• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.3
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• pp.183-197
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• 2004

The introduction of geodetic methods of absolute displacement monitoring in tunnels has significantly improved the value of the measurements. Structurally controlled behavior and influences of an anisotropic rock mass can be determined, and the excavation and support adjusted accordingly. Three-dimensional finite element simulations of different weakness zone properties, thicknesses, and orientations relative to the tunnel axis were carried out and the function parameters were evaluated from the results. The results were compared to monitoring results from Alpine tunnels in heterogeneous rock. The good qualitative correlation between trends observed on site and numerical results gives hope that by a routine determination of the function parameters during excavation the prediction of rock mass conditions ahead of the tunnel face can be improved. Implementing the rules developed from experience and simulations into the monitoring data evaluation program allows to automatically issuing information on the expected rock mass quality ahead of the tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.229-240
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• 2007

The 3D absolute displacement monitoring system has been developed to analyze the tunnel convergence measured under construction of underground structures and to manage effectively the measured data. The system is comprised of the total station, the anchor-typed target pin and the 3D absolute displacement measurement and management program. In this paper, the types and specifications of the 3D total station were presented. The anchor-typed target pin, an improved model of traditional one, was developed and its sightable distance and measurement accuracy were checked by field tests. Also a 3D absolute displacement measurement and management program, TEMS 3D, was developed to provide some analysis tools including the trend and influence lines. L/C ratio, S/C ratio and the like. The developed system was applied the construction stage of a railway tunnel for testing purpose. It is verified that the developed system is capable of predicting weak zones ahead of tunnel face by comparing with results of TSP (Tunnel Seismic Prediction) survey.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.04a
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• pp.47-60
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• 1998

It is considered in this paper that the main causes of tunnel collapse during the construction were the insufficiency of data of geotechnical investigations, or their limits due to special ground condition such as its heterogeneity and anisotropy It is thought that safety of ground can be affected by the geological conditions such as presences of discontinuities in good intact rocks, and considered to be necessary that awareness of the conditions of discontinuities in advance is important to apply adequate reinforcement measures. It is also shown that a serious accident had occurred because of the unawareness of the permeable alluvial deposits at the top of the tunnel. And it is shown that the example of application of the results of geotechnical investigation such as face-mapping, pilot boring etc. during tunnel construction, and a serious deformation of tunnel under special geological condition. Therefore, it is strongly recommended to perform an adequate geotechnical investigation to confirm the geotechnical conditons of ground before design, and supplimentary investigation is also needed depending on conditions for safe and econonic construction.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2003.03a
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• pp.13-30
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• 2003

In this paper, a new systematic method will be introduced, in which a Rock-mass Prediction System(RPS) predicts the geological conditions and rock mass movements before tunnel excavation and the appropriate counter-measures are taken in the expected weak zones during tunnel construction. The Rock-mass Prediction System(RPS) consists of the LIM, a horizontal core drilling and a seismic exploration method(TSP/HSP). In the Rock-mass Prediction System(RPS), the seismic exploration method (TSP/HSP) gives information on the locations of the weak zones such as major faults and voids in wide-range, and the horizontal core drillings are utilized to find exact location and widths of the faults or voids near the weak zones which was predicted by the seismic exploration method (TSP/HSP). The LIM is used to find the hardness of the rock mass and small weak zones near the excavation face. The Rock-mass Prediction System (RPS) was successfully applied to the Sol-An Tunnel and the effectiveness of the system was verified.

• Tunnel and Underground Space
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• v.34 no.2
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• pp.143-153
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• 2024

Tunnel Boring Machine (TBM) method is a tunnel excavation method that produces lower levels of noise and vibration during excavation compared to drilling and blasting methods, and it offers higher stability. It is increasingly being applied to tunnel projects worldwide. The disc cutter is an excavation tool mounted on the cutterhead of a TBM, which constantly interacts with the ground at the tunnel face, inevitably leading to wear. In this study quantitatively predicted disc cutter wear using geological conditions, TBM operational parameters, and machine learning algorithms. Among the input variables for predicting disc cutter wear, the Uniaxial Compressive Strength (UCS) is considerably limited compared to machine and wear data, so the UCS estimation for the entire section was first conducted using TBM machine data, and then the prediction of the Coefficient of Wearing rate(CW) was performed with the completed data. Comparing the performance of CW prediction models, the XGBoost model showed the highest performance, and SHapley Additive exPlanation (SHAP) analysis was conducted to interpret the complex prediction model.

• Tunnel and Underground Space
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• v.6 no.2
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• pp.166-174
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• 1996

Stability of rock slope is greatly affected by the geometry and strength of discontinuities developed in the rock mass. In this study an analytical method which is capable of analyzing the effect of relative orientation between the discontinuities and the slope face on the safety of slope by assessing their vector components was used to evaluate the stability and the maximum cut-angle for the proposed slope design. The results of computerized vector analysis revealed that slope area under investigation might be divided into 3 sections of different face directions. The safety factors for benches in each 3 sections were calculated using the limit-equilibrium theory. Then, by utilizing the concept of probabilistic risk analysis, the susceptibility of entire slope failure was estimated. Based on the distribution of safety factor in each bench, the maximum cut angle of each section could be selected differently ot achieve the permanent stability of the entire slope.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.165-172
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• 2001

본 연구에서는 하천인접구간에서와 같이 지하수가 풍부한 지반에서 시공되는 터널의 막장 안정성을 평가하기 위하여 터널 막장에 작용하는 힘의 두 가지 요소를 고려하였다. 하나는 극한해석 중 upper bound solution으로부터 산출된 유효응력이며, 또 하나는 지하수의 정상류 흐름조건을 고려한 수치해석으로부터 산출된 침투력이다. 지하수가 풍부한 토사지반에서의 터널 시공시 터널 막장에 작용하는 힘을 구하기 위하여 침투력을 고려한 극한해석의 해를 구한 결과 터널 막장의 안정성을 유지하기 위한 최소 지보력은 터널 막장에 작용하는 유효응력과 침투력의 합으로 나타낼 수 있었다. 또한 터널 막장에 작용하는 평균침투압은 지하수위에 비례하여 작용하는 것으로 나타났으며, 이를 실내모형 실험 결과를 통하여 검증하였다. 지하수의 정상류 조건 하에서의 토사터널에 대한 실내모형 실험 결과, 터널 막장에 작용하는 침투력은 수치해석 결과 비슷한 양상을 보여주어 제안된 이론의 타당성을 입증하였다.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.329-343
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• 2000

Rock joint survey consists of measurement of orientation and face mapping for trace informations. We have developed a new alternative approach called rock joint survey system by stereophotogrammetry and image processing to replace the conventional manual method. For the measurement of orientations and face mapping, we applied a stereophotogrammetry and developed two hybrid approaches using image processing techniques, respectively. These methods have advantages in making it possible to measure the orientations of joints and perform face mapping rapidly and objectively in unaccessible and dangerous areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.785-791
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• 2023

Risk management is essential for preventing accidents arising from uncertainties in TBM tunnel projects, especially concerning managing the risk of TBM tunnel collapse, which can cause extensive damage from the tunnel face to the ground surface. In addition, prioritizing risks is necessary to allocate resources efficiently within time and cost constraints. Therefore, this study aimed to establish a TBM risk database through case studies of TBM accidents and determine a risk priority for TBM tunnel collapse using the Bayes theorem. The database consisted of 87 cases, dealing with three accidents and five geological sources. Applying the Bayes theorem to the database, it was found that fault zones and weak ground significantly increased the probability of tunnel collapse, while the other sources showed low correlations with collapse. Therefore, the risk priority for TBM tunnel collapse, considering geological sources, is as follows: 1) Fault zone, 2) Weak ground, 3) Mixed ground, 4) High in-situ stress, and 5) Expansive ground. In practice, the derived risk priority can serve as a valuable reference for risk management, enhancing the safety and efficiency of TBM construction. It provides guidance for developing appropriate countermeasure plans and allocating resources effectively to mitigate the risk of TBM tunnel collapse.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.51-56
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• 1993

This paper presents the FEM anlysis results performed to assess the applicability of Horizontal Jet Grout Roofing, and of ground improvement methods for tunneling in soft ground. Horizontal Jet Grount Roofing Method is applicable to ensure the stability of tunnel face in non-cemeted alluvial strata under high ground water pressure. For applying this method, to ensure the reliability, the Horizontel Jet Grout Roofing should be double lined with pre-grouting to reduce the water inflow during the jet grouting.