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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of Korean Tunnelling and Underground Space Association
Journal Basic Information
Journal DOI :
Korean Tunnelling and Underground Space Association (KTA)
Editor in Chief :
Volume & Issues
Volume 16, Issue 6 - Nov 2014
Volume 16, Issue 5 - Sep 2014
Volume 16, Issue 4 - Jul 2014
Volume 16, Issue 3 - May 2014
Volume 16, Issue 2 - Mar 2014
Volume 16, Issue 1 - Jan 2014
Selecting the target year
A study on the estimation of the optimal number of monitoring points in single-track tunnel lining with the inverse analysis program
Woo, Jong-Tae ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 1~11
DOI : 10.9711/KTAJ.2014.16.1.001
In order to determine the optimal number of monitoring points in single-track tunnel lining, this thesis compares and evaluates the results of two cases: when the tunnel lining is modeled into a simple beam form and then is applied to 1) the tunnel lining inverse analysis program, and to 2) the commercially-used program. The displacement and stress of specific tunnel lining cross-sections are determined by entering the load conditions into the commercially-used program for tunnel interpretations. In doing so, two cases were assumed: where a symmetrically-distributed load was acting upon the tunnel lining of a single-track tunnel and where an asymmetrically-distributed load was in action. By comparing the computed displacement with the stress and displacement determined by entering side numbers 3, 5, and 7 into the tunnel lining inverse analysis program, the optimal number of monitoring points is determined. From the results of the research, it can be inferred that the number of monitoring points needs to be at least 5 points, considering the efficiency of monitoring in practice and the loss-and-damage rate of tunnel monitoring.
Prediction of TBM tunnel segment lining forces using ANN technique
Yoo, Chung-Sik ; Choi, Jung-Hyuk ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 13~24
DOI : 10.9711/KTAJ.2014.16.1.013
This paper presents development of artificial neural network(ANN) based prediction method for section forces of TBM tunnel segment lining in an effort to develop an automatized design technique. A series of design cases were first developed and subsequently analyzed using the two-ring beam finite element model. The results were then used to form a database for use as training and validation data sets for ANN development. Using the database, optimized ANNs were developed that can readily be used to predict maximum sectional forces and their distributions. It is shown that the compute maximum section forces and their distributions by the developed ANNs are almost identical to the computed by the two-ring beam finite element model, implying that the developed ANNs can be used as design tools which expedite routine design calculation process. The results of this study indicate that the neural network model can be effectively used as a reliable and simple predictive tool for the prediction of segment sectional forces for design.
A study on the characteristics of multi load transfer ground anchor system
Kim, Ji-Ho ; Jeong, Hyeon-Sic ; Kwon, Oh-Yeob ; Shin, Jong-Ho ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 25~50
DOI : 10.9711/KTAJ.2014.16.1.025
In order to identify a load transfer mechanism of ground anchors, the behavior of multi load transfer ground anchor systems was investigated and compared with those of compression type anchors and tension type anchors. Large scale model tests were performed and stress-strain relationships were obtained. The load transfer mechanism of ground anchors was also investigated in the field tests. Finally, numerical analyses to predict the load-displacement relationships of anchors were conducted. It is concluded that the load transfer characteristics of MLT anchors are mechanically much more superior in the pull-out resistance effect than those of existing compression and tension type anchors. From the results of research work, we could suggest that the max pull-out capacity of anchor capacity to each the soil condition. Also, the MLT anchors can be used to achieve both structural enhancement and economic construction in earth retaining or supporting structures.
Generation of blast load time series under tunnelling
Ahn, Jae-Kwang ; Park, Duhee ; Shin, Young-Wan ; Park, Inn-Joon ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 51~61
DOI : 10.9711/KTAJ.2014.16.1.051
It is necessary to perform a dynamic analysis to numerically evaluate the effect of blasting on nearby facilities. The blast load time history, which cannot be directly measured, is most often determined from empirical equation. The load has to be adjusted to account for various factors influencing the load and the frequency, but there is not a clear guideline on how to adjust the load. In this study, a series of 2D dynamic numerical analyses that simulates a closely monitored test blasting is performed, from which the blast load that matches the measured vibrations are derived. In the analyses, it is assumed that the hole generated by the blasting is in the form of a circle, and the load was applied normally to the wall of the opening. Special attention was given in selecting the damping ratio for the ground, since it has important influence on the wave propagation and attenuation characteristics of the blast induce waves. The damping ratio was selected such that it matches favorably with the attenuation curve of the measurement. The analyses demonstrate that the empirical blast load widely used in practice highly overstimates the vibration since it does not account for the energy loss due to rock fragmentation. If the empirical load is used without proper adjustment, the numerical analysis may seriously overstimate the predicted vibration, and thus has to be reduced in the analysis.
Influence of the joint stiffness on the segment design
Choi, Woo-Yong ; Park, Jong-Deok ; Lee, Seok-Won ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 63~74
DOI : 10.9711/KTAJ.2014.16.1.063
The lining of shield TBM tunnel is composed of segments, therefore segment joints are induced by connecting each segment. Segment joint is considered as joint stiffness in the design of TBM tunnel. Depending on the choice among the different stiffness equations, the joint stiffness values determined can be varied largely. Therefore, the influence of joint stiffness value on the design of segment lining should be verified. In this study, the joint stiffness values were determined firstly by using various equations and total change boundary was justified. Within the change boundary determined, the member forces were calculated by changing the joint stiffness through the numerical analysis and consequently the stability of segment lining was investigated by applying nominal strength. The results showed that the segment joint stiffness did not affect the design of segment lining largely.
Influence analysis of continuous pile walls on the behavior of a soil tunnel at the shallow depth through a parametric study
You, Kwang-Ho ; Yoon, Woo-Jin ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 75~89
DOI : 10.9711/KTAJ.2014.16.1.075
In recent years, utilization of underground space has been increasing in various parts of the world. In particular, open-cut method is usually applied to the shallow depth excavation. However some problems such as extreme traffic congestion and unstability of adjacent structures etc. might occur. In order to cope with these problems, the M-CAM (Modified Cellular Arch Method) method was proposed to excavate soil tunnels at shallow depth with secured enough stability and minimized construction period. In this study, sensitivity analysis was performed to predict the influence of the size of CPW(Continuous Pile Wall) and ground conditions on the behavior of the tunnel. First of all, embedded depth and diameter (or thickness) of CPW, coefficient of lateral earth pressure, and ground conditions were selected as parameters that could affect tunnel stability. Meanwhile, FLAC 2D based on finite difference method was used for numerical analysis. As a result of this study, it was checked out that embedded depth among sizes of CPW had a greatest influence on the stability of a tunnel.
Sensitivity analysis of tunnel stability with a consideration of an excavation damaged zone
Kim, Jin-Soo ; Kwon, Sanki ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 91~104
DOI : 10.9711/KTAJ.2014.16.1.091
An Excavation Damaged Zone (EDZ), in which rock properties are permanently changed due to blasting impact or stress redistribution, can influence the behavior and stability of structures. In this study, the mechanical stability of an underground opening was simulated by using FLAC, which is a two-dimensional modeling code, with a consideration of EDZ. A sensitivity analysis was also carried out with fractional factorial design. From the modeling, it was found that the behavior and the stability of an underground tunnel are strongly dependent on the existence of the EDZ. The sensitivity analysis showed that the key parameters affecting the factor of safety around the tunnel are in-situ stress ratio, depth, cohesion, reduction ratio, internal friction angle, and height and width of the tunnel. It is necessary to consider the EDZ, which can significantly affect mechanical stability in tunnel design.
Flow and smoke behavior of a longitudinal ventilation tunnel with various velocities using computational fluid dynamics
Lee, J.H. ; Kwon, Y.J. ; Kim, D.E. ;
Journal of Korean Tunnelling and Underground Space Association, volume 16, issue 1, 2014, Pages 105~115
DOI : 10.9711/KTAJ.2014.16.1.105
A numerical analysis on the smoke behavior and evacuee safety has been performed with computational fluid dynamics. The purpose of this study is to build computational processes for an evacuation and prevention of a fire disaster of a 3 km-length tunnel in Korea. To save computational cost, 1.5 km of the tunnel that can include a few cross-passing tunnels is considered. We are going to assess the fire safety in a road tunnel according to the smoke level, which consists of the smoke density and the height from the floor. The smoke density is obtained in detail from three-dimensional unsteady CFD analysis. To obtain proper temperature distributions on the tunnel wall, one-dimensional conduction equation is considered instead of an adiabatic wall boundary or a constant heat flux. The tunnel considered in this study equips the cross passing tunnels for evacuees every 250 m. The distance is critical in both safety and economy. The more cross passing tunnels, the more safe but the more expensive. Three different jet fan operations can be considered in this study; under- and over-critical velocities for normal traffic condition and 0-velocoty operation for the traffic congestion. The SE (smoke environment) level maps show a smoke environment and an evacuating behavior every moment.