安全连续采矿的非爆破破岩技术毕业论文外文翻译

1、Non-explosive Rock Breaking Technologies for Safe andContinuous MiningKey words：Mining Consultant，Yonke Services (Pty) Limited，31 Impala RoadChislehurston，Sandton，Johannesburg，RSAABSTRACT ：Several mines in South Africa (SA),like in many other parts ofthe world, use drill and blast as means of rock b

2、reaking for ore extraction. Despite cost effectiveness high explosive mining does not guarantee optimal total mining costs.Its low energy efficiencies and the hazardous nature of blasting, i.e. poor safety records especially in deep mines, create a need for intensive reseach and development into saf

3、er and more productive technologies. Surely mechanised mining is the ultimate option. Many attempts to use heavy machines in narrow vein deposits at great depths have however resulted in disappointment. Over the last three years, the quest for nonexplosives breaking technologies has gained momentum.

4、 The industry is desperately looking for a face saving system to uplife productivity , ensure safe mining underground, prevent and damaged-control the impact of the devastating HIV/AIDS on the future of mining. Propellant based non-explosive rock breaking is positioning itself so as to capture the o

5、pinion in the industry. It is considered a midway between cheaper but life-threatening explosives and the capital intensive and uncompromising mechanised mining.Many non-explosive products being trailed in the industry:Swartklips Boulder , Rocksplitter,Brandrills PenetrationConeFracture(PCF),NXCOs N

6、onex and Altex s Safex toname a few . Allthese systems have unique merits and they all claimdifferentlevelsof success in breaking rock under varying conditions, however theyall lack the Herculean power (Cunningham 2002),“the oomph ”,toproperlyclean out the rock burdens consistentlytothe satisfaction

7、of the industry . Fundamentally these systems appear to lack in containing the blast gas energies in the rock to mature burden第 1 页fracturing. Rockdusters and Conmin 101 are the newest products tomake an appearance . They claim to have addressed this shortcomingwith contept. They still have to prove

8、 in practicaltrials whatappears like an obvious edge over precursors, that capacity ofholding gases in blastholes for long duration. Ever though theindustry expectation of continuous mining operationts is still adram , as non-explosiveminingtechnologiesdevelopedtodate ,havenotsucceeded todemonstrate

9、such capabilities. Thispaper intendstodiscussthe advantages ofnon-explosiverockbreakingsystems andtopresentsome resultsof trialblaststohighlight theway forwardtowards achievingcontinuousmining ,improved healthand safetyandhigher productivity that impacts on the industry bottom lines.1INTRODUCTIONDri

10、ll and blast technology has indisputable merits of breaking the rock. However it is always associated with major health and safety concerns owing to direct aftermath side effects such noise, fly rocks, toxic fumes, dust, high concussion, accidental detonations and management of misfires. Indeed, the

11、 SA industry has managed to scale down and manage these hazards relatively well, given the risks involved and the statistics of accidents recorded to date. However since human life should be rightly valued, the national expectance is zero accidents at any cost. Thus the reason for this quest by all

12、concerned parties is to work towards a safer mining system that ensures sustainable mining to well take the industry into the future. Cunningham (2002) highlights the major shortcoming of conventional high explosive mining. He observes that underground ore production is limited by disruption of oper

13、ations imposed by mining legislation associated with blasting. Full shift continuous operations are impossible owing to the withdrawal time required. Workers vacate the workings shortly before and during blasting. There is a working prescribed re-entry period that ought to be observed while blast fu

14、mes, noxious gas and dust settle. Non-explosive rock breaking systems claim the advantage of no concern with such huge loss of working time. Several systems have been developed and put forward to the industry. Despite their subtle differences warranting their individual patents, they all have in com

15、mon the following claimed features:第 2 页Non-explosive low concussion rock breakingLess fines and dust generationImproved hanging wall conditions due to low concussionLow toxic fumes, enabling immediate re-entry and continuous mining.2NON-EXPLOSIVE ROCK BREAKINGSA mining industry has one of the highe

16、st rate of mining casualties in the world mainly due to the great depth of mining (2 to 3 kilometres under the ground, ever more ). The unique geotechnical rock conditions are generally characterized by heavily fractured rock in stops and haulages as well as a highlysesmic active ground conditions.H

17、igh explosive mining doesadd to the groundconditionsdescribed above another safety concern thatisbornout of theenormousenergy generated byblasting,whichis oftenpoorlyaccountedfor.Considerable portion of blast energy remains locked up inhanging walls ofmining excavations.Without priorwarning such ene

18、rgycomes down oftentriggering bloody falls of ground that frenquentlyresult inaccidents varying inintensity from small cuts to multiple fatalities .Tabulated below are statistics of accidents recorded in SA mines for a period of nine years from 1990 to 1999.Table 1. Statisics of high explosive relat

19、ed accidents in SA mines.SA mines accident statistics fromTotalTotalTotalTotal90-99injureddisabledkilledaccidentsFall of ground1728699154718229Misfires12432997Exposure to blasting fumes00417Other explosive related accidents180Table 1(above)depicts thehorrendousrealityofSA miningindustrythat maybe su

20、mmedup inthefollowing:Everysingleyearhighexplosives in theindustrycause death tooverone hundredand fiftypeople,injureoverone thousand eighthundred people and inflic permanent disability to some ten people.This is the第 3 页scenariothatnon-explosiverock breakingtechnologiesintendredressingbesidethe add

21、ed advantage of increased production rates.Path and underlyingprinciplesof non-explosiverock breakingsystemsImpact miningIn the early nineties, the mining industry witnessed an eagered search for paradigm shift in mining underpinning intensive reaserch for safer and more productive rock breaking tec

22、hnology for narrow reef mining. The trend was fuelled by the need for substituting the inherent disadvantagesof conventional labour intensive method of drilling holes and detonating violently chemicals into the rock to extract portions of orebodies. In already difficult ergonomical conditions, i.e.

23、deep mine heat load, highly stressed rock and confined spaces, explosions are always perceived to sensibly obscure the positive contribution of the industry. Financial Mail, September 1993 reports that impact mining considered revolutionizing mining since the eighties. Intitial exploratory trials we

24、re carried out at Doornfontein mine. Number of mines which followed suite to pioneer the process, i.e. Kloof Mine, claimed an upper hand for the technology as it yielded lower working costs and high production rations. However the technology was not further developed owing to its lack of flexibility

25、 associated with high level of mechanisation. So despite being non-explosive impact mining was seen as part of drive towards mechanized-mining in deep mines, which falls outside the scope of this paper.NXCOs Nonex technologyNonex technology is also based on the use of a propellant cartridged in a dr

26、illed hole and stemmed by aggregates (stemming column) to fill the blasthole. This system claims to have substantially improved the geometry and nature of the stemming material used to confine the propellant in the hole therefore resulting in a much better in-hole confinement of gas energies. In add

27、ition Nonex cartridges are 100 non-explosive and totally inert. Ignition is obtained by low voltage electric power a part from which any other means would completely fail to set off the cartridge, hence its extreme safety in handling and transportation.The Nonex cartridge system works on the princip

28、le of a balloon to seal off the hole and avoid premature gas escape during the pressure build-up. This is a第 4 页considerable advantage as escaping gas compresses air at the interface cartridge/rock/stemming, interfering thus with the pressure build up in the hole. Indeed, the gas fills the annular s

29、pace around the cartridge as well as filling all the new openings generated by induced and/or in situ fractures, thus lowering the pressure in the blasthole. In a non-expanding cartridge, the pressure is further lowered by the movement of the stemming in response to the slow pressure build-up in the

30、 hole. In principle, the build-up of pressure should be fast enough so that inertia prevent appreciable stemming movement during the critical period of gas advance into the rock fracture network. The slow pressure build-up, on the other hand, results in an early release of gas from the hole before t

31、he rock fracturing process is completed. Work by Ozbay (1982), and other earlier works, ascertained that the fracturing process in hard rock requires some 3 to 10 microseconds to complete. The Nonex cartridge is provided with a pressure release valve that is activated on ignition, inflating the cart

32、ridge to seal off the hole and keeping the pressure within the hole for as much time as the rock needs to crack before the release. The system greatly reduces the probability of cartridge malfunctioning in the blasthole. An additional advantage is that ever in the case of malfunction,a Nonex charged

33、 blasthole could be drilled into by the rockdrill without danger of detonation. There is no potential danger as the cartridge and the igniter are both non-explosives. One cannot talk of misfire in this case; rather a malfunctioning that can easily be remedied.ALTEXs SAFEX technologyOriginally from S

34、cotland this technology is claimed to be suitable for both secondary and primary rock breaking in surface as well as underground mining. It is a relatively new product in the industry and so it has not attracted much interests. It is based on the use of drilled hole in which a special propellant car

35、tridge is charged in a bottom-priming configuration. The blasthole is stemmed with sand and a double chemical concoction, which mixt with the sand to from a sort of paste in the hole. The paste expands to fill up the section area of the hole and dries quickly into a plug that seals tightly the hole.

36、 The propellant charge isinitiated by an AEL made ele ctrical/combustion igniter named sure start . Ibasically an electrical fusehead that is made to set off normal igniter cord forcombustion initiation. Safex field trials conducted at a chrome mine as well as at第 5 页a platinum mine respectively in

37、the Eastern and Western Bushveld did not yield conclusive evidence to warrant recommendation of the system for routine mining. As in any R&D, the product is being improved (back to the drawing board) for further attempts.Salient features of non-explosive rock breakingThe learning curve of non-explos

38、ive rock breaking technologies has been steep since they are meant to compete with settled high explosives that have built the mining industry wealth and reputation over many years.It is against this background and the general conservatism that riddles the industry that the new comers have to battle

39、 .Whatever the standoff will be, it is worth highlighting the following salient features of these new technologies.Motivational edgeFull day work in stops with shift relief underground can be achived.Thus continuous mining and its several advantages discussed below ceases to be a dream of the indust

40、ry but a reality applicable for both primary and secondary, surface and underground mining.Legal advantageNon-explosive mining offers tremendous advantagesin that countless legal implications would fall through and would no longer haunt the industry. By virtue of using safe-to-handle energetic mater

41、ials, i.e. propellant instead of explosives, the perception of mining being the peacetimes most killing industry would fade away.Technical argumentNon-explosive rock breaking technologies are being introduced at the time when the mining industry is very environmental conscientious. Energetic product

42、s are designed with health and safety concerns in mind. Components are user-friendly and life entertaining therefore no special dispositions should be required in their handling and transported as pre-assembled units ready for charging in the hole or can be assembled on site shortly before use.The s

43、ystem guarantees cost-effective mining, which may come in as an第 6 页oxygen line to deep and marginal mines threatened with closure. This would boost the industry and contribute to ensuring its global competitiveness.The technology is set to revolutionise rock breaking in mining. Short of replacing h

44、igh explosives this technology would compete favourably and capture a sensible portion of the commercial explosives market. Its edge over explosives mining is embedded in the gentleness of the propellant combustion reaction. The slow release of equally huge energy like that from explosives enable mo

45、re useful work to be done in the rock, i.e. the longer the gas containment in drilled holes the better the breaking and the lesser the fine generation (crushing).Economic benefitsNon-explosive rock breaking is expected to offer the following advantage:Safety aspects:Little or no harmful nitrous fume

46、s are created,Little or nodust created when the blast takes place,Little or nofatal injury f rom accidental detonation,Due to lower concussion, fewer fractures in the solid rock surrounding the blasted area, which implies less rockfalls. (Great reduction in hanging wall fracturing).Temporary support

47、s are not blasted out leading to lower support costs.Number constraints and current regulations applicable to dangerous commercial explosives areavoided.Working time restraints in stopes are greatly reduced.Few misfires. Ever if they occur one can safely drill through them as the propellant would be

48、 rendered harmless on contact with the water.Productivity aspects:Production process to be continuous, i.e. no need for lengthy re-entry periods that underpins current inefficient work schedule of one blast per day.High monthly cal ls. A double advance per day in a panel is achievable. A第 7 页slight

49、increase in overheads (labor force and drilled meters ) that would be compensated by the extra advance production.Possibility of multiple breakings(3 to 4 times in 24 hours, provided that cleaning technology follows suite).Optimum utilization of the labor force. Crews relieve one another on theface.

50、Concentration of mining (reduced ore traming distances to impact on transport cost)In the mining industry, the strongest production criteria is to get as manyeffective blasts per face per month as possibleThis system offers a potential for 200 more blasts per month.Operational benefisThe product len

51、ds itself to increased panel length, in excess of 40 metres, subject to adapting the rock cleaning and disposal methods. It is noted that the current conventional operations (explosives) are limited to / 20m.Vastly improved mining cycles.Stoping width control improved thus less contamination of ore,

52、 optimisation of transported material underground, cost saving at milling.Flexibility as mining cycles, shift cycles and stope layout can be varied on site to the discretion of the miner.Reduction in waste development fewer orepasses, shorter crosscuts. (Subject to mine layout)3 CONTINUOUS MINING AS

53、PEXTSA mining industry is still not satisfied with the current achievement of propellant rock breaking technologies. Despite the claims, non-explosive mining has still to demonstrate high standards of health, safety and productivity. Field results recorded in primary rock breaking trials conducted a

54、t several mines are disappointing. Inspite of successful results being registered in block busting for secondary breaking and quarrying in surface mining, propellant with regard to第 8 页consistency in breaking rock burdens in stoping. It inflates the total drilling cost in stopes as more blastholes a

55、re required for the same tonnage (in comparison with conventional explosive breaking). Owing to the gas breaking mechanism that rarely generates new fractures, the method relies on microcraks that are created during drilling and on natural micro in-born discontinuities in the rock to initiate the fr

56、acturing process. In hard and well cemented rock formations where such path of least resistence are inexistent, the rifle effect often occurs. Upon initiation, the propellant charge propulses the stemming column through the collar in a blow out that achieves meaningless burden breaking. Such poor br

57、eaking results are exacerbated, on one hand by the unisotropy in rock formations and on the other hand by the perception in favour of massive breaking. Massive (multi burdens) breaking undermines the control of individual burden toe cleaning. Efficient use of propellant mining can only be achieved i

58、f precautions are taken to ensure not choking the blast by strictly avoiding to overburden individual blastholes. Controlled single burden breaking associated with a suitable face cleaning technology is the magic solution, the unique way to achieving real continuous mining in narrow reef stoping. In

59、deed, the major challenge facing the proponents of non-explosive technology is to provide the industry with a mining system, i.e. rock breaking and cleaning that optimistics the work schedule at the face.The initial idea that underpinned non-explosive rock breaking in SA evolved around breaking sing

60、le burdens and cleaning such resulting small amount of rock to enable continuous short-time breaking cycles. Though firing small charge of propellant emissions(CO,NO and NO2)in the working environment can be kept at lower concentration enabling thus the implementation of a schedule of shorter breaks