Impact Study On Overlapping Tunnel Construction Blasting

Rock blasting is widely used in slope construction, tunneling and mining areas of the construction.In the project implementation process of blasting seismic waves affect the stability of rock ,and will produce severe damage to existing structures. Based on construction environmental conditions of Nanshan tunnel, Studied the tunnel blasting vibration effects on the lower part of the tunnel, and put forward blasting vibration control methods. It has become an urgent problem to be solved in construction blasting, which included reducing the quantities of explosives, reducing rock damage, effective conducting blasting.Simulated tunnel blasting vibration to optimize the design of the blasting program, in-depth study explosives in rock blasting laws in overlapping tunnel construction process based on finite element program MIDAS/GTS in this paper. Here are some conclusions:(1) Researched a variety of rock blasting theory and mechanism and different detonation manner of charging structure; derived the relevant equations, analyzed the blasting mechanism and the charge blasting methods; studied advantages and disadvantage of various rock crushings models.based on the results of previous studies.(2) Develop a program for blasting under the mechanical properties of rock blasting site; analyzed blasting seismic wave field data to determine the reasonableness of blasting program through field tests,. results show that the closer seismic waves from the explosion source the faster attenuated, the farther away from the explosion source, the more slowly seismic wave attenuation; the position of wall is the largest velocity inside the tunnel , the maximum vertical velocity of the particle is 6.98 cm/s, the master oscillator frequency is 59.68Hz. The speed of each monitoring point values are not exceeded the design standard value.(3) Used dynamic finite element software MIDAS / GTS simulated tunnel blasting. Results show that: the vault position facing the blasting side is the most dangerous parts of the existing tunnel, whose vertical vibration velocity and displacement values were significantly higher than other parts, is mainly exposed to the blast loading area. The existing tunnel vault is mainly affected by vertical vibration, its maximum vertical velocity is greater than the level of velocity. The maximum value is 6.7732 cm/s.(4) Compared and analysis the field monitoring data and simulation results of blasting vibration. Here are some conclusions: particle velocity increases with the explosion center distance increases firstly and then decreased, the stress of particles are superimposed but its load does not lost, so its displacement have very little change. Both the vertical and horizontal displacement of nodes near the constraint boundary have a greater changes, the opposite direction of the vertical displacement is smaller than the positive direction; when a node near the explosion source, the faster its acceleration values attenuation, the more oscillation intense.