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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Tunnel and Underground Space
Journal Basic Information
Journal DOI :
Korean Society for Rock Mechanics
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Volume & Issues
Volume 16, Issue 6 - Dec 2006
Volume 16, Issue 5 - Oct 2006
Volume 16, Issue 4 - Aug 2006
Volume 16, Issue 3 - Jun 2006
Volume 16, Issue 2 - Apr 2006
Volume 16, Issue 1 - Feb 2006
Selecting the target year
Study of Brittle Failure
Cheon, Dae-Sung ; Synn, Joong-Ho ; Jeon, Seo-Kwon ; Park, Chan ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 437~450
Failure around an underground opening is a function of in-situ stress magnitudes, intact rock strength and the distribution of fractures in the rock mass. At high in-situ stress, the failure process is affected and eventually dominated by stress-induced fractures preferentially growing parallel to the excavation boundary. This fracturing is often observed in brittle type of failure such as slabbing or spatting. Recent studies dies on the stress-induced damage of rock revealed its importance especially in a highly stressed regime. As the constructions of underground structures at deep depths increased, the cases of the brittle failure also increased and furthermore spalling was occurred in Korea at low depths. To improve the stability of the underground structures at highly stressed regime, the characteristics of brittle failure should be examined, but they have not yet been properly investigated. Therefore in this report the characteristics of brittle failure such as types, failure mechanism and modeling methods etc. were considered in all aspects, based on the previous researches.
Monitoring of Cut-Slope Behavior with Consideration of Rock Structure and Failure Mode
Cho, Tae-Chin ; Park, So-Young ; Lee, Sang-Bae ; Lee, Geun-Ho ; Won, Kyung-Sik ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 451~466
Analysis of slope behavior concerning the structural characteristics of field rock mass can be processed by virtue of borehole information of joint orientation and position acquired from DOM drilled core. Anticipated sliding potential of pre-failed rock slope is analyzed and the regional slope instability is investigated by inspecting the hazardous joints and blocks the traces of which is projected on the cut-face. Cross section has been set at the center of rock slope and the traces of both joints and tetrahedral blocks, which potentially can induce the slope failure, are drawn to investigate the failure modes and the triggering mechanism. Automated monitoring system has been established to measure the slope movement and especially, inclinometer has been installed inside DOM borehole to analyze the slope movement by considering the internal rock structure. Algorithms for predicting the slope failure time have been reviewed and the significance of heavy rainfall on the slope behavior has been investigated.
A Study of the Optimum Installation Number of Face Bolts Using Laboratory Tests and Numerical Analysis
Seo, Kyoung-Won ; Kazuo, Nishimurn ; Kim, Chang-Young ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 467~475
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.
Numerical Simulation of Fracture Mechanism by Blasting using PFC2D
Jong, Yong-Hun ; Lee, Chung-In ; Jeon, Seok-Won ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 476~485
During blasting, both shock wave and gas are generated in detonation process of explosives and the generated wave and gas expansion may create new fractures and damage rock mass. In order to explain and understand completely the fracture mechanism by blasting, we have to consider both effects of the wave and gas expansion simultaneously. In this study, we use a discrete element code, PFC2D and develop an algorithm which is capable of modeling both detonation and gas pressures acting on blasthole wall and visualizing generated cracks within rock mass. Moreover, the gas-pressure modeling method which applies a corresponding external force of gas pressure to parent particles of radial fractures is adopted to simulate a coopting between rock mass and gas penetrating created radial fractures. The developed algorithm is verified by reproducing numerical simulations of a lab-scale test blast successfully.
Analysis of Site Amplification Characteristics of Several Seismic Stations Distributed in the Southern Korean Peninsula
Kim, Jun-Kyoung ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 486~494
The horizontal to vertical (H/V) ratio technique in spectral domain is a common useful technique to estimate empirical site transfer function. The technique, originally proposed by Nakamura, is proposed to analyse the surface waves in the micrortremor records. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that most of the stations have fairly good amplification characteristics in low frequency band. However, some of the seismic stations show one (resonant frequency specific to the site) or several local peaks of amplification factors with narrow high frequency band. Even though the site amplification characteristics are important information, we should be careful to analyse the observed ground motions from the seismic stations which have several very high amplification peaks for the deconvolution of seismic source and attenuation parameters.
Strain-Softening Behavior of Circular Tunnel Excavated in Mohr-Coulomb Rock Mass
Lee, Youn-Kyou ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 495~505
Calculating the distribution of stresses and displacements around a circular tunnel excavated in infinite isotropic rock mass subjected to hydrostatic stress condition is one of the basic problems in rock engineering. While closed-form solutions for the distribution are known if rock masses are considered as elastic, perfectly plastic, or brittle-plastic media, a few numerically approximated solutions based on various simplifying assumptions have been reported for strain-softening rock mass. In this study, a simple numerical method is introduced for the analysis of strain-softening behavior of the circular tunnel in Mohr-Coulomb rock mass. The method can also applied to the analysis of the tunnel in brittle-plastic or perfectly plastic media. For the brittle-plastic case where closed-formsolution exists, the performance of the present method is verified by showing an excellent agreement between two solutions. In order to demonstrate the strain-softening behaviors predicted by the proposed method. a parameter study for a softening index is given and the construction of ground reaction curves is carried out. The importance of defining the characteristics of dilation in plastic analysis is discussed through analyzing the displacements near the surface of tunnel.
Case Study on the Causes for the Failure of Large Scale Rock Mass Slope Composed of Metasedimentary Rocks
Park, Boo-Seong ; Jo, Hyun ; Cha, Seung-Hun ; Lee, Ki-Hwan ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 506~525
For the design of large scale rock slope which has complex formations and geological structures, generally, insufficiency of geotechnical investigations and laboratory tests are the main factors of slope failures doling construction. In such case, remedial measures to stabilize slope should be selected and applied through reliable investigations and analysis considering the geotechnical characteristics. The rock slope of this study, one of the largest cut slopes in Korea with a length of 520.0 m and maximum height of 122.0 m consists of metasedimentary rocks. And a case study on the causes of large-scale rock slope failure was carried out by analysis of landslides history and site investigations during construction. When the slope with the original design slope of 0.7: 1.0 (H:V) was partially constructed, the slope failure was occurred due to the factors such as poor conditions of rocks (weathered zone, coaly shale and fault shear zone), various discontinuities (joints, foliations and faults), severe rain storm and so on. The types of failures were rockfall, circular failure, wedge failure and the combination of these types. So, the design of slope was changed three times to ensure long-term slope stability. This paper is intended to be a useful reference for analyzing and estimating the stability of rock slopes whose site conditions are similar to those of this study site such as geological structures and geotechnical properties.
An experimental study on the smoke-spread region before reaching the critical velocity for the case of fires in tunnels employing longitudinal ventilation system
Ki, Young-Min ; Yoon, Sung-Wook ; Yoon, Chan-Hoon ; Kim, Jin ;
Tunnel and Underground Space, volume 16, issue 6, 2006, Pages 526~535
An experimental study was carried out on a reduced scale tunnel model to grasp the behavioral feature of fire-induced smoke in the long tunnels. Based on Froude modeling, the 1/50 scaled tunnel model (20 m long) was constructed by acrylic tubes and paraffin gas was released inside the tunnel to simulate the 20 MW fire-induced smoke. me test results show, that after approximately 2 minutes of fire generation, was descended from the tunnel ceiling through the decrease of buoyancy, then it was symmetrically propagated about 90 meters for 4 minutes before jet fans were operated. The smoke was effectively controlled when the jet fans were operated and an air stream velocity was getting closed to reach a critical velocity (the minimum air velocity that requires to suppress the smoke spreading against the longitudinal ventilation flow during the tunnel fire situations). It was also found out that a range of smoke was spreaded about 3 meters from the origin of fire but the range was not propagated to the escape direction anymore. The early stage of the In operation, however, showed that the smoke was hardly controlled. It means that the operation of emergency ventilation system has many dangerous factors such as an intercepting breathing zone.