International Journal of Mining & Geo-Engineering
Volume:52 Issue: 1, Winter-Spring 2018

The assessment of fragmentation through blasting and therefore subsequent crushing and grinding stages is important in order to control and optimize the mining operation. Prediction of the mean size of fragmented rock by the rock mass characteristics, the blasting geometry, the technical parameters and the explosive properties is an important challenge for the blasting engineers. Some of the effective parameters on rock fragmentation have been investigated in several empirical models. A model for fragmentation in bench blasting was developed using the effective parameters on the existing empirical models, so as to propose a simple applicable model to predict X50. The proposed model was calibrated by nonlinear fits to 35 bench blasts in different sites from Sungun copper mine, Akdaglar quarry and Mrica quarry. In order to validate the proposed model, its results were compared to data obtained from six blast sites in Chadormalu iron ore mine and one in Porgera gold mine. The results indicated a small variance in X50 which is calculated by the proposed model, through the image processing approach. The Comparison of the powers between the proposed and the Kuz-Ram models showed that the specific explosive energy and the powder factor are almost the same. The advantage of the proposed model rather than the Kuz-Ram model is specific explosive energy, since this parameter includes the powder factor and the weight strength of explosive. Also a sensitivity analysis was carried out based on artificial neural network. The results showed that the burden and the specific explosive energy were the most effective parameters in the proposed model.

The expansion of the settlement trough is an important factor in the risk assessment of the tunneling induced settlement. The increase of settlement trough requires buildings to be included in the impact zone, which causes damages. This paper conducts estimation of the settlement trough width (STW) using empirical approaches, field measurement data and numerical solutions. The credibility of the numerical results is affected by accuracy of the input data such as geotechnical parameters (E, c, and φ). Therefore, an approach in which 3D finite element modeling (FEM) and a Taguchi’s experimental design are combined to estimate the geotechnical parameters (E, c, and φ), is used. The field settlement measurements are used to validate the numerical modeling results. The results indicate that Taguchi’s (DOE) method is an effective approach to estimate the geotechnical parameters. In addition, numerical modeling provides a wider settlement trough than the empirical methods and instrumentation data. However, maximum settlement in numerical modeling has the minimum deviation of the filed settlement data. There is a good agreement between empirical approaches and field settlement data to estimate i-value and STW parameter. The results of numerical simulation overestimated the settlement trough width, which causes more buildings to be included in the tunnel impact zone. It demands more extensive study to assess the tunneling induced building damage, which is more conservative.

Rock structures are subjected to cyclic tension-compression loading due to a blasting, earthquake, traffic and injection-production in underground storage case. Therefore study the fatigue behavior of rock samples under this type of loading is required. In this study, the accumulated fatigue damage for a Green Onyx rock sample which consisted of only one mineral composition with two-step high-low sequences of loading levels was investigated under completely reversed loading condition. New apparatus based on the R.R. Moore fatigue test machine is designed to assess this type of loading. A comparison between the predicted behavior of Linear Damage Rule and experimental data was conducted and a new damage model was proposed based on the experimental observation. The results showed a good agreement between the proposed damage model and experimental data.

Earth slopes stabilization is one of the main issues focused on by are in geotechnical engineer. Use of stone columns is one of approaches well increasing the safety factor of earth slopes of the soil embankments; furthermore, it is economical besides the simplicity and ease it exhibits in implementation. . The present paper aims at an experimental comparison of the Ordinary Stone Column (OSC) and Rigid Stone Column (RSC) behaviors in sandy slope. These tasks were carried out by constructing embankment sandy slope and, then, saturating it with rain and, finally, loading increment. The experimental results, obtained in laboratory modeling through taking advantage of three-dimensional finite difference method, have also been verified. Laboratory modeling and numerical analyses results have shown that the existence of rigid stone column in the middle of slope (as the optimal placement location) enhances sandy slope stability up to 1.36 times compared with slope reinforced by ordinary stone columns.

The escalating construction industry has led to a drastic increase in the dimension stone demand in the construction, mining and industry sectors. Assessment and investigation of mining projects and stone processing plants such as sawing machines is necessary to manage and respond to the sawing performance; hence, the soft computing techniques were considered as a challenging task due to stochastic optimization of this issue and to handle complex optimization problems. In this study, Particle Swarm Optimization (PSO) and Artificial Bee Colony (ABC) algorithms as soft computing techniques were used to classify the dimension stones based on physical and mechanical properties and ampere consumption. For this purpose, varieties of dimension stones from 12 quarries located in Iran were investigated. Studied dimension stones were classified into two and three separate clusters using the optimization clustering techniques. The results showed that the applied soft computing technique makes it possible to evaluate the performance of sawing machines in different complex conditions and uncertain systems.

The behaviour of the stabilized lateritic soil obtained from Amaoba, Nigeria treated with green crude oil was statistically studied using analysis of variance with interaction, Kruskal-Wallis test, and expected mean square methods to validate the effect of the additive on the strength properties of the stabilized soil. First a preliminary test was conducted on the soil to classify the soil as an A-2-6 soil according to the AASHTO classification system. The soil was treated with varying percentages of crude oil; 0, 2, 4, and 6% by weight of the soil. The results obtained showed that the GCO improved the strength properties of the treated soil. Finally the prediction model was used to validate the reaction that brought about strength gain, flocculation, carbonation, cation exchange and densification of the stabilized soil matrix. The three analyses of variance approaches agreed on the hypotheses tests conducted, which rejected the null hypotheses and showed that, to achieve soil stabilization, there must be interaction between the additives and the treated lateritic soil and different percentage by weight of treatment affect the treated soil in different ways.

Kerman and its surrounding towns consist of a flat alluvial plain of fine silt and clay materials. In morphological aspects, these sediments have a very gentle slope with the main infrastructure of the city build on them. Generally, the structure of undisturbed soils is developed over time due to the influence of environmental factors. Geological factors in Kerman fine-grained alluviums have caused the formation of some structures after their deposition. In this research, in order to investigate soil structure and determine the collapsibility index, 40 samples were collected from different parts of the city. Next, the engineering properties of Kerman’s soil (e.g., mineralogy and collapsibility), development of soil structure, and the sensitivity of soil structure were studied. To determine sensitivity and structural coefficient of these soils, Schmertmann’s criteria (1969) and Liu and Carter’s model (2000) were applied, respectively. Moreover, scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDS) method were used to study Kerman deposits. Mineralogy results of Kerman plain soils reveal that there are minerals such as illite, chlorite, smectite, and calcite in these deposits. The SEM images confirmed the consolidated and compressed structure of soil grains in most of the samples. Furthermore, other results show that soils of Kerman are often compressed and over-consolidated. Collapsibility index shows a quite direct relationship with structure development, as collapsibility is low in the samples with low destructuring coefficient while it is high in the samples that have a structure.

Due to uncertain nature of grade in ore deposits, considering uncertainty is inevitable in geological modelling of resources and mine planning. In other words, uncertainty in grade of mineralized materials, is one of the most significant parameters need attention in mine planning. In this paper, a comparative procedure utilizing Sequential Gaussian Simulation (SGS) and traditional Ordinary Kriging (OK) was applied in an iron ore mine, and the influence of ore grade uncertainty in mine planning was investigated. It was observed that grade distribution, resulted from the SGS is almost identical to that of the real exploration data as compared to the OK method. Also it is emphasized that uncertainties including ore grade of deposit would significantly affect the technical and financial aspects of plans. Comparison shows that the simulation-based ultimate pits exhibits less risk in deviating from quantity and quality targets than traditional approach based on a single orebody model obtained by OK method. Using SGS method, there was an increase in the value of net present value of mine plans.

This paper aims to study the mechanical behaviour and failure mechanism of intact rocks under different loading conditions using the grain based model implemented in the universal distinct element code (UDEC). The grain based numerical model is a powerful tool to investigate complicated micro-structural mechanical behaviour of rocks. In the UDEC grain based model, the intact material is simulated as assemblies of a number of polygonal blocks bonded together at their contact areas. To investigate the ability of such a numerical framework, uniaxial and triaxial compression tests as well as direct tensile test were simulated in UDEC and then the results were compared with the laboratory experiments undertaken on Hawkesbury sandstone. There was a good agreement between the experimental and numerical under different loading conditions. In order to investigate the effect of micro-properties of the grain based model, blocks and contacts, on the laboratory scale intact rocks, a set of parametric study was undertaken. The results from this analysis confirmed that the block size is an intrinsic characteristic of a model which has significant effects on the mechanical behaviour of the numerical models. Also, it was concluded that the cohesion and friction angle of contact surfaces control both uniaxial and triaxial compressive strengths. Finally, it was found that in the triaxial compression test, as the applied confining pressure increases, the effect of contact cohesion on the strength decreases while the effect of friction angle increases.

The impact of blast-driven shocks on the safety and stability of the underground coal mines has been well established. The seismic imperfections resulting from blasting depend on the total explosive energy released during blasting and the closeness of the development tunnel face to the stope face. Also, the quality of the rock mass wherein the whole stope face is located might pose considerable effects on the damages from blasting operations. Peak particle velocity is the main criteria for the evaluation of the damage caused by blast vibrations. Twenty nine logs were recorded of three indicators, namely the longitudinal, transverse and vertical, assessed in 29 blasting in Alborz-e-Sharghi underground coal mine and twenty sets of data extracted thereof was subjected to a series of statistical analyses. The nine remaining data were applied in validating the relations proposed herein. The present study analyses and evaluates the common equations used in predicting the ground vibrations. The results of the analyses indicated that the vibrations’ prediction scale, based on the cube root of the amount of the charge applied, is a better predictor of the vibrations in this underground mine. Studies have demonstrated that the scaled distance based on the square or cubic root of the delay charge mass might not be very appropriate for the prediction of PPV (peak particle velocity) in undersurface situations. Accordingly, the present study performs an alternative analysis based on multivariate fitness estimation. In the end, a PPV equation with an appropriate correlation coefficient has been suggested for predicting the ground vibrations in this study area.

Coal quality-tonnage curves are helpful tools in optimum mine planning and can be estimated using geostatistical simulation methods. In the presence of spatially cross-correlated variables, traditional co-simulation methods are impractical and time consuming. This paper investigates a factor simulation approach based on minimization of spatial cross-correlations with the objective of modeling spatial relations of coal quality data and estimating quality-tonnage curves in a part of the Ömerler sector of Tunçbilek coalfield (Turkey). Data come from core samples analyzed for lower calorific value, ash content and moisture content. Prior to simulation, composite data and coal seam are unfolded and the composites are also de-trended. The simulations of the original data are obtained by adding the trend values to the simulated residuals and transforming the unfolded coordinates into the original ones. 100 realizations of the coal attributes are jointly generated by Minimum Spatial Cross-correlation (MSC) simulation method. The MSC-simulations are compared to the results of a widely used joint simulation method based on the minimum/maximum autocorrelation factors (MAF) technique. The comparison shows advantage of the new proposed method over the MAF technique. MSC-simulations reproduce the original data well on the basis of correlation coefficient, cumulative histograms and auto / cross-variograms. This suggests that the MSC-simulation method can be used in simulation of spatially cross correlated coal data. Quality-tonnage curve for each realization is calculated and uncertainty associated with tonnage is assessed by using a 95% confidence interval. The assessments show that the tonnage uncertainty depends on the cutoff.

The lining structure of Tunnel Boring Machine (TBM) excavated tunnels is composed of series of precast Reinforced Concrete (RC) pieces which are called segment. At the present paper, a novel method is introduced for seismic retrofitting of segmental tunnels located at active fault zones in rock environment with case study of Amirkabir dam to Tehran water transfer tunnel (Karadj tunnel). The main design concept in this method is based on stiffness degradation of the tunnel structure intersecting tunnel with fault central zone. Even the strongest structures are not capable to undergo displacement of faults and will fail; so, the stiffness degradation and providing life safety operational limit is the logical solution. This phenomenon is developed due to creation of sequential joints in segments intersecting tunnel with fault central zone; so, it is called sequential joints method. At this method, a joint is considered between each or multiple rings and using this method, the tunnel structure is synchronized with tunnel displacements during fault displacement process and the global failure of the tunnel structure is avoided. This method is currently applied in second part of Karadj water transfer tunnel (Part K”-BR).