International Journal of Mining & Geo-Engineering
Volume:56 Issue: 2, Spring 2022

Determining strength and deformation of jointed rock masses is an inevitable part of geomechanical projects. Strength and deformability of a rock mass with stochastic joint sets is conceivably anisotropic and is mainly controlled by joints mechanical and geometrical properties. In this paper, strength and deformation behavior of jointed rock masses has been evaluated at Tazareh coal mine, Iran. Field mappings through scanline method have been used to collect joints spatial features on rock surfaces. A statistical evaluation has been carried out on field data using Dips software. Then, geomechanical properties of intact blocks have been measured conducting uniaxial compressive strength test. Finally, the rock mass is modelled using 3DEC, and its behavior is analyzed in some cases with different loading directions and block sizes to obtain representative elementary volume (REV) based on strength and deformation, respectively.

Reserve evaluation is a very difficult and complex process. The most important and yet most challenging part of this process is grade estimation. Its difficulty derived from challenges in obtaining required data from the deposit by drilling boreholes, which is a very time consuming and costly act itself. Classic methods which are used to model the deposit are based on some preliminary assumptions about reserve continuity and grade spatial distribution which are not true about all kind of reserves. In this paper, a multilayer perceptron (MLP) artificial neural network (ANN) is applied to solve the problem of ore grade estimation of highly sparse data from zarshouran gold deposit in Iran. The network is trained using four metaheuristic algorithms in separate stages for each algorithm. These algorithms are artificial bee colony (ABC), genetic algorithm (GA), imperialist competitive algorithm (ICA) and particle swarm optimization (PSO). The accuracy of predictions obtained from each algorithm in each stage of experiments were compared with real gold grade values. We used unskillful value to check the accuracy and stability of each network. Results showed that the network trained with ABC algorithm outperforms other networks that trained with other algorithms in all stages having least unskillful value of 13.91 for validation data. Therefore, it can be more suitable for solving the problem of predicting ore grade values using highly sparse data.

Chemical compounds of soils can remarkably affect the stability of the excavation wall. This is highlighted in soils with fine grain materials. Inter-particle chemical cementation (IPCC) increases soil cohesion and, in turn, provides more stable excavations. This study evaluates the effect of soil chemical compounds on the stability of an excavation excavated in the west of Iran, Kermanshah city. It adopted the 2D finite element method (2DFEM) to evaluate the physical stability of the excavation. In the excavation examined here, the maximum depth that could be excavated with no need for support was 36m. In contrast, according to simulation results, the maximum possible depth for an excavation with soil cohesion of 6kPa and friction angle of 33 degrees, derived from direct shear test, is 6m. As per the results of this investigation, iron oxide, aluminum oxide, and silicon oxide increase the soil's cohesion containing the clay mineral montmorillonite by 10 folds and increase its shear strength by 127%.

The aim of this experimental study is to investigate the effects of the addition of mine wastes and bone ash on some geotechnical properties of soft soil. The properties investigated include modified proctor compaction characteristics, California bearing ratio (CBR), uniaxial compression strength (UCS), internal friction angle (ϕ), maximum high density and maximum moisture contents of a characteristic soft soil. The study evaluated the ability of self-cementing properties of iron ore tailings, steel slag and coal ash which are by-product wastes from mining activities and bone ash at low proportion replacements to soft soil to improve the bearing capacity of the soil. The use of these calcium rich waste materials to stabilise and improve the bearing capacity of soil is a cost efficient and environmentally friendly disposal method of handling wastes. The candidate wastes, coal ash, bone ash, iron ore tailing, and steel slag were used to stabilise the soil separately at 0.5%, 1%, 1.5%, 2% and 2.5% replacements with soft soil. Based on performance tests conducted, considerable increase in the soil maximum dry density, compaction, UCS and CBR values were observed at different percentages of the additives. The results show that iron ore tailing is the candidate additive with highest property value of CBR of 11 over the soft soil of 7.5. Iron ore tailings also give maximum dry density and maximum moisture content values of 2500.73Kg/m3 and 22.45% respectively higher than other additives. All the candidate additives show improvement in properties evaluated over the soft soil. Therefore, these mine wastes can be used to enhance the stability of earthy materials of structural foundation such as highways, railways, embankments, reclamation and backfill etc. at low percentage replacements.

Extreme vertex design (EVD) provides an efficient approach to mixture experiment design whereby the factor level possesses multiple dependencies expressed through component constraints formulation. Consequently, the derived experimental points are within the center edges and vertices of the feasible constrained region. EVD was deployed for the modeling of the mechanical properties of the problematic clayey soil-geogrid blends. Geogrids are geosynthetic materials that possess an open mesh-like structure and are mostly used for soil stabilization. The geotextile materials present a geosynthetic and permeable layer to support the soil and foundation by improvement of its stiffness characteristics and at a cheaper cost to procure compared to other construction materials and possess unique lightweight properties with greater strength improvement on the soil layer when used. Minitab 18 and Design Expert statistical software was utilized for the mixture design experiment computation; to fully explore the constrained region of the simplex, I-optimal designs with a special cubic design model were utilized to formulate the mixture component ratios at ten experimental runs. I-optimality and D-optimality of 0.39093 and 1747.474, respectively, were obtained with a G-efficiency of 64.8%. The generated laboratory responses were taken together with the mixture ingredients’ ratio and taken as the system database for the model development. Statistical influence and diagnostics tests carried out on the generated EVD model indicate a good correlation with the experimental results. Graphical and numerical optimizations were incorporated using a desirability function that ranged from 0 to 1, which helped to arrive at the optimal combination of the mixture components. 0.2% of geogrid, 9.8% of water, and 90 % of soil yielded the optimal solution with a response of 41.270kN/m2 and a desirability score of 1.0. The model simulation was further carried out to test the model’s applicability with the results compared with the actual results using student’s t-test and analysis of variance. The statistical results showed a p-value>0.05 which indicates a good correlation.

Chehel Koureh mine project is located 110 km NW of Zahedan in the southeast of Iran. Due to the great depth of ore deposits, the underground exploitation method was chosen. In this research, the geomechanical parameters were obtained using in situ tests and empirical formulas. The non-pillar continuous mining method (NPCM) was selected as the most appropriate method considering the shape of the ore body and rock mass strength conditions. As the rock mass is fractured and has semi-continuum characteristics, the stability analysis of the shape dimensions was carried out using FLAC 3D software. In the proposed method, a cylindrical pillar with a height of 3.8 meters was located above the stope. For the safety of the drilling machine room and stope roof, height accuracy was required. Five different pillar diameters (i.e., 3, 3.2, 3.4, 3.6, and 3.8 m) were analyzed by considering the critical height and plastic zone created around the pillar. For these five diameters, only the pillar with a diameter of 3 meters had a supercritical height. It was observed that for the pillar with a diameter of 3.8 m, no plastic zone was created and the safety factor for this pillar was obtained 1.11. Due to the restrictions for the application of the proposed mining method i.e. NPCM in Iran, the Miami method was considered as the alternative mining method applicable to the Chehel Koureh copper deposit. Then, the suitable dimensions for stope and pillar were determined by the same software. In the Miami method, there were three spans and two pillars at each stope before the recovery of pillars could be undertaken. The pillars with three widths of, i.e., 5, 6, and 8 meters were studied for the stability analysis. The results demonstrated that a plastic zone was not created only around the pillar with a width of 8 meters, and the safety factor for this pillar was obtained to be 1.56.

Discontinuities within the rock mass are present in a wide range of networks. Their characterization and analysis exist with considerable diversity. Prior research appraises the significance of mechanical discontinuities and their effect on geotechnical structures and deficient with integral discontinuities. The variability and uncertainty related to rock mass discontinuity parameters such as spacing, persistence and aperture size cannot be present in a single value; it exhibits variability between specific range values. The use of a statistical method to present the discontinuity parameters provides a basis for Monte Carlo (MC) based stochastic modeling of discontinuity parameters to evaluate the stability of rock mass. The road cut slope of Bukit Merah, Malaysia, was investigated using close-range photogrammetry. Details of high precision rock mass discontinuities (mechanical and integral) parameters such as spacing, persistence and aperture were captured. To evaluate the best fit distribution for discontinuity parameters, Chi-Square test, Modified Kolmogorov Smirnov (K-S) and Anderson-Darling tests were employed. According to the findings, the discontinuity spacing is subjected to a lognormal distribution. In contrast, discontinuity persistence and aperture size followed loglogistic distribution. Furthermore, the Monte Carlo simulation (MCS) is a promising approach for assessing the variability and uncertainty of discontinuity parameter relationships.

Long-term production planning in open-pit mines is a precedence-constraint knapsack problem. A spatial representation of the mining region (called the block-model) is the primary input of mine planning models. One should note that as the number of blocks and periods to be planned increases, the number of decision variables increases. This paper presents a fast yet straightforward algorithm to reduce binary variables in open-pit mine production planning models. The algorithm considers mining capacity, processing capacity, and pit deepening rate to estimate the time span within which a block is mineable. This paper applies the algorithm in 12 different cases. The number of blocks varies from 1000 to 240000, and the mining periods range from 6 to 30 years. According to the results, this algorithm is helpful for problem size reduction.

The growth of mining activities reduces the area covered by natural ecosystems and the value of ecosystem services (ES) provided by them. It is necessary to estimate the impacts of land-use changes on the ES value of the ecosystems located in the areas directly and indirectly influenced by mining activities as well as the cost of environmental damages inflicted on the ecosystems. Green mining makes it possible to develop a suitable and effective mechanism for the policymakers and planners to optimally and sustainably upgrade resources utilization. Estimating the cost of the environmental damage of mining activities would effectively preserve ES values and prevent the degradation of ecosystems. It is also an efficient approach in making effective decisions and plans for the restoration of mines. The recent study is the first research to investigate the relationship between mining activities and their impact on reducing/losing the value of ecosystem services by offering a comprehensive and specific framework. The total estimated cost of environmental damages inflicted on ecosystem services influenced by the mining activities in the Sungun Copper Mine was estimated at Int $ 7543232 (1734943 million IRR). This research aimed to develop a comprehensive framework for the stages involved in estimating the changes and losses inflicted on the values of ecosystem services provided by the ecosystems within the scope of direct and indirect effects of mining activities. This framework can help policymakers, stakeholders, and land use planners at regional and national levels preserve ecosystem services and make sustainability plans for the mining regions.

Undoubtedly, determining the threshold of anomalies and separating geochemical anomalies from background is one of the most important stages of minerals exploration. In the discussion of the separation of geochemical anomalies from background, there are different methods that structural methods have shown much greater efficiency than nonstructural methods. Among structural methods (methods that consider the position and location of samples), U-statistic and fractal methods have a special place. In this study, by using the algorithm of the abovementioned methods and combining them, a new method as U values fractal model (U-N and U-A) is introduced for the first time. Then, the proposed method is employed to determine the boundaries of background and anomalous populations (about the gold (Au) and arsenic (As) elements in Susanvar district). Results show that in U-N and U-A fractal models, the first fracture boundary is much clearer and more accurate than previous fractal models (C-N and C-A) in the same condition. In U-N model, due to the nature of the U method algorithm, there is a discontinuity as the exact threshold between background and anomaly that in U-A model, this does not exist due to the homogenization of U values. In this method, the exact threshold between background and anomaly is determined by the U-statistic method and by its combination with the fractal method, in each population, sub-populations are identified more accurately and simply than the concentration fractal model. Finally, a lithogeochemical map of the study area is provided for Au and As which has been prepared using U-N and U-A fractal methods. In these maps (especially the prepared maps by U-A model), the delineated Au-As mineralization is closely associated with the defined Au ore indications in the study area.

This paper evaluates the variation and relationship of Brazilian tensile strength and fracture characteristics of sandstone under different weathering grades. Brazilian tensile strength experiments were performed on Fresh and slightly weathered sandstone specimens using an automated compression measuring machine UTC-5431. Image-based fracture characterization was carried out using public domain open-source software ImageJ. Furthermore, SPSS and Microsoft Excel were used to analyze the relationship between Brazilian tensile strength and fracture characteristics. Results demonstrate that sandstone tensile strength decreases as fracture maximum deviation distance (FMDD), fracture deviation area (FDA) and fracture length (FL), and weathering grades increases. Additionally, fracture deviation distance, fracture deviation area, and fracture length increase with an increase in weathering grade. The correlation results revealed that the tensile strength of fresh sandstone has a strong relationship with FMDD, FDA, and FL. Whereas, in the case of slightly weathered sandstone, BTS has a strong correlation with FMDD and FDA. Whereas multiple regression analysis shows that BTS has a strong relationship with fracture characteristics. Therefore, estimating the fracture characteristics of sandstone using its tensile strength is convenient, however, the sensitivity of sandstone strength properties and fracture characteristics to weathering must be acknowledged.

Geotechnical engineering applications comprises high temperature such as deep geological disposal of nuclear waste, exploitation of geothermal process, etc. High temperature and thermal environments can affect the mechanical properties of building materials used in civil engineering (concrete, building rock, steel, etc.). The constant action of regular thermal changes in situations of excess temperature is the main source of the alteration of marble in monumental and artistic buildings. In this study, the effect of both the specimen size and temperature on the physio-mechanical characteristics of dolomitic marble has been investigated. The temperature range selected was 20-600°C. It was observed that the color of samples changes with temperature rise. The Uniaxial compression strength (UCS), P-wave velocity (Vp), and Young’s modulus decreased with temperature rise. While the peak strain increases with temperature. The UCS and the peak strain showed a decreasing trend at the high diameter specimens. In the case of 43mm diameter specimens the peak stress reduced from 60MPa-26MPa with a rise in temperature from 20-600°C. While at the same temperature range the peak strain was observed as 1.7-3.3 and Young’s modulus was 34-8GPa. For 75mm diameter, the peak stress is reduced to 17MPa when the temperature rises to 600°C and Young’s modulus decreased to 4GPa while the peak strain increased from 2.3 to 3.9. The pulse velocity decreased from 2.75 km/s to 0.8km/ and the porosity value increased from 0.9 to 1.5%.