Air Deck Research Articles

A Field-Scale Investigation into the Strategic Location of Air Decks for Improved Blasting Performance

A Field-Scale Investigation into the Strategic Location of Air Decks for Improved Blasting Performance

Application of Air Deck Method to Reduce the Impact of Ground Vibration and Optimization of Limestone Fragment Size in Blasting Activities at PT Semen Baturaja (Persero), Tbk.

The field experiment of applying the air deck method to the limestone blasting activities of PT Semen Baturaja (Persero), aims to reduce the impact of ground vibration considering that mining activities are approaching residential areas. In addition, the size of the fragmentation of the blasting results is very important for the effectiveness of the crushing plant. To determine the effectiveness of the application of the air deck method in limestone mining (quarry), blasting planning activities are carried out by dividing the two blasting locations, namely blasting with the air deck method and without using an air deck. By using a zig-zag blasting pattern and the number of holes of 50 Lb, the depth of the drill holes is 9 meters (without air deck) and 13 meters and the type of explosive used is Nonel. From the results of the analysis of limestone blasting with data processing using the split desktop 2.0 demo application, the ground vibration value (micromater system) was obtained. The average value of ground vibration (pVS) shows a smaller value using the air deck method of 0.68 mm/sec while without air deck of 0.74 mm/sec. The results of limestone fragmentation analysis with the air deck method obtained size <75cm reached 91.93%, while for without air deck it was 80.27%. These results show that the air deck method can be applied as a method to assist the Company in reducing ground vibration and limestone fragmentation effectively and efficiently by considering natural factors including geographical factors.

Analysis of Blast Fragmentation Results of the Top Air Decking Method in Coal Mines

This research aims to find out what influences the results of blasting fragmentation in the top air decking method. The method used in this research is a quantitative method. The data collection techniques used in this research came from literature studies and field data collection. Processing data analysis is carried out by considering several factors, such as rock characteristics, fragmentation results, and digging time results. After analysis, it can be seen that the design for determining the ADF, ADL, and stemming values is adjusted to the hole depth and PF used so that the fragmentation and digging time obtained are better in order to increase production activities. Based on the research results, it was found that the factors that influence the fragmentation results from top air deck blasting are the powder factor, blasting geometry (burden and spacing), air deck length (ADL), stemming depth, and wet hole conditions. The greater the PF value used, the smaller the fragmentation resulting from blasting and vice versa. The greater the ADL value used, the stemming depth will decrease and there will be potential for stemming injection and producing boulders. More holes in wet conditions will potentially result in greater fragmentation as well. The optimal ADF value to use is 0.3. With an ADF value of 0.3, the ADL used is 0.4–1.47 meters, resulting in better fragmentation. The previous boulder percentage of 18% changed to 7% and the previous digging time of 11.87 seconds changed to 10.57 seconds.

Numerical investigation on blast-induced rock fragmentation with different stemming structures

Stemming is one of the main concerns in blast of rock engineering due to its impact on explosion energy consumption and rock excavation performance. In this study, blast-induced rock fragmentation under different stemming conditions is numerically studied using combined numerical modelling and image processing. After careful determination the parameters of constitutive material models, the developed numerical model in LS-DYNA is verified based on the blast testing results including rock fracturing and fragment size distribution (FSD). The calibrated constitutive models are then used to model the pressure variation and rock disintegration produced by blasting with different stemming structures. The size data of simulated rock fragmentation are obtained by image-processing the cut surfaces of the numerical model with the program ImageJ, and the blast-created rock FSD is characterized using a three-parameter generalized extreme value function. The effects of the combination of explosive, air/sand deck and stemming on blast-induced rock fragmentation are quantitatively analysed, considering various stemming modes, stemming lengths and air/sand deck lengths. The results show that the blast-created fragment size decreases with an increase in stemming length, a decreasing in air/sand deck length, replacement of top stemming (stemming at borehole collar with air deck) with bottom stemming (stemming directly contact explosive) and alteration of air deck to sand deck, while the FSD range exhibits the opposite tendency. Bottom stemming is recommended for practical blasting due to its efficiency in rock fragmentation and robustness with respect to stemming length.

Blasting-induced rock damage control in a soft broken roadway excavation using an air deck at the blasthole bottom

Blasting-induced rock damage control in a soft broken roadway excavation using an air deck at the blasthole bottom

Comparison and application of top and bottom air decks to improve blasting operations

<abstract> <p>The blasting operation is an integral part of mines, and it is still being used as the most economical tool to fragment and displace rock mass. Appropriate blast optimization alleviates undesirable side effects, such as ground vibration, air blasts and flyrock, and it and enhances rock fragmentation. Blast optimization can also be effective in reducing the overall mining cost. One way of reducing blasting side effects is to use deck charges instead of continuous ones. The location of the deck(s) is still considered an unanswered question for many researchers. In this study, an investigation was carried out to find an appropriate air deck position(s) within the blast hole. For this, air decks were placed at three different positions (top, middle and bottom) within a blast hole at Cheshmeh-Parvar gypsum and Chah-Gaz iron ore mines to understand and evaluate air deck location impact on blast fragmentation and blast nuisances. The results were compared based on the existing blasting practices at both mines, as well as the air-deck blasting results. The results obtained from the blasting were very satisfactory; it was found that charging with a top air deck, as compared to current blasting practices, causes a decrement in the specific charge, as well as a decrement of 38% in the back break and 50% in flyrock; the average size of fragments obtained from blasting was increased by 26%. Thus, it can be said that the top air deck is more advantageous than the bottom air deck in terms of reducing undesired blasting consequences.</p> </abstract>

Optimization of the Air Deck Blasting Parameters on the Basis of the Holmquist-Johnson-Cook Constitutive Model

The present study considers the so-called air deck blasting, one of the most commonly used techniques for the improvement of blasting efficiency in mining applications. In particular, it aims to improve the operating conditions of large-scale equipment, increase the efficiency of the slope enlarging process, and reduce the mining cost. These objectives are implemented through a two-fold approach where, first, a program for slope enlarging based on the middle air-deck charge blasting-loosening technology is proposed, and second, the physical mechanism responsible for the stress wave attenuation in the rock is analyzed in the framework of a Holmquist–Johnson–Cook constitutive model. Field test results verify that the proposed approach is highly efficient and economical when used in medium-hard rock blasting and thus provides a basis for the practical implementation of slope enlargement for high benches in Open-Pit Mines.

Effects of Axial Air Deck on Blast-Induced Ground Vibration

Effects of Axial Air Deck on Blast-Induced Ground Vibration

Study on the effect of air deck on ground vibration and development of blast damage zone using 3D discrete element numerical method

Study on the effect of air deck on ground vibration and development of blast damage zone using 3D discrete element numerical method

Analysis Of The Effect Of Blasting Pattrerns On Ground And Building Vibration Levels Around The Mine At Blasting In Pit 2 Banko West PT Bukit Asam Tbk tanjung Enim, South sumatera Province

PT Bukit AsamTbk is one of the coal mining companies in Indonesia that uses an open pit mining system. Demolition of B2-C overburden rocks at the location of electrification mining in Pit 2 Banko Barat is not economical if it is doing by ripping-dozing process so that drilling and blasting activities are carried out. After blasting activities, ground vibration will arise as an effect of the blasting. It is known that the distance of the blasting location with the residential area is at a distance of 1350-1800 m for this reason that vibration measurements must be carried out with the Blasmatet III device. Ground vibration is one of the problems that must be minimized so that the ground vibration level is in accordance with SNI 7571; 2010 did not exceed the vibration threshold that could cause damages, especially for residents. The ground vibration level can be controlled in various ways such as setting the point initiation point, setting the delay time with a higher value, planning the powder factor and finally using the Air deck method. Based on research carried out for 60 days with blasting 17 times which produces different vibrations. The vibration value used for the comparison of the effects of the blasting pattern is used in 6 data, 3 data for the Box cut blasting pattern, which are 0.52, 0.53, 0.56 and for data on the Corner cut blasting pattern which is 0.63, 0.69, 0.73. While for the comparison of data using Air deck, 6 data are used, 3 values of the results of the vibration of the water deck method are 0.73, 0.69,58 and for non-Air decks the results of the vibration are 1.17, 1.05, 0, 88. Calculation of the results of the comparison of the vibration comparison using the delay time there are 6 data used, namely 3 with a delay time of 42 & 67 with the results of vibration, namely, 0.58, 0.69, 0.73 while the delay time 42 & 109 the result of vibration is 0.50, 0.56, 0.58. Of the overall soil vibration values, settlements around the blasting area are in the safe category (PVS <3 mm / s).

Air Decks in Surface Blasting Operations

In this study, the best possible location for an air deck in an explosive column during a surface blasting operation for the most efficient rock fragmentation is described. Volumes of air decks are proposed for the optimization. This study aims at helping guide blasting engineers to easily apply an air deck in a surface blasting operation.

Influence of Air Gap Volume on Achieving Steady-State Velocity of Detonation

The velocity of detonation (VOD) is a significant property considered when rating an explosive. It may be quantified as a confined or unconfined velocity. The confined velocity is the rate at which the detonation wave propagates through an explosive within a blast hole or any restrained space. The unconfined velocity emanates when an explosive is detonated in the open. However, the confined velocity is more significant as explosives are usually employed under a definite degree of confinement. This paper evaluates the increment of air deck volume and its effect on the VOD. The air gap (air deck) volume is increased stepwise from 10 to 30% of the total blast hole volume by reducing the stemming height in the collar zone. Thereafter, the VOD estimation in the 172-mm-diameter explosive column is conducted using the Dautriche technique. It is observed that the VOD reduced with the increasing air deck volume and detonation failure is high when 30% of the blast hole volume is replaced with air deck. It is deduced that the increment of the air deck volume has an effect on the attenuation of the steady-state VOD.

Air Decks in Surface Blasting Operations

Air Decks in Surface Blasting Operations

A study of cut blasting for one-step raise excavation based on numerical simulation and field blast tests

Over the past several decades, raise excavation has been widely employed in underground mining, civil engineering and military engineering. One-step raise excavation with burn cuts, where all the boreholes are pre-drilled and detonated at one time and no workers need to be underneath the freshly blasted and dangerous ground, is an important and promising method in raise excavation. Cut parameters, especially the parameters of prime cut which used empty hole as a free surface and swelling space, have significant influence on the effect of raise formed. In this study, two small-scale experimental methods, spiral hole spacing method and observation hole method, are designed to determine the prime cut parameters such as hole spacing (L), stemming length (Ls1, Ls2) and air deck length (La) which are normally determined by empirical formula. In order to study the feasibility of the two methods, numerical analysis and experimental tests are conducted in V zone of Sandaozhuang molybdenum mine (SMM), in which there are large numbers of underground goafs need to be controlled by filled raise. The Riedel–Hiermaier–Thoma (RHT) material model, which considers compression damage and tension damage effect under blasting loading, is employed in the LS-DYNA software to study the rock damage zone. Meanwhile, the field tests are carried out according to the two small-scale experimental methods. The comparison results show that the damage zone of numerical simulation has a good agreement with the experimental data. Further, the optimal prime cut parameters obtained from experimental tests are applied in one-step filled-raise excavation, and a 23 m raise that meets the design requirements is formed through the proposed technology. The results indicate that these cut parameters determined by the small-scale experiments are suited for one-step raise excavation. This study can provide two simple field experiments to determine the important prime cut parameters of one-step raise excavation.

Stemming zone fragmentation analysis of optimized blasting with top-column air decks

Stemming zone fragmentation analysis of optimized blasting with top-column air decks

Improving Collar Zone Fragmentation by Top Air-Deck Blasting Technique

Air gap in an explosive column has long been applied in open-pit blasting as a way of reducing explosive charge, vibration, fly rock and improve fragment size. In conventional blasting a greater amount of explosive energy is lost in the generation of oversize fragments. Oversize fragments reduces loading and hauling efficiencies of equipment which requires secondary blasting. Recurring oscillation of shock waves in the air gap increases the time over which it acts on the adjacent rock mass by factor of 2–5. Top air deck blasting technique trial conducted with an application of gas bags at Chimiwungo pit resulted in an improved fragmentation of about 94 % less than 950 mm. Results obtained from the analysis of muckpile images using split-desktop exhibited that the mean fragment size was 264.81 mm and F20, F80 and top-size were 41.99, 683.18 and 1454.69 mm respectively. Optimum crusher feed size was as large as 1200 mm and crushed down to the 40 mm and only a small percent of the material was above 1200 mm. Gas bag application resulted in a significant reduction in explosives load in production holes without loss in fragmentation or movement of the collar zone. This reduced total cost of charging as compared to conventional blasts with a variance of $20, powder factor was dropped to an average of 0.86 kg/bcm. The technique reduced the cost of bulk blend explosive by 15 %, reduced overall cost of charging per hole by 12 %, enhanced premature ejections. The overall blast results were satisfactory, 443,624 tonnes of blasted material from the block which represented 90 % of the total muckpile material was within 900 mm size. The overall muckpile blasted was well fragmented.

비파괴 검사를 이용한 항공 갑판의 결함 검출

본 논문에서는 비파괴 검사를 통하여 얻어진 항공 갑판 영상에서, 조직의 결함의 정도를 자동으로 검출하는 방법을 제안한다. 먼저 비파괴 검사를 통하여 얻어진 항공 갑판 영상에서 감마상관 변환과 7<TEX>${\times}$</TEX>7 소벨 마스크와 13<TEX>${\times}$</TEX>13 소벨 마스크를 각각 적용하여 윤곽선을 추출하고 추출된 윤곽선 영역을 평활화와 평균 이진화 기법을 적용하여 영상을 보정한다. 마지막으로 보정된 영상에서 침식 연산과 팽창 연산을 이용하여 잡음을 제거한 후, 라벨링 기법을 적용하여 항공 갑판의 결함 영역을 추출한다. 실험 결과에서, 항공 갑판에서 결함을 추출하는데 기존의 방법보다 효과적인 것을 확인하였다. In this paper, we propose an effective method that automatically detects flaws in air deck by using non-destructive testing. First, Gamma correlation transform, 7 <TEX>${\times}$</TEX> 7 and 13 <TEX>${\times}$</TEX> 13 Sobel mask apply to the image of air deck acquired non-destructive testing in order to detect the edge of the image. Second, the edge detection area is smoothed and corrected by mean binarization method. Finally, the region of flaws in air deck is detected by a labeling method after removing the noise by the erosion and the dilation operation. In experimental results, we showed that the proposed detection method is effective in air deck.

Storm Warning

This article focuses on measures for preventing damages to oil drilling setups post hurricanes or typhoons. According to engineers, today, it is a complex network of fixed and floating production platforms, mobile drilling units, undersea wells, and oil and gas pipelines. No single solution will ensure the safety of the entire system. The exploration wells under the drilling rigs are also vulnerable. Mobile drilling units, such as jackups and semisubmersibles, which drill test wells and then move to another location, proved especially vulnerable during Katrina and Rita. When the American Petroleum Institute rolled out its first post-Katrina recommendations in April, it took an initial step on a road that will eventually demand changes in everything from air gaps, tie-downs, and deck design to moorings, tethers, clamps, and piping supports. New standards are expected to improve the odds for newer platforms and rigs if they continue to face larger and larger hurricanes.

Borehole pressures in an air decked situation

In the late 1970s and early 1980s in conjunction with other oil and gas well stimulation studies, personnel from the Dynamic Effects Laboratory performed model testing to demonstrate the effectiveness of utilizing an open section of borehole just before a plug. We called the process stem induced fracturing. The open section beneath the stem was used to increase the pressure magnitude and spread out the duration of the pressure pulse. This technique was later utilized by Frank Chiapetta [Chiappetta, R.F. and Mammele, M.E., 1987, Analytical high-speed photography to evaluate air decks, stemming retention and gas confinement in pre-splitting, reclamation and gross motion applications. Proceedings of 2nd International Symposium on Rock Fragmentation by Blasting, Keystone, Colorado, USA, 257 – 309] in the fracture and fragmentation of rock in quarry blasting situations. He called his technique air deck blasting. In fact, Frank found that the Russians had previously discovered the same technique. There is curre...

A Further Study on the Mechanism of Airdecking

Airdecking is used in mining for two quite different applications. One is to enhance the fragmentation by amplifying the induced fracturing and the second is for pre-split blasting in which the borehole fracturing is reduced. This paper deals with the first of these effects. A forth coming paper will describe pre-splitting by airdecking. The use of air decks to enhance rock fragmentation and so to reduce explosive costs has been the practice for quite long time. Although a number of studies has been conducted to verify the advantages of blasting with air decks and to investigate the mechanisms involved, the proposed mechanisms still cannot explain clearly the phenomena observed in practice and the design approach adopted for this kind of blasting is still primary based on rules-of-thumb. In this paper, the theory of shock tubes is adopted to (a) investigate the processes of the expanding detonation products, (b) study the interactions between the explosion products and the stemming or bottom of blasthole, and (c) to decide the distribution of the changing pressure of explosion products along blasthole. Numerical simulation and theoretical analyses are then performed to study the physical process of blasting with air decks. Finally, a reasonable value for the airdecking ratio is decided theoretically. It is shown that the pressure-unloading process caused by the propagation of the rarefaction wave and the reflected rarefaction waves in the detonation products plays an important role in the enhanced fragmentation of rock when blasting with air decks. The unloading process can induce tensile stresses of rather high magnitude in the rock mass surrounding blasthole. This favors fracturing of the rock. The reflected shock wave with a magnitude of gas pressure higher than that of the average detonation pressure in a fully charged blasthole acts as the main energy source to break the rock in the air deck and stemming portions. The second and succeeding strain waves induced by the unloading or reloading of the pressurewithin the blasthole also contribute to form the initial fracture network in the rock around the blasthole. It is also revealed that there exists a reasonable range of values for the airdecking ratio. For ANFO, this value varies from 0.13-0.40.