【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。更多还原

【Abstract】 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.更多还原