1、FROM: PURE AND APPLIED GEOPHYSICS,1998.6,10（1）：4165附录Use of Microseismic Source Parameters for Rockburst Hazard AssessmentJANE M. ALCOTT1, PETER K. KAISER1 and BRAD P. SIMSER2 1.Geomechanics Research Centre, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada. 2.Noranda Mining and Exploration L
2、td., Brunswick Mining Division, P.O. Box 3000, Bathurst, New Brunswick, E2A 3Z8, Canada. Abstract：Since 1994 Norandas Brunswick #12 Mine has complemented their MP250/Queens Full Waveform seismic systems with an ISS (Integrated Seismic System). Time histories of ISS source parameter information form
3、a component of the daily ground control decision-making. This paper discusses a methodology for microseismic hazard assessment, which filters ISS data using energy, apparent stress and seismic moment criteria to identify those events that are relevant for the assessment and decision-making process.
4、Seismic events are classified into four groups: (1) no or minor hazard; (2) seismically-triggered, gravity-driven hazards; (3) stress-adjustment-driven hazards resulting in bulking due to rock mass fracturing; and (4) deformation-driven hazards exploiting existing rock mass damage. Three case histor
5、ies from 19941996, for the 1000 Level South and the 850 Level at Brunswick Mine, are analyzed using this technique to calibrate and verify the proposed methodology.Key words: Rockbursts, hazard assessment, microseismicity, source parameters.Introduction Many research efforts have been directed towar
6、d eliminating, mitigating and minimizing rockburst hazard by improved mine design methods, design of energy absorbing or yielding rock support systems, and by better rockburst anticipation techniques (CAMIRO, 1997). Bursting conditions are usually not experienced early in a mines life; and thus litt
7、le effort may be placed on preventing burst-prone conditions during mine planning. If problems are encountered later in mine life, it is often not possible to alter the mining method or sequence and ground control engineers may be forced to live with seismicity, requiring procedures to identifypoten
8、tial rockburst hazards and to ensure adequate ground support to minimize risk. Norandas Brunswick no.12 Mine, located in Bathurst, NB, Canada, is a 9000 tonnes per day, zinc-lead-copper-silver operation. Brunswick has a history of microseismicity and has experienced rockburst-related damage to under
9、ground excavations. The mine has taken a pro-active approach to mitigating rockburst risk by complementing preventative mine design and ground support initiatives with a ground control program that provides 24-hour access to microseismic monitoring data. Brunswick employs three systems for seismic m
10、onitoring: Electrolab MP250 and Queens Full Waveform (FW) systems for event locations, and an Integrated Seismic System (ISS) for event locations and source parameter information. During the study period (19941996), normal daily microseismic activity averaged 400800 FW system triggers and 2040 ISS s
11、ystem triggers; however, these numbers could increase tenfold during periods of intense activity. Typically, 75% of these triggers are cultural noise, stemming from ore passes; fill raises as well as development and production blasts (HUDYMA, 1995). Daily data analyses, at the mine, consist of track
12、ing variations in event location clustering and occurrence frequency, and ISS energy index and cumulative apparent volume time histories analyses. These analyses combined with underground observations currently form the basis for workplace closure and re-opening decisions. Time histories (VAN ASWEGE
13、N and BUTLER, 1993) examine spatial and temporal source parameter variations to monitor rock mass behavior and to predict large magnitude seismic events (potential instabilities). Brunswick has successfully applied this approach, but felt it did not adequately capture or differentiate seismic hazard
14、s, largely because seismicity and seismically-induced damage are not restricted to large mangitude events (GIBOWICZ, 1990). HUDYMA (1995) wrote about seismic-ity at Brunswick, on an individual basis there is not a good correlation between the size of a seismic event magnitude and the level of damage
15、 that may be done. Accepting that current mining conditions and techniques cannot be changed to eliminate rockburst hazards, these hazards must be properly managed as part of a daily ground control decision-making process (e.g., temporary workplace closures and re-openings rehabilitation, support st
16、andard revisions). This paper presents a methodology to assess potential rockburst hazards using microseismic source parameters, which is designed to provide a simple but effective means for incorporating the most relevant source parameters into the daily monitoring and decisionmaking process. The ISS data and observed damage recorded at Brunswick Mine are used to calibrate and verify this methodology.1
