• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.83-96
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• 2011

Currently, the commonly used tunneling method in Korea is NATM (New Austrian Tunneling Method). This method uses the rock bolt, shotcrete, and supporting system to maintain the strength of original soil and ensures the stability of tunnel by stabilizing the soil using the original strength of the soil in maximum after the excavation. In past years, wire-mesh reinforced shotcrete was common ones but currently steel-fiber reinforced shotcrete is being widely used for the tunnel construction site in Korea to save construction time with the advanced construction technology. The results further indicate that needs for the establishment of not only the specifications for shotcrete but the strengthening methods for the under reinforced shotcrete sections. Therefore, this study deals with the development of a new steel-fiber to ensure the stability of tunnels that are under reinforced with steel-fibers and to overcome the shortcomings of conventional method.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.267-278
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• 2003

Artificial neural networks are efficient computing techniques that are widely used to solve complex problems in many fields. In this study, in order to predict tunnel-induced ground movements, Tunnel Behavior Prediction System (TBPS) was developed by using these artificial neural networks model, based on a Held instrumentation database (i.e. crown settlement, convergence, axial force of rock bolt, compressive and shear stress of shotcrete, stress of concrete lining etc.) obtained from 193 location data of 31 different tunnel sites where works are completed. The study and test of the network were performed by Back Propagation Algorithm which is known as a systematic technique for studying the multi-layer artificial neural network. The tunnel behaviors predicted by TBPS were compared with monitored data in the tunnel sites and numerical analysis results. This study showed that the values obtained from TBPS were within allowable limits. It is concluded that this system can effectively estimate the tunnel ground movements and can also be used f3r tunneling feasibility study, and basic and detailed design and construction of tunnel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1461-1468
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• 2015

Mostly mine support(Rock bolt and Support) which is currently general for reinforcements of a large scale tunnel is applied, Some executing a reinforcement to Poor ground by cast-in-place shotcrete. However On domestic mine conditions that couldn't having every time after mine tunnel excavation, it couldn't ensure the field batch plant which is a fixed in an issue of economies and site security, constructing it by supply gets from shotcrete materials combined in neighborhood ready mixed concrete manufacturing plants. carried shotcrete in ready mixed concrete manufacturing plants as migration length and time are falling off in quality. But, it is difficult for construction quality control By quality control arbitrariness absence at on-scene. In the present study, carry out Laboratory Test by kinds and percentages of accelerating agent for evalution of Mechanical Property and Durability of Shotcrete.

• Geomechanics and Engineering
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• v.27 no.6
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• pp.537-550
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• 2021

There are various technical problems need to be solved in the construction process of pre-setting an isolation wall into a double lane in the outburst prone mine. This study presents a methodology that pre-setting an isolation wall into a double lane without a coal pillar. This requires the excavation of two small section roadways to dig a wide section roadway, followed by construction of the separation wall. During this process the connecting lane is reserved. In order to ensure the stability of the separation wall, the required bearing capacity of the isolation wall is 4.66 MN/m and the deformation of the isolation wall is approximately 25 cm. To reduce the difficulty of implementing support the roadway is driven by 5 m/d. After the construction of the separation wall, the left side coal wall is brushed 1.5 m to make the width of the gas roadway reach 2.5 m and the roadway support utilizes anchor rod, ladder beam, anchor cable beam and net configuration. During construction, the concrete pump and removable self-propelled hydraulic wall mold are used to pump and pour the concrete of the isolation wall. In the process of mining, the stress distribution of coal body and isolation wall is detected and measured on site. The results demonstrate that the deformation of the surrounding rock of roadway and separation of roof in the roadway is small. The stress of the bolt and anchor cable is within equipment tolerance validating their selection. The roadway is well supported and the intended goal is achieved. The methodology can be used for reference for similar mine gas control.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.1
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• pp.1-11
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• 2023

In this study, the stability of the room-and-pillar underground method was investigated using numerical analysis method. In-situ geotechnical investigation was conducted, and a supporting pattern was selected based on the geotechnical investigation data. For the supporting pattern, Type-1, 2, 3 were selected for each ground condition. A 3D numerical analysis model was developed for effective simulation as the room-and-pillar underground method consist of a pillar and room. As a review of numerical analysis, it was confirmed that the crown settlement, convergence, shotcrete and rock bolt were all stable in all supporting patterns. As a result of the analysis by the construction stage, it was confirmed that excessive stress was generated in the room when the construction stage of forming pillar. So, precise construction is required during the actual construction stage of the pillar formation.

• Journal of KIBIM
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• v.13 no.3
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• pp.1-11
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• 2023

In order to use BIM as a tool for improving the productivity and quality of products in the construction industry, a BIM model must be created from the design stage first. Infrastructure structures such as bridges and tunnels are mainly created based on three-dimensional alignment in the generation of BIM models. Especially, generation of BIM models based on three-dimensional linearity has high task difficulty and algorithms for automating BIM modeling for railway infra structures have been suggested in previous studies. This study improved the BIM modeling automation algorithm of railway infrastructures and developed a system based on the algorithm so that it can be easily used by ordinary users. The system was built as an add-in system of Autodesk's Revit. As an improvement first, it is possible to arrange different libraries for each pattern, enabling various uses. In addition, it can be created models of several members with a single process and the system can automatically places structures that are added periodically, such as Rock Bolt and Fore Polling. Finally, 3D length information and volume for each pattern are automatically calculated for more accurate 3D-based volume calculation. This study contributes to increasing user accessibility by building a BIM modeling automation algorithm into a system. The system is expected to improve the efficiency of BIM modeling creation of linear-based infra structures, including railway infrastructure.

• Journal of the Korean Geosynthetics Society
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• v.15 no.2
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• pp.55-64
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• 2016

The construction of the road NATM tunnel, which undergoes the weathered zone of the mountain, was in process with the reinforcement methods such as the rock bolt, shotcrete depositing, and the multi step grout with large diameter steel pipe. The collapse from the ceiling, and on the ground surface area(sink hole), of which were measured to be 25m from the ground surface($V=12m(W){\times}14m(L){\times}5m(H)=840m^3$), as well as excessive displacements in the tunnel, had occurred. In order to execute the necessary reconstruction work, the causes of the surface collapses were inspected through the field investigation, in-situ tests, and numerical analysis. As a result, several proper solutions were suggested for both internal and external reinforcements for the tunnel. As a result of numerical analysis, the collapsed zone of the tunnel was reinforced up to 0.5D~1.0D laterally by the cement grouting on the ground surface, 0.5D longitudinally by the multi step grout with large diameter steel pipe in tunnel. With further reinforcement implemented by rebars in lining, the forward horizontal boring was executed to the rest of the tunnel to evaluate the overall status of the tunnel face. Appropriate reinforcement methods were provided if needed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.1
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• pp.3-12
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• 2006

The purpose of this study is to describe the Non-Destructive Testing(NDT) of the rockbolt and investigate the applicability of the NDT methods to estimate the integrity of the rockbolt. To examine the rockbolt integrity including rockbolt itself and grouting material, two methods are adopted: numerical and experimental methods. In the numerical method, the numerical code DISPERSE is used to analyze the dispersion of the rockbolt. The dispersion curve shows the effects of the thickness and stiffness of grouted materials on the embedded rockbolt. Therefore, the optimal frequency for the integrity test of the rockbolt is obtained: 20~120kHz in L(1,0) mode. In the experimental methods, destructive and non-destructive tests are carried out in a laboratory. In the non-destructive test, the low frequency mode generated by an impact and t he high frequency mode generated by an ultrasonic transducer seem to characterize the rockbolt condition readily. The experimental results show that the guided waves attenuate more significantly when the stiffness of the grouted material increases and/or the zone of the defect increases. Meanwhile, the ultimate capacity of rockbolt was evaluated through the pull-out tests and is compared to the NDT results. This study demonstrates that the NDT is a valuable tool for the rockbolt integrity evaluation.

• Journal of the Korean Geotechnical Society
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• v.37 no.8
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• pp.25-35
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• 2021

Recently, the ground anchor method is commonly applied with nail and rock bolt to secure the stability of slopes and structures in Korea. Among them, permanent anchor which is used for long-term stability should secure bearing capacity and durability during the period of use. However, according to recent studies, phenomenon such as deformation to slope and the reduction of residual tensile load over time have been reported along the long-term behavior of the anchors. These problems of reducing residual tensile load are expected to increase in the future, which will inevitably lead to problems such as increasing maintenance costs. In this study, we identified the factors that affect the tensile load of permanent anchor from a literature study on the domestic and foreign, and investigated the prior studies that analyzed previously conducted load cell monitoring data. Afterwards, using this as basic data, the load cell measurement data collected at the actual site were analyzed to identify the tensile load reduction status of anchors, and the long-term load reduction characteristics were analyzed. Finally, by aggregating the preceding results, proposed a technique to predict the long-term load reduction characteristics of permanent anchors through short-term data to around 100 days after installation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.3
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• pp.223-242
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• 2024

Single-shell tunnels, introduced to South Korea in the early 2000s, have not been adopted for the main tunnels of roads or railways over the past two decades despite several attempts starting with the Gwangju City Bypass. This reluctance likely arises from concerns about the long-term performance of supporting materials and the absence of relevant criteria and specifications. However, recent progress, including the incorporation of high-strength shotcrete standards and corrosion-resistant rock bolt specifications, alongside equipment and technique enhancements, necessitates a reassessment of single-shell tunnels. While the single-shell tunnel method offers advantages in environmental impact, construction cost and period compared to the conventional NATM, it is crucial to address the challenges, such as limited design and construction experience, incomplete detailed standards, and insufficient construction specifications, through further research and pilot projects. This paper reviewed the basic principles of single-shell tunnel, current application and research status, technical development trends, criteria and specifications, and remaining challenges. It aims to reignite discussions on the feasibility of applying single-shell tunnels in South Korea.