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  • 1. Assessment of explosive performance by detonation velocitymeasurements in TurkeyA. Bilgin & S. EsenDepartment of Mining Engineering, Middle East Technical University, Ankara, TurkeyABSTRACT: Real performance of an explosive can be determined by conducting continuous velocity ofdetonation (VOD) measurements in full scale blast environments. This paper presents and discusses the res-ults of continuous VOD measurements of five different blasting agents carried out at three mines in Turkey.The results show that VOD of a blasting agent varies depending on mainly the rock properties (confinement),presence or absence of sensitizer (chemical formulation), blasthole diameter, and type of primer. The methodof continuous VOD measurement is an indispensable and invaluable tool in explosive and primer selection.1 INTRODUCTION specific rock and test conditions. Since VOD is a direct measurement of the source function, it canBlast optimization studies attract more attention than provide valuable information with respect to shock,before due to increasing economical pressures. stress waves, kinetics, ground vibration, airblast,Inadequate blast designs besides environmental fragmentation and undesirable noxious fumes. Ifhazards can cause decreased efficiencies in loading, VOD is not monitored and an explosive product ishauling, crushing and grinding cycles and lead to assumed to perform as specified, the interpretationincrease in the unit cost of overall operation. A blast of other measurements (if any) could be erroneousdesign implemented according to the site specific when product malfunction occurs. Thus, it isconditions and mine objectives may decrease overall important to correlate the product’ VOD soperation cost together with provision of safety and characteristics to the rock environment, blast design,elimination of environmental hazards. and other measurements (Chiappetta 1993 & 1998). With new PC based blast monitoring Field VOD measurements were performed with ainstrumentation systems and recently introduced continuous VOD recorder (VODR-1) developed bynew analytical methods of analysis, the operator can EG&G and BAI. The VODR-1 is a commercialeasily eliminate most of the guess work involved in version of the CORRTEX system, which wasdesigning efficient blasts and in evaluating explosive originally developed by Los Alamos Nationalperformance in any mining environment (Chiappetta Laboratory (USA) to measure shock wave1998). propagation in nuclear tests to determine nuclear Within the scope of a research and development explosive yield. In the measurement of explosiveproject on explosives and blasting techniques, over performance, a coaxial cable is placed in an70 continuous VOD measurements were conducted explosive filled borehole with the far end of theat seven different blasting sites till now. However, cable taped on the primer. Operation is similar tothis paper presents a summary of continuous that of RADAR where a pulse of radio waves is sentvelocity of detonation (VOD) measurements out and an echo or reflected pulse is returned to giveconducted at only three mines. It is intended to ranging information. The VODR-1 uses standardinvestigate the performance of five different blasting coaxial cables to carry a fast rise time electricalagents in full scale in three mines having different pulse back and forth every 5-200 µs. Displacementrock types and its impact on the blast results. versus time data can be obtained for the entire length of explosive column and the stemming region to determine explosive VOD, cap timing, shock wave2 VOD INSTRUMENTATION transmission, etc. (Chiappetta 1993, Bilgin & Esen 1999).Velocity of detonation of an explosive can be usedto evaluate the performance of a product under
  • 2. 3 CASE STUDIES Displacement, mThree case studies are included in this paper. These 45.10are Etibak r Küre Copper Mine which is an open pitmine, Ba ta Limestone Quarry and Yeniköy OpenCast Coal Mine. Continuous VOD measurements in 42.84these full scale blast environments are presented. Five different blasting agents namely ANFO, ElectronicELBAR-5, BARANFO 50, ELBAR-100 and 40.57 NoiseBARANFO 100 are tested. ANFO is a locallyprepared one using porous prills of ammoniumnitrate (AN), whereas the other four are produced at 38.31factory. ELBAR-5 is a slightly sensitized ANFO.ELBAR-100 is a water resistant ANFO that containssome sensitizer and water proofing agent. 36.05BARANFO 50 is produced partly by using porousprills and partly by crushed AN. BARANFO 100 isconsisting completely of porous prills of AN. These 33.79blasting agents are basically ANFO having different 1.12 1.93 2.74 3.56 4.37 5.18ammonium nitrate size and type and/or sensitizer. Time, ms Figure 1. Zoomed-in raw VOD record for ANFO.3.1 Etibak r Küre Copper MineVOD measurements were conducted while blasting - the start-up VOD at the hole bottom is 2525 m/smassive copper ore which was classified as high (Fig. 2).strength rock. Performances of four blasting agents - low order detonation at the hole bottom results(ANFO, ELBAR-5, BARANFO 50 and ELBAR- from poor priming and causes toe problem.100) are evaluated by these measurements. Blast - average VOD of ANFO is 4141 m/s.design parameters are given in Table 1. - poor fragmentation is observed by qualitative ANFO and Powergel Magnum (an emulsion visual analysis of the muckpile. It is due to theexplosive, 90x200 mm) were the blasting agent and poor detonation performance of ANFO at theprimer respectively in the first test. A single hole is hole bottom, and improper drilling pattern. Later,monitored by VODR-1 system. A zoomed-in raw by changing the drilling pattern to 3.5 m x 5.5 m,VOD record is illustrated in Figure 1. fragmentation is improved by blast optimization The following results were obtained by analyzing studies (Esen et al., unpubl.).the single hole record and from observations: - bad muckpile profile resulting from the blast- run-up distance (the length of explosive column causes difficulties in loading operation. detonating at low velocity and measured from - a few number of electronic noise in the VOD the point of initiation to the point where steady record shown in Figure 1 indicates quite clearly state VOD is reached) is 1.47 m. that the rock mass surrounding the length of the explosive column was quite intact with very minor structural discontinuities and no softTable 1. Blast design parameters at Etibak r Küre formations. Copper Mine. VOD measurements for ELBAR-100, BARANFO 50 and ELBAR-5 were carried out to select the best Blasthole diameter 159 mm blasting agent for the mine. These explosives were Bench height 12 m charged into 3 different holes in the order given Hole depth 13.5 m above. These were primed by Gelatinous Dynamite Burden (B) 3m (90x100 mm) and initiated by shock tube. A single Spacing (S) 3m row consisting of three holes is prepared for VOD Stemming length 4.5 m measurements and a different blasting agent is Blasthole inclination Vertical charged into each hole. The results of the Charging configuration Bottom priming, measurements are given in Table 2. continuous charging The following results were obtained from three Blasthole pattern Square hole, one row shot VOD record and from Initiation system used Shock tube observation: Initiation pattern Square V - high VOD recorded at hole bottom in each blast- Delay between rows 25 ms hole indicates good priming of ANFO. So, Gelatinous Dynamite is a suitable primer.
  • 3. VOD, m/s Time, msFigure 2. VOD-time graph of raw VOD record for locally prepared ANFO.Table 2. Comparison of VOD results at Etibak r the explosive column, but the decrease is not Küre Copper Mine. much and seems acceptable. - The minimum reduction in VOD is obtained for ANFO EL- BAR- EL- the explosives BARANFO 50 and ELBAR-100 BAR- ANFO BAR-5 (Table 2). 100 50 Explosives having high VOD and low attenuationDensity, 0.810 0.994 0.928 0.803 in VOD are generally preferred for massive highg/cm3 strength rocks. So, the most suitable blasting agentPrimer Power- Gel. Gel. Gel. for this blast environment is BARANFO 50 and/or gel M. Dyn. Dyn. Dyn. ELBAR-100. Since ELBAR-100 has higher VOD,Average 4141 5041 4832 4184 density and unit price, it may be utilized as bottomVOD, charge, whereas BARANFO 50 may be used asm/s column charge. ANFO consisting completely ofVOD at 2525 5163 4859 4379 porous ammonium nitrate prills is not recommendedhole bot- as a blasting agent for this mine as it has lower VODtom, m/s and density and much greater reduction in VODVOD at 3810 4871 4782 3983 along the explosive column.the top of A research study conducted by Esen et al. (2000)explosive has shown that coarser fragmentation is obtained bycolumn, utilizing ANFO containing only porous AN prills inm/s hard rock environments due to its lower shock energy. Blasting agents with high shock energy (high VOD and density) such as BARANFO 50 and- Due to high VOD at hole bottom, no toe problem ELBAR-100 are recommended in these blast en- was observed during and after mucking. vironments. Blasting agent selection based on the- Figure 3 shows VOD-time graph for the second VOD measurements agrees well with the findings of hole where BARANFO 50 was the blasting Esen et al. (2000). agent. VOD is not constant and decreases along
  • 4. VOD, m/s Time, ms Figure 3. VOD-time graph of BARANFO 50 at Küre Copper Mine.3.2 Ba ta Limestone Quarry records are evaluated, high VOD at the hole bottomPerformances of blasting agents ELBAR-5, is observed showing good priming of the blastingBARANFO 50 and ELBAR-100 are evaluated by agents tested. ELBAR-100 and BARANFO 50 areconducting VOD measurements also at Ba ta suggested for parts “ and “ as” uy” respectively byLimestone Quarry at two different blasthole considering the measured velocities (Table 3).diameters (89 mm, 165 mm) and at two separate Proper selection of blasting agent and primer haveparts of the quarry coded as “ and “ as” uy” which led to good fragmentation and elimination of toewere classified as high strength and medium strength problems at the quarry.rocks, respectively. Results of the VOD meas-urements are shown in Table 3. 3.3 Yeniköy Open Cast Coal Mine It is proven once more that VOD of a commercialexplosive material varies depending on hole VOD measurements were also conducted at Yeniköydiameter and confinement (Table 3). When the VOD Open Cast Coal Mine to evaluate the performances of ELBAR-5, BARANFO 50 and BARANFO 100 in weaker rock environments. Measurements wereTable 3. VOD results at Ba ta Limestone Quarry. conducted at kizköy District of the mine where . stripping operations were carried out. Marl is the Blasting Hole Dia- Rock Average principle rock type blasted during overburden Agent meter, mm Definition VOD, m/s loosening which is subsequently removed by shovelElbar-5 89 as 3240 truck combination. It is classified as low strength 165 as 4268 rock. Blasthole diameter, burden, spacing and hole 165 uy 4171 length are 235 mm, 9 m, 9 m and 9.6 m,BAR- 89 as 3735 respectively. 100 kg blasting agent is charged intoANFO 50 165 as 4588 each blasthole. Blasting agents tested were primed 165 uy 4229 by either 100x90 mm Gelatinous Dynamite orElbar-100 89 as 4017 90x150 mm Powergel Magnum cartridges. Results 165 as 4900 of the VOD measurements are given in Table 4. 165 uy 4749
  • 5. Table 4. Results of the VOD measurements at 4 CONCLUSIONS Yeniköy Open Cast Coal Mine. 1. VOD of a blasting agent depends heavily onBlasting Primer Average Run-up formulation characteristics, rock propertiesAgent VOD, Distance, (confinement), blasthole diameter and priming. m/s cm 2. A VOD record can provide excellent informationELBAR-5 Gelatinous 4550 - on the integrity, structural and geomechanical Dynamite condition of the surrounding rock mass.ELBAR-5 Powergel 3895 35 3. When an explosive is primed adequately, VOD Magnum at hole bottom is high and decreases towards theBARANFO Gelatinous 4675 - end of the explosive column. So, VOD of a50 Dynamite commercial explosive is not constant.BARANFO Powergel 4350 62 4. Low VOD at the hole bottom indicates poor50 Magnum priming of blasting agent. Inadequate primingBARANFO Gelatinous 4175 - creates low order detonation resulting in poor100 Dynamite explosive performance at the hole bottom. ItBARANFO Powergel 3811 38 leads to hard toe (difficult digging) and coarse100 Magnum fragmentation. 5. BARANFO 100 is the most suitable explosive for the low strength rocks of Yeniköy Open Cast Bulk densities of ELBAR-5, BARANFO 50 and Coal Mine. BARANFO 50 is the most properBARANFO 100 are 0.803, 0.928 and 0.714 g/cm3, explosive in blasting medium strength rocks.respectively. Higher VOD (higher shock energy) and higher The following conclusions are drawn both from density explosives such as ELBAR-100 andTable 4 and field observations: BARANFO 50 having low attenuation in VOD- no run-up distance is measured when blasting are proven to be suitable for blasting operations agents are primed by Gelatinous Dynamite in hard rock environments such as seen in showing adequate priming. The initial high VOD Etibak r Küre Copper Mine. at the hole bottom proves that Gelatinous 6. Since performance of primer and blasting agent Dynamite is a suitable primer. affect blasting results, selection of explosives- run-up distances were measured only when should be made properly for each blasting site. Powergel Magnum (an emulsion explosive) is VOD measurement carried out at full scale is an used as a primer. Therefore, Powergel Magnum excellent and indispensable tool for the selection. is not as good as Gelatinous Dynamite as a 7. VOD measurements conducted during full scale primer. blasting certainly offers important information to- presence of run-up distance indicates poor be used in blast design optimization and the performance of the blasting agent at the hole bot- detection of low order detonation, deflagration tom. For example, run-up distance of and misfire. BARANFO 50 due to poor priming is 62 cm, that is, about 25 kg explosive is wasted during detonation. REFERENCES- low VOD at the hole bottom causes low productivity in excavation during stripping Bilgin, H.A. & Esen, S. 1999. Assessment of the operation. The result is an economical loss for performances of some commercial explosives in the mine. blasthole at Ba ta Quarry. The 2nd National- type of primer affects the detonation velocity Aggregate Symposium, Istanbul, Turkey: 157-168 even if the explosive type, the rock type, the (in Turkish). diameter of the hole and the initiator are the Chiappetta, R.F. 1993. Continuous velocity of deto- same. Average VOD’ of BARANFO 50, s nation measurements in full scale blast BARANFO 100 and ELBAR-5 primed by environments, Proceedings of the International Gelatinous Dynamite are 4675, 4175 and 4550 Congress on Mine Design, Kingston, Ontario, m/s, respectively. That of these explosives Canada: 759-785. Rotterdam: Balkema. primed by Powergel Magnum are 4350, 3811 Chiappetta, R.F. 1998. Blast monitoring instrumen- and 3895 m/s, respectively. tation and analysis techniques, with an em- Explosives having low VOD and density are phasis on field applications. FRAGBLAST-generally preferred in low strength rocks. Therefore, International Journal of Blasting and Fragmenta-BARANFO 100 is selected for stripping operations tion, Vol.2, No. 1: 79-122. Rotterdam: Balkema.of the mine due to its low VOD and density. Esen, S., Bilgin, H.A., Erkoç, Ö.Y., pek, T. & Al- da , G.G.U. 1999. Report on experimental blast-
  • 6. ing studies at Etibak r Küre Copper Mine. An- kara, Turkey. 10 pages (unpublished report in Turkish).Esen, S., Bilgin, H.A. & BoBo, T. 2000. Effect of explosive on fragmentation. The 4th Drilling and Blasting Symposium, Ankara, Turkey: 63-72 (in Turkish).