In all blasting operations, blasters
shall use one of the following methods to monitor or control the intensity of
motion in the ground at the nearest dwelling, house, school, church, commercial
or occupied building. These limits do not apply to property owned, leased or
contracted by the blaster's company or property on which the owner provides a
voluntary written waiver from these restrictions.
(1) Option 1 - Frequency Versus Particle
Velocity graph. A blasting operation shall have the option to use the graph
shown in Figure 6-10 to limit peak particle velocity based upon the frequency
of the blast vibration. Allowable vibrations fall below the limits indicated by
the central lines; non-allowable vibrationsNon-Allowable Vibrations lie above
the lines. Seismographs shall meet the following requirements:
(i) Monitoring instruments shall have a flat
frequency response between 2 and 250Hz for particle velocity.
(ii) The digitizing sampling rate for peak
particle measurements shall be at least 1,024 samples per second.
(iii) Seismographs shall be capable of
performing a self-test of velocity transducers and printed event records shall
indicate whether or not the sensor test was successful.
(iv) Monitoring instruments shall be capable
of recording particle velocities with intensities ranging from 0.02 to 5.0
inches per second.
(v) Monitoring
systems shall be calibrated by a service center approved by the manufacturer
within at least two years of the time of use. Certificates documenting date of
calibration, issued by the approved service center, shall be kept by the
user.
(vi) Monitoring systems shall
be capable of printing hard-copy reports showing the date and time of
monitoring, the maximum peak particle velocity (PPV) measurements, and plotted
PPV-time waveform plots.
(vii) For
all blasts with a scaled distance less than 100 ft/lb0.5, seismographs
monitoring motion shall be set to trigger at a level of 0.05 in/s.
The following equation shall be applied when calculating
the scaled distance.
Click to view
image
Where: Ds = Scaled distance
(ft/lb0.5)
D = Distance to the nearest structure (ft)
W = Maximum weight of explosive detonated within any 8
millisecond window (lb)
(viii) Vibration analysis results must be
presented in comparison with the RI 8507, adopted by United States Bureau of
Mines (USBM) and as shown in Figure 6-10.
(ix) If a valid vibration record showing
compliance with the MAPV limits shown in figure 6-10 is not available for
inspection, the maximum charge weight per delay (W) must conform to the scaled
distance limitations as prescribed in Option 2.
FIGURE 6-10
Click to view
image
Table: U.S. Bureau of Mines RI 8507,
2009
(2)
Option 2 Scaled Distance - when seismic monitoring is not performed, the
maximum weight of the explosive detonating within any 8-millisecond time period
shall not exceed the amount allowed by a calculation using the scaled distance
factors given in Scaled Distance column of Table 6-10.
The following equation shall be applied when utilizing the
scaled distance calculations to control blast-induced vibration.
Click to view
image
Where: Ds = Scaled distance
(ft/lb0.5)
D = Distance to the nearest structure (ft)
W = Weight of explosive detonated within any 8 millisecond
window (lb)
Example Maximum Charge Weight per Delay (W)
Calculation:
Given: Ds = 55 (ft/lb0.5)
D = 500 ft. therefore W = (500 /
55)2 = 82.6 lb
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Table 6-10
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Blasting Vibration and Air Over-Pressure
Standards
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Distance From Blast (Ft)
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Option 2 Scaled Distance
Factor
Units Are
Ft/Lb0.5
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0 to 300
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50
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301 to 5000
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55
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5001 and Greater
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65
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