• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.1
• /
• pp.105-112
• /
• 2010

Applications of plant residues and green manures generally improve the properties of soil under conventional farming system. Therefore, we investigated the improvement of selected soil physical properties, bulk density, porosity, and water content, soil penetration resistance, and soil microbial biomass carbon (SMBC) content as affected by different management practices: 1) conventional tillage without rice straw or green manure crop treatment (TNT, check plot), 2) no-tillage amended with rice straw (NTRS), 3) no-tillage amended with rye (NTR), 4) no-tillage amended with Chinese milk vetch (NTCMV), 5) no-tillage without rice straw or green manure crop treatment (NTNT), The values of bulk density, porosity, and water content ranged from 1.22 to 1.37 Mg $m^3$, from 48.3 to 54.0%, and from 35.0 to 40.2%, respectively. The management practices might positively influence the changes in the selected soil properties, especially in the second experimental year. The soil penetration resistance and SMBC content were also improved after applying rice straw and green manure crops as comparing with TNT. Therefore, applications of the rice straw and green manure crop management practices under no-tillage system positively influenced soil physical properties and soil microbial activities in paddy field.

• Journal of Wetlands Research
• /
• v.20 no.3
• /
• pp.235-242
• /
• 2018

The function of vertical subsurface flow wetlands can potentially be reduced with time due to clogging and are often assumed to be occurring when ponding and overflow is observed during rainfall. To investigate their clogging potential, three pilot-scale vertical subsurface flow (VSF) wetland systems were constructed employing woodchip, pumice, and volcanic gravel as main media. The systems received stormwater runoff from a highway bridge for seven months, after which the media were taken out and divided into layers to determine the amount and characteristics of the accumulated clogging matters. Findings revealed that the main clogging mechanism was the deposition of suspended solids. This is followed by the growth of biofilm in the media which is more evident in the wetland employing woodchip. Up to more than 30% of the clogging matter were found in the upper 20 cm of the media suggesting that this layer will need replacement once clogging occurs. Moreover, no signs of clogging were observed in all the wetlands during the operation period even though an estimation of at least 2 months without clogging was calculated. This was attributed to the intermittent loading mode of operation that gave way for the decomposition of organic matters during the resting period and potentially restored the pore volume.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.203-203
• /
• 2019

도시화로 인한 불투수면의 증가는 물순환 왜곡, 비점오염원 발생 및 수생태계 건상성 훼손 등을 야기시키며, 이를 해결하기 위하여 다양한 LID 기법을 적용하고 있다. 일반적으로 LID 내 적용 되는 여재들은 무기성여재로 중량이 크고 미세공극의 부재로 물리화학적 및 생물학적 저감기능이 제한적이다. 따라서 본 연구에서는 중량성이 낮은 생물폐자원을 선정하여 LID 시설 적용성평가를 수행하고자 한다. 생물폐자원은 발생량, 경량성 및 용이성을 고려하여 꼬막껍질(CS)과 호두껍질(WS)을 선정하였다. 생물폐자원의 산화부식을 고려하여 무기성 여재인 화산석과 혼합하여 Bioretention 시설에 적용하였으며, 여재 혼합비율에 따라 총 3가지의 Case 로 구성하였다. 식생은 구절초와 꽃댕강나무를 식재하였으며, 여재의 물리적 특성 분석을 위하여 적용 전과 후의 SEM(Scanning Electronic Microscope)을 수행하였다. 모니터링은 도로퇴적물 100g과 물 110L를 제조하여 인공강우유출수를 이용하여 수행하였으며, $0.0003{\sim}0.007m^3/sec$의 유속으로 주입하였다. 시설의 유입 및 유출부에서 유량 측정 및 수질 시료를 채취하였으며, 채취된 시료는 수질오염공정 시험법에 준하여 입자상 물질, 유기물, 영양물질 및 중금속 등을 분석하였다. Bioretention 시설의 모니터링 결과를 이용하여 물수지 및 TSS 저감 효율을 산정하였으며. 물수지 분석결과 시설의 저류율은 Case 1(soil) > Case 3(WS+RV) > Case 2(CS+RV) 순으로 나타났다. 시설 내 공극률이 가장 낮았던 Case 1에서 저류율이 약 55%로 가장 높게 것으로 분석되었다. Case 3(WS+RV)은 Case 2(WS+RV)와 시설 내 공극률이 유사함에도 불구하고 저류율이 약 10% 높은 것으로 분석되었다. 오염물질 저감효율 분석 결과, TSS와 TP의 제거효율은 모든 Case에서 약 75% 이상으로 높게 나타났으며, COD의 경우 모래를 적용한 Case 1에 비해 생물폐자원인 꼬막껍질과 호두껍질을 적용한 Case에서 약 1.3배 이상 높게 나타났다. 호두껍질과 꼬막껍질의 SEM 분석 결과 표면에 다공성이 형성되어 있는 것으로 조사되었다. 이는 여과 및 저류기작으로 인한 물순환 효과증대와 다공성과 돌기사이로 인한 입자상의 물질 여과 및 흡착으로 인하여 오염물질의 제거효율이 증대 된 것으로 평가된다. LID시설 내 생물폐자원과 무기성여재를 적절히 배합하여 복합여재로 조성할 경우 침하현상을 방지할 뿐만 아니라 저류 및 침투기능 향상과 미생물의 서식환경을 제공하기에 물순환 회복 및 비점오염물질 저감에 기여할 것으로 평가된다.

• Economic and Environmental Geology
• /
• v.55 no.6
• /
• pp.649-659
• /
• 2022

This study examined the granite, quartzite, phyllite, schist, and gneiss as aggregate resources among the original rock distributed in the Chungju-Goesan area. The granite distributed in the study area is mainly composed of Jurassic biotite granite, and the quartzite layer is from the Daehyangsan quartzite Formation distributed on the upper part of the Gyemyeongsan Formation and the Hyangsan-ri dolomitic limestone Formation. In addition, phyllite is pophyrytic phyllite-schist from the Hwanggangri Formation of the Okcheon group, schist is chlorite schist, from the Munjuri Formation of the Okcheon group, and gneiss is porphyroblastic gneiss which is the upper part of the Seochangri Formation. Aggregate quality evaluation factors of these rocks included fineness modulus, absorption, unit weight, absolute dry density, solid content, porosity, resistance to abrasion, and soundness. In the case of granite, it was found to be partially unsatisfactory in terms of unit weight, solid content, porosity, and resistance to abrasion. Gneiss was found to be out of the standard values in resistance to abrasion and schist in porosity and solid content. As for the overall quality of aggregate resources, it was analyzed that quartzite, gneiss, and phyllite showed excellent quality. Aggregate quality tests are performed simply for each rock, but the rock may vary depending on the morphology of the mineral. Therefore, when analyzing and utilizing the quality evaluation of aggregate resources, it will be possible to use them more efficiently if the rock-mineralological research is performed together.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.2
• /
• pp.97-104
• /
• 2023

In order to maximize the utilization of recycled fine aggregate, high strength mortar made of 100 % recycled fine aggregate was prepared, and its physical properties were evaluated to determine the possibility of using recycled fine aggregate as structural aggregate. The effect caused by the amount of nanosilica on the physical properties of w/b 0.2 recycled fine aggregate mortar consisting of cement, silica fume, and blast furnace slag. To improve the dispersion of nanosilica inside mortar, an aqueously dispersed nanosilica solution by ultrasonic tip sonication was prepared, and incorporated into the mortar to evaluate changes in mortar flow, porosity and compressive strength depending on nanosilica content. According to the experimental results, mortar flow decreased as the replacement ratio of nano-silica increased. As the replacement ratio of nanosilica increased up to 0.75 %, the porosity decreased and the compressive strength increased, but, at a replacement ratio of 1 %, the porosity increased and the compressive strength decreased. It was confirmed that the nano-silica replacement ratio of 0.75 % was optimum proportion to maximize the mechanical performance of high-strength recycled fine aggregate mortar.

• Journal of the Korean Wood Science and Technology
• /
• v.29 no.1
• /
• pp.16-21
• /
• 2001

Improvement of sound absorption capability of wood and wood-based board by resonant absorption was attempted. Sound absorption coefficients of wood and wood-based board which contain normal, simple perforation and stair type perforation had been estimated by the tube method using standing wave ratio. Sound absorption coefficients of wood specimens of simply perforated and perforated with stair were higher than that of normal specimens. Especially, in case of stair type perforation, it was about 50 to 60% higher than that of normal specimen in the frequency of 3 to 4KHz. It was considered that the cavity which had been formed by perforation with stair type behaved as a single resonator. Wood-based board showed good sound absorption coefficients in the frequency from 125Hz to 2KHz and that of perforated board showed a little higher in the frequency from 300Hz to 500Hz than that of normal board. The computed data of resonant frequencies at several sizes of cavity showed good accordance with the estimated data of those.

• Korean Journal of Medicinal Crop Science
• /
• v.11 no.5
• /
• pp.340-346
• /
• 2003

This study was carried out to improve cultivation techniques by low cost and labour saving in ginseng (Panax ginseng C. A. Meyer) seedling production, by elucidating proper ratio virgin soil and organic fertilizer, suitable height of front piller. The obtained results are as follows ; The optimal ratio of white decomposition of virgin soil and organic fertilizer was 10:1 for good yield of standard seedling, The fittest height of front piller was 150 cm because of both good seedling growth and yield. The cost for production of seedling of ginseng could be reduced by both optimal ratio of virgin soil, organic fertilizer and selection of front piller height.

• Journal of the Korean GEO-environmental Society
• /
• v.14 no.6
• /
• pp.39-46
• /
• 2013

The field of ground amelioration, many construction methods have been developed more prosperously up to now, but even now, the majority focuses on the improvement of ground strength. And they could not suggest concrete solutions to the occurrence of environmental issues. To address this problem, soil improvement methods employing organic acid materials have recently been developed as eco-friendly technologies for increasing the soil strength, but details regarding the basic stabilization mechanism are not known yet. Against this background, this research was conducted to examine the soil stabilization mechanism; for this purpose, unconfined compressive strength and pH tests were conducted by using an improved eco-friendly organic acid material. The test results revealed that the samples processed with the organic acid showed a considerable increase in the unconfined compressive strength over time as compared to the strength of the samples that were processed without the organic acid. It was also confirmed that the organic acid material promoted microbial breeding and improved the soil structure by reducing the volume of the voids in the soil. Therefore, the sustainable development of this method needs to be analysed more in the future.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.3
• /
• pp.419-429
• /
• 2019

The characteristics of ground vibration have been analyzed by test blasting in southern region of Jeju (layered ground consisting of basalt and clinker). By grasping the principal component of ground vibration and depriving the prediction equations of ground vibration, the propagation characteristics of ground vibration have been compared to the domestic design guidelines. Ground vibration in layered ground has a small amplitude at a short distance. However, it has been confirmed that the vibration energy is transmitted further by virtue of the low attenuation of the ground vibration as it goes to a longer distance. Moreover, the frequency has been confirmed to be low frequency band. The outcome has been defined that it resulted because the clinker layer with a large pore transforms the blasting energy seismic wave with high frequency into a low frequency wave having a long waveform period. In addition, the limits of design guidelines were identified by comparing the ground vibration of Jeju and other bedrock areas. Thus, the necessity of the development of the prediction equations of ground vibration utilized in design that reflect the characteristics of the area has been suggested.

• Economic and Environmental Geology
• /
• v.53 no.1
• /
• pp.23-32
• /
• 2020

Geological CO₂ sequestration is a global warming response technology to limit atmospheric emissions by injecting CO₂ captured on a large scale into deep geological formations. The presented results concern mineralogical and hydrogeological investigations (FE-SEM, XRD, XRF, and MICP) of mudstone samples from drilling cores of the Pohang basin, which is the research area for the first demonstration-scale CO₂ storage project in Korea. They aim to identify the mineral properties of the mudstone constituting the caprock and to quantitatively evaluate the hydrogeologic sealing capacity that directly affects the stability and reliability of geological CO₂ storage. Mineralogical analysis showed that the mudstone samples are mainly composed of quartz, K-feldspar, plagioclase and a small amount of pyrite, calcite, clay minerals, etc. Mercury intrusion capillary pressure analysis also showed that the samples generally had uniform particle configurations and pore distribution and there was no distinct correlation between the estimated porosity and air permeability. The allowable CO₂ column heights based on the estimated pore-entry pressures and breakthrough pressures were found to be significantly higher than the thickness of the targeting CO₂ injection layer. These results showed that the mudstone layers in the Yeongil group, Pohang basin, Korea have sufficient sealing capacity to suppress the leakage of CO₂ injected during the demonstration-scale CO₂ storage project. It should be noticed, however, that the applicability of results and analyses in this study is limited by the lack of available samples. For rigorous assessment of the sealing efficiency for geological CO₂ storage operations, significant efforts on collection and multi-aspect evaluation for core samples over entire caprock formations should be accompanied.