• The Journal of Engineering Geology
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• v.19 no.4
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• pp.483-492
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• 2009

During construction of a tunnel and underground structure, it is very important to acquire accurate information of the rock mass will be excavated. In this study, the drill monitoring method was applied for rapid prediction of geological condition ahead of the tunnel face. Mechanical data(speed, torque and feed pressure) from drilling process using a hydraulic drilling machine were analyzed to assess rock mass characteristics. Rock mass information acquired during excavation from drilling monitoring were compared with results from horizontal boring and tunnel seismic profiling(TSP). As the result, the drilling monitoring method is useful to assess rock mass condition such as geological structures and physical properties ahead of the tunnel face.

• Geomechanics and Engineering
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• v.23 no.5
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• pp.441-454
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• 2020

The tunnel collapse, large deformation of surrounding rock, water and mud inrush are the major geological disasters in soft rock tunnel construction. Among them, tunnel collapse has the most serious impact on tunnel construction. Current research backed theories have certain limitations in identifying the collapse risk of soft rock tunnels. Examining the Zhengwan high-speed railway tunnel, eight soft rock tunnel collapse influencing factors were selected, and the combination of indicator weights based on the analytic hierarchy process and entropy weighting methods was obtained. The results show that the groundwater condition and the integrity of the rock mass are the main influencing factors leading to a soft rock tunnel collapse. A comprehensive fuzzy evaluation model for the collapse risk of soft rock tunnels is being proposed, and the real-time collapse risk assessment of the Zhengwan tunnel is being carried out. The results obtained via the fuzzy evaluation model agree well with the actual situation. A tunnel section evaluated to have an extremely high collapse risk and experienced a local collapse during excavation, verifying the feasibility of the collapse risk evaluation model. The collapse risk evaluation model proposed in this paper has been demonstrated to be a promising and innovative method for the evaluation of the collapse risk of soft rock tunnels, leading to safer construction.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.81-87
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• 2008

This study is about the back analysis to optimize the uncertain parameters of geotechnical properties used in stability analysis of cut and cover tunnel. The Simplex algorithm, Powell algorithm, Rosenbrock algorithm, and Levenberg-Marquardt algorithm are applied for artificial problems of ground excavation. Furthermore, results are compared in the matter of the reliability of optimal solutions with a certain accuracy and the computation speed for evaluations of variables. As shown in results of numerical analysis, all of four algorithms are converged to exact solution satisfying the allowable criteria. And Levenberg-Marquardt's and Rosenbrock's algorithms are identified to be the more efficient methods in the evaluations of functions. After the back analysis for Poisson ratio and Young's modulus for cut and cover tunnel has been performed, design parameters have been correctly estimated and computation time has been improved while the number of measure points is increased.

• Tunnel and Underground Space
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• v.17 no.3 s.68
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• pp.225-233
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• 2007

Because of Norwegian topography as valleys and fjords, a large number of tunnels has been built and 59 of them have been excavated by TBM for last 30 years. Prognosis technology has been developed and improved through lots of TBM experiences, and the NTNU prediction model has been completed. This paper focuses the improvement of net penetration rate and advance rate in 14 Norwegian and 4 Koran TBM tunnelling sites of which data were reported. Through this period, net penetration rate as well as advance rate were increased to double with the improvement of disc cutter size and cutter arrangement in Norway. These rates in Korea were also increased for 15 years even though the rates were lower compared to Norwegian. It is estimated that these low rates were mainly caused by using disc cutters less than 17 inch diameter. It is expected that net penetration rate and advance rate can be increased by improvement of machine and tunnelling technology, especially by using 17 or 19 inch of the disc cutter size in the Korean full face mechanical tunnelling site.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.192-203
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• 2009

In the new Seoul-Busan high speed railroad construction specially in area of city center passage the roadbed establishment is recommended the staibility for the existing subway tunnel segments of Busan subway 1st and 2nd lines regarding the appearance condition, a quality condition and the durability of the objective facility, and it evaluates the numerical analysis using MIDAS/GTS which leads the stability of the objective facility and investigatesd tunnels. Fundamental issues in tunneling under high groundwater table are discussed and the effect of groundwater on tunnel excavation was examined using a 3D stress-pore pressure coupled Finite-Element Method. Based on the results the interaction mechanism between the tunnelling and groundwater is identified. In the both of 1st and 2nd Line the maximum sinkage, unequal sinkage and the lining stress from numerical analysis are within permission and the damage degree is appearing to be disregarded. But it enforces necessary Pre-grouting in order to minimize an actual tunnel face conduct and when the tunnel is excavated it is also necessary to minimize the outflow possibility.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.393-402
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• 2021

The first TBM introduced in Korea was the gripper TBM, which was applied to the Gudeok Waterway Tunnel in 1985. In the initial stage of the introduction of the gripper TBM, many applications were mainly focused on waterway tunnels (Tunnel Mechanized Construction Design, 2008). Currently, the construction range of gripper TBM in Korea is widely applied to not only waterway tunnels, but also subways, railway tunnels, and TBM+NATM expansion. Overseas, gripper TBM is generally applied, and even when NATM tunnel is applied, it is applied as an exploration tunnel because of the excellent advance rate of gripper TBM and used as an evacuation tunnel after completion. Due to the fast excavation speed, the application of the gripper TBM in the rock section of weathered rock or higher can minimize the environmental and civil complaints caused by creating a large number of work areas when planning long tunnels or mountain tunnels. In this study, the work process of the general gripper TBM was analyzed by analyzing the construction cycle and the gripper TBM with a diameter of 2.6~5.0 m, which was applied the most in Korea. Downtime was investigated and analyzed.

• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.99-104
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• 2007

The deep soil mixing, on ground modification technique, has been used for many diverse applications including building and bridge foundations, port and harbor foundations, retaining structures, liquefaction mitigation, temporary support of excavation and water control. This method has the basic objective of finding the most efficient and economical method for mixing cement with soil to secure settlements through improvement of stability on soft ground. In this research, the experiments were conducted on a laboratory scale with the various test conditions of mixing method; the angle of mixing wing, mixing speed. Strength and shapes of improved soil of these test conditions of deep mixing method were analysed. From the study, it was found that the mixing conditions affect remarkably to the strength and shapes of improved soils.

• International conference on construction engineering and project management
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• 2020.12a
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• pp.463-481
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• 2020

Cutter suction dredgers (CSDs) are widely used in various dredging constructions such as channel excavation, wharf construction, and reef construction. During a CSD construction, the main operation is to control the swing speed of cutter to keep the slurry concentration in a proper range. However, the slurry concentration cannot be monitored in real-time, i.e., there is a "time-lag effect" in the log of slurry concentration, making it difficult for operators to make the optimal decision on controlling. Concerning this issue, a solution scheme that using real-time monitored indicators to predict current slurry concentration is proposed in this research. The characteristics of the CSD monitoring data are first studied, and a set of preprocessing methods are presented. Then we put forward the concept of "index class" to select the important indices. Finally, an ensemble learning algorithm is set up to fit the relationship between the slurry concentration and the indices of the index classes. In the experiment, log data over seven days of a practical dredging construction is collected. For comparison, the Deep Neural Network (DNN), Long Short Time Memory (LSTM), Support Vector Machine (SVM), Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and the Bayesian Ridge algorithm are tried. The results show that our method has the best performance with an R² of 0.886 and a mean square error (MSE) of 5.538. This research provides an effective way for real-time predicting the slurry concentration of CSDs and can help to improve the stationarity and production efficiency of dredging construction.

• Geomechanics and Engineering
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• v.37 no.1
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• pp.65-72
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• 2024

Water ingress poses a common and intricate geological hazard with profound implications for tunnel construction's speed and safety. The project's success hinges significantly on the precision of estimating water inflow during excavation, a critical factor in early-stage decision-making during conception and design. This article introduces an optimized model employing the gene expression programming (GEP) approach to forecast tunnel water inflow. The GEP model was refined by developing an equation that best aligns with predictive outcomes. The equation's outputs were compared with measured data and assessed against practical scenarios to validate its potential applicability in calculating tunnel water input. The optimized GEP model excelled in forecasting tunnel water inflow, outperforming alternative machine learning algorithms like SVR, GPR, DT, and KNN. This positions the GEP model as a leading choice for accurate and superior predictions. A state-of-the-art machine learning-based graphical user interface (GUI) was innovatively crafted for predicting and visualizing tunnel water inflow. This cutting-edge tool leverages ML algorithms, marking a substantial advancement in tunneling prediction technologies, providing accuracy and accessibility in water inflow projections.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.363-375
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• 2019

Since the double-deck tunnel is deeply constructed in the city, it is necessary to secure the installation space of air supply and exhaust, escape passage stairs, elevator, distribution facilities and connection tunnels in the vertical shaft for the double-deck tunnel. Also, in order to minimize the effect of construction on adjacent area, it is necessary to construct the concrete structures at high speed in vertical shaft after tunnel excavation. Therefore, the slabs and the stairs in vertical shaft are needed to be constructed using precast concrete, and the rapid construction techniques of bracket for supporting the inner precast structure are needed. The bracket installation methods include cast-in-place concrete, precast concrete and steel. In this study, the improvement of the steel brackets with good economical efficiency and good workability was carried out in consideration of the improvement of the construction speed. We have developed a new bracket that is optimized through bracket shape improvement, anchor bolt position adjustment and quantity optimization. As a result of the structural performance test, it was confirmed that the required load supporting capacity was secured. As a result of structural performance test for bar type anchor bolt and bent anchor anchor bolt, it was confirmed that the required load carrying capacity was secured and that the load bearing capacity of bent anchor bolt was large.