• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.7-20
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• 2003

• Tunnel and Underground Space
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• v.14 no.5
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• pp.381-390
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• 2004

In this study, scaled model tests were performed to investigate the deformation behaviors around twin tunnels. Eleven types of test models which had respectively different pillar widths, rock types and loading conditions were mode, where the modelling materials were the mixture of sand, plaster and water. The models with shallower pillar width were cracked under lower pressure than the models with thicker pillar width, and they showed the more tunnel convergences and the clear spatting failures. The models of hard rock were cracked under 50% higher pressure than the models of soft rock and they showed the less tunnel convergences. The failure and deformation behaviors of twin tunnels were also dependent on the loading conditions of models. Futhermore, the results of FLAC analysis were qualitatively coincident with the test results.

• Tunnel and Underground Space
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• v.8 no.2
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• pp.87-95
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• 1998

Field instrumentation and numerical analysis by the finite difference method were applied to estimate the relaxed zone in a subway tunnel of shallow depth in soft rock, excavated by NATM. The convergence and ground displacement can be used to estimate the deformation behavior and the relaxed zone. Parameters for the several models previously suggested were measured using regression analysis techniques adopting a function of time and the face advance. The estimated relaxed zone by the MPBX and FDM analysis were 1.5~3.0 m and 1.5~2.0 m, respectively. It was concluded that the visco-elastic model and the time-dependent elasto-plastic model correlate very well ($r^2$>0.9) with results of the numerical analyses.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.147-179
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• 2002

The important role of observational method in geotechnical engineering are emphasized together with the direction of future development, concerning successful application of the technique on the site investigation, design and feed back at various construction stages. Case histories on the application of feed back are introduced in order to achieve the most economical and reliable construction for tunnel, rock slope and deep excavations through feed back system at design and construction stages. Also the limitations and advantages of the observational method and the role of feed back system are discussed for construction of tunnel, rock slope and deep excavation in hard ground such as layered ground conditions including weathered, soft and hard rocks.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5C
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• pp.359-368
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• 2006

After construction, time-variant seepage and long-term underground motion are representative factors to understand the abnormal behavior of tunnels. In this study, numerical models have been developed to analyze the behavior of tunnels associated with seepage and long-term underground motion. Possible scenarios have been investigated to establish causes-and-results mechanisms. Various parameters such as permeability of tunnel filter, seepage condition, water table, long-term rock mass load, size of damaged zone due to excessive blasting have been investigated. These are divided into two sub-parts depending on the tunnel type and major loading mechanisms depending on the types. For the soft ground tunnels, the behavior associated with seepage conditions has been studied and the effect of permeability change in tunnel-filter and the effect of water-table change which are seldom measurable are investigated in detail. For the rock mass tunnels, tunnel behavior associated with the visco-plastic behavior of rock mass has been studied and the long-term rock mass loads as a result of relaxation and creep have been considered.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.407-420
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• 2009

In this study geostatistical technique using indicator kriging was performed to evaluate the optimal rock mass classification by integrating the various geophysical information such as borehole data and geophysical data. To get the optimal kriging result, it is necessary to devise the suitable technique to integrate the hard (borehole) and soft (geophysical) data effectively. Also, the model parameters of the variogram must be determined as a priori procedure. Iterative non-linear inversion method was implemented to determine the model parameters of theoretical variogram. To verify the algorithm, behaviour of object function and precision of convergence were investigated, revealing that gradient of the range is extremely small. This algorithm for the field data was applied to a mountainous area planned for a large-scale tunneling construction. As for a soft data, resistivity information from AMT survey is incorporated with RMR information from borehole data, a sort of hard data. Finally, RMR profiles were constructed and attempted to be interpreted at the tunnel elevation and the upper 1D level.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.211-224
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• 2018

It is important to design tunnel support system considering the various loads acting on the tunnel because they have a direct impact on the stability of tunnels. In Korea, standardized support patterns are defined based on the rock mass classification system depending on the project, and it is stated that it should be modified appropriately considering the behavior of tunnel during construction. In this study, the tunnel support pattern optimization method is suggested based on the convergence-confinement method, earth pressure, axial force of rock bolt, and moment acting on the shotcrete. The length and spacing of the rock bolts and the thickness of the shotcrete were optimized by using the differential evolution algorithm (DEA) and the results were compared to the standard support pattern III for railway tunnel. Rock bolt length can be reduced and the installation interval can be widened for shallow tunnel. As the depth of tunnel increases, the thickness of shotcrete increases linearly. Therefore, the thickness of shotcrete should be thicker than the standard support pattern as the depth of tunnel increases to secure the stability of tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.3
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• pp.25-36
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• 2000

The purpose of this research work is to propose an analytical method of tunnel design based on reasonable site data. Therefore the proposed design method consists of monitoring data and Modified In Situ Rock Model. Also the Rock Mass Rating for very poor quality rock is very difficult to estimate, the balances between the ratings may no longer gives a reliable basis for the rock mass strength. But in reality Rock Mass Rating is only the property which can be obtained from face mapping records of the exposed tunnel face during construction stage. Evaluation of rock parameters for the actual design prior to tunnel construction should be corrected during tunnelling process in particularly complex ground conditions. This study intends to investigate application of in-situ rock model to soft rock tunnelling (weathered rock) by face mapping results and site measurement data that are obtained at the costraction site of Seoul Subway Tunnel. For the preparation of more reliable ground parameters, the Rock Mass Rating values for the weathered rocks were modified and readjusted in accordance with the measurement data. The modified input parameters obtained by the proposed method are used for the prediction of the tunnel behavior at subsequent construction stages. The results of this study revealed that more reasonable feed back tunnel analysis can be possible as suggested. Ample measurement data would be able to confirm the new proposed technique in this research work.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.73-81
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• 2010

The paper presents the application of FE simulations of NATM tunnel using different constitutive models. The results from a series of two dimensional plane strain finite element analyses of medium-liner interaction for NATM are presented. Four types of constitutive models are considered, namely, linear elastic, elasto-plastic Mohr-Coulomb, Hardening-Soil, Soft-Soil model. The design for tunnels requires a proper estimate of surface settlement and lining forces. It is shown that the advanced constitutive model gives better predictions for both ground movement and structural forces.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2007.10a
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• pp.63-79
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• 2007

Several remedial works were attempted to stabilize the collapsed area of the inlet slopes of diversion tunnel, but prevention of any further movement was being only carried out at beginning stage by filling the area with aggregates and rock debris, after several cracks had been initiated and developed around the area. The extra specialty developed folding zone is consisted with highly weathered Greywacke and Black shale. The suggested solution is to improve the properties of the rock mass of failed area by choosing the optimum level of reinforcement through the increment of slope rock support design so as to control the movement of slopes during the re-excavation. The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia. The power station will consist of a 210m height Concrete Faced Rockfill Dam. During the construction of the dam and the power facilities the Balui River has to be diverted of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four defined Rock Mass Type (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each "global" slope without any rock support and shotcrete system. In the second stage, it is calculated for each "local" slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.