Influence Of Blasting Vibration On Goaf And Prediction Of Vibration Velocity Based On East Open-pit Mine

Because of the integration of underground mines, there are a number of unknown goafs left over in the stope of East Open-pit mine. The goafs collapse under the influence of blast vibration in production process, and trigger industrial accidents in the field. In order to select blast paremeters, control blast vibration and guarantee the security of goafs, it is of vital importance to analyze the impacts of blast vibration to the stability of goafs, and to establish the prediction model of blast vibration.The vibration velocity monitoring in the ground was carried out, and compared with the numerical simulation predictive vibration velocity, which prove correctness of the established model of blasting vibration. The software LS-DYNA was employed to build three-dimensional model for blast vibration with different parementers, the influence of blast vibration to the goafs was analyzed, and the fitted prediction formula of the vibration velocity on the goaf roof was obtained. The principal research contents are as following:(1) The PPV in the ground is larger with a goaf in the underground, but only to some extent. The goaf increases the duration of blast wave, generates multi wave crests in the waveform, and aggravates the damage of blast vibration to the structures in the ground.(2) Comparison between the numerical simulation of blast vibration and the in situ recorded signals in the ground showed that the attenuation law of vibration velocity and the time-history velocity curve are consistent with field monitoring, and that the average error of peak particle vibration is 7.4 %. It is verified that the selected constitutive model, material parameters for the rock mass and the established model for blast vibration was correct and reliable.(3) The damage under blast vibration occurs primarily on the roof of goafs, and the sidewall closer to the blast side comes second. The horizontal component of the roof vibration induces the most severe damage to the goafs. While the particle velocity on the roof gradually decreases with the increase of the horizontal distance to blast holes, the particle velocity on the sidewall closer to the blast side decreases after an increase with the increase of horizontal distance, yielding the maximum with distance 20 m. The sidewall closer to the blast side is the most susceptible to damage. While the horizontal particle velocity decreases after a slight increase with the burial depth, with the maximum velocity at the depth of 35 m, the particle velocity on the sidewall closer to the blast side decreases with the burial depth. The peak particle velocity(PPV) increases with the spacing of goaf roof, and maintains an inconspicuous increasing trend when the spacing exceeds 30 m.(4) The primary influence factors of blast vibration include the maximum segmental explosive charge, the burial depth of goafs, the horizontal distance from goafs to blast holes and the spacing of goafs. The basic variable of dimension analysis was determined, and the blast-induced vibration prediction model of underground goafs was established using the dimension analysis.The vibration velocity prediction formula of goafs obtained from fitting was adopted to predict the particle velocity on the roof of goafs, which in turn could serve as the distinguishing criterion of stability of underground goafs under the influence of blast vibration. The maximum vibration velocity to guarantee safety was determined, and the maximum charge weight could be obtained in inversion, which can provide theoretical guide for in situ blast construction design.