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

• Journal of the Korean GEO-environmental Society
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• v.1 no.1
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• pp.57-63
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• 2000

Volume change of the dredged soils is composed of loss amount of the soil particles flowing over an outflow weir with water and settlements due to both the self-weight consolidation in reclaimed layer and the desiccation at the surface of reclaimed layer. In order to estimate the amount of soil particles flowing over an outflow weir with water, the breakage theory and the results of hydrometer analyses. To verify a validity of the proposed procedure, evaluated loss ratio is compared with various estimates from the other existing methods.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.692-705
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• 2018

Ground vibration is one of the remarkable issues in tunnel blasting. In recent studies, to improve the fragmentation with reduction of ground vibration in tunnel blasting, a vibration-controlled blasting method with artificial cutting slot near the center-cut holes has been suggested. This study examines the effect of the different arrangement of artificial cut-slot on the vibration reduction and fragmentation by performing the full-scaled concrete block blast experiments and the numerical simulations with 3D-DFPA. The results show that the existence of artificial slot contributes to the improvement of vibration reduction, blast fragmentation and the efficiency of the cutting slot blast. It can be explained that the artificial slot play a free surface role and should decrease the burden between the cut holes. Crater volumes of the blasted concrete blocks were measured by 3-dimensional digital image analysis and compared with the ideal standard crater volume which can be calculated by theoretical standard blast design method. As a result, the ratio of burden and hole diameter which should achieve the standard crater in the cut-hole blasting were suggested.

• Journal of the Korean GEO-environmental Society
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• v.3 no.1
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• pp.67-77
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• 2002

Volume change of the dredged soils is composed of the volume loss of soil particle flowing over an outflow weir with water and settlement due to both the self-weight consolidation in reclaimed layer and the desiccation at the surface of reclaimed layer. In order to estimate the amount of soil particles flowing over an outflow weir with water, the evaluation procedure of loss ratio of the dredged soils is proposed in the present study based on the Marsal's modified breakage theory and the results of hydrometer analyses. To verify a validity of the proposed procedure, evaluated loss ratio is compared with results from the other existing methods. The model test results and those of field test were compared and analyzed. Also, the variation of soil loss ratio was examined through the model test in the lab.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2005.05a
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• pp.375-379
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• 2005

본 연구는 ${\beta}-galactosidase$와 phytase활성이 높은 균주의 선발을 목적으로 수각 미생물들을 Kefir와 자연환경에서 분리하여 효소활성을 측정하였다. 배양한 유산균과 효모 균체액을 French pressure cell press로 세포를 파쇄하였을 때, 각 미생물의 단백질농도는 효모보다 유산균이 높은 것으로 나타났다. ${\beta}-galcactosidase$의 비활성은 Kluyveromyces maxiranus와 Candida utilis를 제외하고는 대부분 $0.80{\sim}0.89\;umol/min/mg$ 사이였다. 체적활성의 경우는 Lactobacillus paracasei 및 Lactobacillus rahmnosus, Enterococcus faecium이 각각 15.9 및 14.5, 14.5 umol/ml를 기록하여 ${\beta}-galcactosidase$의 추출재료로 우수하였다. phytase의 비활성은 Lactobacillus paracasei 와 Enterococcus faecium이 0.032와 0.038 umol/min/mg로 가장 높았다. 체적활성의 경우는 Lactobacillus paracasei가 35.12 umol/ml로 가장 높았다. 결론적으로 ${\beta}-galactosidase$와 phytase의 생산측면에서 이용한 미생물중에서는 Lactobacillus paracasei가 가장 우수한 것으로 사료되었다.

• Journal of the Korean Institute of Gas
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• v.25 no.1
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• pp.20-29
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• 2021

During multi-stage fracturing in a low permeable shale formation, stress interference occurs between the stages which is called the "stress shadow effect(SSE)". The effect may alter the fracture propagation direction and induce ununiform geometry. In this study, the stress shadow effect on the hydraulic fracture geometry and the well productivity were investigated by the commercial full-3D fracture model, GOHFER. In a homogeneous reservoir model, a multi-stage fracturing process was performed with or without the SSE. In addition, the fracturing was performed on two shale reservoirs with different geomechanical properties(Young's modulus and Poisson's ratio) to analyze the stress shadow effect. In the simulation results, the stress change caused by the fracture created in the previous stage switched the maximum/minimum horizontal stress and the lower productivity L-direction fracture was more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than the relatively ductile Eagle Ford shale, the fracture width in the former was developed thicker, resulting in the larger fracture volume. And the Marcellus shale's Young's modulus is low, the stress effect is less significant than the Eagle Ford shale in the stage 2. The stress shadow effect strongly depends on not only the spacing between fractures but also the geomechanical properties. Therefore, the stress shadow effect needs to be taken into account for more accurate analysis of the fracture geometry and for more reliable prediction of the well productivity.

• The Journal of Engineering Geology
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• v.15 no.3
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• pp.349-363
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• 2005

Many Quaternary faults are recognized as thin gouge and narrow cataclastic zone juxtaposing the Bulguksa granite and Quaternary deposit bed in the eastern block of the Using Fault, Korea: Gaegok 1, Caegok 2, Singye, Madong Wonwonsa and Jinhyeon faults. This study was performed to calculate chemical change, volume change, silica loss and fluid-rock ratio taken place in gouge zones of these Quaternary faults using XRF, XRD, EPMA. The chemical compositions of fault rocks reveal that the fault gouges are depleted in $SiO_2,\;Na_2\;O,and\;K_2O$ and enriched in $Al_2O_3,\;Fe_2O_3,\;P_2O_5,\;MgO,\;MnO,\;CaO,\;and\;LOI(H_2O+CO_2)$ relative to protoliths. The fact that there is enrichment of relatively immobile elements and depletion of the more soluble elements in the fault gouges relative to protoliths can be explained by fluid-assisted volume loss of $56\%$ for Caegok 1 fault, $22\%$ for Caegok 2 fault,$34\%$, for Singye fault, $8\%$ for Madong fault, $2\%$ for the Wonwonsa fault and $53\%$ for the linhyeon fault. Madong fault and Wonwonsa fault where ratios of the volume change, silica loss and fluid-rock are low might have acted as a closed system for fluid activity, whereas Caegok 1 fault and Jinhyeon fault with high ratios in those factors be an open system. The volumetric fluid-rock ratios range $10^2\sim10^4$ for all faults, being highest in Caegok 1 fault and Jinhyeon fault whose fluid activity was most significant.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.65-70
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• 2005

A low resistivity zone is found in many places such as a fractured fault zone, weathered zone and aquifer. The electrical resistivity is influenced mainly by pore fluid as well as the clay mineral types and contents, Hence, it is very important to understand the relationship between the electrical resistivity and clay contents associated with the low resistivity zone for geotechnical applications such as civil engineering. This study examines the characteristics of clay mineral types and contents to electrical resistivity through sample measurements, and proposes an expression relating the resistivity and clay content. The electrical resistivity is measured for an artificial agar specimen with clay minerals instead of a natural rock. The clay minerals used are Kaolinite and Montmorillonite. Montmorillonite shows remarkably lower resistivity than Kaolinite, although its clay content is fewer than that of Kaolinite. Also, the proposed expression shows a good correlation coefficient as high as 0.89 or more in all clay minerals.

• Journal of the Korean Geotechnical Society
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• v.38 no.4
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• pp.5-20
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• 2022

To analyze the flow and density variations in debris flows, a two-phase finite volume model simplified with momentum equations was constructed in this study. The Hershel-Buckley rheology model was employed in this model to account for the internal and basal friction of debris flows and was utilized to analyze complex topography and entrainments of basal soil beds. In order to numerically solve the debris flow analysis model, a finite volume model with the Harten-Lax-van Leer-Contact method was used to solve the conservation equation for the debris flow interface. Case studies of circular dam failure, non-Newtonian fluid dam failure, and multiple debris flows were analyzed using the proposed model to evaluate shock absorption capacity, numerical isotropy, model accuracy, and mass conservation. The numerical stability and correctness of the debris flow analysis of this analysis model were proven by the analysis results. Additionally, the rate of debris flow with various rheological properties was systematically simulated, and the effect of debris flow rheological properties on behavior was analyzed.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.211-216
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• 2003

굴폐각은 굴양식 후 남는 것으로 남해안에서 주로 집중적으로 발생하는데 연간 28만톤의 발생량 중 상당양은 폐기물로 계속 누적되고 혹은 불법매립되어 환경오염 문제까지 발생시키고 있다. 본 연구에서는 산업폐기물로 분류되는 굴패각을 지반공학 분야에서 활용하기 위한 대안으로 해성점토와 혼합하여 매립재료로써의 적용성을 평가하기 위하여 대형 압밀기를 이용하여 실험을 실시하고 이를 토대로 기초자료를 획득하고자 하였다. 원형의 굴패각을 파쇄하여 입도별로 분류하고 이중 사질토 입경 크기의 재료에 대한 기본 물성치를 평가하고 지반 재료로써의 적용성를 분석하였다. 해성점토 내의 굴패각입자의 혼합비를 변화시켜 만들어진 혼합토에 대한 압밀 실험 결과 굴패각의 혼합율이 증가할수록 체적변화율이 작게 되고, 침하 속도는 빠르게 증가함을 알 수 있었다. 이는 압밀응력의 일부를 굴패각 입자의 골격구조가 부담함으로써 실제 점토부분에 작용하는 압밀응력은 굴패각 혼합율이 증가할수록 작아지는 것으로 판단된다.