• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1999.03a
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• pp.33-40
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• 1999

암석 및 암반을 대상으로 AE 법에 의해 파괴원 위치를 결정하는 경우 복잡한 수학적 알고리즘을 필요로 하며, 다수의 연구자에 의해 수많은 방법들이 개발되어 왔으나 각 해법의 특성에 따라 부분적인 오차를 보이는 것으로 보고되어 있다. 이와 같이 재래식 계산법에 의한 파괴원 위치의 결정은 오차를 감소시키기 위해 다양한 알고리즘이 적용되어야 한다. 이를 위해 도달시간차 및 재료 내부의 속도장을 평가하는 기술이 요구된다. 이것은 암석의 표면에서 발진기와 수신기 사이의 변화로부터 추적가능하며 복잡한 수학적인 알고리즘을 필요로 한다. (중략)

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1995.03a
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• pp.67-81
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• 1995

암반 구조체를 해석하기 위해서는 파괴전의 응력-변형률 거동뿐만 아니라 파괴를 구성하는 삼차원 응력 상태를 알아야 한다. 암반의 파괴를 지배하는 조건을 결정하기 위해서는 일반적인 삼차원 파괴기준이 필요하다. 암반의 파괴를 이루는 응력상태를 파악하기 위해 많은 실험적 연구가 수행되었으며 특히 장비의 사용에 있어서 하중 메카니즘과 시료의 경계조건의 개선에 많은 연구가 진행되었다. 암반의 파괴조건을 설명하는 데에는 이러한 기본적인 기준들 이외에도 경험적인 기준들이 사용되어 왔다. Hoek 와 Brown 은 비등방성 재료의 강도에 대해 연구하였고 순수암(intact rock)의 강도에 대한 경험적인 기준을 제안하였다. (중략)

• Journal of the Korean GEO-environmental Society
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• v.25 no.5
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• pp.15-19
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• 2024

This study aimed to develop high-efficiency grouting techniques under deep-depth conditions by experimentally verifying the applicability of various injection materials. Particle size analysis and injection model experiments were conducted with Ordinary Portland Cement (OPC) and Micro Cement (MC) to evaluate the injection performance of each material. Using Barton's Cubic Network theory, the rock fracture spacing was calculated for domestic deep-depth standards, specifically below 40 meters underground. The analysis of particle size passability under selected conditions showed that MC could pass through the rock fracture gaps, while OPC could not. According to the results of the injection model experiments using experimental devices and area calculation software, OPC failed in injection due to its larger particle size, whereas MC was capable of injection even under high-viscosity conditions. Based on these findings, the study quantitatively and visually derived the applicability of grouting materials under deep-depth conditions, and high-viscosity MC material is expected to be effective for waterproofing enhancement in deep-depth rock fracture surfaces.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.118-121
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• 2002

항만시설의 기본재료로서 가장 널리 사용되고 있는 피복석 (Rock armor)의 경우 저렴하며, 구입이 용이하다는 장점 때문에 여러 시설물에 적용되어 왔다. 그러나 계속되는 개발로 인해 석재원도 그 한계에 도달했기 때문에 더 이상 저렴한 재료라고 할 수도 없으며, 무엇보다 난 개발로 인한 국토의 훼손과 이에 따른 비난의 여론으로 인해 피복석의 사용이 제한을 받고 있다. (중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.161-171
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• 1993

The aim of this study is to provide the stress-strain behavior of hardening geological materials such as rock or concrete on three dimensional spaces by using Desai model based on plastic theory. To validate proposed model, truly triaxial tests with high pressure under variety of stress paths in which three principal stresses were controlled independently using concrete materials were performed. The main results are summerized as follows: 1. Various stress paths for hardening materials used are satisfactorily explained by performing the truly triaxial test with high pressure. This is very important to investigate constitutive equations for materials like rock or concrete. 2. Since the proposed yield function is continuous, it avoids the singularity point at the intersection of two function in the previous models, thus, reducing the difficulties for computer implementation. 3. Analytic predictions for yielding behavior on $J_1-{\sqrt{J_{2D}}}$ octahedral and triaxial plane, as well as volumetric strain and stress-strain behavior agree well with experimental results.

• The Korean Journal of Malacology
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• v.28 no.3
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• pp.187-196
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• 2012

Recently, for the purpose of constructing artificial ecosystem, the public aquarium and experimental mesocosm systems are receiving attention. To design and establish an aquarium and mesocosm system, there is need of several materials for simulating the environment, such as sediments, rocks, and plants. Expecially for sessile mollusks, there must be proper materials to which sessile invertebrates can adhere. Nowadays, many aquariums and mesocosm systems are using dead coral skeletons for sessile mollusks. This study was proceeded to have data on the effect of dead coral skeletons on water qualities with the experiment on the environmental factors. For this purpose, I made glass tank for experiment, chose two types of dead coral skeletons imported from the Indonesia and observed the change of water qualities and decomposition efficiency of TAN (total ammonia-nitrogen), nitrite ($NO_2{^-}$) and nitrate ($NO_3{^-}$). As a result, the lager the surface area was, the more TAN, nitrite and nitrate decomposition rate increased. In addition, coral skeletons covered with crustose algae and bacteria in the tank showed faster TAN, nitrite and nitrate removal rate and stabilization. Accordingly, this experiment suggested that dead coral skeletons could be used as a sub filter for the closed system as well as an adhering plate.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.3
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• pp.205-217
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• 2006

Rock and discontinuities are main factors consisting of a rock mass and the physical properties of each factor have direct effects on the mechanical stability of artificial structures in the rock mass. Because physical properties of the rock and discontinuities change a lot according to the size of test materials, a close attention is needed when the physical properties, obtained from laboratory tests, are used for the design of field structures. In this study, change of physical properties of intact materials due to the change of their size are studied. Six kinds of artificial materials including crystal, instead of an intact rock, are adopted for the study to guarantee the homogeneity of specimen materials even with relatively large size. Uniaxial strength and Young's modulus of each artificial material are checked out for a size effect and compared with the predicted values by Buckingham's theorem - dimensional analysis. A numerical analysis using PFC (Particle Flow Code) is also applied and primary factors influencing on the size effect are investigated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.161-182
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• 2018

We carried out a series of linear cutting machine tests to assess the cutting performance of a pick cutter in sedimentary rock. The specimens were Linyi sandstone from China and Concrete (rock-like material, conglomerate). Using the small scaled LCM system, we estimated the cutter force and specific energy under different cutting conditions. The cutter forces (cutting and normal) increased with penetration depth and cutter spacing in two rock types, and it was affected by the strength of specimens. On the other hand, the ratio of the peak cutter force to the mean cutter force was influenced by cutting characteristic and composition of rock rather than rock strength. The cutting coefficient was affected by the friction characteristic between rock and pick cutter rather than the cutting conditions. Therefore, the optimal cutting angle can be determined by considering of cutting coefficient and resultant force of pick cutter. The optimum cutting condition was determined from the relationship between the specific energy and cutting condition. For two specimens, the optimum s/p ratio was found to be two to four, and the specific energy decreased with the penetration depth. The result from this study can be used as background database to understand the cutting mechanism of a pick cutter, also it can be used to design for the mechanical excavator.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.59-69
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• 2000

Acoustic emission is n burst of microseismic waves generated by microscopic failure due to deformation in materials. The study on the detection of initiation and propagation of microcracks from acoustic emission measurement is very important for the evaluation of the stability of underground rock structures by the nondestructive letting method. In this study, acoustic emission was measured under uniaxial stiffness loading test used to obtain the complete stress-strain curves of marble and concrete used as reinforced materials of rock structures. The analysis of acoustic emission parameters and source location were performed to discuss the characteristics of the deformation and failure behavior of rock and concrete. And acoustic emission was measured under cyclic loading test to verify the Kaiser effect associated with the damage of materials, in situ stress of rock, and stress history of concrete structure.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.313-325
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• 2006

In this study, scaled model tests were performed to investigate the deformation behaviors around tunnels located in anisotropic rocks. Fifteen types of test models which had respectively different joint angles and rock pressure conditions were made, where the modelling materials were the mixture of sand, plaster and water. All of the tested models showed the shear failure mechanism at the stress-concentrated regions and sliding phenomena according to the joint planes. The direction of joint inclination turned out to have great effect on the tunnel deformation behaviors. The models of joint inclination less than $30^{\circ}$ showed considerable floor heavings. The model of $50^{\circ}$ joint inclination showed the least tunnel convergence among the tested models regardless of rock pressure condition, so that it was thought as the most stable model. Furthermore, the failure mechanisms and deformation behaviors of tunnel models were strongly dependent on the coefficient of rock pressure.