EEG Practical Help

Question 1

PPV =

Answer 1

PPV = k(D/W^0.5)^B

Question 2

Specific charge =

Answer 2

Q/V kg/m^3

where
Q = total mass (kg) of explosives in a multi-hole blast
V = total in-situ rock volume (m^3) broken out

Question 3

Specific charge = Q/V

V = ?

Answer 3

V = S^2 x h

where
S = spacing and burden
h = height

Question 4

In a limestone quarry with dipping strata, a serious of blasts with Instantaneous Explosive Charge Weight, W, was monitored at various distances from the blast hole.

A log-log scale plot of the resulting data is shown to be remarkably linear with little scatter when plotted in this format.

(i) Briefly explain why the results do not seem realistic for a representative ground vibration survey in this limestone quarry.

Answer 4

Typically, results will be much more scattered and 90% or 95% confidence bands will be used.

Question 5

In a limestone quarry with dipping strata, a serious of blasts with Instantaneous Explosive Charge Weight, W, was monitored at various distances from the blast hole.

A log-log scale plot of the resulting data is shown to be remarkably linear with little scatter when plotted in this format.

How would you modify your analysis method given a more realistic set of results? Describe the main geological factors that can lead to inaccurate prediction from ground vibration surveys when applied to routine quarry production blasts.

Answer 5

In a dipping limestone sequence there will be anisotropic wave propagation so vibration amplitude is sensitive to direction.

The survey should address this with monitoring in the important max and min directions to pick up the geological structure effects.

Question 6

How would you draw 95% confidence limits onto a PPV vs SD plot by eye?

Answer 6

Drawn with same gradient;
95% upper limit only;
95% so would expect only 1 in 20 points to lie to the right;
This will give safer design.