The settlement and bearing capacity of very large foundations on strong soils: 1996 R.M. Hardy keynote address

1998 ◽  
Vol 35 (1) ◽  
pp. 131-145 ◽  
Author(s):  
Jack I Clark
Keyword(s):  
Bearing Capacity ◽  
Data Base ◽  
Tall Buildings ◽  
Friction Angle ◽  
Geologic History ◽  
Cohesionless Soils ◽  
In Situ Tests ◽  
Angle Of Internal Friction ◽  
Undisturbed Samples ◽  
Order Of Magnitude

Strong soils are not typically problem soils, and hence their behaviour has not been extensively studied. Strong soils are best defined on the basis of their geologic history, but for this paper they can be roughly defined as cohesive soils with an N value of about 15 or over and cohesionless soils with N values over 30. Settlement of tall buildings on strong soils has always been of interest. The means of estimating settlement of the large foundations or pile foundations associated with these structures varies but is generally understood to be predominantly elastic. Although predictions of settlement based on laboratory tests or in situ tests may vary as much as an order of magnitude, there now exists a reasonable data base which suggests that large buildings will settle similar amounts regardless of the size or bearing pressure of the foundations or, for that matter, the type of foundations. No data base exists for quantifying the maximum bearing pressure that will be tolerated by large foundations without failure. The angle of internal friction is known to be critical and to decrease with increasing pressure. It is difficult to measure the undisturbed strength of strong soils, since undisturbed samples are very difficult to secure. Centrifuge model tests of large foundations of different shapes confirm that the bearing capacity factor N gamma decreases with increased size of footing, but the decrease of N gamma may not be accounted for entirely by the friction angle change with pressure. Selection of a friction angle to determine the peak capacity of very large foundations must be done very carefully and with a great deal of judgement, since it cannot be accurately measured.Key words: settlement, bearing capacity, foundation behaviour.

scholarly journals Bearing Capacity of the Working Platform with Kinematic Method

2015 ◽  
Vol 37 (1) ◽  
pp. 3-8
Author(s):  
Katarzyna Białek ◽  
Lech Bałachowski
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Soft Soil ◽  
Failure Mechanisms ◽  
Cohesionless Soils ◽  
Angle Of Internal Friction ◽  
Kinematic Method ◽  
Margin Of Safety ◽  
Effective Angle ◽  
Different Thickness

Abstract Bearing capacity of the working platform for heavy tracks was analysed using Distinct Layout Optimization (DLO) method. The platform layer constructed from cohesionless soils is resting on weak cohesive subgrade. Different thickness of the platform, its effective angle of internal friction and undrained shear strength of the soft soil were taken into consideration. Kinematic method permits different failure mechanisms to be analyzed. Margin of safety for a given load and subsoil conditions was determined using two approaches: increasing the load or decreasing the shear strength up to failure. The results were compared with solution proposed in BRE recommendations.

scholarly journals Bearing capacity and settlement prediction of multi-edge skirted footings resting on sand

2020 ◽  
Vol 40 (3) ◽  
pp. 9-21
Author(s):  
Tammineni Gnananandarao ◽  
Vishwas Nandkishor Khatri ◽  
Rakesh Kumar Dutta
Keyword(s):  
Regression Analysis ◽  
Bearing Capacity ◽  
Input Parameter ◽  
Friction Angle ◽  
Reduction Factor ◽  
Small Scale ◽  
Ann Model ◽  
Angle Of Internal Friction ◽  
Ann Models ◽  
The Difference

This paper presents the application of artificial neural networks (ANN) and multivariable regression analysis (MRA) to predict the bearing capacity and the settlement of multi-edge skirted footings on sand. Respectively, these parameters are defined in terms of the bearing capacity ratio (BCR) of skirted to unskirted footing and the settlement reduction factor (SRF), the ratio of the difference in settlement of unskirted and skirted footing to the settlement of unskirted footing at a given pressure. The model equations for the prediction of the BCR and the SRF of the regular shaped footing were first developed using the available data collected from the literature. These equations were later modified to predict the BCR and the SRF of the multi-edge skirted footing, for which the data were generated by conducting a small scale laboratory test. The input parameters chosen to develop ANN models were the angle of internal friction (ϕ) and skirt depth (Ds) to the width of the footing (B) ratio for the prediction of the BCR; as for the SRF one additional input parameter was considered: normal stress (𝛔). The architecture for the developed ANN models was 2-2-1 and 3-2-1 for the BCR and the SRF, respectively. The R2 for the multi-edge skirted footings was in the range of 0,940-0,977 for the ANN model and 0,827-0,934 for the regression analysis. Similarly, the R2 for the SRF prediction might have been 0,913-0,985 for the ANN model and 0,739-0,932 for the regression analysis. It was revealed that the predicted BCR and SRF for the multi-edge skirted footings with the use of ANN is superior to MRA. Furthermore, the results of the sensitivity analysis indicate that both the BCR and the SRF of the multi-edge skirted footings are mostly affected by skirt depth, followed by the friction angle of the sand.

Assessment of the range of variation of Nγ from 60 estimation methods for footings on sand

2013 ◽  
Vol 50 (7) ◽  
pp. 793-800 ◽  
Author(s):  
Edgar Giovanny Diaz-Segura
Keyword(s):  
Friction Angle ◽  
Standard Penetration Test ◽  
Estimation Methods ◽  
Penetration Test ◽  
In Situ Tests ◽  
Vertical Loading ◽  
Simplified Method ◽  
Bearing Capacity Factor ◽  
Range Of Variation

The range of variation of the bearing capacity factor, Nγ, was assessed using 60 estimation methods for rough footings on sand subjected to static vertical loading. The influence on the Nγ values of the use of correlations for the estimation of the friction angle, [Formula: see text], derived from in situ tests was also assessed. The analysis shows a marked dependency on the methods used to determine Nγ, showing differences for the same [Formula: see text] values of up to 267% between estimated values. Uncertainty in the estimation of [Formula: see text], due to the use of correlations with in situ tests, leads to a range of variation for Nγ higher than that seen using the 60 estimation methods. Finally, given the regular use of the in situ standard penetration test (SPT) on sands, and based on a series of analyses using finite elements, a simplified method in terms of the SPT N-values is proposed for estimation of Nγ in footings on sands.

In situ estimation of the coefficient of consolidation in clays

1990 ◽  
Vol 27 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Mohammed G. Kabir ◽  
Alan J. Lutenegger
Keyword(s):  
Key Words ◽  
Pore Pressure ◽  
Reference Values ◽  
Time Factors ◽  
In Situ Tests ◽  
Coefficient Of Consolidation ◽  
Oedometer Test ◽  
Undisturbed Samples ◽  
Oedometer Tests

An investigation was conducted to demonstrate the applicability of cylindrical piezocone and flat piezoblade tests for providing reliable estimates of the coefficient of consolidation in clays. Coefficients of consolidation were calculated from piezocone dissipation tests for different degrees of consolidation using theoretical time factors to provide a comparison with laboratory oedometer tests. Three techniques were developed to calculate the coefficient of consolidation from piezoblade dissipation tests. Results from in situ pore pressure dissipation tests were compared with laboratory oedometer tests performed on undisturbed samples oriented in both the vertical and horizontal directions, to provide reference values of cv and ch. The results of investigations conducted at several clay sites are presented. Key words: in situ tests, piezocone, piezoblade, coefficient of consolidation, oedometer test, clays.

Seismic uplift capacity of inclined strip anchors

2005 ◽  
Vol 42 (1) ◽  
pp. 263-271 ◽  
Author(s):  
Deepankar Choudhury ◽  
K S Subba Rao
Keyword(s):  
Limit Equilibrium ◽  
Ground Surface ◽  
Failure Surface ◽  
Friction Angle ◽  
Uplift Capacity ◽  
Principle Of Superposition ◽  
Seismic Acceleration ◽  
Acceleration Coefficient ◽  
Angle Of Internal Friction ◽  
Seismic Forces

Uplift capacities of inclined strip anchors in soil with a horizontal ground surface are obtained under seismic conditions. Limit equilibrium approaches with a logarithm-spiral failure surface and pseudostatic seismic forces are adopted in the analysis. The results are presented in the form of seismic uplift capacity factors as functions of anchor inclination, embedment ratio, angle of internal friction of the soil, and horizontal and vertical seismic acceleration coefficients. The uplift capacity factors are worked out separately for cohesion, surcharge, and density components. Use of the principle of superposition for calculating anchor uplift capacity is validated. The vertical seismic acceleration coefficient always reduces the uplift capacity, whereas the horizontal seismic acceleration coefficient reduces the uplift capacity in most cases. The roles of anchor embedment ratio, soil friction angle, and anchor inclination in determination of the seismic uplift capacity are also discussed. Comparisons of the proposed method with available theories in the seismic case are also presented. The present study gives the minimum seismic uplift capacity factors compared with the existing theory.Key words: seismic uplift capacity factors, inclined strip anchors, limit equilibrium, pseudostatic, c–ϕ soil.

scholarly journals Improvement ratio and behavior of bearing capacity factors for strip skirt footing model resting on sand of different grain size distribution

2018 ◽  
Vol 162 ◽  
pp. 01026
Author(s):  
Mahmood Rashid Mahmood
Keyword(s):  
Grain Size ◽  
Bearing Capacity ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Coarse Sand ◽  
Linear Increase ◽  
Angle Of Internal Friction ◽  
Theoretical Approaches ◽  
Different Grain Size ◽  
Improvement Ratio

Plain strain model tests were performed on beds of sands with different particle size distribution (Coarse, Medium and Fine) prepared at loose state (Relative density Dr. of 30%). A strip footing model with skirt was placed on the bed of sand and loaded vertically up to failure at different ratios of skirt depth to width D/B of (0.5, 1.0, 1.5, 2, and 3). The applied stress increments and the corresponding settlements were measured. The improvement ratio due to different skirt depth and the behavior of bearing capacity parameters Nγ and Nq at each depth were evaluated and compared with some theoretical approaches. The test results revealed that the improvement ratio increased linearly up to D/B of 1.5 then reduced. Two factors were introduce into the general bearing capacity equation where used to evaluate bearing capacity of skirt footing, there values are about 1.6 for skirt ratio ranged between 0.5 to 1.5, and 1.25 for skirt ratio more than 1.5. Also, it is found that the Nγ parameter for D/B=0 were very close to Vesic proposal for fine and medium grain size distribution, while it’s close to Biarez proposal for coarse sand. The behavior of Nq parameter with different skirt ratio shows slight increase up to D/B of 1.5 then decrease with increasing D/B ratio for different grain size distribution. While the behavior of theoretical Nq parameter (depending on angle of internal friction values) shows a linear increase with skirt ratio for different grain size distribution.

scholarly journals Probabilistic Bearing Capacity of a Pavement Resting on Fibre Reinforced Embankment Considering Soil Spatial Variability

2021 ◽  
Vol 7 ◽  
Author(s):  
Kouseya Choudhuri ◽  
Debarghya Chakraborty
Keyword(s):  
Spatial Variability ◽  
Soil Properties ◽  
Bearing Capacity ◽  
Coefficient Of Variation ◽  
Friction Angle ◽  
Horizontal Scale ◽  
Vertical Scale ◽  
Scale Of Fluctuation ◽  
The Mean ◽  
The Finite Difference Method

This paper intends to examine the influence of spatial variability of soil properties on the probabilistic bearing capacity of a pavement located on the crest of a fibre reinforced embankment. An anisotropic random field, in combination with the finite difference method, is used to carry out the probabilistic analyses. The cohesion and internal friction angle of the soil are assumed to be lognormally distributed. The Monte Carlo simulations are carried out to obtain the mean and coefficient of variation of the pavement bearing capacity. The mean bearing capacity of the pavement is found to decrease with the increase in horizontal scale of fluctuation for a constant vertical scale of fluctuation; whereas, the coefficient of variation of the bearing capacity increases with the increase in horizontal scale of fluctuation. However, both the mean and coefficient of variation of bearing capacity of the pavement are observed to be increasing with the increase in vertical scale of fluctuation for a constant horizontal scale of fluctuation. Apart from the different scales of fluctuation, the effects of out of the plane length of the embankment and randomness in soil properties on the probabilistic bearing capacity are also investigated in the present study.

scholarly journals Geotechnical Investigations of an Earth-Filled Site for Construction of a Building

2020 ◽  
Vol 18 (02) ◽  
pp. 71-74
Author(s):  
Riaz Bhanbhro ◽  
Zafar Ali Siyal ◽  
Bashir Ahmed Memon ◽  
Shahnawaz Zardari ◽  
Amjad Hussain Bhutto ◽  
...  
Keyword(s):  
Friction Angle ◽  
Complex Materials ◽  
Strength Parameters ◽  
Strain Behavior ◽  
The Earth ◽  
Undisturbed Samples ◽  
Geotechnical Investigations ◽  
Allowable Bearing Capacity ◽  
Allowable Load ◽  
Silty Soils

There is a growing need of construction around the globe. This need tends to provide newer opportunities for construction of buildings over reclaimed lands or earth filled areas. Mostly, the earth is filled with soils as it is an easily available material. Soil is a complex materials, and its properties can vary due to several reasons. If not understood properly, it can damage undisturbed samples collected from earth-filled soils. The basic properties of soils, the stress-strain behavior and strength parameters are presented and discussed. Results show that soil exhibits strain hardening and normally consolidated behavior in direct shear and oedometer test respectively. It is observed that the compression index values are in the range of 0.157 to 0.182 which indicates that the material is silty soils with low plasticity. The allowable bearing capacity in our study was 305 kPa and allowable load on footing was 987 kN. The strength parameters, i.e., friction angle and cohesion are 37 degree and 2 kPa respectively.

scholarly journals Bearing Capacity of Ring Foundations on Sand Overlying Clay

2020 ◽  
Vol 10 (13) ◽  
pp. 4675
Author(s):  
Chaowei Yang ◽  
Zhiren Zhu ◽  
Yao Xiao
Keyword(s):  
Bearing Capacity ◽  
Friction Angle ◽  
Failure Criteria ◽  
Unit Weight ◽  
Sand Layer ◽  
Collapse Mechanisms ◽  
Internal Radius ◽  
Vertical Bearing ◽  
Vertical Bearing Capacity ◽  
Ring Foundations

The vertical bearing capacity of rough ring foundations resting on a sand layer overlying clay soil is computed in this study by using finite element limit analysis (FELA). The sands and clays are assumed as elastoplastic models, obeying Mohr–Coulomb and Tresca failure criteria, respectively. Based on the FELA results, design charts are provided for evaluating the ultimate bearing capacity of ring foundations, which is related to the undrained shear strength of the clay, the thickness, the internal friction angle, the unit weight of the sand layer, and the ratio of the internal radius to the external radius of the footing. A certain thickness, beyond which the clay layer has a negligible effect on the bearing capacity, is determined. The collapse mechanisms are also examined and discussed.

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