سید محمداسماعیل جلالی

The Cased, Cemented, and Perforated (CCP) completion method is considered one of the superior well completion methods in sand-prone reservoirs due to its execution safety and cost-effectiveness compared to alternative techniques. In the design of perforation configurations, the number of shots aligns with the requisite hydrocarbon production volume. Consequently, the optimization of the phase angle (phasing) emerges as a critical design parameter, typically deployed to forestall overlap within the impacted zones surrounding neighboring perforations and curtail their interaction. In light of the absence of constraints and the ease of establishing a single helical perforation pattern compared to alternatives, this study is dedicated to exploring the optimal phase angles within this pattern using a pythonic brute-force search approach. Moreover, emphasis is placed on achieving the minimum spacing between adjacent perforations, and the analysis is geared towards identifying the most optimal phase angles for 6, 9, and 12 shots per foot across three common wellbore diameters. Innovations of this study include the consideration of more than three consecutive wraps of perforations in determining the optimal phasing, as well as the simultaneous impact of perforation stability and uniform flow distribution around the wellbore in reducing the likelihood of sand production. The uniform distribution of perforations has been achieved by introducing a parameter known as the Equilateral Likeness Score (ELS), where its minimum value signifies the most uniform arrangement of adjacent perforations. The optimal phasing angles are determined by drawing inspiration from two distinct perspectives: maximizing the spacing between adjacent perforations and achieving the highest possible phasing values. A comparative analysis of the outcomes derived from the presented theory and existing ones underscores the potential for significant variations in the determined phasing values for certain shot densities. Ultimately, the optimal phase angles for the aforementioned shot densities are projected as 127, 130, and 97 degrees for a 41/8-inch wellbore, 130, 97, and 143 degrees for a 61/8-inch wellbore, and 97, 143, and 77 degrees for an 81/2-inch wellbore.

Iran is considered one of the countries with a relative advantage in the field of mining and related industries due to its important mineral resources and reserves. This issue increases the importance and priority of development programs in the mining and mineral industries sector. Copper, after steel, ranks second among the major metals in terms of value-added production in the world. Iran, with a reserve of about 34 million tons of copper, owns 4% of the world's copper reserves. This article examines the analytical and comparative analysis of copper industry development programs in Iran and India. Although both countries have started their own development programs in the copper industry almost simultaneously, India was ranked among the top economic powers in Asia in 2018 compared to Iran. On the other hand, with some economic growth indicators surpassing China, some analysts believe that this trend may continue and India may achieve growth similar to China and even replace it. On this basis, India’s strategic plans in the field of copper can greatly help in formulating strategic plans in Iran’s copper industry. According to studies conducted in Iran, the most important challenges in the copper industry include increasing the amount of government salaries and export duties, non-entry of mining and industrial machinery, round-the-clock laws, and fluctuations in exchange rates and inflation. This research has examined the damage and analysis of the strengths and weaknesses of Iran’s copper industry program, reviewed the current situation and copper industry development programs, compared it with India, and addressed the challenges ahead. Finally, solutions have been proposed for the development of this important industry.

Accurate simulation of geometrical properties of fractures is an important goal in rock engineering. One of the most capable methods for simulating the random nature of geometrical properties of fractures is Discrete Fracture Network (DFN) random modelling, which presents the heterogeneous nature of fractured rock mass with statistically defined geometrical properties. Up to now, all properties of fractures such as location, shape, orientation, size (persistence), spacing, and opening of joints have been simulated and applied in 3D DFN modelling. In this research, a statistical solution based on Kernel’s non-parametric distribution is used for simulating roughness. Through this method, even those geometric properties of fractures which do not have their own specific distribution functions can be simulated. After simulating the roughness value, the roughness geometry should also be simulated in a way that evokes the roughness value. Therefore, in order to simulate the surface of fractures in this research, the DRS method is applied in 2D and then, developed into 3D. At the end, simulation of discontinuity’s roughness is added as a separate package to DFN-FRAC3D computer program. DFN-FRAC3D computer program, as one of the most capable tools in this field, is able to develop a 3D fracture network block model by using the surveyed data and then simulating geometrical properties of the fracture; thus, by applying the results of this research in this compute software, all geometrical properties of fractures can be simulated. Finally, in order to explain the results of this research, outcomes of DFN-FRAC3D computer program for both with and without applying the roughness property on DFN are compared.

Due to the significance of the sand production (SP) issue in sandstone hydrocarbon reservoirs, the main objective of this study is to evaluate the Asmari formation layers along well No. 469 in the Ahwaz hydrocarbon field in terms of SP causes and its potential capacity to provide suitable solutions for its reduction from a geomechanical perspective. The evaluation was carried out using the Techlog software. The required parameters for constructing a one-dimensional geomechanical reservoir model were estimated from available data. The Mohr-Coulomb failure criterion was adopted considering the scale effect for perforated cavities under non-hydrostatic stress conditions. After constructing the one-dimensional model, the Critical DrawDown Pressure (CDDP) curve was plotted for both open hole and perforation completions, and the susceptible SP zones were identified. The M2 layer was selected as one of the most susceptible zones for SP sensitivity analysis due to its low strength, porosity, and permeability compared to other layers. The sensitivity analysis was conducted based on well geometry, formation rock properties, field stress conditions, and perforated cavity characteristics. The analysis was performed at depths of 2822 and 2837 meters in the open hole and the perforation completions, respectively, with a dominant sand diameter of 200 microns in the potential SP zone. The Critical Bottom Hole Pressure (CBHP) and the Critical Reservoir Pressure (CRP) were estimated to be 1898 and 2735 pounds per square inch, respectively, in the maximum horizontal stress direction with a 0.4-inch perforation diameter and 861 and 2115 pounds per square inch, respectively, in the direction perpendicular to the maximum horizontal stress direction with a 0.3-inch perforation diameter. By defining and determining Transitional Deviation Angle (TDA), Minimum Safe Deviation Angle (MSDA), and Critical Perforation Orientation Angle (CPOA) based on sensitivity analyses, a novel design approach for perforation operations in sand-prone reservoirs has been introduced.

Having rich mineral reservoirs, Iran has great potentials for developing this field, especially in copper mines. Mining in Iran has great potentials for helping economy and creating jobs. Studying and solving the problems of contractors and making necessary preparations for them in order to enter the mining industry and making investment in this area are of effective factors in actualizing the vast mining potentials in Iran. Existence of large-scale contractors in mining operations is considered not only an inseparable arm of the domestic large-scale mining body, but is also looked upon as the prerequisite for sustainable economic development. In any way, despite the undeniable benefits and necessity of large-scale mining contractors for working in large-scale mines, some strategic problems such as international sanctions, lack of access to quality mining machineries, lack of access to quality spare parts and up-to-date technologies, worn-out transportation, time-consuming process of finding spare parts due to sanction conditions, currency rate fluctuations, changes in stated inflation trend, etc., result in limiting contractors’ activities in the large scale. In this research, in addition to studying the major problems of contractors in large mines of Iran, the most important challenges of large-scale mining contractors, especially in large copper mines are reviewed and support solutions such as making preparations for importing up-to-date and large machineries and spare parts, adaptation of adjustment to inflation rate, making specific price list for mining industry, etc. for the continuity of mining contractors’ operations are presented.

Loading and hauling operations have the highest share of the production costs of open-pit mines. Therefore, in choosing the loading and hauling machines, paying attention to the economic aspects is necessary. For a better understanding of the financial performance of mining machinery, various performance indicators have been proposed by researchers. This research presents a special form of economic performance index, which indicates the ratio of each machine's revenue to its total cost. For this purpose, the cost and revenue of the transport fleet, including dump trucks, mining shovels, and backhoe excavators, were collected for two years (From September 2017 to September 2019) and determined. As the first step, the total cost and the amount of revenue from the operation of each machine then, the Economic Performance Index (EPI) for each of the loading and hauling machines is calculated and compared with each other. The results show that Backhoe excavators perform better than mining shovels. In addition, by examining different trucks from different manufacturers, it was found that C100 series trucks have the best performance among all trucks. Its average economic performance index value for each of those trucks is 2.82.

Despite the development of numerous excavation methods and reinforcement of tunnels, finding a proper method for stabilization of underground structures is a challenging task. The use of pre-reinforcement systems is an appropriate method to improve the status of the ground. In this study, the performance of umbrella system in Alborz tunnel in north of Iran has been investigated. Rock mechanics studies of tunnel running area have shown that parts of this tunnel have unstable capacity due to being located in weak zones. Therefore, the tunneling operation running is not possible in these areas. On this basis, umbrella pre-reinforcement system that can be used for loose and running ground are modeled numerically by Flac3D software. In this research, in addition to investigating the performance of umbrella system, the effect of geometrical parameters such as the angle of placement of pipes relative to the horizon and the distance between the umbrella system pipes was investigated. The criterion of investigating is the displacement occurred at the crown of the tunnel. The results of this study indicate that increasing the angle and decreasing the distance between pipes, cause an increase in stability and by using umbrella system, the vertical displacement of crown of the tunnel has decreased by 70 %.

In this research, the effect of different tunnel depths, has been investigated from both technical and economic perspectives. Then, the optimal depth for the construction of subway tunnels has been determined according to both views. Ground surface settlement with different overburdens is the technical perspective. In this study, the allowable surface settlement limit is considered 25 mm. If the ground surface settlement is more than the allowable limit, It cannot be technically suitable for tunnel excavation. Estimation of tunnel excavation costs as well as construction costs of metro stations, along the second line of the Tabriz subway form the economic perspective of this study, to optimization of depth for subway tunnel. This research has been undertaken to identify and optimization of depth for subway tunnel excavation considering Technical and economic perspective, in the second line of the Tabriz subway as a case study. The Line 2 of Tabriz Metro consists of a double-track tunnel with a total length of 21km and 20 underground stations. The ground of the second line of the Tabriz subway is classified in two modes; The first case is, based on the type of ground and the second case is, based on the amounts of overburdens in the tunnel route. In the first case; The different layers of land along the tunnel route are classified into four general categories. In the second case; Tunnel overburdens are classified into five general categories along the tunnel route based on their height. In this research, FLAC3D V6.00.69 software was used. The amount of ground surface settlement has been investigated in 16 different models. Grounds that have more settlement than the allowable depth limit, cannot be suitable for tunnel excavation. Then, the informations related to the tunnel excavation costs as well as construction costs of metro stations, along the second line of the Tabriz subway have been calculated. Next, the optimal depth is determined from an economic perspective. Depths where the tunnel overburden is less than the diameter of the tunnel, are technically more than the allowable settlement limit, and it is not recommended that the tunnel be excavated in that spatial range of the ground. On the other hand, the investigation of this study showed that with increasing depth of tunnel, the tunnel excavation costs initially decreased, and after that when the tunnel overburdens are more than twice the diameter of the tunnel, it increases again. Also, with the increase of tunnel overburden, the construction costs of metro stations have increased. So that the construction costs of a one-story station is equal to 95 billion tomans. Meanwhile, the construction costs of a four-story station was equal to 250 billion tomans, which is much more than the previous case. Therefore, the optimal depth for the construction of tunnels and stations is when the tunnel has more overburden than the diameter of the tunnel and also less than one and a half times the diameter of the tunnel.

Summary:

One of the important geometric features of rock mass discontinuities is its surface roughness. The discontinuity level has different heights that differentiate each level from the other. In practice, it is not possible to assign a roughness value to each of these levels, so to levels that are similar in height; The same amount of roughness is assigned. In analyzing the problems of stone mechanics related to coercion, it is necessary to choose one of the many levels of discontinuities that have the same amount of roughness. Discontinuity Roughness Simulation (DRS) is a random selection of different levels of surface roughness for a certain amount of surface roughness. In this method, the level of discontinuity is simplified by connecting several pieces together; So that each piece has an unevenness. By simplifying and using different layouts of components that make up the discontinuity surface, the DRS method can produce different levels, the JRC value of which is almost the same.

Several methods have been proposed to measure the roughness feature of rock mass, all of them work based on the elevation of its fracture's measurement. Precise measurements and illustration of roughness values were the subjects of the previous studies.

Methodology and Approaches:

Barton's field method and determination of the maximum distance, a, between fracture and the field survey profile, L, is the foundation of the proposed method here. So fracture's length would be divided into n pieces in which its length is less than L and there exist an asperity with the height of a. By considering a number between 0 and an as the flange's height and a random number in the [0,l] interval as the distance between two adjacent flanges, locus of the fracture's flange points would be determined. The locus of the fracture's atrio points would be determined by measuring the distance between two adjacent flange and atrio points of a fracture which is a number between 0 and two adjacent flanges.

In order to validate and ensure the accuracy of the results obtained from the application of the DRS method, the validity, and reliability of the method have been checked for all possible JRCs. The results of the validity test for different JRCs indicated that the value of the mean percentage of absolute error (MAPE) for different parts of a simulated fracture is always less than 10 percent and this means that if a fracture needs to be simulated using the DRS method in order to produce a roughness value of JRC = 10, the JRC value for all parts of the simulated fractures would a number be between 9 and 11. The reliability of the DRS method for different JRCs has also been investigated. Outcomes showed that the value of MAPE in 100 of repetition of DRS method implementation for a part of the simulated fracture that is randomly determined is less than 6 percent, which is an acceptable value and a confirmation of the accuracy of the DRS method to simulate and produce fracture’s roughness.

Summary:

Almost all of the proposed models of Discrete Fracture Networks (DFN) embedded within rock masses are discontinuities with zero tension strength. While, potential discontinuities and weak surfaces such as rock bridges, veinlet, and schistose surfaces are a candidate for breakage under stress and have also a significant effect on rock mass strength. Simultaneously with geometrical parameters, this geomechanical heterogeneous nature of fractures is crucial for understanding rock mass behavior and characteristics. This paper focuses on the probabilistic effect of potential discontinuity properties on the rock mass strength using Potential Discrete fracture networks (PDFN)-bonded block models (BBM) framework. The cohesive crack model is used to define block contact behavior. A comparison of the results indicates the importance of the proposed model for the assessment of realistic rock mass strength instead of traditional DFN.

Analysis of discrete fracture network (DFN) employing the complex nature of fracture patterns plays an important role in understanding the micro and macromechanical behavior of rock mass. Rock mass behavior analyses have traditionally been undertaken for discontinuity with zero tension strength along DFN to calculate mechanical properties. In point of this view, such methods regardless of geometrical parameters generally assume the same possibility of failure for all fractures in the rock mass. The distribution of the DFN strength parameter in Potential DFN can result in important changes in the strength of rock mass and remains a challenge in rock engineering design. The term of PDFN is used for those fracture network with tension and shear strength. Detailed analysis of the employed PDFN which elaborately highlights the role of the distribution of input strength property of each fracture that controls the real strength of rock mass has been presented in this research.

Methodology and Approaches:

In the BBM-DEM, the Voronoi tessellation scheme is employed and the material is simulated as assemblies of several particles bonded together at their contact areas. In order to define contact law of BBM, a cohesive crack model (CCM) is implemented in the UDEC. The calibration process is carried out to obtain contact properties. DFN is written in c++, in which the probability distribution of cohesion, friction angle, and tension strength is considered. The sensitivities of the rock mass strength calculated using SRM e.g., UDEC-DFN to the variability of the input parameter are investigated. A discussion of results is then made base on a reference simulation performed without a distribution method. 4 different P21 are investigated.

The cohesive crack model is implemented in UDEC to define contact law among generated BBM through the Voronoi tessellation technique. In order to assess the effect of the distribution of mechanical parameters in PDFN on the strength of rock mass, DFN is written and this feature is added. The results indicate the importance of the proposed model for the assessment of realistic rock mass strength in engineering applications.

Improvement of the value chain of mining and mineral industries requires a lot of investment. Considering the current condition of the country, this cannot be achieved just by the public budget. One possibly effective approach in financing is the participation of public and private parties is Public-Private Participation (PPP). In order to apply this method to the mining projects, it is necessary to identify factors effective on success through studying and analyzing other countries' experiences and experts' solutions. In this manuscript, in order to identify and prioritize factors effective on PPP success in mining projects, previous researches and papers were studied, success-factors identified and several questionnaires prepared and were given to the experts in order to prioritize them. Then, the results were ranked using Friedman Test. The results of this research showed that through different factors, "defining the appropriate project" has the highest importance on the success of PPPs. Next important ones are payment mechanisms, proper contracts, appropriate political and social environment and legislating new laws, respectively.

In the conventional mass balance methods, sampling are carried out to determine the metal content, solid percentage and particle size distribution in the paths (branches) and ultimately the corresponding errors are dispersed. In these methods, there is no information about the amount of feed and the grade (or the metal content) at any moment of time for each mineral processing unit (plant equipment). Thus, in this paper, the quantitative and qualitative values of input feed to each of the operating units in the processing paths were probabilistically investigated using stochastic process theory, and consequently the load distribution in these units was estimated. For this purpose, the processing plant was firstly modeled as a directional and balanced graph. In this graph, each node represents an operating unit and each edge displays a path between two units. The weight of each edge also indicates the passing material weight from the node to another node, which is assigned as a random variable at a specified interval. After modeling the process, the obtained graphical model containing random parameters was analyzed using Markov chain theory. Applying the philosophy outlined in this paper, not only the load distribution, but also the presence probability of each particle or mineral in each of the operational units of the processing plant can be predicted. It is also possible to estimate the tonnage in each unit when the plant is shut down and even the necessary steps are provided to discharge them. In this research, Chadormalu iron ore processing line was modeled using method presented and the results were analyzed and thereafter were reported using probabilistic parameters.

Computation of fluid flow in fractured rocks is very important. The rock-mass is consisted of intact rock and fractures. Number and connectivity pattern of the fractures are two key factors controlling the fluid flow in the rock-masses. One of the most accurate methods to model geometrical structure of the rock-masses is discrete fracture network (DFN). Anisotropy and heterogeneity of the rock masses often affects the computations of the flow, therefore, three-dimensional DFN has been more desirable in literatures. Numerical calculation of the fluid flow requires solving a large system of equations which are generated by discretization schemes. Solving these systems are not usually straightforward and it needs more special and complex methods to converge the result. One of the best methods in this regard are Krylov subspaces methods. Evaluation of different Krylov subspaces methods which have been validated in comparison with a direct method and 3DEC modeling, has been considered in this research and the most optimized methods have been determined using a series of sensitivity analyses. Therefore, CG, CR and IOM have been characterized as the most accurate and fastest Krylov subspaces methods. The provided results in this research can be a sufficient guideline for the researchers who want to study the fluid flow in fractured rocks.

Ensuring the stability and integrity of underground gas storage salt caverns is a very complicated subject due to the non-linear and time-dependent behavior of rock salts under complicated thermal and mechanical loading conditions. For this reason, pressure and temperature fluctuations in the caverns and their surrounding strata must be integrated into the analysis and the numerical tools that are used for this purpose. LOCAS, a 2D axisymmetric finite-element code, dedicated to the stability analysis of underground salt spaces, was applied to assess the effects of various operating and geometrical parameters on the cavern behavior. In this paper, we aimed to give an overall assessment of the behavior of the salt caverns used for natural gas storage. In this work, some specific loading scenarios were considered first, followed by thorough parametric and sensitivity analyses to reveal the impacts of the geometrical parameters and operational parameters involved on the behavior of salt caverns using the modern stability criteria. The findings showed that the onset of dilation was more likely to happen within the first cavern life cycle when pressure dropped to the minimum level. As for the potential of tension occurrence in the surrounding rock, this is more likely to happen by increasing the number of operation cycles, especially in the upper one-third of the cavern wall. Finally, it was seen that the cavern depth and minimum cavern internal pressure had even more important influences than the others on the salt cavern behavior.

Gas leakage through the cracks and tracks surrounding Underground Coal Gasification (UCG) is of criteria affecting the feasibility of economic methods of the UCG reactor. In terms of process control and groundwater contamination capacity, the sealing of the UCG reactor is very important. Various factors affect the gas leakage from the UCG reactor. In this paper, the parameters of pressure, temperature and joint characteristics (including opening, length and intensity) as the most important factors affecting gas leakage through rock mass fractures are examined using numerical modeling. For this purpose, The Mazino Tabas coal area is studied as a case study. The DFN-FRAC3D computer program is used to stochastically simulate joints and create an equivalent pipe network. Also, Water Gems software is used for flow analysis. The results are shown that increasing the reactor pressure and increasing the rock mass jointing around the reactor increases the flow rate and the gas leakage. On the other hand, increasing the reactor temperature does not have a significant effect on the output flow rate. Besides, jointing is the most effective factor in fluid leakage through the UCG reactor. Among the geometrical features of the joint, including the intensity, the opening and the length of the joint, the joint intensity factor has been introduced as the most important factor.

Rock fragmentation can show the quality of blasting. Screen analysis can be also a precise method to determine size distribution of blasted rocks, but it is a difficult undertaking and sometimes impossible that is due to  the time consumed and large volume of crushed rocks. Nowadays, digital image processing is used to evaluate the rocks fragmentation due to its acceptable accuracy and speed. In this research, WipFrag and Split Desktop were compared for evaluation of crushed rocks. Case study was focused on fragmented rock in Jajarm limestone mine. At the first, an image was delimited manually in the both software. Then the results were compared with screen analysis, showing that the results of Split Desktop are closer to the screen analysis results. Maximum difference between screen analysis and results of Split Desktop and WipFrag is equal to 3.59% and 11.38%, respectively. Some comparative modes including the delimitation method effect (automatically and manually), the image rotation effect, and the separation of an image into four quarter images and a combination of the results are investigated. Maximum difference between the automatically and manually delimitation by Split Desktop and WipFrag is equal to 1.28% and 3.79%. Maximum difference for the image rotation effect for Split Desktop and WipFrag is equal to 1.96 perc%ent and 8.09% and Maximum difference for the separation of an image effect for Split Desktop and WipFrag is equal to 3.01 percent and 9.58 percent. Consequently, in all modes investigated the Split Desktop shows more efficient results.

In parts of constructing east-west t lot of line 7 Tehran subway, the excavating machine (EPB-TBM) passes from the top of the Abouzar’s wastewater conveyance tunnel with clear distance of 2.25 m. The FLAC 3D has been used to model this problem and find the deformations and forces of ground and linings. The modeling results show that after excavating subway tunnel, lining of Abouzar tunnel will be moving upward due to the increasing plastic zones and stress relaxation. This rate of displacement induced the internal force more than allowable designed amount in concrete lining of Abouzar tunnel. Generally, excavation a tunnel near another tunnel may lead to significant interaction effects, which mainly dependent on tunnels position relative to each other (parallel or cross), the distance between two tunnels, tunnel dimensions, lining rigidity, stress and boring environment condition as well as the method of tunnel boring. The interaction between adjacent tunnels have been investigated by different researchers using methods such as analytical and empirical, field observation, physical modeling and numerical modeling. In the current project, the tunnel of Tehran metro line 7 passes with a distance of 2.25 meters from the top of the Abuzar tunnel. Because of the nature of three-dimensional problem of interaction between underground spaces, numerical modeling is an appropriate tool for the analysis of these complicated problems. Therefore, FLAC3D software have been used in order to investigate into the interaction analysis. The purpose of modeling is study on stability of support system of Abuzar tunnel during tunnel excavation of Tehran metro line 7. Methodology and Approaches: In this paper, the finite difference method (FDM) is used for modeling and solving the problem. FLAC 3D program which uses FDM was selected in order to study the interaction between the two tunnels, in construction stage. For this purpose, at first Abouzar tunnel modeled and excavated, then impact of stepwise excavating of line 7 Tehran subway on lining system of Abouzar tunnel is investigated numerically. History of Internal forces, bending moments and structural displacement of Abouzar’s tunnel lining have been provided and studied. Engineering recommendations have been proposed in different-leveled intersecting tunnels. Results and Conclusions: The results of modeling show that after excavation of metro tunnel, the support system of Abuzar tunnel will be uplifted because of increasing the plastic zone and stress relaxation. This displacement causes internal forces in Abuzar tunnel lining which are more than allowed values.

Prioritising mines for investment is one of the major issues in mining economic. In this kind of problem, mines are ranked according to the conditions and characteristics of mines like value of mine reserve, production capacity of mines etc.. Based on this ranking, investment priority for each mines determined. In this study, priority investment for oxidized copper mines in Semnan province has been found using the TOPSIS method, a multi-criteria decision-making methods. TOPSIS method is based on the concept that the chosen alternative should have the shortest geometric distance from the positive ideal solution and the longest geometric distance from the negative ideal solution. In this study, 12 different criteria, and 33 copper mines in Semnan province were considered for prioritization. The decision criteria were weighed by surveying of experts in the field and then the importance of each factor have been determined using AHP method. Finally, using TOPSIS method, Chah Mosa, Kolut and Chah Farakh copper mines are ranked as first, second and third priority for investment, respectively. Also, sensitivity analysis is done to find the weight of criteria which are the most effective in prioritizing mines.

Assessment of rock mass caveability is one of the important factors in the success of the block-caving mining. prediction of rock mass caveability is complicated due to the wide range of effective factors and the lack of complete knowledge of the impact of each factor on the rock mass caveability. Existing methods do not consider all the factors affecting the caveability process. This study uses the Rock Engineering systems (RES) approach to assess the rock mass caveability. After the implementation of the rock engineering system and ranking the influencing factors, the caveability index for selected mines was calculated. The results of this study have shown the sufficiency of RES approach in taking into account of all effective parameters.
Introduction In mining methods based on caving of ore such as block caving and sublevel caving, caveability of ore and surrounding rocks is of great importance. If the caveability of ore, would not properly evaluated it will impose high cost and losing of time on mining companies.
A major challenge in developing of existing caveability predicting methods is the taking into account of the values related to geomechanical, environmental, geometric and operational factors of rock mass, with a simple yet efficient method.
Methodology and Approaches RES is a powerful system approach to study the effect of influencing factors on the performance of an engineering system. The first step of the method is to establish interaction matrix and coding of the matrix. The principal factors considered relevant to the caveability have listed along the leading diagonal of a square matrix and off-diagonal terms have been coded by ESQ method. Then by Using RES approach the effective parameters on caveability have ranked. In the next step caveability index of Elteniente, Kemess and Ironcap mines, determined and compared with the results of well-known experimental methods, as the Laubscher caving chart, the extended Mattew’s stability graph and Stewart and Forsyth methods.
Results and Conclusions The results of this study have shown that Geomechanical factors are the most dominant and geometric factors are the most subordinate factors in the system. In addition, geomechanical and environmental factors have the highest and the least interaction on the system, respectively. Furthermore, although the hydraulic radius is different in experimental methods, but follows the same trend and there is a good agreement between the results of rock engineering systems and experimental methods there. At last a classification for the caveability index has introduced.

The aim of stope limit optimization is to define an area with maximum economic value, for which, in accordance to the mining method used, all technical and geometrical constraints is considered. Although more than four decades have passed since the first presentation of underground stope optimizatiom algorithm, the development of these algorithms in comparison with similar algorithms used in open pit mines, have been very slow. This may be due to the high variety of underground mining methods and complexity of economic modeling of mining limit. In this paper a 3D comprehensive algorithm, which is called MLOA, is proposed. This algorithm runs on a variable value block models and is able to determine the number, height and optimal layout of levels. To determine the optimum limit of stopes, MLOA has used a heuristic algorithm which is called SOA. In SOA algorithm, Technical and geometrical constraints such as the minimum and maximum of stope dimension and minimum width of rib pillars have been regarded. The optimum location and dimension of stopes within specific level can be determined by using SOA. In order to verify the methods , the results of the application of SOA algorithm on hypothetical economic block model, are compared to similar rigorous algorithm’s results. The results demonstrate the capability of SOA algorithm in determining optimum limit of stopes.

The accurate prediction of rock mass cavability is one of the key factors in block caving mines. Today, the industry interest in application of caving methods in the strong rock masses, the reliable prediction of rock mass cavability will be much more important. If the cavability of the orebody is not assessed with a reasonable accuracy, expensive and time-consuming measures may be required subsequently to initiate or sustain caving. Therefore, it is of great importance to identify the effective parameters and interactions between them. Here, the effective parameters on cavability are introduced and then, by using RES method the level of dominant or subordinante of each parameter is assessed. In-situ stress, caving rate and fragmentation are the most dominant factors. Joint orientation is the most dominate parameter in the system (Max C-E) and potential of cavability is the most subordinate parameter (Min C-E).