• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.10a
• /
• pp.161-168
• /
• 2006

The recent unpredictable weather condition, especially abnormal heavy precipitation which is on the verge of PMF, made implement more rigorous design standard. Following these trends, the idea of additional auxiliary spillway, most of them are tunnel around existing one, is adopted to many sites. Tunnel spillway, having free water table is generally consisted of several compartments such as inlet, transition, inclined, curved and stilling parts. It may has some technical problems to be considered. Among them, the surface deterioration due to cavitation is reported many times in the part of irregularities on lining. Including this kind of problem, several technical considerations for tunnel spillway will be handled in this paper during design procedure.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.10a
• /
• pp.153-160
• /
• 2006

Tunnel type spillway is rarely constructed in worldwide, and designed secondary in Korea. In this paper we pronounce a case study of tunnel type spillway design. We firstly considered lining concrete abrasiveness and cavitations for tunnel safety. This paper describes the design of tunnel type spillway section, excavation method, blasting, support and concrete lining.

• Tunnel and Underground Space
• /
• v.18 no.1
• /
• pp.58-68
• /
• 2008

The construction of an emergency spillway of Imha Dam is being in progress on the granite region including fault fractured zone. Considering that this tunnel is being excavated in three paralled rows, the pillar width between each tunnel and the face distance between each tunnel face were evaluated. The Influence of the fault fractured zone for the tunnel stability was investigated by numerical modelling in 3D. Various geophysical investigations and rock engineering field tests were carried out for these purposes. It was suitable that the second tunnel would be excavated in advance, maintaining the face distance between each tunnel face of minimum 25 m. The results of numerical modelling showed that the roof displacement and the convergence of the second tunnel were insignificant, and the maximum bending compressive stress, the maximum shear stress of shotcrete and the maximum axial force of rockbolt were also insignificant. Therefore, it was estimated that the stability of the spillway tunnel was ensured.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.7 no.1
• /
• pp.63-72
• /
• 2005

The influence of internal water pressure under the Probable Maximum Flood (PMF) on tunnel spillway is analysed using 3D FDM analysis. HEC-RAS program including 1-D hydrologic numerical model was also implemented to estimate the maximum pressure on the lining under the PMF, thereafter determined rational internal water pressure. Tunnel spillway was designed as twin tunnel and excavation and supporting stage are fully considered. Analysis was classified into the 3 cases; pressure is applied only to the left tunnel, only to right tunnel, and to both tunnels. The maximum tensile stress and axial force in supporting materials induced by water flow were compared with the critical values to assess the stablilty of the tunnel and the locations of stress concentration parts were also examined.

• The Journal of Engineering Geology
• /
• v.20 no.2
• /
• pp.147-153
• /
• 2010

Cut-off wall with a low permeability can be constructed to prevent groundwater seepage in spillway tunnel areas. Three spillway tunnels are constructed in Im-ha multipurpose dam region and three types of cut-off walls with a variety of directions and scales are designed. As a result of MODFLOW modeling to assess the effect of cut-off wall for three types, groundwater inflows to the tunnels range from 64.26 $m^3/day$ to 65.49 $m^3/day$ and also they through a cut-off wall section from a reservoir do from 44.08 $m^3/day$ to 45.31 $m^3/day$ and it does not show any significant difference among them. Therefore, a construction process and an environmental conservation rather than the effectiveness of cut-off wall need to be considered to select the best cut-off wall in this region.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1726-1731
• /
• 2006

Hydraulic and numerical models were applied to design the emergency spillway of ImHa multipurpose Dam. For the numerical model, FLOW-3D was used to evaluate the three-dimensional flow in the spillway. The results of hydraulic model were compared with those of the numerical model which were separated into four zones such as approaching zone, weir zone, transition & tunnel chute zone, and dissipator zone. Moreover, for optimum design of the spillway, the hydraulic and numerical models were performed for the basic plan. Solving the problems of the basic plan, the optimized alternative design was proposed. The numerical models for various conditions of the spillway were performed, which is not always feasible in the hydraulic models. Verified by using the hydraulic models, the optimum alternative design was proposed.

• The Journal of Engineering Geology
• /
• v.23 no.1
• /
• pp.67-77
• /
• 2013

We conducted a Tunnel Seismic Prediction (TSP) survey in a spillway tunnel at Juam Dam to predict the locations of major discontinuities ahead of the tunnel face. We compared the results of the TSP survey with those from pre-construction inspections (including a surface resistivity survey and borehole investigations) as well as with direct tunnel-face mapping during excavation. The TSP method predicted the locations of major fracture zones that were unnoticed in the pre-construction inspections. The reinforcement patterns planned on the basis of pre-construction inspections were changed on the basis of the TSP results. The results demonstrate that TSP surveys are a cost-effective and reliably accurate method of predicting the locations of fracture zones. Although the TSP method has some limitations, these results suggest that the method is generally useful for predicting geological conditions prior to tunnel face construction.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.09a
• /
• pp.602-603
• /
• 2005

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.09a
• /
• pp.604-605
• /
• 2005

• Tunnel and Underground Space
• /
• v.8 no.1
• /
• pp.37-45
• /
• 1998

In this study, two dimensional and three dimensional numerical analysis were performed with a finite difference code for the safe maintenance of the spillway slope of the Boryeong dam. Results of the geological survey and the stereographic projection analysis on the discontinuities were used as input data for the numerical analysis. As a result, several suggestions were given such as the reinforcement of the local tension zone, the decrease in the angle of the slope, the drawdown of the pore pressure in the slope and the removal of the upper benches. A systematic and long-term monitoring system was also suggested.