Hadi Bejari; Jafar Khademi Hamidi
Abstract
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 ...
Read More
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.
M. Zahiri; K. Goshtasbi; J. Khademi Hamidi; K. Ahangari
Abstract
There is a direct relationship between the efficiency of mechanized excavation in hard rocks and that of disc cutters. Disc cutter wear is an important effective factor involved in the functionality of tunnel boring machines. Replacement of disc cutters is a time-consuming and costly activity that can ...
Read More
There is a direct relationship between the efficiency of mechanized excavation in hard rocks and that of disc cutters. Disc cutter wear is an important effective factor involved in the functionality of tunnel boring machines. Replacement of disc cutters is a time-consuming and costly activity that can significantly reduce the TBM utilization and advance rate, and has a major effect on the total time and cost of the tunneling projects. When these machines bore through hard rocks, the cutter wear considerably affects the excavation process. To evaluate the performance of the cutters, first, it is essential to figure out how they operate the rock cutting mechanism; secondly, it is important to identify the key factors that cause the wear. In this work, we attempt to introduce a comprehensive numerical method for estimation of disc cutter wear. The field data including the actual cutter wear more than 1000 pieces and the geological parameters along the Kani-Sib transmission tunnel in the northwest of Iran are compiled in a special database that is subjected to a statistical analysis in order to reveal the genuine wear rule. The results obtained from the numerical method indicate that with an increase in the wear of disk cutter up to 25 mm, the applied normal and rolling forces can be multiplied by 2.9 and 2.7, respectively, and by passing the critical wear, the disk cutters lose their optimal performance. This method also shows that confining pressure will increase the wear of the disc cutter. By the proposed formulation, the cutter consumption rate can be predicted with a high accuracy.
Exploitation
M. Ghobadi Samani; M. Monjezi; J. Khademi Hamidi; A. Mousavinogholi
Abstract
Truck-Shovel fleet, as the most common transportation system in open-pit mines, has a significant part of mining costs, for which optimal management can lead to substantial cost reductions. Among the available dispatch mathematical models, the multi-stage approach is well suited for allocating trucks ...
Read More
Truck-Shovel fleet, as the most common transportation system in open-pit mines, has a significant part of mining costs, for which optimal management can lead to substantial cost reductions. Among the available dispatch mathematical models, the multi-stage approach is well suited for allocating trucks to respected shovels in a dynamic dispatching program. However, with this kind of modeling sequencing of the allocated trucks is not possible though it is important to find out the best solution so that getting the minimum accrued cost. To comply with the shortcoming of the traditional model, in this paper, a new hybrid model is developed and applied in Copper Mine of Iran, in which for each truck an allocation matrix is considered as input to the genetic algorithm implemented to determine the best solution. According to the obtained results, the optimal sequencing of the trucks can result in a significant (31%) cost reduction in a shift.
Exploitation
M. Mohtasham Seyfi; J. Khademi Hamidi; M. Monjezi; A. Hosseini
Abstract
Methane gas emission, accumulation, and explosion are the most important risk factors in underground coal mines. Hence, having a knowledge of methane gas emission potential in underground coal mines is of crucial importance in preventing the explosion risk, loss of life, and property, and providing miners' ...
Read More
Methane gas emission, accumulation, and explosion are the most important risk factors in underground coal mines. Hence, having a knowledge of methane gas emission potential in underground coal mines is of crucial importance in preventing the explosion risk, loss of life, and property, and providing miners' safety. The purpose of this work is to provide the prediction maps for the C1, C2, and B2 coal seams gas contents, and to identify high gas content panels in the Parvadeh No. 1, Tabas coal mine. For this, the data collected from exploratory boreholes is put into geostatistical analysis in ArcGIS in order to estimate the coal seams gas content in unsampled points using the kriging estimation method. Reviewing the gas content maps has revealed that seams of C1, B2, and C2 have gas contents more than 15 cubic meters per ton in about 84%, 55%, and 22% of the understudied area, respectively. The present work highlights the potential and the need for implementation of a methane pre-drainage system, particularly in deeper longwall panels.
