Papers by Keyword: Blasting

Abstract: This study highlights the performance analysis of rock fragmentation on mine excavation process efficiency and powder factor, instantaneous dig factor and loading efficiency. The power regression analysis of the relationship between powder factor and loading efficiency, defines the highest loading efficiency at the optimal powder factor ranging from 0.48 to 0.52 kg/m³. Loading efficiency with powder factor 0.50 kg/m³ is 0.469 while loading efficiency with powder factor 0.30 kg/m³ is 0.253. However, when considering the powder factor of more than 0.80 kg/m³, the efficiency dropped to 0.217 due to the generation of excessive fines and the reduction of the bucket fill rates. The R² value of the regression model is 0.995, thus, confirming the high predictive ability of powder factor while measuring the loading efficiency. In comparison to the original parameters, the optimized powder factor selection reduced the cycle times by as much as 22.4% and increased fragmentation consistency, according to the study. This study potentially highlights the need for enhanced blast design, which optimises total excavation costs and maximises mine productivity.

Abstract: This research was carried out to compare the performance of ANFO and Ammonium Nitrate on fragment size distribution by using the ANFO and AN as the column charge in blasting operations, measuring the fragmentation size after each blasting operation, characterizing the fumes evolving from the blasting operation in each case and compare the performance of the ANFO and AN. The densities of the rock deposit were derived as 2.638 g/m³ and 2.622 g/m³ for Block A and Block B respectively. The rebound hardness tests ranged from 47 to 61 for Block A and Block B from 48 to 54. The total explosive charge used for each of the blocks was 0.1 kg. The muckpile magnification ratio for Block A was 0.008 and Block B was 0.004. The fragmentation sizes for Block A range from 1.869 cm to 19.411 cm and Block B from 2.414 cm to 37.177 cm. The magnification ratio and fragment sizes show that Block A has better fragmentation than Block B. Ammonia gas was not present in the area of study before blasting but the fume emitted after first blasting with ANFO produced 0.08% of Ammonia gas and after the second blasting with AN 0.07% were produced. The oxygen level was reduced from 20.9% before blasting to 19.2% after the first blasting and 19.1% after the second blasting. It was deduced that blasting with ANFO generated more Ammonia gas than blasting with AN but the Oxygen level when ANFO is used was higher than when AN is used. Keywords: Blasting, density, explosive, fragmentation, magnification ratio

Abstract: Blasting has been adjudged as the cheapest method of hard rock fragmentation. The itinerary of rock breakage through blasting in open pit mines is a complex portent which is measured via various variables and parameters. This research investigates the impact of short burden and spacing on blasting output with the aim of establishing a more suitable and economically viable approach. Trials and proposed methods were adopted to investigate blasting geometry results. Results obtained showed that the trials method of 1.2 m by 1.2 m and proposed blasts method of 2.0 m by 2.0 m burden and spacing at 9m depth, covered areas were 80.64 m² and 99.36 m² respectively, while at 12 m depth with same blasting geometry covered 224 m² and 276 m² respectively. The first trial and proposed blasts methods using burden and spacing of 1.2 m by 1.2 m produced 2,583.71 tons and 2,387.62 tons respectively. Hence, with the use of 2.0 m by 2.0 m burden and spacing, the blasts operations produced 7,176.96 tons and 6,632.28 tons respectively. Meanwhile, the results revealed that, short burden (≤ 1.2 m by 1.2 m) threatens safety in which flyrocks are spawned and it’s dangerous to equipment and personnel, at the same time, the areas covered, quantity produced (i.e. volume) and the tonnage were small compared to the engineering control methods. However, it was found that the trials blast methods were not economically worthwhile in terms of explosive consumption compared to the proposed measure of the geometry.

Abstract: The article discusses the experience of drilling and blasting operations in the conditions of high water cut of the rock massif, it also presents practical experience in modeling and forecasting water inflows into workings. By the example of the Koashvinskoe deposit, the problems of work in conditions of high water cut of the rock mass leading to the collapse and silting of drilled boreholes are considered. The article presents calculations showing the effectiveness of the drainage systems for lowering the groundwater level of a prepared rock mass section. The paper provides a rationale for the optimal mass of bottom charges for the preparation of drains in the rock mass, depending on the water saturation of the mass and the grid of drilled boreholes.

Abstract: The weakening of the rock massive has been determined during boring of freezing tubes. It has been proved that the freezing column is disjoint from the massive by mud solution with strength 0,7-0,8 MPa, which fills out the drill hole Ø250mm. Were established lows of forming of the shear stress regions on the freezing pipe`s circuit. Were suggested adjunctive technological measures such as exhaust solution injection in the annular space, which reducing intensity of blasting loads on freezing pipe.

Abstract: Fluid dynamic bearings, which have an advantage in high-accuracy revolutions, are employed for spindle motors of hard disk drive, cooling fans for central processing unit, spindles of machine tool, etc. Micro herring-bone grooves are manufactured on cylindrical surface of the shafts in the bearing units, and they generate dynamic pressure during spins. Although the depth of the herring-bone grooves is generally constant, the shafts of which groove depth decreases from the ends of the groove array to its center improve the performance of bearing. The micro grooves are mainly manufactured by chemical etching, electrochemical machining, cutting and form rolling. However, the chemical etching and the electrochemical machining are difficult to control 3D machining profiles with high accuracy. The cutting and the form rolling have problems in tool lives and manufacturing costs. On the other hand, blasting is expected as one of micro fabrication methods. Therefore, we focused on blasting, and have investigated its material removal capabilities by fundamental tests. The purpose of this study is to control machining profiles in cylindrical blasting. The machining profiles of cylindrical workpieces in blasting were simulated based on the material removal capabilities obtained by the fundamental blasting tests. Then, the simulated profiles agreed well with the experimental ones by blasting under the same experimental condition.

Abstract: The paper deals with evaluation of relation between individual parameters of roughness of the blasted surfaces by the correlation analysis. Based on the measured values on the surfaces which were blasted by various types of blasting devices, the correlation matrix was set and the standard of statistic importance of correlation between the monitored parameters was determined from it. The correlation coefficient was also set.

Abstract: Additive manufacturing technologies decrease production time and costs in engineering industry but also in other industries. Parts produced with Fused Deposition Modeling (FDM) have typical low surface finish quality. This paper is aimed on research of surface finishing technologies applicable to improve the quality of FDM prototypes surface finish. Pretreated samples were blasted with sodium bicarbonate and glass beads. The values of R_a and R_z were measured on the samples and compared the impact of selected pre-treatment, blasting medium and blasting conditions on surface finish quality of FDM prototypes.

Abstract: Put the first Phase Project of Qingdao Metro (line 3) civil 03 bid section TAI-YAN interval of blasting construction as the background In this paper,select the test section to blasting test,in groundposition on the ais of the tunnel workface arrange the measuring points and location of measuring points remain the same.Based on the measured data, studied on the law of blasting vibration of cutting parts of each of the driving cycle.The research result show that the cutting part of vibration velocity peak appeared in behind the tunnel woekface 1~3m;Rear vibration composite speed of the tunnel workface is speed of the tunnel workface is 1.0~1.4 times in front of the particle vibration composite speed;The main vibration frequency in front of tunnel workface and rear particles are above 15HZ.

Abstract: The development of railways brought a great era of tunnel construction in the 19^th century. One of the greatest obstacles for the railway between Bohumín and Žilina was the Jablunkov Pass. In 1869 the excavation of the first Jablunkov Tunnel started. In 1914 the second one came. However in the era of modern railway corridors these tunnels are no longer satisfactory, so a process of their modernisation was launched. Eventually the second tunnel was re-bored as a two-track tunnel. In 2007 the construction started, but in 2009 an exceptional event occurred, which significantly delayed the whole construction work. During the subsequent clearing of the cave-in a part of the tunnel from the northern portal remained in its definitive lining. Another part was temporarily secured with a concrete plug, while the original primary lining was reinforced with a railway bridge pier (PIŽMO). To get through the caved-in section and the concrete plug it was necessary to deploy blasting too. This created an opportunity to perform a unique experimental measurement of the impact of vibrations on the definitive lining from various sources (blasting and hydraulic demolition hammer). The generated vibrations might negatively affect the already finished definitive lining. All measurements were performed in amplitude and frequency area and the results were drawn as attenuation curves corresponding to the propagation of vibrations through the definitive lining construction.