• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.101-111
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• 2002

The purpose of this research is to develop improved model for joints of tunnel based on Disturbed State Concept (DSC) model. DSC model is verified with respect to comprehensive laboratory tests performed by Schneider and back prediction results. Based on results of this research, it can be stated that DSC model is capable of characterizing the strain softening and dilative behavior of rough granite joints under four different constant normal stresses.

• Tunnel and Underground Space
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• v.18 no.5
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• pp.338-342
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• 2008

Longitudinal deformation profile(LDP) has been obtained mostly by numerical analysis. In this study, LDP was plotted by measured data from horizontal inclinometer and crown settlement. Deformation of foe ahead was determined by comparing to the maximum deformation point and deformation of after excavation was determined by regression of the measured crown settlement data. The result shows that crown deformation began as f3r as 3D ahead of the face. Crown settlement at the face was 40% of ultimate deformation, which was 10% higher than numerical results, and the deformation converged after excavation of 4D.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.149-157
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• 1999

A powerful numerical method that can be used for that purpose is the Discontinuous Deformation Analysis (DDA) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the DDA method have been proposed in the literature, the method is not capable of modeling water-block interaction that is needed when modeling surface or underground excavation in fractured rock. This paper presents a new extension to the DDA method. The extension consists of hydro-mechanical coupling between rock blocks and water flow in fractures. A example of application of the DDA method with the new extension is presented. The results of the present study indicate that fracture flow could have a destabilizing effect on the tunnel stability.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.309-320
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• 2012

Dynamic behaviors of the tunnel linings of curved tunnels with various curvatures are investigated to examine the effect of wind loads due to passing vehicles. In the case without backfill, the responses of the tunnel lining should be considered to examine the clearance of the lining. A steel tunnel lining is selected to see the influence of the wind load upon the tunnel lining more clearly. The wind pressure upon the lining is simplified into the pressure and suction while the vehicle passing the loading positions. As the radius of curvature decreases, the response decreases, showing that the strength against the deformation is found to increase since the asymmetry of the deformation shape is reduced. It is found that the responses increase as the passing vehicle speed increases.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4D
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• pp.555-561
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• 2009

In lieu of section profile data, a fitting of the bored tunnel shape is more significant confirmation for maintenance of a tunnel. Before the permit on the completion of a tunnel, deformation of the completed tunnel with respect to the design model are considered. And deformation can be produced at continuously along the entire of the tunnel section. This study firstly includes an analysis of algebraic approach and test it with an observed field data. And then a number of methods, line search method, genetic algorithm, and pattern search methods, are compared with the 3D tunnel shape fitting. Algebraic methods can solve a simple circular cylinder type as like a railway tunnel. However, a more complex model (compound circular curve and non circular) as like a highway tunnel has to be solved with soft computing tools in the cause of conditional constraints. The genetic algorithm and pattern search methods are computationally more intensive, but they are more flexible at a complex condition. The line search method is fastest, but it needs a narrow bounds of the initial values.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.25-32
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• 2000

This paper presents two new extensions to the DDA method. The extensions consist of sequential loading or unloading and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the DDA method with the new extensions are presented. Simulations of the underground excavation of the Unju Tunnel of Kyungbu High Speed Railway Project in Korea were carried out to evaluate the influence of excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the DDA program with the three new extensions can now be used as d practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.

• Journal of the Korean Geotechnical Society
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• v.31 no.10
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• pp.29-36
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• 2015

This paper deals with inspecting and monitoring cracks developed on a subway tunnel liner during the construction of temporary supports and excavation. The cracks have developed near a enlarged part of the tunnel. Several measurements, crack gauge, internal displacement measurement, 3-D laser scanner have been conducted to monitor the progress of cracks and effects of them on the tunnel. Local measurement, additional propagation of cracks and deformation of liner, have been conducted by crack gauge and internal displacement measurement. Global inspection has been conducted by 3-D laser scanner. From the scanned data, occurrence of global deformation of tunnel and rail has been evaluated. Because of limited sequence of construction at the ground, no apparent deformation of crack propagation has been measured. As presented in this paper, deformation of tunnel liner and effects of rail need to be investigated in view of local and global aspects.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.5
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• pp.761-778
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• 2017

The need of the underground space for the infrastructures in urban area is increasing, and especially the demand for shallow tunnels increased drastically. It is very important that the shallow tunnel in the urban area should fulfill not only its own safety conditions but also the safety condition for the adjacent structures and the surrounding sub-structure. Most of the studies on the behavior of shallow tunnels concentrated only on their behaviors due to the local deformation of the tunnel, such as tunnel crown or tunnel sidewall. However, few studies have been performed for the behavior of the shallow tunnel due to the deformation of the entire tunnel. Therefore, in this study the behavior of the surrounding ground and the stability caused by deformation of the whole tunnel were studied. For that purpose, model tests were performed for the various ground surface slopes and the cover depth of the tunnel. The model tunnel (width 300 mm, height 200 mm) could be simulationally deformed in the vertical and horizontal direction. The model ground was built by using carbon rods of three types (4 mm, 6 mm, 8 mm), in various surface slopes and cover depth of the tunnel. The subsidence of ground surface, the load on the tunnel crown and the sidewall, and the transferred load near tunnel were measured. As results, the ground surface subsided above the tunnel, and its amount decreased as the distance from the tunnel increased. The influence of a tunnel ceased in a certain distance from the tunnel. At the inclined ground surface, the wider subsidence has been occurred. The loads on the crown and the sidewall were clearly visible, but there was no effect of the surface slope at a certain depth. The load transfer on the adjacent ground was larger when the cover depth (on the horizontal surface) was lager. The higher the level (on the inclined surface), the wider and smaller it appeared. On the shallow tunnel under inclined surface, the transfer of the ambient load on the tunnel sidewall (low side) was clearly visible.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.3
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• pp.319-329
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• 2016

Underground structures such as subsea tunnel having large section should be stable against seismic loads. In general, underground structures show more stable behavior due to the limited dynamic motion and force, and considerable energy dissipation; however, severe damage was reported from recent earthquakes. Therefore, more sophisticated and analytic approach is required to investigate the seismic response of underground structure like subsea tunnel. In this study, seismic analysis of virtual Honam-Jeju subsea tunnel are performed. Consequently, stresses and forces of tunnel lining increased at fractured and/or weak rock zones. Stresses and forces of tunnel lining also increased at large section under axially deformed condition; however, decrease under transversely deformed condition.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.5
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• pp.523-536
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• 2013

In order to ensure the safety of the subsea tunnel during its construction and operation, unlike the underground structures on land, the special monitoring system is essential which considers the characteristics of subsea tunnels in addition to conventional stress and displacement measurements applied to existing land tunnels. Therefore, the concept applied to NATM is reorganized to evaluate the stability of subsea tunnels. And the observation system for making a monitoring plan, the critical strain theory for tunnel safety management and MS monitoring methods for detecting the local failure and crack initiation of rock and supports, are introduced. Finally, the scheme of monitoring and management for subsea tunnels by using these methods is suggested.