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Sustainable Low Impact Mining solution for exploitation of small mineral deposits based on advanced rock blasting and environmental technologies

Periodic Reporting for period 2 - SLIM (Sustainable Low Impact Mining solution for exploitation of small mineral deposits based on advanced rock blasting and environmental technologies)

Reporting period: 2018-05-01 to 2019-10-31

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, pre- and post-blast rock mass characterization (automatic rock mass characterization from images, fragmentation measurement and muckpile properties), modeling of the rock/explosive interaction with numerical codes and semi-analytical models to predict damage zone extent, fragmentation and far field vibrations.

The SLIM solutions encompass a better control and prediction of the operation. Tools and models are being 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.
Technologies and tools to account for rock mass characteristics, fragmentation, blast damage and vibration are being developed. Further development of the measuring procedures defined in the first part of the project to characterize pre-blast rock mass characteristics have been carried out. This includes Measuring-while-drilling (MWD) data in four sites, measurements of the high wall with photogrammetry and LiDAR data of the block face in one quarry and two open pit mines, and in-hole photography of the blasthole walls with optical televiewer. Damage to the remaining rock is determined from televiewer and close range acceleration measurements; the latter used to calibrate near-field seismic model.
Different techniques, like in situ and lab sieving combined with analysis of images taken by Unmanned Aerial Vehicles Systems (UAV) and terrestrial laser scanning, have been applied to measure fragmentation from blasting. A numerical procedure to calibrate the Ignition and Growth equation of state (EoS) for three emulsion explosives has been developed. This EoS that takes into account non-ideal detonation regime has been considered to model in LS-Dyna the performance of these explosives in a wide range of conditions. A procedure to measure detonation pressure of explosives in controlled (laboratory) and production environments (mine) have been developed. The parameters that govern the production of toxic fumes from blasting have been studied and guidelines to reduce the production of toxic fumes are provided.

LS-DYNA code has been run using different numerical techniques to describe the rock and the explosive. Among others, the effect of timing and rock mass properties 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) models of single and multiple holes have been developed to model the near-seismic field, aiming at building damage plots of the remaining rock mass. A semi-analytical model has been developed and calibrated to assess velocity and acceleration fields in near seismic field. Based on these data, a procedure to calculate the stress field and evaluate the extent of damage in the rock from these radiation patterns is also provided.

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 has been assessed in El Aljibe quarry using continuous dust samplers. Dust emission factors (EF) for mucking and blasting have been quantified. Solutions to control dust production in blasting have been implemented and evaluated. 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.
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.
A new software application for designing surface blasts is being developed.

Preparatory and validation trials have been carried out in two mines to assess whether the solutions developed in the project results in an increase of the plant performance. 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.
A SLIM Checklist for Exploitation has been used in a similar way as the Innovation Radar Questionnaire.

Dissemination of the project activities and results has been done through numerous poster and oral presentations in conferences and workshops, project website and social media representations. A first SLIM video has been produced.

The main stakeholders of the SLIM mines have been identified. Best practices on social awareness communication and guidelines for local communities have been elaborated.
The following developments are state-of-the art level:
- A procedure to calibrate the Ignition and Growth equation of state for civil explosives.
- Technologies to measure detonation pressure of explosives in controlled (laboratory) and production environments (blasting site).
- New technologies to characterize rock mass.
- Low cost drilling monitoring system.
- Improved fragmentation measurement tools from terrestrial LiDAR and UAV images.
- Engineering tools to predict fragmentation and rock motion.
- A semi-analytical model to assess vibrations in the near field. Use of these data to calculate the stress field and evaluate the extent of damage in the rock mass.
- Numerical models of near field vibration, bench face initial velocity and response time.
- Measuring and analysis procedures to analyze damage by blasting from borehole logs with optical televiewer.
- Implementation of different solutions to control dust production in blasting.
- 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.