Causes, impact and control of overbreak in underground excavations

DOI

10.2991/rare-16.2016.4How to use a DOI?

Keywords

rock mass damage; blasting; overbreak; Maximum charge per delay; scale effect

Abstract

Drilling and blasting has been a preferred method of rock excavation world-wide. Blasting inevitably causes damage to the peripheral rock mass, which culminates in the form of overbreak and damaged zone. Damage or overbreak not only endangers the safety of structure and cost escalation but also delayed completion. Too large damage zone endangers the safety of the front line workers due to reduction of stand-up time especially for poor rock mass. Functionality and post-construction performance of structures get affected due to large extent of damage zone, if not taken care in time. Field investigations were carried out at five different Himalayan tunnels to formulate an empirical equation for predicting blast-induced overbreak for wide range of rock mass quality wherein Q values ranged between 0.03 and 17.8. The proposed equation involves parameters like specific charge, perimeter charge factor, maximum charge per delay, rock mass quality (Q), advancement and confinement factors. These parameters are readily available at the site without any difficulty. Nearly 113 experimental blasts were monitored and data so collected were used to formulate an index termed as scale effect (Si), which is the ratio of tunnel cross-sectional area and block size of rock mass. It is revealed that when Si becomes greater than 4, the range of overbreak lied between 8 and 25%.

Copyright

© 2016, the Authors. Published by Atlantis Press.

Open Access

This is an open access article distributed under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

Download article (PDF)

TY  - CONF
AU  - H.K. Verma
AU  - R.D. Dwivedi
AU  - Roy P. Pal
AU  - P.K. Singh
PY  - 2016/11
DA  - 2016/11
TI  - Causes, impact and control of overbreak in underground excavations
BT  - Proceedings of the conference on Recent Advances in Rock Engineering (RARE 2016)
PB  - Atlantis Press
SP  - 29
EP  - 34
SN  - 2352-5401
UR  - https://doi.org/10.2991/rare-16.2016.4
DO  - 10.2991/rare-16.2016.4
ID  - Verma2016/11
ER  -