• Geomechanics and Engineering
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• 제9권3호
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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.

• 암석학회지
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• 제5권1호
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• pp.21-34
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• 1996

Contact-metamorphosed calc-silicate hornfels of the Hwanggangni formation adjacent to Daeyasan granite in Goesan are characterized by the mineral assemblages. tremolite-clinozoisite-alkali feldspar-calcite, diopside-grossular-vesuvianite, and wollastonite-diopside-phlogopite-grossular-vesuvianite, indicating low $X_{CO_2}$ condition during contact metamorphism. Two trends of fluid-rock interactions are recognized; combination of infiltration and buffering in the outer portion of the aureole and fluid-dominated behavior in the most part of the aureole. Modal abundance of diopside produced during metamorphism was measured in order to estimate fluid/rock ratios and permeabilities with the assumption that equivalent volume of fluids estimated from the fluid/rock ratios flow through the rock body. The calculated fluid/rock rations and permeabilities range from 0.6 to 9 and $10^{-19}$ to $10^{-17}$ meabilities in the calc-silicate hosted contact aureoles and expected values during progressive metamorphism by theories.

• 설비공학논문집
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• 제11권5호
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• pp.588-597
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• 1999

Sokkuram grotto, a UNESCO cultural heritage in Kyongju Korea, was originally covered with crushed rocks over its dome with ventilating holes. The grotto was perfectly preserved for more than 12 centuries until the upper structure was replaced with a concrete dome in the early 20th century to protect from total collapse. Since then, heavy dew formed on the granite surface to seriously damage the sculptures until it was further remodeled with air-conditioning facilities in the 60s. It is considered that the original upper porous structure had a dehumidifying capability. This research is made to unveil the dehumidifying mechanism of the rock layer during the rainy season in that area. A rock layer and a concrete layer are tested in a temperature/humidity-controlled room. No dew formation is observed for the two specimen for continued sunny days or continued rainy days. However, heavy dew formed on the concrete surface for a sunny day after long rainy days. It is thought that the sun evaporates water on the ground and dew is formed at the surface as the highly humid air touches the yet cold concrete. On the contrary, no dew formation is observed for the rock layer at any time. Even in the above worst situation, air flows downward through the cool rock layer and moisture is removed before reaching inside. Temperature measurement, flow visualization, observation of dew formation and measurement of air velocity are made to verify the mechanisms.

• Geomechanics and Engineering
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• 제23권2호
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• pp.127-137
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• 2020

To study the reverse fault formation process and the stress evolution feature, a simulation test system of reverse fault formation is developed based on the analysis of reverse fault formation mechanism. The system mainly consists of simulation laboratory module, operation console and horizontal loading control system, and data monitoring system. It can represent the fault formation process, induce fault crack initiation and simulate faults of different throws. Simulation tests on reverse fault formation process are conducted by using the simulation test system: horizontal loading is added to one side of the model. the bottom rock layer cracks under the effect of the induction device. The crack dip angle is about 29°. A reverse fault is formed with the expansion of the crack dip angle towards the upper right along the fracture surface and the slippage of the hanging wall over the foot wall. Its formation process unfolds five stages: compressive deformation of rock, local crack initiation, reverse fault penetration, slippage of the hanging wall over the foot wall and compaction of fault plane. There is residual structural stress inside rock after fault formation. The study methods and results have guiding and referential significance for further study on reverse fault formation mechanism and rock stress evolution.

• 지질공학
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• 제2권2호
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• pp.173-200
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• 1992

대구시 중심부의 지하수는 신천과 범어천 등의 하천수를 주 공급원으로 하기 때문에 그 수질은 이들 하천수의 영향을 많이 받고 있다. 그리고 하천의 수질은 하천이 발원한 지역의 암류와 밀접한 관계를 가지므로 안산암가 몬조니암을 상류에 두고 있는 신천과 범어천의 수질은 이들 화성암류의 영향을 받게 된다. 마찬가지로 반야월층이나 함안층에서 발원하는 하천의 수질은 이들 퇴적암류의영향을 받고 있다. 본 역 상류천이 pH는 하천이 발원하는 암류에 따라 차이를 보이는데 화성암류(안산암, 몬조니암)지역은 약산성 - 중성이고 퇴적암류지역은 약알카리성을 띤다. Ca와 Mg 함량은 퇴적암류지역 하천이 화성암류지역 하천보다 현저히 높으나, Na 함량은 퇴적암류지역 하천이 화성암류지역 하천보다 약간 높은 경향을 보이며, K 함량은 암산암지역보다 반야월층이 오히려 약간 낮은 경향을 띈다. 중금속원소의 함량도 역시 주택지대와 공장지대가 있는 퇴적암지역 하천이 비오염 화성암류지역 하천보다. 높은 경향을 띤다. $NO_3-N$ 함량도 퇴적암류지역 하천이 화성암류지역 하천보다 높다. 지하수의 수질은 암층의 여과작용에 의하여 오염하천수에 비하면 금속이온의 함량이 현저히 낮으나 화성암지대의 오염되지않은 상류천 수질에 비하면 많이 오염되어 있다. 그리고 오염의 정도도 주택지대가 있는 반야월층지역보다 공장지대가 있는 함안층지역에서 심하다. pH는 반야월층과 함안층지역이 비슷하나 주원소의 함량은 함안층지역이 반야월층지역 보다 대체로 높은 경향을 보인다. 중금속원소의 함량은 양 지층의 지역간에 근소한 차이를 보이나, 오염이 심한 공단천과 달서천 부근의 지하수는 함안층 지하수는 Cu, Pb, Zn, Mn, Fe의 함량이 높다.

• 한국지구과학회지
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• 제36권6호
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• pp.543-552
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• 2015

본 연구는 경상북도 구미시 천생산 지역에서 발달하는 타포니를 대상으로 암석의 풍화 과정 및 타포니의 형성 과정을 분석하고 있다. 연구지역의 타포니 발달은 조립질 퇴적암인 역암과 역질사암에서 발생빈도가 높으며 타포니의 발생은 역의 이탈 및 박리가 발생한 지점에서부터 시작되는 것으로 추정된다. 지형적으로 산지의 남사면 암석 노출지에서 타포니의 집중적 발달이 관찰되는데, 이는 겨울철 기계적 풍화와 여름철 화학적 풍화의 진행이 상대적으로 높은 환경적 조건에 따른 것으로 해석된다. 타포니가 발달한 암석 표면에서 측정한 함수율의 분포 특성은 타포니 발생 지점이 주변에 비해 높은 함수율을 명확히 보여주고 있어 암석 내의 수분은 어떤 기제로든 타포니 발생에 상당한 영향을 끼치는 것으로 판단된다. 타포니 내에서 확인되는 풍화 침전물 및 이차광물에 관한 분석은 후속 연구로 현재 진행 중에 있다.

• Structural Engineering and Mechanics
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• 제68권1호
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• pp.95-101
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• 2018

The low rate of penetration and short lifetime of drilling bit served as the most common problems encountered in hard formation drilling, thus leading to severe restriction of drilling efficiency in oil and gas reservoir. This study developed a new local impact drilling method to enhance hard formation drilling efficiency. The limitation length formulas of radial/lateral cracks under static indentation and dynamic impact are derived based on the experimental research of Marshall D.B considering the mud column pressure and confining pressure. The local impact rock breaking simulation model is conducted to investigate its ROP raising effect. The results demonstrate that the length of radial/lateral cracks will increase as the decrease of mud pressure and confining pressure, and the local impact can result in a damage zone round the impact crater which helps the rock cutting, thus leading to the ROP increase. The numerical results also demonstrate the advantages of local impact method for raising ROP and the vibration reduction of bit in hard formation drilling. This study has shown that the local impact method can help raising the ROP and vibration reduction of bit, and it may be applied in drilling engineering.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.253-260
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• 2002

Chemical weathering processes related with mineralogical characters and ground water condition are very essential engineering problems in soluble rock masses. Detailed geological mapping were performed and 8 samples were collected from the 2 formations including various rock faces to deduce the possibility of the limestone cavity formation and their mechanism. Petrological descriptions and various petro-mineralogical experiments such as XRD analysis, clay mineral analysis, absorptivity test, impurity analysis were conducted to evaluate the cavity making processes. Laboratory solubility test for rock specimen were also carried out under the strong acid (pH=1) condition. From the experimental data and geological mapping data, it is found that the formation of limestone cavities in limestones are strongly related with geological structures such as beddings, cleavages and the contents of impurities rather than CaCO$_3$contents. In case of dolomites, rock textures, grain size, amounts and types of clay minerals as well as geological structures are major controlling factors of cavity forming processes

• 터널과지하공간
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• 제16권1호
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• pp.38-49
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• 2006

복공식 LNG 지하저장기지 건설을 위해서는 암반역학, 열역학 및 수리지질특성과 관련된 여러 가지 기술이 요구되며, 이러한 기술의 적용성을 입증하기 위한 일환으로 대전에 Pilot cavern을 건설하였다. 이 논문에서는 Pilot cavern에 적용된 기술 중 배수시스템 평가과 Ice ring모사에 관한 수치해석 연구를 수행하였다. 대수층관점의 Modflow와 유동시스템 관점의 Seep/W 해석을 통해 적용된 배수시스템이 효율적으로 작용하였음을 확인하였다. Ice ring 형성은 열전달과 지하수 흐름의 상호작용을 통해 모사될 수 있는데, 이에 대한 모사를 위해 Temp/W-Seep/W 프로그램을 이용한 냉열수리 연동해석을 수행하였다. 이러한 해석을 통해 Ice ring의 형성 위치를 추정 할 수 있었고, Ice ring형성에 지하수 유동 속도 및 방향이 영향을 크게 미친다는 것을 확인했다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.999-1008
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• 2009

A series of sedimentary rocks which are formed in the Tertiary are distributed around Samcheok(Samcheok-Pukpyoung basin), Younghae(Younghae basin), Pohang(Pohang basin), Gyeongju(Yangnam basin), Ulsan(Ulsan basin), Jeju(Seogyuipo formation) in the southern region of the Korean Peninsula. This study concerned with geological, geophysical, geotechnical properties of the unconsolidated rocks in the Pohang area. A consolidated rocks are classified as hard rock - soft rock - weathered rock - residual soil follows in degree of weathering. But unconsolidated rocks has soil properties as well as rock's at the same time. The results of field excursion, boring, borehole-logging, rock testing, geophysical survey, laboratory test are soft rock range, but the durability of the rock until the residual soil from the weathered rock. We accomplished the rock mass classification of the unconsolidated rocks.