We love watching stuff blow up – what a rush! Blasting in construction is an efficient way of getting a job site prepped. Using controlled explosives in the excavation has been a popular method for breaking rock for over a hundred years. The size of the rock you’re demolishing will dictate the velocity of the explosives. The harder the rock type, the higher the velocity. The softer the rock type, the lower the velocity. Blasting is considered the fastest and cheapest way of removing rock on job sites and is very popular. Factoring in how long it will take to break the rock using this method (or any other) is essential when planning your Civil Information Management (CIM) process.

When to Blast vs. Hammer

If you’re working on roads, tunnels, large site projects, or dams, you will likely use the blasting method over slower methods like ripping or using a jackhammer. The reason is that these are typically more extensive projects with large quantities of rock to remove; this makes slower but cheaper methods of rock removal cost prohibitive and could delay your deadline. It makes sense to use the hammer for smaller-sized projects where the rock is easily accessible and not in large quantities. There are also considerations, such as location, that could prohibit you from using the blasting method, such as densely settled areas. Assessing your requirements and finding out what permits, if any, are mandated is a necessary step before getting started on the rock demolition.

Safety Considerations

The first step in ensuring your blasting is safe is determining your blasting limits which are not always easy. Accurately choosing the blasting limits is one of the biggest challenges associated with blasting. If you’re unsure or unclear on how to set the blasting limits, you need to reach out for guidance because blasting rock impacts nearby surroundings. Organizations (e.g., the US Bureau of Mines and Office of Surface Mining) have provided acceptable vibration standards based on research. Generally, the allowable vibrations are equivalent to a bus or loaded truck going fifty to one hundred feet away. These standards are necessary because they significantly reduce the risk associated with nearby impacts and potential damage.

Process of Blasting and Commonly Used Equipment

Rock blasting can be precise; many blasts are engineered with exact borehole locations and depths. Drones or photogrammetry are often used to create a detailed point cloud of the rock face, allowing for accurate blast calculations. Again, if you’re unfamiliar with how to do this, you must contact a subject matter expert to help you. The first step is drilling the boreholes in the rock using blast hole rigs. Blast hole rigs use rotating carbide drill bits to drill holes ranging from a few inches to over a foot in diameter and up to 200 feet deep. The holes are filled with explosives, and the detonators are connected to the main blasting wire. Next, the boreholes are blasted in a pattern determined by the engineer to brake the material up as efficiently as possible. Often, blasting mats may be required to contain the blasted rock and keep the amount of flying rock to a minimum. The area is usually constructed with old tires connected with steel cables.

What to do with Waste Rock

It may seem counterintuitive, but it gains some value after paying to blast rock. Waste rock is often used on-site and can be processed into valuable materials. Most shot rock is used in fill areas or dumped into designated on-site waste areas. It can also be used as rip rap and for boulder retaining walls. Some companies also set up crushing equipment on site and turn the shot rock into gravel for road bases or aggerate for concrete use. Shot rock is seldom hauled off-site, as it is bulky, heavy, and hard on over-the-road trucks and trailers.

When ECI Technologies is a part of your earthwork team, you’ll gain workflow efficiencies. We know how to quickly and accurately get you the CAD files and 3D models you need, and we understand the construction job sites. We offer solutions and guidance to our clients that they incorporate into their workflows to get a better project outcome. We take our dirt world experiences and your challenges and guide you through solutions that work. Give us a call today – we always answer our phones!