• Journal of the Korean Geotechnical Society
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• v.32 no.7
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• pp.35-45
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• 2016

Estimation of vertical bearing capacity is critical in the design of bucket foundation used to support offshore structure. Empirical formula and closed form solutions for bucket foundations in uniform sand or clay profiles have been extensively studied. However, the vertical bearing capacity of bucket foundations in alternating layers of sand overlying clay is not well defined. We performed a series of two-dimensional axisymmetric finite element analyses on bucket foundations in sand overlying clay soil, using elasto-plastic soil model. The load transfer mechanism is investigated for various conditions. Performing the parametric study for the friction angles, undrained shear strengths, thickness of sand layer, and aspect ratios of foundation, we present the predictive charts for determining the vertical bearing capacities of bucket foundations in sand overlying clay layer. In addition, after comparing with the finite element analysis results, it is found that linear interpolation between the design charts give acceptable values in these ranges of parameters.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.131-139
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• 2004

When calculating bearing capacity and settlement of actual foundation from plate test result fur design and construction of shallow foundation, scale effect should be considered. But, adequate guide and test result of scale effect were not prepared yet in Korea. So, to analyze the relations of bearing capacity and settlement as the difference of loading plate sizes, model test and field loading test were performed with different loading plate on weathered-granite layer. Model tests were conducted with water content, compaction number, saturated unit weight and plate size(Dl5, 25cm) in soil-box$(2,000\times 2,000\times 1,000mm)$ formed soil layer. Field loading tests were carried out with diameters of loading plate$(D15, 25, 30, 40, 75\times 75, 140\times 210cm)$ on the same soil condition. Finally, we presented the prediction formula of bearing and settlement for computating scale offset in design of shallow foundation through result analysis of load test and numerical simulation on weathered soil and rock.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.65-73
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• 2020

This study describes the evaluation results of pile length ratio and N value on the bearing capacity of drilled shafts in cohesionless soil. The bearing capacity ratio in Meyerhof's formula is affected only by the length ratio, and it is equally evaluated a sharing ratio of the end bearing capacity and the skin friction. NAVFAC's formula shows that the pile length influences both end bearing capacity and the skin friction, but pile length is also found to be a more influence factor on the end bearing capacity. Especially, it was found that the effect of pile length factor was larger than the effect of N value and pile diameter. FHWA's formula was evaluated to reflect the influence factor by skin friction more positively than other formulas at calculation the bearing capacity. It was also confirmed that the influence of the skin friction is larger when the ultimate bearing capacity is evaluated.

• Journal of the Korean GEO-environmental Society
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• v.7 no.5
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• pp.67-77
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• 2006

Bearing capacity of soil can be improved by several conventional ground improvement techniques like stabilization and compaction. Recently, the necessity on the reseaches for the bearing capacity of footing reinforced by Geotextile is being significantly increased. In this paper, a series of model tests on sandy ground reinforced by a layer of Geotextile were performed under plane strain condition, and the effects of bearing capacity improvement and behaviour of sandy ground were observed through tests for position and horizontal length, material strength of reinforcement.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.299-306
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• 2001

Crushed Stone Pile(CSP) is one of the ground improvement methods available to loose sand and clayey ground by forming compacted CSP in the weak soil layer. The effects of this method are enhancement of ground bearing capacity, reduction of settlement and prevention of lateral ground movement in cohesive layer, reduction of liquefaction potential in sandy ground. This study performs model tests in 1.0m${\times}$1.0m${\times}$1.0m and 1.5m${\times}$1.5m${\times}$l.2m model tank to observe bearing capacity of CSP treated ground. The area replacement ratio of CSP composite ground varies 20%, 30% and 40% with square grid pattern. After the composite ground was consolidated under pressure of 0.5kg/$\textrm{cm}^2$ and 1.0kg/$\textrm{cm}^2$, load tests were carried out. The results show that ultimate bearing capacity increases with area replacement ratio and the preconsolidation pressure of ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.784-791
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• 2008

This study is to evaluate the characteristics of bearing capacity for granite soils by N-value. The partial data is investigated for practical evaluation of weathering degree and bearing capacity on granite soils. The settlement is linearly decreased when the N-value is less than 50, but the settlement isn't constant when the N-value is more than 50. This is the affect of ground water. Therefore ground water is detailed evaluated. The bearing capacity is linearly increased when the N-value is less than 30, is inactively increased when the N-value is between 30 to 50, is constant when the value is more than 50.

• Geomechanics and Engineering
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• v.9 no.3
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• pp.287-311
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• 2015

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.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.359-366
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• 1998

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.89-99
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• 2009

Compared to standard piling methods, micropile construction can be used in downtown areas since it generates less vibration and noise. Since it only causes less soil disturbance, it is commonly used as reinforcement to existing structures. In this study, a field wherein the bearing capacity and settlement of soil can not support the weight of the superstructure was selected and micropiles were implemented instead of ordinary piles. The deformation modulus of the micropile reinforced ground was determined and was directly reflected in the design. Loading testing was used to check whether or not the allowable bearing capacity satisfies the condition of the designed bearing capacity. The computed deformation modulus based from the test was used in the numerical analysis of soil to investigate the stability of the foundation and analysis method. And a method for controlling the bearing capacity and settlement was recommended.

• Journal of Ocean Engineering and Technology
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• v.29 no.2
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• pp.175-185
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• 2015

Jack-up type WTIV(Wind Turbine Installation Vessel) is used to avoid the effects of waves when installing wind turbines in the Southwest Sea of South Korea. During the preloading procedure, unexpected penetration may cause some risks such as excessive penetration or punch-through failure. To ensure the safety of the WTIV during preloading, the bearing capacities should be evaluated based on the soil data at each borehole. Eight boreholes (OW-1 to -8) have been drilled in the Southwest Sea of South Korea. The bearing capacities of a spudcan designed to be used in this district are calculated using both a conventional analysis and finite element analysis with the soil properties of OW-1 to -8. A finite element analysis is carried out for OW-1, -3, and -4 to gain an in-depth understanding of the soil behavior during the penetration. OW-1, -3, and -4 are representative boreholes for a strong layer overlying a soft layer, a general soft layer, and a soft layer overlying a strong layer, respectively. The resultant bearing capacity curves versus the depth of the numerical analysis are compared with the conventional method. The results show that the conventional analysis is conservative. Case studies for different spudcan areas and shapes are also conducted to seek an appropriate spudcan type for the Southwest Sea of South Korea. Finally, a spudcan with a rectangular shape and a bearing area of $112.8m^2$ is selected.