• Geomechanics and Engineering
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• v.5 no.1
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• pp.1-15
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• 2013

Pressure transducers are increasingly used within soil mass or at soil-structure interface for appraisal of stresses acting at point of installation. Calibration of pressure transducers provides a unique relationship between applied pressure and voltage or strain sensed by transducer during various loading conditions and is crucial for proper interpretation of results obtained from pressure transducers. In the present study an in-house calibration device is used to calibrate pressure transducers and the study is divided into two parts: 1) demonstration of developed calibration device for fluid and in-soil calibration of pressure transducers; 2) effect of soil layer thickness on the earth pressure cell (EPC) output. Results obtained from the present study revealed successful performance of the developed calibration device, and significant effect of sand layer thickness on the calibration results. The optimum sand layer thickness is obtained as 1.5 times the diameter of EPC.

• 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 Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.89-96
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• 2006

Recently, many researches on the dissipation of excess pore pressure in liquefied sand grounds have been performed to evaluate post-liquefaction behaviors of structures. In this paper. centrifuge tests were performed to simulate liquefaction behaviors of prototype soil. The evaluation model of solidified layer thickness was developed to simulate non-linear variation of solidified layer thickness with time. Also, the dissipation of excess pore pressure in liquefied sand was evaluated by applying the solidification theory and the consolidation theory. The developed model gives a good estimation of the solidified layer thickness and the time history of excess pore pressure.

• Journal of the Korea Safety Management & Science
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• v.25 no.1
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• pp.23-29
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• 2023

Among the Additive Manufacturing (AM) technologies, the Binder-Jetting printing technology is a method of spraying an adhesive on the surface of powder and laminate layer by layer. Recently, this technique has become a major issue in the production of large casting products such as ship-building, custom vehicles and so on. In this study, we performed research to make actual mold castings and increase mechanical property by using special sand and water-based binders. For use as a mold, it has a strength of more than 3MPa and permeability. Various experiments were carried out to obtain suitable them. The major process parameters were binder jetting volume, binder types, layer thickness and heat treatment condition. As a result of this study, the binder drop quantity was measured to be about 60 pico-liter, layer thickness was 100㎛ and the heat treatment condition was measured about 1,000℃ and compressive strength were measured to be more than 5MPa. The optimum condition of this experiment was established through actual casting of aluminum. The equipment used in this study was a Freeforms T400 model (SFS Co., Ltd.), and the printing area of 420 * 300 * 250mm and resolution of 600dpi can be realized.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.185-204
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• 2024

This study was conducted for evaluation the geological, physical, and chemical properties of domestic sand by analyzing about 4,800 quality data of natural sand from river and land area surveyed until 2023 through the aggregate resource survey conducted by the Ministry of Land, Infrastructure and Transport. The average depth of the Quaternary unconsolidated sedimentary layer in Korea, which includes a sand layer, is about 10m (maximum depth 66m). The thickness of the sand layer within the sedimentary layer is most dominant in the range of 0.5m to 4.0m. This accounts for about 70% of the entire sand layer. In the sand layer, the ratio of sand, gravel, and clay is 60:20:10. Regardless of the provenance or geology, the sand is mainly composed of quartz, plagioclase, and K-feldspar, and the minor minerals are muscovite, biotite, chlorite, magnetite, epidote. The sand includes in 45~75% of quartz, 5~20% of plagioclase and K-feldspar, each other. And other minor minerals are included in 10%. The average grain size of sand is 0.5mm to 1.0mm, which accounts for 44% of sand samples. The water absorption rate and soundness are estimated to be suitable for aggregate quality standard in almost all sand, and the absolute dry density is suitable for 66%.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.237-242
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• 1993

The bearing capacity of the sand foundation including a thin dense sand layer depends on the stiffiness, thickness and the location of the dense sand layer. In this paper was the influence of the dense sand layer on both the bearing capacity and the failure configuration is studied by means of K.E.M(Kinematic Element Method). K.E.M was implemented to get the excat solution starting from the upper bound of the analysis. The result show that the bearing capacity of the foundation and the failure configuration is greatly influenced by the dense sand layer, when the layer is located not deeper than 3/5 of the foundation width.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.6
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• pp.95-103
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• 2004

A turfgrass rootzone foundation is one of the important iufluences on the growth of cool-season turfgrass such as Kentucky bluegrass, which is usually grown on korean golf courses and athletic fields in Korea. This study was carried out to evaluate the growth of Kentucky bluegrass on 4 types of turfgrass root-zone foundations: a 2cm thickness of Sand 90%+Peat humus 8%+Zeolite 2% mixture on a subsoil base (C), a 20cm thickness of Sand 90%+Peat humus 8%+Zeolite 2% mixture (S), a 20cm thickness of Sand 45%+fine sand(a sort of Bomyungsa) 45%+Peat humus 8%+Zeolite 2% mixture (S+F), and a 20cm thickness of Sand 45%+fine sand(a sort of Bomyungsa) 45%+Peat humus 8%+Zeolite 2% mixture on a 20cm thick drainage layer (S+F(G)). Visual ratings of Kentucky bluegrass on the C foundation were low throughout the experiment when compared to S, S+F, and S+F(G) foundations, which contained high contents of sand with a high water infiltration rate. However, poor growth of Kentucky bluegrass in the summer of 1991 on the S foundation was likely to be caused by a too high water infiltration rate (185.8cm/hr). The growth of Kentucky bluegrass on the S+F(G) was good while the growth was a little weak at the developing stage on the S +F foundation. If the cost had to be considered when constructing golf courses and athletic fields, The S+F foundation without the drainage layer would be the best choice in terms of low cost and good quality of Kentucky bluegrass compared to the S+F(G). In this result, the infiltration rate was regarded as the most influential factor to the growth of Kentucky bluegrass on rootzone foundations.

• Geomechanics and Engineering
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• v.10 no.2
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• pp.155-174
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• 2016

A total of 104 laboratory model tests on a square footing subjected to eccentrically inclined loads supported by sand reinforced with randomly distributed polypropylene fibers were conducted in order to compare the results with those obtained from unreinforced sand and with each other. For conducting the model tests, uniform sand was compacted in a test box at one particular relative density of compaction. The effect of percentage of reinforcement used, thickness of the reinforced layer, angle of inclination of load to vertical and eccentricity of load applied on various prominent factors such as ultimate load, vertical settlement, horizontal deformation and tilt were investigated. An improvement in ultimate load, vertical settlement, horizontal deformation and tilt of foundation was observed with an increase in the percentage of fibers used and thickness of reinforced sand layer under different inclinations and eccentricities of load. A statistical model using non-linear regression analysis based on present experimental data for predicting the vertical settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) of square footing on reinforced sand at any load applied was done where the dependent variable was predicted settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) respectively.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.13-22
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• 2007

Recently, many researches on the dissipation of excess pore pressure in liquefied sand grounds have been performed to evaluate post-liquefaction behavior of structures. In this research, centrifuge tests were performed to analyze liquefaction behavior of level saturated sand grounds. Based on the test results, the evaluation model of solidified layer thickness was developed to simulate non-linear variation of the thickness with time. The thickness evaluation model was combined with the solidification theory and the consolidation theory in order to simulate dissipation of excess pore pressure. The suggested dissipation model properly estimated the solidified layer thickness and the time history of excess pore pressure.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.61-71
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• 2003

On the soft soil consisted of silty clay, the compulsion replacement method is useful for revetment and its safety is very much affected by compulsion replacement depth. Usual method calculating the compulsion replacement depth on silty clay is considered the bearing capacity of soft soil with undrained shear strength increase from ground surface and weight of revetment. But according to soil deposit, there are some cases of soft soil with inter sand layer or clayed silt, which affect the compulsion replacement depth. In this paper, the compulsion replacement depth on soft soil with inter sand layer is analyzed by layered weighted average bearing capacity considering influence effect of Perloff et al.(1967) and compared with numerical method(FLAC). In the result, the calculated depth from numerical method is nearest to layered weighted average bearing capacity in case that contact width under revetment is $0.2B_o$(soft soil with inter sand layer), $0.5B_o$(only soft soil) and the effect of contact width under revetment is less than undrained shear strength, thickness and location of inter sand layer. Also the compulsion replacement depth is as much as the inter sand thickness($d_2/B_o$) is thinner, the inter sand layer location($d_1/B_o$) is farther, and undrained shear strength is less.