PDF] DRILL AND BLASTFile Format: PDF/Adobe Acrobat - View as HTML were produced using compressed air. These drills were of American origin ..... the rock blasting mechanism of an. explosive where the expanding gas ... www.ats.org.au/index.php?option=com_docman&task=doc_download&gid=8

David Lees - History of Drill and Blast - 1 -

DRILL AND BLAST Underground excavation dates right back to the Cave Men where they excavated for there homes and developed underground flint mines. This has advanced through history with man’s need for protection and hiding, aswell as mining metal and precious stones. From picks made of horn and flint techniques moved onto metal picks. Then came ‘fire setting’, where fires heated up the rock which was then dowsed in cold water, the artificial expansion and contraction causing the rock to shatter. Then with invention of gunpowder, the necessity of boring holes arrived and the first inception of “drill&blast” was born. 1 HISTORY OF THE ROCK DRILL ‘Beating’ the bore or drilling by hand uses the same method of penetration as all rock drills. When a chisel bit hits a rock surface the induced stress causes a shatter zone around the bit, if the bit is then rotated through 360 degrees and hit after each few degrees of rotation a circle of crushed rock will result. When this is continued, a round hole is formed.

Figure 1 Rock failure mechanism for a percussive drill bit The Drill or ‘Jumper’ as it was called, consisted of a bit or chisel edge which was usually flat since it cut more freely than the curved edge and was therefore used on deep holes. The curved edge was much stronger at the corners and hence more suitable for hard rock. The

shaft or stock was octagonal in section, and since it was found that a shorter stock transmitted a better blow several lengths were used in drilling one hole, each new length having a slightly reduced bit size, (as in all rock drills). The striking face was flat and had a similar cross section to the stock.

Figure 2 Beating the bore in a Cornish tin mine

Figure 3 Examples of the drills and sledges ( after G.G. Andre 1887 )

David Lees - History of Drill and Blast - 2 -

The drill or ‘jumper’ was hit by a sledge or hammer. The sledges were carefully designed as well, those used for drilling blast holes had a flat face to deliver a direct blow with a chamferring of the head to ensure that the sledge would fly off when a false blow was struck, and hence miss a man’s hands holding the drill. A hammer was smaller than a sledge, about 3lbs with a 10 inch handle to be used with one hand. The sledge was between 5lbs. and l0lbs with a handle designed for two hands between 20 incites and 30 inches long. In 1870 Ingersoll and Rand rock drills were produced using compressed air. These drills were of American origin and were a great achievement since they were designed with very few moving parts. The design consisted of two tappet levers, therefore the vibration of the shock is much less and wear on the parts is less also. Then to ensure durability, the valve gear consists in making the spindles separate from the valves and tappet levers and in the case of the piston striking the cover an elastic cushion is provided. Mokean designed a rock drill for the St. Gothard Tunnel with a very ingenious mechanism for automatic feed, but this feature was not possible to include in the lighter machines for ordinary mining and quarrying. The Sach’s rock drill, designed by the German Carl Sachs had less durable moving parts but, with its screw feed as compared to the conventional winch handle or a wheel as used firstly on the Dubois/Francois drill, it was much favoured on the Continent.

Figure 4 Holman’s Rock Drill The Schram rock drill, a Swedish and German design, was the start in an era of simplification. It had just four moving parts; a working piston which drove the borer; a slide valve; a slide rod and a small piston which drove the working piston and all these were worked directly by the motor fluid. Mr. Schram was a mining engineer and like his compatriots realised an automatic feed was impractical and therefore did not include it in his design. The advantages of this design were quite obvious, the piston is perfectly free, the full fluid pressure is kept during the whole stroke, the friction loss is small and it has fewer moving parts all of which are readily accessible. The whole construction of the machine is simple and strong.

Figure 4 Holman’s Rock Drill

David Lees - History of Drill and Blast - 3 -

Then came John Darlington with an even simpler idea. He realised the main problems of most drill designs was in the very fragile gears, that the destructive piston blows meant that high velocities were impractical. He therefore based his design on just two parts, the cylinder and the piston. As well as this, he made the possibility of quick drill changes and held the tool firmly to reduce the strain on it, all this meant faster drilling. Machine drilling spread quickly due to the much higher progress rates that were possible . With hand drilling typical progress of eighteen inches a day was achieved (about 46cm), whilst in 1948 at the Marie Vale Consolidated Mine in South Africa, 1,227 feet (about 374m) was achieved in 26 days with six 31/2 inch Holman’s drifters, (that’s a rate of over 47 feet or 14.3m a day!). These increases in penetration also meant more dust which meant an increase in Silicosis or “Miners Complaint” which killed many miners every year at a young age. The first place to tackle this problem was South Africa, where water was thrown from a puddle by a small tin. Then, in 1902, it became official that water should be used to dowse the dust and at this time Leyner designed a drill on which today’s drills are still based. The steel was held loosely in a chuck attached to the cylinder itself and the piston reciprocated and struck the blunt end of the drill steel. The most important improvement was his method of introducing air down through the drill steel to keep the drill holes clear of rock. This raised a lot of dust, so he introduced water along the drill with the air; this innovation soon dominated the world market.

Figure 5 Leyner’s patent An historical method to solve the dust problem but which could not compete with Leyner’s design, was the dust allayer. Experiments were started in 1935 by Major A. Hibbert and Mr. Charles Wetherhill to try to prevent the dust by projecting a fog against the face. Water was found to be useless on its own since it held the particles until it evaporated, so they tried to reduce the surface tension of the water and found Castor Oil was the answer, but the miner’s did not like it so did not use it. The complaint was that it produced dampness which tends to rheumatism, and also since the water underground was not very clean, damage to health might be done by inhaling a spray of disease laden water. 1.1 ROCKDRILL DEVELOPMENT IN AUSTRALIA The first rockdrill to be used in Australia is believed to be a Low machine imported in 1867 by the Mount Tarrengower Tunnelling Company to be used in a goldmine in Maldon, Victoria. The drill was selected by the Mine Manager, Mr Gardner, after a visit to the Paris Exhibition. The drill, designed by English inventor George Low, was mounted on an iron frame and ran on wheels and rails with a small steam engine which was worked by

David Lees - History of Drill and Blast - 4 -

compressed air at 90 psi delivered from the surface. The drill arm could be directed in any direction through a twisting socket.

Figure 6 The Low Rockdrill This was in essence a single boom, rail mounted jumbo, with remote controlled pneumatic boom positioning and a powered hose reel. The drilling rate in granite was about 50mm/minute for a 50mm diameter hole. Unfortunately due to problems with spare parts, the drill had major maintenance problems and due to lack of ore the mine folded in 1870. The fate of the machine is not known. In 1868 a local rock drill known as Ford’s patent was manufactured and tested in Castlemaine, Victoria. Unfortunately this machine was complicated and difficult to repair. In 1879 a great exhibition of machinery was held in Sydney. At this exhibition percussive machines took second place to exploration diamond drills for the coal mining industry. Hence it was in Victoria where the percussive drills were developed for underground mining. In the late 1880s the RD Oswald machine was manufactured at the North British Mine at Maldon. After a visit by George Thureau to California in 1877, the American rock drills started to appear on the Australian scene and Ingersoll Rand were operating in Victoria, South Australia,

New South Wales and Queensland from about 1876. The Ingersoll Drill Company exhibited their “Eclipse” drill at the 1879-80 Expo in Sydney, which was being used at Pyrmont Quarry. At the 1888 exhibition in Melbourne a number of other drills are mentioned including Teague’s patent produced by Harvey and Co from Hayle, Cornwall, a rock borer manufactured by Robinson and Co,, and a diamond drill by McBullock Manufacturing Co. of Chicago, and the “Slugger” and “Little Giant” by the Rand Drill Company of New York. The Rand drill machines were advertised with an improved air compressor. The air compressor was direct acting from a 12 inch diameter steam engine. The compressor had sufficient air to supply four or five Little Giant drills at pressures of 65 to 70 psi. The Little Giants were described as “strong and light, easily handled by two men and well adapted to work underground in stopes”. The Slugger was a heavier drill and more adapted for development work underground and is reported to have achieved 102 feet advance in one week with three machines in 1887 in hard quartzite gneiss.

Figure 7 The Slugger

David Lees - History of Drill and Blast - 5 -

With influence from the mechanisation at Broken Hill, the Australian mining industry turned more to American machines in favour of British and particularly Cornish influences. In 1893 Gold was discovered at Kalgoorlie and the Ingersoll Sergeant Drill Company was established in Kalgoorlie in 1897. In 1905 a merger to form the Ingersoll Rand Company marked a new generation in the story of the development of the rock drill in Australia including down-the-hole hammers and tungsten carbide tips. 2 HISTORY OF EXPLOSIVES An explosive can be a substance or a device that produces a volume of rapidly expanding gas that exerts sudden pressure on its surroundings. There are three common types of explosives: chemical, mechanical, and nuclear. Mechanical explosions are physical reactions, for example the effects of compressed air.

Explosives have been around for a very long time. The very first explosives were accidentally made by ancient Asian alchemists in the 10th Century. They added the ingredients of saltpetre and sulphur, two common materials, and found that the mixture actually detonated. The Asians did not use their new creation for war. They made the first fireworks out of the substance, which they used for

communication. Much later on, the Asians developed a very crude projectile weapon using their explosive technology. The Arabs stole the Asian's knowledge and brought the knowledge westward. The era of explosives had begun.

In the 13th century Roger Bacon, a European, was interested in the new knowledge. He studied it and tested it over and over again. After many months he found the perfect ratio of saltpeter, sulfur, and a new ingredient, charcoal. After he found out the perfect ratio he wrote the ingredients and the amounts in code in his diary. Roger Bacon had made, and recorded, the first black powder (the early form of gunpowder).

Bacon did not get credit for the making of black powder because he didn't use his invention. Berthold Schwarts saw this and exploited it. He experimented with many devices and finally thought of a great idea. Schwarts used the black powder to launch a pebble at high speed out of a metal tube. Schwarts had invented guns.

The invention soon progressed to cannons which were capable of launching boulders through stone castle walls. Gunpowder also sped up the very slow process of digging up stones. With gunpowder they could blow the stones out of the ground. Before, only the rich people could have stone houses because it took so long. Now even some poor people could have a house of stone. This was a great technological advance.

Five hundred years after, in 1846 an Italian scientist named Ascano Sobrero, thought of a new idea. He mixed nitric acid and glycerin together to see what would happen. The new substance nearly exploded in his face! Sobrero had discovered nitroglycerine.

David Lees - History of Drill and Blast - 6 -

After testing he saw that the highly unstable mixture was very powerful. It was so unstable that it could be detonated by a touch of a feather.

Figure 9 Alfred Nobel

In 1852 Alfred Nobel took up the task of making nitroglycerine more stable so it could be used as a commercially and technically useful explosive. This proved to be very dangerous and resulted in the death of many people including his brother Emil. He soon found that mixing nitroglycerine with silica would turn the liquid into a paste which could be shaped into rods of a size and form suitable for insertion into drilling holes. In 1867 he patented this material under the name of dynamite. This was one of the first high explosives. People used the new explosive for excavating and tunneling. Nobel got the credit for not only nitroglycerin but dynamite, too. Nobel became very rich and famous. He knew the amount of destruction his invention would cause and he did not want to be associated with thousands of deaths, so he left a large amount of money to the awarding of prizes every year. The prizes were given to the best in Chemistry, Medicine, Physics, Literature, and the promotion of peace. The prizes are still given out every year.

Two important developments in the history of explosives were the

inventions of the safety fuse and the blasting cap. In 1831 William Bickford of England devised the safety fuse, originally a textile-wrapped cord with a black powder core, which for the first time enabled safe, accurately timed detonations.

In 1865 Nobel invented the blasting cap, providing the first safe and dependable means for detonating nitroglycerin and thereby considerably expanding its use for industrial purposes. Electrical firing, first used successfully in the late 19th century, allows greater control over timing.

The year 1955, marked the beginning of the most revolutionary change in the explosives industry since the invention of dynamite, with the development of ammonium nitrate–fuel oil mixtures (ANFO) and ammonium nitrate-base water gels, which together now account for at least 70 percent of the high explosives consumption.

3 URBAN DRILL AND BLAST Whilst drill and blast has been successfully utilized for major construction projects its application in urban development is restricted due to environmental constraints - in particular dust, noise, and vibration. In fact in many urban centres where rock excavation is carried out, blasting is not allowed. In Hong Kong for

David Lees - History of Drill and Blast - 7 -

example there are many strict rules for limiting blasting activities. In the city centre, adjacent to existing metro tunnels and other services and beneath water culverts, blasting is either specified as not permissible or requires an extensive application process for permission from the Hong Kong Mines Department. Rock breaking is therefore limited to mechanical means and for small excavtions expanding grouts and hydraulic hammers are used and progress is generally slow. In Sydney CBD deep basement excavations have been developed for many large buildings to create parking and shopping facilities underground but blasting is generally not permissible and the excavations in the Hawkesbury Sandstone are made by hydraulic hammers. Recent tunnel developments such as the Eastern Distributor, M5 East and Northside Storage Tunnel have been carried out by roadheader and TBM, but cross passages, ventilation shafts and other small excavations require alternative techniques. Controlled blasting usually imposses constraints on progress and production, and alternatives such as hydraulic hammers may often cause more environmental impact for residents, due to the continuous nature of the noise and vibration and the prolonged period of its operation. The RTA (2000) has stated for the new Cross City Tunnel that excavation will be by rock boring techniques and blasting will be restricted. 3.1 RESTRICTING CRITERIA Rockbreaking by blasting creates ground vibrations, air blast, noise and flyrock. Control of these impactss in an urban environment is critical to minimise damage to structures as well as annoyance to neighbours.

Ground vibrations Blasting essentially causes three different types of vibration; namely – P waves or compression waves and S waves or sheer waves that travel through the rock, and R waves or Rayleigh waves which travel along the surface. The intensity of these vibrations is generally controlled by the limiting criteria PPV, or Peak Particle Velocity. A large amount of research has been done in this area and a number of relationships have been developed between the explosive charge and the value of PPV at a certain distance from the blast. A common representation of this is: PPV = K ( R/W β)

α (1)

Where: PPV is the peak particle velocity (mm/s) R is the distance from the blast (m) W is the maximum instantaneous charge (kg) K, α and β are site constants.

The relationship is either a square law or cube law where β = 0.5 or 0.3. Work carried out in many different rock types by the US Bureau of Mines (Siskin et al 1980) has suggested a square law is appropriate in most cases with the following values for the site constants: K = 1244 and α = - 1.45 (2) In some parts of the world other local site constraints have been developed such as:

David Lees - History of Drill and Blast - 8 -

Hong Kong Mines and Quarries Division K = 644 and α = - 1.22 (3) Sydney Water K = 1143 and α = - 1.6 (4) The effect of vibrations on structures has also undergone a large amount of study and a number of restricting values have been presented. Proposals for limiting criteria are given by many authorities including the Australian and British Standards, The UK Transport Research Laboratory, The Hong Kong Mines Department and Mass Transit Rail Corporation (MTRC) specifications. A summary of these criteria presented is given in Table 1. Limiting initial charges within the requirements of the local blasting laws ensures maximum PPV limits are not achieved. Monitoring these initial blasts in a series of trials enables actual site constraints to be determined so that real site specific blasting criteria can be developed. Table 1. Vibration limits from blasting (after New 1986)

Air blast In every blast a portion of the total blast energy escapes into the atmosphere. The temporary overpressure (pressure above atmosphere) produced by the explosion is emitted as a wave which travels at the speed of sound. The arrival of this wave at any point may be sensed as noise, or shaking or rattling of loose objects. The airblast overpressure from an unconfined explosive charge can be estimated from: P = 185 (D/W 1/3)- 1.2 (4) (after Ssiskin et al 1980) Where: P is the air over

pressure (kPa) D is the distance from the blast (m) W is the maximum instantaneous charge (kg)

and sound pressure on the decibel scale is determined from: dB = 20 log10 (P/Po) (5)

Where: Po is the reference

pressure of 2x10– 8 kPa.

Structures Max. ppv Commercial and Industrial Buildings 25 mm/s Houses and low rise residential buildings 10 mm/s Historic Buildings 2 mm/s Utility Services 35 mm/s Slopes and retaining walls 35 mm/s Water retaining Structures 13 mm/s Computer installations 5 mm/s Human comfort 2-5 mm/s Fresh Concrete (less than 2 days old) 5 mm/s Concrete between 2 and 8 days old 25 mm/s Concrete more than 8 days old 50 mm/s

David Lees - History of Drill and Blast - 9 -

Table 2. Airblast limits from blasting (after Siskin et al 1980)

A summary of levels of damage sustained from air blast overpressures (after Nicholls et al 1971) are given in Table 2. Routine blasting operations in which explosives are confined in blastholes and which are designed to limit PPV to less than 50mm/s typically do not generate airblast overpressures that cause significant damage to residential structures. Noise Noise is a nuisance factor rather than a damaging influence and the US Bureau of Mines has specified safe standards as presented in Table 3 (after Siskin et al 1980). Problems can occur from blasting in built up or enclosed areas where the air blast may be magnified and reflected. This is overcome by correct stemming and use of sand bags blasting mats over the blast holes. Flyrock Flyrock can be a very dangerous side effect of blasting. The very nature of the rock blasting mechanism of an explosive where the expanding gas propagates fractures and moved the broken rock creates the opportunity for small fragments to travel at high speed and for considerable distances. Table 3. Noise limits from blasting (after Siskin et al 1980)

Work presented by Lundberg (1973) states that for a specific charge less than 0.2kg/m3 there is no throw but for other values the maximum throw is expressed as: L = 143 d (q- 0.2) (6) Where d is the hole diameter

(mm) q is the specific charge (kg/m3).

For values of q greater than 0.2 kg/m3 flyrock is generally overcome by providing blasting covers and barricades to control the flyrock. 3.2 NON EXPLOSIVE ROCKBREAKING An answer to the problems of rock breaking using conventional explosives has been provided by going back to the properties of Blackpowder. PCF or Penetrating Cone Fracture, is an example of this and consists of a faster burning propellant that generates high-pressure gas at the lower point of a drill hole. This gas, when held in a hole by stemming, is forced into micro fractures formed in the rock by the percussive drilling process and initiates and propagates natural and drilling fractures to break the rock.

Air blast overpressure Effect 20 kPa (180db) Structural damage 14 kPa (175db) Windows fail 5 kPa (168db) Some failure of poorly fitted window

panes 1 kPa (155db) Some prestressed window panes fail 0.2 kPa (140db) Windows and small objects shake <0.05 kPa (128db) Avoid disturbance to people

Safe level 128dB (0.048 kPa)

Allowable impulsive noise limit 136 dB (0.134 kPa)

David Lees - History of Drill and Blast - 10 -

The product is classified as a non explosive means of rock breaking. The system has been developed by RockBreaking Solutions, a subsidiary of Brandrill Limited. As it is not an explosive and does not produce the initial seismic pulse of an explosive, the vibrations due to rock breaking with PCF are less than conventional explosives. As the rock is broken through the propagation of fractures rather than pulverisation of the rock there is little or no flyrock and the airblast is minimal as the energy is used in fracturing the rock. 7 Table 5 Comparison of airblast from PCF to conventional explosives

The following equations were derived by independent tests of PCF explosives in granite rock.

PCF PPV = 1090(D/W0.5)-1.39 (7) Explosives PPV = 1483 (D/W0.5)-1.25 (8) Typical comparative values of PCF compared to conventional explosives for a 60g charge weight for PCF and equivalent 360g of explosives in granite rock are presented in tables 4, 5 6, and 7.

PCF Overpressure Levels (dBL) Charge Weight (g)

Distance (m) Unattenuated Attenuated

(No Canopy) (Canopy, barrier & shroud) 60 10 107 55 20 100 48 30 96 39

David Lees - History of Drill and Blast - 11 -

Table 4 Comparison of vibrations from PCF to conventional explosives

Table 6 Noise values from PCF operations

dBA (@ 50m) Range 50 - 68 Mean 59

PCF also has good fume characteristics enabling it to be used in closed confined conditions:

Table 7 Typical fume characteristics from PCF

EXAMPLES PCF has carried out a number of successful projects recently which include:

1. Underground plant rooms at North Point Station on part of the Kowloon Line for the MTRC in Hong Kong.

2. Mass excavation of the top

4 metres of dam wall and 13 spillway recesses at Canning Dam in WA and excavation of a 5m adit into the lower gallery.

3. Excavation of cross adits

for M5 East Tunnel in Sydney

4. Breaking of boulders

adjacent to highways at Tandy’s Lane in NSW and Gunalda Bypass in Queensland.

5. Tunnel development for the

LTA beneath Clarke Quay in Singapore.

6. It is currently being used

for excavation of a large

Distance (m) Vibration (mm/s) PCF Explosives 5 16 105 10 6 44 15 4 27 20 2 19 30 1 11 50 1 6 100 0.3 2

Gas Concentration (mol/kg)

Concentration (L/kg) @ STP

Concentration (%w/w)

Emission (L) (per 100g PCF charge)

Carbon Monoxide (CO)

18.23 408 51.2 40.8

Water vapour (H2O)

8.79 197 15.8 19.7

Hydrogen (H2)

5.13 115 1.1 11.5

Nitrogen (N2)

4.6 103 12.9 10.3

Carbon Dioxide (CO2)

4.22 95 18.6 9.5

David Lees - History of Drill and Blast - 12 -

basement to form an underground carpark at Bondi Junction.

4 CONCLUSION Drill and blast has developed a long way since its early inception but even with the development of hard rock mechanized excavation technologies such as TBM and roadheader, drill and blast is finding an increasing application in modern hard rock underground excavation.

5 REFERENECES

1. Andre G.G. (l887) A Treatise on Mining Machinery

2. Australian Standards (1983) SAA – Explosives Code. AS2187 part 2

3. British Standards Institution 1984. Guide to evaluation of human exposure to vibration in buildings (1Hz – 80 Hz). BS 6472

4. Brown G I. The Big Bang: A History of Explosives

5. Crozier Ronald D. Guns, Gunpowder & Saltpetre. Faversham Society

6. Hong Kong Mines Department. Assessment of stability of slopes subject to blasting vibration. GEO Report No 15

7. Lowe, P.T. and McQueen L.B. 1990. Construction of the North Head Ocean Outfall Tunnel. Seventh Australian Tunnelling Conference, Sydney, September 1990. Inst Engineers, Australia, Canberra, Australia

8. Lees DJ (2000) Constraints for tunnel construction in the urban environment and how to overcome them. AUCTA Workshop – Planning for Tunnelling in the Urban Environment. Preconference Symposium of Geoeng 2000

9. Lees DJ(2001) History of the Rock Drill. AUCTApril 2001

10. Lees DJ(2001) Rockdrill Develoment in Australia. AUCT Nov 2001

11. Lundberg, N. 1973 The

calculation of maximum throw during blasting. SveDeFo Report DS 1973:4

12. McCarthy PL (1985) Rockdrill Develoment in Australia. AusIMM Bulletin Vol 290 No 2 March 1985

13. New, B.M. 1986. Ground vibration caused by civil engineering works. Transport and Road Research Laboratory Research Report 53. TRRL Berkshire UK.

14. Nicholls, H.R., Johnson, C.F., and Duvall W 1971. Blasting vibrations and their effect on structures. USBM Bulletin 656

15. RTA 2000. Environmental Impact Statement for the Cross City Tunnel, Roads Traffic Authority of NSW. Sydney

16. Siskin, D.E., Stagg, M.S., Kopp, J.W., and Dowding, C.H. 1980a. Structure response and damage produced by ground vibrations from surface mine blasting. USBM Report RI 8507

17. Siskin, D.E., Stachura, V.J., Stagg, M.S., and Kopp, J.W. 1980b. Structure response and damage produced by airblast from surface mining. USBM Report RI 88485.

18. Treve Holman(1946) Historical Relationship of Mining, Silicosis, & Rock Removal.

19. Weston (1923) Rock Drills 20. Jim Whitehead The

Development of Ingersoll Rand in Australia

21. www.inventors.about.com/library 22. www.sis.ac.uk/~dj9006/explosive

s/homepage