• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1091-1104
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• 2018

Wear prediction of TBM disc cutters is a very important issue during design as well as construction stages for hard rock TBMs as the cutter head intervention is directly related to the time and cost of tunneling. For that, some methods such as NTNU, CSM and Gehring models were used to predict disc cutter wear and intervention interval. There are however some problems to be addressed in these models in terms of accuracy and time for testing, so that a NAT (New Abrasion Tester) model has been developed in order to achieve simplicity and reliability together at the same time (Farrokh and Kim, 2018). On the basis, the proposed NAT model has been applied to ${\bigcirc}{\bigcirc}$ project in Korea. A comparative study was performed to compare with the conventional methods and as a result the NAT model showed a very good agreement with actual cutter life. The NAT model will be further applied to other projects to establish credibility.

• Journal of the Korea Institute of Building Construction
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• v.11 no.6
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• pp.530-537
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• 2011

The purpose of this study is to examine material performance of fiber reinforced cement composite for mass production. It is necessary to manufacture SHCC(Strain Hardening Cement Composite) by batch plant for field application and mass production. For the study, a mock-up test of SHCC manufactured in the batch plant was conducted, and the performance was compared with SHCC manufactured in the laboratory. Assessment items were freshness and hardening properties. Specifically, direct tensile test machine was used for performance verification of SHCC. As a result, there was a tendency of less satisfactory fiber dispersion and performance of strain hardening compared with the performance of SHCC manufactured in the laboratory. To address this, dry mixing and mortar mixing time should be increased compared to laboratory mixing, and injection time of an agent such as a water reducing agent should be properly controlled according to mixing combination, or the capacity to secure dispersion and homogeneity of material.

• Journal of the Korean Geosynthetics Society
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• v.13 no.2
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• pp.21-29
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• 2014

The use of filling material based on cement paste is inefficient at field construction because it needs a lot of the charging mass. In addition, it has environmental problem according to the large amount of cement use because its strength is also larger than criterion. The excavated soil with stabilizer can be used as the filling materials when the bored pile is constructed. Therefore, this paper describes field application of solidified soil for economical efficiency and environment-friendly. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. As results, the flowability, segregation and bleeding, and bond strength of filling materials was a good performance than that of the existing cement paste. But the skin friction of pile by PDA was slightly decreased than that of the existing cement paste. However, as pile filling materials, and in terms of economics and environment, the applicability of filling material is considered very effective.

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.15-21
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• 2012

It is difficult to determine the strength and the permeability of a soil levee quantitatively because the damages of a levee have been evaluated only by visual inspection in Korea. Therefore, it is necessary to develop a simplified measurement device for measuring the strength and permeability of a levee. In this paper, a new in-situ permeability measuring device which can measure strength and permeability based on GWP is developed and its applicability to the field permeability test of a soil levee is introduced. From the laboratory and in-situ experiments, the new measuring device has the potential of measuring the soil permeability simply and accurately.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.977-980
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• 2008

Recently, the study on the application of SCC(Self-Compacting Concrete) is actively underway, in order to solve the lack of flowability and the poor compacting which is one of the chronic problems of tunnel lining concrete. The aim of this study is that to verify the validity of the application of SCLC(Self-Compacting Lining Concrete) for tunnel lining concrete and to examine the characteristic of flowing and mechanics of SCLC in term of comparing before and after casting SCLC was developed by Packing Factor mix method and casted in field mix-design according to the condition of site and the characteristic of aggregate. Before casting, the tests of the capability of flowability and durability was performed by slump flow, air void and so on. Additionally, the slump flow loss is measured to evaluated the possibility of cast-in-place. Furthermore, considering on the first time SCLC casting applied to the tunnel lining in Korea, it is provided that the careful items and the correct way for construction when applied the SCLC on site.

• Journal of the Korean Geotechnical Society
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• v.26 no.1
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• pp.55-62
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• 2010

Dynamic soil resistances were simulated by modified Ramberg-Osgood model in order to predict penetration rate of sheet pile installed by vibratory pile driver. Various factors which characterize modified Ramberg-Osgood model were determined considering the shapes of dynamic soil resistance curves obtained from field test and standard penetration value (N value) was used as parameter that relates field test results to the suggested model. Penetration rates calculated by analytical model were smaller than those of field test and penetration times were vice versa. Therefore, predicted penetration rate and penetration time by analytical model are more conservative than those of filed test.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.415-415
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• 2020

국내 농업용수 수요량 산정에 있어서 논벼 수요량은 수정 Penman (Modified Penman: MP) 방법에 의한 증발산량을 기반으로 산정하고 있으나, 최근 국제식량농업기구 (Food and Agriculture Organization of the United Nations: FAO) 및 국내 농진청 등에서는 Penman-Monteith (PM) 방법에 의한 증발산량 산정방법을 채택하고 있다. 따라서 본 연구에서는 논벼 수요량 산정에 있어 우리나라 실제 현장여건에 적합한 논벼 증발산량 산정 방법을 제안하고자 기존에 적용하고 있는 MP 방법과 최근에 국내외적으로 제안되고 있는 PM 방법에 의한 논벼 수요량 산정 결과를 실질적으로 벼 생산에 공급된 저수지 공급량 자료와 비교 분석을 통해 현장 적용성을 평가해 보았다. 이를 위해 본 연구에서는 농진청에서 PM 증발산량 작물계수를 도출한 현장실험지구를 포함하는 호남지역을 대상으로 저수지 100 만톤 이상의 한국농어촌공사 관리지역 중 농업용수 공급량 자료가 신뢰성 있는 대표지구를 선정하였다. 농업용수 실제 공급량 자료를 기반으로 두 증발산량에 의한 논벼 수요량 산정 결과를 비교 분석한 결과, MP 방법에 의한 수요량이 PM 방법에 의한 수요량 보다 높게 나타났으며, 따라서 MP 방법에 의한 수요량이 PM 방법에 의한 수요량 보다 농업용수 공급량과의 차이가 작게 나타나는 경향을 보였다. 대체적으로 강우량이 적은 지역에서 농업용수 공급량 및 논벼 수요량이 높게 나타났으며, 이러한 결과는 공급량과 수요량간의 관계에도 영향을 미쳐 강우량이 많은 지역에서 강우량이 적은 지역에 비해 농업용수 공급일수가 감소함으로써 공급량과 수요량과의 차이가 적어지는 경향을 보였다. 본 연구 결과로 농업용수 공급량을 기준으로 논벼 수요량 산정에 있어 증발산량 산정방법은 안정적인 농업용수 공급계획과 수리시설 설계에서의 이수안전도 확보차원에서 MP 방법을 채택하는 것이 더 바람직 할 것으로 사료된다. 추가적으로 논벼 수요량 산정은 증발산량 산정방법 외에도 유효우량 산정방법, 수로손실, 재배관리손실 등의 다양한 관련 인자들의 영향을 받기 때문에 증발산량 산정방법과 더불어 이들 인자들에 대해서도 종합적인 평가를 실시하여 논벼 수요량 산정 결과의 신뢰성 확보가 요구된다.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.4
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• pp.315-322
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• 2008

Valves in power plants are leaking internally by various damages including insertion of foreign objects on seat, seat crack, defects and fatigue crack of stem packing or welds etc. due to severe operating conditions such as high temperature and high pressure for extended period time. Acoustic emission(AE) technology should be applied in order to diagnose precisely and evaluate these valve internal leak. In this paper, results of studies which have accomplished in actual power plant are presented. We have analyzed background noise, AE signal level and frequency spectrum through laboratory tests on the basis of various actual conditions in power plant, and also have considered evaluation methods on the background noise, AE properties and the detectable minimum leak rate according to valve leak conditions through comparing with results of field tests in power plant. As a result of these studies, we conformed that evaluation of internal leak conditions including discrimination of leak or not, and the detectable minimum leak rate is possible, and also it is expected to contribute to safe operation and prevention of energy loss in power plants.

• Journal of Digital Contents Society
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• v.12 no.1
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• pp.33-48
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• 2011

In this thesis, a field experience activity support system is designed and implemented for improving social skills of children with developmental disabilities. The proposed system is designed to allow the students to experience various field activities around their local community. The proposed system has the following characteristics. First, it can improve effectiveness of field experience by providing very practical pre-study information to students. Second, the systems provides very practical and real-world problem-solving abilities rather than providing simple experience and superficial information. Third, the system allows students to change the contents according to their local community environments and purpose of use. Fourth, the system can be used as education for living at home as well as field experience study at schools. After applying the proposed system to students with developmental disabilities, the following positive results are obtained. First, the system have good effect on students with severe developmental disabilities when the system is used for prestudy. Specially those students are highly interested and motivated on study subjects. Second, at real field experience study place, students are well adapted and are very interested in their activities. Third, in the light of post-evaluation after field experience, it is reported that lots of study contents remain in their memory.

• Resources Recycling
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• v.29 no.1
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• pp.43-52
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• 2020

The objectives of this study were to identify the optimal mix of foam concrete with the low-strength and high-flow for the repairing ground subsidence situation emergently by utilizing a large amount of industrial by-products and evaluate the possibility by applying it to the site. The factors of the experiment were the mixing ratio of mixing water and a foaming agent and the mixing ratio of foam over paste volume. The optimal mix identified by the experiment was applied to the field and basic properties were evaluated. The results of the experiment showed that the optimal mixing ratio of mixing water and the foaming agent was 10%. Moreover, when the mixing ratio of pre-foam over paste volume was 170%, it satisfied the target. However, to ensure stable quality when applying to the field, the foam mixing ratio was set 140% for the field application. The field application test of foam concrete with the low-strength and high-flow using an eco-friendly binder satisfied all target performances. Therefore, the possibility of using it as a mixture and construction method for a ground repair system is confirmed. However, there was a quality deviation between the upper part and the lower part due to the separation between foam and paste. Consequently, further studies are needed to improve it.