• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.117-128
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• 2005

This Paper present design parameters of grouting by reviewing several published equations and the results of coupled analysis considering the difference of permeability between soil and grouted zone. Also, the feasibility of couped analysis in the design of grouting is studied for seeping water quantity into tunnel, displacement of tunnel face, drawing down of groud water table, settlement of ground and stress of tunnel supports.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.946-951
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• 2004

ITIS is applied to the several tunnel construction sites in Korea. Tunnel construction properties which are acquired from these sites are transferred to information management server(SQL 2000 server)by client application program in real time. Access permission to DB server depends on the user's roles. Some functions which cannot be embodied in SQL Server are serviced through XML and GMS server is used for spatial data based on GIS part. This system is supposed to give engineers the advantages which are not only easy handling of the program and computerized documentation on every information during construction but also analyzing the acquired data in order to predict the structure of ground and rock mass to be excavated later and show the guideline of construction. Neung-Dong tunnel and Mu-Gua express way tunnel are now under construction and with this system they have 3D visualized map of the geology and tunnel geometry and accumulate database of construction information such as tunnel face mapping results, special notes and pictures of construction and 3D monitoring data, all matters on the stability of rock bolts and shotcrete, and so on. Ground settlement prediction program included in ITIS, based on the artificial neural network(ANN) and supported by GIS technology is applying to the subway tunnel. This prediction tool can make it possible to visualize the ground settlement according to the excavation procedures by contouring the calculated result on 3D GIS map and to assess the damage of buildings in the vicinity of construction site caused by ground settlement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.229-242
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• 2009

Numerical analysis has been performed to estimate maximum settlement, maximum horizontal displacement and total settlement volume at the ground surface due to tunnel excavation varying ground condition, tunnel depth and diameter, and construction condition (volume loss at excavation face). The maximum surface settlement from the numerical analysis has been compared with the maximum settlement at tunnel crown considering ground condition, tunnel depth and diameter, and construction condition, and it has been also compared with the maximum horizontal displacement. In addition, the volume loss ($V_L$) at tunnel excavation face has been compared with the total surface settlement volume ($V_s$) with the variation of ground condition, tunnel depth, and tunnel diameter. The results from the numerical analysis have been compared with field measurements to confirm the applicability and validity of the results and by this comparison it is believed that the numerical results in this study can be utilized practically in analyzing the ground movements due to tunnel excavation.

• Geomechanics and Engineering
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• v.10 no.4
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• pp.471-526
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• 2016

In order to investigate water flow characteristics after inrushing in process of karst tunnel excavation, numerical simulations for five case studies of water inrush from the tunnel floor are carried out by using the FLUENT software on the background of Qiyueshan high risk karst tunnel. Firstly, the velocity-distance curves and pressure-distance curves are drawn by selecting a series of probing lines in a plane. Then, the variation characteristics of velocity and pressure are analyzed and the respective optimized escape routes are made. Finally, water flow characteristics after inrushing from the tunnel floor are discussed and summarized by comparing case studies under the conditions of different water-inrush positions and excavation situations. The results show that: (1) Tunnel constructors should first move to the tunnel side wall and then escape quickly when water inrush happens. (2) Tunnel constructors must not stay at the intersection area of the cross passage and tunnels when escaping. (3) When water inrush from floor happens in the left tunnel, if tunnel constructors meet the cross passage during escaping, they should pass through it rapidly, turn to the right tunnel and run to the entrance. (4) When water inrush from floor happens in the left tunnel, if there is not enough time to escape, tunnel constructors can run to the trolley and other equipment in the vicinity of the right tunnel working face. In addition, some rescuing equipment can be set up at the high location of the cross passage. (5) When water inrush from floor happens in the cross passage, tunnel constructors should move to the tunnel side wall quickly, turn to the tunnel without water inrush and run to the entrance. (6) When water inrush from floor happens in the cross passage, if there is not enough time to escape, tunnel constructors can run to the trolley and other equipment near by the left or the right tunnel working face. The results are of important practical significance and engineering value to ensure the safety of tunnel construction.

• Tunnel and Underground Space
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• v.16 no.6 s.65
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• pp.467-475
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• 2006

The use of face bolt method has been increasing abroad recently. Hence, many tests and measurements are being conducted and reported. Also, it is well hewn that determination of the installation number of foe bolts in the design stage is very difficult due to difference of the ground condition and the type of a bolt to be used. First of all, the type, the number, etc. of bolts used in various tunnel construction sites, investigated, are analyzed. The relationship between bolt and ground condition could not be found because bolts have been used with the other support methods in many cases. In the laboratory test and numerical analysis based on the site investigation, the behavior of ground and pipes installed on the tunnel face to support has been examined. Especially, the installed number is focused on. According to the result of tests, the surface settlement and the axial displacement of the face decrease exponentially as the number of installed bolts increases.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.433-452
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• 2018

The shield tunneling method can minimize surface settlements by preventing the deformation of tunnel face and tunnel intrados due to tunnel excavation. For this purpose, it is very important to control the operating conditions of shield TBM. The face pressure and backfill pressure for tail void grouting should be the most important and immediate measure not only to restrain surface settlement, but also to influence the effective stress and pore water pressure around the circumstance of tunnel during excavation. The reaction of the ground to the application of face pressure and backfill pressure relies on the stiffness and permeability of ground. Especially, the reaction of saturated clayey ground formations, which shows the time-dependent deformation, is different from the permeable ground. Hence, in this paper it was investigated how the TBM operating conditions, ground stiffness, and permeability impact on the surface settlement of saturated clayey ground. For this purpose, a series of parametric studies were carried out by means of the stress-pore water pressure coupled FE analysis. The results show that the settlement of soft clayey ground is divided into the immediate settlement and consolidation settlement. Especially, the consolidation settlement depends on the ground stiffness and permeability. In addition, the existence of critical face pressure and backfill pressure was identified. The face pressure and backfill pressure above the critical value may cause an unexpected increase in the ground settlement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.3
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• pp.215-231
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• 2011

In this study, the behavior of a shallow 2-arch tunnel during the excavation in the sandy ground containing vertical discontinuity plane was experimentally studied. Load transfer mechanism in the pillar caused by a 2-arch tunnel excavation was observed. The position of the vertical discontinuity plane was varied. Model tests were carried out in the normal construction sequence of 2-arch tunnel. Test results-showed that the load transfer caused by the 2-arch tunnel excavation was concentrated in the discontinuity plane, and was cut by the discontinuity plane, so no load transfer took place above the discontinuity plane. It was also shown that the effect of adjacent tunnel excavation on the pillar load and the ground deformation was greater when excavating the upper half-face of the main tunnel, more than when excavating the lower half-face.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.207-213
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• 2020

Umbrella Arch Method (UAM) often employed in the tunnel construction under poor rock mass conditions in Korea. Insertion of steel pipes at the periphery of the tunnel and infiltration of grouts along the pipes into the rock masses increases tunnel stability. There are two major effects of grouts expected at the tunnel face: 1) increase of face stability by enhancing the frictional resistance of discontinuities and 2) decrease of permeability along the rock masses. Increase of resistance and decrease of permeability requires a certain curing time for the grout. In Korea, we require 24 hours for curing of grout, which means no progress of excavation for 24 hours after infiltration of grouts. This step delays the tunnel construction sequences. To eliminate such inefficiency, we propose MTG (Method for Tunnel construction using Grouting technology), which uses extended length of steel pipes (14 m) compared to conventional pipe roof method (12 m). The merit of MTG is the reduction of curing time. Because of the approximately 2 m extension of the length of steel pipe, blasting can be done after infiltration of grouting. For this paper, we conducted experiments on the shear strength behaviors of grout infilled rock joint with elapsing of curing time and blasting induced vibration. The results show that blasting induced vibration under MTG does not influence the mechanical features of grout material, which indicates no influence on the mechanical behaviors of grout, contributing to the stability of tunnels during excavation. This result indicates that MTG is a cost effective and fast construction method for tunneling in Korea.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1299-1306
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• 2005

The introduction of geodetic methods of absolute displacement monitoring in tunnels has improved the value of the measurements significantly. By using this method, structurally controlled behavior and influences of an anisotropic rock mass can be determined and the excavation and support adjusted accordingly. In this study cases of tunnel monitoring in anisotropic/heterogeneous rock masses are analyzed, and various anisotrpic behavior of tunnel can be estimated. Because rock anisotropy and heterogeneity can have great influence on tunnel behavior, tunnel design considering rock anisotropy and heterogeneity is needed. Also under construction, feedback must be performed by using face mapping and monitoring to prevent over-deformation and tunnel collapse.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.3
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• pp.239-248
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• 2020

Exact rock classification helps suitable support patterns to be installed. Face mapping is usually conducted to classify the rock mass using RMR (Rock Mass Ration) or Q values. There have been several attempts to predict the grade of rock mass using mechanical data of jumbo drills or probe drills and photographs of excavation surfaces by using deep learning. However, they took long time, or had a limitation that it is impossible to grasp the rock grade in ahead of the tunnel surface. In this study, a method to predict the Q value ahead of excavation surface is developed using recurrent neural network (RNN) technique and it is compared with the Q values from face mapping for verification. Among Q values from over 4,600 tunnel faces, 70% of data was used for learning, and the rests were used for verification. Repeated learnings were performed in different number of learning and number of previous excavation surfaces utilized for learning. The coincidence between the predicted and actual Q values was compared with the root mean square error (RMSE). RMSE value from 600 times repeated learning with 2 prior excavation faces gives a lowest values. The results from this study can vary with the input data sets, the results can help to understand how the past ground conditions affect the future ground conditions and to predict the Q value ahead of the tunnel excavation face.