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January 2, 2020 Page 4-4 <br />Agapito Associates, Inc. <br />and charts are given in the “c” figures and represent the plan-view recovery within the panel <br />(between the barrier pillar centerlines). <br /> <br />The design curves provide Trapper with a rational starting point for web and barrier pillar <br />layout. By using these design curves to determine the minimum pillar width for each panel as <br />mining progresses, and adjusting that width as conditions warrant, maximum resource recovery <br />can be attained. <br /> <br />AAI recommends that HWM production panels be comprised of no more than 20 openings. <br />However, it is suggested that the initial panel in each seam contain only 10 openings. Assuming <br />no problems are encountered, subsequent panels can be mined with 20 openings. <br /> <br />4.3 Numerical Modeling of Pillar Design Cases <br /> <br />Numerical modeling, including efforts using the LAMODEL boundary-element method, <br />the Universal Distinct Element Code (UDEC) distinct-element method, and the FLAC3D™ finite- <br />difference method were preformed for typical web and barrier pillar designs for each of the Pits <br />and target seams to confirm the validity of the empirical pillar designs, study seam interaction, and <br />detect possible susceptibility to roof, floor, or rib instability. The modeling confirmed the pillar <br />designs, and no major issues were identified. Details of the modeling are fully discussed in each <br />individual pit report (AAI 2018, 2019a, 2019b). <br /> <br />