• Tunnel and Underground Space
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• v.9 no.3
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• pp.171-174
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• 1999

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1957-1968
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• 2013

Design criteria for rock load on tunnel concrete lining has not been established yet. Generally rock load on tunnel concrete lining is empirically estimated, which leads to a conservative design. Ordinary estimation method of rock load includes various problems. Estimating by numerical analysis is very complicated and has not been verified with field measurements. Therefore, it is necessary to conduct a study on practical method of estimating rock load which is more accurate to the real rock load on tunnel concrete lining. This study, presents estimation method of rock load on tunnel concrete lining. Crown settlement of the tunnel construction site has been measured and it was been back analyzed to estimate the rock load. The rock load was estimated to be smaller compare to the ordinary estimation method.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.89-94
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• 2006

We, presently, don't have clear diagram methods and analysis criteria in rock bolt pull test usable for tunnel reinforcement. So this paper has suggested that; first, 'scheme of apposite diagram method at hard rock and the different application method of rock bolt pull test at weathered and hard rock', and second, 'the pullout capacity specification criteria for design and construction of rock bolt', based on foreign criteria and field test.

• Tunnel and Underground Space
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• v.6 no.2
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• pp.122-130
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• 1996

Generally the NATM technique uses shotcrete, rock bolts, H-beam steel ribs, and concrete lining for the tunnel support in Korea. Among them, H-beam steel ribs are extremely heavy and difficult for workers to handle. Therefore, especially in Europe, lattice girders are being used instead of H-beam steel ribs for tunnel support. Lattice girders have basically the same function as H-beam steel ribs in tunnelling. The main advantages of using lattice girders compared to H-beam steel rib supports are as follows: 1) lattice girders have relatively a low weight enough to be easily lifted and installed by labors and 2) they create a more effective bond with the shotcrete. The purpose of this study is to evaluate the effectiveness and applicability of lattice girders compared to H-beam steel ribs used in construction tunnel sites and to show that lattice girders can be adequately applied in domestic tunnel construction sites as a new tunnel support system.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.333-340
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• 2011

RMR is most strongly adopted rock classification method to scheme support system in domestic tunnel. However the RMR, which is based on geological survey during design stage of tunnel, can't present the real ground accurately. In this study, authors suggested Weighted-RMR (W-RMR) which is considered weighted value of risk factors of collapse due to prevent collapse and roof falls during tunneling. According to the application of W-RMR to Bye-Gye tunnel, we could change support type flexibly by the risk factors on a face of tunnel.

• Tunnel and Underground Space
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• v.23 no.2
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• pp.110-119
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• 2013

It is generalized to measure the arch settlement and convergence during tunnel construction for monitoring its mechanical stability. The initial convergence rate a day is defined from the first convergence measurement and the final convergence defined as the convergence measured lastly. The initial and the final tunnel arch settlement are defined like the preceding convergence. In the study, the relations between the initial and final displacements of a shallow tunnel are analyzed. The measurements were performed in the tunnel of subway 906 construction site in Seoul. The overburden is 10-20 m and the tunnel goes through weathered soil/rock. The width and height of the tunnel are about 11.5 m, 10m, respectively. So this is a shallow tunnel in weak rock. The length of tunnel is about 1,820 m and the tunnel was constructed in 2 stages, dividing upper and lower half. The numbers of measurement locations of arch settlement and convergence are 184 and 258, respectively. As a result, the initial displacement rate and the final displacement are comparatively larger in the section of weathered soil.

• Geomechanics and Engineering
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• v.36 no.6
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• pp.575-587
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• 2024

The contact pressure between the surrounding rock and the support is an important indicator of the surrounding rock pressure. There has been a bottleneck in the prediction of contact loads between surrounding rock and primary support in deep-buried mountain tunnels. The main reason is that a reliable method wasn't existed to quantify the contact loads. This study had been taken into account the flexible support role of the primary support, and the fitting curve of surrounding rock deformation for dynamic tunnel construction was proposed. New formulas for the calculation of contact loads between surrounding rock and primary support were obtained by inversion. Comparative analysis of the calculation results with numerical simulation verified the reliability of the calculation method in this study. It can be seen from the analyses that the contact load between surrounding rock and primary support increases, remains unchanged and decreases during acceleration, uniform velocity and deceleration, respectively, and the deformation of the surrounding rock in the acceleration and deceleration stages cannot completely converted into contact loads. The contact loads between surrounding rock and primary support of medium-strength and weak surrounding rock tunnels are generally within 150 kPa and 1 MPa, respectively. For tunnels with weak surrounding rock, advanced support can be installed to reduce the unique release coefficient λ₀ and the value of the constant D, with the purpose of reducing the contact loads between surrounding rock and primary support. Changes in support parameters have a small effect on the contact loads between surrounding rock and primary support, but increase or decrease the safety factor, resulting in a waste of resources or a situation that threatens the safety of the support. The results of this research provide guidance for the prediction of contact loads between surrounding rock and primary support for dynamic tunnel construction.

• Tunnel and Underground Space
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• v.11 no.2
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• pp.96-108
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• 2001

A concrete lining of NATM tunnel is the final product of a process that involves planning and evaluation of user needs, geotechnical investigations, analysis of ground-lining interaction, construction, and observations and modifications during construction. The designer must consider the lining in context of the many function, construction, and geotechnical requirements. Also, the loss of supporting capacity of shotcrete lining due to poor rock qualities and shotcrete erosion must be considered. The values, shapes, and estimating methods of rock load and water pressure are very different with every designers. Estimating methods of rock loads used in the design of NATM tunnel concrete lining are investigated. Structural analyses are done in various load combinations, and the member forces(moment, axial force and shear force) are compared. The adequate load combination of rock load and water pressure is proposed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.41-49
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• 2000

Rock Mass Rating has been widely applied to the underground tunnel excavation and many other practical problems in rock engineering. However, Rock Mass Rating is hard, even by the experts of tunnel assessment owing to lack of investigation system. In this study, using multivariate analysis we presented rock mass rating system that is objective and easy to use. The constituents of RMR are decided to RQD, condition of discontinuities, groundwater conditions, intact rock strength, orientation of discontinuities, spacing of discontinuities in important order. In each step, we proposed the best multiple regression model for RMR system.