Results 41 - 50 of 77

• Effect of the Dip and Excavation Orientation on Roof Stability in Moderately Dipping Stone Mine Workings
  1/1/2005 - Conference papers
  In some underground limestone mines, the dip may exceed 5°. This can cause roof instability, which can be exacerbated by horizontal tectonic stresses. Field studies and numerical model analyses assess the effect of dip in various stress conditions.
• Preventing Falls of Ground in Coal Mines With Exceptionally Low-Strength Roof: Two Case Studies
  8/1/2004 - Conference papers
  Mines with low-strength roof are much more likely to struggle with roof falls. This paper focuses on two mines in two different seams, conducting statistical analysis to determine which support combinations have proven to be most effective.
• Numerical Modeling for Increased Understanding of the Behavior and Performance of Coal Mine Stoppings
  8/1/2004 - Conference papers
  In underground coal mines, concrete block stoppings are widely used to control mine ventilation. Researchers developed a numerical model to evaluate the performance of stopping materials and different wall geometries in a controlled environment.
• Hydraulic Prestressing Units: An Innovation in Roof Support Technology
  8/1/2004 - Conference papers
  A new generation of hydraulic mine support prestressing devices has been developed. This paper examines the performance capabilities of these inflatable prestressing units and the impact they have on the performance of various support systems.
• Investigation of Pillar-Roof Contact Failure in Northern Appalachian Stone Mine Workings
  8/1/2004 - Conference papers
  Underground limestone mine roofs in Northern Appalachia can be subject to high horizontal stresses. A case study is presented showing that induced stress changes in the immediate roof are less likely if the pillars contain weak bedding planes.
• UDEC Modeling of an Underground Opening in a Rock Mass of Varying Quality
  5/1/2004 - Conference papers
  This paper describes a project involving modeling rock masses with varying Rock Mass Rating (RMR) values to determine the degree of instability that develops around an underground opening as a function of RMR.
• Design Parameters of Roof Support Systems for Pre-Driven Longwall Recovery Rooms
  2/1/2004 - Conference papers
  A calibrated three-dimensional finite element model, developed in conjunction with an underground test area, provided the critical components and design principals for a comprehensive parametric study.
• Reducing the Risk of Ground Falls During Pillar Recovery
  12/1/2003 - Conference papers
  Pillar recovery has been associated with nearly one third of roof fall fatalities in underground coal mines during the past decade. This paper discusses design methods and technologies that have been transferred and implemented in mining.
• Pumpable Roof Supports: Developing Design Criteria by Measurement of the Ground Reaction Curve
  8/1/2003 - Conference papers
  Pumpable roof supports provide an alternative longwall tailgate roof support and have grown in usage recently. Despite the success of these supports, questions remain regarding critical design issues for optimizing the use of this technology.
• New Tools for Roof Support Evaluation and Design
  8/1/2003 - Conference papers
  This paper describes two tools NIOSH developed. The miniature data acquisition system (MIDAS) could make geotechnical instruments in underground mines more feasible. The rock strain strip, together with MIDAS, more accurately measures rock movement.