Mining upward sounds like a counterintuitive and dangerous idea. In reality, excavating from the bottom up offers a lot of advantages compared to traditional methods of developing raises. Strange as it may sound, digging up is a safe, flexible, precise and efficient way to work – and that’s why DMC has become quite skilled at it.
Raises are vertical excavations between levels of a mine, invaluable for egress routes, ventilation, and hoisting material. In just about any complex mining operation, multiple raises are necessary. When mines are expanding, new raises are crucial.
At DMC, we have invested in two approaches to digging mechanical raises that are specialized and valuable: Raise Bore and Alimak raising. Between the two techniques, we can cover just about any raise excavation need, situation, or operational requirement and customize innovative solutions to meet our clients’ needs. That’s why we have so many repeat customers over the years – customers trust our expertise and quality of work.
Raise boring can be done between any two horizontal surfaces, whether it’s from the surface or between two levels of a mine. In this approach a rig is set up to precisely drill a pilot hole down to a reamer, the drill bit is detached, and the reamer attached. The rig then pulls the rotating reamer back up to excavate a wider diameter as it progresses.
Compared to conventional or long-hole raises, Raise Boring offers several significant advantages. Since it’s mostly mechanized, it requires just minimal labour once set up. As well, safety and efficiency is improved since it doesn’t require blasting, and is a continuous process with less downtime. And finally, the resulting process creates smooth wall surfaces that doesn’t require finishing or reinforcement.
Smooth walls are a key consideration when excavating ventilation shafts, as they reduce turbulence in air. Less turbulent air can be moved much more efficiently, which can create significant energy savings over the operational life of a mine—often referred to as the ‘save factor’. For this reason, most ventilation shafts we build are created using this technique.
Our fleet consists of 9 Raise Bore machines, with over 7,500 feet of drill pipe and 16 reamers with diameters from 28 inches to 20 feet. Due to 30 years of experience using this technique, we have the expertise to provide a solution to just about any raise excavation problem a mine may encounter.
Alimak raising is a similar method of excavating upwards, except it begins at the bottom and proceeds via a drill and blast method. Alimak raising is named after the raise climbing equipment used, which allows cages with workers and equipment to be sent up the raise as it is excavated. As it requires less heavy, power-hungry equipment, Alimak raising is preferred in remote mines where logistics costs for bore raising would become prohibitive.
One noteworthy recent Alimak project that is a more innovative approach is currently in development for our client in Sudbury. This project will see the use of a mix of Raise Bore and Alimak techniques; first, a small raise hole would be bored, then the Alimak technique would be used from the top down. This is a novel configuration that DMC has used in the past, which is important because excavating at full diameter bottom-up with Alimak is unsafe.
This approach develops a single chute for waste and muck disposal at the mine, meaning only one loading station is required at the main shaft. While the raise is being blasted, the initial raise hole will allow waste rock to be quickly disposed so that work can continue. The priority in all mining projects is to meet or exceed schedules, so this technique is attractive due to the speed of advance it allows.
While much of DMC’s project work is done in shaft sinking, we are very well-known for our expertise in Raise Bore and Alimak mechanical raise work. Excavating raises is an important part of developing and expanding mines, and offering these services creates value to our clients so they gain efficiencies. The availability of raise bore equipment, and the unique specialization of both techniques mean that many mining operations rely on specialists like DMC for these services.
DMC has over 30 years of experience excavating raises, with successful Alimak and Raise Bore projects completed around the world – from North America to Africa and Europe – for a variety of project sizes and complexities, both in mining and civil engineering applications, for over a dozen repeat clients. Keeping our fleet and crews active keeps them in top form to develop and deliver excellence, and completes DMC’s ability to offer a full spectrum of mining services solutions to our clients.