Study On Dynamic Response Characteristics Of Surrounding Rock And Supporting Bolts Under Blasting Excavation

As an efficient and inexpensive construction method,drilling and blasting method has been widely used in the construction of large-scale underground projects such as tunnels and mine roadways.The seismic effects caused by blasting is inevitable to cause the hazard effects on the surrounding rock and the supporting structure of the explosion source caverns.Therefore,it is necessary to analyze the seismic effect of tunnel blasting and the stability of surrounding rock as well as the supporting bolt.The damage failure zone of surrounding rock under transient blasting unloading effect,the propagation attenuation law of vibration waves and the dynamic response characteristics of supporting bolts in the underground tunnel are mainly studied in this paper.The main research results are as follows.(1)The Elastic dynamics is used to solve the dynamics analytical solutions of stress field under transient blasting unloading around the deep rock roadway.Combined with the tensile and shear damage threshold condition,the damage failure zone and the damage degree of the blasting transient unloading of the deep rock tunnel were given,and the factors impacting on distribution of damage zone were discussed.The study shows that the surrounding rock failure zones induced by transient blasting unloading is mainly composed of tensile failure.For the same conditions,the more brittle the rock is,the larger the damage value will be.The bigger the blasting load is,the bigger the tensile and shear damage failure zone will be.The tensile damage effect is obviously inhibited by the in-situ stress in surrounding rocks.(2)By simplifying blasting loads and in virtue of the separation variable method,the propagation attenuation law of vibration waves in surrounding rock for a specific axis coordinate system is obtained,and the influence of blasting parameters on propagation law is discussed.The results show that the vibration in surrounding rock appeared the interaction of the sign wave attenuation with the increasing of radial distance,and negative exponent attenuation with the increasing of axial distance.Moreover,the vibration attenuates more quickly and intensely in the near blasting field,(3)The analytic solution of vibration law of supporting bolt under blasting seismic wave is solved by the method of structural dynamics theory.The vibration response characteristics of bonding anchor bolts under blasting is analyzed.The result shows that the velocity and axial force of free length attenuate exponentially.However,the velocity,axial force and sheer stress of free length show sinusoidal variation,it performs first increase then decrease overall.(4)In virtue of underground engineering model test system,the three-dimensional dynamic loading physical model experiment is carried out.The conventional explosives is replaced by spark source,and the propagation attenuation law of vibration waves and the dynamic response characteristics of supporting bolts are analyzed.By comparing the experimental results with the analytical results,the rationality of theoretical calculation results is verified.These research results not only have important theoretical significance,but also can provide predictability guidance for the design of supporting structure.