受单轴压缩大理岩填充割缝周围的微裂纹生长
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摘要
在扫描电镜实时观测下,进行了受单轴压缩大理岩填充割缝周围的微裂纹生长的实验观测研究。实验所用岩石材料为房山大理岩,试件为平板状,中心予制穿透试件的割缝,用水泥砂浆充填,割缝的长轴与外加单轴压缩方向分别成30°,45°和60°夹角。对试件中填充割缝周围的微裂纹的萌生、扩展连通和闭合等过程进行了显微照相及分析,结果表明,微裂纹首先呈剪切破裂带状发育,随外载的增加而连通形成断裂带。将实验结果与以往未填充割缝实验结果对比发现:割缝填充后微裂纹萌生所需的载荷水平明显提高;同时,微裂纹的起裂点向割缝端部移动,微裂纹的多重发育也更加明显。
The mini-crack development around a prefabricated fracture cemented with grout in a plate specimen subjected to uniaxial compression is tested and studied under direct SEM observation. The rock used for the test is Fangshan marble,which is relatively homogeneous in texture. Its grain size is 0.05～0.35 mm,its elastic modulus is about 78.9 GPa,Poissons ratio is 0.35 and uniaxial compressive strength is 160 MPa. The specimen is a plate 25 mm×12 mm ×1.6 mm in size with a central slot about 0.6 mm wide and 6.0 mm long cemented with grout. The compressive strength of the cement grout is about one fifth of that of the marble. The major axis of the cemented fracture is inclined to the loading direction at 30°,45° and 60°. The tests are carried out in the vacuum chamber of a SEM using a vise-type loading frame. Its loading capacity is 2 000 N and the load on the specimen is measured by the piezoelectric transducer with a resolution of 0.5 N. The initiation,coalescence and recovery of mini-cracks are photographed and analyzed. The mini-cracks extend during the formation of a shear band composed of paralleled cracks,and then merge to form the fracture. The test results are compared with those with open fracture in the specimen from the previous study. It is observed that not only the load required for the crack initiation is higher,but also the crack initiation points move closer to the fracture ends in cemented fracture specimen. There are more multiply developed mini-cracks at the neighborhood of the fracture. The real fracture or fault system in earth,no matter at what scale,has lower strength,if it is filled with fault gouge or fault clay. Therefore,the test results in this paper gives a comprehensive picture for understanding and simulating the fracturing process in earth crust.
The mini-crack development around a prefabricated fracture cemented with grout in a plate specimen subjected to uniaxial compression is tested and studied under direct SEM observation. The rock used for the test is Fangshan marble,which is relatively homogeneous in texture. Its grain size is 0.05～0.35 mm,its elastic modulus is about 78.9 GPa,Poissons ratio is 0.35 and uniaxial compressive strength is 160 MPa. The specimen is a plate 25 mm×12 mm ×1.6 mm in size with a central slot about 0.6 mm wide and 6.0 mm long cemented with grout. The compressive strength of the cement grout is about one fifth of that of the marble. The major axis of the cemented fracture is inclined to the loading direction at 30°,45° and 60°. The tests are carried out in the vacuum chamber of a SEM using a vise-type loading frame. Its loading capacity is 2 000 N and the load on the specimen is measured by the piezoelectric transducer with a resolution of 0.5 N. The initiation,coalescence and recovery of mini-cracks are photographed and analyzed. The mini-cracks extend during the formation of a shear band composed of paralleled cracks,and then merge to form the fracture. The test results are compared with those with open fracture in the specimen from the previous study. It is observed that not only the load required for the crack initiation is higher,but also the crack initiation points move closer to the fracture ends in cemented fracture specimen. There are more multiply developed mini-cracks at the neighborhood of the fracture. The real fracture or fault system in earth,no matter at what scale,has lower strength,if it is filled with fault gouge or fault clay. Therefore,the test results in this paper gives a comprehensive picture for understanding and simulating the fracturing process in earth crust.
引文
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11赵永红,黄杰藩,王仁.岩石微破裂发育的扫描电镜即时研究[J].岩石力学与工程学报,1992,11(3):284～294
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14Zhao Y, HuangJ,Wa ngR.Dev el opmento fsubcrack sb etwe enenechelonfracturesinrockplates[J].Pageoph,1995,145(3/4):759～773
15赵永红,黄杰藩,候建军等.岩石细观破裂的实验观测研究及其对了解地震活动性的启示[J].地球物理学报,1995,38(5):627～635
16李炼,徐钺,李启光等.花岗岩板渐进破坏过程的微观研究[J].岩石力学与工程学报,2002,21(7):940～947
2HoriiH,Nemat-NasserS.Compression-induc edmicrocra ckgrow th inbritt lesolids:axi alsplitti nga ndshe arfailure[J].J.Geophys.Res.,1985,90(B4):3105～3125
3林鹏.含裂纹与孔洞缺陷介质的脆性破坏行为[J].岩石力学与工程学报,2002,21(8):1283～1283
4LinP,LoganJ.Inter ac tio noftwoc losely spacedcr acks :arockmodelstudy[J].J.Geophys.Res.,1991,96(B13):21667～21675
5黄明利.岩石多裂纹相互作用破坏机制的研究[J].岩石力学与工程学报,2001,20(3):423～423
6黄凯珠,林鹏,唐春安等.双轴加载下断续预制裂纹贯通机制的研究[J].岩石力学与工程学报,2002,21(6):808??816
7W ongRHC, ChauKT.Crac kc o alescenceinarock- likeMateri alc ontainingtwocracks[J].Int.J.RockMech.Min.Sci.Geomech.Abstr.,1998,35(2):147～164
8WangR,Z haoYS,ChenY,e tal .Exper imentan dfiniteele mentsimu latio nofX-type shea r fract ur esfromacrackinmarble[J].Tectonophysics,1987,144(1～3):1 41～150
9Huan gJF, ChenG L,ZhaoYG,eta l.Ane xp eri mental studyo fthestrainf ields de velopme nt p riorto failu reofa marbleplateundercompression[J].Tectonophysics,1990,147(1～3):269～284
10夏蒙棼,柯孚久,吕永华等.理想裂纹系统中的随机扩展效应[J].中国科学(D辑),1991,21(3):276～284
11赵永红,黄杰藩,王仁.岩石微破裂发育的扫描电镜即时研究[J].岩石力学与工程学报,1992,11(3):284～294
12赵永红,黄杰藩,王仁.破裂带发育的SEM实验研究及其对地震前兆的启示[J].地球物理学报,1993,36(4):453～462
13ZhaoYonghong,HuangJie fan,WangRen. Re al-timeSEMobservat ionsoft he Micr ofract u ringprocess inrockduringacompressiontest[J].Int.J.RockMech.Min.Sci.Geomech.Abstr.,1993,30(6):643～652
14Zhao Y, HuangJ,Wa ngR.Dev el opmento fsubcrack sb etwe enenechelonfracturesinrockplates[J].Pageoph,1995,145(3/4):759～773
15赵永红,黄杰藩,候建军等.岩石细观破裂的实验观测研究及其对了解地震活动性的启示[J].地球物理学报,1995,38(5):627～635
16李炼,徐钺,李启光等.花岗岩板渐进破坏过程的微观研究[J].岩石力学与工程学报,2002,21(7):940～947
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