Drill and blast mining is the most commonly used mining excavation method in the world. Drill and Blast mining is extremely popular for numerous reasons, such as its cost, simplicity, and effectiveness. In this article, we&#;d like to take you through what drill and blast mining is, what are some advantages and disadvantages of utilizing this method, and finally walking you through a typical excavation cycle.
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The drill and blast mining, as its name would suggest, is a method of mining that begins with drilling holes into rock after careful surveying and developing a plan.
Next, these holes are carefully loaded with explosives. The explosives are then detonated, causing the rock to fracture and crumble.
From there, it is simply a matter of removing the blasted rock, called mucking. When all the blasted rock is removed, you can restart the surveying process all over again.
Since the drill and blast method is the most widely used method of rock extraction today, it obviously has many different advantages compared to two other common mining methods: cut-and-cover and tunnel boring.
Cut-and-cover mining is a process that begins with digging a trench and a subsequent tunnel (&#;cutting&#;), extracting the rock, before then returning the surface to its original state (&#;covering&#;). Tunnel boring refers to excavation done with a tunnel boring machine (TBM), which is basically a gigantic circular drill that cuts a tunnel through the rock.
The first step in any mining excavation operation is to plan and survey the land. This allows for the development of a plan that can minimize environmental hazards. This step is of crucial importance for drill and blast mining, since here is where all the calculations around the explosions will be done.
Next, blast holes will be drilled into the rock by a drilling rig into the foremost front wall of the tunnel, often called the working face. These holes will be drilled according to the blasting plan developed in step 1.
Now that holes have been drilled, the next step is to carefully load them with explosives. Detonators are attached to each explosive, and the explosive devices are also attached to each other. The quantity of explosives needed varies, but harder rocks require more explosives.
The holes are blasted sequentially, beginning in the center and then cascading outward. Although there can be hundreds of individual explosions, the entire blast sequence should take no more than a few seconds. It&#;s important to ensure that the explosives don&#;t detonate at the same time, but go one after another in specified intervals.
Before any rock excavation can take place, the blast tunnel must be properly ventilated. This is because the explosion dispersed large clouds of dust that then mixed with the gases created in the explosion. For obvious health and safety reasons, this air must be ventilated through pipes before anybody can enter the tunnel.
Now, it&#;s time to remove the rock through a process called mucking. Excavators will dislodge any splintered rock that wasn&#;t completely released by the explosion. Additionally, all the loose rock and rubble will be loaded into dump trucks, either with wheel loaders or conveyor belts.
Before the process can start all over again, the tunnel must be secured. Depending on the type of rock, there are a bunch of different methods that can be used to secure and stabilize the tunnel and its roof. 3 common methods are wire mesh, arches, and bolts. Wire mesh is great for preventing loose rock from the ceiling from falling on workers below. Bolting is the most common method, where large steel rods are drilled into the tunnel ceiling, which is then secured with a steel plate and a large nut to add stability. In poor conditions, steel arches may be necessary to hold up the walls and roof.
Now that the tunnel has been secured and is stable, you can then begin the next explosion of the process. Additional calculations and measurements must be made in order to ensure a safe and effective blast. The cycle from planning to securing in drill and blast mining can be repeated multiple times, depending on how big of an extraction operation is needed.
If you and your company are looking for any mining services company, you should look no further than American Mine Services in Boulder, Colorado. AMS has over 50 years of experience in evaluating, designing, and constructing mines and tunnels for a variety of construction needs nationwide. Some projects that we&#;ve recently been awarded are the Crystal Creek dam improvement project and the Fort Dodge Wall structure solicitation. Please contact us with any inquiries.
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Now more than ever, people are prioritizing the wellbeing of our planet &#; especially those who rely on it for their livelihoods. Because of the environmental effects of mining, some operations are looking at methods other than drill and blast mining to harvest minerals. Continuous surface mining is an alternative that helps your crew work efficiently.
One advantage of this method is in the name &#; it&#;s continuous.
&#;Continuous is the operative word here,&#; said Mike Selover, corporate accounts manager for Specialty Excavation. &#;We&#;ve got machines in Bauxite mines running 8,000 hours a year. That means those machines are running 22 hours a day. Day and night, rain or shine. That&#;s continuous.&#;
A pure product means larger profits, so minimizing product dilution is a priority.
&#;Using a continuous surface mining method, you can actually mine layer by layer,&#; said Gregg Van Roekel, applications specialist. &#;This way you can precisely get down to those elements that you need so you&#;re not having as much product dilution.&#;
Mining layer by layer also helps control product size. Instead of the uncertainty of size that comes with drill and blast, continuous surface mining machines, like the Vermeer Terrain Leveler® surface excavation machines (SEM), use mechanical excavation to be precise. According to Selover, Vermeer equipment typically sees about nine-inch minus with very few fines.
&#;Product dilution is solved with continuous surfacing mining and product sizing is consistent,&#; said Selover.
Removing explosives from the jobsite helps prevent flyrock and minimizes dust that can be kicked up after the blast. Seismic vibrations are also a consideration with drill and blast. Continuous surface mining combats this by creating pit walls upon their cuts.
&#;It&#;s an advantage to be able to cut that high wall so you don&#;t have jagged edges coming out,&#; said Van Roekel.
Vermeer machines can cut anywhere from an 80- to 90-degree highwall, depending on which attachment you utilize.
&#;This is all about maximum material extraction for a quarry site,&#; said Selover. &#; And when you use continuous surface mining you don&#;t have to store, handle or conduct a blast with high energy explosives,&#; said Selover.
Continuous surface mining also equips you to be precise in what you mine and load out.
&#;Selective mining and selective loading are two things you can do with continuous surface mining that you can&#;t do with drilling and blasting,&#; said Selover.
Using software and drawing up a mine plan in three dimensions can help you have a calculated plan of attack for proceeding with your work. By putting in the pit sumps, ramps, roads and water features, you can plan where to go while you mine to maximize your efficiency.
&#;If you understand your geology through core sampling and know where the vein of the highest quality ore is, you can draw a mine plan and go right after that, whether it&#;s in the ground horizontally or vertically,&#; said Selover. &#;That&#;s selective mining, which is also known as follow the seam.&#;
The process of selective loading can be done visually or with GPS information and includes loading out the minerals that aren&#;t product diluted. Lower grade quality material is sorted separately and left behind, allowing only the pure product to be loaded out. By only taking the minerals you&#;re interested in you are maximizing the product quality and product margin by avoiding product dilution found in the drill and blast mining method, all while making efficient use of the land.
To learn more about maximizing your efficiency in the mining process, contact your local Vermeer dealer.
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