Mining Contract: Conduct Numerical Modeling to Meet the Requirements of the 2008 Congressional Appropriations Bill
The safety of deep cover mining depends largely on proper pillar design to ensure that the overburden rock mass is well supported by unmined areas of the mine. One of the common methods used for mine planning is a numerical modeling simulation of rock mass response and pillar loading using a computer program called LaModel, so named because of the laminations of the rock layers above the coal seam. As with any numerical method, the success and accuracy of the LaModel program is largely dependent on the accuracy of the input parameters, and these parameters need to be specifically calibrated to the unique conditions at the specific mine. To improve upon LaModel, what is needed is a "standardized" method of calibrating the program that has been thoroughly evaluated and verified through actual case studies.
Contract Status & Impact
This contract is complete. To receive a copy of the final report, send a request to OMSHR@cdc.gov.
On August 6th, 2007, the Crandall Canyon Mine in Utah collapsed, trapping six miners. Ten days later during the heroic rescue effort, another collapse occurred, killing three of the rescue workers. At the time of the collapse, the Crandall Canyon Mine was performing pillar retreat mining at cover deeper than 1,500 ft.
The Crandall Canyon catastrophe underscored the importance of design tools like LaModel in providing safe workplaces for miners involved in deep cover pillar recovery. Under this contract, a research team at West Virginia University developed software wizards to provide improved recommendations for critical LaModel input parameters. This team also analyzed case studies of deep cover retreat mining and compared LaModel results with those from the NIOSH-developed Analysis of Retreat Mining Pillar Stability (ARMPS) software. ARMPS is an empirically based assessment of pillar design that utilizes data from past deep cover mining cases to define successful and unsuccessful mining plans. ARMPS provides adequate design solutions for most simple situations, but LaModel provides more flexibility for the complex geometries and multiple seam situations that are often encountered. The verification of the program applications and revised input parameter selection should guide mine planners in the use of LaModel in conjunction with ARMPS, thereby providing optimal pillar designs that will prevent such tragedies as Crandall Canyon from recurring.
Under this contract, a major revision to the LaModel program was completed. This revision included several parameter input wizards that will develop calibrated material properties for users of all levels. These wizards significantly simplify the program and provide consistent application for even novice users. The newly developed version of LaModel was used to compare pillar loading, pillar stability factors, and design guidelines with the ARMPS program, which is the most widely used pillar design software. This comparison proved to be favorable for LaModel and provides users with a more flexible tool to evaluate complex pillar designs under variable topography.