There are a few critical parts of a blast that can make or break the performance of the blast design. One of the most important areas of the blast is the face. Face profiling is the process of measuring the free face of a blast. A lot of rock faces appear vertical but when you actually measure them they slope out. This slope is what we are measuring to make sure we put our face holes in the right spot.
Not all blasts are bench shots with an exposed face, but the majority of commercial quarry blasts are designed this way. All quarry bench blasts are designed around the face. If you drill holes too close to the face you cause flyrock. If you drill holes too far away from the face you will end up with a poorly performing blast that doesn’t move, causing issues that could include high spots in the floor upon digout of the blast, flyrock from venting blast holes that have nowhere to go but up, and excessive back and side break, to name a few. Even in applications where there is nothing to hit, excessive fly rock is still a negative. We can go into this in-depth in another post but it takes energy to throw rock, and that energy costs money. If it is not necessary to throw the rock, energy is being applied that was not needed, meaning money was spent and wasted.
Throughout our 30 years of drilling and blasting we have gathered large amounts of data on proper distance from the face for specific hole sizes in rock sources. This is known as “Face Burden”. Not only does rock differ from one quarry to the next but in the Northwest many quarries have a number of layers of various types of rock. With this knowledge, paired with the technology available to us today, we are able to remove all of the unknowns. We design blasts so we know exactly what they will do before we even start drilling holes. We drill the holes to place explosives in the exact spot necessary to maximize performance, which is extremely valuable for our clients.
In the good old days, blast design and drill pattern layout was done with a pole and a measuring tape. The driller would lay his tape out and stretch it along the ground in order to quantify an area, mark holes, and ultimately decide the fate of the blast (for better or worse). This process was slow, inaccurate, and could be unsafe at times. Today, we are able to use lasers to do the job for us. Not only are they accurate, but they are very efficient and remove the need for someone to get near a ledge or underneath a highwall to get a measurement. Now the work that would have taken two people hours to complete can be done by one person in minutes. Extrapolate this over the hundred of jobsites we visit each year and the difference in systems is significant. By using lasers to measure the difference in face burden from the top of the bench to the bottom, we are able to apply our experience and drill vertically or angle holes exactly as needed to achieve a specific result.
3-D Face Profiling Software
We are currently in the process of testing and assisting in the development of a 3-D face profiling software that will be the next big advancement for blast design. We are able to either laser measure, photograph with a camera, or fly an area with a drone to create a 3-D model of a bench and/or face in order to upload this model into software where we can generate an ideal blast design. This will be the next major step for blast design in our industry and will revolutionize, again, the way we go about our day to day jobs.