冲击地压巷道锚杆-围岩系统复刚度特性

Complex stiffness characteristics of bolt and surrounding rock system in bump-prone roadways

为探讨冲击载荷作用下锚固围岩体动力失稳机理与能量耗散机制,基于振动力学理论,建立锚杆-围岩在冲击载荷作用下的三维轴对称力学模型,获得了冲击载荷作用下锚杆-围岩系统复刚度的解析表达.从抵抗变形与能量耗散两个方面,分析了冲击地压发生时锚杆-围岩系统的动力响应特征.结果表明:在相同频率的冲击载荷作用下,随着围岩黏性阻尼、围岩强度以及锚固长的增加,锚杆-围岩系统复刚度越大,抵抗纵向变形能力越强,应力波能量耗散越快,系统吸能特性越好;随着冲击载荷频率的增加,围岩强度与黏性材料阻尼对锚杆-围岩系统复刚度影响更为明显;全长锚固条件下,锚杆-围岩系统抵抗纵向变形能力几乎不受冲击载荷频率控制.采用数值分析验证了理论分析的正确性.建议采用围岩注浆改性与锚杆全长锚固方式,提高冲击载荷作用下锚杆-围岩系统抵抗冲击变形能力与增强系统阻尼耗能性能.

To investigate the dynamic instability mechanism and energy dissipation mechanism of bolted rock mass under the action of impact loads,a three-dimensional axis-symmetry model of bolt and surrounding rock affected by impact loads was established based on vibration mechanics theory,and then analytical solution of complex stiffness of bolt and surrounding rock system were obtained.When coal bump occurred,dynamic response characteristics of bolt and surrounding rock were analyzed in terms of resistance to deformation and energy dissipation.The results show that,with the increasing of viscous damping,strength of surrounding rock and anchored length,the complex stiffness and resistance capacity for deformation of supporting system grow larger,the stress wave energy dissipation become faster and the absorptionperformance of the system gets better.The action of viscous damping and strength of surrounding rock on complex stiffness is more obvious with the increase of impact load frequency.For the full column anchoring,resistance to vertical deformation of bolt and surrounding rock system is almost not affected by impact loads frequency.And the correctness of the theoretical analysis is verified by numerical analysis.The modification of the grouting and full column anchoring were recommended to improve resistance to deformation and enhance damping performance of bolt and surrounding rock system under the action of impact loads.