Simulations of Bearing Capacity of Foundation on Unsaturated Granular Soils

2011 ◽  
Vol 52-54 ◽  
pp. 1400-1405 ◽  
Author(s):  
Anuchit Uchaipichat ◽  
Ekachai Man-Koksung
Keyword(s):  
Bearing Capacity ◽  
Limit Equilibrium ◽  
Ultimate Bearing Capacity ◽  
Shallow Foundation ◽  
Granular Soils ◽  
Equilibrium Concept ◽  
Common Structure ◽  
The Earth ◽  
Dry Conditions ◽  
Unsaturated Granular Soils

Typically a shallow foundation is chosen to support several types of common structure. Several equations for the ultimate bearing capacity of shallow foundation have been proposed with assumption of fully saturated or completely dry conditions. In fact, almost 40 percent of natural soils on the earth surface are in an unsaturated state. Therefore, the ultimate bearing capacity of shallow strip foundation on unsaturated granular soils is developed in this paper using limit equilibrium concept. The simulations from the developed equation for a laboratory-compacted-sand are performed. The results are carefully presented and discussed.

Bearing Capacity Characteristic of Unsaturated Granular Soils

2011 ◽  
Vol 261-263 ◽  
pp. 989-993 ◽  
Author(s):  
Anuchit Uchaipichat ◽  
Ekachai Man Koksung
Keyword(s):  
Bearing Capacity ◽  
Matric Suction ◽  
Ultimate Bearing Capacity ◽  
Experimental Program ◽  
Granular Soils ◽  
Test Results ◽  
High Level ◽  
Unsaturated Granular Soils ◽  
Capacity Characteristic

An experimental program of laboratory bearing tests was performed to characterize the bearing capacity of foundation on unsaturated granular soils. All tests were performed by pushing a circular rod on the surface of compacted sand specimens with different values of matric suction until failure. The test results show an increase in ultimate bearing capacity with increasing matric suction at low suction value but a decrease in that at high level of suction. The comparisons between the test results and simulations using the expressions proposed in this paper are presented and discussed. Good agreements are achieved for all testing values of suction.

scholarly journals A NEW DESIGN EQUATION FOR PREDICTION OF ULTIMATE BEARING CAPACITY OF SHALLOW FOUNDATION ON GRANULAR SOILS

2014 ◽  
Vol 19 (Supplement_1) ◽  
pp. S78-S90 ◽  
Author(s):  
Ehsan Sadrossadat ◽  
Fazlollah Soltani ◽  
Seyyed Mohammad Mousavi ◽  
Seyed Morteza Marandi ◽  
Amir H. Alavi
Keyword(s):  
Bearing Capacity ◽  
Numerical Models ◽  
Ultimate Bearing Capacity ◽  
Prediction Performance ◽  
Shallow Foundations ◽  
Shallow Foundation ◽  
Granular Soils ◽  
Good Prediction ◽  
Design Equation ◽  
Statistical Measures

A major concern in design of structures is to provide precise estimations of ultimate bearing capacity of soil beneath their foundations. Direct determination of the bearing capacity of foundations requires performing expensive and time consuming laboratory tests. To cope with this issue, several numerical models have been presented by researchers. This paper presents the development of a new design equation for the prediction of the ultimate bearing capacity of shallow foundations on granular soils using linear genetic programming (LGP) methodology. The ultimate bearing capacity is formulated in terms of width of footing, footing geometry, depth of footing, unit weight of sand, and angle of shearing resistance. The LGP-based design equation is established using the results of several load tests on real sized foundations presented in the literature. Validity of the model is verified using a part of laboratory data that are not involved in the calibration process. The statistical measures of coefficient of determination, root mean squared error and mean absolute error are used to evaluate the performance of the model. Sensitivity and parametric analyses are conducted and discussed. The proposed model accurately characterizes the ultimate bearing capacity resulting in a very good prediction performance. The LGP model reaches a better prediction performance than the well-known prediction equations for the bearing capacity of shallow foundations.

scholarly journals Determination of bearing capacity of shallow foundations without using superposition approximation

2003 ◽  
Vol 40 (2) ◽  
pp. 450-459 ◽  
Author(s):  
D Y Zhu ◽  
C F Lee ◽  
K T Law
Keyword(s):  
Bearing Capacity ◽  
Field Method ◽  
Ultimate Bearing Capacity ◽  
Shallow Foundation ◽  
Closed Form Expression ◽  
Safe Side ◽  
Superposition Approximation ◽  
Bearing Capacity Factor ◽  
Rigorous Procedure

The Terzaghi superposition assumption has been widely used to determine the bearing capacity of shallow footings. Although this assumption always errs on the safe side, a rigorous procedure to calculate the bearing capacity is still of engineering value. This paper presents such a procedure that is free from errors as a result of the superposition assumption. It demonstrates that the ultimate bearing capacity can be precisely expressed by the Terzaghi equation, except that the bearing capacity factor Nγ is dependent upon the surcharge ratio. A recently developed numerical method, i.e., the critical slip field method, is used to calculate the modification coefficient for modifying Nγ. It is found that this modification coefficient increases with the surcharge ratio at small values of surcharge ratio and then remains constant for large values of surcharge ratio. However, the errors invoked by the superposition assumption do not exceed 10%. On the basis of numerical calculations, a simple closed-form expression of the modification coefficient is proposed that yields the theoretically rigorous ultimate bearing capacity. In the later part of the paper, errors in bearing capacity calculations owing to the use of conventional procedures are analyzed. It is concluded that the continued use of conventional procedures is justified, but the inherent errors should not be neglected in assessing the performance of shallow foundations.Key words: shallow foundation, strip footing, ultimate bearing capacity, critical slip field.

scholarly journals Influence of Natural Cavities on the Design of Shallow Foundations

2020 ◽  
Vol 10 (3) ◽  
pp. 1119
Author(s):  
Jesús Luis Benito Olmeda ◽  
Javier Moreno Robles ◽  
Eugenio Sanz Pérez ◽  
Claudio Olalla Marañón
Keyword(s):  
Rock Mass ◽  
Bearing Capacity ◽  
Ultimate Bearing Capacity ◽  
Shallow Foundation ◽  
Rock Masses ◽  
Volcanic Origin ◽  
Rock Types ◽  
Geometric Configurations ◽  
Relative Eccentricity ◽  
Decisive Parameter

When inner cavities of significant dimensions exist in natural rocks, problems arise when a shallow foundation for a building, bridge or other structure is builtonthem. Thus, taking one of the most representative cavity geometries in nature, the ellipsoidal horizontal shape, the main objective of this study is to obtain the ultimate bearing capacity of the foundation with cavities of different sizes and positions, on rock masses with different strengths and deformation characteristics. The study focuses on natural rocks of karst origin (in limestones, dolomites or gypsums) and of volcanic origin. The ultimate bearing capacity is determined relative to a situation without the existence of the cavity for different cavern positions and sizes, rock types (mi), strengths (UCS), and states (GSI) of the rock mass. The results showed that the most decisive parameter is the relative eccentricity. The influence of the rock type (Hoek’s parameter mi) is, for practical purposes, negligible (lower than 10%). The strength and condition of the rock mass (parameters UCS and GSI) have relatively little influence on the results obtained. This study aims to provide a simple design criteria for universal use, with different geometric configurations and qualities of rock masses that can be used directly without the need for sophisticated calculations by the designer.

Ultimate bearing capacity of shallow foundations on sand with geogrid reinforcement

1993 ◽  
Vol 30 (3) ◽  
pp. 545-549 ◽  
Author(s):  
M.T. Omar ◽  
B.M. Das ◽  
V.K. Puri ◽  
S.C. Yen
Keyword(s):  
Bearing Capacity ◽  
Key Words ◽  
Model Test ◽  
Ultimate Bearing Capacity ◽  
Shallow Foundations ◽  
Shallow Foundation ◽  
Laboratory Model ◽  
Critical Depth ◽  
Test Results ◽  
Laboratory Model Test

Laboratory model test results for the ultimate bearing capacity of strip and square foundations supported by sand reinforced with geogrid layers have been presented. Based on the model test results, the critical depth of reinforcement and the dimensions of the geogrid layers for mobilizing the maximum bearing-capacity ratio have been determined and compared. Key words : bearing capacity, geogrid, model test, reinforced sand, shallow foundation.

Experimental and large-scale field tests of grid-anchor system performance in increasing the ultimate bearing capacity of granular soils

2016 ◽  
Vol 53 (7) ◽  
pp. 1047-1058 ◽  
Author(s):  
M. Mosallanezhad ◽  
N. Hataf ◽  
S.H. Sadat Taghavi
Keyword(s):  
Bearing Capacity ◽  
Large Scale ◽  
Field Tests ◽  
Experimental Tests ◽  
Ultimate Bearing Capacity ◽  
Soil Reinforcement ◽  
Granular Soils ◽  
Anchor System ◽  
Scale Field ◽  
Large Scale Field

Soil reinforcement by means of geogrid is an effective method of increasing the ultimate bearing capacity (UBC) of granular soils. In this study a new system, created by adding cubic anchors to ordinary geogrids, is introduced to increase the UBC of granular soils. This system is called “grid-anchor” (G-A). To analyse the performance of the G-A system in increasing the UBC of granular soils, 45 experimental tests and 9 field tests were performed, the results of which show that the G-A system is 1.8 times more capable than ordinary geogrids in increasing the UBC in square foundations. Furthermore, the failure of soil reinforced by the ordinary geogrid takes place at a settlement of 9% of the foundation width, while the same value for the G-A system is almost 13%.

Analysis of Earth Pressure for Retaining Wall and Ultimate Bearing Capacity for Shallow Foundation by Variational Method

2004 ◽  
Vol 20 (1) ◽  
pp. 43-56 ◽  
Author(s):  
Lai-Yun Wu ◽  
Yi-Feng Tsai
Keyword(s):  
Variational Method ◽  
Bearing Capacity ◽  
Governing Equation ◽  
Virtual Work ◽  
Retaining Wall ◽  
Earth Pressure ◽  
Ultimate Bearing Capacity ◽  
Shallow Foundation ◽  
Rupture Surface ◽  
Transversality Conditions

AbstractApplying the principle of virtual work, the slice element method, and the variational method proposed in this paper, one can derive the governing equation and transversality conditions for the rupture surface of a sliding mass of retaining wall and shallow foundation under several external conditions. The governing equation, transversality, and boundary conditions can be solved by the finite difference method (FDM) proposed in this paper, so that the rupture surface and its associated earth pressure acting on the retaining wall or the ultimate bearing capacity acting on the foundation can be determined effectively. By comparison of our results with those of some well known earth pressure and bearing capacity estimating methods, it can be concluded that determining the earth pressure on a retaining wall or the ultimate bearing capacity of a shallow foundation by using the variational method and FDM proposed in this paper, a logical and reasonable result can be obtained without the necessity of guessing the rupture surface.

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