47 JULY 2023 WorldWide Drilling Resource® Blasting Basics Adapted from Information by The World of Explosives Before any blasting is done, extensive planning and preparation by blasting professionals must take place. Most importantly, for every step of the blasting process, safety is the first priority. First, blasting professionals will examine the site and evaluate the field conditions. Conditions which have an impact on the blasting plan include: geologic conditions including rock type and irregularities such as faults, cracks, and voids; the existence of surface and groundwater; changing terrain and elevations; available excavation equipment; as well as the job’s proximity to surrounding structures like homes, businesses, and even underground utilities. Drilling the Blastholes - Once the blast design is determined, blasthole locations are marked. Then, it’s time to drill the holes. While drilling the holes, if the drill operator encounters any geological conditions of concern, he will discuss them with the blaster. Drilling accuracy is very important, so knowing about the geological structure of the area can help the blaster plan for proper hole loading. Loading the Blastholes with Explosives - After the hole accuracy and depth have been verified, the next step is to load the holes with explosives. First, detonators are placed in each hole. These detonators are the primary elements used to initiate the explosives in the hole. They also contain the timing sequences necessary to help maximize breakage while minimizing off-site effects. The holes are then loaded with the explosives to perform the breakage. The holes are not filled completely. Space is left at the top of the hole, which will be filled with an inert material called stemming. Stemming is usually clean crushed stone or another inert material. Stemming helps ensure the energy released by the detonation stays within the confines of the blasthole and helps focus the energy horizontally. Connecting the Detonators - After the blastholes are loaded with explosives, the detonators are connected together. There are three main types of detonators: electric, nonelectric, and electronic. Each of these has its own characteristics which make it suitable for use on various blasting projects. The blaster decides which system is most appropriate for each job. Securing the Blast Area and Detonating the Blast - In preparation for the blast, the blaster will define an area to be secured, the blast area, and take steps to ensure the blast area is clear. In many cases, a warning siren will be sounded a few minutes in advance of the detonation. After making a final check to ensure the area is clear, the blast is detonated. All Clear - With safety always in mind, the blaster will examine the site after the blast to ensure it performed as planned. Once this is confirmed, an all clear signal will be given and the process of excavation will begin. In addition to safety, proper planning and communication are key to a successful blast. EXB We Are Not Alone There are two other bodies orbiting near Earth, sometimes referred to as moons, though they are not strictly worthy of the title. Discovered in 1986, 3753 Cruithne is an asteroid which actually orbits the sun. Since it takes the same amount of time to orbit the sun as Earth, it looks as if Cruithne is following our planet. Its orbit, when seen from the perspective of Earth, appears bean-shaped. Asteroid 2002 AA29 also orbits the sun once a year, following a more bizarre horseshoe-shaped path which brings it close to Earth (within about 3.7 million miles) every 95 years. Because of its proximity, scientists have suggested collecting samples from AA29 and bringing them back to Earth.
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