Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators

By
Nick Lewis, Vulcan Materials Company
Paulo Pereira, ORICA USA, Inc.

Abstract

The Vulcan McCook quarry has been in operation for about 100 years. It is located about
17 miles from downtown Chicago and is surrounded by both industrial and private
structures. Recent issues have forced the quarry to blast very close to structures and this
will be necessary years into the future. This paper discusses the implementation of
electronic detonators to McCook. It also discusses the advantages and savings that the
Program has achieved

Introduction

2001 production at the Vulcan Materials McCook Quarry was 10 million tons.
Production levels are projected to be in the 8 million ton level for the next 3-5 years.
Daily blasting requirements are about 45,000 tons. Recently, ground control problems in
active quarrying areas forced the major reserves of the quarry to be temporarily
abandoned for evaluation. This has forced McCook to extract reserves that are closer to
houses and industrial sites. Currently, about 50% of blasts are 500-700 feet from
structures, 25% are 400-500 feet and 25% are greater than 700 feet. It is Vulcan policy
not to exceed 0.5 in / sec peak particle velocity and 130 db peak overpressure. 10
continuous seismographs surround the quarry and are monitored by independent
consultants for compliance.

Between 1998 and 2001, McCook began mining areas that were closer to structures.
Seismograph studies identified “hot zone” areas where ground vibration was higher than
expected. Using regression analysis, it was decided that a conservative scale distance of
75 would be used to design shots in all areas. This criterion was in effect for 3 years and
success was achieved in that blasts met the limits set forth by Vulcan. The disadvantage
was the required additional drilling, loading time, cost and the lower tonnage per shot
detonated. It was common to shoot 4 shots per day, 6 days per week and to drill 24 hours
per day, 7 days per week. Even then it was common for the quarry to be out of shot
material.

In 2001, a new drill and blast program was implemented at McCook. The major focus
was to increase the tonnage per shot while staying within the requirements for ground
vibration and air overpressure. Evaluations began immediately on two fronts.

The first was to test bulk loading of blastholes, particularly pumping a 70% Emulsion /
30% ANFO sensitized blend. Most holes are wet and require either de-watering or
pumping for bulk loading and the past program used bagged explosives. This was done
primarily to meet the very low pounds per delay requirement associated with a scale

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 1 of 14
distance of 75. This is especially true at distances of 500 feet and lower. If bulk loading
was feasible, drilling patterns could be expanded significantly thus increasing the yield
per shot. However, if more pounds were loaded, then the scale distances would be less
than 75.

This lead to the second front, the testing and implementation of electronic detonators. It
was suspected that the original regression study concluded such a high scale distance due
to cap-scatter in the pyrotechnic delays that were used during the study. The question was
would accurate timing allow a lower scale distance to be shot and still meet the vibration
requirement? Through testing, it was determined that a Scaled Distance of 38 was
feasible as long as all other fundamental variables were in order (burden, spacing, actual
lbs loaded, etc.). This lower scale distance has allowed the drilling and blasting
productivity to expand dramatically while maintaining required powder factors.

Methodology

The D&B program at Vulcan’s McCook Quarry has embarked on a continuous

improvement process to increase the quarry’s productivity and lower its operating cost.
The main operating constraint at the quarry is controlling ground vibration due to the
proximity to structures all around the quarry. Hence, all optimization efforts were
carefully chosen as to not exceed the ground vibration limits both imposed by the State of
Illinois and by Vulcan Materials. The methodology followed to improve quarry
operations efficiency through drilling and blasting included but was not limited to:

1) Comprehensive seismic study

2) Use of handheld GPS receivers to establish a ground vibration scaling law for the
quarry based on different blast zones
3) Use of different timing
4) Use of electronic detonators
5) Reduction of fines

Comprehensive Seismic Study

Back in 1999, Vibratech performed a comprehensive seismic survey around the quarry
and came up with different blasting response zones. With this information the D&B
program could be customized to stay in compliance. In addition, through signature holes
the work identified preferential delay times, which could be used to generate a certain,
prescribed frequency content in the seismic energy.

This work also, produced scaling laws with which the quarry could have a reasonable
idea of the ground vibration Peak Particle Velocity everywhere in the quarry. However,
these scaling laws do not allow for the prediction of frequency content in the seismic
energy. As such, several distinct seismic zones were defined including a few hot spots.

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These hot spots constitute a daily challenge to the D&B program with a trailer park being
one in particular. Frequencies at this site are lower than at other points nearby at the same
distance, and everything else being equal, ground vibration frequencies are much higher
while particle velocities are quite comparable.

In addition, Vibratech, based on the comprehensive seismic survey done all around the
quarry specified delay times to be used between holes and between rows in shots to
produce a certain frequency. The seismic survey also conservatively recommended a
Scaled Distance of 75 to control ground vibration in all quarry.

The quarry has two distinct rock types namely A and B. Both types are limestone but
have different chemical characteristics and quality. The different chemistries also
influence the blastability of both rocks. Usually the B rock is more friable than the A
rock. In addition, the B Rock blasts usually happen at lower elevations in the quarry and
further away from structures around the quarry than the blasts conducted in the A rock.
The latter blasts are usually only a few hundred feet from the closest structure and
seismographs.

The quarry is subject to two peak particle velocity limits. One is mandated by the state of
Illinois and is 1.0 inch per second, and the other is self-imposed by the Vulcan Materials
the Vulcan Materials Co. is 0.5 inches / second.

Use of Global Positioning Receivers to Establish Scaling Law

It was felt that to better understand the recommended scaling law accurate location of
every shot in relation to the nearest seismograph was imperative. As such, the quarry
acquired portable Global Positioning System receivers. These receivers with distance and
location accuracy of +/- 10 feet helped determine the distance between shot and
seismographs without the need for surveying.

Henceforth, scaling laws were calculated for different points in the quarry. As it turned
out the pre-established scaled distance of 75 had to be reevaluated. The different scaled
distances also impacted the quarry’s productivity and its operating costs including but not
limited to the drilling and blasting costs.

Use of Different Timing with Pyrotechnic Delays

The Vibramap conducted by Vibratech around the quarry with more than 140 receivers
installed was used to select delay times for the pyrotechnic delays in the quarry. To
support the Vibramap, the quarry also conducted several single-hole blasts to generate
signature vibration traces in several positions at the quarry. The power spectra from these
signature holes were used to recommend delay times to impart the lowest possible ground
vibration amplitudes around the quarry.

Use of Electronic Detonators

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Early in 2002, the quarry decided to test electronic detonators as a means of controlling
ground vibration, particularly in critical areas from a vibration control and quarry
production standpoints. Incidentally, one of these critical areas was earmarked in 2002 to
produce about 25% of all the rock in the quarry and about 45% of the premium quality
rock.

In these critical areas, in order to keep ground vibration under control, the quarrying plan
would have to change causing an increase in operating costs. It was expected that
electronic detonators would allow the quarry to take some more radical steps in the
blasting program that would reduce operating costs in these critical areas

Electronic detonators available in the market were analyzed and the quarry selected
ORICA’s i-konTM Digital Energy Control given its flexible operating features that
rendered it easier and safer to use.

Reduction of Fines

Fine or base material is the single most worrisome product of any aggregate operation, as
there usually is very little market demand for fine material and when there is market
demand the price usually paid for it does not generate adequate profit margins.

Historically, the quarry has generated fines as an unavoidable by-product of the quarrying
process. In early 2002, quarry management decided to better understand the problem and
in order to do that a belt scale was installed after the primary crusher. It allowed the
quarry to quantify the amount of fine or base material produced after the primary
crushing system. This reduction of fines process has only recently started and will be
discussed in another paper.

Discussion of the Results

Introduction

Vulcan has a self-imposed 0.5 in/sec PPV limit on all three components but no formal
limits on frequency. Compliance implies economic considerations, constant attention on
blasting designs, and the ability to predict the behavior of the ground vibration for every
location in the quarry. An electronic detonator based ground vibration prediction system
will greatly contribute to the maximization of the quarry’s productivity through
incremental improvements of the drilling and blasting program. The current work,
undertaken since last year, is the first step towards building such a system. The results
presented here come from 453 blasts between June 2001 and June 2002 in A-rock type. It
is felt that these results can be expanded to other parts of the quarry in a way that overall
operating productivity in the operation as a hole can be enhanced.

Scaled Distance Evolution

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The seismic map drawn by Vibratech established a universal scaled distance of 75 to
ensure compliance of the 0.5 in/s everywhere in the quarry. However, it was felt that this
scaled distance was too conservative when broadly applied to the whole quarry. The
initial idea then was to use a handheld Global Positioning System receiver to accurately
establish the distances from the blasts to seismographs. Coupled with that, the accurate
determination of the hole explosive loading weight through the new bulk-truck load
measurement system allowed for an accurate determination of the scaled distance.

The recorded peak ground vibration indicated that the scaled distance could be locally
tailored without exceeding Vulcan’s internal limit. After several attempts, it was
determined that the scaled distance could be significantly lowered all around the quarry
as shown in Figure 1.

Figure 1 – Scaled Distance Evolution at the McCook Quarry

80
70
60
50
40
30
20
10
0
< April 2001 > April 2001 and > December 2001 > June2002
< December 2001 and <June 2002

The drilling and blasting program at the McCook quarry employed, up to December
2001, non-electric initiating systems that, as is commonly known, manifest delay time
scatter. This delay time scatter potentially can cause complex vibration patterns that the
industry has learned to coexist with over the years but that effects operating performance.
At the quarry, after analyzing non-electric initiation generated ground vibration patterns,
it was felt that the scaled distance could be reduced. However, it was unknown by how
much the scaled distance could it be reduced without being disruptive to neighbors or to
the quarry operating productivity.

To answer this question the quarry drilling and blasting management decided to introduce
electronic detonators in the quarry particularly in critical areas such as the South – South
West zone of the quarry. Utilizing the same blasting parameters as before and modifying
timing configurations in the existing blasthole decking structure the quarry achieved

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 5 of 14
excellent levels of ground vibration control that could not have been achieved with non-
electrics.

As a result, an additional reduction in the scaled distance was produced this time from 50
to 36 as expressed in the Figure 1 starting in January 2002. Currently, the drilling and
blasting department at Vulcan is experimenting with other blasting design configurations
to further enhance quarry productivity based on the scaled distance of 36.

Drilling and Blasting Cost Evolution

As mentioned above, the reduction in scaled distance has had economic implications in
the drilling and blasting costs. When shooting scaled distances of 75 the quarry used
bagged emulsion and ANFO explosives, dewatering holes when necessary. In addition,
patterns were relatively small and used 4.5-inch holes with a ratio of 2.22 burden-to-hole
diameter. The blasting program was then modified to load bulk explosives instead of
bagged explosives. The same hole diameter was employed and the burden to hole
diameter ratio was increased to 2.88, resulting in an increase to the blast pattern burden of
almost 30. This and other modifications, as shown in Figure 2, effectively reduced the
overall D&B cost by 34% by going from a scaled distance of 75 to 50.

Figure 2 – Drilling and Blasting Cost Evolution as a Function of Scaled Distance

1.2
1
1
0.765
0.8 0.656
D&B Cost
0.6
Ratio
0.4
0.2
0
SD 75 (Before SD 50 (non- SD 36 (Electronics)
April 2001- non- electrics)
electrics)
Scaled Distance

The introduction of bulk explosives also rendered positive results:

a) Reduced load cycle times

b) Eliminated the need for dewatering holes
c) Eliminated the need for bagged explosives storage

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 6 of 14
 d) Reduced labor costs

Electronic detonators were introduced in the beginning of 2002 at the South-Southwest

area of the quarry. In this area, it was decided that instead of shooting two 50-foot high
benches using non-electrics the quarry would shoot one single 100-foot high bench. This
would not only improve drilling and blasting operating productivity but also hauling
productivity. Hauling distances would increase by about 30% if the two 50-foot benches
were the only choice.

In early 2002, quarrying started using the single 100-foot bench in the South-Southwest
area. To date approximately 2,000,000 tons have been mined from that area with very
successful vibration control.

The need for the electronic detonators in that area increased the D&B cost in relation to
the scaled distance of 50 by about 16.7% on a per ton basis as also shown in Figure 2.
This cost differential however, was more than offset by other operating improvements.

Firstly, the 100-foot bench determined a shorter hauling distance that enabled a reduction
in hauling cost of about 30% compared to the double 50-foot bench situation. Secondly,
the elimination of one bench also seemed to improve the efficiency of the drilling and
blasting operations through increased utilization. Thirdly, the elimination of one
stemming area also seemed to improve productivity at the primary crusher.

The gross and net value due to the aforementioned electronic detonator enabled operating
improvements were estimated to respectively 41% and 24% of the D&B cost at the
Scaled Distance of 50 as shown in Figure 3.

Figure 3 – Net Operating Value due to Electronic Detonators

Electronic Detonator Enabled Net Value

50%
% of the D&B Costs

40%
30%
20%
10%
0%
1

Cost Differential Electronic - Non-electrics

Total Estimated Gross Savings
Net Value

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 7 of 14
Resulting Ground Vibration from SD = 50 to SD =36 in A-Rock Type

Peak Particle Velocity

In the critical South-Southwest area of the quarry, electronic detonators were extensively
used in the A-type rock to compare their operating performance against non-electrics.
The resulting peak particle velocities were in general higher for the electronic detonators.
This is actually expected given the fact that in order to achieve the scaled distance of 36
not only the pounds per delay were increased by 45% but also the distance between shots
and seismographs was shortened by 15%. Figure 4 depicts the measured average PPV’s.
The difference between the mean PPV’s is significant at the 96% confidence interval
assuming a normal distribution.

Figure 4 – Peak Particle Velocity between Electronic and Non-electric Detonators

0.4
0.35
0.3
0.25 All Non-electric
in/s

0.2 All Electronic

0.15
0.1
0.05
0
PPV L PPV T PPV V
Peak Particle Velocity

Tests with non-electric initiation revealed that due to cap scatter this type of initiation
system was just too unpredictable to be used in such geometry as far as ground vibration
control was concerned.

Still, another aspect that was worthwhile evaluating was the variability of PPV’s as
described by the standard deviation of the measurements. Figure 5 depicts the variability
comparison between non-electrics and electronics.

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 8 of 14
 Figure 5 – PPV Variability between Electronic and Non-Electric Detonators
Peak Particle Velocity Varaibility
Non-electric vs Electronics

as % of Average PPV
Standard Deviation
80%
60%
40%
20%
0%
PPV L PPV T PPV V
Components
St. Dev % of Average (Non-electric)
Std Dev % of Average (Electronics)

Figure 5 shows that electronic detonators, everything else being equal, should produce
more predictable seismic signatures from blast-to-blast due to the absence of randomness
in the delay timing. Small random variations in cap scatter may greatly alter the order of
blasthole firing in a blast. This in turn may affect rock movement and fragmentation. By
using accurate timing it is possible to further enhance blasting performance to a higher
degree than what is achievable today with non-electric detonators. Current initiatives at
the McCook Quarry between Vulcan Materials and ORICA USA Inc. aim at taking
advantage of this capability.

The ratio of the variances between the Peak Particle Velocity generated by electronic and
non-electric detonators was also evaluated. This ratio was in general less than one for two
of the three components of the ground vibration at the 98% confidence level. This is
remarkable, given the significantly lower average scaled distance used in the shots fired
with electronic detonator.

Frequency

The frequency content of the ground vibration was also evaluated at the peak particle
velocity values. One difficulty was that a power spectral analysis could not be performed
due to absence of data. It would be helpful to understand the energy content in the 4 – 20
Hz frequency band of structural damage interest. Figure 6 depicts the frequency values at
the Peak Particle Velocity values.

Figure 6 – Frequency Comparison between Electronic and Non-Electric Detonators

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 9 of 14
 45
40
35
30
Hz 25 All Non-electric
20 All Electronics
15
10
5
0
Freq L Freq T Freq V
Frequency

There is hardly any real difference in the average frequencies for the three components
exception maybe for the Vertical component. Figure 7 presents the variability and the
results also do not show significant differences in variability.
Figure 7 – Frequency Variability Comparison Electronic and Non-electric Detonators
Frequency Variability at the PPV

60%
% of Average Frequency at the

50%

40%
Peak

30%

20%

10%

0%
Freq L Freq T Freq V
Frequency Component

St. Dev % of Average (Non-electric) Std Dev % of Average (Electronics)

Summary of Results

Table 1 presents a summary of the results following the application of electronic

detonators.

Table 1 – Summary of Average Results for all shots analyzed

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 10 of 14
 Average Non electric Electronic Electronic vs
Non-electric
PPV (in/s) 0.26 0.32 +19%
Frequency (Hz) 30.6 28.2 -7.2%
Scaled Distance 50 36 -28%
Av.Tons / shot 5.5” holes 24,064 35,895 +49%
Holes / shot 28.5 27.8 -2.5%
Av. Bench height 5.5” holes 48.0 ft 69.6 ft +45%

The improvement in D&B productivity is described in Figure 11 as the increase in tons /

hole and Figure 12 as the increase in Primary Crusher Productivity.

Figure 11 – Tons per hole comparison electronics vs non-electrics

Tons / hole

1200 1075
1000
748
Tons / hole

800

600
400

200
0
Non-electric ikon
Initiation system

The Primary Crusher Productivity increase is primarily, the authors think, due to (1)
eliminating one stemming zone after the introduction of the 100-foot bench in the SSW
area of the McCook Quarry; (2) consequent increase in the average shot size with
electronic detonators; and (3) significantly increasing the number of pounds per delay by
using electronic detonators.

Figure 12 – Primary Crusher Productivity vs Shot Size

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 11 of 14
 2,700

Primary Crusher Throughput

2,600

2,500
(tons/hr)
2,400

2,300

2,200

2,100

2,000
15,000 17,000 19,000 21,000 23,000 25,000 27,000 29,000
A Rock - Shot Size (tons)
R2 = 0.5901

Non-electric initiation was tested with the same blasting geometry in the 100-foot bench.
See table 2 for blasting parameters for non-electric and electronic shots used on the > 90-
foot bench. The scaled distance used was approximately the same as in the shots with
electronic detonators.

Table 2 – Predominant Blast Parameters for Bench Height > 90’, HD = 5.5”

Factor Unit Non-Electric Electronic

Burden Feet 17.3 17.0
Spacing Feet 17.3 17.3
Tons / shot | Holes / shot Tons | Holes 35,800 | 17 55,800 | 25
Bench Height Feet 95 98
Scaled Distance NA 52 45

The resulting Peak Particle Velocities at Location 1 are depicted in Figure 13 and the
variability in the Peak Particle Velocity at that same location is depicted in Figure 14.

Figure 13 – Comparison PPV between Electronic and Non-Electric Detonators

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2003G Volume 2 - Operating Improvements at Vulcan Materials McCook Quarry using Electronic Detonators 12 of 14
 Peak Particle Velocity at Location 1, Bench Height >
90', HD = 5.5"
0.4

Particle Velocity (in / s)

0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
PPV L PPV T PPV V

Non-electric Electronic

Figure 14 – Variability for PPV between Electronic and Non-electric Detonators

PPV Variability Bench Height > 90' at Location 1,

HD = 5.5"
Standard Deviation as a %

30%
25%
of Average

20%
15%
10%
5%
0%
PPV L PPV T PPV V

Non-electric Electronic

The generally higher particle velocities, variability and lower productivity per shot with
non-electric detonators motivated the decision to use only electronic detonators in the
100-foot bench.

Conclusions

The Drilling and Blasting program at Vulcan Materials McCook Quarry has evolved
considerably from historical practices where bagged explosives and very conservative
scaled distances were used. With the introduction of bulk explosives and simple GPS
technology significant further improvement has been achieved in the form of:

• Reduced drilling and blasting costs by reducing the number of shots per year
• Eliminated the need for dewatering holes
• Reduced the need for explosives storage
• Reduced scaled distance all around the quarry from 75 to 50

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Operating constraints related to ground vibration control and cost reduction in vibration
sensitive areas motivated the quarry to introduce electronic detonators in early 2002. As a
result scaled distances were further reduced from 50 to 36. This allowed for increasing
the shot sizes in the sensitive area particularly doubling the bench height in the SSW
corner of the quarry.

The 28% reduction in scaled distance, not surprisingly, increased Peak Particle Velocities
although the increase was modest. In addition, the variability of the Peak Particle
Velocity was reduced after electronic detonators were introduced. Particularly in the 100-
foot bench, the use of non-electrics was discontinued after a few trials. The resulting
greater variability in the peak particle velocities in these tests generated values that were
close to Vulcan’s self-imposed limit. The frequencies analyzed were not as clearly
influenced by electronic detonators as were the peak particle velocities and more work
needs to be done in this area.

The operating cost results showed that despite the increased cost of electronic detonators
the overall net value created by using electronic detonators surpassed that expense by
24% of the existing D&B cost. This level of value came from:

• Reduction of in hauling unit costs with the introduction of the 100-foot bench.
• Elimination of one stemming zone in the single 100-foot bench that allowed for
reduced drilling and blasting operating costs.
• Increase in Primary Crusher Productivity in the A-Rock Type with increased shot
size and elimination of one stemming zone after joining two 50-foot benches in
one single 100-foot bench.

Finally, it is clear that (1) electronic detonators enabled further operating improvement at
the McCook Quarry; and (2) their increased cost was more than offset by said operating
improvements. They have become a stepping-stone for Vulcan Materials Co. and ORICA
to further improve operating performance at the McCook Quarry.

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