The Study Of Stability And Safety Vibration Velocity Of Surrounding Rock Of Existing Tunnel On The Disturbance Of Blasting

In order to alleviate traffic pressure,A large number of single tunnel needs rebuild to double tunnel or build a new tunnel beside the existing tunnel.At this time,The surrounding rock and the structure of the existing tunnel will be inevitably damaged on the disturbance of blasting.How to ensure the surrounding rock of existing tunnel during the process of blasting has become an important project for successful construction.The study of stability and safety vibration velocity of surrounding rock of existing tunnel on the disturbance of blasting is still in the stage of development,mostly through the empirical formula and field test to guide engineering practice,and for the theoretical research of blasting vibration is still very inadequate.In order to explore the rules of dynamic response and safety vibration velocity of surrounding rock of existing tunnel on the disturbance of blasting,the paper use theoretical calculation and numerical simulation methods,and verified by field measurement and model test.The results obtained as follows:(1)In this paper,formula of safety vibration velocity of surrounding rock of existing schist tunnel are established based on elastic mechanics and structural mechanics.It is concluded that the tensile stress of surrounding rock at the most dangerous point gradually increases with the increase of the angle of rock stratum,the tunnel radius,the thickness of the over burden layer and the included angle of stratified rock mass at different rates,attenuation with the increase of the thickness of rock stratum,the power increases with the increase of the ratio of the tunnel radius to the thickness of rock statum,but when the product of included angle of stratified rock mass and the ratio of radius to thickness is fixed,the tensile stress is constant.At the same time,according to the theory criterion of maximum principal tensile stress,the calculation formula of the maximum vibration velocity of the most dangerous point is calculated,combined with the attenuation formula of vibration ofblasting particle,The maximum tolerant explosive quantity of single can be determined in blasting.(2)By establishing the mechanical model of the mechanical state of the key blocks in the surrounding rock of the existing tunnel,obtaining the formula of the safety vibration velocity of surrounding rock of tunnel.The safety vibration velocity is proportional to the value of mechanical parameters of the joints,and inversely proportional to the crack depth of the joint surface.Safe velocity and the impact that the static lateral pressure coefficient on it decreases with the increase of block length,At the same time,the changes of rock static lateral pressure coefficient have an affect on the security area of surrounding rock mass.In addition,the average lateral pressure of the key block is proportional to buried depth of the hole and is influenced by the hole diameter and the height of the block.(3)By analyzing numerical simulation result and real data of the Ten White High-speed engineering,it is concluded that the direction of the peak value of vibration velocity and tensile stress are perpendicular to each other,and it has some proportional relationship in a special range,which have guiding significance for the layout of monitoring points in practical engineering.(4)Through the model test,It is concluded that the conclusion that the direction of the peak value of vibration velocity and tensile stress are perpendicular to each other has been verified.And the ratio between them is obtained.