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December 27, 2023 Page 7-1 <br />Agapito Associates, Inc. <br />7 GROUND CONDITIONS ANTICIPATED DURING PILLAR EXTRACTION <br />The use of MRS enhances the safety of personnel by (1) providing a more effective ground support, <br />(2) reducing worker exposure near the gob edge, and (3) eliminating a major cause of material <br />handling injuries (Mark et al. 1995). Given the wide range in roof lithology, the ground conditions <br />in Sunset Mains South are expected to be variable during lifting. In most areas, caving up to the <br />rear of the MRS is anticipated, particularly in the areas where double lifting is utilized. General <br />experience suggests that the highest geotechnical risk during pillar extraction when using the <br />Christmas tree method is pushout removal and retreating up to intersections. With regard to <br />pushout removal, the pushout should only be removed if the roof exhibits good competency and <br />the operator is experienced in this manner. Particular attention should be given to intersections, as <br />past experiences demonstrate that intersections, particularly 4-way intersections, are most prone <br />to roof falls during pillar extraction. <br />In addition to the above, local geotechnical anomalies also require attention. Particular attention <br />should be given to locally poor roof conditions, particularly in any joint and/or fault zones. These <br />areas should be assessed by an appropriate mine official for the need of supplementary support <br />prior to lifting. Poor ribs should be scaled to remove loose material prior to lifting. No extraction <br />should be conducted from a roadway that has spalled to a width of >25 ft prior to lifting unless the <br />area has first been inspected by an appropriate mine official and a remedial roof support strategy <br />developed. <br />As mentioned previously, the gob edge is controlled by a set of two MRS placed on the gob side <br />of the lift. The MRS should be kept as close as possible to the continuous miner during the lifts. <br />As the lifts approach the outby intersection, another set of two MRS should be installed in the <br />outby crosscut between the pillar being mined and the previously mined pillar in the same pillar <br />row. In regard to the use of the MRS, the following guidance is critical in maintaining control of <br />the gob: <br />The MRS should be moved as often as possible to kept them as close as possible to the <br />continuous miner to reduce the possibility of premature roof caving. <br />When moving the MRS during pillar extraction, each MRS should be advanced no more <br />than one-half the length of a canopy and pressurized against the roof before the second <br />MRS canopy is lowered and trammed forward a similar distance and pressurised against <br />the roof. <br />The canopy should not be lowered more than necessary to clear roof obstructions during <br />advancement. <br />The MRS should be set against the roof with just enough force to make contact with the <br />immediate roof. <br />Lower setting pressures should be used in weak immediate roof. This is an important factor <br />considering the amount of soft mudstone and shale logged in the immediate roof in the <br />Sunset Mains. <br />In regard to the life-of-mine roadways, accepting that the modeling indicates roadways should be <br />isolated from any large surges in vertical stress, it is nonetheless recommended that the adequacy <br />of the existing roof support is assessed. Prior to pillar extraction, the roadways should be inspected