• Explosives and Blasting
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• v.32 no.3
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• pp.1-9
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• 2014

Since the rock fragmentation from a bench blasting can affect the subsequent processes including loading, hauling and crushing, its control is essential for the assessment of blasting efficiency as well as production cost. In this study, the delay time could be precisely controlled by using electronic detonators. The rock fragmentations resulted from the blastings with different delay times of 1, 2, 3, 4, 5, 7 and 10ms per each meter of burden were measured from full scale field tests in a limestone mine. The results showed that the optimum delay time for minimum fragmentation was approximately 6ms/m. From the analysis of fragmentation size distribution, it was possible to find that delay time can be a parameter on rock fragmentation and thus it would be possible to control rock fragmentation by adjusting delay time.

• Tunnel and Underground Space
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• v.21 no.6
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• pp.508-517
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• 2011

The linear cutting test is the most reliable and accurate approach to measuring cutting forces and cutting efficiency using full-size disc cutter in various rock types. The result of linear cutting tests can be used to obtain the key parameters of cutter-head design (i.e. optimum cutter spacing, cutter forces). In Korea, LCM (Linear Cutting Machine) tests have been performed for typical Korean rock types, but these studies focused on the isotropic rocktypes. For prediction of TBM (Tunnel Boring Machine) performances in complex geological conditions including a bedded and schistose rockmass, it is important to consider the effects of anisotropy of rockmass on cutting performances and cutting efficiency. This study discusses a series of LCM tests that were performed for Asan Gneiss having two types of anisotropy angles to assess the effect of the anisotropy angle on rock-cutting performances of TBM. The result shows that the rock-cutting performances and optimum cutting conditions are affected by anisotropy angle and the effect of anisotropy on rock strength should be considered in a prediction of the cutting performances and efficiency of TBM.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.35-41
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• 2000

Residual stress is defined as a minimum stress with a large displacement of specimens and the residual stress after peak shear stress appears with displacement volume but there is no provision to select the residual stress. In the previous study, residual stress was recorded when the change of shear load is small in the condition of the strain more than 15%. But, in this study, hyperbolic function((No Abstract.see full/text), b=experimental constant) of soil test is adapted to joint of rock and the propriety is investigated. In a landslide and landsliding of artificial slope, wedge failure of tunnel with a large displacement, tests are simulated from peak stress to residual stress for safety analysis. But now. direct shear stress and triaxial compressive tests are usually performed to find out characteristics of shear stress about joint. Although these tests get a small displacement, that data of peak stress and residual stress are used for safety analysis. In this study, we tried to determine failure criteria for joints of rock using ring shear test machine. The residual stress following shear behavior was determined by the result of ring shear test and direct shear test. In conclusion, after comparing the results of the two test, we found that cohesion(c) and internal friction angle(ø) of ring shear test are 30% and 22% respectively of those of the direct shear test.

• Journal of fish pathology
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• v.26 no.3
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• pp.295-301
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• 2013

Ferritin is an evolutionarily conserved protein that plays an important role in iron storage and detoxification. In this study, the gene encoding a ferritin H subunit homologue (RbFH) was cloned from rock bream (Oplegnathus fasciatus) and analyzed at the expression. The full-length ferritin H cDNA was 1162 bp long and contained an open reading frame (ORF) of 531 bp that encoded 177 amino acid residues with a predicted molecular mass of 20.8 kDa. The 5' UTR was 297 bp in length, and the 3' UTR 298 bp, and preceded by a 5'-untranslated region that contains a putative Iron Regulatory Element (IRE). The deduced amino acid sequence of RbFH shares extensive sequence identities with the H ferritins of a number of fish species and contains the ferroxidase center that is preserved in ferritin H subunits. Examination of tissue specific expression indicated that RbFH expression was most abundant in PBLs, RBC, liver and muscle.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.149-157
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• 1994

In this study two dimensional visco-plastic finite element model capable of handling the multi-step excavation was developed for investigating the effect of excavation support sequences on the behavior of underground openings in the jointed rock mass. First, the finite element model which is capable of handling the multi-step excavation is developed and verified. And then the model is combined with visco-plastic joint model. Ubiquitous joint pattern was considered in the model and joint properties in cach set were assumed to be indentical. Passive, full-grouted rockbolts were cosidered in the numerical model. The visco-plastic deformations of joints and rockbolts were assumed to be governed by Mohr-Conlomb and von Mises yield criteria, respectively. With the ability of removing elements, the model can simulate the multi-step excavation-suppport sequences. The reliability and applicability of the model to the stability analysis for the underground excavation in pratice was checked by simulating the behavior of underground crude oil storage caverns under construction.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.629-634
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• 2000

Rockfall protection fence which is used for mitigation of rockfall hazard, has been constructed without consideration of lithology, height and dip angle of rock slope. However, those factors should be considered for the construction of the protection fence. In addition, the protection fence should be evaluated its performance by in-situ test in order to utilize the fence effectively. This is the first full sized rockfall test in Korea. For this test, the rock cut slope whose height is about 20 m and dip angle is 65 $^{\circ}$ has been chosen. Based on the preliminary simulation procedure, four different concrete balls (0.5 ton, 1.0 ton, 2.0 ton and 5.0 ton) were prepared and four different types of protection fence were constructed. The results of this test will be utilized in the establishment of rockfall protection fence construction manual.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.383-399
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• 2020

Optimizing the spacing of the disc cutter is a key element in the design of the TBM cutter head, which determines the drilling performance of the TBM. The full-scale linear cutting test is known as the most reliable and accurate test for calculating the spacing of the disc cutter, but it has the disadvantage of costly and time-consuming for the full-scale experiment. In this study, through the numerical analysis study based on the discrete element method, the tendency between Specific Energy-S/P ratio according to uniaxial compression strength and penetration depth of rock was analyzed, and the optimum spacing of 17-inch disc cutter was derived. To examine the appropriateness of the numerical analysis model, the rolling force acting on the disc cutter was compared and reviewed with the CSM model. As a result of numerical analysis for the linear cutting test, the rolling force acting on the disc cutter was analyzed to be similar to the rolling force derived from the theoretical formula of the CSM model. From the numerical analysis on 5 UCS cases (50 MPa, 70 MPa, 100 MPa, 150 MPa, 200 MPa), it is found that the range of the optimum spacing of the disc cutter decreases as the rock strength increases. And it can be concluded that 80~100 mm of disc cutter spacing is the optimum range having minimum specific energy regardless of rock strength. This tends to coincide with the optimal spacing of previously reported disk cutters, which underpins the disk cutter spacing calculated through this study.

• Proceedings of the Zoological Society Korea Conference
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• 2001.10a
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• pp.184.3-185
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• 2001

No Abstract, See Full Text

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.269-272
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• 2007

See Full Text

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.460-462
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• 2007

See Full Text