Overbreak and underbreak in underground openings Part 2: causes and implications |
| |
Authors: | J. A. Ibarra N. H. Maerz J. A. Franklin |
| |
Affiliation: | (1) Excavaciones Soporte Y Tecnologia, Zapopan, Jal., Mexico;(2) N.H. Geo Consulting Limited, Kitchener, Ontario, Canada;(3) Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, Canada |
| |
Abstract: | Summary The newly developed light sectioning method has been used to investigate some of the causes and costs of overbreak and underbreak. Investigations at the Aquamilpa Hydroelectric Project in Mexico have shown decreased overbreak and increased underbreak as a result of increased rock quality and decreased explosive energy. A new measure of explosive energy, the perimeter powder factor (PPF), has been defined and shown to be useful in the context of tunnel-wall rock damage. Tentative results indicate that explosive energy (PPF) may be a more important factor in producing underbreak, whereas rock quality may be a greater factor in producing overbreak. A site-specific equation is given for predicting overbreak or underbreak as a function of rock quality and explosive energy, with an evaluation of the cost of underbreak and overbreak. |
| |
Keywords: | overbreak underbreak digital image processing tunnelling blasting assessment tunnel profiling RMR Q powder factor perimeter powder factor |
本文献已被 SpringerLink 等数据库收录! |
|