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CONTRACT no 13RE2-CT92-0127

BLASTING CONTROL FOR UNDERGROUND MINING

WITH SPECIAL REFERENCE TO IN-SITU ..
M E . A S U R E M E N T S AND TESTS . . . .,.
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~UBL&ABLE’ SYNTiESIS liiPOii+ .. . ..’. ., .;,,. . . .
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FROM 01.11.1992
,. TO 31.07.1995
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PROJECT REPORT No 8

ARMINES/CGES Coordinator
POLITECNICO DI TOIUNO Partner
BAUXITES PARNASSE Partner
NITROBICKFORD . Partner
MONTANUNIVERSITY LEOBEN Paitner
VOEST ALPINE ERZBERG Major Subcontractor

:., ,,
i
1. OBJECTIVES OF THE PROJECT

The improvement of an existing blast supposes two different cycling steps : first the
diagnosys of the problem, then the application of a therapy in order to solve the problem.

If the therapy (or blasting planning) uses more or less the same principles since
Langefors deveIoped his theorj, the diagnosys is still a highl y time-consuming process which
does not always provide all the necessary inforniation for a correct therapy.

The current project, under the name of Blasting Control, clearly addresses the first
step of the kycle : the diagnosys. Its industrial objectives are to :

more precisely control the bksting operation, by the use of an updated methodology,
using the recent improvement in terms, of acquisition devices and explosive
manufacture,

indirectly, make available control tools for the main entities invoIved in b~astin~
(fracturation, explosive energy, fragmentation, vibrations, and side effects). -

As a result, the application to any ‘underground mine of the Blasting Control

methodology developed in the project should provide blasting experts (mining engineers,
academic professors or technical services) with the relevant data for the improvement of
biasting in this mine, in a time compatible with production constraints.

,.
2. CWMN’IZAT~(3N. OJ?:i’EEE PROJECT. ,,. .

In order to reach the objectives of the research, the project has been organized in
three main phases (figure 1) :
1,

Analysis of the blasting practicai experience (without any specific control) in a

,0 mine in production (Biiuxites Parnasse).

The idea was to show that it was not possible to propose a correct therapy to the mine
simply with a manual observation, that is to say that there was a real need for the
current project !

Development of the Blasting Control methodology

This second phase was based upon measurement of M possible information before,
during, and after blasting. It concerned the rock to be bIasted, the explosives used,
the blasting process itself as well as the results of the blast Wd its environmental
impact. The phase more precisely proceeded through the three foIlowing steps.:

Development of control devices, in a fully dedicated test mine (Erzberg test

site).

I Contract 13RE2.CT92.0127 Pro.iect te~ort n“ 8

Blasting Control 1 “ 01.11 .lj92 - 3~.07.1995
 ., .
I This step included the choice and adaptation of the control devices, the
material preparation of the test site and the organization of the tests, the
definition of a “working blast”, and [he control devices tests, calibration and
validation.

It provided the instrumentation, as well as the acquisition methodology, usab[e

I jn any underground mine.

ExpIcisives and detonators properties measurement, in a dedicated chemical

laboratory (Nitro-13ickford pkmt)
..
~ The different explosives and detonators used in the project have been amdyzed
for future comparison and calibration.

1 I
Interpretation of the measurements

In order to provide the experts in charge of the therapy

--
work with a-usable
o information, it has been necessary to an~yze the measurements o~tputtti from
the devices. ‘The geometrical data have thus been processed, and several
analysis and correlation have been made on the other measurements, in order
I
to extract significant parameters on the controkd blast behavior.

This second phase answered the key questions of how can the blast be ccmtrokd,
and what type of information can be extracted from the measurements.
..
- Validation ok the blasting control methodology in a mine in prod~ction (Bauxites
Parnasse) “’.

This last phase first concentrated on the validation of the acquisition with the working
conditions of a mine in production. This also has provided data, used by an expert
group in order to propose a new blasting scheme (therapy). Finally, the new blasting
scheme has been tested and validated in the mine in production.

Q This third phase of the research showed the feasibility of fuI1y controlled b[asts in
a mine in production (diagnosys), as well as the efficiency of the measurements z
for a real improvement of the blast (therapy).

In order to realize such a research program, the project consortium was constituted
of a mine in production as an end-user (Bauxites Parnasse), of a partner able to provide a
fully dedicated test site (Leoben), of an industrial company specialized in explosives and
detonators manufacturing (Nitro-Bickford), and of three complementary academic parmers
(.4rmines, Politecnico Torino and Leoben). For the performance of the mining, work i! the
test site, Voest Alpine Erzberg GesmbH was gained as a major subcontractor.

Contract BRE2. CT92.0127 Project report n“ 8

Blasting Control 2 01.11.1992-31.07.1995
 r ANALYSIS OF BLASTING PRACTICAL EXPERIENCE .--. > Limit of control
without devices

II DEVELOPMENT OF BLASTING CONTROL NIETKOI)OLOGY

II. 1 Control devices development

. ,clevices adaptation
. test organization .---> How to control
. working blast with devices
. device tests

11.2 Explosives and detonators measurements

H.3 Interpretation of measurements

. geometrical data processing ---- > Wh,at to expect

. analysis and correlations from the control

.
m VALIDA,TION OF BLASTING CONTROL mTHbDOLOGY

111.1 Acquisition validation ----> F e a s i b i l i t y o f

control in working
conditions

111.2 Exarnple of therapy ----> Example o f

Improvement
Improved b l a s t i n g s c h e m e following the mntrol
. tests of the new scheme

Figure 1 : Organization of the projdct

Contract J3RE2.CT92.0127 Project report n“ 8

Blasting Control 3 01.11.1992-31.07.1995
-.

PHASE 1: ANALYSiS OF BLASTING PRACTICAL EXPERIENCE

The first phase of the project has been dedicated to the analysis of the practical
experience of blasting in the Bauxites Pamasse mine.

The work logically started with thedefinition ofa blastingagencfa, supposed to be

filkdby mine foremen for each observed bIast, including the followingitems :

GeneraI data (date, time, working area, drift, blast)

Shape of the drift before blasting (actual profile, face situation, distances to reference
point)
Geological situation (rock type, disconthmities)
Blasting geometry (actuaI cut, drilling pattern, charging, delay)
9 BIasting results (pile profile, grain size distribution, advance profile after bksting)
Scaling (length, volumes)
Shape of the drift after blasting (profile, face situation)

The next step addressed. the observation itself which runned during the first 6 mcmths
of the project on 43 blasts referring to 6 different drifts in limestone and in bauxite.

Finally, a detailed analysis (statistical and qualitative) concentrated on the 43 observed

bIasts, The statistical analysis of the resuIts showed that, : .’ .”
\
Simple correlations between obsemed parameters was not possible.’” ,
\
I There were many deviations between actual and planned rounds, both in bauxite and
in limestone. They mainly concern the cut pattern and the charging.

The results, in terms of advance and profile shape, were fm from the expectations.
e The qualitative analysis of the results showed that :

The key point of the blasting success is the cut. The best results (regarding over
breaking and advance) are ob~ined when the actually drilled cut is different from the
planned one.

The drilling side seemed to be only indirectly affected by explosives, which raised the
problem of drilling accuracy and of explosives behavior.

The resuIt of these anaIysis, somehow quite poor and uncertain, was a good
illustration of the limit of classical diagnosys. It showed that not enough information was
available to propose quickIy a correct and precise therapy to the mine. it lead to the fact that
there was a cIear need for a better control of the bIasting process.

Con&act BRE2.CT92.0127 Project report n“ S

Blasting Control 4 01.11.1992- 3i.07.199S
 l“” ‘
PHASE 11: DEVELOPMENT OF BLASTING CONTROL METHODOLOGY

The main global entities involved in the Blasting process can be expressed in the
following list :

the rock to be blasted (hardness, microfissuration, natural fracturation, behavior

during drilling, holes position and deviation, profiles),’
the explosives and detonators used,
the blasting itself (energy used, ignition efficiency),
the blasting results (grain size distribution, profiles, advance, side walls weakening),
the environmental constraints (vibrations, noise and air, gas).

For each element of the previous list, some fundamental parameters can be
measured in order to provide u~ful information for the control of blasting. This is the precise
objective of the blasting control methodology “developed in the project.
..

e In order to reach such an objective, the idea has been to adapt arid test control devices
able to provide the searched parameters in a realistic time (compatible with production
constraints) and at a reasonable cost (only existing low cost equipments have been used).

I The phase has been organized around the control devices development (II. 1) realiz~
in the Erzberg test site, the explosives and detonators rn&surements (X1.2) made in the
NitroBickford plant, and the interpretation of measurem~nts (H.3).

Ill .CONTROL DEVICiiS D E V E L O P W E N T ,, ~~~ . ,

I This part of ‘the work supposed to choose and adapt the devices, to prepare the test
site, to organize the tests, to find a working reference blast, and finally to validate the
devices. Main results are presented in the following.

The devices or measurement methods, chosen for test, are the following :

@ Hardness : Point Load Testing, Schmidts Rebound Hammer

Microfissuration : Seismic wave velocity and R & D measurements
Natural fracturation : In-hole Endoscope
Behavior during drilling : Instrumented Drilling Jumbo
~ Holes !30 sition and deviation : Theodolite
Profiles : Theodolite
Enersw used : Moved to vibra[io~s measurement
Vibratioris : Seismographs
Grain size distribution : Image Analysis c/o CCD-camera
Noise and airblast : Dedicated devices
@ : Large scak measuring device

Contract BRE2.CT92.0127 Project report n“ 8

Blasting Control 5 ‘ OL1l 1992-31 07 1995
 A fully equipped underground laboratory has then been realized in the Erzberg test
site, incIuding computer office, access galleries, wire and cable connections, ventilation,
etc . . . The efficiency of this laboratory has been tested through 4 monitored blasts. From
these tests, it has been possible to define precisely how to organize the future work in
Erzberg.

Concerning the data acquisition, a biasting agenda, simikr to the one made for
Bauxites Parnasse, but including the devices, has been developed for Erzberg.

The following test period, aimed at finding a working blast, allowing control devices
monitoring -without secondary blasting to correct its failure. This step of the work has been
carried out during 11 blasts made in two drifts. The objective of the 7 first blasts was to keep
every blasting parameter as constant as possible in order to evaluate the standard deviations
of the measured parameters. This helped to choose the range of planned variations for the
further tests as well as to judge about the significance of different blasting results. Once the
standard working blast has been found, 4 more blasts have been made to standardize the
decomposed blasts process.

The last set of tests in Erzberg has been devoted to the blasting control itself. The
objective was to have the control devices working and providing as many useful data as
possible. Nearly 30 blasts (full,, decomposed, and single shot) were made in two drifts. Full
blasts aimed at the full rnoni~oring testing. Decomposed blasts, made in three steps, tried to
isolate seismic information from the cut, the production zone, and the contour zone. Single
shots controkd the drilling precision, the burden distances and the vibration records. The
main results of the tests are given in the following.
.’.’
Rock’ hardness devices : Tests carried out on rock “samples showed a quite good
correlation between uniaxial compressive strength and the point load index determined
radially for the limestone area. Moreover, it was shown that [he various rock
parameters measured correlate quite well on a global scale (10 m) and may vary very
much on a blast per blast scale.

Endoscope (natural fracturation ) : The endoscope was used to detect big faults (and
● particularly to see if they connect bordering holes). The results were satisfactory and
the image strip could be recons[ructesi from the recordings. F$evertheless, the
measur~ment was quite long and it was clear that a stronger equipment is needed to
achieve the complete objectives.

DrilIin~ iumbo (behavior during drillin~ : The close monitoring of drilling

parameters for purpose of the prediction of rock and rock mass parameters gave the
following results :

From monitoring of the drill speed the localization of major faults and open
cracks in the ground is possible.

The presence of inhomogeneities in the rock (schist pkmes, etc... ) which are
closed cannot be localized on the spot. Heavy jointing results in a usualiy

Contract BRE2. CT92.0127 Project report no 8

Blasting Control 6“ 01.11.1992-31.07.1995
 increased drill speed.

The prediction of changing rock properties from monitoring of drilling

parameters is possible on a global point of view.

Theodolite (holes ~osition and deviation, ~rofiles) : The device worked as pkmned,
but was very time consuming.

Seismo~raphs (vibrations} : The positioning of the devices is of a great importance.

It will have to be tested in any new mine to be controlled. Moreuver, a filtering
process of the signals is necessary before interpretation. ‘

Image analysis (grain size distribution) : With the adaptation for fines elimination on
the image, the system worked correctly.

Other devices (for noise and airblast measurements, for gas detection) have been
tested for proper environmental controL Nevertheless, it is not pianned to bring them in
● Greece.
I At the end of this control devices development part of the project, the initial key
question (how to control the blasting process with devices) is considered to be answered.

IL2 EXPLOSIVES AND DETONATORS MEASUREMENTS

The energy and the detonation speed of each type of explosives had to be measured
ifi order to evaluate their actual efficiency, and to move from E~berg blasts (Austrian
explosives) to Bauxites Parnasie blasts (Greek explosives).

The measurements have been realized in the Saint-Martin de Crau plant of Nitro-
Bickford, with standardized procedures. Their principle is to blast under water and to
measure the maximum pressure of the chock wave (providing the chock energy Ec), and the
length of the bubble pulse first “pseudo-period” (providing the gas energy Eg). The totaI
@ energy Et available for the blast is given by the chock and gas energies sum.

Concerning the explosives used in the Erzberg test site, 25 kg samples of Gelatine
Donarit 1, Gelatine Donarit 2E, Lambrex 1 and Lambrex 2 have been required from Nobei-
Vienna and imported in France.

Concerning the explosives used in the Bauxit& Parnasse mine, due to very strong
importation / exportation and transportation problems, chemical formulas of pulverdent
dynamite NAD 1 and crashed D7, of gum dynamite Robex 1, and of gum dynamite Hand
machine 3, have been required from Elviemek. 25kg of each explosives have then been
manufactured from the formulas specifically for the tests.

Contract BRE2.CT92.0 127 Project report no 8

Blasting ControI 7 01.11.1992-31.07.1995
 Concerning the detonators, the Czech detonators used in Greece and the Schaffler
detonators used in Austria were nearly identical to the Nitro-Bickforcl ones (Davey), in terms
of PETN loading and of energy. For that reason, tests have been performed with Davey
standard electrical detonators with 0,2 g of lead nitrite and 0,6 g of PETN under 400 bars
compression.

\
11.3 INTERPRETATION OF MEASUREMENTS

The first step of the interpretation has been the realization of a database in order to
store the results (from observation and measurements) and allow geometrical representations
and calculations. This database, realized with Access, ExceI, and Sumac . softwares rxovides
the main following outputs :

calculation of the advance

calculation of dip and azimuth of each borehole
extraction of the real drilled length
● shape of the face
drillhoIe position on the face
drillhole p o s i t i o n i n 3 D
drilled volume of cut, production, and contour zones
position and amount of explosives in each hole
blasted volume
profiles
for all data, comparison between actual and planned values ‘

Examples of vie;;ng capabilities are given on” figures 2 and 3.

The next step was to evaluate the significance of the data obtained from the chosen
control devices, that is to say to know if:

the measurements reflect the actual physical parameters (which supposes an individual ‘
analysis of each device and of their links to real parameters involved in the blasting
process),

the provided information is useful to the blasting improvement (which supposes a

-
glolxd analysis of the devices capability to explain a g;ven biasting result). ”

The Erzberg tests and the following analysis period allowed to define more precisely
the potentialities and the limitations of some of the devices. Although this analysis work
would have needed much more time, the results are very promising. They were :

The complete geometrical survey of the blasting process allowed an efficient control
of the blasted volume related to each single hole.

Contract BRE2.CT92.0127 Project report n“ 8

Blasting Control 8 01.11.1992- 3i.07.1995
7“ ‘

The vibration analysis appeared to be a very useful tool for controlling single shots
in the delay sequence. MultipIe shots caused problems. They might be recognized by
taking more parameters (specially rock parameters) into account.

The correlation between the drilIing parameters, the main faults detected with the
endoscope, and the missing peaks of the cut seismograms, provided promising results
on the blastability characterization during drilling, but were not sufficient to conclude
on this point.

The grain size distribution measurement showed an homogen~us family of grain size
distributions for the blasting pattern used in Erzberg. Nevertheless, some significant
differences in some bIasts can be linked to a bad explosives ener~v distribution
-
(confirmed by the explosives measurements), ‘“

This last step of the phase dedicated to the development of the blasting control
methodology fiswered the initial key question of what to expect from the control of the
blasting process.
9

. . ,,

Contract IHUZ2. CT92.0127 Project report n“ 8

Blasting Control 9. 01.11.1992-31.07.1995
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Contract BRE2.CT92.0127
Project report n“ 8
Bki.sting Control 10 01.11.1992-31.07.1995
 1

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C(]ntrwct IIRE2.CT92.0127 Pro.jwt report no 8

Bkisting Control 11 01.11.1992-31.07.1995
 PIIASE 111: VALIDATION OF BLASTING CONTROL METHODOLOGY

The last phase of the project has been dedicated to the validation of the developed
methodology. This validation took place in a mine in production (Bauxites parnasse) under
working conditions.

The first step aimed at proving that the complete monitoring of blasts was realistic in
working conditions (acquisition validation). The following step aimed at showing that such
a control could provide the blasting expert with efficient information for the blasting
improvement (example of therapy).

111.1 ACQUISITION OF VALIDATION

The validation of the acquisition with control devices has been made in the Bauxites
Parnasse mine through nine blasts made in two drifts (5 in bauxite and 4 in limestone).
e
The first two weeks were used to prepare, install and calibrate the chosen devices, to
prepare the measurement places, and to install the data recording system.’ Then the tests took
place. Finally, a database, similar to the Erzberg’one, has been realized.
. .
The testing period in Greece has been successful in terms of data acquisition. The
applied measuring system (on basis of the experience gained at Erzber~ test site) proved to
,work properly. Some minor technical problems occurred, which should be easily eliminat~
for further operations. Table 1” summarizes the main results :
. .
device technical time data further
probIerns constraint storage improvement
I drilling no less good sensors
lifetime
@ endoscope no big under work handling
grain size ‘ no less good
distribution
vibration yes less good
surveying no big good handling
core drilling no big under work
deviation no medium under work

Table 1: Results of the acquisition validation tests

Contract BRE2.CT92.0127 kojc~t report n“ 8

Blasting CcmtroI 12 01.11.1992-31.07.1995
This test phase reached its two objectives : the tools work and the feasibility of full
monitoring in working conditions is proved.

The acquisition is then considered to be validated.

IH.2 EXAMPLE OF THERAPY

Measurements made during the acquisition validation have been used by blasting
experts in order to propose a new blasting scheme supposed to improve the geometrical
results of the blasts. For this, the blasting experts group choose to concentrate on the
ge6metncal problems in bauxite where the actual advance, the actual profiles and the grain
size distribution were ve~ far from the planned ones. In order to reach their conclusions, ~e
main ideas developed where the following :

The obviously high drilling deviation is the main reason for the generally bad blasting
results. Other influencing parameters can be neglected regarding the deviation. The
new blasting scheme must have an easier drivability.

- Some weakness of planned drilling pattern exist, in particular for the first helpers
considered to be too far from the cut. This point explains the bad granulometry.

- The un~oaded borehole length is generally too ‘high and the energy distribution is not
optimal. This point also explains the bad granulometry.

In order. to solve the problin of fines (too numerous)” and. in addition to the two
“previous points, the ex~losives have been changed for a combination .of gelatine and
ammonite. This change will also help a proper contouring, of the blasts.

As the center hole cannot be enhrged (no specific drilling equipment is available), a
specific delay pattern for the spiral cut has to be used in order to provide free
volumes.

From their analysis, new drilling, loading and ignition schemes have been proposed
for bauxite in order to increase the advance, ameliorate the profiles, ad produce less fine
material.

To validate these shemes, 4 blasts were done in one drift, monitored with a theodolite
(for profile and advance), seismographs (for efficiency) and image analysis (for the fine
material).

All but the vibration data from the different devices (electronic based data or
handwritten) were stored immediately after the blast in the database Access, and transferred
to Surpac for immediate calculations and visualizations.

The main geometrical results of the tests can be commented as follows :

Contriict BEZE2.CT92.0127 Project report n 08

Blasting Control 13 01.’11.1992-31.07,1995
 There is a quite satisfying correspondence between the planned and actual values of
the drilled volumes for the cut, the production zone and the contour zone. Especially t
in the cut zone the result has been considerably improved.

The comparison between the actual and planned total volume drilled and blasted again
gives satisfying results.

Especially the advance achieved is excellent. Of the length drilled, actually in average
94,5 % could be blasted.

The- immediate measurements calculations and visualizations ‘enabled to discuss the

results of the validation tests direetly in the mine at the end of the validation test
period.

The results of the tests were demonstrated in front of an audience of mining enginkers
and foremen at the offices of the mine. The example of therapy, centred around the advance
and the fine materials, looks very promising and interests Bauxites I%rnasse a lot. Such a
O P attem. could be extended to account for mechanical properties of rock and desired
granulometry of blasted material. This could turn out to be an extremely useful tool in the
hands of the underground mining engineers and foremen of the mine.

It is thus considered that the objectives have been reached and that the key question
on the possibility to propose an efficient therapy from the controt measurements is
“positively answered.

4 . . . . CONCLUS1ONS . .

The generaI conclusions of the project can be directly linked to its initial objectives.
They are :

It is considered that the blasting control methodology developed in the project proved
a to be realistic (in terms of working conditions in a mine in production) and efficient
(in terms of blasting improvements].

The application of the results in our end-user mine (Bauxites Parnasse) is very
promising and opens the door to other types of improvements.

The adaptation of the methodology to any new underground mine should not be of a
great difficulty.

Several controI’devices, adapted to mining working conditions, are now available for
further uses or developments. They can be directly used for production control (grain
size distribution) or envirorimental control (seismographs; noise and airbiast
equipments). They can also be developed in other industrial research projects (drilling
jumbo or endoscope).

Contract BRE2.CT92.0127 Project report n“ 8

Blasting Control 14 01.11.1992-31.07.1995