单侧限压缩下预制裂隙试样力学特性及板裂化机制细观研究

Meso research on mechanical properties and slab failure mechanism of pre-fractured rock mass under the condition of one side restriction loading

岩体板裂化破坏是地下工程中一种常见的破坏现象。采用等效岩体技术,将岩体中裂隙(平行于临空面)和岩块分别用光滑节理模型及颗粒体模型表征,通过试验和计算对比,研究单侧限压缩条件下裂隙岩体强度、裂纹分布、裂纹孕育演化规律及裂隙岩体板裂化形成机制。研究表明:(1)随裂隙数量的增加,岩体单侧限抗压强度近似呈线性降低的规律。(2)单侧限压缩下裂隙岩体中产生的裂纹可划分为Ⅰ型~Ⅴ型裂纹,其中Ⅰ型、Ⅱ型(剪切)裂纹是由加载端部效应导致,Ⅲ型~Ⅴ型裂纹由岩体板裂化破坏导致。(3)单侧限压缩下岩体板裂化破坏过程中,导致无侧限边界处岩体剥落的Ⅴ型裂纹最先产生,原生裂隙进一步扩展的Ⅳ型裂纹随后产生,最后产生的是板裂化现象向岩体深部发展的Ⅲ型裂纹。(4)各类裂隙试样在单侧限压缩下的声发射数量与破裂强度均近似服从高斯函数分布关系。

The slab failure of rock mass is one of the common destruction phenomena in underground engineering. Based upon equivalent rock mass(ERM) technique, the fracture(parallel to the free surface) and rock block are represented by the smooth-joint model and bonded-particle model, respectively. The strength, crack distribution, crack initiation and evolution, and slab failure formation mechanism of fractured rock mass under one side restriction(OSR) compression are studied by comparing experimental results and numerical modelling. With the increase in the number of fracture, the OSR compressive strength of rock mass exhibits linear decreasing. Under OSR loading, five types of cracks generated in rock mass can be identified. The type-Ⅰ and type-Ⅱ(shear) cracks are caused by the loading end effect, while the type-Ⅲ, type-Ⅳ and type-Ⅴ cracks are caused by slab failure of rock mass. In the process of slab failure, type-Ⅴ cracks which causes rock mass spalling at the unconfined boundary first occurs. Then type-Ⅳcracks result in the propagation of original fractures generate. Finally, the type-Ⅲ cracks generate, which indicates that the slab failure phenomenon is developing towards the interior of rock mass. In various specimens under OSR loading, the relationship between the acoustic emission(AE) quantities and crack magnitude approximates Gaussian function distribution.