Study On Propagation Law Of Pendulum Wave Force In Deep Rock Mass

The pendulum wave phenomenon occurs in the block rock mass,and its characteristics are quite different from the elastic wave in the continuum.Studies have shown that the pendulum wave has the characteristics of nonlinearity,low frequency and low speed,and carries large energy,which is easy to cause various engineering geological disasters such as rock burst.Therefore,studying the pendulum wave problem has far-reaching significance for improving engineering design and preventing engineering disasters.Based on the dynamic model of pendulum wave propagation in one-dimensional block rock mass,this thesis conducts four theoretical researches.First,the effects of the stiffness,viscosity and block size of the weak interlayer on the energy dissipation and conversion in the block system are studied;secondly,the effects of half-sine shock loads with different loading rates on the pendulum wave propagation are studied;The dynamic propagation model of the shape wave,the new model considers the shear effect of the joints in the vertical direction of the block vibration,studies the shear effect of the anisotropy,and explores the effect of the positive and negative shear stiffness ratio on the propagation of the pendulum-shaped wave.The hyperbolic function model of joint shear strength is used to explore the influence of impact load and y-direction normal stress on the propagation of pendulum waves.Finally,the BB hyperbolic function model of joint normal deformation is introduced,and the propagation law of pendulum waves in different grades of block rock mass is explored in combination with the theory of grade block rock mass structure.The following are the main conclusions of the study.(1)The stiffness coefficient affects the decay period of the system kinetic energy and elastic potential energy.The larger the stiffness coefficient is,the smaller the decay period of the system kinetic energy and elastic potential energy is.The viscosity coefficient affects the decay rate of the kinetic energy and elastic potential energy of the system.The larger the viscosity coefficient is,the lower the peak value in each decay cycle,and the faster the system kinetic energy,elastic potential energy and total energy decay.As the block level increases,the decay period of kinetic energy and elastic potential energy becomes larger,that is,the conversion period of system kinetic energy and elastic potential energy becomes larger,and the energy peak value of each decay period decreases significantly,and decay faster.(2)The greater the impact load loading rate is,the stronger the response of the displacement,velocity and acceleration of the block are,and the faster the decay speed is,but the response period remains unchanged.The larger the impact load loading rate is,the more energy the block system absorbs during the impact process,and the block system remains in a high-energy state for a longer time.When the loading rate is small,the impact load will hinder the reverse movement of the first block,so that the energy decay becomes faster,and the decay curve of the system energy appears in a fast decay segment.(3)First,the anisotropy of shear deformation is studied,that is,the positive shear stiffness and negative shear stiffness are different.At this time,the displacement response,velocity response and acceleration response have the following characteristics: when η=0,the positive and negative amplitudes of the block are basically symmetrically distributed;whenη>0,the negative amplitude is greater than the positive amplitude,and the positive displacement is limited;when η<0,the positive amplitude values are greater than the negative amplitude,the negative displacement is limited.On considering the joint shearing effect,the overall stiffness of the system increases,which is reflected in the frequency domain curve as an increase of the number of the peak points,while the frequency spectrum moves to the high frequency region,and the low frequency characteristics of the pendulum wave are weakened.When the impact load is larger,the shear displacement is larger,and the shear stiffness is smaller,which results in a larger vibration period of the block,and the frequency domain response curve of the acceleration shifts to the low frequency region.As the normal stress in the y direction increases,the frequency domain curve moves to a high frequency region,and the low frequency characteristics of the pendulum wave are weakened.(4)After introducing the BB hyperbolic function model of joint normal deformation,the compressive deformation of the weak interlayer is limited to the maximum joint closure amount,and the negative and positive displacement curves of the block are no longer symmetrically distributed,and the negative displacement value greater than the positive displacement amplitude.When the impact load is larger,the compressive deformation of the interlayer is larger,and the deformation stiffness becomes larger at this time,so it is reflected in the displacement response curve that the amplitude and decay period both increase.With the propagation of the pendulum wave,the energy is gradually dissipated,and the deformation of the interlayer decreases,so the deformation stiffness also decreases,and the decay period of the dynamic response of the block increases.After introducing the BB hyperbolic function model of joint normal deformation,the response curve of the acceleration has obvious clustering phenomenon,and the time interval of the clustering phenomenon is consistent with the decay period of the block displacement and velocity.The larger the size of the block is,the larger the corresponding interlayer thickness and the deformable range are.Under the same impact,the dynamic response period and amplitude of the block become larger.The above research has deepened our understanding of the dynamic properties of the deep level block-rock mass,and is of great significance for ensuring engineering safety,and promoting economic development.