Vibration Effect Analysis of Downhole Pre-splitting Blasting Based on VMD-HHT
The current mining method employed at Dahongshan copper mine in Yuxi,Yunnan Province utilizes the large blasting technology of sublevel open-stope subsequent filling method.However,due to the excessive amount of explosive used in each blast,significant damage is inflicted upon the retained rock mass which ultimately affects stope stability.In order to address this issue,a more holes and less charge approach has been implemented whereby dense blast holes are arranged at a certain distance from the retained rock mass and single hole charges have been reduced.Prior to detonating the main detonation zone,these rows of holes are first detonated thereby creating a gap with a specific width that serves to minimize damage inflicted upon the retained rock mass.The variational mode decomposition and Hilbert-Huang transform(VMD-HHT)method was employed in this study to analyze the field-measured blasting vibration signals.The results show that the instantaneous energy distribution of the pre-splitting vibration signals primarily concentrates within the time range of 0 to 0.5 seconds,while the frequency distribution predominantly lies within the range of 40 Hz.The combined velocity of the three measuring points is used to calculate the vibration reduction rate,and the vibration reduction rates of the three measuring points are 21.0%,30.1%and 38.5%,respectively,which effectively reduces the damage and destruction of blasting vibration to the retained rock mass.
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