含共面双裂隙复合岩石的力学特性与破坏规律研究

Study on the Mechanical Properties and Failure Law of Composite Rocks with Coplanar Double Fissures

为了研究裂隙构型属性对层状复合岩石的力学行为、破坏模式及裂纹扩展规律的影响,以预制含共面双裂隙复合岩样为研究对象,通过室内单轴压缩试验与数字图像采集模块,分析在不同裂隙长度、倾角下岩样的力学特性和破坏特征。结果表明:(1)岩样峰值应力和弹性模量随着裂隙倾角增加上升,随裂隙长度增加而下降;劣化系数k随裂隙倾角的增加而减小,随裂隙长度的增加而增大。(2)破坏模式受裂隙倾角和两种岩石材质的影响,破碎程度主要由裂隙长度决定。(3)岩桥的贯通模式受裂隙倾角和结构面的控制,4种贯通模式中,随裂隙倾角增大,贯通趋势增强,但裂隙倾角达90°时不再贯通,且结构面会抑制岩桥的贯通。(4)裂纹扩展受裂隙长度影响,当裂隙长度小于12mm时,裂纹首先出现在岩样的右半部分,而弹性阶段产生的裂纹主要出现在岩样的左半部分,当裂隙长度大于12mm时,裂纹均匀布满岩样表面。该研究成果对实际工程建造和设计具有一定的指导意义。

In order to investigate the impact of fissure configuration attributes on the mechanical behavior,failure mode,and crack propagation law of layered composite rocks,a study was carried out on pre-fabricated composite rocks with coplanar double fissures.Indoor uniaxial compression tests and a digital image acquisition module were used to analyze the mechanical properties and failure characteristics of rock samples with various fissure lengths and angles.The following conclusions are drawn.Firstly,the peak stress and elastic modulus of rock samples increase with the increase of fissure angle,while decrease with the increase of fissure length.The degradation coefficient k displays a decrement with increasing fissure angle and an increment with increasing fissure length.Secondly,the failure pattern is influenced by both the fissure angle and the two types of rock materials,with the degree of fragmentation primarily governed by fissure length.Thirdly,the bridging mode of rocks is subject to fissure angle and structural planes.In the four bridging modes,the transfixion trend increases with the increase of fissure angle,but it is no longer transfixion when the fissure angle reaches 90°,and the structural plane will inhibit the transfixion of rock bridge.Fourthly,crack propagation is contingent on fissure length.When the fissure length is below 12 mm,cracks predominantly emerges in the right half of the rock sample,while post-elastic stage cracks are principally observable in the left half.When the fissure length is greater than 12mm,the crack is evenly distributed on the surface of the rock sample.The research results have a certain guiding significance for the construction and design of practical engineering.