Study On Attenuation Law Of Blast Wave In Tunnel Excavation And Its Application

Tunnel excavation blast wave propagation along the tunnel,Because of its limited propagation space,the attenuation is slower and the propagation distance is longer than the open blasting.In order to prevent damage to the personnel and equipment caused by blast wave,personnel and equipment must be evacuated at the time of blasting.However,in the construction of a long tunnel,it is impossible for all personnel to evacuate the tunnel,therefore,a reasonable evacuation distance needs to be determined.The research on the attenuation law of blast wave plays an important role in protecting personnel safety.In this paper,field tests and numerical simulation methods are used to study the attenuation law of blast waves.Due to the specific conditions such as parking of construction equipment,stacking of materials and changes in tunnel cross-section at the tunnel excavation site,the attenuation of blast waves in tunnels is complicated.Existing experiential formulas for calculating overpressure in tunnels may not be applicable.Therefore,a field test was conducted.A blast wave tester was used to measure the overpressure at different charge and different propagation distances.Through the processing of the test data,the parameters of the existing empirical formulae were modified,and the empirical formula suitable for tunnel excavation blast wave overpressure was obtained,the applicable conditions were also given.According to the formula,warning distances and evacuation distances for non-operators are given for different charges.Convert overpressure values into more intuitive distance standards.The nonlinear dynamic analysis software AUTODYN was used to establish two kinds of calculation models for numerical simulation of tunnel blast wave propagation.Through the function of the software,the process of blast waves in tunnels from the explosion of explosives to the formation of flat wave.The blast wave morphology and the variation of overpressure with propagation distance were analyzed.At the same time,by simulating the propagation of blast wave in tunnels with cross-section changes,the effect of cross-section changes on the propagation of blast waves is clarified.