Wambo Coal AEMR 2011-2012 - Peabody Energy

8
2.2.3 KITCHEN WING
Results for the first floor of the Kitchen Wing, recorded on 17/2/2012, are scheduled in a similar manner in Table 2.
Event ident.
Channel
no.
Table 2 – Kitchen Wing first floor 17/2/2012
Orientation Max ‘a’, Max ‘v’, Max. ‘s’, mm
mm/s² mm/s
Dominant
frequency,
Hz
Kitchen Wing 1 N-S 845 13.1 0.31 10 10
2 E-W: 1 184 3.9 0.25 12 2.7
3 E-W: 2 220 3.8 0.13 10 2.6
Velocity
amplification
in building
Grounds N-S 1.31 11
E-W 1.47 12
V 0.84 NA
Reference to the spectrogram plots helps explain the different levels of amplification from what was experienced
in the house. In particular, the vibration of the chimney was quite low, indicating that resonance did not occur; the
north-south side wall did seem to get some resonance, as seen by the distinct pulses in the spectrogram, but other
frequencies were present as seen by the smearing. The most distinct movement was for the N-S direction, which is
likely to have been attributable to the movement in the end wall of building; the frequency correlating with what might
have been expected from the building as a whole would be up to 5 Hz.
3 CONCLUSIONS
3.1 Vibration vulnerability
Vibration monitoring during blast events in representative rooms in the New House and Kitchen Wing at Wambo
Homestead has shown that effects on the buildings are related to the frequencies in the blast wave. In particular, it was
observed that the buildings are most vulnerable to damage when the blast wave contains frequencies in the 10 Hz to
15 Hz range.
3.2 Scope for blast design adjustments to reduce vulnerability
Adjusting detonator delays and blast patterns has the potential for controlling the frequency distribution within the
blast wave. If, in the future, blasts critical to Wambo Homestead were be designed to have frequencies below 8 Hz
and greater than (say) 16 Hz, then the potential for damage, particularly to plaster ceilings, could be greatly reduced.
With suitable blast design this could allow substantially increased blast sizes without any greater risk of damage to the
buildings.
J.W. Jordan FIEAust CPEng
NPER Structural & Conservation Reg. No. 161488
April 2012
Wambo Homestead
Vibration vulnerability
April 2012