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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SLIM (Sustainable Low Impact Mining solution for exploitation of small mineral deposits based on advanced rock blasting and environmental technologies)

Teaser

Summary

The project develops technological solutions for increased productivity of small mining operations, helping difficult mines balance sheets fall into profit. Technologies include characterization of explosive and pre- and post-blast rock mass characterization (e.g. fragmentation measurement and muckpile properties) and numerical modeling of the rock/explosive interaction.

The SLIM solutions will be validated downstream in some mines by monitoring processing plant key performance indicators so as to ensure both its performance and its integration capacity within the mining and processing value chain.

Besides technical aspects, SLIM addresses environmental, social and economic dimensions, including workers safety and environmental impact (nitrates leaching, vibrations and airborne particulate matter). Dissemination, communication and social innovation actions are also included.

Work performed

Tools to account for rock mass characteristics on fragmentation, blast damage and vibration are being developed. Measuring-while-drilling (MWD) data has been monitored in 96 blasts. Data from VA Erzberg have been filtered and analysed to build a geochemical model of the iron content as function of MWD data. Structural characteristics of the rock mass are determined from photogrammetry and LiDAR data of the block face and in-hole photography of the borehole wall with optical televiewer, the latter used for validation purposes. Wall damage is being determined from televiewer measurements and close range acceleration measurements, and is used to calibrate near-field seismic model.

Performance of an emulsion explosive has been investigated through cylinder tests. The results have been used to calibrate the JWL EoS. Tests to measure the detonation front curvature and velocity of detonation are used to determine the Ignition and Growth EoS. LS-DYNA code has been run using different numerical techniques to describe the rock and the explosive. Among others, the effect of timing on fragmentation is being determined from it. Initial velocity of rock fragments and response of the rock mass to the detonation is also studied.

Three major topics have been covered on environmental impact and safety: vibration from blasting in the near and far field, airborne particulate matter, and the application of lining while charging in open pit mines. 2D and 3D numerical (LS-DYNA) and analytical (Heelan-Blair) models of a single blasthole with a free face have been developed to model the near-seismic field, aiming at building damage plots of the remaining rock mass. A far-field seismic model is being built for the sub-surface of Erzberg mine, which is used to forward-model the influence of certain blast layouts on the vibrations at specific spots in the mining area. Dust emission produced by drilling, blasting and mucking is assessed in El Aljibe quarry. A dispersion model of TSP and PM10 has been developed and calibrated from data. Sources of dust generation for several mining activities and the mitigation measures commonly applied are reviewed. A prototype for a lining while charging device to reduce nitrates leaching has been developed.

A new explosive formulation, RIOMEX 10000 DS emulsion has been developed and tested. It has two forms: chemically gassed and physically sensitized. The ranges of density, velocity of detonation (for confined small diameters), viscosity and energy have been determined. Delivery systems that allow changing the density and viscosity of the bulk explosive while loading into the blasthole have been developed. Nitrates leaching properties have been assessed against viscosity, presence of ammonium nitrate prills (e.g. ANFO blended with emulsion), type of fuel, nature of emulsifier and composition (single or dual salt emulsions). A new explosive characteristics module has been implemented into the software Rioblast, a new version of which, called RIOSLIM, has been developed specifically for the project.

A new concept for the characterization of blasting results by analysis of UAV-borne images is being developed. Experiments in real and laboratory scale have been done to optimize image acquisition, integrating analysis of different cameras and different image configurations. Adaptations of existing algorithms and development of machine learning algorithms have been done.

A new software application for designing surface blasts is being developed. The algorithm for automatic characterization of the main rock structure features in the bench face has been applied to various 3D data sets.

An environmental assessment has been started to quantify all relevant emissions and resources consumed and the related environmental and health impacts and resource depletion issues that are associated with the technologies developed in SLIM. The goal and scope definition has been completed and a plan for acquiring the information relating

Final results

The following developments are state-of-the art level:
- New tools to characterize rock mass.
- Low cost drilling monitoring system.
- Improved fragmentation measurement tools from LiDAR and UAV images.
- Engineering tools to model and design fragmentation and rock motion.
- Use of spectral analysis of near-field vibration waveforms to investigate rock damage.
- Calibrated numerical models of near field vibration, bench face initial velocity and response time.
- Determination of the effect of delay time on over-excavation.
- Dust dispersion model and emission factors of TSP and PM10 from different mining activities as an alternative to those proposed by US EPA.
- A formulation of a high stability, repumpable emulsion, with very high shelf life, and related delivery systems.
With the following expected potential impact:
- Blast design tools developed will assist mines and quarries to use explosives more efficiently through a better blast design and reduce total mining costs. What is true for Europe is becoming true for mines elsewhere in the world. The SLIM developments are employed in assisting mines globally, and especially attractive to those mines and quarries which could have, or have had, issues with ground water contamination.
- The automatic blast design software enables analytic and objective optimization of blasts. It mitigates the risk for negative impacts such as fly rock or vibrations and concurrently brings economic advantages to the mines and quarries.
- The chosen approach for characterizing muckpiles has high potential to overcome current weaknesses. Only reliable and correct assessments of blasting results allow to improve and audit the work in the mines.