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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Tunnel and Underground Space
Journal Basic Information
Journal DOI :
Korean Society for Rock Mechanics
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Volume & Issues
Volume 22, Issue 6 - Dec 2012
Volume 22, Issue 5 - Oct 2012
Volume 22, Issue 4 - Aug 2012
Volume 22, Issue 3 - Jun 2012
Volume 22, Issue 2 - Apr 2012
Volume 22, Issue 1 - Feb 2012
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Mechanical Properties of a Lining System under Cyclic Loading Conditions in Underground Lined Rock Cavern for Compressed Air Energy Storage
Cheon, Dae-Sung ; Park, Chan ; Jung, Yong-Bok ; Park, Chul-Whan ; Song, Won-Kyong ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 77~85
DOI : 10.7474/TUS.2012.22.2.077
In a material, micro-cracks can be progressively occurred, propagated and finally lead to failure when it is subjected to cyclic or periodic loading less than its ultimate strength. This phenomenon, fatigue, is usually considered in a metal, alloy and structures under repeated loading conditions. In underground structures, a static creep behavior rather than a dynamic fatigue behavior is mostly considered. However, when compressed air is stored in a rock cavern, an inner pressure is periodically changed due to repeated in- and-out process of compressed air. Therefore mechanical properties of surrounding rock mass and an inner lining system under cyclic loading/unloading conditions should be investigated. In this study, considering an underground lined rock cavern for compressed air energy storage (CAES), the mechanical properties of a lining system, that is, concrete lining and plug under periodic loading/unloading conditions were characterized through cyclic bending tests and shear tests. From these tests, the stability of the plug was evaluated and the S-N line of the concrete lining was obtained.
Comparative Study on the Applicability of Point Estimate Methods in Combination with Numerical Analysis for the Probabilistic Reliability Assessment of Underground Structures
Park, Do-Hyun ; Kim, Hyung-Mok ; Ryu, Dong-Woo ; Choi, Byung-Hee ; Han, Kong-Chang ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 86~92
DOI : 10.7474/TUS.2012.22.2.086
Point estimate method has a less accuracy than Monte Carlo simulation that is usually considered as an exact probabilistic method, but this method still remains popular in probability-based reliability assessment in geotechnical and rock engineering, because it significantly reduce the number of sampling points and produces the statistical moments of a performance function in a reasonable accuracy. In the present study, we investigated the accuracy and applicability of point estimate methods proposed by Rosenblueth and Zhou & Nowak by comparing the results of these two methods with those of Monte Carlo simulations. The comparison was carried out for the problem of a lined circular tunnel in an elastic medium where an closed-form analytical solution is given. The comparison results showed that despite the non-linearity of the analytical solution, the statistical moments calculated by the point estimate methods and the Monte Carlo simulations agreed well with an average error of roughly 1-2%. This average error demonstrates the applicability of the two point estimate methods for the probabilistic reliability assessment of underground structures in combination with numerical analysis.
Comparison of Two- and Three-dimensional Approaches for the Numerical Determination of Equivalent Mechanical Properties of Fractured Rock Masses
Min, Ki-Bok ; Thoraval, Alain ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 93~105
DOI : 10.7474/TUS.2012.22.2.093
This paper compares the two- and three-dimensional (2D and 3D) approaches for the numerical determination of the equivalent mechanical properties of fractured rock masses. Both orthogonally-fractured model and discrete fracture networks (DFN) were used for the geometry and 2D models were cut in various directions from 3D model to compare their mechanical properties. Geological data were loosely based on the data available from Sellafield, UK. Analytical method based on compliance tensor transformation was used for investigation in orthogonally fractured rock and numerical experiments were conducted on fractured rock mass with DFN geometry. It is shown that 2D approach always overestimates the elastic modulus of fractured rock masses by a factor of up to around two because fractures are assumed to be perpendicular to the model plane in 2D problems. Poisson ratios tend to have larger values in 2D analysis while there is opposite trend in some sections. The study quantitatively demonstrates the limitation of the 2D approach that uses the simplified model from true 3D geometry.
A New Coefficient for Three Dimensional Quantification of Rock Joint Roughness
Park, Jung-Wook ; Lee, Yong-Ki ; Song, Jae-Joon ; Choi, Byung-Hee ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 106~119
DOI : 10.7474/TUS.2012.22.2.106
Roughness of rock joint has generally been characterized based upon geometrical aspects of a two-dimensional surface profile. The appropriate description of joint roughness, however, should consider the features of roughness mobilization at contact areas under normal and shear loads. In this study, direct shear tests were conducted on the replicas of tensile fractured gneiss joints and the influence of the shear direction on the shear behavior and effective roughness was examined. In this procedure, a joint surface was represented as a group of triangular planes, and the steepness of each plane was characterized using the concepts of the active and inactive micro-slope angles. The contact areas at peak strength which were estimated by a numerical method showed that the locations of the contact areas were mainly dependent on the distribution of the micro-slope angle and the shear behavior of joint was dominated by only the fractions with active micro-slope angles. Therefore, a three-dimensional coefficient for the quantification of rock joint roughness is proposed based on the distribution of active micro-slope angle: active roughness coefficient,
. Comparison of the active roughness coefficient and the peak shear strength obtained from the experiment suggests that the active roughness coefficient is the effective parameter to quantify the surface roughness and estimate the shear behavior of rock joint.
Numerical Design Approach to Determining the Dimension of Large-Scale Underground Mine Structures
Lee, Yun-Su ; Park, Do-Hyun ; SunWoo, Choon ; Kim, Gyo-Won ; Kang, Jung-Seok ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 120~129
DOI : 10.7474/TUS.2012.22.2.120
Recently, mining facilities have being installed in an underground space according to a social demand for environment-friendly mine development. The underground structures for mining facilities usually requires a large volume of space with width greater than height, and thus the stability assessment of the large-scale underground mine structure is an important issue. In this study, we analysed a factor of safety based on strength reduction method, and proposed a numerical design approach to determining the dimension of underground mine structures in combination with a strength reduction method and a multivariate regression analysis. Input design parameters considered in the present study were the stress ratio and shear strength of rock mass, and the width and cover depth of underground mine structures. The stabilities of underground mine structures were assessed in terms of factor of safety under different conditions of the above input parameters. It was calculated by the strength reduction method, and several kinds of fit functions were obtained through various multivariate regression analyses. Using a best-fit regression model, we proposed the charts which provide preliminary design information on the dimension of underground mine structures.
Numerical Analysis on the Performance Evaluation of Cablebolts as Tunnel Supports
Park, Yeon-Jun ; Park, Joon-Hyoung ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 130~143
DOI : 10.7474/TUS.2012.22.2.130
Cablebolts used to be employed as auxiliary supports where long or high capacity bolts are needed, but become competitive by the improvements in supportability and easiness in handling. Based on the test results obtained from various researches, the performance of the cablebolts was analyzed numerically while varying lengths and fixing conditions. The supporting effecte is assessed by monitoring displacements and stress taken place in shotcrete. When cablebolts are grouted without being tensioned, supporting effect was not as good as that of rockbolts. But, their supportability was good enough to substitute rockbolts if tensioned properly. Post grouting right after tensioning of the cablebolts shows reduction in supportability, but long term stability could be achieved without losing supportability if grouted when the bolt is far enough from the face. Further study is necessary including laboratory and in-situ tests under various conditions to use cablebolts as main support in tunnels.
A Study on Punch Penetration Test for Performance Estimation of Tunnel Boring Machine
Jeong, Ho-Young ; Jeon, Seok-Won ; Cho, Jung-Woo ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 144~156
DOI : 10.7474/TUS.2012.22.2.144
This paper discusses the methods of estimating the punch penetration indices and data analysis punch penetration test to estimate the TBM normal force and penetration rate. In punch penetration test is known as a useful test to estimate penetration rates and normal force of TBMs directly with several slope indices indicated drill-ability and brittleness of rocks. However, the standard methods and indices for punch penetration test are not suggested yet. The main purpose of punch penetration test which is prediction of normal force of TBM disc cutter when cutters excavate rock mass. In this study, the punch penetration tests were performed for 6 representative Korean rock types and variety length and diameter of rock core specimens. Among slope indices were obtained from punch penetration test, PLI and MLI which is suggested in this study show high correlation with cutter force measured by full-scale cutting test. The results show that the predicted normal force of a single disc cutter and the experimental error was 10%. Based on these results, it is concluded that punch penetration test is reliable laboratory test for estimating thrust and penetration rates of TBM.
A Study on the Shock Compaction of Ceramic Powders using Explosive
Kim, Young-Kook ; Kim, See-Jo ; Cho, Sang-Ho ;
Tunnel and Underground Space, volume 22, issue 2, 2012, Pages 157~161
DOI : 10.7474/TUS.2012.22.2.157
-2% powder were consolidated by shock compaction technique, which uses a high performance explosive. The microstructural and electrical characteristics of
compact with density of 97% and hardness of 220~250
were investigated using SEM (Scanning Electron Microscope) and X-ray diffraction analysis, respectively. In the microstructures of the compact, there were no visible cracks at most of the surface areas, and interparticle bonding between powder particles was confirmed. The broadened peaks were detected due to deformation of crystallited size and high electric resistances were confirmed due to increased grains because of shock energy with a high pressure and high velocity.