• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.453-467
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• 2012

Usage of underground space is increasing at metropolitan city. More than 90% of flood damages have occurred at downtown of metropolitan cities. In order to prevent and/or minimize the flood-induced damage, an underground rainwater detention cavern was proposed to be built underneath existing structures. As for underground caverns to be built for flood control, multi-caverns will be mostly adopted rather than one giant cavern because of stability problem. Because of the stress concentration occurring in the pillars between two adjacent caverns, the pillar-stability is the Achilles' heel in multi-caverns. So, a new pillar-reinforcing technology was proposed in this paper for securing the pillar-stability. In the new pillar-reinforcing technology, reinforced materials which are composed of a steel bar and PC strands are used by applying pressurized grouting, and then, by applying the pre-stress to the PC strands and anchor body. Therefore, this new technology has an advantage of utilizing most of the strength that the in-situ ground can exert, and not much relying on the pre-cast concrete structure. The main effect of the pressurized grouting is the increase of the ground strength and more importantly the decrease of stress concentration in the pillar; that of the pre-stress is the increase of the ground strength due to the increase of the internal pressure. In this paper, ground reinforcing effects were verified the stress change in pillar is obtained by numerical analysis at each construction stage. From these results, the effects of pressurized grouting and pre-stress are verified.

• Magazine of korean Tunnelling and Underground Space Association
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• v.14 no.2
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• pp.61-66
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• 2012

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.927-935
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• 2013

In this study, reservoir routings for 1 hour-50 year precipitation frequency were carried out at the Engineering Water Fall and the Amphitheater located at the downstream of Seoul National University Dam. Main analysis was focus on the following matters: (1) storage amount by the tank; (2) reduction of the outflow and the peak water surface elevation; (3) change of phase lag time; and (4) design of new boxes at the inlet and outlet of storage tank. As for the storage tank of $25,000m^3$ built in the Amphitheater area, the tank induced 49.43 % storage effect, 28 min. phase lag time, and reduced the peak outflow by 49.64 %. In addition, the peak water surface elevation was lowered by 35 cm compared with that of $15,000m^3$ storage tank. It is concluded that combined management of previous storage facility and new underground storage tank would control the excessive rainfall runoff efficiently.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.231-248
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• 2017

Government plans to construct a double-deck tunnel under a portion of Gyeongbu Expressway that will solve traffic problems and could also be used as a flood storage facility. Divergence tunnels connect the main tunnel to the urban areas and their construction effects on adjacent structures at shallow depth need to be analyzed. This study primarily includes the numerical analysis of construction effects of divergence tunnels on utility tunnels. The utility tunnel was analyzed for three cases of volume loss applied to the divergence tunnel and two cases of the angle between main tunnel and divergence tunnel ($36^{\circ}$ and $45^{\circ}$). The results show that the more the volume loss was applied and the shorter the distance was between utility tunnel and divergence tunnel, the more the utility tunnel was affected in terms of induced displacements, angular displacement and stability. The worst scenario was found out to be the one where the angle between main tunnel and divergence tunnel was $36^{\circ}$ and the distance between divergence tunnel and utility tunnel was 10 m, resulting in the largest displacement and differential settlement at the bottom of the utility tunnel. A relationship between the angular displacement and the distance to diameter ratio was also established.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.670-691
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• 2018

This study presents the research results of the BMT(Benchmark Model Test) simulations of the DECOVALEX-2019 project Task B. Task B named 'Fault slip modelling' is aiming at developing a numerical method to predict fault reactivation and the coupled hydro-mechanical behavior of fault. BMT scenario simulations of Task B were conducted to improve each numerical model of participating group by demonstrating the feasibility of reproducing the fault behavior induced by water injection. The BMT simulations consist of seven different conditions depending on injection pressure, fault properties and the hydro-mechanical coupling relations. TOUGH-FLAC simulator was used to reproduce the coupled hydro-mechanical process of fault slip. A coupling module to update the changes in hydrological properties and geometric features of the numerical mesh in the present study. We made modifications to the numerical model developed in Task B Step 1 to consider the changes in compressibility, Permeability and geometric features with hydraulic aperture of fault due to mechanical deformation. The effects of the storativity and transmissivity of the fault on the hydro-mechanical behavior such as the pressure distribution, injection rate, displacement and stress of the fault were examined, and the results of the previous step 1 simulation were updated using the modified numerical model. The simulation results indicate that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing interaction and collaboration with other research teams of DECOVALEX-2019 Task B and validated using the field experiment data in a further study.