The mining industry is constantly changing and currently the technological progress is not homogeneous through all its production stages, standing out one more than others, because of the application of digital programs that allow forecasting much more precisely results from the mining operation.
Underground mining and its different mining methods, are constantly on the quest to attain its results, improving its benefits, in order to become a large-scale mining, which could face challenges within a market that constantly shows variations in mineral pricing and commercialization.
As part of this industry, it is our duty to innovate and apply new technologies; that allow us to manage the information and data from the production processes, aiming to make more accurate decisions to increase economic margins and that those generate for us great benefits (mining speed, mineral recuperation quality, transport and hauling, among others).
The present paper will analyze and explain, how the realistic 4D blast simulation will help us to achieve these challenges to fit them to production time and, moreover, precisely foreseeing the underground blasting results. It is so, considering its particularities, as for example, its execution within confined spaces, the absence of free face and the variability of the mineralized structure calculations shall be made to ensure optimal results.
Based on the rock fragmentation mechanisms with explosives, digital innovative models and most up-to-date simulation systems will allow us to design a digital model of realistic 4D underground blast simulation. This new model will manage to represent simultaneously the rock fragmentation, movement, seismic levels, dilution and blast damage so fast that will facilitate for us making immediate decisions, with no impact on the production cycle. It is to say, obtaining and evaluating blast results before executing it.
Empiricism & Digital Simulation
The process of trial and error has been a determined factor since the beginning of centuries; The mining world is not unaware of it! Therefore, we start the Method of trial and Error trying a variety of charging models with different explosives, multiple starting sequences, we adjust the geometry of the blasting pattern again and again until getting our results; though a modification in the conditions of the field leads us back again to make the exercise of trial and error over and over. Today we know that a blast carries with it a complex physical phenomenon of detonation mechanics, thermodynamics and ballistics, far away from the traditional random change of parameter to perform the trial-and-error method.
The digital simulation opens us the doors to the virtual world, where we can, from the target’s identification and the awareness of physical factors that leads to the optimization of the process, to set the necessary parameters in the digital simulations of this complex physical phenomenon through digital dynamic interactions, that allow us making more accurate decisions across our operations.
Execution Methodology
To start using simulation programs, it is necessary collecting data in situ (Blasting Method, geology, hauling equipment and drilling) and on field blast audits, that allow us to build a line of blasting data base; with different settings of the drilling mesh and on different rock qualities. This process is the starting point for future improvement models, in fragmentation domains, vibration, cast and blast damage.
When creating a symbiosis among the collected data and the digital processes; it will show us various scenarios of the simulated results from our blast, allowing us to have, not only a perception, but a real understanding of the effects of each parameter that represents the blasting process in different results simulated to determine which scenario meets the best our targets. Figure 1.
We characterize the rock mass with the obtained data; to be able to propose a pattern design with specific geometry loading and timing sequences in order to simulate the blast and evaluate the results. The obtained effects will allow us to have the adequate criteria to determine and/or adjust designs; considering the quantity of over size, the vibration limit, the air blast limit, the damage on the rock mass, the dilution, and safety among other targets; which we consider for our blast.
- Site Information –
To start we have to identify the underground mining method that have been being implemented, which will enable us to have a macro vision of the mining works, the geology and the type of mineral deposit that presents the zone, with these two factors we will be able to have information about the mining process, dimensioning of drilling equipment, blast, cleaning and hauling inside the mine. Figure 2.
- Drilling Audit and blast. –
To implement this process, it is important to keep in mind the targets we expect to attain among others, in terms of fragmentation, vibration monitoring, dilution, over beak, safety or a combination of them. The analysis of drilling cycle will start from these targets and from each of its parameters starting with the current geometry of the drilling pattern, the drilling process itself, including symmetry, depth, parallelism, inclination and drilling speed. Figure 3.
When we talk about blasting, we are making reference about putting explosives in the drilled bores, confine them accurately, establishing sequence times and that after the detonation process, which releases great quantities of energies, gases at high pressures and temperatures, will result new cracks and movement of the mass rock; it is there, where we will audit the technical characteristics of the product (Manufacturer’s Technical chart vs Field measurements) and its performance in line with the conditions of the mass rock. Figure 4 & 5.
- Geomechanical Mining Parameters. –
Based on the fragmentation mechanism of the rock, it is important to initially make a detailed study of the zone including geotechnical recognition campaigns with on field activities, as geomechanical login, geometrical mapping and geophysical tests. With the obtained data from measurement while drilling, correlated with the local geology, such as the simple compressing resistance, traction strength and toughness for different lithologies, as well as its geomechanical classification Rock Mass Rating (RMR) and Rock Quality Designation (RQD) it will give us settings that will be applied on our calculations and/or analysis with the I-Blast software. Figures 6 & 7.
With the measure of time arrival of the main vibration resulting from the blast at each seismograph sensor (geophones); in a period of time; we will be able to determine the velocity of the P wave (Vp), that will allow us modeling the transmission of compressive and tensile stress wave along the exploitation zone. This factor (Vp) is related with the elastic module of the media, it is to say, the mass rock.
- Drilling Pattern Design and Blast.
Determining the accurate drilling geometry for the underground mining blast, is linked to use and analysis of various parameters with specificities. For the purpose of this document, we will analyze a mineralized vein blast from level to level (long drills). Figure 8.
The determination of the initial drilling geometry of this case; will be linked to the geomechanical settings previously mentioned, intending to overcome the resistance values of the rock to blast in order to reach the ideal fragmentation, without affecting the deposit structure resulting from the uncontrolled vibration of the blast.
It is important to mention that, during the drilling we can also collect information about the rock strength parameters that will help us redesigning the explosive loading in each one of the blasting holes. Figure 9.
- Blasting Simulations. –
One of the challenges of the blasting automation process, is to benefit from the power of digital systems to make several simulations according to the mechanism of the effects caused by the different characteristics of the explosive in the mass rock and attaining targets on each blast. The main challenges that currently face the underground mining are dilution or ore grade control, cast control, monitoring damages produced by the vibration on the mass rock and safety in operations, to obtain a homogeneous fragmentation with a passing size of 80%, that facilitates its mucking, hauling and plant processing.
Fragmentation, upon obtained results for fragmentation simulations; we can determine a geometrical setting of the burden and spacing to improve fragmentation and the benefits that entails such optimization.
This simulation model of fragmentation must be calibrated with the obtained results after the blast performed.
Among post blast results, fragmentation is one of the most important performance index and it is quite related to the production performances; because of its direct influence on mucking and hauling; as the monitoring of the fragmentation processes, the vibration level are monitored. The use of software will allow us to measure and compare fragmentation results, the actual measures versus the simulated ones. Figure 10.
Dilution, it is the mix of low ore grade or sterile material with rock mass that has a percentage of ore content above the cut-off grade that we want to extract. In many cases, it is not possible to know in which proportion the dilution turned out even after extracting all the blasted material. Currently, it is already possible, by the means of mathematical models to simulate and be able to determine zones where dilution of the ore will turn out and, therefore, minimize the phenomenon that generates economical losses in the extraction process. Figure 11.
Damage from blasting, During the detonation process; a big release of energy is produced; which, part of it is used to generate new cracks and movement of the blasted material; the energy in excess continues to travel in the rock mass, becoming alternatively compressive and tensile wave that generate damages on the rock mass.
Currently, it is possible to make simulations that allow to identify the most sensitive zones of damage from the blast, being able to predict the level of vibration on any point around the blast to optimize our sequence and explosives loading. Figure 12.
We will perform the calculation with site information, characterization and geomechanical parameters (velocity of P wave, rock strength, Young Module) to obtain PPVc (critical Peak Particle Velocity) and minimize PPV based on mathematical models.
Energy Distribution,
At this stage of the simulation, it allows us to analyze the interaction of explosive charges in each of the blast holes, along the entire drilling length and be able to readjust the amounts of explosive needed to fragment only the ore body, without generating damage to the rock mass that may produce dilution. On the other hand, it allows us to optimize the required fragmentation, to make efficient the mucking and hauling processes of the ore Figure 14.
We will perform the calculation with site information, characterization and geomechanical parameters (velocity of P wave, rock strength, Young Module) to obtain PPVc (critical Peak Particle Velocity) and minimize PPV based on mathematical models.
We will perform the calculation with site information, characterization and geomechanical parameters (velocity of P wave, rock strength, Young Module) to obtain PPVc (critical Peak Particle Velocity) and minimize PPV based on mathematical models.
On site seismic monitoring allow us to evaluate the level of damage that was generated and calibrate the simulation model. Figure 12.
Conclusions
Currently the Digital 4D Simulation based on real parameters and physics, is a powerful tool to predict blast results and be able to optimize drilling parameters hole loading and timing to achieve our blasting goals.
Reliability from performed simulations, is directly correlated to the data and/or collected information; it is important to point out that any variation in the input parameters (type of rock, kind of explosive, timing sequence, etc.), will lead us to have field results different from whose obtained by the simulations.
It is important to highlight that the success of our realistic 4D simulation, will be based on the reliability of the data that we can collect from field measurements and site information.
Results
With the obtained results from each blast, it will be possible to define and validate our simulation model adjusted to the parameters present in our field work in a continuous way and be able to obtain blasts with efficient results, that generate for us greatest benefits, either economical, technical, productive and as for security. Figures 13 & 14
