• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.463-471
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• 2009

Cemented soils or concrete are usually cured under moisture conditions and their strength increases with curing time. An insufficient supply of water to cemented soils can contribute to hydration process during curing, which results in the variation of bonding strength of cemented soils. In this study, by the consideration of in situ water supply conditions, cemented sand with cement ratio less than 20% was prepared by air dry, wrapped, and underwater conditions. A series of unconfined compression tests were carried out to evaluate the effect of curing conditions on the strength of cemented soils. The strength of air dry curing specimen was higher than those of wrapped cured specimen when cement ratio was less than 10%, whereas it was lower when cement ratio was greater than 10%. Regardless of cement ratio, air dry cured specimens were stronger than underwater cured specimens. A strength increase ratio with cement ratio was calculated based on the strength of 4% cemented specimen. The strength increase ratio of air dry cured specimen was lowest and that of wrapped and underwater cured ones increased by square. Strength of air dry cured specimen dropped to maximum 30% after wetting when cement ratio was low. However, regardless of cement ratio, strength of wrapped specimens dropped to an average 10% after wetting.

• 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%.

• Magazine of the Korean Society of Agricultural Engineers
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• v.21 no.2
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• pp.81-103
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• 1979

The weathered granite soil involves problems in its stability in soil structures depending upon the reduction of soil strength due to the water absorption, crushability, and content of colored mineral and feldspar. As an attemt to solve the problems associated with soil stability, the crushability of weathered granite soil was investigated by conducting tests such as compaction test, CBR test, unconfined compression test, direct shear test, triaxial compression test, and permeability test on the five soil samples different in weathering and mineral compositions. The experimental results are summarized as follows: The ratio of increasing dry density in the weathered granite soil was high as the compaction energy was low, while it was low as the compaction energy was increased. The unconfined compressive strength. and CBR value were highest in the dry side rather than in the soil with the optimum moisture content, when the soil was compacted by adjusting water content. However, the unconfined compressive strength of smples, which were compacted and oven dried, were highest in the wet side rather than in soil with the optimum moisture content. As the soil becomes coarse grain, the ratio of specific surface area increased due to increased crushability, and the increasing ratio of the specific surface area decreased as the compaction energy was increased. The highest ratio of grain crushability was attained in the wet side rather than in the soil with the optimum moisture content. Such tendency was transforming to the dry side as the compaction energy was increased. The effect of water on the grain crushability of soil was high in the coarse grained soil. The specific surface area of WK soil sample, when compacted under the condition of air dried and under the optimum moisture content, was constant regardless of the compaction energy. When the weathered granite soil and river sand with the same grain size were compacted with low compaction energy, the weathered granite soil with crushability had higher dry density than river sand. However, when the compaction energy reached to certain point over limitation, the river sand had higher dry density than the weathered granite soil. The coefficient of permeability was lowest in the wet side rather than in the optimum moisture content, when the soil was compacted by adjusting soil water content. The reduction of permeability of soil due to the compaction was more apparent in the weathered granite soil than in the river sand. The highly significant correlation coefficient was obtained between the amount of particle breakage and dry density of the compacted soil.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.705-711
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• 2016

Crimson clover, a legume crop, is a landscape crop and green manure crop that can be sowing in spring and autumn. Its red flower blooms in May, and serves various roles such as landscape composition, weeds suppressing, prevention of soil loss and nutrient on sloping land and supplying nitrogen and organic matter in soil. Thus, in order to utilize this crop in agriculture land, we evaluated the growth characteristics of crimson clover cultivated in four different soil textures; sand, sandy loam, loam, and clay loam. The nitrogen content of crimson clover was $15.8g\;kg^{-1}$ and C/N ratio was 20.3. Its plant height was 42.5 cm in sandy loam and 49.5 cm in loamy, respectively, approximately 20 cm longer than the sand and clay loam. The crimson clover in sandy loam and loam bloomed about seven days earlier than those in sand and clay loam. Regarding number of flower per hill and flower length, there were no difference among the soil textures. Dry weight of crimson clover for sandy loam and loam was $2.5Mg\;ha^{-1}$ and $2.3Mg\;ha^{-1}$, respectively, $0.8{\sim}1.1Mg\;ha^{-1}$ higher than that of sand and sandy loam. Plant height and dry weight of crimson clover increased with delaying harvest time. Nitrogen contribution in loam and clay loam was $51.3kg\;ha^{-1}$ and $53.5kg\;ha^{-1}$, respectively. Therefore, in terms of flowering properties and dry weight, the proper soil texture for the growth and development of crimson clover was sandy loam and loam.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.129-139
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• 2002

Dielectric constant measurement has drawn much attention in the investigation of the properties and contaminations of subsurface. In this study, by varying the frequency from 75 kHz to 12 MHz, dielectric constant was measured for the weathered granite soil and Jumunjin sand having different water contents and dry density. The dielectric constant of sand showed the dispersive behavior indicating that dielectric constant decreased with frequency of an electric field. And the dielectric constant of soil increased as water content and/or dry density increased due to the decrease of air portion and/or the increase of amount of water molecules which could contribute to the development of orientation polarization. The dielectric constant of sand showed a linear relationship with the moisture density, considering both water content and dry density. At low frequency, the dielectric constants calculated by Maxwell's, Topp's and CRIM equation deviated from measured values. It could be explained by the fact that those equations did not consider dispersive behavior of dielectric constant with the frequency.

• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.5
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• pp.107-113
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• 2000

The purpose of this study is to investigate the effects of soil amendments for reducing soil compaction at heavy traffic area in golf course. Major results of this research are summarized at follows: 1. In the Lab. experiment, the porosity was improved significantly when the materials, such as peatmoss, charcoal, and tire chip mixtures were used respectively. Especially mixture of sand and 20% peatmoss showed higher effectiveness (10%) in porosity, comparing with ordinary sand. This soil mixture(sand 80%+peatmoss 20%) was observed the best in water retention, soil hardness and hydrauric conductivity. 2. In the greenhouse experiment, traffic pressure was given 7 times a day on several combination of mixture treatments to see the top dry weight. The soil mixture of 20% peatmoss showed the highest in the top dry weight. When the more traffic pressure(15 time/day) were given on the different treatment, the top dry weight was significantly reduced. However, the mixture of 20% peatmoss also had the least influence on this type of heavy traffic. 3. In the field experiment, the soil amendments were treated in traffic area f golf course, and observed at 30days, 60days, 90days, 120days after treatment. Visual turf quality(color), root length and soil compaction were compared to those of control. As a result, overall treatments with soil amendments were effective, which showed better turf quality and less soil compaction. 4. In the field test, physical characters of soil (such as soil hardness and hydrauric conductivity) in sand+tire chip+peatmoss(60:20:20, %, v/v) treatment was significantly improved. Also in the slow increasing of traffic, the soil compaction was the most effective in reducing soil hardness.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.3
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• pp.86-93
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• 2002

The objectives of this research were to investigate the effect of serpentine as a new soil conditioner for growth of turfgrass. To achieve the goal, pure sand or mixtures of sand and serpentine with various ratios were tested for soil physical properties and the growth effects of perennial ryegrass and zoysiagrass growth were compared. Major results of this research are summarized as follows; 1) Hydraulic conductivity of 10~30% serpentine mixtures were observed within the range of 1010~901mm/h which is good for USGA recommendation. Experimental results of pH and EC for various mixtures indicated that the 10% serpentine mixture was the most suitable for turfgrass growth. 2) Perennial ryegass treated with 10% serpentine mixture showed the highest visual quality(p<0.01) among all treatments. And serpentine treatment was more effective to improve visual quality of perennial ryegrass than that of zoysiagrass. The treatment of 10% serpentine had better visual qualities than that of 20% in both of zoysiagrass and perennial ryegrass. Treatment with the right amount of serpentine extends green period for one to two weeks during early winter in both zoysiagrass and perennial ryegrass. 3) In perennial ryegrass, the treatment of 10% serpentine resulted in an increase of total dry weight compare with those of zeolite or barley stone, and also dramatically promoted the dry weight by 15% compared with sand 100%(control). Total dry weight of zoysiagrass treated with 10% serpentine was 9％ higher than that of san. These results indicated that serpentine can be a good soil conditioner for both zoysiagrass and perennial ryegrass when it is blended with sand within a range of 10 to 20% by volume.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.65-70
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• 2001

As consumption rate of energy increase rapidly, the facilities of fuel storage tank become large size. Almost all of the industry or public facilities storing fuel in underground fuel storage tank is manufactured by steel materials. Thus, this fuel storage tank made of steel materials is damaged by stray-current corrosion, it become destruction. If fuel storage tank is destructed, petroleum, oil and gas are leaked. So it bring about environmental pollution, energy loss, fire and explosion. Therefor, in this study, for study on the prevention of corrosion damage in underground fuel storage tank, it were investigated by corrosion and stray-current corrosion for SS 400 in dry sea sand and wet sea sand along to specific resistance. The main results obtained are as follows : As specific resistance decrease in wet sea sand, corrosion rate per year increase linearly, in case of back fill up wet sea sand in underground fuel storage tank, if the water is flow into dry sea sand, corrosion tendency of underground fuel storage tank is supposed sensitive.

• Journal of Environmental Science International
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• v.22 no.2
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• pp.187-193
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• 2013

Dry matter allocation characteristics of Calystegia soldanella, grown in pots, was analysed to assess its plasticity in response to water-stressed conditions. As water was withheld leaf water potential between the two watering treatments was similar during the first 6 days, followed by a rapid decrease in water-stressed plants. The minimum leaf water potential was -1.50 MPa on day 15 and the maximum leaf water potential was about -0.5 MPa on day 0 in water-stressed plants. In well-watered plants leaf water potential was maintained almost consistently throughout the experiment. There was no significant difference in plant dry weight between the two watering treatments for 9 days after the start of experiment and that was remarkably increased thereafter, compared with that remained without any increase in water-stressed plants. In dry mass partitioning, however, the water-stressed plants showed a great plasticity, showing that there were 1.81, 1.35 and 0.81 times increase in root, stem and leaf, respectively. Dry mass partitioning in well-watered plants varied from 2% to 5%. The difference of dry mass partitioning between the two watering treatments was reflected in leaf mass per unit area (LMA) and root/shoot (R/S) ratio. LMA in water-stressed plants was lower than that in well-watered plants, while R/S ratio in water-stressed plants was higher in well-watered plants. This means that the water-stressed plants reduced its leaf area and increased dry mass partitioning into root and stem during the progress of soil drying. These results indicate that Calystegia soldanella inhabiting in sand dune cope with water stress with high plasticity which can adjust its dry mass partitioning according to soil water conditions.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.30-34
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• 2009

A Sand blasting technology has been used to address via and trench processing of glass wafer of optic semiconductor packaging. Manufactured sand blast that is controlled by blast nozzle and servomotor so that 8" wafer processing may be available. 10mm sq test device manufactured by Dry Film Resist (DFR) pattern process on 8" glass wafer of $500{\mu}m's$ thickness. Based on particle pressure and the wafer transfer speed, etch rate, mask erosion, and vertical trench slope have been analyzed. Perfect 500 um tooling has been performed at 0.3 MPa pressure and 100 rpm wafer speed. It is particle pressure that influence in processing depth and the transfer speed did not influence.