• 한국농공학회지
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• 제19권1호
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• pp.4312-4322
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• 1977

In order to investigate the effect of the water content and the accelerated curing on the strength of the soil-cement mixtures, laboratory test of soil cement mixtures was performed at five levels of water content, four levels of accelerated curing temperatures, three levels of normal curing periods, and six levels of accelerated curing time. Also this study was carried out to investigate the effect of grain size distribution of 21 types of soils on the strength of soil-cement mixtures at four levels of cement content and three levels of curing time. The results are summarized as follows: 1. Optimum moisture content increased with increase of the cement content, but maximum dry density was changed ununiformly with cement content. Water content corresponding to the maximum strength was a little higher than the optimum moisture content along the increase of cement content. 2. In molding the specimens with the optimum moisture content, the maximum strength appeared at the wet side of the optimum moisture content. 3. According to increase of curing temperature as 30, 40, 50, and 60$^{\circ}C$, unconiiend compressive strength of soil-cement mixtures increased, the rate of increase at the early curing period was large, and approximately 120 hours was suifficient to harden soil-cement mixtures completely. 4. The strength of soil-cement mixtures at the curing temperature of 10$^{\circ}C$ decreased at the rate of 30 to 50 percent than at the curing temperature of 20$^{\circ}C$, and the strength of soil-cement mixtures at the curing temperature of 0$^{\circ}C$ increased a little with increase of curing time. 5. Although the strength of soil-cement mixtures seemed to be a little affected by the temperature difference between day time and night, it was recommended that reasonable working period was the duration from July to August of which average maximum temperature of Korea was approximately 30$^{\circ}C$. 6. Accelerated curing time corresponding to the normal curing time of 28-day was shorten with increase of curing temperature, also it was a little affected by the cement. Accelerated curing time that the strength of soil-cement mixtures for the cement of 9 percent and the curing temperature of 60was shorten with increase of curing temperature, also it was a little affected by the cement. Accelerated curing time that the strength of soil-cement mix- tures for the cement of 9 percent and the curing temperature of 60$^{\circ}C$ was 45 hours at the KY sample, 50 hours at the MH, 40 hours at the SS, and 34 hours at the JJ respectively. 7. Accelerated curing time was depended upon the grain size distribution of soil, it decreased with increase the percent passing of No. 200 sieve. 8. Relationship between the normal curing times and the accelerated curing times showed that there was a linear relationship between them, its slope decreased with increase of curing temperature. 9. The most reasonable soil of the soil-cement mixtures was the sandy loam which was a well graded soil. Assuming the base of road requiring 7-day strength of 21 kg/$\textrm{cm}^2$ being used, the soil-cement mixtures could be obtained with adding 6 percent of cement in such a sails S-7, S-8, S-9, S-10, S-11, S-12, S-13. 10. The regression equation between the 28-day and the 7-day strength was obtained as follow; q28=1.12q7,+6.5(r=0.96).

• 한국지반환경공학회 논문집
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• 제7권6호
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• pp.67-73
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• 2006

본 연구에서는 하수관거의 기초나 뒷채움재로 많이 사용되고 있는 기존의 모래를 대체할 재료로써 석분의 적용가능성을 평가하기 위하여 석분재료에 대한 기본적인 물리적, 역학적인 특성실험을 실시하였다. 석분의 입도분포는 모래보다 더 좋은 상태를 나타내며, 다짐실험 결과도 모래보다 강도특성이 좋은 것으로 나타났다. 이러한 실험결과로부터 하수관거의 기초 및 뒷채움재로써 석분은 현장적용성이 우수한 것으로 평가되며, 이를 뒷받침하기 위하여 직접전단시험, 삼축압축시험을 실시하여 강도특성을 분석한 결과 모래의 경우와 유사한 경향을 나타내었다. 석분의 경우 일축압축강도 특성은 시간이 지남에 따라 점차 증가하는 경향을 보이지만 6~7일 경과 후에는 거의 일정한 값을 보이는 것을 알 수 있었다. 이와 같은 실험결과로부터 석분도 하수관거의 기초 및 뒷채움재로 충분히 활용할 수 있는 재료로 평가되었다.

• 한국지반환경공학회 논문집
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• 제13권11호
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• pp.51-60
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• 2012

동토지반의 기초구조물을 설계하는데 있어 기초의 안정성을 지배하는 설계정수인 동결토의 전단강도 및 동착강도를 측정하기 위하여 지난 50여 년 동안 많은 연구가 수행되어 오고 있다. 하지만, 아직까지 동결토의 전단강도 특성에 관한 많은 연구들은 토사 종류, 수직구속응력, 동결온도조건 등 여러 가지 영향인자 중 제한된 영향인자의 변화를 통해 수행되어 왔다. 동결토는 일반 토질과는 달리 토립자, 물, 공기뿐만 아니라 얼음을 포함한 4상으로 구성되어 있으며, 동토의 역학적인 성질의 변화는 일반적으로 온도, 수직구속응력, 동토의 구성물질에 따라 영향을 받는다. 이와 같은 동결토의 전단강도 특성을 측정하기 위하여 영하 30도의 저온환경에서도 동작이 가능하도록 설계된 동결토 직접전단시험기를 활용하였으며, 동토지역의 저온환경을 모사하기 위하여 대형 냉동챔버 내에 직접전단시험기를 설치하였다. 동결토의 전단강도 특성을 측정하기 위하여 비교적 균질한 입경분포를 지닌 주문진표준사 및 실리카모래와 입도분포가 좋은 화강풍화토를 활용하였다. 각각 세가지 시료에 대하여 전단시험은 세가지 동결온도 조건 및 수직구속응력 조건에서 수행되었으며, 그 결과를 바탕으로 동결온도조건 및 수직구속응력이 동결토의 전단강도에 미치는 영향을 분석하였다. 전반적으로 동결토의 전단강도는 동결온도가 낮아질수록 증가하는 경향을 보였으나, 수직구속응력에 의한 영향은 미미한 것으로 나타났다.

• 유기물자원화
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• 제9권2호
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• pp.77-86
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• 2001

As construction and expansion of wastewater treatment works is continuing, generation of sludge is increasing. Bur most sludge is not used appropriately but disposed by landfill dumping to sea. Furthermore direct landfilling of sludge cake containing moisture content over 75% has been legally prohibited since 2001 that's enforcement will be more strict in 2003. Such a situation means nowadays recycling of organic waste such as sludge and food waste is necessary. Composting is one of recycling methods commonly and used as an effective means of stabilizing organic waste and then compost can be used as fertilizer. However fertilizer law management which include standard of compost products and other fertilizers applied all sludge products indiscriminiately and was not flexible. So MOE has graded organic composts according to land applications to improve recycle of organic wastes. The classified organic compost which contains low contaminants has been possible to use as various purpose. This study enalyzed 30 samples which were raw materials for compost and compost products management well and to estimate the quality of compost products. Heavy metals were measured in Raw materials and OM/N, NaCl and VS were tested in compost products as well as heavy metals. As a result, approximate 10% of raw materials was not suitable to the grade A and 6.7% over the grade B of the regulation on raw materials for compost. In the case of 30 produced compost propducts approximate, 57% of composts was not compatible with the grade A and B of the regulation on composting product. The qualities of compost products were worse than raw materials, because the compost products have more regulation item raw materials have.

• 한국농공학회논문집
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• 제56권6호
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• pp.169-176
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• 2014

To evaluate bio-cementation of microbial on sands, laboratory test was conducted using acrylic cubic molding boxes ($5cm{\times}5cm{\times}5cm$). It was incubated the microbial, called Bacillus Pasteurii, according to Park et al (2011, 2012). and applied 50ml each specimen. Two type of sand samples used were Jumoonjin sand and common sand (well graded). These sands were molded in acrylic boxes with the relative density of 30 % and 60 % respectively. Microbial were poured onto the samples molded in acrylic boxes and cured at the room temperature and humidity. After 7, 14 and 21days, it was measured the compressive strength, pH, EC, and density and it were observed SEM and XRD to verify the effect of bio-cementation. It was found that bio-cementation was increased a strength of sands and it was appeared that strengths were related to the type of sand and relative density. Therefore it was confirmed the solidification of sands using the bio-cementation by microbial activation and the usefullness of acrylic molding boxes when tests were conducted on the soil of sands.