• Tunnel and Underground Space
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• v.30 no.3
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• pp.214-225
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• 2020

Uniaxial compressive strength (UCS) of rock is one of the important factors to determine the advance speed during shield TBM tunnel excavation. UCS can be obtained through the Geotechnical Data Report (GDR), and it is difficult to measure UCS for all tunneling alignment. Therefore, the purpose of this study is to predict UCS by utilizing TBM machine driving data and machine learning technique. Several machine learning techniques were compared to predict UCS, and it was confirmed the stacking model has the most successful prediction performance. TBM machine data and UCS used in the analysis were obtained from the excavation of rock strata with slurry shield TBMs. The data were divided into 8:2 for training and test and pre-processed including feature selection, scaling, and outlier removal. After completing the hyper-parameter tuning, the stacking model was evaluated with the root-mean-square error (RMSE) and the determination coefficient (R²), and it was found to be 5.556 and 0.943, respectively. Based on the results, the sacking models are considered useful in predicting rock strength with TBM excavation data.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.404-416
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• 2020

An analytical procedure for calculating the failure load of a V-shaped rock notch under two-dimensional stress conditions was developed based on the slip-line plastic analysis method. The key idea utilized in the development is the fact that the α-line, one of the slip-lines, extends from the rock notch surface to the horizontal surface outside the notch when the rock around the notch is in the plastic state, and that there exists an invariant which is constant along the α-line. Since the stress boundary condition of the horizontal surface outside the rock notch is known, it is possible to calculate the normal and shear stresses acting on the rock notch surface by solving the invariant equation. The notch failure load exerted by the wedge was calculated using the calculated stress components for the notch surface. Rock notch failure analysis was performed by applying the developed analytical procedure. The analysis results show that the failure load of the rock notch increases with exponential nonlinearity as the angle of the notch and the friction of the notch surface increase. The analytical procedure developed in this study is expected to have applications to the study of fracture initiation in rocks through wedge-shaped notch formation, calculation of bearing capacity of the rock foundation, and stability analysis of rock slopes and circular tunnels.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.271-305
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• 2020

An effect of coupled thermo-hydro-mechanical and chemical (THMC) behavior is an essential part of the performance and safety assessment of geological disposal systems for high-level radioactive waste and spent nuclear fuel. Furthermore, numerical models and modeling techniques are necessary to analyze and predict the coupled THMC behavior in the disposal systems. However, phenomena associated with the coupled THMC behavior are nonlinear, and the constitutive relationships between them are not well known. Therefore, it is challenging to develop numerical models and modeling techniques to analyze and predict the coupled THMC behavior in the geological disposal systems. It is also difficult to verify and validate the development of the models and techniques because it requires expensive laboratory tests and in-situ experiments that need to be performed for a long time. DECOVALEX was initiated in 1992 to efficiently develop numerical models and modeling techniques and validate the developed models and techniques against the lab and in-situ experiments. In Korea, Korea Atomic Energy Research Institute has participated in DECOVALEX-2011, DECOVALEX-2015, and DECOVALEX-2019 since 2008. In this study, all tasks in the three DECOVALEX projects were introduced to the researcher in the field of rock mechanics and geotechnical engineering in Korea.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.306-319
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• 2020

Characterizations of Excavation Damage Zone (EDZ), which is hydro-mechanical degrading the host rock, are the important issues on the geological repository for the spent nuclear fuel. In the DECOVALEX 2019 project, Task G aimed to model the fractured rock numerically, describe the hydro-mechanical behavior of EDZ, and predict the change of the hydraulic factor during the lifetime of the geological repository. Task G prepared two-dimensional fractured rock model to compare the characteristics of each simulation tools in Work Package 1, validated the extended three-dimensional model using the TAS04 in-situ interference tests from Äspö Hard Rock Laboratory in Work Package 2, and applied the thermal and glacial loads to monitor the long-term hydro-mechanical response on the fractured rock in Work Package 3. Each modelling team adopted both Finite Element Method (FEM) and Discrete Element Method (DEM) to simulate the hydro-mechanical behavior of the fracture rock, and added the various approaches to describe the EDZ and fracture geometry which are appropriate to each simulation method. Therefore, this research can introduce a variety of numerical approaches and considerations to model the geological repository for the spent nuclear fuel in the crystalline fractured rock.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.1
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• pp.31-43
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• 1982

Engineering phase of dairy housing systems has close connection with the milk produc- tivity of dairy cattle, the quality of milk, extension of dairy production systems, labor- saving in management of dairy cattle and the like. Moreover, the rate of investment of dairy housing facilities is of relatively high level, However, there has been almost no research effort for the improvement of engineering aspects of dairy housing systems in Korea. The purpose of this study is to find out general engineering problems and to recomm- end the improvement in dairy housing systems in Korea. Field survey by means of questionaire, direct measurements, taking pictures and sketching was conducted to get necessary information for the study. Kyung-ki Do region was firstly chosen for sampling area since it has included more than half of the number of dairy farms of the whole country. The results obtained are summarized as follows: 1. In overall dairy farm layout, the dwellings of workers were ignored in the light of sanitary environment 2. The layout of stalls in a dairy barn belongs mostly to the type of double-row face-out, which is compatible with the emphasis of manure disposal activities. 3. While the width and length of stalls were sufficiently close to the standard dimension, the width of mangers was much less than the standard dimension. 4. The width and depth of manure gutters and the width of working alleys were much. less than the standard dimension. 5. The mooring equipment was mostly in the classes of chain or rope. The watering equipment was not facilitated independantly except the one cese of using watercup. 6. The bucket milkers with one or two bucket milkers with the capacity of two cattles. each were used as milking equipment in most dairy farms. 7. There were only few milk rooms independently spaced from other space, in which the arrangement of milking equipment was much less than the standard condition. 8. The lounging ground area was averaged to be sufficient for the activity of dairy herd. 9. Silos for silage used during winter consisted of mostly bunker silos, trench silos and underground vertical silos. Ordinary vertical silos were considered for the farmers to be inconvenient for the labor saving. 10. From the view point of heat conservation and moisture removal within the dairy barns, windows were not flexible for the easy ventilation and ceiling part was not adequate for temperatur maintenance. 11. Waste treatment and disposal systems were not provided with most dairy farms, therefore the livestock waste pollution problems would be serious in the near future.

• Journal of the Korean Geotechnical Society
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• v.28 no.1
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• pp.29-39
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• 2012

The maximum unit point resistance ($q_{max}$) of rock socketed drilled shafts subjected to axial loads was investigated by a numerical analysis. A 3D Finite Difference Method (FDM) analysis and a Distinct Element Method (DEM) analysis were performed with varying rock elastic modulus (E), discontinuity spacing ($S_j$), discontinuity dip angle ($i_j$), and pile diameter (D). Based on the results of obtained, it was found that the ultimate point resistance ($q_{max}$) increased as rock elastic modulus (E) and rock discontinuity spacing ($S_j$) increased. But, it was found that $q_{max}$ decreased as pile diameter (D) increased. As for the influence of the dip angle of rock discontinuity ($i_j$), it was shown that $q_{max}$ decreased up to 50% of maximum value within the range of $0^{\circ}$ < $i_j$ < $60^{\circ}$ due to the shear failure at rock discontinuities. Furthermore, it was found that if $20^{\circ}{\leq}i_j{\leq}40^{\circ}$, influence of $i_j$ should be taken into account because $q_{max}$ tended to approach a minimum value as $i_j$ approached a value near the friction angle of the discontinuity (${\phi}_j$).

• Korean Journal of Plant Resources
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• v.17 no.2
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• pp.183-188
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• 2004

This study was conducted to investigate the effects on the growth and yield by the different seeding methods and cultivating root weight in Atractylodes macrocephata Koidz. Seeding distances were different such as 5${\times}$5 cm, 5${\times}$10 cm, 10${\times}$10 cm, 10${\times}$15 cm by the hand seeder and 15 cm seeding in drill. Emergence date, plant height were not significantly changed with seeding space, but the number of leaf, fresh weight of above-ground part and fresh weight of root were increased in the sparse seeding compared with the dense seeding. The highest fresh root yield was 1,012 kg/10 a at the 5${\times}$5 cm. Roots yield was increased in the sparse seeding compared with the dense seeding, but the highest number of roots above 16 g yield was observed at the 10${\times}$10 cm seeding distance. Emergence date was faster 1∼3 day root weight above 6 g than that root weight 5 g. The plant height, number of stem and fresh weight of above-ground part were more increased as the root weight was heavier. The growth of underground part were more increased as the root weight was heavier, yield was increased about 27％ to 112％ compared with root weight above 6 g than that 134.6 kg/10 a with root 5 g.

• Spatial Information Research
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• v.21 no.4
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• pp.71-81
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• 2013

Due to explosively increasing utilization in spatial information and a rapid development in geospatial technology related to national territorial and housing, there are increasing demands for converging spatial information on not only urban planning and real estate data but also newly generated data from smart phone, GPS to achieve comparative advantage of national territory. In this paper, we prospect the utilization of Converged Spatial Information(CSI) to future national territorial planning for the purpose of enhancing territorial competitiveness. For this purpose, considering the Korea Land and Housing corporation(LH) takes charge most of government's land and housing development projects, CSI usage of this company's 6 future business domains until 2029 were used as a case study. Also, 7 CSIs derived from literature review were surveyed to find the degree of CSI utilization in the national territorial future. In the analysis result, it was found that 3D data and mobile data among others have higher degree of utilization, and urban and regional development is the most highly utilizable domain for CSIs. After all, to revitalize the use of CSI in national territorial future, it is required to do a balanced construction of territorial use spatial information about marine use, coastal use, underground space besides land use.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.405-411
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• 2016

Seoul city is publishing new plans to increase modal share rate of bicycle every year, such as, maintaining bicycle related facilities. But bicycle's modal share rate in Seoul stayed same for the last decade and people are still facing difficulties using bicycle related facilities. These problems are causing bicycle usage as connecting transportation of public transit to decrease. This study looked at the high bicycle modal countries, such as, Netherlands, Germany and Japan to find applicable solutions by analyzing cases and comparing them with cases of highly populated subway station of Sindorim in Seoul. For example, in Germany and Netherlands there is bicycle-parking system to help bikers to access subway easier, in Japan there is underground bicycle parking tower to safely keep high volume of bicycles with in small space. For Seoul city to increase its modal share rate, they should look at problems from users' prospective and solve it by fixing it and improving the services, not by making more facilities.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.484-492
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• 2016

This study is the numerical analysis for the ground stability assessment in ${\bigcirc}{\bigcirc}$mine. The subsidence factors applied to the numerical analysis were as follows. First, the deterioration of the rock mass properties by excavation of the disturbed zone. Second, using the average lateral pressure coefficient of Korea. Third, a study of the mine history. Fourth, the excavating collapsed rock mass in numerical analysis based on the assumption that the rock mass around the goaf was collapsed due to the mining. The developed methods were applied to the cross section (5+10) of the actual subsidence in ${\bigcirc}{\bigcirc}$mine. The feasibility of the numerical analysis methods was confirmed by providing the same results as those of the actual subsidence. Next, the developed methods were applied to the cross section (3+10) that had a high probability of subsidence and the ground stability was evaluated. The analysis results show that the vertical displacement for the 5+10 cross section occurs at a maximum of 46 mm, whereas the analysis results show that the vertical displacement for the 3+10 cross section occurs at a maximum of 7 mm. Hence, it is concluded that the probability for subsidence is low.