• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.03b
• /
• pp.117-124
• /
• 2000

This paper presents the construction planning and the detail design of a 16.2 km long railroad tunnel in a mountainous area. Major design conditions for railroad are the single track, loop-typed alinement, and a maximum grade of 24.5$\textperthousand$. A underground station(double track) with a length of 1.1km is located in the middle of the line for train cross-passing. Tunnel is excavated in highly complex geological conditions including faulted areas, abandoned mine works areas, and various rock types such as sandstone, shale, limestone, and coal seam partly. Drilling and blasting method was adopted because it is more flexible than TBM(Tunnel Boring Machine) as a result of risk assessment for geological conditions in this area. Two working adits were planned to adjust the construction schedule and can be used for ventilation and maintenance in operation phase. New material and concept were introduced to the tunnel drain design. They are expected to improve tunnel drain condition and capability. Rational tunnel support design was tried to consider the various tunnel size and purpose and to use the geological investigation results.

• Tunnel and Underground Space
• /
• v.9 no.4
• /
• pp.296-305
• /
• 1999

In ordinary back analysis it if hardly possible to obtain the mechanical properties of tunnel lining by using commonly measured displacements of tunnel lining, because only a few displacements could be measured at the site. Therefore, it is necessary to develop a new method which can evaluate the state of stresses of tunnel by using measured data. In this study, in order to assess tunnel lining stability by estimating its stresses with a few measured displacements, a formulation of back analysis method was proposed. The accuracy of results were investigated through the parametric study for several types of measurement model of two dimensional elastic lining. This new back analysis method to assess tunnel lining stresses and strains with a few numbers of measured displacements showed high accuracy and good applicability when compared to the results of numerical experiments by FEM. The method has been tested on subway tunnel and its applicability has been confirmed by comparing field and analytical data. It is verified that the stress on the tunnel lining can be obtained by only more than 3 point of input displacements without any condition of external loads.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.2
• /
• pp.393-404
• /
• 2018

The tunnel can be planned to connect to underground roadway and surface road. The large tunnel and branch section are made when the ramp tunnel access to the main tunnel. In the branch section, stress concentration can be assigned and it can be very important for the stability of the tunnel. This study assessed the behavior of rock pillar in double deck tunnel diverging area by using a two dimensional numerical analysis. This study evaluated different safety factors according to pillar width and the ramp tunnel position in branch. By the assessment of the strength-stress ratio, tunnel pillar width is suggested in order to secure the safety factor 1.5.

• Tunnel and Underground Space
• /
• v.13 no.2
• /
• pp.125-137
• /
• 2003

Field measurements were carried out in this study to investigate the behavior of cut and cover tunnel such as the distribution and the magnitude of the earth pressure during back fill process. Three kinds of measuring instruments, such as the earth pressure load cell, the concrete strain gauge and the reinforcing bar meter of embedded type in concrete structure were installed and measured. Earth pressure load cells measured the outside forces acting on the tunnel lining with radial directions. Three load cells were installed at the crown, the right and the left shoulder of the tunnel, respectively. Three sets of reinforcing bar meter were installed in the double reinforcements of the tunnel lining and their locations were the same with the position of the earth pressure load cells. Concrete strain gauge was installed only one site of the upper compressive part at the tunnel crown. Based on the measurements, the deformation and the earth pressure acting on the tunnel lining were investigated with the back fill process. Considerations on the validity of the field measurements were paid.

• Tunnel and Underground Space
• /
• v.12 no.2
• /
• pp.107-114
• /
• 2002

It is the common practice to over design the reinforcement for the secondary tunnel lining due to the lack of rational insight into the ground loosening loads. and due to the conservative application of the empirical design methods. The main loads of the secondary lining are the ground Loosening loads and the ground water pressure, and the ground load is critical in the reinforcement design of the secondary lining in the case of drained tunnel. If the external load is absent around a tunnel, the reasons of the load far secondary tunnel lining are the deterioration of the primary supports such as shotcrete, steel rib, and rockbolts. Accordingly, the analysis method considering the ground-primary supports-secondary lining interaction should be required tar the rational design of the secondary tunnel lining. In this paper, the interaction was conceptually described by the simple mass-spring model and the load transfer from the ground and primary supports to the secondary lining is showed by the ground-primary supports-secondary lining reaction curves fur the theoretical solution of a circular tunnel. And also, the application of this proposed model to numerical analysis is verified in order to check the potential far the tunnel with the complex analysis conditions.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2003.03a
• /
• pp.265-272
• /
• 2003

In this study, the rock mass classification results from the face mapping and the resistivity inversion data are compared and analyzed for the reliability investigation of the determination of the rock support type based on the surface electrical survey. To get the quantitative correlation, rock engineering indices such as RCR(rock condition rating), N(Rock mass number), Q-system based on RMR(rock mass rating) are calculated. Kriging method as a post processing technique for global optimization is used to improve its resolution. The result of correlation analysis shows that the geological condition estimated from 2D electrical resistivity survey is coincident globally with the trend of rock type except for a few local areas. The correlation between the results of 3D electrical resistivity survey and the rock mass classification turns out to be very high. It can be concluded that 3D electrical resistivity survey is powerful to set up the reliable rock support type.

• Tunnel and Underground Space
• /
• v.7 no.1
• /
• pp.39-50
• /
• 1997

Reference concepts for the disposal of spent nuclear fuel and the current status of underground rock laboratory were studied. An analysis to simulate the deep disposal of spent nuclear fuel in saturated rock mass was conducted. Main input parameters for numerical study were determined based on the KBS-3 concept. A series of results showed that the temperature distribution around a cavern reached the maximum value at about 10 years after the emplacement of spent fuel. The maximum temperature at the surface of canister was more than about 12$0^{\circ}C$ at about 4 years. This temperature was not much higher than the temperature criteria to meet the performance criteria of an artificial barrier in the KBS-3 concept. The maximum upward displacement due to the heat generation of spent fuel was about 0.9cm at about 10 years after the emplacement of spent fuel. It turned out that the vertical displacement became smaller with the decrease in heat generation of a canister. The quantity of groundwater inflow into a disposal tunnel increased by about 1.6 times at 20 years after the emplacement of spent fuel with the increase of pore pressure around a cavern.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2005.09a
• /
• pp.37-42
• /
• 2005

Remote seismic tomography is regarded as one of the most valuable geophysical technique for the estimation of the rock mass classification in the tunnel area where hard data information such as drill logs are absent. But the results of rock mass classification based on the remote seismic tomography tend to be overestimated in practice. In this study, we propose the effective method to implement the seismic reference velocity ratio based on semblance for the improvement of rock mass classification. Also, to verify its feasibility, proposed technique was tested by using the real field data.

• Tunnel and Underground Space
• /
• v.9 no.3
• /
• pp.214-220
• /
• 1999

In this study, the validity of items of RMR system is evaluated and the applicability of this system to the data measured in Korean sites if discussed. Database was constructed from 139 sites, which are composed of subways, railway tunnels and road tunnels. These sites are located nationwide. Analysis shows that original classification of Bieniawski is valid although it was derived empirically. But it has considerable rating difference (error) in the result of Korean application. Thus new classification systems of KRMRI and KRMR2 are suggested, which are deduced from the Korean database. The former includes adjusted ratings and the latter adopts two more items. These are deduced by artificial neural network because it is difficult to select \`characteristic value'to estimate rock quality.

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