层状复合岩体损伤演化规律及分形特征

The evolution law of the damage of bedded composite rock and its fractal characteristics

采用现场所取页岩和灰岩经室内加工"拼接"成6种不同组合方式的层状复合岩体,研究其在单轴压缩下的损伤破裂过程和声发射特征。试验过程中采用声发射系统采集试件在试验过程中所释放的声发射信号,试验前后对复合岩体进行CT扫描,分析试件破裂前后内部裂纹发育情况,并引用分形理论对破裂试件不同部位CT图像进行损伤程度分析。研究结果表明:(1)层状复合岩体的破坏是页岩组分材料和灰岩组分材料在荷载作用下耦合破坏的过程。破坏过程中灰岩组分材料对页岩组分材料的横向变形有制约作用,页岩组分材料对灰岩组分材料的横向变形则有反向促进作用,破坏时页岩组分材料的强度大于单一页岩,灰岩组分材料的强度则小于单一灰岩。(2)根据组合方式不同,将层状复合岩体破坏模式分为张拉劈裂型破坏、剪切滑移型破坏和劈裂剪切复合型破坏3种。岩石的组合方式决定着其受力状态,从而影响着复合岩体的破坏模式。(3)复合岩体平均CT数和试件扫描破裂断面盒维数均能够反映出复合岩体的损伤程度,即试件破坏前后断面CT数差值越大,断面盒维数越大,则其损伤程度也越大。

Shale and limestone in situ are processed indoors into 6 different combinations of bedded composite rock,through which the author explores the damage and fracture process under uniaxial compression as well as its acoustic emission characteristics. Acoustic emission system is adopted to collect the acoustic emission signal released by the test specimen during the experiment. CT scanning is performed on the composite rock before and after the experiment. The development of the internal cracks before and after the fracture is analyzed,and the fractal theory is adopted to analyze the damage of fracturing specimen through its CT images of different parts. The results show that：（1） The damage of bedded composite rock is a coupling failure process of shale component material and limestone component material under load. In the process of damaging,limestone has a restriction on shale transverse deformation,while shale has a promoting effect on limestone. The strength of shale component material is greater than that of single shale,which also goes for limestone component material.（2） According to the different combinations,the failure mode of bedded composite rock can be divided into 3 kinds：tension splitting failure,shear slip-type failure and splitting shear compound damage. Combinations of rock play a decisive role in its stress and affect the failure mode.（3） The average number of CT-scanning composite rock and the box dimension of its fracture section is able to respectively reflect the damage of the rock,that is to say,the greater the CT number difference before and after the damage of the section is,the greater the box dimension of the section is,and the more serious the damage is.