块系岩体滑移失稳中低摩擦效应的理论与试验研究

Theoretical and experimental research on the low-friction effect in slip stability of blocky rock mass

深部岩体具有块状层次结构,深部动载造成岩块发生相互间的振动脱离产生低摩擦效应,从而极易诱发原先处于平衡状态的岩体的动力变形破坏。在前人研究基础上,将块系岩体振动简化为等效质量-黏弹性模型,引入岩石摩擦滑移速率弱化模式,最终得到块系岩体滑移失稳计算模型。通过计算分析块系岩体自身特性及外荷载特性对岩块间低摩擦效应的影响。理论计算表明:水平静力及外扰动保持不变,增大岩块间弹性系数或者减小黏性系数,更容易引发岩体低摩擦滑移。随着冲击扰动、水平拉力幅值的增加,岩块的水平残余位移量值增加,当它们幅值超过一临界值时,岩块发生自持续滑移失稳运动。冲击扰动诱发岩块间不可逆位移、动力滑移失稳的临界能量与剪切力水平密切相关,在较大的剪切内力条件下,极其微弱的动力扰动即可诱发较大的岩块间不可逆位移甚至岩块的动力滑移失稳,随着剪切内力的减小,诱发岩块滑移失稳的能量阈值不断增大,当剪切内力低于岩块动摩擦强度时,单次冲击扰动只能诱发岩块间的不可逆位移。初步开展扰动诱发含初应力紫砂岩块体滑移试验,试验结果与理论计算基本符合,证明该模型的可行性。

Deep rock mass is a block-hierarchical structure.Dynamic events cause rock mass to be separated from each other during wave propagation,resulting in a low friction effect,which can easily induce the large dynamic deformation of the rock mass in the equilibrium state.Based on the previous studies,the vibration system of rock block is simplified as the equivalent mass-viscoelastic model,and the slip rate weakening mode of the rock friction is introduced.Finally,the calculation model of rock block slip is obtained.The effects of viscoelasticity property of soft medium between rock blocks and the external loads on the relative displacement of the working rock blocks are analyzed.Calculation results show that when the elastic coefficient increases or the cohesive coefficient decreases,the low friction slipping is more likely to occur.With the increase of the external disturbance or horizontal force,the horizontal residual displacement of the rock block increases,and when their amplitudes exceed a critical value,the sustained sliding instability occurs.The critical energy triggering irreversible displacement and dynamic sliding instability is closely related to the value of shear force.With large enough shear force,extremely weak disturbances can induce large irreversible displacement or even dynamic sliding instability between rock blocks,while a greater impact disturbance is required with smaller shear force.When the shear force drops to a value lower than the dynamic friction strength,a single impact load cannot induce dynamic sliding instability but only irreversible displacement.The horizontal dynamic response of the purple sandstone block under the combined effect of vertical impact load and horizontal static force is measured.The experimental results are basically consistent with the theoretical calculation,which proves the feasibility of the model.