WP3 ENVIRONMENTAL IMPACT AND SAFETY
MUL, UPM, ARNÓ, VA Erzberg GmbH, InvestorNet, LTU
WP3 aims to provide mines and other raw material extracting industries working with explosives with modern techniques that
substantially decrease the societal disturbances and environmental foot print of their blasting work without decreasing
the productivity of the operations.
3.1. A NEAR-FIELD SEISMIC MODEL FOR VIBRATION MINIMISATION
MUL, UPM (lead), LTU, ARNO
Blast contour design approaches based on the estimation of the PPV generated by the explosive shock waves have been developed over the years. Starting from the well-known Holmberg and Person approach, the PPV was measured at different distances from the blasthole and was correlated with the lineal charge concentration and the extension of the damage created by the blasting effect. W. Hustrulid studied the particle vibration generated by blasting effect in the near field and described two approaches for estimating the PPV around the blasthole: The Colorado School of Mines Approach, based on the study of the necessary time for the propagation of the detonation wave between explosive charges and the p-wave velocity in rock mass; and the New Hybrid approach, based on Heelan Solution, in which changes on the blasthole pressure during the detonation were considered and the radial and vertical components of the wave were combined. The computational efficiency of such models is offset by their limited flexibility in terms of geometry and detonation modelling and is becoming less important in favour of finite element models as computers velocity of process increases.
In this task, analytical solutions will be compared with the ones obtained with dynamic finite element models. The following work will be carried out:
Subtask 3.1.1 – Near-field vibration measurements (acceleration and particle velocity, field tests)
Single-hole tests. (UPM, ARNO)
Multiple-hole tests. The production blasts tests in subtask 2.3.1 in WP2 will be used for this purpose. (UPM, ARNO)
Correlation of vibration levels with rock damage measured in subtask 2.2.2 in WP2 (UPM)
Subtask 3.1.2 – Numerical modelling
The LS-DYNA code will be used to model blast-induced vibration and damage. The detonation of the explosive will
be modelled with ideal and non-ideal detonation models and the rock mass with the Riedel-Hiermaier–Thoma (RHT)
model, which is an advanced plasticity model for brittle materials such as concrete and rock. The explosives parameters
will be calibrated in WP2.1 and the RHT model data in WP2.4. The following work will be done:
Determination of the vibration velocity and acceleration field. Single hole. (UPM, LTU)
Multiple-hole modelling. (UPM, LTU)
Damage prediction (UPM, LTU)
3.2. A FAR-FIELD SEISMIC MODEL FOR VIBRATION MINIMISATION
MUL (lead), ERZBERG
This task will oversee the development of a far-field seismic model and its use based on the following actions:
Subtask 3.2.1 – Site characterization and subsurface model for VA Erzberg mine
Maps of site, characterization of blasts; geometry, loading, delay times
Id of sensitive targets and statement of admissible PPV and frequencies of blast vibrations
Determine sensor array positions for 50 seismic sources
Drill source holes; 50, Ø48 core mm, up to 5 m deep
Shooting of test shots with 200-500 g dynamite charges to determine seismic wave field
Analysis of site characterization signals
Construction of topographic heterogeneous subsurface model for VA Erzberg mine
Subtask 3.2.2 – Optimization of blast patterns at VA Erzberg
Selection of range of realistic blast patterns (orientation, drill pattern, delay times, sequences) and of sensitive targets.
Numerical forward modelling of selected blast patterns to determine minima and maxima in vibration wave field.
Preliminary recommendations of blast patterns that minimize PPV in given frequency range at selected targets.
Subtask 3.2.3 – Validation of blasts for minimal vibrations at VA Erzberg
Selection of 5-10 optimal blast patterns, 3 sensor array deployments
Use of matched pairs technique for blasts at different places in mine
If possible cooperation with LWC topic work
Final recommendations of blast patterns design for VA Erzberg conditions
3.3. AIRBORNE PARTICULATE MATTER IN MINING: GENERATION AND MITIGATION
UPM (lead), ARNO, LTU
Air pollution is a major environmental health problem affecting workplaces and urban areas in the vicinity of mines and quarries. Among the most frequently air pollutants such as ozone or nitrogen dioxide, suspended particulate matter (PM) has the major influence on human health and welfare. PM is complex mixture of very fine particles suspended in the air. It is main formed by two fractions: PM10 and the fine PM2, with aerodynamic diameters smaller than 10 and 2.5 μm, respectively. Some PM have a natural origin like windblown dust from agricultural processes, uncovered soil, or it comes from natural hazard. But also anthropogenic activities produce large amount of suspended particulate matter.
Near these sources emission, sedimentable particulates (greater than 20 μm) fall out from the air to the ground, whereas the most dangerous suspended PM can be transported large distances and could pose health problems.
Another concern is the composition of suspended and sedimentable particulate matter. This quarry is representative of small mines in Europe that are a source of emission of pure crystalline or free silica in suspended particulate. Nonoccupational exposure to silica composed PM produces lung diseases like silicosis and increases the risk of tuberculosis and autoimmune diseases.
The main work to be carried out within this task are:
Subtask 3.3.1 – Assessment of total suspended and particulate matter (PM) production in mining
Quantification of emission factors in different mining activities: blasting, loading and hauling, primary crushing using a network of fix and mobile gravimetric dust samplers. (UPM, ARNO)
Occupational and non-occupational exposure to silica dust using personal dust monitors with filter capsule for quartz analysis (UPM, ARNO)
Subtask 3.3.2 – Small scale blasts to assess generation of very fines (LTU)
The amount of total suspended particulate matter (SPM) from blasting will be investigated from small scale blasts carried out in subtask WP 2.3.3. For this purpose a device to capture SPM will be designed and used in 2 to 4 tests on mylonite samples collected in ARNO. SPM will be studied down to 2.5 microns, which is the fraction accounting for more health problems.
3.4. LINING OF BLASTHOLES TO REDUCE NITROGEN LEAKAGE AND CONTROL OF EXPLOSIVE CHARGE
MUL (lead), ERZBERG
This task will demonstrate the technical function of the lining-while-charging (LWC) of blastholes with ContBlast units for normal hole size of small open pit mines or quarries. Keeping the emulsion column under control will substantially decrease environmental impact (nitrate leakage), charge malfunction (detonation failure) and safety (fly rock) when blasting in fractured and wet ground
Subtask 3.4.1 – Specifications and tests of LWC in normal quarry holes
Specifications of charging conditions; pressure, chemical environment, safety issues etc.
Design of a ContBlast unit for lining while charging (LWC) with considerations for placement of detonator and primer
Manufacture first prototypes of ContBlast unit with 3D printing, up to 40-50 units
Drilling of either 40-50, Ø76 or 89 mm, 15-20 m deep blastholes, some if possible in wet ground
Charging with ContBlast units and MUL-BBK emulsion pumping unit and explosives from Austin powder
Checking for emulsion leakage through rise of emulsion column during gassing
Blasting of holes while checking for detonation failures
Evaluation of design of ContBlast unit and redesign according to experience
3.5. VERIFICATION TESTS
MUL (lead), UPM, ARNO
Following the execution of the previously described tasks, the following field tests will take place:
Subtask 3.5.1 – Verification of near-field blast damage prediction model
Blasts in the ORGIVA mine, made under WP2.5, will be used to verify fragmentation and near field vibration modelling
completed in subtask 3.1.2
Subtask 3.5.2 – Verification of blast vibration optimization procedures at ARNO
The work done under tasks 3.2.1-3.2.3 will be repeated but the work will be more efficient because of the experience
of how to best model the subsurface and optimize the blast patterns. Depending on the subsurface at ARNO and the
sensitive targets, the optimized blast patterns may look quite different than at the ERZBERG.
– Site characterisation at ARNO
– Modelling of ARNO subsurface
– Optimisation of blast patterns
– Validation blasts at ARNO
– Final recommendations and reporting on blast optimization procedures
Subtask 3.5.3 – Verification of dust suppression measures in ARNO mine
Depending on the results of WP3.3, which ends in month 24 and where the main sources of particulate matter will be
defined, suppression measures will be tested. (UPM, ARNO).