Drills have different mining functions, from providing geologists with different samples of soil for analysis to facilitating the extraction of precious minerals that would otherwise be difficult to reach.
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How many methods of drilling are there? As the mining industry advances and more excavating opportunities present themselves, the number of drilling methods increases. Whether it is for exploration, production, land-clearing or geotechnical purposes, there are drilling methods that serve every mining purpose. Auger Drilling Auger drilling is the simplest form of drilling. It involves the manual rotation of a helical screw into the ground, usually by two people although auger drills can also be mounted to small vehicles. Once the auger drill is deep enough, the earth is lifted up by the blade of the screw. This kind of drill specializes as an initial geochemical reconnaissance technique, which means it is used in softer soil to find the optimal place to mount a larger drill. Rotary Air Blasting Rotary air blasting is the most common shallow drilling method, in which a piston-driven hammer-like object drives the drill bit into the rock, fragmenting the hard surface into chips that are then lifted to the surface via compressed air. This method is ideal for drilling multiple holes in a short period of time, and less ideal for producing geological samples because the airblasting process can compromise the quality of the rock. Aircore Aircore drilling involves a three-bladed drill bit with a hollow drill rod in order to penetrate loose soil and rock fragments. After the drilling is complete, compressed air is blasted through the drill rod in order to bring the cuttings to the surface. While this method is typically slower than rotary air blasting, it is more precise, meaning that the samples collected are less prone to contamination. Reverse Circulation Drilling Reverse circulation is a popular method for mining exploration that shares similarities with both rotary air blasting and aircore drilling. The same piston-driven hammer is used to drive the drill bit into the rock, however, the larger rigs and machinery associated with reverse circulation drilling allow for the drill bit to be driven even further into the earth. Compressed air is then used to drive the fragmented earth to the surface. This method is ideal for geological exploration, as it produces contaminant-free samples and requires less handling, resulting in cost reduction and faster turnaround times. Diamond Core Drilling Diamond core drilling is the most expensive drilling method, as it involves using a drill bit that has been fortified with industrial diamonds attached to hollow drill rods to extract a continuous cylinder of rock from several kilometers below the earth. However, this method also produces the most accurate rock samples as the entire core of a mineral can be brought to the surface as opposed to mere fragments, making it ideal for procuring records on their strength, composition, porosity, etc. Blast Hole Drilling Blast hole drilling is a method of drilling used to clear out large amounts of the earth and make the minerals below easier to access. It involves the drilling of holes into the earth. Explosive charges are then placed into each hole and detonated. After the explosion, the broken material is cleared and, if the drilling and blasting occurred underground, the tunnels created by the explosion are fortified to allow for safe human entry. Alternatively to explosives, gas pressure blasting pyrotechnics can also be used to displace the rock for excavation. What types of drills are there? As mining operations have become more sophisticated with the passage of time, new kinds of drill rigs have emerged to meet the demand of mining companies. Nowadays, various mining drills utilise different features to complete different kinds of mining tasks while being both manually operated and remotely automated. These rigs are available in various shapes and sizes, functioning in confined spaces as well as large quarries. As a result, there is a wide array of surface mining drill rigs available for many different kinds of operations. Surface Top Hammer Drill Rigs Top hammer drill rigs are equipped with powerful hydraulic drills as well as a hammer. The hammer strikes the drill rod, creating a percussive force that travels to the drill bit and displaces the rocks, leaving them susceptible to pressurized air or water. This kind of rig is renowned for its reliability in the toughest conditions, as well as its fuel economy and low operating costs. When partnered with the drill and blast method, this drill rig makes the excavation process efficient. Surface Down-The-Hole Drill Rigs The purpose of a down-the-hole drill rig is to drill large-diameter holes downwards, consisting of a jackhammer screwed to the bottom of a drill string. Like other drill rigs, the DTH breaks up the rock so it can be flushed out using air or water. This particular rig specializes in high-capacity rock drilling in quarries, opencast mines, and rock excavation projects. Dimensional Stone Drill Rigs The dimensional stone drill rig has a more esoteric function that its other drill rig counterparts, in that its purpose is to drill precise holes in the ground in order to excavate for natural rock such as granite, limestone, marble, or sandstone so that it can be extracted and fashioned into blocks for construction. This rig is designed to drill precise holes safely and efficiently. Rotary Blasthole Drill Rigs Rotary blasthole drill rigs drill into the earth in order to create holes that can then be filled with explosives that clear large sections of rock for subsequent mining operations. Rotary blasthole drill rigs are renowned for their precision and depth, boosting productivity by making the process of blast hole drilling easier and more cost-effective. In addition to the range of surface mining drill rigs, there is also a wide variety of underground drill rigs available that meet the stricter safety and logistical requirements that underground mining entails. Development Drill Rigs Development drill rigs are mining vehicles that drill holes into the surface of a coalbed that explosives can be inserted into and detonated. These vehicles are modular, meaning they can be disassembled, transported, and reassembled with ease. They can also be used for small-scale mine development and large-scale tunneling. Tunneling Jumbos Tunneling jumbos are versatile modular electro-hydraulic excavation machines that can be used for both fast face drilling and mechanized longhole drilling and bolting. Jumbos operate as stationary work stations that an operator safely conducts mining operations from, consisting of one, two or three drock drill carriages, ensuring high productivity and reliability. They are used specifically for underground drilling and blasting jobs, however, they can also be used in tunneling if the hardness of the surrounding rocks prevents the use of tunneling machines. Top Hammer Longhole Drill Rigs Top hammer longhole drill rigs are ideal for mining operations where the highest priority is ore recovery and minimizing the contamination of rock fragments. Like its surface mining counterpart, this drill contains a piston-powered hammer that impacts the drill in order to shatter the rock before using compressed air to disperse the debris. Rock Support Drill Rigs Rock support drill rigs are engineered to install rock bolts that stabilize the rock face by transferring the load from an unstable mine exterior to the confined (and therefore stronger) interior of the rock mass. These rigs ensure the safety of underground drilling and blasting by securing the rock mass and stopping it from caving in. In-The-Hole Longhole Drill Rigs In-The-Hole longhole drill rigs are mounted on tracked or articulated carriers in order to be transported into a mine where it uses extension rods to drill holes and extract ore with the aid of an ITH hammer similar to that of the top hammer drill rig. Additionally, the ITH longhole drill rig also flushes out debris with pressurized water. These rigs are designed with mobility and accuracy in mind. Low Profile Drill Rigs Low profile drill rigs are mining drills that are built at a low elevation so they can enter more confined spaces that regular drills cannot due to their size. They are ideal for development, rock support, and production drilling in tabular ore bodies such as platinum and chrome mines. These drills come in single and double boom variants, meaning that their specialization for spaces with low heights does not sacrifice their ability to reach higher spaces if the need be. Narrow Vein Drill Rigs KSQ Technology are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together. Narrow vein drill rigs are similar to low profile drill rigs, in that they are designed to venture into and extract ore from confined spaces. However narrow vein drill rigs are designed less to accommodate height challenges and more for the general navigation of geologically complex mine spaces with widths less than 3-6m. Narrow vein deposits contain large amounts of gold, tin, copper, lead, and zinc that narrow vein drill rigs allow us to access and utilize. Secondary Breaking Drill Rigs Secondary breaking drill rigs are compact support drills that increase drawpoint availability in narrow vein mines and back caving operations by breaking oversized boulders that are causing blockages. These drills eliminate the need for explosives, which in turn eliminates the need for time-consuming ventilation and evacuation measures while promoting a safer mining environment. These small drill rigs are available in the form of jumbos, longhole rigs, and drill-charge and drill-split breaking units.
Drills are used to create a hole of a certain diameter and depth. Occasionally, the goal of drilling is to create an empty hole, but more often, the purpose of the hole is to accept explosives. The major components of a drill include the bit, which fragments the rock; a power source that transfers energy to the bit; and lengths of drill steel, sometimes called the drill string, that connect the bit to the drill rig proper. Drills vary by: the method of rock penetration, e.g., rotary or percussion; the location of the power source, which can be at the top of the drill string, e.g., top hammer, or at the bit, e.g., down-the-hole; primary method of powering the drill, e.g., diesel engine, electric motor, or compressed-air; and the method of mounting the drill rig, e.g., track-mounted or tire mounted.
Here, we have a track-mounted down-the-hole drill with an articulating boom to facilitate drilling holes at precise angles.
Figure 5.1.1: Track-mounted down-the-hole drill
Source: Atlas Copco
While the previous drill employs a down-the-hole hammer to apply energy to the bit, this one is a top-hammer drill, i.e., the energy source for the bit, at the top of the drill string. That means the “pounding and rotational” action has to be transmitted through the drill string to the bit. The biggest disadvantage of this approach is the loss in accuracy. The drill string tends to travel in a large helical track with the top hammer, and this causes the drill bit to “wander” off the desired location of the hole.
Figure 5.1.2: Top-hammer drill
Source: Atlas Copco
If these drills are going to be used underground where the headroom is limited, the mast is not as high but otherwise the drill is similar. While the accuracy of hole location is most always important, in some underground applications, it is crucial. In those, a down-the-hole hammer will be used.
Vertical or inclined holes are commonly required in surface mining, and sometimes in underground mining. It is very likely that horizontal or nearly horizontal holes will be required in underground mining, as well as overhead vertical or overhead angled holes.
The dual boom jumbo drill is designed to drill horizontal or inclined holes at angle off of the horizontal. The depth of these holes is typically limited by the application and is on the order of 15’.
Figure 5.1.3: Dual boom jumbo drill
Source: Atlas Copco
Ring or fan drilling and longhole drilling are characteristic of a few underground metal mining methods. The holes may be 150’ or long, and must be drilled to precise depths at the exact design angles. Drills to accommodate these requirements employ computer control to achieve the required accuracy, as do more and more jumbo and other drills being used in production operation. A typical drill is shown here. Note the remote operating station for the drill operator.
Figure 5.1.4: Computer controlled drill with remote operator
Source: Atlas Copco
This diagram illustrates the drilling pattern required in a sublevel stoping mine. Notice the layout of the holes. What do you think would happen if a hole was started, but the angle was off by a few degrees? Or what if a particular hole were drilled to 128’ instead of the designed length of 135’? Intuitively, I am sure you can imagine that it will affect the performance of the blasting, and you are correct. We’ll talk more about this when we cover blasting, but for now, please recognize that productivity, cost, and safety are adversely affected by less-than-optimal drilling practices.
Figure 5.1.5: Diagram of drilling pattern required in a sublevel stoping mine
Source: Atlas Copco
Finally, we should close our overview of drills with the handheld “jackleg” drill. In years past, these were used instead of jumbo drills in hardrock mining and for ground control applications in coal and metal/nonmetal mines. The size hole depended on the cylinder bore of the drill, as they were powered by compressed air, as well as the size of the drill bit. Hole sizes ranged from approximately 1” to 4”. Depending on the size, and consequently what the drill was used for, they were given names such as drifters or stopers. They are only used in modern mines for very specialized functions, requiring a few holes on occasion, here or there. Unfortunately, you will find them in widespread use in the underground mines of lesser-developed countries. I say unfortunately because they are brutal to use. Although much of the weight, around 75 lbs., is supported on the jackleg, the miner has to apply the thrust, i.e., pushing the drill bit into the hole. That alone is hard work. They are very loud, there is bone-jarring vibration, and they can produce dust-laden air and that along with the oil mist from the compressed air creates a respiratory hazard. Teams of miners would stand all shift-long operating these drills. Often they were paid based on the production that they achieved, and 15 years ago in the western U.S., one of these miners could easily earn $60-80 thousand dollars per year… but they earned every penny of that!
Figure 5.1.6a and b: The jackleg drill
5.1.6a: J. Kohler, © Penn State University, is licensed under CC BY-NC-SA 4.0 , and 5.1.6b: Atlast Copco
The practice of loading sticks of dynamite has all but disappeared from modern mining. Safer and more economic practices utilize explosives that are pumped, gravity-fed, or pneumatically blown into the hole. That’s not to say that we never use packaged material, because we do, and we’ll look at that when we discuss explosives and blasting practice. The vast majority of blasting, however, is accomplished with powders, gels, or emulsions that are bulk loaded.
Figure 5.1.7: Explosive truck for surface mining
Credit: J. Kohler, © Penn State University, is licensed under CC BY-NC-SA 4.0
The truck below is used in surface mining. It carries the materials to mix the explosive at the hole, and the equipment to place the explosive into the hole. Such an arrangement can be found in some underground mines as well. In this example, the explosive is being pumped into the hole.
Figure 5.1.8: An example of gravity flow, in which the explosive is fed augered into the hole.
Credit: J. Kohler, © Penn State University, is licensed under CC BY-NC-SA 4.0
In a mine in which the height of the active mining face is on the order of 15’ to 60’ feet, you will see equipment like this. The boom allows the blaster, standing in the basket, to reach each hole, insert a hose into the hole, and then load the explosive. In this picture, you can see the yellow tank that contains the blasting agent. There is a second tank on the other side, which is obscured from view in this photo. These tanks are known colloquially as “powder monkeys.”
Figure 5.1.9: Explosive loading machine. Note the blaster standing in the basket.
Credit: J. Kohler, © Penn State University, is licensed under CC BY-NC-SA 4.0
Rippers are dozers that have been equipped with one or more large drag bits. These are pulled through the ore as the dozer moves forward. Typically, they break up the top 6” – 18”, depending on the mechanical properties of the ore. Rippers are not very common because they are suited to few deposits. Occasionally, I’ve seen them used in soft high calcium limestone and in coal, but there are other examples. In the picture here, this ripper (seen at the back of the image) has three large drag bits.
Figure 5.1.10: Ripper with drag bits
Source: Stock image by Worradirek, shutterstock.com
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