• Geomechanics and Engineering
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• 제29권3호
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• pp.219-228
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• 2022

The most widely used parameter to represent rock abrasiveness is the Cerchar abrasivity index (CAI). The CAI value can be applied to predict wear in TBM cutters. It has been extensively demonstrated that the CAI is affected significantly by cementation degree, strength, and amount of abrasive minerals, i.e., the quartz content or equivalent quartz content in rocks. The relationship between the properties of rocks and the CAI is investigated in this study. A database comprising 223 observations that includes rock types, uniaxial compressive strengths, Brazilian tensile strengths, equivalent quartz contents, quartz contents, brittleness indices, and CAIs is constructed. A linear model is developed by selecting independent variables while considering multicollinearity after performing multiple regression analyses. Machine learning-based regression methods including support vector regression, regression tree regression, k-nearest neighbors regression, random forest regression, and artificial neural network regression are used in addition to multiple linear regression. The results of the random forest regression model show that it yields the best prediction performance.

• 자원환경지질
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• 제53권6호
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• pp.729-742
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• 2020

본 연구는 강릉 경포해변에서 약 500 m 거리에 위치한 노출암인 십리바위 주변에 발달한 사질-수중암반 해역에 대한 해저지형자료를 기반으로 해저면영상 및 수중영상과 드론영상 등을 중첩하고 통합 분석하여 동해 북부 연안 서식지의 해저면 환경 특성을 분석하고자 하였다. 십리바위 주변 약 600 m × 600 m 해역을 연구 범위로 선정하고 총 3회 현장자료를 획득하였다. 무인도서인 십리바위는 크게 2 개 노출암과 주변의 여러 돌출암, 노출암 및 수중암초들이 작은 군도 형태를 이루며 형성되어 있다. 십리바위 서쪽으로는 약 200 ~ 300 개의 인공구조물들에 의한 해중림초가 조성되어 있다. 십리바위 주변 약 600 m × 600 m 범위 해역의 수중암반지대는 수심 약 9 m ~ 11 m 범위 내에서 주로 발달해 있으며, 노출된 십리바위 남서쪽 주변으로는 암반지대가 수면 위에서부터 해저면으로 연장되어 발달된 특징을 보이고 있다. 동남쪽의 수심 약 10 m ~ 13 m 해역에는 가장 넓은 수중암반지대가 나타난다. 십리바위 주변해역은 총 4 가지 Type의 해저면 환경 특성이 나타나는데, 수중암반지대(Type I)가 가장 많이 분포하고 있다. 수중암반지대가 발달한 구간 주변이나 사이 및 십리바위 서쪽 방향의 경포해변으로 이어지는 해역은 연성기반의 사질 퇴적층이 나타나며, 조립한 사질 퇴적층이 형성되어 있는 구간(Type II: gS(gravelly Sand)과 세립한 사질 퇴적층구간(Type III: S(Sand)으로 나뉘어 분포하는 특징을 보이고 있다. 십리바위의 서쪽해역 일부 구간에는 인공적으로 형성된 해중림초(TypeIV)가 조성되어 있다. 수중 합성영상 촬영 범위인 십리바위 북서쪽의 약 10 m × 10 m의 수중암반지대에 형성되어 있는 서식지에는 해조류(약 6종), 해면동물(약 2종), 극피동물(약 3종), 연체동물(약 3종) 그리고 척삭동물(약 2종) 등이 우점하여 서식하고 있는 것으로 나타나고 있다. 수면 위 십리바위 조간대 범위에는 두드럭배말, 굵은줄격판담치 등의 연체동물과 거북손, 조무래기따개비 등의 절지동물들이 서식하고 있으며 그 범위와 분포 양상을 해저지형자료와 드론영상을 통합 분석한 자료에서 파악이 가능하다. 본 연구에서 파악하고 확인한 십리바위 및 주변 해역의 서식지 환경 특성은 해저지형자료를 기반으로 해저면영상, 표층퇴적물 시료, 수중영상 그리고 드론영상 등의 자료들을 통합 분석한 결과로 2차원의 분석 자료들을 3차원의 시각화된 주제도로 도출함으로써 해저지형 특성에 따른 서식 환경 특성 연구에 기여하고자 하였다.

• Geomechanics and Engineering
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• 제13권1호
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• pp.173-194
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• 2017

Access shaft is of critical importance to the construction and operation of underground rock caverns. It usually has a relatively large cross-section and penetrates through fill materials, soil layers, and weathered rocks before reaching the caverns excavated in solid bedrock. In this paper, the design and construction of vertical shafts are reviewed in terms of diameter, depth, geological conditions, and support structure. Three shaft alternatives, namely alternative I: vertical shaft with spiral roads, alternative II: upper shaft with spiral roads & lower tunnels, alternative III: plain shaft, are proposed based on a simplified geological profile of the Jurong formation, Singapore. The advantages and limitations of the three types of shafts are discussed. The key issues relating to shaft design and construction, such as the shaft sinking, water control, support structure, are also discussed with a series of solutions provided, such as the sequential excavation, pre-grouting and diaphragm walls.

• Geomechanics and Engineering
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• 제8권4호
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• pp.477-493
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• 2015

In rock drilling, the most important characteristic to clarify is the wear of the drill bits. The reason that the rock drill bits fail with time is wear. In dry sliding contact adhesive wear deteriorates the materials in contact, quickly, and is the result of shear fracture in the momentary contact joins between the surfaces. This paper aims at presenting an overview of the assessment of WC/Co cemented carbide (CC) tricone bit in rotary drilling. To study wear of these bits, two approaches have been used in this research. Firstly, the new bits were weighted before they mounted on the drill rigs and also after completion their useful life to obtain bit weight loss percentage. The characteristics of the rock types drilled by using such this bit were measured, simultaneously. Alternatively, to measure contact wear, namely, matrix wear a micrometer has been used with a resolution of 0.02 mm at different direction on the tricone bits. Equivalent quartz content (EQC), net quartz content (QC), muscovite content (Mu), coarseness index (CI) of drill cuttings and compressive strength of rocks (UCS) were obtained along with thin sections to investigate mineralogical properties in detail. The correlation between effective parameters and bit wear were obtained as result of this study. It was observed that UCS shows no significant correlation with bit wear. By increasing CI and cutting size of rocks wear of bit increases.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.606-613
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• 2004

One of the major forces that causes landslide is the amount of underground water resulted from rainfall and shear strength. As a result of close study on the landslide area affected by typoon Rusa it is observed that many landslides took place at the interface of rock and soil. Based on this observation that shear strength at the interface played a great role in landslide of the hilly area, two shear strengths were measured on different places, one at the interface between rocks and soil and the other just on soil. The two values thus derived were compared and used to review the safety factor for the hilly areas already collapsed. Back analysis was also used to calculate the ground water table according to the different rock types at the time when degradation happened.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2000년도 암반공학문제의 수치해석(Numerical Analysis in Rock Engineering Problems)
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• pp.163-170
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• 2000

절리가 발달한 암반의 거동 특성을 효율적으로 모델링 할 수 있는 수치해석 방법으로서 널리 알려진 개별요소법은 서로 다른 알고리즘에 기초하여 개발된 두 가지 형태의 수치해석 방법으로 발전해 왔다. 본 논문에서는 Plesha 등에 의해 개발된 implicit알고리즘에 기초한 NURBM과 저자에 의해 개발된 explicit 알고리즘에 기초한 CBLOCK을 이용하여 불연속체 암반의 기초적인 거동 특성을 수치해석적으로 고찰하고 모델링상의 문제점들을 비교 분석하였다. CBLOCK 계산 결과에 의하면 절리의 수직 및 접선 강성비는 절리 분포에 따라 불연속체 암반의 안정성을 좌우하는 중요한 지수로서 사용될 수 있는 것으로 나타나고 있으나 NURBM 제산은 상이한 결과를 보였다. 또한 구조물의 안정성과 국부적인 파괴 거동의 해석에서 두 방법이 상이한 결과를 가져올 수 있는 것으로 나타났고 이는 수치해석적 모델링의 제약적 요소로 작용할 수 있음을 보여 주었다.

• 터널과지하공간
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• 제10권3호
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• pp.410-417
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• 2000

절리가 발달한 암반의 거동 특성을 효율적으로 모델링 할 수 있는 수치해석 방법으로서 널리 알려진 개별요소법은 서로 다튼 알고리즘에 기초하여 개발된 두 가지 형태의 수치해석 방법으로 발전해 왔다. 본 논문에서는 Plesha 등에 의해 개발된 implicit 알고리즘에 기초한 NURBM과 저자에 의해 개발된 explicit 알고리즘에 기초한 CBLOCK을 이용하여 불연속체 암반의 기초적인 거동 특성을 수치해석적으로 고찰하고 모델링상의 문제점들을 비교 분석하였다. CBLOCK 계산 결과에 의하면 절리의 수직 및 접선 강성비는 절리 분포에 따라 불연속체 암반의 안정성을 좌우하는 중요한 지수로서 사용될 수 있는 것으로 나타나고 있으나 NURBM 계산은 상이한 결과를 보였다. 또한 구조물의 안정성과 국부적인 파괴 거동의 해석에서 두 방법이 상이한 결과를 가져올 수 있는 것으로 나타났고 이는 수치해석적 모델링의 제약적 요소로 작용할 수 있음을 보여주었다.

• 암석학회지
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• 제3권3호
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• pp.220-233
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• 1994

The granitic rocks in the Poeun - Sogrisan area are composed of the Jurassic Poeun granodiorite and the Cretaceous Sogrisan granites. The latter can be divided into three rock types : coarse-grained biotite granite, porphritic biotite granite and granite porphyry. Petrographical observations, especially focusing on the quartz-feldspar intergrowth texture, suggest that the Sogrisan granites has emplaced at shallower level and crystallized more rapidly than the Poeun granodiorite. The F, Cl contents and the Fe/(Fe+Mg) ratio of biotite and muscovite in the Sogrisan granites are higher than those in the Poeun granodiorite. The anor-thite contents of plagioclase in the Poeun granodiorite are higher then in the Sogrisan granites. Ilmenite in the Sogrisan granites is more enriched in Mn and depleted in Fe than that in the Poeun granodiorite. The whole-rock magnetic susceptibility values (in $10^{-6}$ emu/g unit) are higher in the Sogrisan granites (33~144) than the Poeun granodiorite (9~12), indicating that the former generally belongs to magnetite-series granitoid and the latter to ilmenite-series one. The Sogrisan granites has solidified under more oxidizing environment than the Poeun gra-nodiorite, judging from the whole-rock magnetic susceptibility measurements as well as the chemical compositions of biotite and ilmenite.

• Advances in concrete construction
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• 제7권4호
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• pp.241-247
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• 2019

In this paper the effect of bedding layer on the failure mechanism of rock in direct shear test has been investigated using particle flow code, PFC. For this purpose, firstly calibration of pfc2d was performed using Brazilian tensile strength. Secondly direct shear test consisting bedding layer was simulated numerically. Thickness of layers was 10 mm and rock bridge length was 10 mm, 40 mm and 60 mm. In each rock bridge length, bedding layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $15^{\circ}$. Totally 21 models were simulated and tested. The results show that two types of cracks develop within the model. Shear cracks and tensile cracks. Also failure pattern is affected by bridge length while shear strength is controlled by failure pattern. It's to be noted that bedding layer has not any effect on the failure pattern because the layer interface strength is too high.

• 패션비즈니스
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• 제27권2호
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• pp.1-25
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• 2023

Taq-i Bustan rock reliefs are relatively well preserved among Sassanid relics. They are considered concrete and empirically important materials for studying Sassanian culture. In these rock reliefs, inauguration of various kings and hunting scenes are depicted. Thus, kings' attire and life of the court could be discerned according to eras. The purpose of this study was to investigate Sassanian clothing styles of various social positions by analyzing their clothing depicted in rock reliefs and to improve comprehension of the culture of the Sassanian Dynasty. Methodically, literature studies and artifacts were analyzed in parallel. Data of these two insources were consolidated for comparison. Results of this study are as follows. Since the Sassanian Dynasty succeeded the Parthian Dynasty, the Parthian style of clothing pieces such as tunic and trousers appeared in their attire. Basic types of tunics and trousers did not vary according to social status or age. However, details showed differences in those aspects. In the early Sassanian Dynasty, the dressing style of Rome was adopted. Styles of tunic and trousers featured draperies with many wrinkles and shoes were worn instead of boots. Trousers were tied with laces at ankles and laces were decorated with round clasps, imitating the style used by Kushan kings to the east of Sasanians. External cultural elements were also present in costumes of the Sassanian Dynasty, which played a bridging role for cultural exchanges between Eastern and Western civilizations at the gateway of the Silk Road.