jafar khademi hamidi

Determination of stope boundary is a critical step in underground mine design, directly impacting project profitability and operational plans. Developing efficient and accurate algorithms for solving the Stope Boundary Optimization (SBO) problem has been a challenging task. In this study, a metaheuristic Discrete Imperialist Competitive Algorithm (DICA) was introduced for the SBO problem. The DICA algorithm, following a simulation-based approach, provides initial solutions in the search space and identifies the optimal solution after evaluating each one. Tested with different operators such as assimilation and revolution, and various initial populations, the suggested algorithm was applied to a 5*5*5 m block model of a copper deposit comprising 15,945 blocks. The results demonstrated the algorithm’s capability to determine stope boundaries within a reasonable computational time. For validity check, the results were compared with those obtained from the Maximum Value Neighborhood (MVN) and floating stope algorithms. The comparison revealed that DICA outperformed both algorithms.

The resistance properties of the intact rock are dependent on the mineralogical composition and texture of the rock material. In this research, some quantitative relationships were found between petrographic and mechanical properties of sedimentary rocks collected from different locations. The results revealed that stone-forming minerals have a great and governing impact on mechanical properties.

This work aims to investigate the effect of water saturation on cutting forces and chipping efficiency by performing a series of small-scale linear cutting tests with a chisel pick on twelve low- and medium-strength rock samples. The peak and mean cutting force acting on the chisel pick are measured and recorded under dry and saturated cutting conditions by the strain sensors that are embedded in the dynamometer. Also the amplitude of cutting force fluctuations in dry and saturated cutting conditions is compared by the standard deviation measurement of cutting force data, and its relationship with the size of cutting fragments is investigated. The results obtained show that the peak cutting force is reduced in saturated conditions compared to dry conditions. The mean cutting force in the synthetic sample cutting test is unchanged or in some cases increase, while in the natural samples it decreases. The relative increase in the mean cutting force in synthetic rock specimens is due to the paste state of fine materials produced from saturated cutting and chisel pick clogging. A strong correlation is found between the standard deviation of cutting force data and the average size of rock debris, indicating that the standard deviation of cutting force data is a useful measure for evaluating the chipping efficiency. The present study's findings reveal that to have an efficient excavation system in field operations, it is necessary to consider the presence of water and saturated conditions in designing the cutting machine's operating parameters and predicting the performance of mechanical excavators.

In mechanized mining and tunneling operations, the interface of existing rock layers poses a variety of challenges including cutter failure, machine vibration, and low advance rate without prior notification. As a result, proper understanding of the cutting process and the tool-rock interaction is critical for machine design in these circumstances. In this study, a lab-scale investigation on the interaction between rock and tool to determine the cutting forces at transition zone was carried out in mechanized excavation laboratory of Tarbiat Modares University using a small-scale linear cutting machine equipped with a disc cutter of 54 mm in diameter. Three types of samples were used in the study: sandstone with a strength of 37 MPa and two types of synthetic gypsum with strength of 21 and 24 MPa, in a mixed condition. Experiments with linear cutting machine were carried out at cutting depths of 1, 2, and 3 mm. Laboratory studies revealed that as the cutter approaches the interface between two soft and hard specimens in mixed specimens, the normal and rolling forces vary dramatically, and the difference in the ratio of forces in the transition zone diminishes as the cutting depth increases. It was also revealed that the ratio of boundary cutting forces to rock cutting forces in unmixed mode reduces as cutting depth increases. Taking into consideration the highly variation of cutting forces pattern at the interface, the importance of selecting appropriate cutters for tunneling machines and mechanical excavators increases in the field conditions. Also, it was revealed that the difference in cutting forces results in shock load at the transition zone where the cutter passing the interface of two rock layers. This shows the importance of proper design of cutter in respect of toughness and hardness and its impact in reducing cutter failure in mixed face conditions.

The brittleness is an important rock property and effective in rock excavation. Recognition of the relationship between drillability and brittleness will increase performance the rock excavations. In this study, the number of 16 samples has been studied rock mechanical properties of granite, granodiorite, dolomite, hornfels and marble in the area of Glass water conveyance tunnel project in the margin of Naghadeh city. The number of 16 brittleness indices were calculated with stress-strain curve, modulus and rocks strength properties. In addition, Sievers’ J-miniature drill test and the brittleness test are carried out and DRI values were calculated. The statistical relationships between the brittleness indices and the drilling rate index are showed a strong correlation between B3 brittleness index (R2= 0.76 and RMSE= 1.02 coefficients) and B4 brittleness index (R2= 0.79 and RMSE= 0.95 respectively) with rocks drilling rate index. The statistical relationships are compared with study former between the brittleness indices and the drilling rate index of rocks. The Precision and accuracy of relationships are confirmed with relationships former. In addition, a model was presented with multiple regression analysis. It can use for the assessment of rock drillability.

Brittleness and modulus of toughness are among the most important inherent properties of rock, which are determinative for rock excavation operations. In this study, mechanical properties of granite, granodiorite, dolomite, hornfels and marble were studied in the area of Glass water supply tunnel near the Naghadeh city (NW Iran). The stress-strain curve area and rocks strength properties were applied to calculate 13 brittleness indices and modulus of toughness. Statistic relationships between brittleness indices and toughness of modulus suggest strong correlation between B3 brittleness index (R2= 0.83 and RMSE= 5.46 coefficients) and B4 brittleness index (R2= 0.83 and RMSE= 3.85) respectively with modulus of toughness. The statistical relationship between modulus of toughness and specific energy indicates a strong correlation (R2= 0.85). The modulus of toughness and brittleness are useful parameters for estimating specific energy of rock cutting. Since the modulus of toughness increases with specific energy of rock cutting, it enabled us to estimate the specific energy of rock cutting.

Rock cuttability always has been recognized as one of the most effective parameters in selection and design of cutting tools and prediction performance of mechanical excavator machines. Field, experimental and theoretical methods have been applied into determination of rock cuttability. In this study, the theoretical model of rock cutting forces estimation presented for V-shape disc cutters was modified taking into account the influence of cutter edge radius. In order to validate the proposed model, full-scale rock cutting test data presented by Balci and Tumac (2012) and t-test with 99% interval confidence have been implemented. The results showed that there is a strong correlation between estimated rock cutting forces and real data, and since the p-value is more than α=0.01, both methods have the same values on average. To study the effect of edge radius of V-shape disc cutters, the proposed model was used. The results showed that for a constant edge angle, increasing edge radius increases cutting forces of blunt disc cutter more than those of sharp disc cutter. Also, with increase in penetration depth, the effect of edge radius on cutting forces diminishes in such a way that the cutting forces approach those of sharp disc cutter. In other hands, increasing edge angle caused a non-linear increase in blunt disc cutter cutting forces for a constant penetration depth.

Summary
One of the most important results of the linear rock cutting process is the accurate estimation of the cutting forces applied to the disc cutter which can be a prelude to the development of models for predicting the performance of all tunnel boring machines (TBM). In this study, numerical modeling of rock cutting process by a disc cutter using finite element code ABAQUS has been implemented. For model validation, the results of the linear cutting machine tests (LCM) by Previous researchers have been applied. After solving the proposed model, the forces on the disc were calculated in three directions of the rock cutting model and the mean of each force was calculated by a code that was developed in MATLAB software. Comparison of laboratory results and numerical modeling shows 11.1% error for the mean normal force, 5.6% error for the average rolling force, and 10% error for the average lateral force. By comparing the results of numerical modeling and linear cutting experiments, we can conclude that there is a good agreement between them.
 
In this study, a numerical model of linear rock cutting process based on finite element method (commercial code  ABAQUS) was used. To validate the proposed model, Rostami's (1997) linear rock cutting test on the Indiana limestone sample was used. Due to the unavailability of this rock sample, data from other texts were used to obtain input parameters to the model. A model assembly with a single disc cutter similar to laboratory test was simulated. By solving the proposed model, the forces applied to the cutter were calculated.
 
Methodology and Approaches
In order to model linear rock cutting procedures, Commercial finite element code ABAQUS/CAE was employed and for validating that, laboratory linear rock cutting test by Rostami (1997) was considered. Rock and disc cutter models was built in ABAQUS GUI module and to simulate rock behavior of rock model, a linear strength criterion was implemented in the model. Boundary Condition for disc cutter was similar to TBM’s working status with linear velocity of 2 meter per seconds and angular velocity of 9.3 radians per seconds.
 
Results and Modeling shear forces showed a similar trend to the experimental results. On the other hand, the comparison of the cutting forces of the experimental test with the numerical model results showed 11.1, 5.6 and 10% differences for the normal, rolling and lateral forces, respectively. This discrepancy seems to be due to the complexity and nonlinearity of the rock-cutting problem and the impossibility of considering all the parameters governing to rock-cutting process with a natural disc cutter. However, further analysis is being done by modeling on other rock samples to confirm the results.

This study uses multiple indicator kriging estimator based on assayed data acquired from 48 exploration boreholes in Tabas coal mine in order to predict gas content of coal seams. Results of the estimated block models showed that approximately 12% of the total area has the gas content of less than 5 (m3/ton) (Low risk), 11% has 5-10 (m3/ton) (Medium Risk) and 15% has 10- 15 (m3/ton) (High Risk), while about 62% of total area has the gas content of more than 15(m3/ton) which is of a high risk. Therefore, according to the experiences from mined panels, in the zones with lower to median gasification risk, it is possible to keep the mining operation running with management and optimization of the ventilation system. However, in the zones with higher gasification rate, demethanization process is mandatory.

Design and selection of a proper machine and its performance prediction is a very delicate and important part for planning and estimation of project costs in mining and mechanized tunneling. Assessment of rock cuttability in mechanized excavation includes the study of rock behavior and rock-tool interaction. Accordingly, laboratory rock cutting test is the most reliable method to precisely evaluate the behavior of rock and tool in a close condition to real field situation. In this study, the small scale linear cutting machine was used for assessing the rock cuttability and its relationship with rock mechanical parameters. To do this, test specimens were selected from Qom Upper Red Sandstones. At the same time, standard tests were carried out for detailed rock characterization and determination of its physical and mechanical properties. Upon performing the tests, the cutting force and specific energy respectively showed linear and nonlinear relationship with the cutting depth. Also, the cutting speed didn't show a meaningful relation with cutting force and specific energy. The results obtained from rock cutting tests were compared with those from Evans rock cuttability model. Although the experiment is in good agreement with theory, more tests are underway to achieve more accurate results and develop a new model for determination of rock cuttability.

Estimation of cutting forces acting on a disc cutter while cutting rock has been used for cutter head design and performance prediction of tunnel boring machines (TBMs). On the other hand, cutting forces is resulted from pressure in contact zone between disc cutter and rock. In this study, numerical modeling of rock cutting procedure with disc cutter by applying commercial finite element code ABAQUS is performed and in order to validate this model, contact zone pressure between disc and rock was compared by Rostami(1997) ‘s semi-empirical model. Modeling Shows 14 error percentage that confirms good relation between two models. The other result of this modeling is study the effective geometrical parameters of disc in pressure distribution of contact zone area in linear rock cutting procedure.
Summary
In this Study, linear rock cutting procedure of a single disc cutter was modeled by Commercial finite element code ABAQUS/CAE. Numerical models of rock and disc with perfect match by laboratory testing of linear rock cutting test by Rostami(1997) was built and finally validated. Pressure distribution of cutting zone with considering of non-loading zones was studied and was compared with semi-empirical model of Rostami(1997). With lower than 14% of error percentage comparing laboratory result, This models shows a perfect match. Also, geometrical parameters of disc cutter was studied to find the effects on pressure distribution zone of contact area. With a longitude and a latitude cross sections of rock model in cutting path, it was concluded that with increasing edge and angle of disc tip, micro cracks was formed in rock. Although the disc diameter causes increasing weight of disc, resulted pressure distribution has less changes.
Introduction Rock cutting procedures is an indentation of a cutter into rock that formed a pressure bubble immediate beneath cutter in rock and finally a soft powder is formed around the cutter. This bubble develop a crack pattern to rock material. In 1993, Rostami & Ozedmir believe that this bubble has a hydrostatic pressure forms that has linear behavior but in 1997 by calibration of disc and do more rock cutting tests, found out the other form of pressure bubble and non-loading zones exist in rear and forward of disc cutter in cutting procedure.
Methodology and Approaches In order to modeling linear rock cutting procedures, Commercial finite element code ABAQUS/CAE was employed and for validating that, laboratory linear rock cutting test by Rostami (1997) was considered. Rock and disc cutter models was built in ABAQUS GUI module and to simulate rock behavior of rock model, Strength criterion with linear equation of state was implemented to material model. Boundary Condition for disc cutter was similar to TBM’s working status with linear velocity of 2 meter per seconds and angular velocity of 9.3 radians per seconds.
Results and Conclusions The results from Numerical modeling of rock cutting that validated by laboratory test of Rostami (1997) shows prefect match with semi-empirical model. Even though this model can be employed in other applications of TBM designs, more study is needed to find out deeper issues of rock cutting procedures.

Underground mine roof collapse is one of the most critical problems encountered by miners. Faults and fractures decrease the strength of overlying strata. As a result, knowledge of the roof geology and quality within coal mining before coal extraction is necessary. In this study, geostatistical estimator was used to predict the roof condition in Tabas coal mine. First, core data from 33 exploration boreholes was gathered. Ordinary Kriging method was chosen as the best estimation method based on the quality of data and the absence of isotropy. Also, the best variogram model was selected among exponential, spherical and Gaussian ones considering the evaluation criteria including MPE, RMSSPE, ASE and RMSPE. Cross validation showed the high accuracy level of the geostatistical estimator. The roof classification map of Tabas coal mine was built using ArcGIS. Based on the obtained results, approximately 22% of total area is under a weak roof, and 78% covered with an intermediate roof. For validity check, the geological experiences obtained during the extraction of panels E1 and E2 and real data were compared with the final ArcGIS map of mine roof classification. The real data regarding the mining operation and downtime for the mined out panels verified the mine roof classification was obtained by geostatistical analyst and ArcGIS model in this study.

Cost estimation is one of the most critical tasks in prefeasibility studies and planning of tunnel construction projects. This paper presented a cost estimation model for excavation and support of short tunnels using uni-variate (UVR) and multi-variate regression (MVR) techniques. Hence، a database consisting of two explanatory variables including RMR and tunnel depth along with tunnel support and excavation costs was compiled from 12 tunnel sections in the North-West of Iran. The statistical significance and validity of the obtained models was checked by using some statistical tests، which proved that this model provides the possibility of a fast and adequate cost estimation of the excavation as well as support cost of tunnels at the phase of pre-feasibility study in tunnel projects.

In longwall mining, the roof strata behind the stope is caved with face advancing. This is followed by a high load distribution around the panel and gob. Determination of the stress concentration, its distribution around the panel and the influencing parameters such as the stope length are of critical important to design of longwall mining. Both numerical and empirical methods can be used to investigate the effect of stope length on distribution and concentration of stress induced at the panel. In this paper, numerical modeling and analysis of a longwall panel were carried out by using a 3D numerical model for investigating the effect of stope length on stress distribution in Tabas coal mine, Parvadeh No. 1. A sensitivity analysis of the impact of six different values of stope length on abutement stress showed a nonlinear relation between the stope length and front abutment stress. The analyses results revealed that with a 30 percent increase in the stope length from 190 to 245 m, front abutment stress increases only to 10 percent (i.e. 5.55 to 6 MPa).With stopes longer than 245 meters up to 300 meters, an increase of 20 percent in stope length resulted in a 27 percent decrease of roof stress (i.e. 6 to 4.4 MPa). Also, results obtained from modeling studies revealed that the location of maximum front abutment stress increases from 5 to 15 meters in front of the face with change in stope length from 190 to 300 meters.