• The Journal of Engineering Geology
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• v.15 no.3
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• pp.289-301
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• 2005

Groundwater level drawdown of the first stage resulted from groundwater leakage into tunnel was predicted by an analytical approximation. And numerical modeling was performed to predict the flow rates into tunnel and the groundwater level decline in the vicinity of future proposed tunnel area using a groundwater flow model MODFLOW. Groundwater level of the first stage was predicted to decrease by 15.3 m in analytical approximation. The flow rates in the total length of the future tunnel, when it is excavated, would be approximately $1,870m^3/day$ in numerical model. The model predicts that the groundwater levels in the area around the future tunnel are expected to drop between 5 to 25 m relative to current groundwater levels. Under condition for a $50\%$ tunnel conductance increase, the flow rate was estimated to be $2,518m^3/day$ and the groundwater level drawdown was predicted to be between 5 to 35 m The flow rate and the predicted groundwater level drawdown under a $2,518m^3/day$ tunnel conductance decrease was estimated to be $1,273m^3/day$ and between 2 to 12 m.

• The Journal of Engineering Geology
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• v.20 no.4
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• pp.449-459
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• 2010

We performed numerical simulations of the excavation of an underground structure (the Giheung Tunnel) in order to evaluate the rate of groundwater flow into the structure and to estimate the groundwater level around the structure. The tunnel was constructed in Precambrian bedrock in Gyeonggi Province, South Korea. Geological and electrical resistivity data, as well as hydraulic test data, were used for the numerical modeling. The modeling took into account the strike-slip faults that cross the southern part of Giheung Tunnel, as these structures influence the discharge of groundwater into the tunnel. The transient modeling estimated a groundwater flow rate into the tunnel of $306\;m^3$/day, with a grout efficiency of 40%, yielding good agreement between the calculated change in groundwater level (6.20 m) and that observed (6.30 m) due to tunnel excavation.

• Tunnel and Underground Space
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• v.2 no.1
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• pp.123-151
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• 1992

“Norwegian Tunnelling in General" will cover the following subjects : - Short introduction to the geology of Norway - Major considerations in rock installations - Hydropower plants, roads, tunnels, oil and gas storage in rock, drinking water storage, sewage plants, frozen food storage, defence and civil defence projects, including sports arenas and swimming pools, etc.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.175-180
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• 2001

• Tunnel and Underground Space
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• v.19 no.2
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• pp.132-145
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• 2009

Faults in rock mass have strong influences on the behaviors of rock structure such as rock slope, tunnel and underground space. Thus, it is very important to analyse for the characteristics of fault rocks in design for tunnel. But, due to the limitation of geotechnical investigation in design stages, tunnel engineers have to carry out the face mapping and additional geological survey during tunnel excavation to find the distribution of faults and the engineering properties of faults for support and reinforcement design of tunnel. In this study, various geological survey and field tests were carried out to analyse the characteristics of the large thrust fault zone through the large sectional tunnel is constructed in mica-schist region. Also, the distribution of structural geology, the shape of thrust faults and the mechanical properties of fault rock were studied for the reasonable design of the reinforcement and support method for the highly fractured fault zone in the large-span tunnel.

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.115-129
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• 2015

The cut-slope of a large-sectional tunnel portal is recognized as a potential area of weakness due to unstable stress distribution and possible permanent displacement. This paper presents a case study of a slope failure and remediation for a large-scale cut-slope at a tunnel portal. Extensive rock-slope brittle failure occurred along discontinuities in the rock mass after 46 mm of rainfall, which caused instability of the upper part of the cut-slope. Based on a geological survey and face mapping, the reason for failure is believed to be the presence of thin clay fill in discontinuities in the weathered rock mass and consequent saturationinduced joint weakening. The granite-gneiss rock mass has a high content of alkali-feldspar, indicating a vulnerability to weathering. Immediately before the slope failure, a sharp increase in displacement rate was indicated by settlement-time histories, and this observation can contribute to the safety management criteria for slope stability. In this case study, emergency remediation was performed to prevent further hazard and to facilitate reconstruction, and counterweight fill and concrete filling of voids were successfully applied. For ultimate remediation, the grid anchor-blocks were used for slope stabilization, and additional rock bolts and grouting were applied inside the tunnel. Limit-equilibrium slope stability analysis and analyses of strereographic projections confirmed the instability of the original slope and the effectiveness of reinforcing methods. After the application of reinforcing measures, instrumental monitoring indicated that the slope and the tunnel remained stable. This case study is expected to serve as a valuable reference for similar engineering cases of large-sectional slope stability.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.283-292
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• 2013

A calcareous rock slope failed during excavation of the slope for construction of a tunnel entrance. The slope is located at the construction site for widening highway in Yeongwol, Korea. Field surveys, laboratory tests, and numerical analyses were performed to determine the reason for the slope failure. The numerical analysis revealed that the safety factor of the slope before construction of the entrance was less than 1, and that this decreased after construction. After construction of the entrance, the sliding zone of the slope increased and slope stability decreased because the shear strain and plastic zone in the slope over the tunnel entrance showed an increase relative to the lower part of the slope. To enhance the stability of the slope for construction of the tunnel entrance, countermeasures such as rock bolts, rock anchors, and FRP (Fiber glass Reinforced Plastic) grouting were adopted in light of the field conditions. Serial field monitoring performed to confirm the reinforcing effects of the adopted countermeasures revealed a small amount of horizontal deformation of the slope soils, most of the elastic deformation that can regain its former value. In addition, the axial forces of the rock bolt and anchor were more strongly affected by slope excavation during construction of the tunnel entrance than by tunnel excavation or the rainy season, and the axial forces tended to converge after excavation of the tunnel. Therefore, we can confirm that the slope is currently safe.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.643-653
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• 2007

Average hydraulic conductivity was $2.64{\times}10^{-8}m/sec$ average RQD was 78%, average porosity was 0.51%, and range of groundwater level was $77.06{\sim}125.97m$ by measured in 8 boreholes at the Surak Mt. tunnel area. Groundwater level of two peaks in the Surak Mt. tunnel area were estimated through linear regression analysis for groundwater level versus elevation. And, average horizontal hydraulic gradient in the Surak Mt. tunnel area was calculated 0.267. Minimum, maximum, and average hydraulic conductivities that estimated by field tests were $5.56{\times}10^{-9}m/sec,\;6.12{\times}10^{-8}m/sec,\;and\;2.64{\times}10^{-8}m/sec$, respectively. Groundwater discharge rates per 1 meter that estimated using minimum, maximum, and average hydraulic conductivities and average horizontal hydraulic gradient were $0.00585m^2/day,\;0.06434m^2/day,\;and\;0.02775m^2/day$, respectively. Pure groundwater recharge rate per unit recharge area was calculated 223.96 mm/yr through water balance analysis. Prediction simulation of groundwater level fluctuation with minimum, maximum, and average hydraulic conductivities were conducted. Discharge rate into the Surak Mt. tunnel for minimum hydraulic conductivity was small, but groundwaer drawdown was highly. Discharge rate into the Surak Mt. tunnel for maximum hydraulic conductivity was higher, but groundwaer level was recovered quickly.

• The Journal of Engineering Geology
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• v.15 no.4 s.42
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• pp.463-473
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• 2005

Because of using the same rating ranges for every rock types the RMR or the Q-system could not usually consider local geological characteristics They also could not present sufficiently the engineering anisotropy of rocks. The canonical correlation analysis was carried out with 3 kinds of face mapping data obtained from granite, sedimentary rock and phyllite in order to clarify a discrepancy between rock types. According to analysis results, as a type of rocks changes, RM factors have different influences on the total rating of RMR.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.189-202
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• 2002

In this study we carried out the in situ test in order to explore the grouting effects of fracture zone on mechanical properties and permeability in tunnel. After consolidation grouting the rock mass averaged 2.30 in the modulus of deformation and 2.49 in the modulus of elasticity. The results obtained through this study are as follows. (1) With advance of the injection steps, the total cement take shows uniformity of the rock mass. (2) After consolidation grouting the improvement of permeability can be identified by reduction of Lugeon values. (3) Grouting injection can improve deformability and strength of rock mass. (4) More mechanical improvement appears for more deformable rock mass before grouting injection.