ICGCM Papers:
Fundamental Research Studies
 
 
Design Concerns of Room and Pillar Retreat Panels
35th International Conference on Ground Control in Mining
Design Concerns of Room and Pillar Retreat Panels
by
Ted M KlemettiMorgan M SearsIhsan B Tulu, NIOSH, Office of Mine Safety and Health Research, Pittsburgh, United States
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[Conference] 35th International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Fundamental Research Studies
[Author] Ted M KlemettiMorgan M SearsIhsan B Tulu, NIOSH, Office of Mine Safety and Health Research, Pittsburgh, United States
[Abstract] 
Key Conclusions:
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In order to successfully retreat a R&P panel, there should be at least two different design analysis conducted. The first is during the planning phase and should rely heavily on engineering design procedures. These procedures should evaluate the loading, displacement, and timing of the mining planned. Factors of importance include the depth of cover, topographic changes, pillar design, panel design, mining height, geology of the roof and floor, faults, and rolling of the seam. The second evaluation should be done post development and/or during retreat mining, and should rely more heavily on the prevailing conditions of the area(s) to be mined. Evaluation of the amount of deterioration, pillar loading, and deformation that has occurred due to development, multiple-seam, and abutment loading if applicable prior to retreat mining should be performed. In addition, the amount of supplemental support installed, focusing on standing support, should be taken into account in deciding whether to leave the pillar or extract it.
Key Findings:
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Through both observation and instrumentation studies of four consecutive R&P retreat panels, there are several factors that should be highlighted. The primary focus was on the differences observed between the four panels and within the panels themselves. The instrumentation study was initially planned to evaluate the interactions between primary and secondary support, but produced rather interesting results relating to the loading encountered under the current mining conditions. In addition to the observation and instrumentation, numerical modeling was performed to evaluate the stress conditions. Both the LaModel 3.0 and Rocscience Phase2 programs were used to evaluate these four panels. The results of both programs indicated a drastic reduction in the vertical stresses experienced in these panels as well as increases at the gob-solid boundaries. Both programs showed a higher level of stress associated with the outside entries of the panels. These results agree quite well with the observations and instrumentation studies performed at the mine. The following factors should be considered during R&P retreat mine planning and execution: 1. Topographic relief in panel leads to very different conditions than those associated with relatively flat overburden. 2. An overlying gob can relieve a large portion of the overburden pressure, as evidenced from the four panels observed. 3. As the entries get closer to the overlying gob solid boundary, the condition of the entries appear to encounter higher stresses leading to more roof and rib deterioration. 4. Geological changes in the immediate roof can significantly affect the condition of the entries depending on the stress regime encountered.
Objective of the Paper:
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To determine the relevant factors influencing the conditions of Room and Pillar (R&P) Retreat mining entries. To reinforce the influence of topographic changes, depth of cover, multiple seam interactions, geological conditions, and mining geometry.
Problem Statement:
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Why do some room and pillar retreat panels encounter abnormal conditions? What factors deserve the most consideration during the planning and execution phases of mining and what can be done to mitigate those abnormal conditions when they are encountered?