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<br />TABLE 20-4 <br /> <br />UNIAXIAL COMPRESSIVE STRENGTH TESTS <br />SPECIMEN SIZE STRENGTH <br />NUMBER (HxWxL) psi <br />1 2.3X2.3X2.3 3,705 <br />2 2.1 X 2.1 X 2.1 2,481 <br />3 3X3X3 587 <br />4 3X3X3 596 <br />5 3X3X3 1,729 <br />AVERAGE <br />FACTORS OF SAFETY <br />Fnr 1R Fnnt WiriP Fntriac <br />1,820 <br />CAMEO - C Seam <br />PILLAR DEPTH OF COVER <br />SIZE 500 600 700 800 900 1,000 EXTRACTION <br />60' X 70' 2.83 2.36 2.02 1.77 1.47 1.33 48 <br />60' X 60' 2.48 2.06 1.77 1.55 1:::29 :.::::.:: ::::.:::::l;lf.:::: 51 <br />60' X 50' 2.25 1.88 1.61 1.41 1:.:04 :.::::: :::::::::0.94:::.:::: 53 <br />55' X 55' 2.07 1.73 1.48 1:.29::.::. ::::::1:.:08:::::: ::::.4'9:?::::: 55 <br />50' X 50' 1.68 1.40 I.20:: 1:05:::::: :::: 0<97:.::: ::::4:87::::: 59 <br />- Indicates pillar sizes that will not be utilized in the <br />Subsidence Control Zones under the Coal or Jerry Creek. <br />No pillaring will be allowed in the Subsidence Control Zones. <br />Volume 8 Tab 20 <br />Table 20-4 <br /> <br /> <br />5-13-99 <br />Z <br />b <br />W <br />