Experimental Study On Ground Vibration Propagation Law Of Shallow Buried Tunnel

In this paper,the jianzi mountain tunnel blasting construction as the engineering background,by real time vibration test of blasting field,combined with matlab wavelet analysis software and model test research on the propagation and attenuation characteristics of shallow tunnel excavation blasting ground vibration.The main contents and conclusions are as follows:(1)By the jianzi mountain tunnel blasting vibration test,it is found that subsection of seismic waves generated by the millisecond blasting in shallow tunnels are not obvious,intersegment intervals to reach 100 ms or more can avoid the phenomenon;when blasting in shallow buried tunne,blasting vibration intensity of cut hole is usually the largest.(2)Along axis of the tunnel,with the horizontal distance increasing from tunnel face,the front and back corresponding measuring points of the tunnel face of vibration velocity amplification coefficient increased firstly and then decreased,when the horizontal distance is 12 m,the maximum value is 1.37,and the vibration speed difference also increases first and then decreases;along radial of tunnel,with the increase of lateral distance,the front and back corresponding measuring points of the tunnel face of vibration velocity amplification coefficient show a decreasing trend generally,to the excavation boundary,and the vibration speed magnification factor is reduced to less than 1.1 times.(3)The minimum error of wavelet reconstructed signal and the original signal test,signal frequency band of wavelet decomposition ca n effectively carry out research on monitoring signal;with the interval from low frequency to high frequency band interval,vibration signals in various frequency bands length decreased with frequency interval;interval from low frequency to high frequenc y,the peak vibration velocity of each frequency band signal decreased.(4)Sadaovsk formula for the vibration velocity in shallow buried tunnel blasting face in front of the surface vibration velocity prediction,does not apply to the rear of the tunnel face surface prediction;prediction method of all measuring points in front of the tunnel face behind the predicted average relative error is 8.93%,by using BP neural network,in front of the tunnel face without excavation of the average relative error of data area forecast of 8.98%,the prediction accuracy is higher than the Sadaovsk formula prediction method,The average relative error of the predicted data in the backhand excavation area was 8.89%,BP neural network is applied to the front and back side of surface vibration velocity prediction of tunnel face.(5)The blasting vibration propagation law of jianzishan tunnel is studied by model test.The results show that the ground vibration propagation of the model test is consistent with the ground vibration propagation of the tunnel blasting,and the effect of hollow effect on the axial and radial direction of the tunnel about model and field is consistent.Along the axis and radial direction of the tunnel,with the increasing of the tunnel face blasting explosive,the front and back corresponding measuring points of the tunnel face of vibration velocity amplification coefficient and vibration velocity difference show a increasing trend;with the increase of the buried depth of the tunnel,along the axis and radial direction of the tunnel,the front and back corresponding measuring points of the tunnel face of vibration velocity amplification coefficient and vibration velocity difference show a decreasing trend generally.