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Conical picks are one kind of cutting tools widely used in engineering machinery. In the process of rock breaking, the conical pick bears great cutting force and wear. To solve the problem, a new method, conical pick assisted with high pressure water jet, could break rock effectively, and four different configuration modes of water jet were present...
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The article describes the dynamics of drill bits, drilling modes, distribution of resistance forces when drilling with bits. The theory of drilling a well of arbitrary shape, possible shapes of contacting figures at the bottom hole and the type of drill bit operating in the rotation pair mode are considered. This type of bit has the properties of a...
Citations
... Research on the impact of water jet mining (specially designed picks with a hole and a nozzle in their axis have been used) [59], • ...
... • Investigations into the impact exerted by the high-pressure pre-cutting of the rock with a water jet placed next to the disc and in front of the disc on the cutting efficiency [21,58], • Research on the impact of water jet mining (specially designed picks with a hole and a nozzle in their axis have been used) [59], • Investigations into the influence of the use of microwaves on the cutting resistance [60], • Research on mining with discs performing additional oscillation, which required modification of the disc holder and the addition of another drive-this method is referred to as ODC (oscillating disc cutting) [17,61,62]. ...
Mechanical mining is a widely used method of separating materials from the face to obtain a useful mineral (e.g., coal, metal ores, salts, and diamonds), to make underground workings (e.g., mine galleries, tunnels, and underground garages), level roads, shape slopes, or to dig ditches. Mechanical mining is applied in the mining branch, tunnelling, road, and construction industries. Depending on the mechanical properties of the rocks, most frequently described by uniaxial compression strength, various machines and tools are used. The methods of mining high-strength abrasive rocks that have been used and developed in recent years are particularly applicable to the mining of copper, gold, tungsten, platinum ores, diamond deposits, and tunnelling. In addition to rock strength, the effectiveness of the mining process is affected by abrasiveness, which influences the rate of abrasive tool wear. Therefore, in various research and development centres, but also in production companies, tools are tested on unique stands. Tests are carried out to determine the cutting resistance and assess the wear rate. This article reviews methods and benches for testing mining tools, conical picks, and discs. Various solutions for testing single tools and cutting heads have been presented. The analysis conducted has revealed that despite the large number and great diversity of different test benches, there are no appropriate methods and stands for testing the wear rate of materials intended for mining tools.
... Methodology. Of the known models of destructive strain of coals, the most suitable is the Johnson -Cook model, which takes into account kinetic hardening and adiabatic heating of the deformable material [19][20][21]. Therefore, using the Johnson-Cook model, one should evaluate the destructibility of coals, thereby comparing it with the results of experiments. ...
The main volume of coal is mined underground using shearers. In modern shearers, auger actuators are mainly used, which are distinguished by the simplicity of design, manufacturability and reliability. However, in the process of separating coal from mass by cutting, the yield of fine grades is 40-50 % of the total production volume. Therefore, the search and development of technical solutions that provide an increase in the yield of large fractions in the process of coal mining with auger shearers is an urgent task. Traditionally, this problem is solved by increasing the thickness of the slices, which is achieved by installing cutters with a larger radial reach and increasing the shearer feed rate. An unconventional way to increase the cross section of slices by forming energy-efficient paired and group slices with mutual superposition of stress fields in the mass from the action of neighboring cutters is considered. The results of modeling the process of cutting coal confirm that an increase in the efficiency of destruction of the rock mass by the cutters of the auger executive bodies of the shearer can be achieved by a complex technical solution, including the formation of paired cuts and combined stress zones in the rock mass. As a result, the output of large fragments when cutting with paired cutters increases by 1.3-1.8 times compared with cutting with a single cutter.
... The cutting tools mainly used for coal mass excavation on continuous miners, road headers and longwall shearers are drag type of picks, where point attack picks (conical picks) are mostly used [9,11,13,14,15]. Conical picks are often applied in cutter heads mainly for the excavation of coal as they guarantee better efficiency considering the low specific energy requirement for their operation [12,13,[16][17][18][19]. Although, it's mining efficiency is reduced considerably when used in a coal seam containing hard and abrasive rocks which translates to higher costs of operations. ...
A coal mine in the central district of Botswana is experiencing premature failure of conical picks which mine 150-350 tons of coal/ pick rather than 400 tons/pick specification. This has adverse implications on business productivity and profitability due to the need to replace the picks with new ones. This study employed physical observation of mining operation; macroscopic and microscopic examinations; weight loss analysis; micro-hardness, and fractography analyses of one hundred and ninety-three (193) worn-out and five (5) new picks to investigate root causes of its failure and failure mechanisms with a view to identifying mitigation measures to avoid recurrent failure. It was observed that the picks situated at the extreme right and left ends of the cutter drum failed most frequently. Common modes of failure discovered for Botswana coal mine picks include one-side wear of the pick body, pull-out of pick’s carbide tip, slimming steel body and even wear of carbide tip, and carbide tip. Furthermore, cracking and crushing of tungsten carbide (WC) grains, cavity formation and pitting, coal intermixing, abrasion wear, long and deep cracks, rock channel formation, and corrosive degradation were identified as the failure mechanisms. Recommended mitigation measures to avoid repeated failures include the use of structurally stable materials at elevated temperature and characterised with improved hardness, toughness and wear resistance for pick manufacturing; exploring manufacturing technology that imparts improved bonding in the constituent materials without degrading material properties; redesigning of pick’s flange; and inspection of pick’s free rotation of the pick before starting any shift.
... However, the u under impact of the CO 2 jet is larger than that without the CO 2 jet, and it increases with the increase in the impact velocity. The reason is that after the jet impacts the rock surface, a layer of pressure water film is formed, which attaches to the rock surface and prevents the tensile failure of rock chips [36]. ...
... The reason is that the jet formed a layer of pressure CO 2 film on the rock surface at this time, which prevented the rock from breaking away. In this case, the mechanical cutter cannot perform to its full potential [36]. Although the jet at a distance of 2.5 times of the nozzle diameter can offer great support for the composite rockbreaking, this distance is too small to be applied in the rock bit design. ...
CO2 drilling is a promising underbalance drilling technology with great advantages, such as lower cutting force, intense cooling and excellent lubrication. However, in the underbalance drilling, the mechanism of the coupling CO2 jet and polycrystalline-diamond-compact (PDC) cutter are still unclear. Whereby, we established a coupled Smoothed Particle Hydrodynamics/Finite Element Method (SPH/FEM) model to simulate the composite rock-breaking of high-pressure CO2 jet & PDC cutter. Combined with the experimental research results, the mechanism of composite rock-breaking is studied from the perspectives of rock stress field, cutting force and jet field. The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter. Meanwhile, the high-pressure CO2 jet has a positive effect on carrying rock debris, which can effectively reduce the temperature rising and the thermal wear of the PDC cutter. In addition, the effects of CO2 jet parameters on composite rock-breaking were studied, such as jet impact velocity, nozzle diameter, jet injection angle and impact distance. The studies show that when the impact velocity of the CO2 jet is greater than 250 m/s, the CO2 jet could quickly break the rock. It is found that the optimal range of nozzle diameter is 1.5–2.5 mm, the best injection angle of CO2 jet is 60°, the optimal impact distance is 10 times the nozzle diameter. The above studies could provide theoretical supports and technical guidance for composite rock-breaking, which is useful for the CO2 underbalance drilling and drill bit design.
... Investigations were conducted for four different configurations of an HPW jet in relation to the pick edge. A view of these configurations and the scheme of the three most often used solution is shown in Figure 1 [1,14]. Based on the analysis of the test results described in the above publications, it can be concluded that both the location and parameters of HPW jets have a large impact on the obtained effect. ...
... However, such an arrangement of the jet is only possible under laboratory conditions. In practice, the nozzle in the pick edge gets damaged quickly [13][14][15]. [14]. ...
... In practice, the nozzle in the pick edge gets damaged quickly [13][14][15]. [14]. ...
The mining of hard rocks by mechanical methods, using cutting tools, is associated with problems such as sparking, dust generation and increased wear. The application of disk tools allows limiting these problems but requires constructing a machine with large dimensions and weight. To limit these problems, high-pressure water jets can be applied. The article presents the effects of using this solution in the field and stand tests when mining rocks with a symmetrical disk. The results of the bench tests of high-pressure water jets to support the process of mining with symmetrical disks, carried out at the AGH University of Science and Technology, performed on a unique test stand, which enabled the samples to be mined in a circular trajectory in conditions similar to real ones, are presented. With the use of a dimensional analysis, a theoretical-empirical model was developed to estimate the impact of slots cut by water jets on the tool load and the amount of output as a function of slots spacing and depth. Considering the similarity criteria for the mined rock sample (mechanical properties), it is possible, with the use of this model, to estimate the most advantageous working parameters while hydromechanical mining uses disks on a larger cutting radius.
... And some scholars have taken tests to research the rock cutting. Liu et al. [7] presented a kind of rock drilling method and conducted tests to research its cutting performance. Too many tests about the process of chip formation were to be provided by Che et al. [8]. ...
The new method of rock breaking based on the combination of circular sawblade and conical pick was proposed to improve the effectiveness of hard rock breaking. The numerical simulation method was applied to research the conical pick cutting arc rock plate by ANSYS/LS-DYNA. The conical pick cutting arc rock plate numerical simulation model was established to research the influence of arc rock plate structural parameters and cutting parameters on cracks formation and propagation of the arc rock plate and the cutting force in the process of conical pick cutting arc rock plate. The amount of cracks is positively correlated with arc rock plate thickness, the cutting speed, and distance of cutting point to arc rock plate central axis and negatively correlated with the cutting angle. The mean peak cutting force is positively correlated with the thickness of arc rock plate and the distance of cutting point to arc rock plate central axis; however, it is negatively correlated with the arc rock plate height and width and cutting angle of conical pick. The simulation results can be used to predict the conical pick work performance with various cutting parameters and structural parameters.
... To prepare free faces, researchers have employed a high-pressure waterjet, highpower laser, multistage cutterhead, undercutting TBM, and many other techniques. Ciccu and Grosso (2013), Liu et al. (2014), and Liu et al. (2015) found that waterjet-assisted mechanical rock breaking using conical or disc cutters can reduce rock-breaking forces and improve cutting efficiency. Lu et al. (2013) and Tang et al. (2014) developed a novel rock-drilling technique where a pilot hole free face was prepared using an abrasive waterjet from the cutting bit center that significantly increased the drilling depth and reduced the cutting forces and bit wear. ...
Hard-rock cutting Free face Disc cutter Rock-cutting efficiency A B S T R A C T This study presents the results of full-scale hard rock (granite) cutting experiments using tunnel boring machine disc cutters at different free-face conditions. Rolling cutting tests are conducted on a full-scale rotary cutting machine with a commercial constant cross-section disc cutter with a diameter of 432 mm. Three free-face conditions are prepared for the tests: vertical free faces, inclined free faces (with different heights and cut spacings), and narrow kerfs. The rock-cutting force, rock-cutting trajectory, specific energy, and shape of the representative rock chip are analyzed and compared for each test. The major results are as follows. First, for the granite subjected to vertical free-face conditions, the cut spacing should not be larger than the critical value of 140 mm in order to break the rock successfully with high efficiency. Second, the free face that is closer to parallel to the penetration direction exhibits a decreased rock-cutting force and improved rock-cutting efficiency. Third, narrow kerfs are not as effective as vertical and inclined free faces for assisting rock breaking. Therefore, to exploit the advantages of narrow kerfs, they should be prepared close to the cutting path, with spacings of less than 40 mm for the studied granite. Fourth, the applied grain-based discrete element method is effective for numerical analysis of the rock-cutting process because the rock-fragmentation performance is very similar to that in the laboratory tests.
... In that paper, the water jet was directed in front of the tool. Liu et al. [9][10][11][12][13] performed numerical simulations and experiments to study the rock breaking performance of different configuration modes of conical tools assisted by water jets. ...
It has been found that the impact performance of water jets can be changed by its properties, which include pressure, additive, and mode of jet. Thus, an abrasive water jet (AWJ) has been developed as a new method. However, there is little research on the effect of abrasive concentration on the impact performance of abrasive jets. Thus, the SPH method is used to establish an abrasive water jet crushing concrete model to study the effect of abrasive concentration on the impact force, concrete internal energy, abrasive particle distribution, crushing depth, and damage and crushing efficiencies under different concrete compressive strengths and abrasive densities. The results indicate that there is little effect of the abrasive concentration on the peak impact force under different compressive strengths and abrasive densities, while the mean impact force tends to increase linearly with the abrasive concentration. The internal energy of the concrete increases stepwise with the abrasive concentration under different compressive strengths and abrasive densities. The concentration of 10%∼20% is the rapid increasing stage. The crushing depth and damage efficiencies are all maximum at a concentration of 20% under different compressive strengths and abrasive densities. After the concrete was impacted by the water from the water jet, it is divided into rebounding particles and intrusive particles. The more the intrusive particles, the easier the concrete to be crushed and damaged.
... Bilgin et al. [7] and Kel et al. [8] carried out the experimental researches with the linear cutting machine, in order to study the dominant rock properties that influenced on conical pick performance. Liu et al. [9] proposed a new rock cutting method and carried out the experiment to study the cutting performance. e numerical simulations are more detailed and faster than the experimental research. ...
In order to overcome conical pick wear in the traditional rock cutting method, a new cutting method was proposed on account of increasing free surface of the rock. The mechanical model of rock plate bending under concentrated force was established, and the first fracture position was given. The comparison between experimental and numerical results indicated that the numerical method is effective. A computer code LS-DYNA (3D) was employed to study the cutting performance of a conical pick. To study the rock size influenced on the cutting performance, the numerical simulations with different thickness, width, and height of a rock plate was carried out. The numerical simulation with the different cutting parameters of cutting speed, cutting angle, and cutting position influenced on cutting performance was also carried out. The numerical results indicated that the peak force increased with the increasing thickness of rock plate. With the increasing width and height of the rock plate, the peak force decreased and then became stable. Besides, the peak force decreased with the increasing of cutting position lxp / lx . Moreover, the peak force increased and then decreased with the increasing of cutting angle. The cutting speed has nonsignificant influence on the peak force. The strong exponential relationship was obtained between the peak force and cutting position, thickness, height, and width of the rock plate at a confidence level of 0.95. A binomial relationship was observed between the peak force and cutting angel. The cutting force comparison between traditional rock cutting and rock plate cutting indicated that the new cutting method can effectively reduce peak cutting force.
... The developed technical solutions for changing the geometry and shape of the head to increase the destructive capacity of the tool are presented in proceedings (Fader and Lammer, 2011;Greenspan et al., 2014;Sarwary and Hagan, 2015). Tompson and Tank (1990) and Liu et al. (2015) studied the impact of water supply in the breaking area on the efficiency of rock breaking. ...
The objective of this study was to find opportunities for metal waste recycling in the process of rock breaking in mines. A built-up cutter design for a combined cutter-loader and a recycling technique for a considerable portion of the deteriorated tool are suggested. Industrial tests have proven the possibility of a ten-fold increase in the use of cutters on mining machines for coal rock mass destruction. The proposed technique allows a four times reduction in metal consumption in the production and use of cutters and a reduction of the ultimate resulting waste by 80%. This advanced technique could be transferred extensively into such industries as open-cast mining, repair of motor-roads, construction and agriculture.
