• Geomechanics and Engineering
• /
• v.14 no.4
• /
• pp.387-398
• /
• 2018

The present study evaluates the interface shear strength between sand and different construction materials, namely steel and concrete, using direct shear test apparatus. The influence of surface roughness, mean size of sand particles, relative density of sand and size of the direct shear box on the interface shear behavior of sand with steel and concrete has been investigated. Test results show that the surface roughness of the construction materials significantly influences the interface shear strength. The peak and residual interface friction angles increase rapidly up to a particular value of surface roughness (critical surface roughness), beyond which the effect becomes negligible. At critical surface roughness, the peak and residual friction angles of the interfaces are 85-92% of the peak and residual internal friction angles of the sand. The particle size of sand (for morphologically identical sands) significantly influences the value of critical surface roughness. For the different roughness considered in the present study, both the peak and residual interaction coefficients lie in the range of 0.3-1. Moreover, the peak and residual interaction coefficients for all the interfaces considered are nearly identical, irrespective of the size of the direct shear box. The constitutive modeling of different interfaces followed the experimental investigation and it successfully predicted the pre-peak, peak and post peak interface shear response with reasonable accuracy. Moreover, the predicted stress-displacement relationship of different interfaces is in good agreement with the experimental results. The findings of the present study may also be applicable to other non-yielding interfaces having a similar range of roughness and sand properties.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.1005-1012
• /
• 2005

Shell-sand mixtures are commonly used for reclamation projects. This study presented the engineering properties of shell-sand mixtures. Shell shows higher specific gravities and less compressibilities than quartz sand. From large shear box tests, it can be seen that the shear strength increased with the increase of shell mixtures. At 30% shell mixtures showed about 6 increase in shear friction angle.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.1
• /
• pp.185-196
• /
• 1999

A laboratory experiment was performed to examine the relationship between resistivity and ionic components in the pore water of a sand by using soil resistivity test box and STING-Rl. The resistivity measurement was performed with the concentration changes of ionic components. Also, the resistivity change was evaluated for multiple components. The results showed that the resistivity of Arsenic was less than other heavy metals. In the case of complex components, resistivity ranges depended on the resistivity of components existed in the pore water.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.472-485
• /
• 2008

In this study, sand compaction pile method was adopted to improve the soft ground under the permanent dyke, namely west sea dyke of Incheon New Port. The row replacement ratio 30% was applied to consider the ground condition, environmental side and the construction cost of the site. The stability and displacement analysis was carried out by respectively SLOPE/W and PLAXIS 2D program. Based on this analysis, it is found that the safety factor and displacement is within an allowable criteria. The model experiment was carried out using the acryl soil box with $400(H){\times}1200(L){\times}250(W)mm$ to show the displacement of the dyke and behavior of soft ground. Based on this experiment results, it is found that the settlement does not occur from 1 and 2 loading phases and horizontal displacement of 0.0075% occurs from 2 phases. It is also found that the differential settlement occurs 0.05mm corresponding respectively 0.02% and 0.03% of the dyke height(15cm).

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.25 no.5
• /
• pp.301-310
• /
• 2013

For analyzing sand grain size, a specialized high-priced instrument has been used, such as sieve shaker, video camera, laser particle size analyzer, and microscope. Among these, the sieve shaker is commonly used because it is not only cheaper than others but also provides reasonable accuracy. However, it takes a long time and makes lots of dust and noise. In this study, a cheaper and easier method which can replace the sieve shaker is proposed. By using a commercial flat-bed scanner and a darkroom box, the sand size distribution can be analyzed. The darkroom box makes sand images clear and protects the glass of the scanner from being scratched. Comparison between the present method and sieve analysis shows that the present method not only has an accuracy comparable to the sieve analysis but also can save time and effort.

• The Korean Journal of Quaternary Research
• /
• v.15 no.1
• /
• pp.21-28
• /
• 2001

The etymology of the Chinese words for “Asian Dust" in Korea. China, and Japan has been investigated using historical records and the research results of Quan (1994) and Wada (1917) The results show that the words for Asian Dust in Korea can be found in $\boxDr$Samguksagi$\boxUl$, $\boxDr$Korysa$\boxUl$ and $\boxDr$Chosunwangjosillok$\boxUl$, which are histrorical books of Korea. In 174 AD, during the reign of King Adalla of the Silla Dynasty, “Dust Fall” was employed to describe a descending substance in the atmosphere other than water droplets (Wada, 1917; Chun et al., 2001). The terms “Dust Fall”, “Dust rain” and “Mud” were commonly used until the end of the 19th century. It was not until Japanese colonial rule (1910~1945) that “Yellow Sand” was used in Korea. The documentation on Asian Dust started far earlier in China. “Dust Fall” records were compiled as early as 1150 BC. At that time, Asian Dust was written as “Dust Fall” or “Mud”. “Yellow Sand” was recorded in 550 AD in China, however, it seems that its use was not as common as “Dust Fall”. In Japan, the first report related to Asian Bust was made in 807 AD : it used the phase “Yellow Rain”. “Mud” was recorded in 1596 and “Dust Fall” was employed in 1633 (Wada, 1917). “Yellow Sand” was used in 1939 as the title of a Japanese research paper.aper.

• Asian Journal of Turfgrass Science
• /
• v.9 no.3
• /
• pp.187-198
• /
• 1995

The objective of this research was to produce sod by box seeding for zoysiagrass or by vegetative propagation for zoysiagrass and manilagrass.1 Various ratio of peatmoss to sand(v /v) were prepared to find idea[ medium for fast and light weight sod production. Then, the days required for sod formation, the effect of growth regulators on the growth of turfgrass, and the various storage methods for winter keeping of sods were also investigated. 1.The mixed medium of sand and peatmoss(v /v, 1 : 2) showed more biomass production than that of sand. 2.In comparison of seeding rate of zoysiagrass, the amount of log /$m^2$ was most effective in the fast and dense sod formation. The amount of 20g /$m^2$ also showed fast sod formation. But, it resulted in weak plant and less tillering. During April to June, about 100 days were required to form sod with seeding rate of 5g /$m^2$ regardless of seeding time. Whereas 80 days were required to form sod in the rate log /$m^2$, which was 20 days shorter than that of 5g /$m^2$. 3.More than 85% of shoots in sod stored in field or plastic house during the winter time resumed the growth in good appearance after transplanting. The whole covering of ground with sod resulted in less weeds and faster formation of lawn. 4.Vegetative propagation of manilagrass showed about 7 to 15 days faster formation of sod than that of zoysiagrass. Application of GA increased shoot growth and BA increased the total number of tillering. However, the effects of the combined application of GA and BA were negligable.

• Journal of Korea Foundry Society
• /
• v.9 no.5
• /
• pp.403-412
• /
• 1989

This study has been carried out to investigate into the properties of molding sands containing various core sands, $CO_2$, Shell, Furan, Pep Set and Cold Box, in the system sands using domestic active bentonite. The properties of system sands with 5% bentonite and 3% moistures containing baked core sands and no-baked core sands were varied by the ratio of core sands. The system sand containing no-baked core sands had been the poor bonding force and rough grain surface than those of the baked core sands. The L. O. I of system sand containing 30% organic binders core sands were more than inorganic binders core sands. It has been found that the no-baked core sands were necessary have to reclaim for using molding sand.

• Geomechanics and Engineering
• /
• v.10 no.2
• /
• pp.155-174
• /
• 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 Korean Society of Coastal and Ocean Engineers
• /
• v.33 no.4
• /
• pp.168-178
• /
• 2021

Numerical simulations were implemented to look into the modified seabed topography due to the presence of breakwaters of varying reflection characteristics. The numerical model was composed of OlaFlow, an OpenFoam-based tool box, and a physics-based morphology model [Seoul Foam]. In doing so, the interaction between the seabed, which undergoes deformation due to siltation and scouring, and the incoming waves was described using Dynamic Mesh. The rubble-mound, vertical, and curved slit caisson breakwaters with varying reflection characteristics resulted in standing waves that differ from each other, shown to have a significant influence on the seabed topography. These results are in line with Nielsen's study (1993) that sands saltated under the surface nodes of standing waves, where the near-bed velocities are most substantial, convected toward the surface antinodes by boundary-layer drift. Moreover, the crest of sand waves was formed under the surface antinodes of standing waves, and the trough of sand waves was formed under the surface antinodes. In addition, sand wave amplitude reaches its peak in the curved slit caisson with a significant reflection coefficient, and the saltation of many grains of sand would cause this phenomenon due to the increased near-bed velocity under the nodes when the reflection coefficient is getting large.