• Journal of Korean Society of Forest Science
• /
• v.105 no.2
• /
• pp.223-230
• /
• 2016

This study was carried out to investigate the quarrying and restoration characteristics on quarry in Korea. We researched quarrying and restoration status, analyzed the relationship between restoration area and permitted period, permitted area, quarrying volume, pit slope width, height, and berm width from 55 quarry sites. Most of the quarries were located in the following conditions : mixed forest, average altitude of less than 300 m, average mountain slope of $61^{\circ}$<, hillside, granite and landslide hazard class. Major quarrying characteristics were permitted period of 6~10 years, permitted area of less than 10 ha, quarrying volume of less than $1,000,000m^3$, a stone type of aggregate, a quarrying type of terrace, pit slope of $61^{\circ}$< Most quarries were restored by themselves, and the main restoration type was slope greening. Also, area ratio of flatland, pit slope, and berm was 54.9:39.6:5.5. Ccorrelation analysis showed that quarrying area was positively correlate with quarrying volume (${\alpha}=0.01$), permitted area, pit width, and pit height (a=0.05).

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.38 no.4
• /
• pp.611-619
• /
• 2018

Basalt powder sludge (abbreviated BPS) is an inevitable industry by product resulted from the stone processing. Recently, demands for natural materials have been increasing in the construction and landscaping fields, therefore, amounts of BPS have been also increasing. Since most of BPS are used as landfill and earth soil, it is necessary to figure out to expedite their utilization. In this study, by considering the characteristics of precipitation of Jeju, effectiveness of BPS as a filler for asphalt compounds mixed with cement were analyzed. As a result, BPS satisfies quality criterion required in KS F 3501. Marshall mixing designs were performed to determine the optimal asphalt content for the Modified recycling asphalt mixture (27% recycling aggregate) and the Normal asphalt mixture. Effectiveness of BPS were identified by the Marshall Stability Test with the mixing ratio (level 3) of two asphalt compounds and composition ration (level 3) of BPS and cement. Performance of asphalt compounds shown appropriate effect of mixing and composition ratios of the filler were assessed. Test results show that two types of asphalt compounds satisfy the quality standards of the MLIT (2015). Therefore, BPS could be used as filler for asphalt compounds.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.7
• /
• pp.4960-4968
• /
• 2015

In this study to improve the chloride durability of the shotcrete structure depending on types and contents of mineral admixture chloride resistance was evaluated by NT BUILD 492 of european test standards. It was also evaluated with the mechanical properties such as static strength and chloride penetration resistance. For shotcrete mixed crushed stone aggregate of the maximum size 10mm of coarse aggregates was produced. Based on 28days compression strength the variable mixed with 15% silica fume showed the highest strength in 67.55MPa. As the content of fly ash and blast furnace slag increased, the strength lowered. In the chloride penetration resistance test, OPC showed "high grade" and In the case of admixture, the penetration resistance tended to increase in all variables except the fly ash. In order to evaluate the service life, the accelerated chloride penetration test was conducted by the standards of KCL, ACI, FIB. Test results were obtained with the lowest spreading factor in a variable mixed with silica fume of 15%. At the KCI standards, It was found to have a service life of about 65 years and at the FIB standards, It was found to have a service life of 131 years. Among standards, the service life of KCI standard in all of the variables was evaluated as the lowest.

• Journal of the Korea Concrete Institute
• /
• v.18 no.6 s.96
• /
• pp.811-817
• /
• 2006

The primary purpose of this study is to estimate the guaranteed strength and construction quality of the combined high flowing concrete which is used in the slurry wall of underground LNG storage tank. The required compressive strength of this type of concrete become generally known as a non economical value because it is applied the high addition factor for variation coefficients and low reduction factor under water concrete. Therefore, after estimation of the construction quality and guaranteed strength in actual site work, this study is to propose a suitable equation to calculate the required compressive strength in order to improve its difference. Application results in actual site work are shown as followings. The optimum nix design proportion is selected that has water-cement ratio 51%, sand-aggregate ratio 48.8%, and replacement ratio 42.6% of lime stone powder by cement weight. Test results of slump flow as construction quality give average 616~634mm. 500mm flowing time and air content are satisfied with specifications in the rage of 6.3 seconds and 4.0% respectively. Results of strength test by standard curing mold show that average compressive strength is 49.9MPa, standard deviation and variation coefficients are low as 1.66MPa and 3.36%. Also test results by cored cylinder show that average compressive strength is 66.4MPa, standard deviation and variation coefficients are low as 3.64MPa and 5.48%. The guaranteed strength ratio between standard curing mold and cored cylinder show 1.23 and 1.32 in the flanks. It is shown that applied addition factor for variation coefficients and reduction factor under water concrete to calculate the required compressive strength is proved very conservative. Therefore, based on these results, it is proposed new equation having variation coefficients 7%, addition factor 1.13 and reduction factor 0.98 under water connote.

• Korean Journal of Ichthyology
• /
• v.12 no.4
• /
• pp.236-243
• /
• 2000

The purpose of present the study was to describe the spawning behavior and early life history of the grass puffer, Takifugu niphobles. The grass puffer was caught at the spawning ground on the coast Dolsan, Korea from May to the 1998. Artificial fertilization was carried out to get fertilied eggs. Spawning season was from the end of May to the beginning of July on the coast of the Dolsan, Korea. Form 2~6 days before the spring tide the aduct males and females began to aggregate in the shore water, and they spawned in the upper part of intertidal zone exposed to air among pebble stone. The fertilized eggs were demersal, transparent and spherical in shape, and its diameter were 0.87~0.95 mm with several oil globules of 0.0014~0.0540 mm. Hatching began about 146 hours after fertilization under water temperature $21.2{\sim}22.3^{\circ}C$. The newly-hatched larva was 2.02~2.24 mm in total length (TL, mean: 2.14 mm), with 22~24(8~9+14~15) myotomes, and mouth and anus was not yet open. In 3 days after hatching it was measured 2.64~2.93 mm in TL (mean: 2.76 mm), and yolk sac was completely absorbed and transformed to postlarval stage. In 15 days after hatching it was measured 4.43~4.82mm in TL (mean: 4.59mm), and the caudal notochord flexion started. The larvae reached the juvenile stage in 28 days after hatching and attained 7.55~7.65mm in TL (mean: 7.60mm), and all fin-rays were formed.

• Journal of the Korea Concrete Institute
• /
• v.17 no.1 s.85
• /
• pp.129-137
• /
• 2005

In Korea, due to the insufficiency of natural aggregates and increasing needs of crushed stones, it is necessary to examine the alkali-silica reaction of the crushed stones. The reaction produces an alkali-silica reaction gel which can imbibe pore solution and swell to generate cracks that are visible In affected concrete. In general, crushed stones are tested by petrograptuc examination, chemical method and mortar-bar method, but the most reliable method Is mortar-bar test. This study tested alkali-silica reactivity of crushed stones of various rock types using ASTM C 227 and C 1260, and compared the results of two test methods. This study also analyzed effects of particle size and grading of reactive aggregate on alkali-silica reaction expansion of mortar-bar. The effectiveness of mineral admixtures to reduce detrimental expansion caused by alkali-silica reaction was investigated through the ASTM C 1260 method. The mineral admixtures used were nv ash, silica fume, metakaolin and ground granulated blast furnace slag. The replacement ratios of 0, 5, 10, 15, 25 and $35\%$ were commonly applied for all the mineral admixtures and the replacement ratios of 45 and $55\%$ were additional applied for the admixtures that could maintain workability. The results indicate that replacement ratios of $25\%$ for ay ash, $10\%$ for silica fume, $25\%$ for metakaolin or $35\%$ for ground granulated blast furnace slag were most effective to reduce alkali-silica reaction expansion under the experimental conditions.

• Journal of the Korea Concrete Institute
• /
• v.17 no.4 s.88
• /
• pp.569-579
• /
• 2005

An investigation for long-term strength characteristics of crushed sand concrete using crushed sands produced in Yang-san, Kim-hae and Jin-hae that can be assumed to respectively represent eastern, middle and western suburbs of Busan has been carried out. Concrete is composed of 70~80% of aggregates in whole volume so the effect of aggregates quality to the characteristics of concrete is very important. Since 1980s, aggregates used in concrete have already been substituted crushed stone because of the exhaustion of natural gravel and sand. Crushed sand tends to increase in using quantity because of the prohibition of sea sand picking and deterioration of river sand. Crushed sand is blended with river sand in order to investigate the quality changes and characteristics of concrete as variation of blend ratio of crushed sand (n, 50, 70, 80, 90, 100%). Slump and air content were measured to investigate the properties of fresh concrete. Unit weight, compressive strength and modulus of elasticity in age of 7, 28, 60, n, 180 days were measured to investigate properties of hardened concrete. Compressive strength, unit weight and modulus of elasticity were increased with a passage of time and they are expected to keep on increasing in long-term age as well. The experimental results of the qualifies of crushed aggregates in each producing area, were all satisfied with Korea Standard. The results of the measurement of slump exposed that slump preferably decreased as mixing rate increased till 70~80% but it increased to mixing rate 70~80%. The air content was exposed that it decreased by micro filler phenomenon according to that crushed sand b)ended ratio increased. According to the result of measuring unit weight in age of 7, 28, 60, 90, 180days, it increased in accordance with that blended ratio of crushed aggregates increases. As a result of measuring compressive strength and modulus of elasticity in age of 7, 28, 50, 90, 180days, compressive strength was highest when it is 70% of blended ratio.