• Title/Summary/Keyword: 변형 화강암

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Geometry and Kinematics of the Yeongdeok Fault in the Cretaceous Gyeongsang Basin, SE Korea (한반도 동남부 백악기 경상분지 내 영덕단층의 기하와 운동학적 특성)

  • Seo, Kyunghan;Ha, Sangmin;Lee, Seongjun;Kang, Hee-Cheol;Son, Moon
    • The Journal of the Petrological Society of Korea
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    • v.28 no.3
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    • pp.171-193
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    • 2019
  • This study aims to identify the geometry and internal structures of the Yeongdeok Fault, a branch fault of the Yangsan Fault, by detailed mapping and to characterize its kinematics by analyzing the attitudes of sedimentary rocks adjacent to the fault, slip data on the fault surfaces, and anisotropy of magnetic susceptibility (AMS) of the fault gouges. The Yeongdeok Fault, which shows a total extension of 40 km on the digital elevation map, cuts the Triassic Yeongdeok Granite and the Cretaceous sedimentary and volcanic rocks with about 8.1 km of dextral strike-slip offset. The NNW- or N-S-striking Yeongdeok Fault runs as a single fault north of Hwacheon-ri, Yeongdeok-eup, but south of Hwacheon-ri it branches into two faults. The western one of these two faults shows a zigzag-shaped extension consisting of a series of NNE- to NE- and NNW-striking segments, while the eastern one is extended south-southeastward and then merged with the Yangsan Fault in Gangu-myeon, Yeongdeok-gun. The Yeongdeok Fault dips eastward with an angle of > $65^{\circ}$ at most outcrops and shows its fault cores and damage zones of 2~15 m and of up to 180 m wide, respectively. The fault cores derived from several different wall rocks, such as granites and sedimentary and volcanic rocks, show different deformation patterns. The fault cores derived from granites consist mainly of fault breccias with gouge zones less than 10 cm thick, in which shear deformation is concentrated. While the fault cores derived from sedimentary rocks consist of gouges and breccia zones, which anastomose and link up each other with greater widths than those derived from granites. The attitudes of sedimentary rocks adjacent to the fault become tilted at a high angle similar to that of the fault. The fault slip data and AMS of the fault gouges indicate two main events of the Yeongdeok Fault, (1) sinistral strike-slip under NW-SE compression and then (2) dextral strike-slip under NE-SW compression, and shows the overwhelming deformation feature recorded by the later dextral strike-slip. Comparing the deformation history and features of the Yeongdeok Fault in the study area with those of the Yangsan Fault of previous studies, it is interpreted that the two faults experienced the same sinistral and dextral strike-slip movements under the late Cretaceous NW-SE compression and the Paleogene NE-SW compression, respectively, despite the slight difference in strike of the two faults.

The Optimal Method to Determine Damage Threshold of Rock using Hwangdeung Granite (황등화강암을 이용한 암석의 손상기준 결정방법 연구)

  • Jang, Bo-An;Ji, Hoon;Jang, Hyun-Shic
    • The Journal of Engineering Geology
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    • v.20 no.1
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    • pp.89-100
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    • 2010
  • Although various methods for determination of damage threshold in rock have been suggested, clear damage thresholds were determined by some methods, but different thresholds were measured by other methods. We determined the damage thresholds in Hangdeung granite using all the methods suggested, and investigated the best methods, applicability and errors of each method. The crack initiation threshold and the crack damage threshold which are important in investigation of characteristics of crack development and failure were verified by field strength ratio method and long-term constant load test. The crack closure stress and the crack initiation stress were 57.5 MPa and 77.6 MPa, and the most exact values were yielded by crack volumetric strain. The secondary crack initiation stress was 90.6 MPa and AE event count and AE event count rate were the effective methods. The volumetric stiffness, AE event count and AE event count rate were the most effective methods for determination of crack coalescence threshold and crack coalescence stress was 110.3 MPa. The crack damage stress was 127.5 MPa and was measured correctly by volumetric stiffness and AE event count rate. The ratio between crack initiation stress and uniaxial compressive strength was 0.47 which was very similar with the FSR value of 0.46. The ratio between crack damage stress and uniaxial compressive strength was almost the same as the ratio between long-term strength and uniaxial compressive strength, indicating that the crack initiation stress and the crack damage stress measured were correct.

The Wondong magmatic system : its petrochemical evolution (원동 마그마계 : 암석화학적 진화)

  • 황상구
    • The Journal of the Petrological Society of Korea
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    • v.6 no.3
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    • pp.166-184
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    • 1997
  • The Wondong caldea is a deeply eroded structure that offers spectacular exposures through the core and margins of a resurgent caldera. The Wondong Tuff and the postcollapse intrusions range from medium-silica rhyolite to rhyodacite in composition and the postcollapse lava and tuff, preresurgent and resurgent intrusions also range from medium-silica rhyolite to an-desite, which jump to gap dacite composition. The continuous compositional zonations generally define a large stratified magma system in the postcollapse and resurgent magma chamber. Isotopic and trace element evidence suggest that the compositional zonations might have resulted from the differentiations from crystal fractionations of a parental andesitic magma, accompanying a little contamination from the crustal assimilations near the chamber roof and wall. But chemically and isotopically distinct late intusions might have resulted from emplacement of any different magma batch.

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Time-relationship between deformation and metamorphism of the Paleozoic metasedimentary rocks of the north Sobaegsan massif in the Janggunbong area, Korea (장군봉지역 북부 소백산육괴의 고생대 변성퇴적암류에 대한 변형작용과 변성작용 사이의 상대적인 시간관계)

  • 강지훈;오세봉;김형식
    • The Journal of the Petrological Society of Korea
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    • v.7 no.3
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    • pp.190-206
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    • 1998
  • The microstructures and time-relationship between deformation and growth of metamorphic minerals(metamorphism) of the Paleozoic metasedimentary rocks(Joseon Supergroup and Pyeongan Group) in the Janggunbong area at the central-south part in the North Sobaegsan Massif, Korea, have been analyzed in this paper. The first phase metamorphism (low-pressure type metamorphism), recognized as the crystallization of stack-type chloritoid and biotite and augen-type old andalusite, occurred under non-deformational condition before D1 deformation related to the formation of an E-W trending isocline-synclinal fold(Janggunbong fold) and associated its axial plane S1 foliation, and produced regional mineralogical zoning of E-W trend in the Paleozoic rocks. The second phase metamorphism(medium-pressure type metamorphism), related to the growth of staurolite and garnet porphyroblasts with straight or curved internal foliations(Si), occurred under non-deformational condition after D1 deformation related to the formation of E-W trending thrusts modifying the Janggunbong fold and during D2 deformation related to the formation of E-W trending Yecheon shear zone. This metamorphism also produced regional mineralogical zoning of E-W trend. After D2 deformation occurred the intrusion of Jurassic Chunyang granite and associated its contact metamorphism which crystallized patchy-type young andalusite and prismatic- or fibrous-type sillimanite and coarse-grained garnet. This metamorphism occurred under non-deformational condition before D3 deformation related to the formation of S3 crenulation cleavage and during early phase of D3 deformation, and formed narrow mineralogical zoning of N-S trend near Chunyang granite.

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Analysis of Co-relationship between Rock Mass Grade by RMR and Estimation Method of Rock Deformation Modulus by Suggested Formulas (RMR 분류에 의한 암반등급과 제안식에 의한 암반 변형계수 추정기법의 상관관계 분석)

  • Do, Jongnam;Lee, Jinkyu;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.4
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    • pp.13-26
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    • 2012
  • The deformation modulus of rock masses is a very important design factor for the computation of stability of tunnels and their support systems. Several empirical formulas to estimate the deformation modulus using simple rock classification methods such as RQD or RMR are widely used because field tests to evaluate the deformation modulus are very expensive and time consuming work. However, these formulas can be depended on experiences from the characteristics of local sites in each country. So it is possible that there might be limitations to estimate appropriate deformation modulus in South Korea using the empirical formulas. Therefore, in this study, the applicability of empirical formulas was analyzed by comparing estimated value with the measured value from eight sites in South Korea. The results show that the estimated value based on the empirical formulas partially have tendency to overestimate. Especially, in case of sedimentary rocks, it was too difficult to apply to the empirical formulas because there was no relation ship between estimated value and measured value. For these reasons, additional data from many tests and accurate analyses are necessary to evaluate the estimation method for the deformation modulus considering the local characteristics of rock masses.

Evaluation of Permanent Deformation Characteristics of Recycled Asphalt Concretes Made by Improved Binder-Rejuvenation (바인더 회생방식을 개선한 재생 아스팔트 콘크리트의 소성변형 특성 연구)

  • Kim Kwang-Woo;Kweon Oh-Sun;Doh Young-Soo
    • International Journal of Highway Engineering
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    • v.8 no.1 s.27
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    • pp.1-13
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    • 2006
  • This paper is one of the studies for developing new methodologies for improving performance of hot-mix recycled asphalt mixtures. The objective of this study is to evaluate rut-resistance characteristics of recycled asphalt mixture which was prepared by newly developed mixing method. The new mixing method provided more sufficient rejuvenation of old binder of reclaimed asphalt pavement (RAP), making homogeneous binder viscosity level in a recycled mixture. Two aggregates (gneiss and granite), two RAP contents (15% and 30%) and two contents (none and 6%) of polymer modifier (LDPE) were used. Recycled mixture was prepared with two methods; method A and method F. To examine difference of binder oxidation level by type of material within a recycled mixture, Gel-permeation chromatography(GPC) analysis was performed on the binders mixed with coarse aggregates and matrix separately. Laboratory tests were performed for evaluation of rut resistance characteristics of each recycled mixture and these includes wheel tracking (WT) test and Kim test. Rut depth and dynamic stability were obtained from WT test and deformation strength $(S_D)$ was obtained from Kim test. The results of regression analysis was shown that correlation $(R^2)$ of F mixing mixtures was higher than one of A mixing mixtures. Therefore, F mixing mixtures showed more consistent rut resistance than h mixing mixtures.

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A study on critical strain based damage-controlled test for the evaluation of rock tunnel stability (암반터널 안정성 평가를 위한 손상제어실험 기반의 한계변형률에 관한 연구)

  • Lee, Kang-Hyun;Kim, Do-Hoon;Park, Jeong-Jun;Lee, In-Mo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.13 no.6
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    • pp.501-517
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    • 2011
  • In general, the tunnel stability during excavation is assessed by comparing measured displacements at roof and sidewall to control criteria. The control criteria were established based on the past experience that considered ground conditions, size of the tunnel cross section, construction method, supports, etc. Therefore, a number of researches on the control criteria using the critical strain have been conducted. However, the critical strain obtained from uniaxial compression tests have drawbacks of not taking damage in rock mass due to increase of stress level and longitudinal arching into account. In this paper, damage-controlled tests simulating stress level and longitudinal arching during tunnel excavation were carried out in addition to uniaxial compression tests to investigate the critical strain characteristics of granite and gneiss that are most abundant rock types in Korean peninsula. Then, the critical strains obtained from damage-controlled tests were compared to those from uniaxial compression tests; the former showed less values than the latter. These results show that the critical strain obtained from uniaxial compression tests has to be reduced a little bit to take stress history during tunnel excavation into account. Moreover, the damage critical strain was proposed to be used for assessment of the brittle failure that usually occurs in deep tunnels.

Deformation Characteristics of Artificially Fracture Joins of Granite under Normal and Shear Loading (수직 및 전단하중하에서 화강암 인공절리의 변형특성)

  • 김영근;이희근
    • Tunnel and Underground Space
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    • v.3 no.2
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    • pp.142-151
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    • 1993
  • In this study, the deformation characteristics of atrtificially fractured joints of granite under normal and shear loading were investigated. To obtain the characteristics of joint deformation, compression and shear tests were performed in the laboratory on three different sizes of rock specimens. The rock used in the experimens was Iksan granite. Joints were produced artificially by fracturing using the apparatus for generating extension-joint. Joint normal deformability was studied by conducting cyclic loading tests on the joints. Joint closure varied non-linearly with normal stress through cyclic loadings. As normal stress increased, the joints gradually reached a state of maximum joint closure. The relation between normal stress and joint closure for mated and unmated joints was well described by the hyperbolic and exponential function, respectively. Joint shear deformability was studied by performing direct shear tests under normal stresses on the joints. it was shown that the behaviour in the prepeak range was non-linear and joint shear stiffness depended on the size of specimen and the normal stress.

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A Study on the Mechanicla Behavior of Two Granites at Elevated Temperatures (고온하 화강암의 변형 및 파괴거동에 관한 연구)

  • 장명환;양형식
    • Tunnel and Underground Space
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    • v.7 no.2
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    • pp.130-135
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    • 1997
  • When crystalline rocks are heated, thermal stress is induced by the differences in thermal expansion of the mineral composition and its orientation. In this study, high temperature uniaxial compressive tests were carried out for Iksan and Hwangdeung granites to study the deformation and failure behavior due to thermal loading. Compressive and tensile strength of Hwangdeung granite for 20$0^{\circ}C$ decreased to 80% and 82% of the room temperature strength, and those of Iksan granite decreased to 90% and 92% for 20$0^{\circ}C$, respectively. Elastic moduli of both granites were decreased sharply at the stress level of 80% of ultimate failure strength. Elastic moduli of both granites by variation of temperature at 50% of ultimate failure strength was decreased as almost linearly.

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Geological Structures of the Southern Jecheon, Korea: Uplift Process of Dangdusan Metamorphic Complex and Its Implication (옥천대 제천 남부의 지질구조: 당두산변성암복합체의 상승과정과 그 의미)

  • Kihm, You-Hong;Kim, Jeong-Hwan;Cheong, Sang-Won
    • Journal of the Korean earth science society
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    • v.21 no.3
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    • pp.302-314
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    • 2000
  • Keumseong area in the southern part of the Jecheon city, the Ogcheon Belt, consists of Precambrian Dangdusan Metamorphic Complex, Dori Formation of the Choseon Supergroup, and Jurassic Jecheon Granite. The Dangdusan Metamorphic Complex consists of quartz schist, mica schist. quartzite and pegmatite. The Dori Formation is composed of mainly laminated limestone. The rocks in the study area have been undergone at least three phases of deformations since Paleozoic period. The Dangdusan Metamorphic Complex is outcrop at three areas in the study area, which are exposed along the faults and occurred as inlier within the Dori Formation. Previous authors interpreted the uplift of the Dangdusan Metamorphic Complex by the Dangdusan Fault, but we could not find any evidences related to the Dangdusan Fault. Thus, we interpret the uplift of the Dangdusan Metamorphic Complex due to the D$_2$ Weolgulri and Dangdusan thrusts and post-D$_2$ Jungbodeul, Kokyo and Jungjeonri faults. The uplift of the Busan Metamorphic Complex to the west of the study area was interpreted by ductile deformation. However, the Dangdusan Metamorphic Complex is formed by brittle thrusts and faults in this study. According to deformation sequence, the characters of deformations in the Choseon and Ogcheon suprergroups had been changed from ductile to brittle deformations through the time. Therefore, we interpret the Dangdusan Metamorphic Complex is exposed later than the Busan Metamorphic Complex.

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