Determination of Abrasiveness in Copper-Gold Sulfide Ores: A Contribution to the Geometallurgical Model of the Sossego Deposit

The geological context of this study is established in the iron oxide-copper-gold (IOCG) deposit of Sossego (Canaã dos Carajás, Brazil), where hydrothermal alterations in shear zones concentrated the metals of interest and added new characteristics to the metavolcanic-sedimentary and granite rocks. The mineral transformation of rocks by hypersaline fluids enriched in metals and silica also modifies some metallurgical properties, such as abrasiveness. Special bench tests on rock drill cores are used in mapping the abrasiveness of rocks, with the Bond abrasion test being more commonly used in the mining industry, but it has a restrictive sampling protocol and mass requirement for geometallurgical studies. As a counterpoint, the test of the Laboratoire Central des Ponts et Chaussées/Central Laboratory of Bridges and Roads (LCPC) requires a smaller amount of fine material and a finer granulometric range. The study on the use of LCPC was implemented in 40 samples, using Bond Ai as a reference. The results showed a strong correlation between both methodologies (R2 = 95%), validating the use of LCPC to quantify abrasiveness in the Sossego mine. It was also possible to classify the most abrasive lithologies.

One-Dimensional Convolutional Neural Network for Drill Bit Failure Detection in Rotary Percussion Drilling

Drill bit failure is a prominent concern in the drilling process of any mine, as it can lead to increased mining costs. Over the years, the detection of drill bit failure has been based on the operator’s skills and experience, which are subjective and susceptible to errors. To enhance the efficiency of mining operations, it is necessary to implement applications of artificial intelligence to produce a superior method for drill bit monitoring. This research proposes a new and reliable method to detect drill bit failure in rotary percussion drills using deep learning: a one-dimensional convolutional neural network (1D CNN) with time-acceleration as input data. 18 m3 of granite rock were drilled horizontally using a rock drill and intact tungsten carbide drill bits. The time acceleration of drill vibrations was measured using acceleration sensors mounted on the guide cell of the rock drill. The drill bit failure detection model was evaluated on five drilling conditions: normal, defective, abrasion, high pressure, and misdirection. The model achieved a classification accuracy of 88.7%. The proposed model was compared to three state-of-the-art (SOTA) deep learning neural networks. The model outperformed SOTA methods in terms of classification accuracy. Our method provides an automatic and reliable way to detect drill bit failure in rotary percussion drills.

Identification of Rock Mass Critical Discontinuities While Borehole Drilling

Modern technologies need more mineral resources for energy generation, metallurgical products, chemicals, and many other uses. These resources are usually extracted from the Earth’s crust. Many engineering underground-space infrastructures are left after mining activity, with their very interesting features such as very large storage capacities (e.g., for hydrocarbons, hydrogen, radioactive, or other waste), and long-term geomechanical stability. Our original experiments were carried out in the conditions of an underground metal ore mine where typical mobile drilling rigs, additionally equipped with a set of sensors for recording signals as effects of rock–drill interaction were used for the research testing. A series of boreholes with diameters of Ø38 and lengths of up to 9 m in the rock medium were drilled in the “weak” and “strong” rock masses, and the frequency spectra of their signals were analyzed with the use of the fast Fourier transform (FFT) and short-time Fourier transform (STFT) algorithms. According to the proposed idealized theoretical model of the disturbance and the distinctive acceleration value of the drilling characteristic, the location of the critical discontinuities in the roof of the excavation were recognized. The most important advantage of the proposed method is the quantity and objective monitoring method for detection of a critical rock mass defect (discontinuity) that is significant for the potential functionality of underground workings as a potential energy storage room and their reinforcement.

Research on the Matching of Impact Performance and Collision Coefficient of Hydraulic Rock Drill

The stress wave produced by the piston impact, on the drill rod, is an important factor affecting impact performance. It is particularly important to control the stress waveform generated by the piston impact on the drill rod to meet the requirements of efficiency and component durability of some impact mechanical systems. Based on wave theory, the impact stress wave model of rock drilling is established, a dimensionless collision coefficient γ is put forward, and the matching relationship between different collision coefficients γ and stress waveforms is analysed. The length of the impact piston under the same material condition determines the change rule of the waveform. The stress waveform experimental verification is thus designed. The pressure chamber curves of different pistons in the rock drill were tested, the collision velocity of the piston was obtained, and the impact energy and impact power were calculated. The relationship between the impact performance and the collision coefficient γ is analysed. When γ is in the range of 9–11, the impact piston’s design of a high-power rock drill can be satisfied. When γ is in the range of 3∼5, it is mainly designed for low-power rock drills.

Cave wall-rock alteration as an indicator of hypogene speleogenesis

<p>Recent years have seen an increasing number of studies suggesting that hypogene processes are more important in the origin of cave systems than previously thought. Recognizing such hypogene caves has important implications for e.g. paleohydrology and has been primarily based on morphological criteria, which to some degree are subjective and difficult to quantify. Apart from caves containing coarsely crystalline spar backed by evidence of elevated paleotemperatures based on isotopes and/or fluid-inclusion data, there are no well-established physico-chemical tools to validate a hypogene model for a given cave.</p><p>In a systematic approach we have studied a number of cave systems showing morphological features diagnostic of upwelling fluids, and examined the composition of the rock immediately behind the cave wall using small-diameter drill cores. We commonly observed two features in this wall rock: (1) an increase in porosity (partly later occluded by carbonate cement) and (2) a change in the rock colour (bleaching of initially grey rock, or reddening). We also identified dedolomitisation of the dolomite host rock, which may locally lead to the formation of boxwork. The most diagnostic feature, however, is a systematic shift in the carbon and/or oxygen isotopic composition along wall rock drill cores. None of these petrographic and geochemical features were observed in wall-rock cores of epigene caves, opening the door to use this approach in order to identify, and in some cases quantify, paleo-water-rock interactions associated with hypogene speleogenesis.</p>

Porosity estimates from marine controlled source electromagnetic dipole-dipole data at the Scanner Pockmark in the North Sea

<p>As part of the EU Horizon2020 ‘STEMM-CCS’ project, controlled source electromagnetic (CSEM) and seismic data were acquired in 2017 at the Scanner Pockmark in the UK sector 15/25 of the North Sea, which is actively venting methane gas, to contribute to the evaluation of risk from potential fluid pathways to the sequestration of carbon dioxide in geological formations. We will present some preliminary results and relate electrical resistivities to sediment properties such as porosity and gas saturation.</p><p>The CSEM data presented were acquired with a University of Southampton deep-towed electric dipole source and two towed three axis dipole receivers (Vulcan, Scripps) along 12 profiles across an active pockmark. The data were processed in the frequency domain and the electrical resistivity structure was inferred with a 2D regularized inversion algorithm (MARE2DEM, K. Key).</p><p>To estimate porosities and their uncertainties to about 200 m below the seafloor, we use the empirical Archie’s law and calibrate Archie’s coefficient using physical properties measured with the multi-sensor core logger on gravity cores and sediment cores from the British Geological Survey Rock Drill 2 rig. Geological horizons identified on reflection seismic data are used as constraints in the resistivity model. The resulting porosity profile decreases with depth due to compaction and can be related to marine and glacial deposition environments.</p>

Research on Impact Performance of Hydraulic Rock Drill with Floating Characteristics of Double Damping System

As a technological innovation of high-power hydraulic rock drill, double damping system has a very important effect on impact performance. The double damping system is a floating mechanism. The characteristics of the floating mechanism have an important influence on the impact energy, frequency, and power of the hydraulic rock drill. Based on orifice throttling theory, the static equilibrium position of a damping piston was calculated, and the characteristic parameters of the double damping system were summarized as damping flow (Qd) and feed force (Fd). According to the characterization parameters of the double damping system, an experimental scheme of the floating characteristics of the double damping system was designed, and the combined experimental data of Qd and Fd were obtained. The 40 groups of experimental data were extracted, and the relationship between the combination (Qd, Fd) and impact energy and frequency and power were analyzed. The combination (Qd, Fd) with maximum and minimum power was selected to analyze the motion law of an impact piston. The maximum drilling power was obtained at the combination (Qd = 8 L·min−1, Fd = 16.25 kN). The influence factors of the double damping system on impact performance were summarized, and the characteristics of the double damping system under optimal impact performance were obtained.