Quantifying the effect of rock mass quality on peak particle velocity for underground drift development

• Main Author: Caceres, Cristian Andres Caceres
• Language: English
• Published: University of British Columbia 2012
• Online Access: http://hdl.handle.net/2429/39861

In prior research the existence of the strong relation between peak particle velocity (PPV), as a result of blasting, and damage to civil structures and mining excavations has been well established. In essence, the higher the PPV levels, the greater has been the observed damage to a structure or excavation. The first part of this thesis examines, through case studies in four underground mines, the relationship observed between measured PPV and induced overbreak. These developed relationships were established through a blast monitoring campaign of drift development headings of markedly dissimilar rock mass qualities, varying from fair/poor to extremely competent. In the second part of this thesis is developed of a new methodology to estimate PPV, which incorporates input parameters that are characteristic of different rock mass qualities, such as propagation velocity and resonance frequency, and explosive characteristics such as velocity of detonation (VOD). This methodology makes use of waveforms to determine vibration levels from which the PPV of a blasthole is established. The developed model estimates PPV by taking into consideration the spatial location of the blasthole with respect to both the drift face, and the point of interest, and the arrival time difference of every incremental charge (or packet) within a blasthole based on the travel distance of the seismic wave, the VOD, and the rock mass propagation velocities. Current state of the art methodologies are solutions to a particular blasting situation; they either consider a specific close range geometry, where they have limited applicability, or they tend to be over simplified in the far-field by considering the explosive charge as a point source. The proposed methodology considers a more realistic close range geometric solution that can be applied specifically to a drifting situation, and improves some of the drawbacks of current methodologies in the far-field range. Finally, a more reliable estimation of PPV levels can help in the assessment of the damage potential of a particular structure or excavation and therefore should help toward preventive measures to make the working environment more safe and cost effective.