岩石厚壁圆筒试验破坏的细观力学机制

Meso mechanical mechanisms of thick-walled hollow rock cylinder during failure process

目前采用传统颗粒体模型较难表征岩石内部不规则矿物颗粒的结构特征。以颗粒流理论及PFC程序为平台,采用平面黏结接触模型,构建能反映矿物颗粒结构特征的岩石厚壁圆筒数值模型,从细观力学角度深入探究岩石厚壁圆筒试样在不同内外部围压条件下的破裂机制与规律。研究表明:当内部围压为0时,试样张拉型微破裂占主导优势;层状剥离的破碎颗粒体以轴线为中心形成近似对称的"V"型破坏区域。当内部围压不为0时,随着内部围压不断增大,试样承受的极限外部围压逐渐增大;试样剪切型微破裂逐渐占主导优势,以轴线为中心产生的近似对称的"V"型破坏区域逐渐消退,破坏逐渐从内径岩壁向各个方向扩展。无论内部围压是否为0,试样外部围压、外部体应变等破坏参量演化曲线均可近似划分为3个阶段。

At present, the conventional bonded particle model is difficult to represent the irregular structural feature of mineral grains in rock. A numerical model of thick-walled hollow cylinder of rock to reflect the feature of mineral grain in rock was established using the flat-joint contact model based upon the particle flow theory and PFC code. The failure mechanism and law of thick-walled hollow cylinder of rock with the different inner and external pressures were investigated from the meso mechanical viewpoint. When inner pressure was equal to zero, the microcracks were mainly tensile type in the failure process and the spalling fragmentation particles formed a V-shaped damage area symmetrical to the cylinder axis. When the inner pressure was not equal to zero, the limiting external pressure increased and the shear microcracks gradually dominated in the failure process with the increase of the inner pressures. Meanwhile, the symmetrical V-shaped damage area in the specimen receded and the failure expanded towards all the directions from the inner rock face. With or without the inner pressure, the variation of the failure parameters such as the external pressure and the external volume strain can be divided into three stages.