充填物对含孔洞大理岩力学特性影响规律试验研究

Experimental study of the influence of the filling material on the mechanical properties of marble with holes

  • 摘要: 为研究充填物对含孔洞岩石的力学特性及变形破坏特征的影响规律,室内预制加工了含孔洞及石膏充填物大理岩,分别对其进行单轴压缩和声发射试验,并对破坏前后试件进行CT扫描,分析其裂纹扩展规律.试验结果表明:(1)相比于含孔洞大理岩,石膏充填使试件的抗压强度提高了10.62%.二者峰前特征相似,均表现为孔周裂纹起裂引起第一次应力跌落现象,峰后特征则有所不同,石膏充填使大理岩变形的局部化特征更为明显.(2)峰后阶段,含孔洞试件声发射特征显著,裂纹扩展迅速,石膏充填试件稍慢,表明石膏充填遏制了试件的裂纹扩展.(3)含孔洞和石膏充填大理岩的破坏模型有所区别,含孔洞试件破坏裂纹较为单一,主裂纹以张拉破坏为主,翼裂纹在试件端部较多,部分从侧面贯通,形成块体掉落.充填条件下孔洞周边的裂纹更细更分散,小裂纹相互贯通,形成"X"状剪切破坏.

     

    Abstract: As a natural material, stone can suffer from initial damage (such as bedding and microfracture) during the diagenetic stage and rock defects (such as joints and faults) are formed after diagenesis. Under the influence of these defects, the properties of rock strength, deformation, and failure will also change. Studying the mechanical characteristics of defective rock can truly reflect the actual situation in the field. For the original hole fissures, actual rock engineering often contains fillings that decrease the stress concentration of the surrounding area of the hole; according to the type of filling, the filling can withstand the corresponding pressure. Thus, it is necessary to study the influence of the filling on the mechanical properties of porous rock damage. To study the influence of the filling material on the mechanical properties and the deformation and failure characteristics of the hole-bearing rock (with each specimen containing one hole), hole-bearing marble (with each specimen containing one hole), and plaster filling, the appropriate specimens were prefabricated in an indoor environment. The law of crack propagation of the specimens was analyzed based on the results of the uniaxial compression and acoustic emission tests and the results of CT scanning of the specimens before and after failure. The results are given as follows:(1) In comparison with hole-bearing marble, the peak stress of the marble specimen with the filled hole increases by 10.62%. Before the peak stress of the specimens, the pre-peak features are similar, and both specimens exhibit a stress reduction phenomenon; however, the post-peak characteristics are different, and the characteristics of partial deformation are more obvious. (2) After the peak stress phase, the acoustic emission features of the perforating hole in each hole-bearing specimen are more remarkable, and the crack propagation is more rapid than those of the gypsum-filled specimens, indicating the gypsum filling stems the crack expansion of the specimens. (3) A difference is found between the destruction model of the marble specimen with a hole and that of the marble specimen with the hole filled with gypsum. Each crack is relatively single for the specimen of marble with a hole, and main cracks exhibit tensile damage; moreover, wing cracks are more developed in the end, and some of those cracks propagate toward both sides, resulting in a block falling off. However, cracks around the hole are thinner and more dispersed, forming "X" shear damage because of the mutual crossing of the cracks.

     

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