• The Journal of Engineering Geology
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• v.13 no.3
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• pp.359-368
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• 2003

A quarry is operated for filling-up the New Busan Harbor which is under construction, but actual rock quality is something different from the primary design. Therefore, object of this study is to classify whole rock quality for the quarry through site investigation and laboratory analyses because unexpected large amount of wasted rock is produced. For this object, various analyses were performed such as surveying, Schimidt Hammer test. joint spacing investigation and laboratory analyses using DIPS & RockWorks programs for evaluating joint sets and sizes of rock fragments after blasting. As a result, it is expected that large amount of wasted rock under ${\Phi}100mm$ is produced after blasting because of high joint density.

• Geomechanics and Engineering
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• v.9 no.3
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• pp.329-344
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• 2015

Cratering tests in rock are generally carried out to identify its fragmentation characteristics. The test results can be used to estimate the minimum amount of explosives required for the target volume of rock fragmentation. However, it is not easy to perform this type of test due to its high cost and difficulty in securing the test site with the same ground conditions as the site where blasting is to be performed. Consequently, this study investigates the characteristics of rock fragmentation by using the hydrocode in the platform of AUTODYN. The effectiveness of the numerical models adopted are validated against several cratering test results available in the literature, and the effects of rock mass classification and ground formation on crater size are examined. The numerical analysis shows that the dimension of a crater is increased with a decrease in rock quality, and the formation of a crater is highly dependent on a rock of lowest quality in the case of mixed ground. It is expected that the results of the present study can also be applied to the estimation of the level and extent of the damage induced by blasting in concrete structures.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.166-171
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• 1996

This study examines whether the raw diatomaceous rock, after thermally activated for converting into a pozzolanic form, can improve cement quality(i.e., compressive strength) of the cement-mortar. The diatomaceous rock, heat-treated at 75$0^{\circ}C$ for 30minutes as an optimum pozzolanic form was mixed with OPC(Ordinary Portland Cement) on a weight basis from 0, 2.5, 5.0, 10, 20, 40%. The cement quality was then assessed by the compressive strength and analysis of XRD(S-Ray Diffraction) and SEM(Scanning Electron Microscope).

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.737-744
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• 2000

This paper resorts to rock mass rating and rock mass quality to draw value based on the evaluation of rock and to draw interrelation formula in relation to rock mass quality, A comparative analysis was given of survey values reported in the existing documents. This paper has tried to find out the relationship between RMR and Q System for the sake of choosing rational reinforcing patterns and of the safety of tunnels. The results run as follow: RMR=8.251n(Q)+43.83. This paper has also tried to find out the relationship between RMR and Q System by using Fuzzy Approximate Reasoning Concept. We suggest that those in charge should not depend on a single system only after evaluating the classification of rocks, and compare one result with another for the good of keeping track of the condition of base rocks in a better way.

• Journal of fish pathology
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• v.34 no.1
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• pp.1-7
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• 2021

Red sea bream iridovirus (RSIV), belonging to the genus Megalocytivirus, is the predominant cause of mortality in marine fishes in Korea, including rock bream (Oplegnathus fasciatus). Rockfish (Sebastes schlegelii) are the host fish for RSIV, exhibiting no clinical signs or mortality. Cohabitation challenges, which mimicked natural transmission conditions, were performed to evaluate viral transmission between rock bream and rockfish, and to determine the pathogenicity and viral loads. In cohabitation challenge, artificially RSIV-infected rock bream were the viral donor, and healthy rockfish were the recipient. The results showed that although the donor rock bream had 95-100 % cumulative mortality (>10⁸ viral genome copies/mg of spleen 7-14 days after viral infection), the recipient rockfish did not die, even when the viral genome copies in the spleen were >10⁵ copies/mg. These results indicated asymptomatic infections. Notably, in a reverse-cohabitation challenge (artificially RSIV-infected rockfish as the viral donor and healthy rock bream as the recipient), RSIV horizontally infected from subclinical rockfish to rock bream (10⁷ viral genome copies/mg of spleen 21 days after cohabitation) with 10-20% cumulative mortality. These results suggest that an asymptomatic, infected rockfish can naturally transmit the RSIV without being sacrificed.

• Geomechanics and Engineering
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• v.30 no.6
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• pp.503-515
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• 2022

The permeability coefficient is an essential parameter for the study of seepage flow in fractured rock mass. This paper discusses the feasibility and application value of using readily available RQD (rock quality index) data to estimate mine water inflow and grouting quantity. Firstly, the influence of different fracture frequencies on permeability in a unit area was explored by combining numerical simulation and experiment, and the relationship between fracture frequencies and pressure and flow velocity at the monitoring point in fractured rock mass was obtained. Then, the stochastic function generation program was used to establish the flow analysis model in fractured rock mass to explore the relationship between flow velocity, pressure and analyze the universal law between fracture frequency and permeability. The concepts of fracture width and connectivity are introduced to modify the permeability calculation formula and grouting formula. Finally, based on the on-site grouting water control example, the rock mass quality index is used to estimate the mine water inflow and the grouting quantity. The results show that it is feasible to estimate the fracture frequency and then calculate the permeability coefficient by RQD. The relationship between fracture frequency and RQD is in accordance with exponential function, and the relationship between structure surface frequency and permeability is also in accordance with exponential function. The calculation results are in good agreement with the field monitoring results, which verifies the rationality of the calculation method. The relationship between the rock mass RQD index and the rock mass permeability established in this paper can be used to invert the mechanical parameters of the rock mass or to judge the permeability and safety of the rock mass by using the mechanical parameters of the rock mass, which is of great significance to the prediction of mine water inflow and the safety evaluation of water inrush disaster management.

• Tunnel and Underground Space
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• v.14 no.3
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• pp.215-228
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• 2004

Rock mass contains discontinuities such as faults and joints, and their mechanical properties and spatial distribution dominate the stability of rock mass. Because the deformation of rock mass occurs discontinuities in many cases. However in the case of poor quality rock mass under high stresses, the deformation along intact rock can also influence the structure's stability. In this study, two dimensional finite element program was developed with a rheological model to analyze the stability of the structure excavated in jointed rock mass. The “equivalent material” approach was used assuming intact rock, joints and rock bolts as visco-plastic materials. The program was verified by analysing an intact rock model, a jointed rock mass model and a reinforced jointed rock mass model. The displacement was examined in each model with changing the intact rock behaviour as elastic and visco-plastic. In the case of poor quality rock mass under high stresses, e assumption of visco-plastic behaviour of intact rock resulted in larger displacement than when assuming elastic behaviour for intact rock. Therefore it is recommended to add intact rock's visco-plastic behaviour to the existing model, which only assumes visco-plastic behaviour of joints and rock bolts.

• The Journal of Engineering Geology
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• v.33 no.2
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• pp.307-322
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• 2023

Rock-mass grouting plays a crucial role in the construction of dams and deep caverns, effectively preventing seepage in the foundations, enhancing stability, and mitigating hazards. Most rock grouting is affected by hydrogeological and rock engineering indices such as rock quality designation (RQD), rock mass quality (Q-value), geological strength index (GSI), joint spacing (Js), joint aperture (Ap), lugeon value (Lu), secondary permeability index (SPI), and coefficient of permeability (K). Therefore, accurate geological analysis of basic rock properties and guidelines for grouting construction are essential for ensuring safe and effective grouting design and construction. Such analysis has been applied in dam construction sites, with a particular focus on the geological characteristics of bedrock and the development of prediction methods for grout take. In South Korea, many studies have focused on grout injection materials and construction management techniques. However, there is a notable lack of research on the analysis of hydrogeological and rock engineering information for rock masses, which are essential for the development of appropriate rock grouting plans. This paper reviews the current state of research into the correlation between the grout take with important hydrogeological and rock engineering indices. Based on these findings, future directions for the development of rock grouting research in South Korea are discussed.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.397-410
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• 2022

The safety of the disposal repository for high level radioactive waste should be guaranteed for a quite long period so that the precise evaluations are required. The site characteristics of the discontinuities are essential part of the safe repository design including engineered barrier and natural barrier systems. The discontinuities act like weak planes and at the same time, they act as flow paths so that their features should be investigated thoroughly. RQD (Rock Quality Designation) is one of the most widely applied characterizing methods due to its simplicity, however, modified designations have been proposed because RQD has some drawbacks, such as its directivity and dependence on the threshold length. This study aims to evaluate the applicability of the modified designations by applying them to the rock mass around KURT and to produce fundamental database that will be utilized in future studies.

• Journal of the East Asian Society of Dietary Life
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• v.15 no.1
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• pp.119-125
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• 2005

A kind of mineral water obtained from the basing of deep under the sea was reported to have a characteristic mineral composition and its effect on the quality of Kimchi was evaluated in this study. Kimchi samples were prepared with NaCl and the mineral water under rock floor as sources of salt together with fermented seafoods and fermented at 20 for 6 days. The qualities of Kimchi were evaluated by analyzing the pH, acidity, number of viable cell, lactic acid bacteria, sensory properties and texture profiles during fermentation. The pH and total acid contents were not different among Kimchi samples. The microbiological changes were not observed in the samples. The sensory scores of Kimchi containing NaCI and fermented sandlance sauce, and of Kimchi containing the mineral water under sea rock floor with fermented seafoods were significantly higher than those of the others. On the other hand, Kimchis prepared with NaCl alone or mineral water under sea rock floor alone earned the lowest sensory scores among the tested samples with an exception of firmness of the sample made with the mineral water. As the Kimchi fermentation proceeds, the hardness value of Kimchi prepared with the mineral water became higher than that of Kimchi with NaCl. This study suggests that the mineral water under sea rock floor could be useful to keep the texture of Kimchi firm during the fermentation.