• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.166-177
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• 1995

This study was carried out to discuss how soils in the area planned for a forest road construction can be mechanically tested and practically applied. For this, 16 soil test samples from 8 plots(2 samples per plot) were used. The major tests are focused on unit weight before and after cut, water content, liquid and plastic limits, sieve and hydrometer analysis etc. The total unit weight(${\rho}_t$) before and after cut are $1.69g/cm^3$ and $1.19g/cm^3$, respectively. Their water contents are 21.0% and 20.5%. The coefficient of uniformity U and coefficient of curvature C obtained from sieve and hydrometer analysis are 125 and 0.42, which mean generally not well graded. On the soil classification by USCS, SM(silty sand or silt-sand mixed soil)is a Key soil, but it seems to be not good for fill material. From the standard proctor test are resulted $1.40{\pm}0.065g/cm^3$ for the unit weight(${\rho}$) in the nature and $1.88{\pm}0.049g/cm^3$ for the optimum proctor unit weight(${\rho}pr$) each. With this to say, it is necessary more powerful compaction work at earth filling, with which this soil reachs enough the ${\rho}pr$, and more earth.

• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.87-93
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• 2006

To evaluate the deformational characteristics of subgrade soils, four subgrade samples in Korea were tested using the RC and TS tests with various dry unit weight and water content. Both the maximum modulus and normalized modulus reduction curves of subgrade soils were affected by the dry unit weight. The normalized modulus was decreased about 20% with increasing of relative compaction of 5%. It was founded that the variations of modulus of subgrade soils in Korea were over 40% with water content variation of $\pm$2%, and those effects can be estimated by exponential model. However, the normalized modulus reduction curves were almost identical and independent of water content. It was also founded that confining pressure, loading frequency, dry unit weight, and water content have an affect on modulus of subgrade soils independently. Therefore, it can be considered that those effects are independent variables.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.3
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• pp.254-262
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• 2024

The demand for high strength and ultra-lightweight materials to incorporate the advanced technology of nanomaterials into the lengthening of structures is continuously increasing. Therefore, based on existing research results and numerous mixing trials, we derived a mix of high strength and ultra-light concrete of a compressive strength of 100 MPa with a unit weight of 18 kN/m³ and a compr essive str ength of 80 MPa with a unit weight of 16 kN/m³ and evaluated their per for mance. In this paper, 108 specimens corresponding to high strength and ultra-lightweight concrete with a compressive strength of 100 MPa under a unit weight of 18 kN/m³, and a compressive strength of 80 MPa under a unit weight of 16 kN/m³ were manufactured, and the bond characteristics were identified by performing a directly tensile tests, and the bond characteristics were evaluated by comparing them with the experimental results and the current design criteria. It was judged that the bond strength calculation formula of ACI-408R and the experimental results were not accurately reflected, so an bond stress equation based on ACI-408R was proposed. The result of the proposed equation was that the deviation was somewhat reduced. In addition, the results of calculating the CEB-FIP model and the modified CMR model using statistical analysis showed slight differences from the experimental results, but considering that the bond behavior is a local behavior, the proposed model appears to explain the bond behavior of high strength and ultra-light concrete as a whole.

• The Journal of Engineering Geology
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• v.19 no.4
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• pp.493-499
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• 2009

Recently, the construction of Concrete Faced Rockfill Dam (CFRD) is increasing because rock material resources are plenty in Korea. Bedding zone in the CFRD is necessary enough bearing capacity to support the concrete face slab uniformly and enough impermeability to prevent the loss of fine soils in case of leakage from the concrete slab face. Therefore, cut-off the water leakage in bedding zone securely is the key factor influencing the safety of CFRD. Tested materials satisfied with the specification of particle size distribution at the Bedding Zone area are chosen for conducting permeability tests, which are done to evaluate the property of cut off the materials. Based on the test results, the effects of cut off the materials are investigated by considering the coefficient of permeability, the soil particle distribution, and the dry unit weight. Especially, the relationships between coefficient of permeability with effective size(D10), dry unit weight, and weight passing percent the No.4 sieve are suggested, and also the variation of coefficient of permeability with time are proposed.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.5-19
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• 2017

This study has been conducted to improve the conventional compaction management method by measuring the water content and dry unit weight of soil using the Time Domain Reflectometry (TDR) method. In order to verify the measured value of the developed flat TDR system, laboratory tests were conducted on six soils. Also, based on laboratory experiments, field tests were conducted to evaluate the applicability of the developed flat TDR system. Also, a comparison experiment was conducted with the Purdue TDR system. In addition, FE analysis was done to confirm the influence range of the Flat probe. As a result, it was confirmed that the influence range was about 10 cm. As a result of laboratory experiment, the water content ratio showed an error of about 0.4% on the average, and in the case of dry unit weight, it showed an error of about 1.6%. For the field test, the water content ratio and unit weight showed an error of 0.8% and 2.5%, respectively. Through the experimental results, it was confirmed that the measured value of the Flat TDR system is more accurate than that of the conventional TDR system.

• Journal of the Korean Geosynthetics Society
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• v.6 no.2
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• pp.17-20
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• 2007

In this study, a series of uniaxial unconfined compression test and constant-head test were performed to investigate the mechanical characteristics of porous concrete using recycled-aggregate for the varying unit weight and water-cement ratio. To enhance the permeability of the porous concrete, the recycled-aggregate with similar grain size in the range of $40{\pm}5mm$ was used and water-cement ratio that leads to the lean-mix was adapted. The mechanical characteristics of the porous concrete cured for 3 days were examined; the compressive strength and $E_{50}$ showed their maximum values with 40% water-cement ratio and $1.8t/m^3$ unit weight and the permeability coefficient was averagely measured in the range of $0.9{\times}10^0cm/sec$ regardless of water-cement ratio and unit weight.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3731-3735
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• 2015

This study reports the relationship between rollingstock weight and acceleration performance for HEMU-430X, the first electric multiple unit developed in Korea. While maintaining the consumed power, the total train weight was deliberately varied by 2%, by adding and removing weights, and the it was shown that the lighter train was found to have higher acceleration performance and hence better suited for maximum speed tests below the speed of 413km/h. According to the power consumption analysis based on the velocity data collected per 0.1 second, the balanced speed, when the traction force and air resistance become equal, was determined to be 419km/h for HEMU-430X, which is in agreement with tested result. It is expected that the analyses in this study will be utilized for the speed tests in the future.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.49-59
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• 2019

In this study, the durability of conical pick cutter was compared and analyzed by pre- and post-test visual inspection, measurement of weight loss and wear volume through field test on two types of conical pick cutters applied to rotary drum cutter. In the visual inspection, it was found that only 9 inserts were lost in the slim type conical pick cutter. This result show that the thickness of the head cover surrounding a insert was important to maintain the insert during excavation. The weight loss and wear volume of the heavy type conical pick cutter were less than half that of the slim type. From these results, it can be confirmed that heavy type is more useful than slim type in hard rock. It should be noted that, when determining the wear loss of the conical pick cutter, the mutual comparison of the weight measurement and the wear volume measurement results may be different due to the unit weight of the material and the spalling caused by excavation.

• Economic and Environmental Geology
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• v.44 no.1
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• pp.71-82
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• 2011

The unsaturated soil column tests were carried out for weathered gneiss soil and weathered granite soil in order to obtain the relationship between rainfall intensity and infiltration velocity of rainfall on the basis of different unit weight conditions of soil. In this study, volumetric water content and pore water pressure were measured using TDR sensors and tensiometers at constant time interval. For the column test, three different unit weights were used as in-situ condition, loose condition and dense condition, and rainfall intensities were selected as 20 mm/h and 50 mm/h. In 20 mm/h rainfall intensity condition, average rainfall infiltration velocities for both gneiss and weathered granite soils were obtained as $2.854{\times}10^{-3}$ cm/s ~ $1.297{\times}10^{-3}$ cm/s for different unit weight values and $2.734{\times}10^{-3}$ cm/s ~ $1.707{\times}10^{-3}$ cm/s, respectively. In 50 mm/h rainfall intensity condition, rainfall infiltration velocities were obtained as $4.509{\times}10^{-3}$ cm/s ~ $2.016{\times}10^{-3}$ cm/s and $4.265{\times}10^{-3}$ cm/s ~ $3.764{\times}10^{-3}$ cm/s respectively. The test results showed that the higher rainfall intensity and the lower unit weight of soil, the faster average infiltration velocity. In addition, the weathered granite soils had faster rainfall infiltration velocities than those of the weathered gneiss soils except for the looser unit weight conditions. This is due to the fact that the weathered granite soil had more homogeneous particle size, smaller unit weight condition and larger porosity.

• Cement
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• s.76
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• pp.51-56
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• 1979

F.L.Smidth는 기획적인 규모로 광범위한 시험과 운용을 한 후에 신형의 크리카 밀을 개발했다. 이 밀의 미분쇄실에서는 평균 단위중량이 5$\~$7g 밖에 안되는 최적 크기의 분쇄매체가 사용된다. 이의 사용은 특수하게 설계된 밀의 출구와 전연 새로운 원리에 바탕을 둔 매우 효율적인 스크리닝 diaphragm에 의해서 가능하게 되었다. Conbidan 밀은 개회로나 폐회로식 분쇄에서 모두 최저의 분쇄 효율을 보장하기 때문에 에너지 소비량이 상당히 절감된다. 완성시멘트에서 요구되는 입도에 따라서, 그리고 채택된 분쇄방법에 따라서 Conbidan 밀의 분쇄 효율은 (kg/kwh), 기업적인 규모로 장기에 걸쳐 시험한 결과로 나타난 바와 같이, $12\%\~27\%$가 향상된다.