Evaluation The Influence Of Tunnel Excavation Blasting On Ancient Great Wall

With the rapid development of the national economy and the updating of infrastructure,blasting technology has been applied to engineering activities more and more.At the same time,blasting construction threatens the safety and stability of buildings and environment near the blasting site while achieving the project goals.In particular,the impact evaluation and control of ancient buildings and other historical and cultural monuments with long history and significant historical and cultural significance have been threatened.Become an urgent problem in the project.Based on the excavation of the Hongshimen tunnel of Chengping Expressway,the article studied the impact of excavation and blasting construction of the tunnel on the Great Wall.Therefore,according to the existing engineering experience and research results,the relationship between blasting explosive charge and blasting impact load is selected.According to the layout of blasting holes and charging methods commonly used in tunnel excavation blasting,the blasting load of tunnel surrounding rock is determined by taking into account the time sequence of blasting excavation and the process and effect of explosive detonation.The finite difference software FLAC^3D was used to simulate the influence of tunnel excavation blasting vibration on the Ming Great Wall above the tunnel.Referring to the vibration threshold of buildings specified in the relevant specifications,the safety of the Great Wall at the time of blasting with a designed total dose was evaluated.Through the above research,the following achievements and understandings have been achieved in this study.?1?When blasting directly under the Great Wall,the peak vibration velocity V_zmax,V_ymax and V_xmax of the three component time course of the rock mass at the top of the tunnel blasting face are negatively correlated with the burst center distance r.With the increase of r,V_zmax,V_ymax and V_xmax decrease as a function of power.?2?When the blasting is underneath the Great Wall,the variation of the three component peak velocity of V_zmax,V_ymax and V_xmax of the Great Wall foundation varies.The maximum value of V_zmax near the blasting face is symmetric and attenuated to both sides.V_ymax and V_xmax get minimal value near the top of the blasting face.Along the Great Wall foundation,the fluctuation of the foundation is fluctuating,and the change trend of V_xmax is similar to that of the letter"M".Considering the topography of the mountain and the heterogeneity of the medium,the radiation characteristics of the blasting source are basically consistent with the radiation characteristics of the single source wave field.?3?In the process of excavation,the variation of the three component peak velocity of V_zmax,V_ymax and V_xmax of the Great Wall foundation is similar to that under the direct blasting.?4?When the slot hole is divided by two batches of total dosage,the vertical peak vibration velocity V_zmax of the Great Wall Foundation during the excavation process is less than 1mm/s,which satisfies the requirements of the“Blasting Safety Regulations”specification.The peak values of the horizontal component peak vibration speeds V_ymax and V_xmax exceed the 0.2 mm/s specified in the specification during the excavation process and cannot meet the safety-allowed blasting vibration speed limit.