The Research On The Tunnel Blasting Vibration With Equivalent Boundary:Combined With Accurate Loading Model

In tunnel and underground space blasting, the part of blasting energy can transform as blasting seismic wave and propagate in geomaterials, when this energy is more than a certain limit, it will produce the effects on the inner structure of host rock and existing structures. This effect may be cause the inner medium damage and destruction. In this paper, the base law of the blasting vibration phenomenon, the prodcing way and mechanism of propagation and the damage and act mechanism on the structures were systematically analysed.(1) Researching on the blasting gas pressure changing, the enlarging of blast hole volume, the developing of fracture and the gas motion, adopting the Chapman-Jouguet model, gas state equation and aerodynamics theory, to summarize the energy losing mechanism, to build the accurate form of blasting dynamic loading model with the time. In the view of this, considering the blast holes dimensions and wave superposition, the pseudo-three-dimensional dynamic loading model and dimensions was built.(2) Meticulous analysis on the different excavation ways, the blast hole can be divided as the cut hole and the other holes with second free face. Adopting the dynamic gradient theory, the scope and attenuation degree of crushed zone and fractured zone could be realized, hence, the blast hole, blasting crushed zone and blasting fractured zone can be regarded as equivalent elastic vibration boundary. Then, the work mechanism and scope of equivalent elastic vibration boundary can be obtained from the in-stiu test and numerical simulation.(3) The blasting energy can be divided into dissipated energy caused by the chemical wear and gas blow-out, effective mechanical energy for cutting the host rock and blasting vibration effect energy to generate the seismic wave. In this paper, considering the chemical wear and gas blow-out, the pseudo-three-dimensional dynamic loading model was built, and analyzing the crushed and fractured mechanism of host rock under the detonation pressure, the equivalent elastic vibration boundary was confirmed, hence, the dissipated energy and effective mechanical energy was removed respectively.The dynamic increase factor (DIF) can be obtained from the static load and dynamic load lab test and numerical simulation. In the view of this research, the elasticity modulus in elastic constitutive relation could be correction to solve blasting vibration analysis this dynamic problem.The wave length can be obtained from the in-situ monitoring tests, so that, the maximum largest dimension of element in the numerical simulation was confirmed. It is due to many influence factors, the blasting loading with equivalent elastic boundary value, which was accessed from the theoretical calculating could not be adopt directly. The transformation coefficient of the loading was rasied by the inverse analysis of simulation to eliminate affect from the influence factors. Therefore, with using huge in-situ monitoring data of velocity value, the local damping coefficient was obtained by adverse simulation.In the view of above analysis, a3D tunnel and structures model in software FLAC3D was built, alongside equivalent elastic vibration boundary, the mechanical parameter, pseudo-three-dimensional dynamic loading and constitutive model to predict the peak velocity and effective tensile stress, to build the elastic seismic field and analyze the damage of host rock, and the research on stabily of structures.