• Tunnel and Underground Space
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• v.10 no.4
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• pp.544-552
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• 2000

Norway has the geological of condition of hard bedrocks, high mountains, deep valleys and fjords. In this background many tunnels and rock caverns are developed. In this process of constructing tunnels and rock caverns Norway seems to have strong competitiveness in the construction of tunnels. In spite of high salaries to the tunnel workers, Norwegian contractors are probably producing the cheapest tunnels and rock caverns in the world. Besides benefit of hard-rock geology, Norwegian cost-saying is owing to the Norwegian excavation technique in hard rocks such as unlined pressure tunnels, air cushion chambers, underwater piercing, and reasonable contract system and organization of workers developed from the accumulated experience. Brief analytical description of them are given in this paper in order to stimulate the utilization of the underground spaces.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.62-69
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• 2004

The objective of this study is to estimate the distribution of a zone disturbed by excavation (EDZ) around tunnels that have been excavated at about 500 m depth in pre-Tertiary hard sedimentary rock. One of the most important tasks is to evaluate changes in the dynamic stability and permeability of the rock around the tunnels, by investigating the properties of the rock after the excavation. We performed resistivity and acoustic tomography using two boreholes, 5 m in length, drilled horizontally from the wall of a tunnel in pre-Tertiary hard conglomerate. By these methods, we detected a low-resistivity and low-velocity zone 1 m in thickness around the wall of the tunnel. The resulting profiles were verified by permeability and evaporation tests performed at the same boreholes. This anomalous zone matched a high-permeability zone caused by open fractures. Next, we performed resistivity monitoring along annular survey lines in a tunnel excavated in pre-Tertiary hard shale by a tunnel-boring machine (TBM). We detected anomalous zones in 2D resistivity profiles surrounding the tunnel. A low-resistivity zone 1 m in thickness was detected around the tunnel when one year had passed after the excavation. However, two years later, the resistivity around the tunnel had increased in a portion, about 30 cm in thickness, of this zone. To investigate this change, we studied the relationship between groundwater flow from the surroundings and evaporation from the wall around the tunnel. These features were verified by the relationship between the resistivity and porosity of rocks obtained by laboratory tests on core samples. Furthermore, the profiles matched well with highly permeable zones detected by permeability and evaporation tests at a horizontal borehole drilled near the survey line. We conclude that the anomalous zones in these profiles indicate the EDZ around the tunnel.

• Explosives and Blasting
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• v.8 no.2
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• pp.3-17
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• 1990

The Caustious blasting have often increased Complaints of ground Vibration and Sound when the Wire-Tunnel Constructed in Pusan. In order to prevent the influence to housing structure, it was necessary to predict blasting-Induced Vibration and Sound. The Suveyer determined the Burden and spacing of Drill holes, minimum delay charges within a allowable Vibration and Sound Level. Tunnel drilling and Ignition patterns are made as follows; No. 1 Tunel (Stable rock, hard rock) No.2 Tunnel (Instable plastic rock; wethered rock) and other Tunnels (Instable rock). The result of 1st testing blasting of No. 1 Tunnel was recorded Under allowable Vibration Level but sound was over 75 Db of allowable value. So Tunnel drilling pattern was amended with 52 Non-charg holes to reduce the blast-sound. The other pattern had no need to amend.

• Tunnel and Underground Space
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• v.6 no.4
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• pp.298-305
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• 1996

Grouting technique is frequently used where a tunnel structure is passing through the shallow overburden area or where the thickness of hard rock above the tunnel is rather thin. However, engineering background on design process of the grout reinforcement does not seem to be fully understood until now. Mechanics of composite material is, therefore, introduced in this study to investigate the orthotropic material properties of the composites containing soil(or rock) and grouting material. These orthotropic material properties can be used to represent the reinfocement effects quantitatively. The model developed in this study is next applied to a typical tunnel structure and the grouting effect is analyzed numerically. The idea used in this study can be expanded to a situation where a pipe roofing or a forepoling technique is adopted and a simplified design procedure, similar to the model model introduced in this study, can be developed.

• Tunnel and Underground Space
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• v.1
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• pp.66-74
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• 1991

The block theory with stereographic projection was applied and analyzed on the tunnel section of Samcheok Coal Mine. The results were as follows ; 1) Prevail orientations of discontinuity of sandstone around the main driftway of Samcheok Coal Mine were $(327^{\circ},\;44^{\circ}),\;(13^{\circ},\;24^{\circ}),\;(204^{\circ},\;65^{\circ})$ and $(225^{\circ},\;77^{\circ})$ in dip and dip direction, respectively. 2) Movable blocks of the site were 0110, 0111, 1110(roof), 0100, 0110, 1110(right wall) and 0001, 1001, 1011(left wall). Because of the direction of tunnel, blocks of the left wall was safe. thus key blocks were those of the roof and the right wall. Maximum height of key block was larger than the width of the tunnel but 2m of the yielded zone is expected in general for 5m width tunnel. 3) It is shown that block theory is applicable to large cavern in hard rock analysis.

• Tunnel and Underground Space
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• v.12 no.2
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• pp.115-119
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• 2002

Four tunnels have been planned to operate a large diameter shielded TBM in Gwangju urban subway construction site. No.1 tunnel has completely been excavated for 13 months operating. Net penetration rate and its relations with thrust farce of the shielded TBM are analysis in this report. This shallow depth tunnel of 536m length is located in soil layers at launching and in hard rocks at ending with 84 m length. The weekly net penetration rates haute dropped down as low as 20∼110 mm/hr in rock while 400∼800 mm/hr in soil. The actual penetration rates we proved to be high as the theoretical penetration rate which is analysis in consideration of conditions of machine and rock. And net penetration rate is investigated to increase linearly thrust force.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.222-229
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• 2022

Although stochastic programming and feedback control approaches could efficiently mitigate the overdue risks caused by inherent uncertainties in ground conditions, the lack of formal representations of planners' rationales for resource allocation still prevents planners from applying these approaches due to the inability to consider comprehensive resource allocation policies for hard rock tunnel projects. To overcome the limitations, the authors developed an ontology that represents the project duration estimation rationales, considering the impacts of ground conditions, excavation methods, project states, resources (i.e., given equipment fleet), and resource allocation policies (RAPs). This ontology consists of 5 main classes with 22 subclasses. It enables planners to explicitly and comprehensively represent the necessary information to rapidly and consistently estimate the excavation durations during construction. 10 rule sets (i.e., policies) are considered and categorized into two types: non-progress-related and progress-related policies. In order to provide simplified information about the remaining durations of phases for progress-related policies, the ontology also represents encoding principles. The estimation of excavation schedules is carried out based on a hypothetical example considering two types of policies. The estimation results reveal the feasibility, potential for flexibility, and comprehensiveness of the developed ontology. Further research to improve the duration estimation methodology is warranted.

• Geomechanics and Engineering
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• v.24 no.6
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• pp.505-518
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• 2021

The present paper has been carried out to understand the effects of impact loading on the rock tunnels, constructed in different region corresponding to varying unconfined compressive strength (UCS), through finite element method. The UCS of rockmass has substantial role in the stability of rock tunnels under impact loading condition due to falling rocks or other objects. In the present study, Dolomite, Shale, Sandstone, Granite, Basalt, and Quartzite rocks have been taken into consideration for understanding of the effect of UCS that vary from 2.85 MPa to 207.03 MPa. The Mohr-Coulomb constitutive model has been considered in the present study for the nonlinear elastoplastic analysis for all the rocks surrounding the tunnel opening. The geometry and boundary conditions of the model remains constant throughout the analysis and missile has 100 kg of weight. The general hard contact has been assigned to incorporate the interaction between different parts of the model. The present study focuses on studying the deformations in the rock tunnel caused by impacting load due to missile for tunnels having different concrete grade, and steel grade. The broader range of rock strength depicts the strong relationship between the UCS of rock and the extent of damage produced under different impact loading conditions. The energy released during an impact loading simulation shows the variation of safety and serviceability of the rock tunnel.

• Tunnel and Underground Space
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• v.4 no.1
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• pp.24-30
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• 1994

Although a dry-system tunnel is not good for reasons fo economy and construction, it has been applied to some tunnels under construction owing to the advantages of good long-term maintenance of tunnel, prevention of consolidation settlement due to the drawdown of groundwater, preservation of the ecosystem, cutailment of operation cost, and so on. The stability of groundwater and the change of the applied water pressure after water proofing were analysed by the finite element method. Using this result, an example of designing the secondary lining for the dry-system tunnel which is to be constructed in low-permeability hard rock was presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.584-590
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• 2009

One of the critical design problems involved in deep tunnelling in brittle rock, is the creation of surface spalling damage and breakouts. If weak fault zone is developed in deep tunnel, squeezing problem is added to the problems. According to the results of ground investigation in the study area, hard granitic rockmass and distinguished high angle fault zone are distributed on the tunnel level over 400m depth. To analyse the probability of brittle failure and squeezing, ground characterization with special lab. and field test were carried out. By the results, probability of brittle failures like spalling and rock burst is very low. But squeezing may be probable, if weak fault zone observed surface and drill core is extended to designed tunnel level.