International Journal of Mining & Geo-Engineering
Volume:56 Issue: 3, Summer 2022

A detailed study into engineering mechanics of rocks is very crucial due to their nature and widespread applications as well as the fact that they are encountered in daily activities of practising engineers and designs and constructions are made in and/or on them. A comprehensive investigations have been made into influence of fabric and mineralogy on the behaviour of dolomitic rock by conducting series of laboratory tests. Also, extensive analyses have been made to determine suitable indices to predict parameters needed for engineering design and construction particularly at the beginning of projects when data may not be readily available. The parameters considered were porosity, rebound hardness, strength and modulus and the indices considered were fabric (particle shape, packing density) and mineralogical indices (quartz and dolomite). The rock is characterised by low porosity (0.64-1.50%), medium durability (65.4-73.3%), heterogeneous and sub-angular particles (0.60-0.77) with very few voids. The mineralogy comprises quartz (0-64%), dolomite (10-87%) and other minerals. The strength varies from low to relatively high strength (12-43 MPa). The variability of parameters and indices of dolomitic rock is low except for quartz. Although mineralogy has little influence on porosity of samples, fabric and mineralogy have significant influence on mechanics of dolomitic rock. It is very interesting to observe that fabric and mineralogical indices can be used to predict physical and mechanical parameters of dolomitic rock based on significant regression statistics. The fabric and mineralogical indices are suitable and are recommended for practitioners working on the materials.

Inverse modeling is one of the useful solutions to create a logical model with relationships between observed and measured values. In geophysical and subsurface investigations such as cavities or mineral explorations, solving inverse problems using problem physics in a partial differential equation (PDE) system is very important. In this research, COMSOL multiphysics’ optimization interface, combined with a PDE or physics interface, was used to solve inverse-modeling problems. Also, a framework is presented to solve undetermined inverse problems using COMSOL multiphysics’ optimization. COMSOL multiphysics does not include a gravity calculation module. However, since Poisson’s equation governs gravity and electrostatics, a gravity model can be created in the electrostatics module by changing the electrical permittivity value. We present a general adjoint state formulation that may be used in this framework and allows for faster calculation of sensitivity matrices in a variety of commonly encountered underdetermined problems. First of all, 2D inversion of gravity data has been run and validated in COMSOL multiphysics software using one synthetic model and synthetic data in a forward modeling process. Afterward, using real gravity data surveyed along a cross-section of the sinkholes in the NW of Abarkuh, the lateral structure and subsurface cavities were estimated. The inverted gravitational acceleration values, then cross-correlated with observed gravity data and available surface pieces of evidence such as sinkholes and circular structures. The results indicated that our COMSOL-based routines for the solution of PDE-based inverse problems using adjoint states, while high in computational speed, can be used in modeling a wide range of physical systems governed by the partial differential equation laws and also can accurately discriminate between low-density contrast regions and background.

Water is one of the important parameters in flotation and represents 80–85% of the volume of mineral pulp processed in flotation circuits. In our recent studies revealed was found that sulphide minerals generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding but effect of type of water on the oxidation of pulp components and hence in deteriorating the concentrate grade and recovery in flotation has not been explored yet. In this study, effect of two types of water on formation of H2O2 as an oxidizing agent stronger than oxygen was investigated. process water is water that is used for a flotation processes in Bama Company. It was shown that process water generated 482 µM H2O2 but deionized water generated 16 µM. The result shows recovery of chalcopyrite in pH 6 is 60% and 40% in process water and deionized water respectively. Also, recovery of galena in pH 6 is 30% and 20% in process water and deionized water respectively.

This paper presents a new approach to quantify the rate of the disturbances within the phosphate series in an area of 50 hectares located in Sidi Chennane deposit, Ouled Abdoun, Morocco. The proposed approach consists in applying the mass-radius fractal method on the geo-electrical images to estimate the fractal dimension FD as an index of the rate of the disturbances. The result of this study shows a strong correlation between the measured disturbed surfaces displayed on the studied geo-electrical images and their corresponding fractal dimensions. The calculated FD’s values were found in the range of 2.081 to 2.719 and correspond to the range of the disturbances rates of 4.1 % to 17.7 % respectively. Therefore, the highest fractal dimension values reveal a high rate of disturbances and vice-versa. This analysis has confirmed that the fractal dimension may offers significant implications to distinguishing between the phosphate deposit at high disturbances rate and the deposit at low disturbances rate. This may lead to important implications for the mining engineers to obtain an accurate phosphate reserve estimate and make the best exploration and exploitation planning in Sidi Chennane mine.

A high-resolution aeromagnetic survey was conducted in the Kirk Range region in southern Malawi with the goal of obtaining comprehensive geological and structural information. This newly collected data was analyzed and interpreted in order to gain a better understanding of the mode of occurrence of gold mineralization and related structural characteristics. To un-derstand the distribution of magnetic sources, many analytic approaches were applied to the aeromagnetic data, including reduction to the pole, Euler deconvolution, Spectrum analysis, Tilt and Vertical Derivatives filtering. Spectral analysis and Euler deconvolution were used to determine the depth of magnetic sources. The study reveals that the studied region is charac-terized by NE-SW and roughly E-W direction structures and that the gold occurrence is re-stricted within these structures, implying that mineralization is structurally controlled. These structures are found at depths of 200-1000 meters, according to Euler solutions produced from this work. Based on the calculated depths the structures controlling mineralization, in the Kirk Range are interpreted to occur at a depth range of 200 to 1000m and the structures trend in the NE-SW and E-W direction. However current gold mining is taking place at a fairly shallow depth of less than 50m and no gold mine has gone deeper than that. The struc-tural pattern and depth extent estimations show that gold mineralization in the Kirk range is expected to continue up to 1000 meters because the majority of the structures controlling mineralization in the region are located within that depth range. It is therefore recommended that future exploration should go deeper to a depth of about 200-1000 meters or more focus-ing on these NE-SW and E-W structures, because it is expected that at that depth range more mineralization should be intercepted.

Removal of copper from synthesized and real dilute sulfuric acid solutions was investigated. Effects of copper, iron concentrations and applied potential were studied. In pure copper solutions, increasing the Cu2+ concentration from 1000 to 5000 mg.L-1 increased the copper recovery from about 30-300% depending on the cathode potential and decreased the energy consumption by about 30%. Also, with increasing the acid concentration from 15 to 50 g.L-1 an about 25% increase in copper recovery and a 30% decrease in energy consumption were observed. The addition of Fe2+ to the solution improved the ionic conductivity and so that the copper recovery. The specified energy consumption for the real leaching solutions increased to 31-47 KWh.kg-1. The diffusion coefficients for several synthesized and real copper electrowinning electrolytes were determined. Moreover, the maximum value of the diffusion coefficient (D) was obtained 2.27*10-4 cm2.s-1 for the pure copper solution at a concentration of 1000 mg.L-1 Cu2+ which was higher than impure and real solutions.

The sheet piles are used below hydraulic structures to reduce seepage flow rate and hydraulic gradient at the outlet of such structures rested on permeable foundations. Up to now, for analysis of seepage under hydraulic structures much research work has been carried out in the form of numerical models. However, less field and laboratory works have been performed to study and compare boiling phenomena for evaluating of the numerical models. By simulating an experimental model of a sheet pile inserted in a sand foundation by computer code FLAC based on the finite difference method, the soil behavior mechanism flow has been investigated under seepage effect. The results indicate that computer code FLAC underestimated uplift pressures compared to the experimental data. In order to study the boiling, the soil treatment analyzed at the most critical condition as well. The numerical model presented in computer code FLAC, is properly able to simulate the soil and foundation behavior. Comparing the results obtained from numerical model with experimental data also confirms well, because this model predicts the boiling observations with reasonable accuracy and it was possible to predict heaving mechanism based on the stress analysis before performing the plan.

In this study, the evolutionary polynomial regression (EPR) method has been employed to develop simple models with reasonable accuracy to predict the compressive strength and Young's modulus of the lime/cement stabilized clayey subgrade soil. For this purpose, the different specimens with the various cement and lime contents, at three moisture contents (dry side, wet side, and optimum moisture content) were fabricated and were cured for 7, 14, 21, 28 and, 60 days to conduct the unconfined compressive strength (UCS) test. According to the test results, a dataset consisting of 75 records for each additive was prepared. Results of this study show that the R2 value of the developed model for predicting UCS of cement-stabilized clay soil is equal to 0.96 and 0.95 for training and testing sets, respectively. These two values for lime-stabilized soil are 0.91 and 0.87, respectively. Moreover, the R2 for predicting Young's modulus of cement-stabilized clay soil is equal to 0.90 and 0.89 for training and testing set, respectively. These two values for predicting Young's modulus of lime-stabilized soil are 0.88 and 0.94, respectively. The sensitivity analysis showed that for the Portland cement stabilized clayey subgrade, the percentage of the Portland cement and moisture content are the most significant parameters for predicting the UCS and Young's modulus, respectively. In contrast, for the lime-stabilized clayey subgrade soil, the most important parameters are the moisture content and the UCS, respectively.

This paper presents results of laboratory tests to explicate the mechanism of the Poly Vinyl Acetate (PVA) and hydrated lime on the engineering properties of the treated soil. Soil improvement is a time and cost saving method that enables unsatisfactory in-situ materials to obtaining higher strength, obviating the need for costly excavation and replacement with suitable material. Laboratory test, including consistency limits, compaction, unconfined compressive strength (UCS), and direct shear tests were carried out on treated soils. The results show that the addition of 4% PVA and 6% lime can improve soil properties, but lime had higher UCS on long period. Moreover, optimum percentage of PVA has a small effect on the cohesion and UCS of treated soil, but its effect on friction angle is significant.

Microwave applications in mining and process metallurgy have been the subject of many studies over the past two decades. This paper reviews the microwave-assisted leaching of copper from high-grade sulfide concentrate of the Sarcheshmeh copper complex. Response surface methodology (RSM) is used to optimize the leaching process. In this research, leaching experiments were carried out in a multi-mode cavity, and times in the presence of varying concentrations of H2O2 with microwave assistance after the leaching process parameters including type and concentration of the oxidizing agent, NaCl concentration, and leaching temperature, were optimized using Taguchi orthogonal array design method. Conventional leaching experiments were also performed to evaluate the influence of microwave radiation. It has been recognized that microwave technology has great potential to improve the extraction efficiency of metals in terms of both reductions in required leaching time and the recovery of valuable metals. Under the optimized conditions, the leaching efficiencies of copper were 75.3% and 42.5% in 3 hours by microwave assistance and conventional leaching methods, respectively..

Split Hopkinson Pressure Bars (SHPB) test is widely used among the various methods for investigating the dynamic behavior of rocks at high strain rates. Various factors affect the waveform and the results of this test. In this study, the aim was to investigate the effect of geometrical parameters of strikers including the effect of shape, length, and impact cross-section width (ICSW) on the waveform induced in the SHPB test using numerical modeling. For this purpose, in the first stage, the required information including geometrical properties and the required micro-parameters have been collected from two laboratory and numerical modeling studies. Then, the initial model was constructed using the discrete element numerical method (DEM), and its results were compared with laboratory and numerical results. Evaluation of the effect of striker shape demonstrated that SS strikers have induced a semi-sinusoidal wave and CS strikers have induced a quasi-rectangular wave. Among the waveform properties, the wavelength was strongly related to the geometric properties of the strikers in both CS and SS types in a way that was directly related to the striker’s length and inversely related to the ICSW. On the other hand, the maximum amplitude is directly related to the striker’s length and ICSW in both CS and SS types. According to the results, the use of SS strikers is more appropriate according to the waveform, and its geometric properties can be determined according to the problem requirement, using numerical modeling results.

At the presence of undesirable geological conditions, including rock masses with high overburden, crushed zones and faults, folds, dikes and other abnormalities, rockburst has become a critical safety problem in Gelas tunnel, a water conveyance tunnel, wherein some sections overlying strata exceed 600 m. The main goal of this study is to determine the possibility of rockburst and its level along the second part of the Gelas tunnel. In order to study the mechanisms of rockburst occurrence in Gelas tunnel, measurements of in situ stress, geological investigation, uniaxial compression tests, and analytical approaches are carried. So, in this study, some analytical approaches, including Linear elastic index, Tangential stresses criterion, Brittleness coefficient of rocks, and method of stresses are used to predict rockburst in 17 sections of the tunnel path. The average result shows that all the selected sections in the tunnel path have the potential of occurring rockburst at a range of low to moderate. About 65 percent of the sections are exposed to moderate risk of rockburst occurrence; and the remaining 35 percent are exposed to low risk of rockburst occurrence. The comparison between applied methods shows a lack of consensus conformity among them. The brittleness coefficient of rocks method turned out to be as the most conservative approaches for predicting rockburst occurrence since by this approach most of the sections in the tunnel path are susceptible to high risk of rockburst occurrence. According to the average result, fault and Dolomitic zones with high overburden have the highest risk of rockburst occurrence.