• Journal of the Korean Geotechnical Society
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• v.39 no.1
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• pp.5-14
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• 2023

The pile driving process may lead to ground heaving, causing additional positive skin friction to act on the piles, compromising their stability. This study proposes a new pile foundation type that can reduce positive skin friction. This was investigated by designing and constructing a pile with a hydraulic cylinder which actively responds to ground deformation. The newly proposed pile design was compared against traditional piles in multiple model tests where ground heaving was simulated. In the tests, base load and total shaft resistance were measured during ground heaving and with expansion of the hydraulic cylinder. As a result of the tests, a very small amount of expansion of the hydraulic cylinder member completely reduced the positive skin friction and increased the base load. Excessive expansion of the hydraulic cylinder, however, generates negative skin friction beyond the zero skin friction state. Therefore, it is necessary to estimate the appropriate level of hydraulic cylinder expansion, taking into account the amount of ground heaving and the allowable displacement of the pile.

• Journal of the Korean Geotechnical Society
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• v.38 no.7
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• pp.49-62
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• 2022

The hollow modular concrete block reinforced foundation method is one of the ground reinforcement foundation methods that uses hexagonal honeycomb-shaped concrete blocks with mixed crushed rock to reinforce soft grounds. It then forms an artificial layered ground that increases bearing capacity and reduces settlement. The hollow modular honeycomb-shaped concrete block is a geometrically economical, stable structure that distributes forces in a balanced way. However, the behavioral characteristics of hollow modular concrete block reinforced foundations are not yet fully understood. In this study, a bearing capacity test is performed to analyze the reinforcement effectiveness of the hollow modular concrete block through the laboratory model tests. From the load-settlement curve, punching shear failure occurs under the unfilled sand condition (A-1-N). However, the filled sand condition (A-1-F) shows a linear curve without yielding, confirming the reinforcement effect is three times higher than that of unreinforced ground. The bearing capacity equation is proposed for the parts that have contact pressure under concrete, vertical stress of hollow blocks, and the inner skin friction force from horizontal stress by confining effect based on the schematic diagram of confining effect inside a hollow modular concrete block. As a result of calculating the bearing capacity, the percentage of load distribution for contact force on the area of concrete is about 65%, vertical force on the area of hollow is 16.5% and inner skin friction force of area of the inner wall is about 18.5%. When the surcharge load is applied to the concrete part, the vertical stress occurs on the area of the hollow part by confining effect first. Then, in the filled sand in the hollow where the horizontal direction is constrained, the inner skin friction force occurs by the horizontal stress on the inner wall of the hollow modular concrete block. The inner skin friction force suppresses the punching of the concrete part and reduces contact pressure.

• Geotechnical Engineering
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• v.3 no.1
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• pp.65-76
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• 1987

This study has been carried out as a basic course for the analysis of foundation deformations based on the Cap model using the finite element methods. Material parameters should firstly be determined in order to use the Cap model for numerical solution. Associated with the fact described above, a method determining the soil parameters is suggested using algorithm for numerical ana])isis from raw truly triaxial compression laboratory test data of Pueblo.Colorado sand by Zaman, et at. (1982) More specifically, the change of soil parameters Is thoroughly examined by weighting the data obtained from CTC and RTE tests, respectively. The main results obtained are as follows; 1. The obtained values of parameters (E, V and 2) are same irrespective of data obtained from various kind of tests. 2. The values of the other parameters are dependent on data used. 3. The determination of parameters is little affected by the weighting factor.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.155-162
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• 1990

In analysis of deformation in which the stiffness is greatly different between the adjacent materials, the desired results have been obtained by using the interface element method compared with those secured by the conventional method of the concept of continua. However the interface element method was originally developed for the behavior of rocks. This study deals with the deformation analysis of foundation with sand drain by the introduction of interface element. The physical conditions of interface element are devided into three categories by Mohr-Coulomb failure criterion ie. sliding, separation, and contact. Finally the accuracy of the program proposed in this paper is proved highly accurate by performing the comparison of the theoretical values and numerical results of a model element with simplified boundary conditions.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.35-43
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• 2005

Recently, various-shaped coastal structures have been studied and developed. Among them, the submerged breakwater became generally known as a more effective structure than other structures, bemuse it not only serves its original function, but also has the ability to preserve the coastal environment. Most previous investigations have been focused on the wave deformation and energy dissipation due to submerged breakwater, but less interest was given to their internal properties and dynamic behavior of the seabed foundation under wave loadings. In this study, a direct numerical simulation (DNS) is newly proposed to study the dynamic interaction between a permeable submerged breakwater aver a sand seabed and nonlinear waves, including wave breaking. The accuracy of the model is checked by comparing the numerical solution with the existing experimental data related to wave $\cdot$ permeable submerged breakwater $\cdot$ seabed interaction, and showed fairly nice agreement between them. From the numerical results, based on the newly proposed numerical model, the properties of the wave-induced pore water pressure and the flow in the seabed foundation are studied. In relation to their internal properties, the stability oj the permeable submerged breakwater is discussed.

• The Journal of the Korea Contents Association
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• v.7 no.11
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• pp.140-149
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• 2007

Social recognition conversion of the jewelry-related industries must be preceded by changes of responsibility of both the staff in charge and educators in education objections. Based on the debate of whether or not increasing (public) interest in jewelry design will subsequently lead to bringing about vision and possibility in the form of cultural management, this paper examined the influences that logical systematization of jewelry design and educational process of jewelry designers' ethics have on the next generation of the cultural industry of jewelry. Through the education and the industry of Italy, this paper analyzed existent method of design, current trend, and new content sand cases of design management that are based on types of consumption. In addition, it also provided the developmental possibility of future culture industry, and the foundation of ethical philosophy of jewelry education that lies beyond national economic power. I intend to imply significance of how designer's perception and conduct provides the whole new conventional foundation of sympathy and sensitivity and the existent method of design.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.67-72
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• 2012

Finite element method was used to compare un-piled and piled raft foundation behaviors on sandy soils in this study. The soil parameters were estimated from SPT tests of 25 boreholes. Based on these soil parameters, a finite element analysis was conducted on un-piled and piled raft foundations. For the un-piled raft, the normalized settlement parameter for raft sizes of $8m{\times}8m$ and $15m{\times}15m$ ranged from 1.02~1.15 and 0.64~0.81, respectively. The raft thickness affects differential settlement and bending moments, but has little effect on load sharing or maximum settlement. Pile spacing greatly affected the maximum settlement, the differential settlement, the bending moment in the raft, and the load shared by the piles, while the differential settlement, the maximum bending moment and the load sharing are not affected very much by increasing the pile lengths.

• Journal of the Korean Geotechnical Society
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• v.34 no.5
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• pp.53-63
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• 2018

Dynamic soil-pile interaction is the main concern in the design of group piles under earthquake loadings. The lateral resistance of the pile group under dynamic loading becomes different from that of a single pile due to the group pile effect. However, this aspect has not yet been properly studied for the pile group under seismic loading condition. Thus, in this study the group pile effect was evaluated by performing a series of dynamic centrifuge tests on $3{\times}3$ group pile in dry loose sand. The multiplier coefficients for ultimate lateral resistance and subgrade reaction modulus were suggested to obtain the p-y curve of the group pile. The suggested coefficients were verified by performing the nonlinear dynamic analyses, which adopted Beam on Nonlinear Winkler Foundation model. The predicted behavior of the pile group showed the reasonable agreement compared with the results of the centrifuge tests under sinusoidal wave and artificial wave.

• Journal of Bio-Environment Control
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• v.24 no.2
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• pp.69-78
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• 2015

In order to provide design data support for reducing gale damage of single-span greenhouses, this paper experimentally evaluated the uplift capacity of a rafter pipe and continuous pipe foundation (anti-disaster standard), usually used for single-span greenhouses according to compaction ratio, embedded depth, and soil texture. In the reclaimed soil (Silt loam) and the farmland soil (Sandy loam), the ultimate uplift capacities of rafter pipe were 72.8kgf and 60.7kgf, respectively, and those of continuous pipe foundation were 452.7kgf and 450.3kgf, respectively at an embedded depth of 50cm and compaction rate of 85% (the hardest ground condition). The results showed that the ultimate uplift capacity of continuous pipe foundation was significantly improved at more than 6 times that of the rafter pipe. The soil texture considered in this paper had a sand content of 35%~59% and a silt content of 39%~58%, and it was shown that the ultimate uplift capacity did not have a significant difference depending on soil texture, and these results show that installing the rafter pipe and continuous pipe foundation while maintaining appropriate compaction conditions can give an advantage in securing stability in the farmland of greenhouses without significantly being influenced by soil texture. Based on the results of this paper, it was determined that maintaining a compaction rate above 75% for the continuous pipe foundation and above 85% for the rafter pipe was advantageous for securing stability in greenhouses. Especially when continuous pipe foundation of anti-disaster standard was applied, it was determined to be significantly advantageous in acquiring stability in greenhouses to prevent climate disaster.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.13-23
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• 2011

Bearing capacity of pile foundations in cold region is dominated by adfreeze bond strength between surrounding soil and pile perimeter. It denotes that adfreeze bond strength is the most important design parameter for foundations in cold region. Adfreeze bond strength is affected by various factors like 'soil type', 'frozen temperature', 'normal stress acting on soil/pile interface', 'loading rate', 'roughness of pile surface', etc. Several methods have already been proposed to estimate adfreeze bond strength during past 50 years. However, most methods have not considered the effect of normal stress for adfreeze bond strength. In this study, both freezing temperature and normal stress have been controlled as primary factors affecting adfreeze bond strength. A direct shear box was used to measure adfreeze bond strength between sand and aluminum under different temperature conditions. Based on the test results, the relation between shear strength of frozen sand and adfreeze bond strength have been investigated. The test results showed that both of shear strength and adfreeze bond strength tend to increase with decreasing frozen temperature or increasing confining pressure. The ratio of shear strength and adfreeze bond strength, expressed as $r_s$, decreased initially frozen section but increased at much lower frozen temperature and there were uniform intervals under the different normal stress conditions. A method for predicting adfreeze bond strength using $r_s$ has finally been proposed in this study.