THE EFFECTS OF UNDERGROUND BLASTING ON NEARBY PRE-EXISTING STRUCTURES

Butte, Montana holds a prestigious place in the history of mining, deemed “The Richest Hill on Earth,” containing a plethora of underground mines. The Orphan Boy/Orphan Girl underground mines, on the western side of Butte, operated from 1895-1956 producing zinc, lead, silver, and manganese. Today, the Orphan Boy mine is part of Montana Tech’s Underground Mine Education Center (UMEC) and the Orphan Girl mine houses the World Museum of Mining. Underground development in the Orphan Boy mine continues to progress as students from Montana Tech receive hands-on underground training; in addition, the UMEC is a multi-disciplinary research facility. Repeated underground blasting occurs in close proximity to old mine workings (wood supports installed circa 1950 or earlier). Research began to determine the impact of underground blasts on nearby pre-existing structures. Using the ISEE Field Practice Guidelines for Blasting Seismographs, one seismograph monitors the predominately-wooden structures to measure their response during each underground blast and one seismograph is positioned on the surface to monitor surface structure response to the blast. Thirteen underground blasts were monitored, and the resulting general conclusion was that the blasts were not causing structural damage to the nearby pre-existing structures. Recorded peak particle velocities from ground vibrations generated from the underground blasts interacting with the pre-existing structures ranged from 0.150 in/s to 2.20 in/s. All 13 blasts fell below the mining industries standard USBM RI 8507 damage threshold. This paper presents the findings of the research conducted to date for the project, includes analysis of the research data, additional conclusions determined from the research. Recommendations for the future work are included as well