Impact Analysis Of Shallow Tunnel Excavation Blasting To Adjacent Existing Dam Safety

In the process of drilling blasting in shallow tunnel,the influence of blasting construction on surface construction is complicated due to the close distance between surface construction and explosion source.Tunnel excavation blasting is a repetitive and long-term process,frequent blasting construction will cause the foundation settlement,structural damage and even cause the building to collapse,a direct threat to the people life and property safety around the tunnel.Therefore,the propagation law of seismic wave caused by excavation blasting of shallow tunnel and the dynamic response of dam under the blasting load is analyzed,and the safety of dam is evaluated under blasting load.With the Douziwan tunnel close to the Qiaoqiaowan reservoir section for the project background,the results of surface and dam vibration monitoring of tunnel excavation blasting are analyzed and the following conclusions are obtained:The main vibration phase in the vibration waveform of tunnel excavation blasting are clear,The cut hole charge is not the maximum single-stage charge,but the peak vibration velocity of the cut blasting hole is more than 2 times the peak velocity of other holes.The peak vibration caused by the shallow tunnel excavation blasting consistent with Sadowski's empirical formula in the direction perpendicular to the tunnel axis,the site coefficients of the three vertical direction were:140.5,88.3,109.5 respectively;attenuation index were:1.7475,1.6254,1.6706 respectively.Blasting seismic waves through the surface of strong weathering rock,reservoir bottom silt and reservoir water storage on the vibration frequency of the filter,when the vibration wave propagates into the position of the dam,the vibration frequency gradually becomes stable,mainly in the low frequency range of 18Hz?35Hz.The LS-DYNA software was used to simulate and analyze the excavation and blasting of Douziwan tunnel,As the incident angle of the blasting seismic wave to the measuring point is different,the peak velocity increases with the increase of the propagation distance in the X axis direction,and the maximum peak velocity appears at the distance of 15 m from the source.In the X-axis direction,the peak velocity increases with the increase of the propagation distance,and the maximum peak velocity appears at the horizontal distance of 15m.The maximum peak velocity of the three vertical directions of the dam is 0.53cm/s,0.31cm/s and 0.54cm/s respectively in the tunnel single cycle footage 1.5m excavation blasting construction.The maximum value appears in the top position of the dam body,and the peak velocity of each point in the dam body is less than the safe peak velocity of the dam.