Barczak has a BSc in physics, a science masters from West Virginia University, and is currently completing a PhD in mining engineering at the same university.

ILN: How would you compare the technology and practice of mine roof support testing over the last decade?

TB: Ten years ago, mines for the most part used conventional wood cribs and timber posts. There were no engineered secondary roof support products to speak of. That all changed with the introduction of engineered timber support systems by Strata Products USA and the Can support developed by Burrell Mining Products.

Today, there are over 50 different standing supports available for secondary roof support with a wide range of support capabilities. There have been probably over 250,000 of these support systems installed in the past decade and roof falls and material handling injuries have been declining as the application of these alternative supports has grown.

ILN: What are the main advances in coal mine roof control systems that have occurred over the last decade?

TB: Cable bolts provided a solution to higher anchorage and stronger support that was missing in conventional roof bolts, and I think has made a major contribution to extending the advancements already provided by roof bolting.

Can support, which largely broke the barrier of using only timber as a support material for standing support. The Can, developed to replace wood cribbing in high-deformation, western mine environments, is now frequently used in many longwall tailgates and continues to be one if not the most stable support on the market.

Pumpable roof supports overcome some of the limitations of the Can particularly in terms of installation, and I think will eventually be perceived as another major advancement in roof support technology, particularly for longwall mines.

ILN: What do you consider as your most important contribution to coal mine roof control research, and why?

TB: I think we have had a major impact on the development of new and improved support systems. The Mine Roof Simulator, by providing full-scale testing of new support concepts, has provided confidence in knowing the performance capabilities and limitations of these support products as they are developed and commercialized.

I think we have changed the way support systems are implemented from a trial-and-error approach to more of an engineered approach.

The STOP (Support Technology Optimization Program) software based on the full-scale performance testing has contributed significantly to this effort by providing a design tool for the mining industry where these support products can be evaluated on an equivalent basis. This put everyone on the same page when analyzing the supports, and perhaps more importantly, made people think about the design criteria. How much support did they want and how soon (how much convergence) did they need it?

However, this is where I think the biggest contribution is yet to be made. Although we know a great deal about the performance capabilities of these numerous roof supports, we know much less about how they interact with the ground that we are trying to control and just how much control they have.

Currently, I am working on the development of a design methodology based on a ground reaction concept. I am convinced there is a component of ground movement which we cannot control with relatively miniscule man-made roof support systems. The trick is to figure out how much of this uncontrollable convergence there is and make sure the support can survive this to provide roof control through the full mining cycle, whatever that may be.

Beyond this, we want the support to react quickly to resist the ground movements that it can control.

As you can see, these are generally conflicting design requirements, and compromises in each must be made to provide a practical support design. Only when this support and strata interaction is fully understood, will we be able to take the next step in optimizing support design for site-specific loading conditions and prevent premature failures without excessive over-design or conservative application of the support.

ILN: What do you see as future developments in supplemental underground coal mine roof supports?

TB: I mentioned earlier that roof support advancements, such as roof bolting, are as much about cultural advancements as they are technological advancements. I think we are seeing a similar cultural struggle with roof control that we saw in the 1950s with roof bolts.

Today, the issue is surface control. The surveillance data clearly shows the majority of injuries from mine roof these days are caused by the falling of small pieces of the immediate roof skin.

Screening has shown to be a very effective control technology to prevent this type of injury, but just like with roof bolts, it costs money and slows down the mining process, two things mines try to avoid as they strive for increased productivity. However, once the risk of injury becomes culturally unacceptable, mines will find a way to use this technology and research will find other ways to substantially reduce this source of injury as well.

On the standing support side, the cultural issue here is to accept the significance of material handling injuries associated with support construction as part of the big picture.

This one is coming along nicely, however, as the trend during the past five years has been toward systems that are easy to install. Actually, the Can support contributed to this agenda ten years ago, although the material handling aspects were most likely a fortunate outcome of the support design and not a primary design requirement.

The Can support, a pre-filled, low-density concrete support, was by necessity installed with a machine. The support was initially designed to replace wood cribbing in western mines, and unknowingly provided a significant material handling advantage resulting in less work and fewer injuries to the mineworkers.

I also think pumpable roof supports will change the industry if a low cost system can be developed. The current systems utilize an expensive grout that makes this support system among the most expensive in the industry. If this cost can be reduced, many more mines than are presently utilizing this technology could realize the advantages of a pumpable support system.