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Summary This paper presents a systematic procedure for determining fracture toughness of an anisotropic marble using the diametral
compression test (Brazilian test) with a central crack on the discs. Additionally, a novel formulation to increase the accuracy
in Stress Intensity Factor (SIF) calculations using Boundary Element Method (BEM) is applied to determine the stress intensity
factors and the fracture toughness of anisotropic rocks under mixed-mode loading. The numerical results show that the SIFs
for both isotropic and anisotropic problems are in good agreement with those reported by previous authors. The marble with
clear white-black foliation from Hualien (in eastern Taiwan), was selected for the Brazilian tests. Diametral loading was
conducted on the Cracked Straight Through Brazilian Disc (CSTBD) specimens to evaluate their fracture toughness. In addition,
a new fracture criterion was developed to predict pure mode I, pure mode II or mixed mode (I–II) fracture toughness of the
anisotropic marble. The new fracture criterion is based on the examination of mode I, mode II and mixed mode (I–II) fracture
toughness for different crack angles and anisotropic orientation.
Authors’ address: Associate Professor Chao-Shi Chen, Department of Resources Engineering, National Cheng Kung University,
No. 1 Dasyue Rd., East District, Tainan 701, Taiwan 相似文献
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Experimental Calibration of ISRM Suggested Fracture Toughness Measurement Techniques in Selected Brittle Rocks 总被引:1,自引:4,他引:1
Summary A wide variety of specimen types and methods are employed in fracture toughness measurement of rocks, which result in scattered
values for the same rock type. In order to provide some consistency to the values, the International Society for Rock Mechanics
(ISRM) recommended three suggested methods using core based specimens, the Chevron Bend (CB) test, the Short Rod (SR) test
and the Cracked Chevron Notch Brazilian Disc (CCNBD) test. This standardization helped obtain more consistent values but still
a variation of 20–30% was observed in the values of fracture toughness obtained with the CB and SR methods. The values obtained
with the CCNBD method were found to be consistently lower (30–50%) than those of the other two methods (CB and SR). Many reasons
have been offered to explain this deviation. These include size of the specimen, anisotropy of rock, a dimensionless parameter
in the fracture toughness calculation equation for the CCNBD test, etc. A comprehensive test program was initiated to identify
the cause of these discrepancies between the CB and CCNBD methods. Three brittle rock types were selected for the study and
more than 200 tests were conducted to measure the values of fracture toughness.
A rigorous statistical analysis was carried out to determine the confidence level and find the significance of the test results.
It was found that the CB and CCNBD methods were very comparable provided the correct equation for fracture toughness calculation
was used for the CCNBD method and the size of the specimens was selected carefully. The error in the ISRM 1995 formula of
fracture toughness for the CCNBD method could be the major factor responsible for the consistently lower values obtained with
the method. 相似文献
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花岗岩与地壳厚度关系探讨 总被引:3,自引:1,他引:3
文中首先从板块构造与大陆构造的对比出发,指出板块构造主要研究洋壳,洋壳主要研究玄武岩,玄武岩主要研究构造环境.大陆构造主要研究陆壳,陆壳玄武岩少花岗岩多,因此,花岗岩在大陆构造研究中具有特殊的地位.由于花岗岩比玄武岩复杂得多,其中尤以源岩和深度对花岗岩的影响最大,是大陆花岗岩研究最重要的课题.文中接着讨论了Sr和Yb的... 相似文献
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利用阴极发光仪对一些前寒武纪变质岩(河北,内蒙等地)和西藏及其它地区的后寒武变质岩,以及不同时代和成因的花岗岩类岩石的样品进行了观察。阴极发光与某些过渡元素的含量有关,可以揭示岩石的构造,间接地反映矿物化学成分的特点。本文介绍了阴极发光在变质岩和花岗岩类岩石的以下几个方面的应用:1) 间接地确定变质级;2) 揭示原岩的变余构造,3) 鉴别细粒和发光矿物;4) 研究矿物之间的反应;5) 重建变形构造。 相似文献
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花岗质次火山岩的成因类型及成矿专属性 总被引:2,自引:0,他引:2
与花岗质火山岩具不同的成因类型相似,自然界也存在着不同成因类型的次火山岩。后者与三大成因类型花岗岩相对应,亦可分为壳型次火山岩,过渡型次火山岩和幔型次火山岩三类。亮型次火山岩主要与U、REE,W、Sn、Nb、Ta等矿产有关系,属花岗岩矿床系列。过渡型次火山岩主要与Cu、Pb、Zn、Ag、Au有关,并伴有W、Sn成矿、属斑岩矿床系列。幔型次火山岩主要与黄铁矿型Cu、Pb、Zn多金属矿化有关,属海相火山岩矿床系列。 相似文献
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花岗岩中常用压力计的应用评述 总被引:2,自引:0,他引:2
本文简要讨论了花岗岩中常用压力计的应用限制条件和误差。对于钙碱性花岗岩推荐使用角闪石全铝压力计;对低
压矿化岩体建议使用黑云母全铝压力计即可;奥长环斑花岗岩中可应用富铁斜方辉石-铁橄榄石-石英组合压力计;存在两
种长石和石英平衡共结的花岗岩可利用Q-Ab-Or-H2O相图获得它们的共结压力。花岗岩矿物中流体包裹体的内压可以通过
热力学状态方程或者拉曼光谱获得;特殊的岩浆矿物如绿帘石有时候也可以指示岩浆结晶时所处的最低压力。此外,通过
THERMOCALC计算的视剖面是约束共生矿物组合及熔体形成温压条件的最后方法。 相似文献
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华南花岗岩研究的回顾与展望 总被引:52,自引:7,他引:45
半个世纪以来,华南花岗岩研究经历了3个发展阶段:第一阶段,重点研究了花岗岩的时空分布。根据地质证据与同位素年龄数据,证实华南存在多旋回的花岗岩,即晚元古代花岗岩、加里东期花岗岩、海西一印支期花岗岩和燕山期花岗岩。基本规律是:不同的造山旋回伴有相应的花岗岩。大体上,自西北往东南(向洋方向)花岗岩时代呈愈来愈新的趋势;第二阶段,重点研究了花岗岩的成岩物质来源,划分为M型、Ⅰ型、S型和A型,研究不同成因类型花岗岩形成的构造环境及其岩石地球化学标志;第三阶段,着重研究壳幔作用与花岗岩成因,例如研究玄武岩浆底侵作用与花岗岩的成因联系,以及岩浆混合作用与花岗岩成分多样性的原因。此阶段研究方兴未艾,仍在深入开展之中。今后主要研究方向,环绕3个问题进行:(一)壳幔作用与A型花岗岩成因;(二)陆内花岗岩浆产生的方式和原因(变质核杂岩、花岗岩穹窿、复式花岗岩体);(三)华南大花岗岩省成因。 相似文献
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为揭示整个北山地区构造演化特征,对北山营毛沱地区分布的花岗岩、花岗闪长岩、二长花岗岩、闪长岩等花岗岩类岩石进行了岩石化学研究。结果表现,这些花岗岩类具有偏铝质-过铝质、碱性-钙碱性特征,具有中等的Si O2(62.1%~72.92%)含量,较高的Na2O+K2O(5.4%~9.12%)含量;球粒陨石标准化分配模式图上,具有相对平缓的富集轻稀土元素配分模式,重稀土元素分馏不明显,弱Eu负异常;亏损Nb、Ba、P、Ti,富集Rb、Pb、K;主微量元素对比及图解分析认为花岗岩类具有Ⅰ型或Ⅰ-A型过渡花岗岩的特点。对其中的花岗闪长岩进行了LA-LCP-MS锆石U-Pb定年分析,得出其侵位时间为384.7±7.7Ma,为中泥盆世早期。结合区域地质分析,指出营毛沱地区的花岗岩类形成于北山早古生代洋盆碰撞造山后的拉伸环境,标志北山地区在中泥盆世已进入新的构造演化阶段,即板内伸展阶段。 相似文献
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Relationship Between Solidification Depth of Granitic Rocks and Formation of Hydrothermal Ore Deposits 总被引:14,自引:0,他引:14
Chemical analysis of biotite in representative granitic rocks in Japan shows that the total Al (TAl) content changes with the metal type of the accompanying hydrothermal ore deposits and increases in the following order: Pb‐Zn and Mo deposits < Cu‐Fe and Sn deposits < W deposits < non‐mineralized granitic rocks. The TAl content of biotite in granitic rocks may be a useful indicator for distinguishing between mineralized and non‐mineralized granitic rocks. A good positive correlation is seen between the TAl content of biotite and the solidification pressure of the granitic rocks estimated by sphalerite and hornblende geobarometers and the mineral assemblages of the surrounding rocks. These facts suggest that the TAl content of biotite can be used to estimate the solidification pressure (P) of the granitic rocks. The following empirical equation was obtained: where TAl designates the total Al content in biotite on the basis O = 22. According to the obtained biotite geobarometer, it is estimated that Pb‐Zn and Mo deposits were formed at pressures below 1 kb, Cu‐Fe and Sn deposits at 1–2 kb, W deposits at 2–3 kb and non‐mineralized granitic rocks were solidified at pressures above 3 kb. 相似文献
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浙西南早元古代花岗质岩石的年代 总被引:34,自引:1,他引:34
用单颗粒锆石U-Pb稀释法获得的浙西南前寒武纪变质基底中花岗质岩石的年龄为:下际二长花岗岩1975±80Ma,里庄二长花岗岩1870±36Ma,田后花岗闪长岩1832±80Ma,三枝树混合岩1963±44Ma。这些年龄数据证实本区基底岩石在1875±100Ma时期经历了一次广泛强烈的岩浆热事件,表明八都群(麻源群)岩石的形成应早于2.0Ga。三枝树地区“鹤溪群”中混合岩年龄为1863±44Ma,斜长角闪岩全岩矿物Sm-Nd等时线年龄为2071±48Ma,表明景宁三枝树地区变质岩的时代应为早元古代,并非原来所属“鹤溪群”划归的晚古生代,这套变质岩可能是浙闽变质基底的一部分。 相似文献
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In this paper, the effects of specimen size and geometry on the apparent mode I fracture toughness (K c) of an Iranian white marble (Neyriz) are studied. A number of fracture tests were conducted on center-cracked circular disk (CCCD) specimens with different radii to investigate the size effects on K c. The experimental results demonstrate that the apparent fracture toughness increases in bigger specimens. In order to explain the experimental results, the modified maximum tangential stress (MMTS) criterion is used, where higher order terms of the Williams’ series expansion are included in the maximum tangential stress criterion. It is shown that the MMTS criterion provides good estimates for the apparent fracture toughness of Neyriz marble, obtained from fracture tests of edge-cracked triangular specimens. It is, therefore, concluded that the proposed criterion is able to account for the size and geometry effects on the fracture resistance of rocks simultaneously. 相似文献
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岩石破裂行为的实验研究 总被引:6,自引:0,他引:6
岩样的破裂行为、破坏过程和参数测试是裂隙断裂构造研究的基础和依据。实验岩石样品采自四川东部和新疆北部地区,为测试准确起见,对岩样进行了应力等值线的有限元法计算。通过单轴和三轴实验的岩样破坏观察和应力应变曲线对比,将岩石的破裂行为、应力应变划分为四个阶段,即裂隙压密阶段、弹性变形阶段、微观劈裂阶段和宏观破裂阶段。基于单轴抗压实验岩石劈裂—破裂—碎裂发展过程的微观分析,可以看出宏观破裂主要是沿岩样原有的隐裂隙、临界裂隙发育的,许多新裂隙则主要是在宏观破裂阶段产生的。 相似文献