JOURNAL OF ANALYTICAL AND NUMERICAL METHODS IN MINING ENGINEERING
Year:2020 | Volume:10 | Issue:22|Papers Count:7

SummaryThe aim of this paper is to present a new algorithm to determine ultimate pit outline and mining sequence simultaneously based on the maximization of the net present value (NPV). For this purpose, a nonlinear binary mathematical model was established and then a heuristic algorithm was developed to solve this NP-Hard problem. IntroductionThe ultimate pit limit is an important problem which is determined by maximization of undiscounted profit or NPV. The floating cone algorithm and its modified versions, Korobov algorithm, Lerchs-Grossman method and maximal flow algorithm were developed to generate ultimate pit limit based on the maximization of the undiscounted profit. Nevertheless, it is better to determine the pit outline based on the maximization of NPV. To achieve this goal some algorithms like Wang-Sevim, Latorre-Golosinski and Roman were established. Methodology and ApproachesThe binary and nonlinear mathematical model to determine the ultimate pit limit on the basis of maximizing NPV and a few suggestions for its linearization were presented. Afterwards, by defining the concepts of downward cone, positional weight and nearest ore index, a heuristic algorithm was developed to determine the ultimate pit limit and mining sequence all together. Results and ConclusionsThe algorithm was applied for 2D and 3D block models and the results showed that it is able to produce optimum outcome. Complexity of the algorithm is low and easy to use and as well as for education purpose. It is also able to consider variable slopes and grade-based constraints for production planning in the algorithm.

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.

The cement-based material is a strong and relatively cheap construction material and is therefore presently the most used construction material worldwide. This material is used as a mortar, concrete or shotcrete. Low tensile strength is an unavoidable and inherent weakness of most cement-based construction materials. Considering the wide-ranging applications of these materials, in this study, the potential of bacterial nano-cellulose on mechanical and physical properties of cement pastes was evaluated. For this purpose, the potential of bacterial nano-cellulose (BNC) as powder, gel, and coated onto Polypropylene fiber as a reinforcement in cement materials was investigated. The results of the flexural strength test showed, up to 103% increase in flexural strength of specimens containing 0. 5 wt. % BNC powder compared to control specimens. In addition, specimens containing BNC-coated fibers showed improvement in compressive and flexural strength in comparison with normal fiber mortal specimens.

In this paper, the effect of the intermediate principal stress on the failure of different rocks and the accuracy of several 3D criteria in estimating failure of the true tri-axial tests results was investigated. Then, applying linear and nonlinear regression, a new 3D criterion was proposed that the criterion can successfully predict failure behavior of deep rocks with accuracy higher than other existing criteria. Failure criteria are relations between the strength properties of rock and applied stresses and used to describe the behavior and failure of rocks. This function is determined based on analytical and empirical methods. Some researchers neglect the effect of intermediate principal stress σ 2 in the failure mechanism of rocks (2D failure criteria). However, there are experimental documents showing that the intermediate principal stress affects the failure behavior for at least some of the rocks (3D failure criteria. The intermediate principal stress has considerable effect on failure mechanism of very deep underground rock masses (such as hydraulic fracturing, wellbore and reservoir stability, underground storage in petroleum engineering). In this paper, the effect of the intermediate principal stress on the failure of five different rock types in 175 true tri-axial tests was studied. Also, the accuracy of several 3D criteria (such as Von Mises, Drucker-Prager and Pan & Hudson) in estimating failure of the tests results was investigated. Applying nonlinear regression, a new 3D criterion was proposed based on the true tri-axial tests results. Maximum, minimum, and intermediate principal stresses, along with uniaxial compressive strength and internal friction angle are used in the new criterion. In order to validation of the proposed criteria for other rocks, results of the true tri-axial tests for 190 specimens of seven different rock types were studied. The results of studies showed that the effect of intermediate principal stress is more significant in competent rocks than weak rocks and Pan & Hudson criterion gives the most accuracy with an MRAE equal to 0. 24. Von Mises and Drucker-Prager criteria gave the next best results by MRAE respectively equal to 0. 28 and 0. 44. Also, RSQ and MRAE of the proposed criterion for all type of rocks are equal to 0. 94 and 0. 06 respectively that the criterion can successfully predict failure behavior of deep rocks with accuracy higher than other existing criteria.

Integrating advantages of layer based and tomography velocity model building methods could partially resolve some of the problems in seismic imaging. This integration resulted to introduction of the hybrid tomography methods which try to overcome the problem of handling large velocity contrast by tomography methods. In this study, the velocity model building strategy in the hybrid gridded tomography method was modified to reduce the effect of velocity contrast in depth seismic imaging. The proposed strategy then was applied on a seismic data from a complex geological structures and results depicted that the hybrid gridded tomography, with the presented strategy could be used as an alternative to conventional velocity model building. SummaryThe hybrid gridded velocity model uses the concept of soft and hard regions and boundaries in the initial velocity model. In this approach, regions with anomaly velocity values are defined as hard regions and the rest of the media is considered as soft media. The contacts between regions with low uncertainty in position are defined as hard boundary and experience minimum changes in updating steps. Whilst region contacts with high uncertainty in position are considered as soft boundaries. IntroductionThese boundaries vary in position during velocity model updating. These regions and boundaries are simultaneously and separately updated in each model updating sequence. Updating of hard regions doesn’ t disturb soft regions updating results and vice versa. In the proposed strategy, the conventional velocity model is obtained to be used for defining large velocity contrasts. Afterwards soft and hard regions are simultaneously updated by gridded tomography method. Hard boundaries face small variation in place while soft boundaries might largely vary in location. After sufficient iteration, sharp boundaries are smoothed and finalized in location and together with velocity values. Methodology and ApproachesIn the proposed approach, the seismic imaging with velocity model obtained in each iteration was changed from pre-stack depth migration to post stack depth migration. The selected seismic data contains a large salt dome with surrounding dipping layers, faults and an unconformity beside the salt. Through the hybrid velocity model building, top boundary and the body of salt dome were considered as hard regions. Bottom of the salt was considered as soft boundary. Results and ConclusionsResult of applying the proposed strategy showed that this method could handle large lateral velocity contract in depth imaging. Therefore, depth imaging by the final hybrid velocity model obtain seismic image with more accuracy in positioning of seismic reflectors and body of geological structures in comparison to images obtained by conventional velocity modelling.

Identification of promising areas associated with mineralization and integration of exploratory multi-resource data-sets are essential in mineral potential modeling. In this research, big data analysis method and an unsupervised deep auto-encoder network algorithm were used to identify the exploratory targets areas associated with porphyry copper-gold mineralization in the Dehsalm strict of Iran. The results show that the identified exploratory target areas have strong spatial relationships with known mineral indices in the study area. The Prediction-Area (P_A) plot analysis shows that the generated model performs well. The result of this study demonstrates that big data analytics supported by deep learning methods is a potential technique to be considered for use in mineral prospectivity mapping.

Liners in tumbling mill transfer energy to the mill load and has a significant impact on the load behavior. In order to achieve a domestic technology of liner design, a knowledge-based package of liner design was developed by using of domestic equipment and software packages. At the first stage, a proposed liner that provides an appropriate load trajectory is obtained by simulation using GMT (grinding media trajectory) software and discrete component method (3D-DEM, KMPCDEM software). In the next stage, after validating by a model mill, the manufacturing drawings of the proposed design are prepared. After the construction and installation of the proposed liners, the liners wear is recorded using a special measuring device and after preparing a three-dimensional model of liners, a new design is proposed. Applying this domestic liner design technology for AG mill liners at the Gol-e-Gohar mining and industrial company and increasing the liner lifter face angle from 7 to 30° while keeping the original lifter height resulted in an overall increase of 17% in the mill throughput. By use of this design package in the Sarcheshmeh copper complex ball and increasing the liner lifter face angle from 0 to 15° and the lifter height from 18 to 21cm, the amount of particles smaller than 75 microns in ball mill 4 product (with proposed design) compared with ball mill 3 (with current design) increased by 2. 5% and the liners life of the first half and second half increased by 18% and 20%, respectively.