Rock Drills in the 19th Century
Humans have been drilling holes in rocks for more than 4,000 years. Drill holes used for explosives need to penetrate some distance into the rock mass; otherwise all that happens when the explosive is detonated is that rock at the surface is shattered. A steam — driven rotary drill was built in Cornwall about 1815, and a steam-driven churn drill, based on the ancient Chinese method of lifting and dropping a rod tipped with a bit, was built by Isaac Singer in the United States about 1835 to work on the Illinois-Michigan canal. Neither drill became popular, and Singer turned his attention to a mechanical sewing machine for which he achieved more notoriety.
Manual drilling with hammers and bits proved to be the only reliable method of drilling until the invention of the mechanical percussion drill in the mid-19th century. Three men could drill a 2-m deep hole in granite in 5-6 hours on average depending on the conditions (Chugh 1985). In 1850, manual drilling with hammers and bits was still the only reliable method of making holes in rocks (see Chapter 3).
The first mechanical percussion drill was invented by J. J. Couch in Philadelphia in 1849 (Rodengen 1995). The principle was that steam was admitted alternately to each end of a cylinder; the drill was thrown like a lance at the rock on the forward stroke, caught and drawn back on the reverse stroke, and thrown again (McAdam and Westwa — ter 1958). It was the first drill that did not depend on gravity, but it was cumbersome and the machine weighed several thousand pounds. Another drill patented in 1851 by Couch’s former colleague J. W. Fowle (Rodengen 1995) was an improvement because the drilling rod was attached to the piston and impelled by the entire power of the engine. This drill, which was also powered by steam, was used successfully in practice, and a similar drill built the same year in France used either steam or compressed air. In these percussive drills the bit made contact with the rock every cycle of the engine and this was how drills worked for 40 years. By 1855, several events gave impetus to the development of mechanical drills.
Work had started on the 8.2-km Hoosac Tunnel in Massachusetts (Sumberg 1999) and in 1857 on the 14.5-km Mont Cenis Tunnel in the Italian Alps (Harper’s New Monthly Magazine 1871). Manual drilling was known to be very slow and expensive; initial manual drilling advanced 23 cm per day at each end. It was estimated that with manual drilling the Mont Cenis Tunnel would take 30 years to complete, so there was much interest in pneumatic drilling.
Compressed air had become recognized as a suitable method for transmitting power over long distances. It had been used with furnaces to melt metals since 2500 BC, and the first mechanical compressor was built in 1776, but it was the need to transmit power over long distances to drive rock drills that made compressed air an important industrial tool.
The number of mines in operation and civic works under construction was increasing and the need for drilling was growing rapidly.
The growing interest in drilling led to many innovations and inventions such as
■ Simon Ingersoll’s invention in 1871 of a steam-driven drill mounted on a tripod that kept the drill steady and enabled it to be operated at virtually any angle (Rodengen 1995).
■ Germain Sommeiller’s use of waterpower from rivers near the Mont Cenis Tunnel to drive air compressors to power the pneumatic drills. He proved the value of compressed air in rock drilling, and the mechanical drills he used greatly reduced the time to build the tunnel. This success came despite his experience that for every nine rock drills that were in operation on each heading, 54 machines were being repaired. Eventually he was able to transmit power by compressed air over 7 km and improve the rate of drilling with 280-kg drills from 0.46 m per day in 1861 to 2.27 m per day in 1870.
A major advance in drilling came in the late 1880s when C. H. Shaw, an engineer in Denver, Colorado, devised a hammer drill in which the piston was separated from the drill rod and hammered it each cycle, thereby increasing the frequency of blows and the rate of penetration. This was suitable for up holes when the cuttings fell out by gravity but not for down holes, and this problem was not solved until 1897 when J. G. Leyner patented a hollow drill rod through which air was pumped and flushed out the cuttings. Water soon replaced air, which reduced the dust that had until then been a lethal problem.
Success in building tunnels using pneumatic drilling and blasting by dynamite had a great impact on rock engineering and size reduction, although the work was still extremely hard. In 1878, percussion drills using steam or compressed air could drill holes 87-100 mm in diameter and up to 16 m long, but the weight of the drills, about
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FIGURE 10.1 A rock drill used in Maldon, Victoria, in 1890 (Drinker 1888)
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FIGURE 10.2 Light rock drills driven by compressed air in the 19th century (Foster 1894)
180 kg, meant that they were hard to transport and set up (Drinker 1888). Figure 10.1 shows an 1890s drill.
Lighter pneumatic drills were built that could be handled by one man, and they increased the rates at which minerals could be mined in confined spaces. The drills may have been lighter but were still difficult to handle, as shown in the sketch in Figure 10.2.
Drilling and blasting advanced quickly during the last quarter of the 19th century because extensive R&D programs were driven by the need to reduce the costs of the great tunnels and canals being built in Europe and the United States.
Some of the problems with building them were
■ Drills had to work in an environment that was as difficult for a machine as could be imagined, and it was necessary to build machines that were stronger, more durable, and more reliable. It has been said that no tougher service for steel is known than in a rock drill. During every minute of operation there are approximately 2,000 violent collisions between the piston and the shank end of the drill rod.
■ Explosives were still dangerous and unpredictable, and their safety had to be improved without reducing their breakage energy.
The R&D programs carried out from 1875 to 1900 were difficult and dangerous, but with all their problems they were very successful and resulted in explosive rock breakage becoming one of the great technical achievements of the 19th century.