The 35th annual International Conference on Ground Control in Mining (ICGCM) wrapped in late July at the Lakeview Resort in Morgantown, West Virginia, with an impressive turnout and one of the broadest breadth of topics the event has ever tackled.
According to conference co-chairs Steve Tadolini, Tom Barczak and Gerry Finfinger, a total of 202 attendees from across the U.S. and seven other countries were on hand to hear dozens of ground control presentations July 26-28. While academia made up the largest percentage, there was a healthy audience of mine operation representatives.
Looking from an international standpoint, China had the largest representation at this year’s event, followed by Australia. Other countries with delegates included Brazil, Germany, India, Mexico and the United Kingdom.
“We had the entire array of ground control topics this year — that wide breadth of options make the conference appeal to a wider audience,” Tadolini said. Of particular note this year was the presence of two sessions focused on what the group calls the “sleeping coal giants”: China and India.
“Of particular note was the session on China…they are probably doing more collective mining research than the rest of the world combined,” he said, adding that many of the country’s operations have made tremendous strides over the last few decades.
There is never one singular trend at any ICGCM event, and the 2016 gathering of some of the world’s top experts in ground control was no different. One thread that seemed to weave its way through so many presented papers, however, was safety. The group noted that the issue was looked at from many angles this year, as well as mine design, support design, monitoring techniques and even the growing hot topic of corrosion. Bolt performance and how boreholes and anchorage testing can “predetermine” it was another area of interest.
Tadolini, Barczak and Finfinger all largely concurred on the most talked-about — and potentially controversial — work presented at this year’s conference. One of those papers was “A Review of the Geomechanics Aspects of a Double Fatality Coal Burst at Austar Colliery in NSW, Australia, in April 2014,” given by Bruce Hebblewhite of the University of New South Wales (who authored the paper with Jim Galvin, also of the University of New South Wales).
“These ‘opinions’ are always difficult to get approval to present because the legal stakes are so high, and opinions in writing are seldom published,” he said of the presentation, adding that while the accident occurred in 2014, the emotions remain high and many maintain strong opinions of the events involved in the now-famous incident.
A second was another Australian paper, “An Assessment of Coal Pillar System Stability Criteria Based on a Mechanistic Evaluation of the Interaction Between Coal Pillars and the Overburden” by Russel Frith along with Guy Reed and Kent McTyer of Mine Advice in Newcastle. As Tadolini noted, the group sought to “stretch the paradigm” of pillar design with ideas that could turn some decades-long methods on their ear. The authors have also already promised a second part of their work will be presented at the 26th ICGCM next year.
“These are the types of papers that make researchers try different things and test other paradigms,” he said.
More than 200 individuals from the U.S. and seven other countries attended the 35th International Conference on Ground Control in Mining during late July.
35th ICGCM Highlights
There were 12 total sessions at this year’s conference: Fundamental Research Studies; Mine Case Studies and Operator Histories; Global Stability and Pillar Design; Support Performance Assessment; New Product and Equipment Developments; Indian Delegation; Chinese Delegation (two sessions); Ground Control Design Tools and Roof and Rib Control Strategies; Ground Instrumentation and Monitoring Studies; Subsidence and Surface Stability; and Numerical Modeling Studies and Design Applications. Each had an average of four presentations, scheduled throughout the day between July 26 and July 28.
Michael Gauna of the Mine Safety and Health Administration (MSHA) Safety and Health Technology Center in West Virginia submitted two insightful papers at this year’s conference, “Unanticipated Multiple Seam Stresses From Pillar Systems Behaving as Pseudo Gob: Case Histories” and “Preventing Roof Fall Fatalities During Pillar Recovery: A Ground Control Success Story.” Both were authored along with agency colleague and fellow ground control expert Christopher Mark.
In the first paper, the two discussed an issue with undermining and overmining where gob regions have the potential to result in abutment stress that can potentially have an impact on active mining.
“If there was no full extraction, and the past mining consists entirely of intact pillars, the stresses on the active seam are usually minimal. However, experience has shown that in some situations there has been sufficient yielding in overlying or underlying pillar systems to cause significant stress transfer to the active working,” the pair noted. “In other words, the overlying or underlying pillar system behaves as a ‘pseudo gob.’ The presence of a pseudo gob is often unexpected, and the consequences can be severe.”
In the first paper, the two discussed case studies showing pillar rib degradation at a West Virginia mine and a western Kentucky operations at an 1,100-ft depth where a rib roll fatality occurred, and pillar rib deterioration at an operation in western Kentucky (570-ft depth) that required an adjustment to pillar size as well as the installation of supplemental bolting. Studies were also presented on roof deterioration at an eastern Kentucky mine under 1,300 ft of depth that halted mine advance and required redirecting the section development, an eastern Kentucky coal burst (1,700-ft depth) with no nearby pillar recovery and a West Virginia coal burst in a development area that was sitting under a relatively shallow depth of 1,100 ft, also with no nearby pillar recovery.
“Miners must recognize that multiple seam stress can be encountered from overlying or underlying old workings where an inspection of the old workings maps indicates that interaction stresses are not expected,” Gauna and Mark concluded in their work. “Mining operations must exercise vigilance and immediately react when evidence of such stresses are encountered,” noting that hazards can be mitigated when pseudo gob stress is encountered using the guidance they offer in their research.
In the latter paper, the pair highlighted a sobering fact: pillar recovery accounted for a quarter of all roof fall fatalities in underground coal mines, and studies revealed that miners on pillar recovery sections are three times more likely to be killed by a roof fall than any other of his fellow miners.
Steve Tadolini, Syd Peng and Gerry Finfinger (along with Tom Barczak, not pictured) will continue to have involvement in ICGCM conferences going forward as advisors to the board.
Just one fatality has been recorded as a result of a pillar line roof fall since 2007 (when six miners and three rescuers were killed at Crandall Canyon), and Gauna and Mark examined the process that helped the industry mark the historic achievement that included the implementation of insights that have been discovered particularly since the turn of the new century.
“One key finding was that safe pillar recovery requires both global and local stability,” the two said, noting that global stability is addressed primarily through proper pillar design. This is an area that became developed with a significant focus after Crandall Canyon. The most significant improvements, however, resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions: leaving an engineered final stump, rather than extracting the entire pillar; enhancing roof bolt support, particularly in intersections; and increasing the use of mobile roof supports (MRS). Emphasis on better pillar recovery operations management was also spotlighted, such as worker positioning, pillar and lift sequences, MRS operations and hazard identification.
In short, while some challenges still remain, including bursts, Gauna and Mark concluded that many elements tied specifically to retreat mining have been made in mines’ roof control plans. “It has become clear that pillar recovery is not “inherently unsafe,” they added.
In the area of product development, Bill Kyslinger of West Virginia-based J.H. Fletcher submitted “Development of a Six-head Drillhead Roof Bolting Machine,” a unit the company designed, built and supplied to an Illinois operation an MSHA-approved six-head platform bolter capable of installing four roof bolts and two rib bolts with two to three operators, a significant increase in efficiency versus existing dual-boom fleets. The machine has been placed at the mine and has been working in production with great promise and some early successes, he pointed out.
“The feed and rotation controls at each operator’s station include a latch control for drilling. The latch control will allow the operator to lock in the feed and rotation once the hole has been collared, allowing the operator to move on to the next hole and start it,” he said. “Some additional guarding has been required by MSHA due to the unattended operator latched drill feed and rotation control. Some ergonomic issues have arisen because of the guarding, but ongoing changes are being worked out [right now].”
Many have an interest specifically in operator experiences, making ICGCM’s session on mine case studies a consistently well-attended portion of the program. One coal-focused highlight this year was “Safe, Efficient and Cost-Effective Support of Longwall Cut-through Entries,” authored by Benjamin Mirabile and John Poland of Pittsburgh-based Jennmar. The objective of the pair’s work and subsequent presentation was to demonstrate the use of fiber-reinforced concrete crib material as a method for standing support in longwall cut-through entries.
“Despite conceptions of poor performance in potentially high convergence environments, fiber-reinforced concrete crib material can be used in longwall support applications subject to high abutment loads,” the two said, adding that central to proper design is use of yield material between crib layers and mine roof/crib interface.
“The placement location of cribs within the cut-through entry has a significant effect on the main roof behavior and associated ground conditions in the longwall abutment zones.”
Mirabile and Poland concluded with their work that, for the potentially high convergence environments associated with longwall mining, fiber-reinforced concrete crib material can be used. They stressed the importance of engineering proper load-displacement characteristics of the installed crib to support expected ground conditions. This avenue is also much more cost efficient, as fiber-reinforced crib supports involved about half of the expense involved in backfilling methods.
In all, 56 papers were presented before the ICGCM audience.
A total of 56 papers were presented within 12 technical sessions, including operator case histories, fundamental research and ground control design studies.
Hosting Changes
The 2017 dates have already been set for ICGCM; it will return to the Lakeview Resort in Morgantown July 25-27. Attendees will likely notice a change at that event, as the Society for Mining, Metallurgy and Exploration (SME) will take over hosting duties for a five-year run at the West Virginia location.
Tadolini said the impetus for the change centered around SME’s history with conferences.
“While it is our passion and we love to do the conference, we are long in the tooth and this ensures the continuation of the conference,” he added.
A smooth transition between now and then is expected, and the group has already compiled a transition team to aid in the details of the endeavor. Tadolini, Barczak and Finfinger will all remain advisors to ICGCM, and conference founder Syd Peng will be intimately involved as well. ICGCM China will not be part of the transition.
For at least the next half-decade, the event will stay in Morgantown, though the three noted that the venue could potentially change after that. “With the shift in markets and the geographies of mining swings, there’s no telling where it can or would end up,” Tadolini said, noting that it has been in three other locations over the years: Chicago, Australia and CSM.
“SME has more vision on the global picture…and they are free to do what they think is best for the conference. And…Syd…will have a lot of influence on that decision.”
The group expects that, as in years past, an invitation for abstracts will be announced this fall. More information on this year’s conference as well as ICGCM China and upcoming events can be found at icgcm.conferenceacademy.com.
