Theoretical and numerical study on reinforcing effect of rock-bolt through composite soft rock-mass

复合软岩穿层锚固效应的理论和数值模拟研究（英文）

Anchoring mechanism and failure characteristics of composite soft rock with weak interface usually exhibit remarkable difference from those in single rock mass.In order to fully understand the reinforcement mechanism of composite soft roof in western mining area of China,a mechanical model of composite soft rock with weak interface and rock bolt which considering the transverse shear sliding between different rock layers was established firstly.The anchoring effect was quantified by a factor defined as anchoring effect coefficient and its evolution equation was further deduced based on the deformation relationship and homogenized distribution assumption of stress acting on composite structure.Meanwhile,the numerical simulation model of composite soft rock with shear joint was prompted by finite element method.Then detailed analysis were carried out for the deformation features,stress distribution and failure behavior of rock mass and rock bolt near the joint under transverse load.The theoretical result indicates that the anchoring effect of rock-bolt through weak joint changes with the working status of rock mass and closely relates with the physical and geometric parameters of rock mass and rock bolt.From the numerical results,the bending deformation of rock bolt accurately characterized by Doseresp model is mainly concentrated between two plastic hinges near the shear joint.The maximum tensile and compression stresses distribute in the plastic hinge.However,the maximum shear stress appears at the positions of joint surface.The failure zones of composite rock are produced firstly at the joint surface due to the reaction of rock bolt.The above results laid a theoretical and computational foundation for further study of anchorage failure in composite soft rock.

复合软岩的锚固机理及锚固失效特征不同于单一岩体锚固。针对西部矿区复合软岩顶板锚固问题,考虑岩层间的横向剪切滑移,建立了含软弱界面复合软岩锚固的力学模型;提出采用锚固效应因子量化穿层锚杆的锚固效应;从加锚复合岩体的变形破坏过程出发,研究了系统锚杆的加固效果与机理,建立加固效果演化方程;采用有限元方法,进一步建立了复合软岩锚固的数值计算模型,分析了岩体在横向载荷作用下,节理面附近锚杆和岩体的变形特征、应力分布规律以及破坏行为。理论研究结果表明,穿层锚杆的加固效应与锚杆的刚度参数、几何参数,围岩的刚度参数和几何参数据有关。锚固效应因子是一个随着围岩工作状态改变而变化的量。从数值计算结果看,锚杆在横向荷载作用下的弯折变形主要集中在节理面附近的两塑性铰之间,变形曲线可用Doseresp模型进行表征;在2个塑性铰处,锚杆存在最大拉压应力,在节理面处,出现最大剪应力,复合岩体在节理面附近由于锚杆的反作用最先出现塑性破坏区。以上结果为进一步研究复合软岩锚固失效奠定了理论和计算基础。