anaconda software respectively. Sensitivity analysis has been performed on the data sets which correlates the various input variables with the output variable of both the models. The coefficient of determination (R2) comes out to be 0.99 and 0.98 for the MLP and MLR models respectively indicating that both the models were able to predict the bearing capacity for the E shaped footing with acceptable accuracy.

Reliability of Shape Factors for Bearing Capacity of Square Footings on Spatially Varying Cohesive Soils

AbstractShape factors traditionally are used to relate the bearing capacity of square, rectangular, and/or circular footings to that of strip footings in geotechnical foundation designs, in order t...

Effect of 3D Geogrid and Glasgrid in the Bearing Capacity of Square Footing Over Soil Slope

Many civil engineering structures such as buildings, bridges, and road embankment etc. require the construction of foundations over soil slope. Reinforcement technique is a low-cost method of enhancing the load carrying capacity of such foundations. Over the past three decades, geosynthetics have been successfully used as a reinforcing material. In the present study, a series of small-scale model footing tests were conducted on the geosynthetics reinforced soil slope. A bi oriented 3D geogrid and glasgrid were used as a reinforcing material. The results obtained from laboratory model footing tests over a geosynthetics reinforced earth slope are analyzed and presented. Pressure settlement curves and improvement factor (IF) were studied by measuring the results of different settlement ratios. Various parameters like edge distance (D) and slope angle (β) were studied to check the effect of slope geometry. Some other parameters like optimum value of initial reinforcement depth (u), influence depth of reinforcement (d), and number of reinforcements (N) were also considered to check the effect of geosynthetic in the enhancement of load carrying capacity of footing over reinforced earth slope. Experimental results demonstrate that load carrying capacity of foundation resting over soil slope significantly improved by the placement of geosynthetics in the soil. On the basis of the experimental work, critical values of geosynthetic parameters for the optimum reinforcing effect are suggested.

Experimental bearing capacity of eccentrically loaded foundation near a slope

Abstract Based on the response of small-scale model square footing, the present paper shows the results of an experimental bearing capacity of eccentrically loaded square footing, near a slope sand bed. To reach this aim, a steel model square footing of (150 mm × 150 mm) and a varied sand relative density of 30%, 50% and 70% are used. The bearing capacity-settlement relationship of footing located at the edge of a slope and the effect of various parameters such as eccentricity (e) and dimensions report (b/B) were studied. Test results indicate that ultimate bearing capacity decreases with increasing load eccentricity to the core boundary of footing and that as far as the footing is distant from the crest, the bearing capacity increases. Furthermore, the results also prove that there is a clear proportional relation between relative densities –bearing capacity. The model test provides qualitative information on parameters influencing the bearing capacity of square footing. These tests can be used to check the bearing capacity estimated by the conventional methods.

Three-dimensional lower bound finite element limit analysis of Hoek-Brown material using semidefinite programming

A reliable and accurate stability analysis in Hoek-Brown rock masses under fully three-dimensional geometries requires an efficient and powerful computational method. This paper presents a computational implementation of a three-dimensional lower bound finite element limit analysis using semidefinite programming for Hoek-Brown rock masses. Its computational performance is investigated extensively through a variety of boundary value problems in rock mechanics, namely triaxial compression, bearing capacity and cavity contraction. New lower bound solutions are numerically derived, including bearing capacity of square footings, uniaxial compression of cube and cylindrical rock specimens with fully rough platens and tension test on double notched rock specimens.

Finite Element Investigation of the Bearing Capacity of Square Footings Resting on Sloping Ground

The ultimate bearing capacity of foundation placed on a slope is significantly affected by its vicinity to the slope face, which offers substantially lesser passive resistance as compared to a footing resting on a semi-infinite medium. Conventional bearing capacity theories fail to address the behavior of such foundations. Few existing theories predict the bearing capacity of foundations on slopes considering stress-based failure approach. However, deformation along the slope plays a major role in governing the failure of such foundations, thus requiring a coupled stress-deformation based failure analysis. With the aid of 3-D finite element modelling, employing coupled stress-deformation analysis, this study addresses the failure mechanism and the bearing capacity (q u ) of a square footing located on a dry cohesionless slope. The effect of various parameters, namely the angle of internal friction of soil, setback distance, slope inclination, footing width and the depth of embedment of the footing, have been investigated. Variations parameters are found to noticeably alter the bearing capacity estimate and the observed failure mechanism. A critical setback distance is obtained [(b/B)critical = 3] beyond which the failure mechanism resembles the same obtained for a footing resting on horizontal ground. The unit weight and modulus of elasticity of the soil material is found to have negligible effect on the bearing capacity.

The bearing capacity of square footings on a sand layer overlying clay

The ultimate bearing capacity and failure mechanism of square footings resting on a sand layer over clay soil have been investigated numerically by performing a series of three-dimensional non-linear finite element analyses. The parameters investigated are the thickness of upper sand layer, strength of sand, undrained shear strength of lower clay and surcharge effect. The results obtained from finite element analyses were compared with those from previous design methods based on limit equilibrium approach. The results proved that the parameters investigated had considerable effect on the ultimate bearing capacity and failure mechanism occurring. It was also shown that the thickness of upper sand layer, the undrained shear strength of lower clay and the strength of sand are the most important parameters affecting the type of failure will occur. The value of the ultimate bearing capacity could be significantly different depending on the limit equilibrium method used.

Effect of reinforcement form on the bearing capacity of square footings on sand

This paper presents the results of laboratory model loading tests and numerical studies carried out on square footings supported on geosynthetic reinforced sand beds. The relative performance of different forms of geosynthetic reinforcement (i.e. geocell, planar layers and randomly distributed mesh elements) in foundation beds is compared; using same quantity of reinforcement in each test. A biaxial geogrid and a geonet are used for reinforcing the sand beds. Geonet is used in two forms of reinforcement, viz. planar layers and geocell, while the biaxial geogrid was used in three forms of reinforcement, viz. planar layers, geocell and randomly distributed mesh elements. Laboratory load tests on unreinforced and reinforced footings are simulated in a numerical model and the results are analyzed to understand the distribution of displacements and stresses below the footing better. Both the experimental and numerical studies demonstrated that the geocell is the most advantageous form of soil reinforcement technique of those investigated, provided there is no rupture of the material during loading. Geogrid used in the form of randomly distributed mesh elements is found to be inferior to the other two forms. Some significant observations on the difference in reinforcement mechanism for different forms of reinforcement are presented in this paper.

Performance of square footing with structural skirt resting on sand

The paper presents the performance of a square footing with a structural skirt resting on sand and subjected to a vertical load through an experimental study. A series of tests were conducted in a model test tank to evaluate the performance in terms of improvement in bearing capacity and reduction in settlement of a square footing with and without a structural skirt. The results of the study reveal that this type of reinforcement increases the bearing capacity, reduces the settlement and modifies the load settlement behaviour of the footing. The various factors influencing the bearing capacity improvements and settlement reduction using a structural skirt are identified. Skirt factors are proposed which can be introduced into the general ultimate bearing capacity equation for a square footing resting on sand. The predictions made through the modified equation are in reasonable agreement with the experimental results. The bearing capacity of square footing is increased in the range of 11.2 to 70%. The improvement in bearing capacity decreases with the increase in base roughness of the footing. Further, an equation for a settlement reduction factor is proposed which can be used to calculate the settlement of the square footing with structural skirt resting on sand. The settlement reduction factor (SRF, defined as the ratio of settlement of footing with structural skirt to the settlement of footing without structural skirt at a given load) was in the range 0.11 to 1.0 depending on applied load and skirt depth ratio with the use of a structural skirt. The results further reveal that for a given depth of the skirt, the settlement reduction factor decreases with the increase in applied load. The improvement in the bearing capacity and reduction in settlement of a square footing with a structural skirt resting on sand are dependent on the geometrical and structural properties of the skirt, footing, sand characteristics and interface conditions of the sand–skirt–footing system.

Bearing capacity of square footing on reinforced pond ash

This paper presents the ultimate bearing capacity of square footing on pond ash reinforced with a single layer of geotextile reinforcement. The effect of different vital bearing-capacity parameters on the ultimate bearing capacity (qru) of square footing on reinforced pond ash has been studied. Parameters considered include depth of the reinforcement layer below the footing (u) and friction ratio (f ▪ ψ/φd)—that is, the ratio of the pond ash reinforcement interface friction angle (ψ) to the direct shear friction angle of pond ash (φd). The value of u/B (B being the width of footing) corresponding to the maximum ultimate bearing capacity is considered as optimum u/B in the current study. In the present investigation the value of optimum u/B ratio was found to increase with increase in friction ratio (f ). With increase in friction ratio (f ), bearing capacity ratio (BCRu= (qru/qu) where qu is the ultimate bearing capacity of square footing, of the same size as that for qru, on unreinforced pond ash) increases. In the present investigation BCRu increases from 1·1180 to 1·4158 with a corresponding increase in friction ratio (f ) of 0·7073 to 0·9230.

Experimental Study of Bearing Capacity of Granular Soils, Reinforced with Innovative Grid-Anchor System

The pull-out resistance of reinforcing elements is one of the most significant factors in increasing the bearing capacity of geosynthetic reinforced soils. In this research a new reinforcing element that includes elements (anchors) attached to ordinary geogrid for increasing the pull-out resistance of reinforcements is introduced. Reinforcement therefore consists of geogrid and anchors with cubic elements that attached to the geogrid, named (by the authors) Grid-Anchor. A total of 45 load tests were performed to investigate the bearing capacity of square footing on sand reinforced with this system. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, effect of relative density, low strain stiffness and stiffness after local shear were investigated. Laboratory tests showed that when a single layer of reinforcement is used there is an optimum reinforcement embedment depth for which the bearing capacity is the greatest. There also appeared to be an optimum vertical spacing of reinforcing layers for multi-layer reinforced sand. The bearing capacity was also found to increase with increasing number of reinforcement layer, if the reinforcement were placed within a range of effective depth. The effect of soil density also is investigated. Finally the results were compared with the bearing capacity of footings on non-reinforced sand and sand reinforced with ordinary geogrid and the advantages of the Grid-Anchor were highlighted. Test results indicated that the use of Grid-Anchor to reinforce the sand increased the ultimate bearing capacity of shallow square footing by a factor of 3.0 and 1.8 times compared to that for un-reinforced soil and soil reinforced with ordinary geogrid, respectively.

Bearing capacity of square footing on pond ash reinforced with jute-geotextile

At present an enormous amount of pond ash is being produced by thermal power plants throughout the world. Storage of pond ash requires vast land area and disposal of ash becomes problematic and also it creates environmental hazards. To mitigate these problems, pond ash has been used in the low-lying areas as structural fills for developing residential and industrial sites. To enhance the bearing capacity of pond ash, it may be reinforced with jute-geotextile, a textile made from jute (natural fibre) for the purpose. In the present study an attempt has been made to study the bearing capacity of square footing on pond ash reinforced with jute-geotextile. The effects of different parameters like number of layers ( N) of reinforcement, the depth of the upper most layer of reinforcement from the base of the footing ( u), friction ratio ( f), i.e. the ratio of the pond ash jute-geotextile interface friction angle ( ψ) to the direct shear friction angle of pond ash ( φ d) and jute-geotextile sheet length ( L s) on bearing capacity of square footing ( q rs) at any settlement resting on pond ash reinforced with jute-geotextile are discussed. A non-linear power model has been developed to estimate q rs based on 1399 experimental data.