주기적으로 침수되는 퇴적암의 풍화특성

이석훈,김수진 한국광물학회 2004 광물과 암석 (J.Miner.Soc.Korea) Vol.17 No.1

울산시 사연댐 상류에 위치하여 주기적으로 침수되는 퇴적암의 풍화특징을 연구하였다. 현장조사, 전자현미분석기, X-선 회절분석기 및 X-선 형광분석기를 이용하여 암석의 풍화조직 및 광물의 조성변화 조사를 통해 주기적으로 침수되는 암석의 기계적 및 화학적 풍화양상을 연구하였다. 수장암석의 풍화작용은 퇴적충리와 수직방향으로 발달한 파쇄대 및 균열과 박리현상과 같은 기계적 풍화작용이 현저하다. 이러한 물리적인 풍화현상은 물과 암석과의 접촉면적을 넓혀 화학적 풍화작용을 가속화시킨 결과 풍화대와 약풍화대에서 석영을 제외한 거의 모든 광물이 용해작용 또는 변질 작용을 받았으며, 특히, 탄산염광물의 용해작용이 현저하여 약풍호대에서 조차 방해석이 완전히 용해되어 빈 공간으로 남아있다. 그러나 점토광물과 같은 이차광물의 형성은 미약한 특징을 보인다. 이 지역의 암석은 일정기간 동안 물에 잠긴 상태로 유지되고, 동결과 해빙이 반복됨으로써 물리적 풍화작용이 상대적으로 빠르게 진행되어 물의 침투가 용이한 투수성 구조를 형성하였고, 그 결과 탄산염광물의 용해작용이 급속하게 일어났다. 자유로운 물의 순환으로 인하여 용해된 원소들이 점토광물과 같은 풍화광물로 침전되지 않고 용탈됨으로써 암석조직이 이완되어 풍화작용이 가속되었다. 퇴적암중 풍화에 극히 약한 탄산염광물의 높은 함량이 강한 화학적 풍화작용의 주요인으로 보인다. The weathering characteristics of periodically submerged sedimentary rocks in the Sayeon dam, Ulsan was examined by field work, electron probe micro-analysis, X-ray diffraction, and X-ray fluorescence spectrometry. Analysis of fracture zone and exfoliation showed the submerged sedimentary rocks have undergone severe mechanical weathering. Mechanical weathering in the water-rock interface accelerated chemical weathering, such as dissolution and alteration of the most of minerals except for quartz in the weathering zone. The dissolution of carbonates specially calcite, is remarkable creating the cavities, whereas formation of minerals including clay minerals is not active. The weathering characteristics of periodically submerged sedimentary rocks in the Sayeon dam, Ulsan was examined by field work, electron probe micro-analysis, X-ray diffraction, and X-ray fluorescence spectrometry. Analysis of fracture zone and exfoliation showed the submerged sedimentary rocks have undergone severe mechanical weathering. Mechanical weathering in the water-rock interface accelerated chemical weathering, such as dissolution and alteration of the most of minerals except for quartz in the weathering zone. The dissolution of carbonates specially calcite, is remarkable creating the cavities, whereas formation of minerals including clay minerals is not active. The sedimentary rocks have been periodically submerged for a certain period of time, and have repeated freezing and thawing. This mechanical weathering favored infiltration, which accelerated mineral dissolution. The high content of easily soluble carbonate of the sedimentary rocks is likely the major cause of intense chemical weathering. The dissolved elements within the infiltrated water interrupted the occurrence of clay and weathering minerals, and expend fractures by infiltrated water accelerated weathering process.

Evaluation of Chemical Weathering Indices Using Correspondence Analysis

( Yufang Tan ),( Lihui Li ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Chemical weathering indices are used to quantify the extent of rock weathering. Several chemical weathering indices have been proposed that account for the mobility of major element oxides in rocks, but are critically dependent on the parent rock composition and have limited application to certain rock types. Therefore, comprehensive and statistical evaluation of index applications is helpful in the choice of a proper index. In this study, we determined correlations between 11 commonly used indices and rock types using correspondence analysis (CA). The database is about 163 samples of 10 rock types and their chemical weathering indices derived from reported literatures. The CA analysis yields two orthogonal principle factor axes (F1/G1 and F2/G2), which capture 37.7% and 21.2% of total variability, respectively. These two factor axes make up a factor-loading graph, which indicate that certain indices including the chemical index of alteration (CIA), chemical index of weathering (CIW), loss on ignition (LOI), and weathering potential index (WPI) are suitable for weathering grade classification of most rocks. The factor loadings of rock samples of variable weathering grade assemble in three groups in the factor-loading graph and most of them form a linear trend, which is related with mineralogy of the parent rock and the weathering environment. The factor-loading graph has a visual presentation of weathering trends of various rock types, and correlation between weathering indices and rock types. All of the merits suggest that CA is a powerful method for evaluating the applicability of chemical weathering indices.

옥천대지역 -제천·금산·김천- 에 분포하는 화강암 및 화강 편마암의 풍화분류에 관한 고찰

우익(Ik Woo),박혁진(Hyuck-Jin Park) 대한자원환경지질학회 2004 자원환경지질 Vol.37 No.3

국내에 분포하는 화강암 및 화강편마암의 풍화 등급에 따른 정성적ㆍ정량적인 분류법을 고찰하였다. 정성적인 분류는 암석의 외적 관찰과 상대적 강도 측정에 의존하는 주관적인 방법이 사용되었으며, 정량적 분류를 위하여서는 실내 외 실험을 통한 암석의 기본적 물성을 이용한 풍화 지수를 사용하여 암석을 풍화에 따라 분류를 하였다. 풍화 분류 기준은 기존의 여러 문헌에서 얻은 방법 및 본 연구에서 사용한 방법을 추가 혹은 수정하여 제시하였다. 또한, 풍화 등급별로 채취된 암석 시료의 박편 관찰을 통하여 암석 구성 광물의 변화와 미세절리발달을 풍화 등급별로 관찰하였다. 풍화에 약한 광물인 사장석 및 흑운모의 화학적 풍화 정도는 풍화가 진행됨에 따라 점점 발달됨을 살펴볼 수 있었으며, 신선한 암석에서도 사장석 및 흑운모의 풍화가 어느 정도 발달되어 있음을 살펴볼 수 있었다. 서로 다른 풍화 등급의 암석 분말에 대한 XRD분석을 수행하여, 암석 구성 광물의 풍화에 따른 동적변화를 살펴보았다. 즉, 풍화에 약한 광물의 비율이 풍화가 진행됨에 따라 감소되며, 풍화에 강한 광물의 비율은 반면에 증가되는 경향을 보여주고 있다. 풍화의 정량적인 분류를 위해서 여러 암석 물성 값을 이용한 Fookes et al.(1988)이 제안한 RDIsq 및 본 연구에서 제안한 Ia(Woo, 2003)를 사용하였다. 그 결과, 연구대상 암석의 신선한 풍화등급 F는 I/sub a/>7, 약간풍화 SW는 3.5<Ia<10, 보통풍화 MW는 1.0<Ia<6.0 그리고 심한풍화 HW는 Ia<2.5로 분류될 수 있다. 실내ㆍ외 실험을 통한 풍화에 따른 국내 화강암 및 화강편마암의 물리적 혹은 공학적 물성 값을 고려하여 본 풍화 지수들의 범위를 결정하여 간편하고 빠르게 암석의 풍화 등급을 결정할 수 있게 하였다. A study on the weathering grade classification has been performed for granite and granite gneiss in Korea. The qualitative classification criteria of weathering were reviewed and then modified with field studies for the weathered rock masses. The thin section observations and XRD analyses for the different weathering grades rock samples showed the petrographical and petrophysical difference with respect to the weathering : the proportion of weathering-resistant minerals suck at quartz and orthoclase has a tendency to increase with the development of weathering, but that of weathering-sensible minerals such as anorthite and biotite is decreased. The ranges of physical and mechanical rock properties for different weathering grades were obtained from the laboratory rock tests and field tests for the studied rocks. And then, along with RDIsq(Fookes et al., 1988), the weathering index Ia, (Woo, 2003) has been developed in this study to demarcate the weathering grade. Those two indices rely mainly on the water absorption ratio of rock and on the different rock strength. The range of these weathering indices have been determined with the physical and mechanical rock properties that can be obtained from simple field or laboratory tests in 4 grades Ia > 7 for F, 3.5 < Ia < 10 for SW, 1.0 < Ia < 6.0 for MW and Ia < 2.5 for HW. Consequently, the weathering index could be utilized to classify quantitatively the rock weathering grade, especially for the studied granites and the granite gneiss in Korea.

Evaluation of geomechanical and geochemical properties in weathered metamorphic rocks in tropical environment: a case study from Samanalawewa hydropower project, Sri Lanka

Dashan T. Udagedara,Chiaki T. Oguchi,Jagath K. Gunatilake 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.3

The effect of weathering on changes of physical and mechanical properties of rocks is a prime concern in the perspectives of geology and engineering. These properties have been studied mostly on weathered igneous and sedimentary rocks under humid climates. Studies on weathering of metamorphic rocks, especially under a tropical climate, are rare. This study evaluates change of physical, mechanical, chemical, and mineralogical properties of metamorphic rocks that weather under tropical climatic conditions. Samanalawewa hydropower project area was selected for this study, because rapid weathering of a metamorphic rock (sillimanite garnet gneiss) was observed in the project site. Fresh rocks that are subjected to weathering have reached to completely weathered condition in a time span of less than 25 years in this area. Visually assessed weathering grades were physically and mechanically evaluated using bulk density, equotip hardness, porosity, specific gravity, point load strength, and slake durability tests. Mechanical properties, especially point load strength, change rapidly at the onset of weathering, while chemical properties show significant changes at later stages of weathering. Mineralogical changes such as appearance of secondary minerals are at the latter part of weathering. Physical properties gradually change during weathering. The observed changes in physical, mechanical and chemical properties indicate that their variations during weathering are independent of lithology and climatic conditions.

인공풍화과정에 의한 김해지역 백악기 화강암의 풍화특성에 관한 연구

엄정기(Jeong-Gi Um) 한국암반공학회 2012 터널과지하공간 Vol.22 No.1

It is very difficult to capture the weathering characteristics of rock because of limitation caused by time and space. A new scheme of experiment that includes physical and chemical weathering processes was implemented on Cretaceous granitic rock samples from Kimhae area to investigate the variations of geomechanical properties of deteriorated rocks due to artificial weathering processes. The seismic velocity was found to decrease with increasing artificial weathering cycle. Effective porosity and absorption tend to increase with artificial weathering processes. The amount of deterioration of rock samples depend on pre-test degree of weathering. Effective porosity, absorption and seismic velocity can be used as the measure of weathering characteristics of granite in the study area. Weathering is accelerated by combined effect of physical and chemical weathering processes. The new experimental methodology conducted in this study has strong capability to analyze the weathering characteristics of rocks.

Weathering Properties of Paulownia tomentosa and Pinus koraiensis Woods Heat-Treated in Palm Oil and Air

( Intan Fajar Suri ),( Byantara Darsan Purusatama ),( Jong Ho Kim ),( Go Un Yang ),( Denny Prasetia ),( Muhammad Alvin Savero ),( Se Yeong Park ),( Nam Hun Kim ) 한국목재공학회 2022 한국목재공학회 학술발표논문집 Vol.2022 No.1

This study aimed to evaluate the weathering properties of Paulownia tomentosa and Pinus koraiensis woods heat-treated in palm oil (OHT) and air (AHT) at 180℃, 200℃, and 220℃ for 2 hours. The untreated and heat-treated samples were exposed to UV and water for artificial weathering test according to ASTM G53-96. The artificial weathering test of heat-treated and untreated wood samples was performed by exposing to UV lamps in the QUV accelerated weathering tester (QUV/se Accelerated Weathering Tester, Q-LAB, USA) for 168 h and 336 h. The weathering cycle involved a continuous light irradiation of UV exposure for 2 hours and condensation for 2 hours. Color change and dimensional stability of the weathered samples were determined. Color change was measured by the CIEL*a*b* system (Esteves et al. 2008). Macroscopically, there was hardly shown on color difference in the wood samples before and after weathering. After weathering test, heat-treated wood of both species showed lower total color change than the control samples, and the total color change decreased with increasing treatment temperature. The total color change of OHT wood was smaller than that of AHT wood samples. In both species, the heat-treated wood samples showed higher dimensional stability than the control samples. The volumetric shrinkage of heat-treated wood samples decreased as the temperature increased. The OHT wood samples showed smallest volumetric shrinkage than AHT wood samples. In conclusion, after the weathering test, the OHT wood samples displayed better color and dimensional stability than the AHT wood samples.

수용성 방부처리재의 기상열화 저항성 평가

이명재,이동흡,김규혁 한국목재공학회 2003 목재공학 Vol.31 No.4

수용성 방부처리(AAC, CCA-3, ACQ, CuAz) 소나무 시편의 기상열화에 대한 저항성을 평가하기 위하여 인공촉진열화 방법을 사용하였다. 기상열화에 의한 재색 및 중량변화, 물리적 표면열화, 목재조직의 변화를 종합적으로 고려할 때, AAC 처리시편을 제외한 ACQ, CCA, CuAz 처리시편은 기상열화에 대한 저항성이 있음을 알 수 있었다. 이러한 몇몇 방부처리재가 기상열화에 대하여 저항성을 나타내는 요인탐색을 위해 기상열화 산물을 분석하였는데, 그 결과, ACQ, CCA, CuAz 처리시편에서는 낮은 리그닌 함량이 측정되어 기상열화 저항성을 가지는 처리시편은 리그닌 열화가 적게 일어남을 나타냈다. 이는 방부제 유효성분이 목재 주성분 중 기상열화에 민감한 리그닌 구조에 정착함으로써 리그닌 열화에 대한 저항성이 발현되었기 때문으로 판단된다. This study was carried out to evaluate the weathering durability of waterborne preservative (AAC, ACQ, CCA, CuAz) treated Japanese red pine (Pinus densiflora S. et Z.) sapwood samples by accelerated weathering, and to find out the factor of stability. When considered the color changes, weight losses, surface degradation, and microstructure changes due to weathering, ACQ-, CCA-, and CuAz-treated samples were durable against weathering; the weathering durability of AAC-treated samples was poor and similar to untreated controls. The lignin content in aqueous extracts collected from ACQ-, CCA-, and CuAz-treated samples during weathering was lower than from untreated and AAC-treated ones. From these findings, we might concluded the weathering durability of ACQ-, CCA-, and CuAz-treated samples was enhanced by the fixation of preservative component(s) onto the lignin structure, which is very susceptible to weathering.

Physical and Chemical Weathering Indices for Biotite Granite and Granitic Weathered Soil in Gyeongju

( Jae-doo Ban ),( Seong-woo Moon ),( Seong-won Lee ),( Joo-gong Lee ),( Yong-seok Seo ) 대한지질공학회 2017 지질공학 Vol.27 No.4

Physical weathering caused by external forces and chemical weathering caused by the decomposition or alteration of constituent materials are the two factors that dominate the mechanical properties of rocks. In this study, a field investigation was undertaken to identify the physical and chemical weathering characteristics of the biotite granite and granitic weathered soils in Gyeongju, South Korea. Samples were collected according to their grade of weathering and subjected to modal analysis, XRD analysis, XRF analysis, physical property tests, particle size distribution tests, and slake durability tests. Modal and XRD analysis identified these rocks as biotite granite; secondary alteration minerals were not observed. Physical property tests and particle size distribution analyses indicate an average porosity of 41.28% and a sand content of > 90 wt.%. These values are somewhat higher than those of granites in general. The results of the slake durability test and XRF analyses show that the physical and chemical weathering indices of the samples vary with the degree of weathering.

해안 암체와 내륙 암체부의 풍화 와지 사이의 암석 강도 차이에 대한 연구

김종연 ( Jong Yeon Kim ) 한국지형학회 2015 한국지형학회지 Vol.22 No.4

The chemical composition of samples from abandoned cliff and coastal rocks at Munam, Gosung, Gangwon province are analysed. Weathering pits are found at the top and surface of abandoned cliff and these forms are inactive in terms of active physical and chemical weathering. So these forms can be regarded as relict forms rather than active. The tafoni and weathering pits are found from the coastal rocks which are actively being weathered and eroded by sea water and splash. The rebound values are measured at 5 points at and around the abandoned cliff with Schmidt hammer. The results show that the coastal rock has higher rebound values than abandoned cliff. It can be assumed that coastal rock is composed with more resistant rock than abandoned rock cliff. Weathering intensity of each samples can be compared with various weathering indices which can be calculated using chemical composition. In this study, the CIA, most frequently used index in geomorphological literatures, showed only weak difference between the samples. The CIA value of the coastal rock is lower than those of abandoned cliff. However, the difference between two groups is very small. PIA shows similar pattern while the WIP and CPA show similar patterns with larger differences. In the case of WIP, the value of coastal rock is highest and cliff and rock meal are follows. It means the coastal rock is most fresh in terms of chemical weathering while the rock meal is severely weathered. This pattern shows good match with rock rebound values. It is assumed that this pattern is not result of current weathering and weathered material removal processes which is most active near of the sea. It can be concluded that the abandoned cliff had experienced similar weathering environment to coastal rock. After it was abandoned, weathered part of the cliff experienced relatively slow erosion processes and preserve the weathered materials, while weathered part of coastal rock is eroded continuously by sea water and relatively fresh parts are exposed to surface. This results are support the result from previous study from the coast of Yellow sea.

Interaction between physical and chemical weathering of argillaceous rocks and the effects on the occurrence of acid mine drainage (AMD)

Shinji Matsumoto,Hideki Shimada,Takashi Sasaoka 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.3

The disintegration of rocks by weathering plays an important role in the occurrence of Acid Mine Drainage (AMD), which is the environmental problem caused by the exposure of sulfide minerals to water and oxygen. The weathering of rocks is, generally, classified into physical or chemical weathering. However, there are few studies that focus on the complex interaction between physical and chemical weathering of rocks and on the effects of the interaction on the occurrence of AMD. This paper elucidates the complex interrelation between physical and chemical weathering of rocks as well as the progress of AMD through leaching test and weathering test with argillaceous rocks taken in open-cast coal mine in Indonesia in addition to sample analysis before and after the wetting and drying cycle: the rock samples were exposed to oxygen and water during the cycle. The results indicated that the argillaceous rocks which consist of sulfide and/or sulfate caused chemical weathering with micro-cracks on the surface of rocks through the dissolution of soluble iron and sulfur during the occurrence of AMD. Additionally, physical weathering of rocks due to clay minerals was accelerated by chemical weathering with the development of cracks with the occurrence of AMD in the argillaceous rocks containing kaolinite and pyrite. Although weathering of rocks also accelerated AMD, it was concluded that the sulfur content, the form of sulfur and iron in rocks, and the supply of oxygen significantly contributed to the occurrence of AMD.