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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 20, Issue 6 - Dec 2010
Volume 20, Issue 5 - Oct 2010
Volume 20, Issue 4 - Aug 2010
Volume 20, Issue 3 - Jun 2010
Volume 20, Issue 2 - Apr 2010
Volume 20, Issue 1 - Feb 2010
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The Analysis of Tunnel Behavior using Different Constitutive Models
Kim, Young-Min ; Kang, Seong-Gwi ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 73~81
The paper presents the application of FE simulations of NATM tunnel using different constitutive models. The results from a series of two dimensional plane strain finite element analyses of medium-liner interaction for NATM are presented. Four types of constitutive models are considered, namely, linear elastic, elasto-plastic Mohr-Coulomb, Hardening-Soil, Soft-Soil model. The design for tunnels requires a proper estimate of surface settlement and lining forces. It is shown that the advanced constitutive model gives better predictions for both ground movement and structural forces.
Numerical Analysis of Grout Flow and Injection Pressure Affected by Joint Roughness and Aperture
Jeon, Ki-Hwan ; Ryu, Dong-Woo ; Kim, Hyung-Mok ; Park, Eui-Seob ; Song, Jae-Jun ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 82~91
Grouting technology is one of the ground improvement methods used in water controlling and reinforcement of rock mass in underground structure construction. It is necessarily required to find out the characteristics of grout flow through discontinuities in a rock mass for an adequate grout design and performance assessment. Laminar flow is not always applicable in simulating a grout flow in a rock mass, since the rock joints usually have apertures at a micro-scale and the flow through these joints is affected by the joint roughness and the velocity profile of the flow changes partially near the roughness. Thus, the influence of joint roughness and aperture on the grout flow in rough rock joint was numerically investigated in this study. The commercial computational fluid dynamics code, FLUENT, was applied for this purpose. The computed results by embedded Herschel-Bulkley model and VOF (volume of fluid) model, which are applicable to simulate grout flow in a narrow rock joint that is filled with air and water, were well compared with that of analytical results and previously published laboratory test for the verification. The injection pressure required to keep constant injection rate of grout was calculated in a variety of Joint Roughness Coefficient (JRC) and aperture conditions, and the effect of joint roughness and aperture on grout flow were quantified.
A Study on the Application of Ventilation Equipment in an Underground Fire
Lee, Sung-Ryong ; Han, Dong-Hoon ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 92~96
In this study, experiments were conducted to evaluate the effectiveness of ventilation equipment in underground fires. Two type of Ventilators were used in experiments. Experiments were carried out using ethanol square pool fire. Maximum heat release rate was about 460kW. Visibility and temperature distribution were evaluated according to mechanical ventilation. In blower type ventilation, visibility was increased and temperature was lowered.
Prediction of Failure Time of Tunnel Applying the Curve Fitting Techniques
Yoon, Yong-Kyun ; Jo, Young-Do ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 97~104
The materials failure relation
is a measurable quantity such as displacement and the dot superscript is the time derivative, may be used to analyze the accelerating creep of materials. Coefficients, A and
, are determined by fitting given data sets. In this study, it is tried to predict the failure time of tunnel using the materials failure relation. Four fitting techniques of applying the materials failure relation are attempted to forecast a failure time. Log velocity versus log acceleration technique, log time versus log velocity technique, inverse velocity technique are based on the linear least squares fits and non-linear least squares technique utilizes the Levenberg-Marquardt algorithm. Since the log velocity versus log acceleration technique utilizes a logarithmic representation of the materials failure relation, it indicates the suitability of the materials failure relation applied to predict a failure time of tunnel. A linear correlation between log velocity and log acceleration appears satisfactory(R=0.84) and this represents that the materials failure relation is a suitable model for predicting a failure time of tunnel. Through comparing the real failure time of tunnel with the predicted failure times from four curve fittings, it is shown that the log time versus log velocity technique results in the best prediction.
Measurement of Soft Ground Foundation and Rock Slope Behavior Using Spiral Bolt Strain Gauge
Kang, Seong-Seung ; Hirata, Atsuo ; Jeong, Seong-Hoi ; Lee, Woo-Ram ; Je, Dong-Kwang ; Kim, Dae-Hyeon ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 105~111
This study is to consider applicability of spiral bolt strain gauge as an instrument measuring behavior of soft ground foundation and rock slope. When the instrument was installed on the ground, it can be useful to identify the state of ground behavior because it has the characteristics of flexibility, as well as to apply the ground reinforcement because it has higher pull-out resistance to the ground. From the measurement of behavior to soft ground foundation, the strain shows a stable state in the beginning, then was observed significant change in the upper and the middle of spiral bolt strain gauge after 400 days. This is analyzed that ground loosening, which is due to occurred frequent earthquake of magnitude 1~2 with increased rainfall, lead to the instability of the ground. From the measurement of behavior to rock slope, the strain shows a stable state with very little change in a period of 0~50 days and the biggest strain at 4.2 m (P6) in a period of 50~100 days, then other places except P6 was maintained at a stable state in a period of 100~160 days. The reason is analyzed because that blasting for excavated limestone surrounding was affected to the largest at P6. However, based on the size of strain change by behavior of the soft ground foundation and rock slope, it is considered that the present condition are not effected on stability of retaining structure and rock slope. In conclusion, the proposed spiral bolt strain gauge can be useful to measure behavior of soft ground foundation and rock slope, and also to be measured behavior as well as reinforcement of the target ground.
Prediction of Principal Frequency of Ground Vibration from Delayed Blasting
Chung, Doo-Sung ; Kang, Choo-Won ; Ko, Jin-Seok ; Chang, Ho-Min ; Ryu, Pog-Hyun ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 112~118
Before blasts that can have direct impacts on human bodies or structures, it is necessary to assess impacts of ground vibration. Therefore, frequency has been recognized as an important factor in order to assess impact on ground vibration and damages. There have been many studies on impacts of frequency. But, there have been no studies on relations between vibration and frequency according to delay time difference. In this study, we examined the relations between delay time difference and frequency according to each frequency with which reinforcement and destructive intervention repeat through delay time difference obtained using superposition modeling of single hole blasting waveform based on the theory of time difference developed by Langefors.
Effects of Strain Rate and Water Saturation on the Tensile Strength of Rocks
Jung, Woo-Jin ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 119~124
Hopkinson's effect tests were carried out for various strain rates on three different types of rock in both saturated and dry states in order to examine the effects of strain rate and water saturation on tensile strength. The tensile strength increased with the increase of the strain rate not only in dry state but also in saturated state. It was also especially recognizable that the dynamic tensile strength of rock in the dry state was proportional to approximately a one-third multiple of strain rate no matter what the type of rock. It was found that water saturation decreased tensile strength in the dry state of sandstone and tuff, both with high porosity, but no significant difference could be recognized between the dry and the saturated states of granite, which has a low porosity of 0.49%.
A Study on the Effectiveness of a Guide Hole on Crack Growth Control in Blasting
Lee, Hee-Gwang ; Kim, Seung-Kon ; Cho, Sang-Ho ;
Tunnel and Underground Space, volume 20, issue 2, 2010, Pages 125~130
Model blast experiments of mortar blocks were performed to investigate the effect of the guide hole on crack growth. The mortar block specimens have a blast charge hole and 8 guide holes. Two of circular guide hole, notched guide hole, diamond shaped guide hole and diamond shaped guide holder are installed around 110 mm, 165 mm and 220 mm apart from the charge hole for each specimen. From the blast experiments, it was revealed that all the guide hole used in this study were effective for controlling the crack growth at the fracture control.