• Geotechnical Engineering
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• v.10 no.3
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• pp.5-16
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• 1994

This paper presents a new method to improve the bearing capacity of a square shallow foundation placed on a sand layer reinforced with geogrids which shows promise for further field work. The geogrid reinforcement will be necessary in the case of machine foundation, embankments for railroads, and foundations of structures in earthquake-prone areas. The ultimate bearing capacity (UBC) for the unreinforced sand and reinforced sand has been compared. Also, the effect of length, spacing, width of reinforcement on increasing the UBC have been evaluated. Based on the present model test results, it appears that significant improvement in the UBC of medium sand can be achieved by geogrid reinforcement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.923-932
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• 1994

The studies on the bearing capacity of shallow and deep foundations have been made in various fields and formulas for various failure mechanisms have been presented. But, for these models, the method of classification with foundation depth has been obscure and bearing capacity factors have not been uniformly applied. An experiment was performed, in plane strain conditions, with ground model made of carbon rods. The failure mechanism of foundation and ultimate bearing capacity with foundation depth were observed. Based on experimental results the classification between shallow and deep foundations by failure shape was tried. Various present failure mechanisms of foundation were verified through the experiment.

• Geomechanics and Engineering
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• v.11 no.6
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• pp.805-820
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• 2016

A fully coupled non-linear effective stress response finite difference (FD) model is built to survey the counter-intuitive recent findings on the reliance of pore water pressure ratio on foundation contact pressure. Two alternative design scenarios for a benchmark problem are explored and contrasted in the light of construction emission rates using the EFFC-DFI methodology. A strain-hardening effective stress plasticity model is adopted to simulate the dynamic loading. A combination of input motions, contact pressure, initial vertical total pressure and distance to foundation centreline are employed, as model variables, to further investigate the control of permanent and variable actions on the residual pore pressure ratio. The model is verified against the Ghosh and Madabhushi high acceleration field test database. The outputs of this work are aimed to improve the current computer-aided seismic foundation design that relies on ground's packing state and consistency. The results confirm that on seismic excitation of shallow foundations, the likelihood of effective stress loss is greater in deeper depths and across free field. For the benchmark problem, adopting a shallow foundation system instead of piled foundation benefitted in a 75% less emission rate, a marked proportion of which is owed to reduced materials and haulage carbon cost.

• Journal of the Korean GEO-environmental Society
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• v.17 no.12
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• pp.55-64
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• 2016

In this paper bearing capacity and safety margin of shallow foundation on weathered soil ground against shear failure by using current design method of allowable stress design (ASD), load resistance factor design (LRFD) based on reliability analysis and partial safety factor design (PSFD) in Eurocode were estimated and compared to each other. Results of the plate loading test used in construction and design were collected and analysis of probability statistics on soil parameters affecting the bearing capacity of shallow foundation was performed to quantify the uncertainty of them and to investigate the resistance bias factor and covalence of ultimate bearing capacity. For the typical sections of shallow foundation in domestic field as examples, reliability index was obtained by reliability analysis (FORM) and the sensitivity analysis on soil parameters of probability variables was performed to investigate the effect of probability variable on shear failure. From stability analysis for these sections by ASD, LRFD with the target reiability index corresponding to the safety factor used in ASD and PSDF, safety margins were estimated respectively and compared.

• Earthquakes and Structures
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• v.12 no.2
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• pp.165-175
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• 2017

This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full probabilistic analysis methods like MC commonly are very time consuming, the feasibility of simple approximate methods' application including First Order Second Moment (FOSM) method and ASCE41 proposed approach for the soil uncertainty considerations is investigated. By comparing the results of the approximate methods with the results obtained from MC, it's observed that the results of both FOSM and ASCE41 methods are in good agreement with the results of MC simulation technique and they show acceptable accuracy in predicting the response variability.

• Journal of the Korean Geotechnical Society
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• v.35 no.3
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• pp.17-24
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• 2019

The purpose of this study is to understand the characteristics of bearing capacity of shallow foundation on the grounds. We made a comparative study of existing bearing capacity theory, based on the three-dimensional finite element analysis with a variety of conditions such as ground condition, foundation scale and foundation shape. In the finite element analysis, the ultimate bearing capacity showed a gradual convergence in the form of exponential function or logarithm function according to the foundation scale. Although the shear strength increased, the bearing capacity tended not to increase but change linearly. In the results of comparative study of existing bearing capacity theory, bearing capacity ratio ($q_{u(FEA)}/q_{u(theory)}$) of pure sand has the outcome closest to those of the Terzaghi method. Pure clay turned out to be about 0.4~0.6 while normal soil was changed in a range of 0.3~1.3. As shear strength is increased, the results turned out to be less than 1.0. Bearing capacity ratio ($q_u/q_{u(1.0)}$), normalized at 1.0m bearing capacity, was about 35%, 15% and 5% of theoretical formula under the condition of ${\phi}=25^{\circ}$, $30^{\circ}$ and $35^{\circ}$ of pure sand; no scale effect was found with pure clay and the normal soil with lower soil strength level showed less than 10% of the theoretical formula of pure sand. Bearing capacity ratio of each case, in accordance with, the shear strength increase, was largely influenced by the internal friction angle. Shape factor of bearing capacity ratios classified by foundation shapes have different results according to the shapes; the shape factor of circular foundation is 1.50, square foundation is 1.30, rectangular and continuous foundations are 1.1~1.0.

• Proceedings of the Korean Geotechical Society Conference
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• 1996.10a
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• pp.179-186
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• 1996

• Journal of the Korean GEO-environmental Society
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• v.11 no.4
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• pp.51-59
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• 2010

This article is a case study for the example of the foundation design, in the project area of the silty sand layer that is spread shallowly with loose status, to make the site for a structure and build it up. The site is located on the dredged and reclaimed land in Gun-San and In-Cheon that is formed the silty sand layer with loose status range around 10 meters underground level, the solid ground for the lower pile is shown around 20 meters underground level. Therefore, this area has to be done by ground improvement when applying for the shallow method of foundation. Dynamic compaction method considering the conditions of the design loads in each zone has to be decided through comparative review on the method of foundations and pilot field test was conducted, and drilling investigation and plate bearing test were achieved as well. The analysis results of the tests prove that stability against bearing capacity was acquired by ground improvement effect.

• Journal of the Korean Geotechnical Society
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• v.34 no.1
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• pp.25-35
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• 2018

Geocentrifuge tests are performed to investigate the structure-soil-structure interaction of shallow foundations that have various sizes. The soil specimen is prepared by using the air-pluviation, and the dynamic responses of the foundation are monitored with separation distances between the two foundations and the embedment. During the centrifugal test, the measured ground acceleration shows a tendency to increase with the increase of the input seismic amplitude, and maximum acceleration is measured at the surface due to the ground amplification. As the separation distance between the two foundations decreases, the ratio of the response spectral acceleration (RRS) increases and the period at the peak RRS decreases due to the structure-soil-structure interaction (SSSI). The RRS of the two foundations tends to decrease when the foundations are buried in the ground at the same separation distance.

• Journal of the Korean Geosynthetics Society
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• v.18 no.3
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• pp.33-44
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• 2019

Clinker layer is a stratum structure distributed in volcanic area such as Jeju Island. The clinker layers were formed in between the repetitive action of eruption and solidification of lava flows. Since the clinker layer contains a large amount of voids accompanied by the lava gas ejection process, there is a possibility of inducing overall stability of the ground due to the low stiffness and strength of the clinker layer. Therefore, in this study, site investigation was carried out at both ends of the 00 bridge where the clinker layers exist. And, based on the ground survey results, the behavior of shallow foundations was analyzed numerically. In addition, the improved shallow foundation behavior in grouting substitution using the chemical injection method of the clinker layer was compared with the shallow foundation behavior in the ground, and the grouting substitution efficiency of each layer was analyzed. As a result, the bearing capacity, the replacement efficiency and elastic settlement were different according to the presence or absence of the sediment layer. This is because the sediment layer has a lower stiffness and density than the clinker layer.