基于改进颗粒流声发射片的地下厂房洞室围岩局部损伤细观机制研究

Meso-mechanism of surrounding rock local damage of underground powerhouse cavern based on improved particle flow acoustic emission sheet

通过改进的PFC-FLAC离散-连续耦合计算方法,提出了一种基于FLAC连续模型耦合区域节点速率双线性插值的PFC颗粒流声发射片模拟方法以及基于声发射强度的围岩破坏区深度细观角度判别方法,并将其应用于地下厂房洞室开挖面、岩锚吊车梁与岩壁接触面等局部围岩损伤细观机制与破化特性研究。研究结果表明:浅层围岩接触力链逐渐稀疏,大量微裂纹发育并汇集成宏观裂隙,最终出现浅层破裂区,呈拉裂破坏;随着距离开挖面的增大,围岩从开挖前期受力较大产生破坏、到开挖后期只有少量微裂纹产生,对应了围岩回弹卸荷区深度。在岩壁围岩劣化和吊车梁超载的情况下,吊车梁与岩壁竖直接触面和倾斜接触面分别发育大量拉裂纹和剪裂纹,宏观表现为拉裂破坏与滑移破坏。上述分析结果与三维有限元方法相一致,并弥补了后者围岩破坏显示方法单一、难以描述围岩损伤程度变化的缺点,为研究地下厂房洞室大变形与应力集中部位的宏细观特性与损伤机制提供参考。

Based on improved PFC-FLAC numerical simulation method, this paper presents an improved particle flow acoustic emission(AE) model based on bilinear interpolation of nodal velocity in coupled region of FLAC model, and a method for judging the depth of rock mass failure zone according to the AE intensity. Both methods have been applied to studying the meso-mechanism of local rock damage and destructive characteristics for excavation surface of underground powerhouse cavern and contact surfaces of rock-anchored crane beams. The results show that the contact force chain of the shallow surrounding rocks is gradually sparse, and a large number of micro-cracks develop and merge into macro-cracks, and finally a shallow fracture zone appears, showing tensile fracture;with the increase of distance from the excavation surface, the surrounding rocks are damaged due to the large force at the early stage of excavation, and only a few micro-cracks are generated at the later stage, which correspond to the depth of rebound unloading zone. When the surrounding rocks deteriorate and crane beam is overloaded, numerous tensile and shear cracks will respectively develop on the vertical and inclined contact surfaces between the crane beam and surrounding rocks, which are macroscopically manifested as tensile fracture and slip failure. The above results are consistent with the three-dimensional finite element method. The proposed method also solves the problems of the finite element method that there is merely a single display method for surrounding rock damage and it is difficult to describe the changes of rock damage degree. This study provides a reference for investigating the macro-and meso-scopic characteristics and damage mechanism of large deformation and stress concentration areas of underground powerhouse caverns.