• Explosives and Blasting
• /
• v.23 no.2
• /
• pp.45-56
• /
• 2005

In this study, fracture formation and fracture volume by blasting demolition of model reinforced concrete pillars were compared with various vertical load and influence of reinforced steel bar. The more vertical load increased, the more tensile cracks and vertical direction cracks produced. In vertical load of 2.0ton, tensile cracks on vertical direction were predominantly produced. Generally, the more vertical load increased, the more bending deformation of concrete steel bar decreased. As a result, vertical load was influenced fracture formation of concrete and bending deformation of reinforced steel bar. Reinforced steel bar was influenced fracture volume of concrete. According to vertical load and influence of reinforce steel bar by blasting demolition of reinforced concrete pillars, drilling and blasting pattern may be modified.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.04a
• /
• pp.509-513
• /
• 2004

현장 균열망의 연결성 및 이에 따른 수리지질학적 특성을 규명하기 위하여, 기존의 통상적인 조사 기법을 한 지역에 집적하여 그 결과에 대한 통합해석을 수행하였다. 본 연구에 적용된 조사 방법은 양수시험, 물리검층, 다중심도 수리화학 분석, 전기비저항 토모그래피, 시추 코어 검층 등의 기련 특성 조사와, 추적자 시험, 다중 심도 수직 유향유속 시험 등 구간별 특성 조사 등이다. 이러한 조사 결과 본 조사 지역 내 균열의 전반적인 분포 특성을 확인할 수 있었으며, 각 균열의 수리적 특성에 대한 기본적 특성을 확인할 수 있었다. 특히 추적자 시험과 유향유속 시험 결과를 통해 각 관정간의 균열을 통한 연결성에 대한 중요한 정보를 도출할 수 있었다. 이러한 성과는 추후 percolation, connectivity 등 모델 개념의 현장화를 위한 연구의 선행 연구로서 그 의미를 자리매김 할 수 있을 것이다.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2010.04a
• /
• pp.306-309
• /
• 2010

강철도 플레이트거더교의 경우 일반적으로 레일의 폭보다 거더 사이의 폭이 넓기 때문에 거더에 편심이 작용하게 된다. 이러한 편심 영향으로 거더 내측 상부플랜지에 휨변형이 일어나게 되어, 상부플랜지와 수직보강재 용접이음부에 반복하중에 의한 피로균열이 발생되고 있는 것으로 보고되고 있다. 본 연구에서는 공용중인 강철도 플레이트거더교를 대상교량으로 하여 공용하중에 대한 구조해석을 실시하였다. 대상교량에 대한 현장계측을 기초로 구조모델링을 검증하였고, 검증된 구조모델링을 사용하여 열차하중 하에서의 상부플랜지와 수직보강재 용접연결부에서의 피로균열 보강방안에 대한 구조해석을 실시하였다. 또한 상부플랜지와 수직보강재 용접이음부 상세해석을 통하여 피로균열 발생위치를 확인하고 연결이음부의 적절한 보강방안을 제시하고자 한다.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.4
• /
• pp.27-39
• /
• 2007

This paper investigates numerically characteristics of the fluid flow in spatially correlated variable-aperture fractures under effective normal stress conditions. Spatially correlated aperture distributions are generated by using the geostaistical method (i.e. Turning Bands algorithm). In order to represent a nonlinear relationship between the effective normal stress and the fracture aperture, a simple mechanical formula is combined with a local flow model. Obtained numerical results indicate that the fluid flow is significantly affected by the geometry of aperture distribution varying according to the applied effective normal stress as well as the spatial correlation length of aperture distribution. Moreover, by using results simulated in this study, the modified Louis formula representing the relationship between the effective normal stress and the effective permeability of fracture is proposed.

• The Journal of the Petrological Society of Korea
• /
• v.18 no.2
• /
• pp.115-135
• /
• 2009

We have studied general orientational characteristics of microcracks distributed in Tertiary crystalline tuff from the northeastern part of the Gyeongsang Basin. 108 sets of microcracks on horizontal surfaces of 6 rock samples from Heunghae-eup and Cheongha-myeon, Pohang-si areas were distinguished by image processing. Those microcrack sets show a distinct linear array in 38 images. Whole domain of the directional angle(${\theta}$)-frequency(N) chart for crystalline tuff can be divided into 20 domains in terms of the phases of the distribution of microcracks. From the related chart, microcrack sets show preferred orientation which are coincident with the direction of vertical common joints. Consequently, the potential for macroscopic vertical joints in a rock body can be inferred from the directional angle showing high frequency in each domain of the related chart. This joint pattern is nearly the same in Mesozoic granites from Seokmo-do, Gwanghwa-gun. From the rose diagram for orientations of microcrack in crystalline tuff, orientations of dominant sets of microcracks in terms of frequency orders reflect representative orientations of maximum principal stress acted on crystalline tuff. Meanwhile, orientations of microcracks in crystalline tuff were compared with those of open microcracks in Bulgugsa granites from the southwestern part of the Gyeongsang Basin, and vertical rift/grain planes from Mesozoic granite quarries in Korea. In regional distribution chart, the agreement of distribution pattern between above two types of microcrack sets and vertical planes suggests that microcrack systems developed in crystalline tuff probably occur regionally in Mesozoic granites in Korea.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.2
• /
• pp.277-284
• /
• 1993

Interfacial surface crack perpendicular to the surface, which is imbedded into bonded quarter planes under single anti-plane shear load is analyzed. The problem is formulated using Mellin transform, form which single Wiener-Hopf equation is derived. By solving the equation stress intensity factor is obtained in closed form. This solution can be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Journal of the Korean GEO-environmental Society
• /
• v.10 no.1
• /
• pp.5-14
• /
• 2009

This study is to analyze numerically the spatial behaviors of the solute transport in a spatially correlated variable-aperture fracture under the effective normal stress conditions. Numerical results show that the solute transport in a fracture is strongly affected by the spatial correlation length of apertures and applied effective normal stress. According to increasing spatial correlation length, the mean residence time of solute is decreased and the tortuosity and Peclet number (is a dimensionless number relating the rate of advection of a flow to its rate of diffusion) is also decreased. These results mean that the geometry of the aperture distribution is favorable to the solute transport as the spatial correlation length is increased. However, according to the applied effective normal stress is increased, the mean residence time and tortuosity have a tendency to increase but the Peclet number is decreased. The main reason that the Peclet number is decreased, is that the solute is displaced by one or two channels with relatively higher local flow rate due to the increment of contact areas by increasing effective normal stress. Moreover, based on numerical results of the solute transport in this study, the exponential-type correlation formulae between the mean residence time and the effective normal stress are proposed.

• The Journal of the Petrological Society of Korea
• /
• v.17 no.4
• /
• pp.206-221
• /
• 2008

We have studied general orientational characteristics of microcracks distributed in Bulgugsa Granites of southwestern Gyeongsang Basin. Microcracks of 131 sets, which were developed on horizontal surfaces of II rock samples collected from Sacheon-Gosung, Geoje-si and Namhae-gun areas, were distinguished by image processing. Then, 45 sets with a distinct linear array on image were sorted out. These microcracks can be comparable with vertical grain planes. Orientations of these microcracks were compared with those of vertical rift and grain planes developed in Cretaceous and Jurassic granites of Korea. In the distribution chart, the agreement of the distribution pattern between microcracks of 45 sets and above vertical planes suggests that microcrack systems developed all over the study area also occur regionally in Cretaceous and Jurassic granites of Korea. Whole domain of the directional angle-frequency chart can be divided into 20 domains in terms of the phases of the distribution of microcracks. Meanwhile, 18 domains from 45 sets of microcracks were compared with the maximum principal stress orientations suggested from previous studies. The majority of maximum principal stress orientations pertain to domain $1{\sim}2$, $5{\sim}6$, $11{\sim}15$, $17{\sim}18$ and $19{\sim}20$, and these domains are coincident with the orientation of the 1st and 2nd-frequency orders represented in a rose diagram for 45 sets of microcracks. Representative orientations of open microcrack reflect the maximum principal stress orientations suggested in previous studies.

• Journal of the Korean Society of Groundwater Environment
• /
• v.6 no.1
• /
• pp.1-7
• /
• 1999

This study deals with linear flow pattern in steady-state or transient dual-porosity media with a vertical geologic structure such as fault, fracture zone, etc. A pumping well is located in the vertical structure of infinitesimal or finite width with high hydraulic conductivity and negligible specific storage. Selected type curves on a pumping well and observation wells in the fractured system and the matrix block are provided. The type curves on the pumping well considers both wellhole and well-loss effects.

• The Journal of the Petrological Society of Korea
• /
• v.17 no.4
• /
• pp.238-244
• /
• 2008

The west stone pagoda of Gameunsa temple site(National Treasure No. 112) has been seriously damaged by surface weathering, and conservation treatment is needed. In the second story body stone, vertical cracks developed parallel to the main compressional axis. The vertical cracks seem to grow much more with the compression. Chemical and biological weathering along the vertical cracks could have enhanced the crack growth. In the third story capstone, the surface cracks strike toward NE and NW directions, which are intersecting each other. In the eastern and southern parts of the third story capstone, lots of vertical cracks develop along the lines from the axial center to outer rim, whereas horizontal cracks are easily observed at the outer rim of the capstone. On the other hand, a few horizontal cracks develop in the western and northern parts of the third story capstone. This fact indicates that the compression along the vertical axis is not uniform in direction. The west stone pagoda leans toward the east and the south, so it is considered that compression by deviatoric stress prevailed at these directions.