• Land and Housing Review
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• v.3 no.4
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• pp.357-367
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• 2012

The efficient business scheme were suggested with the consideration of the local development condition at Ulaanbaatar. Major findings of the study were presented as follows. First, high level of education and the underground resources are presented as the merits of Mongolia. On the other side, the defects are limited domestic demands of 2.6 millions of population and the insufficiency of the infrastructure. The improvement of the infrastructures like roads, water & sewage, electric power, and heating is urgent while the development pressure of Ulaanbaatar is expected to be high due to the continuous inflow of population. Secondly, the Mongolian land system consists of the right of ownership, lease and use, therefore there are some differences among the right of land. Thirdly, definite business scheme to sell land in lots and to sell buildings in lots are suggested which are actual methods to participate in the development project in Ulaanbaatar. Moreover, enhancing the possibility to sell the lands, fixing the proper sale price to secure the profit, finding the proper buyer for the profitable lands, investing of quota and guaranteeing of granting the principal and interest by the Mongolian government, etc. are presented as consideration when participate in projects.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.1
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• pp.42-48
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• 2012

In this study, experiment on phosphorus removal was performed by using microbubble liquid film flotation tank with microbubble module. After dissolving gas and liquid in dissolving tank, microbubble liquid film system created microbubbles in equal size under fixed low pressure. After being passed through $A_2O$ and m-$O_3$ process, secondary treatment wastewater was used as influent in phosphorus removal process. When the T-P concentration of influent was 2.89 mg/L, alum(8%, 30 mg/L) was injected into a microbubble flotation tank, the treatment resulted 94% of T-P removal rate. Remaining T-P concentration was less than 0.2 mg/L, which is in accord with the effluent quality standard. Seasonal variations in water temperature showed no differences in T-P removal property. When the inflow concentration of SS was 1.0 mg/L or more, it served as coagulation nuclei in the coagulation process. In that condition, average T-P removal rate was higher than 97%. When 50% of floated scum was returned, coagulator Al included in scum assisted the injected coagulator and maximized the coagulation efficiency of pollutant. In such treatment, the T-P concentration was measured as 0.18 mg/L and satisfied the outflow water quality standard, which is 0.2 mg/L or less.

• Journal of Korean Society of Disaster and Security
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• v.15 no.3
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• pp.101-113
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• 2022

This study is planned with the aim of developing a systematic construction process based on the scientific and engineering theory of the water-sealing grouting construction applied to the tunnel excavation process during the construction of the downtown underground traffic network, so that the construction quality of the relatively backward domestic tunnel water-sealing grouting construction is improved and continuously maintained no matter who constructs it. The main contents of the improved tunnel water-sealing grouting can be largely examined in the classification of tunnel water-sealing grouting application and the definition of grouting materials, the correlation analysis of groundwater pressure conditions with groundwater inflow, the study of the characteristic factors of bedrock, and the element technologies and injection management techniques required for grouting construction. Looking at the trends in global research, research in the field of theoretical-based science and engineering grouting is actively progressing in Nordic countries (Sweden, Finland, Norway, etc.), Japan, Germany, and the United States. Therefore, in this study, the algorithm is established through theoretical analysis of the elements of tunnel water-sealing grouting construction techniques to provide an integrated solution including a construction process that can effectively construct tunnel water-sealing grouting construction.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.382-393
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• 2020

The engineered barrier system of high-level radioactive waste disposal must maintain its performance in the long term, because it must play a role in slowing the rate of leakage to the surrounding rock mass even if a radionuclide leak occurs from the canister. In particular, it is very important to clarify gas dilation flow phenomenon clearly, that occurs only in a medium containing a large amount of clay material such as a bentonite buffer, which can affect the long-term performance of the bentonite buffer. Accordingly, DECOVALEX-2019 Task A was conducted to identify the hydraulic-mechanical mechanism for the dilation flow, and to develop and verify a new numerical analysis technique for quantitative evaluation of gas migration phenomena. In this study, based on the conventional two-phase flow and mechanical behavior with effective stresses in the porous medium, the hydraulic-mechanical model was developed considering the concept of damage to simulate the formation of micro-cracks and expansion of the medium and the corresponding change in the hydraulic properties. Model verification and validation were conducted through comparison with the results of 1D and 3D gas injection tests. As a result of the numerical analysis, it was possible to model the sudden increase in pore water pressure, stress, gas inflow and outflow rate due to the dilation flow induced by gas pressure, however, the influence of the hydraulic-mechanical interaction was underestimated. Nevertheless, this study can provide a preliminary model for the dilation flow and a basis for developing an advanced model. It is believed that it can be used not only for analyzing data from laboratory and field tests, but also for long-term performance evaluation of the high-level radioactive waste disposal system.

• Tunnel and Underground Space
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• v.32 no.1
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• pp.30-58
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• 2022

The deep geological repository for high-level radioactive waste disposal is a multi barrier system comprised of engineered barriers and a natural barrier. The long-term integrity of the deep geological repository is affected by the coupled interactions between the individual barrier components. Erosion and piping phenomena in the compacted bentonite buffer due to buffer-rock interactions results in the removal of bentonite particles via groundwater flow and can negatively impact the integrity and performance of the buffer. Rapid groundwater inflow at the early stages of disposal can lead to piping in the bentonite buffer due to the buildup of pore water pressure. The physiochemical processes between the bentonite buffer and groundwater lead to bentonite swelling and gelation, resulting in bentonite erosion from the buffer surface. Hence, the evaluation of erosion and piping occurrence and its effects on the integrity of the bentonite buffer is crucial in determining the long-term integrity of the deep geological repository. Previous studies on bentonite erosion and piping failed to consider the complex coupled thermo-hydro-mechanical-chemical behavior of bentonite-groundwater interactions and lacked a comprehensive model that can consider the complex phenomena observed from the experimental tests. In this technical note, previous studies on the mechanisms, lab-scale experiments and numerical modeling of bentonite buffer erosion and piping are introduced, and the future expected challenges in the investigation of bentonite buffer erosion and piping are summarized.