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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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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 10, Issue 4 - Dec 2008
Volume 10, Issue 3 - Sep 2008
Volume 10, Issue 2 - Jun 2008
Volume 10, Issue 1 - Mar 2008
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Evaluation of bonding state of tunnel shotcrete using impact-echo method - numerical analysis
Song, Ki-Il ; Cho, Gye-Chun ; Chang, Seok-Bue ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 105~118
Shotcrete is one of the main support materials in tunnelling. Its bonding state on excavated rock surfaces controls the safety of the tunnel: De-bonding of shotcrete from an excavated surface decreases the safety of the tunnel. Meanwhile, the bonding state of shotcrete is affected by blasting during excavation at tunnel face as well as bench cut. Generally, the bonding state of shotcrete can be classified as void, de-bonded, or fully bonded. In this study, the state of the back-surface of shotcrete is investigated using impact-echo (IE) techniques. Numerical simulation of IE technique is performed with ABAQUS. Signals obtained from the IE simulations were analyzed at time, frequency, and time-frequency domains, respectively. Using an integrated active signal processing technique coupled with a Short-Time Fourier Transform (STFT) analysis, the bonding state of the shotcrete can be evaluated accurately. As the bonding state worsens, the amplitude of the first peak past the maximum amplitude in the time domain waveform and the maximum energy of the autospectral density are increasing. The resonance frequency becomes detectable and calculable and the contour in time-frequency domain has a long tail parallel to the time axis. Signal characteristics with respect to ground condition were obtained in case of fully bonded condition. As the ground condition worsens, the length of a long tail parallel to the time axis is lengthened and the contour is located in low frequency range under 10 kHz.
A study on asymmetric load on circular shaft due to engineering characteristics of discontinuous rock masses
Shin, Young-Wan ; Moon, Kyoung-Sun ; Joo, Kyoung-Won ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 119~128
In the case of a circular shaft, it is expected that asymmetric loads should apply on the surface rather than symmetric loads due to geographical factors and the non-homogeneity of the jointed rock masses. In this study, discontinuous numerical analysis was carried in order to analyze the characteristics of asymmetric load distribution on the wall of the circular shaft due to anisotropy caused by heterogeneity of rock masses affected by the discontinuities like as a Joint. And it was also analyzed that the effect of the mechanical properties varied with the rock mass rating and horizontal stress with depth had influence in the asymmetric load on the wall of the shaft. In the case of considering the effect of the joint as variable, asymmetric load ratio
, which was defined as the ratio of the load subtracted minimum from maximum to minimum, was below 25% in the hard rock. As regarding the variation of the rock mass rating with depth as variable, the value of
was below than 25% in the hard rock, and the value between 30% and 40% in the soft rock. On the other hand, the
of fractures rock was between
which value was much higher than that in better rock mass rating.
A study on the engineering meanings of the critical strain concept in tunnelling
Park, Si-Hyun ; Shin, Yong-Suk ; Bae, Gyu-Jin ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 129~137
This paper intends to develop an assesment technique for the rapid and quantitative evaluation of tunnel safety during tunnel excavation by using displacement measurements. Control criteria for the field measurements are provided at tunnel construction sites in Korea and other countries. However, it was known that the criteria were not clear and varied depending on the construction sites. In order to make a reasonable support for guidelines, critical strain concept is introduced in this study. And the engineering meanings of the critical strain concept are investigated precisely. In order to do this, at first, the engineering meanings of the original concept from the previous researchers was investigated theoretically for the evaluation of tunnel safely. Subsequently displacement data were obtained by using the commercial program, then the evaluation of tunnel safely was conducted with the view point of previous researches. Additionally, strains are determined from the feedback analyses program by inputting measured displacements that were obtained from the commercial program, then the evaluation of tunnel safety was discussed with the critical strain concept. Consequently it can be concluded that the evaluation of tunnel safety can be determined quantitatively and rapidly in the field by introducing the critical strain concept.
Numerical study on rock fragmentation by TBM disc cutter
Cho, Jung-Woo ; Yu, Sang-Hwa ; Jeon, Seok-Won ; Chang, Soo-Ho ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 139~152
A series of numerical experiments were carried out to simulate the rock cutting behavior by TBM disc cutter in a given took condition. AUTODYN-3D, a commercial program capable of simulating three-dimensional dynamic failure, was utilized to carry out the numerical tests over four different disc cutter spacing conditions. After modelling three-dimensional geometries of disc cutter and rock specimen, the linear cutting tests by a disc cutter were simulated for eight different types of rocks. The numerical result, that is the optimum cutter spacing for isotropic rocks had the good agreements with those from linear cutting test. However, for relatively anisotropic or jointed rocks, the specific energy obtained from the numerical tests was almost two-times bigger than the real linear cutting results. Therefore, to simulate cutting procedures for anisotropic rocks realistically, further studies would be necessary.
Development of IT-based tunnel design system
Yoo, Chung-Sik ; Kim, Sun-Bin ; Yoo, Kwang-Ho ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 153~166
This paper concerns the development of a knowledge-based tunnel design system within the framework of artificial neural networks (ANNs). The system is aimed at expediting a routine tunnel design works such as determination of support patterns and stability analysis of selected support patterns. A number of sub-modules for determination of support patterns and stability assessment were developed and implemented to the system. It is shown that the ANNs trained with the results of 2D and 3D numerical analyses can be generalized with a reasonable accuracy, and that the ANN based tunnel design concept is a robust tool for tunnel design optimization. The details of the system architecture and the ANNs development are discussed in this paper.
Applicability of the single shell tunnel in Korea from the economic evaluation
Kim, Hak-Joon ; Shin, Hyu-Seong ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 167~175
The construction cost for the single shell tunnel is cheaper than that of the double shell tunnel according to the case studies performed in several domestic and foreign tunnels. However, the economic advantage of single shell tunnel drops drastically as the condition of the rock mass deteriorates. Therefore, the single shell tunnelling method should be applied to the good rock mass conditions. The application of the single shell tunnelling method to tunnels in Korea should be determined considering the ratio between the good rock and poor rock masses along the tunnel section. The use of the single shell tunnel is expected to offend depending on the cheap supply of high quality shotcrets and rock bolts developed for single shell tunnels.
A study on full-face sequential blasting using electronic detonator
Yoon, Ji-Sun ; Kim, Su-Hyun ; Bae, Sang-Hoon ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 177~184
In this study, in order to reduce appeals regarding vibration and noise from blasts, the optimum delay-time of the electronic detonator, which can minimize blast vibration, is found through blast-waveform composition and blasting simulation, and we have developed the full-face Sequential Blasting Method based on the studies of damping properties of full-face section blasting. The optimum delay-time of the electronic detonator and Full-face Sequential Blasting Method using electronic detonator was applied to the Gyeongbu high-speed railway construction site to test the feasibility of this method.
Study on comparison with electronic detonation blasting and non-electric detonation blasting
Yoon, Ji-Sun ; Lim, Su-Hwan ; Lee, Jin-Moo ; Bae, Sang-Hoon ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 185~191
Today, Large and bigger underground construction are increased. In this study, Blating used electronic detonation (OBM Method) and non-electric detonation are carried out. Through comparison with two method, reduction of vibration and noise and efficiency of construction are investigated. As a result of this study, using electronic detonation is shown that it can control lower vibration and noise level, and better HCF, mucfile, advance rate and fragmentation.
A comparative study on stability evaluation of caverns by 2D continuum analysis in terms of shape factor
You, Kwang-Ho ; Jung, Ji-Sung ;
Journal of Korean Tunnelling and Underground Space Association, volume 10, issue 2, 2008, Pages 193~205
The construction of underground structures such as oil and food storage caverns are recently increasing in our country. The stability of those underground caverns are greatly influenced by their shape and size. In this study therefore, the effect that the shape of an underground cavern have on its stability were analyzed in terms of safety factor. To this end, caverns with 5 different shapes were investigated and sensitivity analyses were performed based on rock class, overburden, and lateral earth pressure coefficient. The proper amount of shotcrete and rockbolt as supports of a cavern was also assumed based on the shape and site of the cavern and rock conditions. This study is expected to be helpful in designing and evaluating the stability of caverns in future.