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<br />r? <br />• <br />field horizontal stress in the vicinity of the Hubbard Creek. Table 1 provides a summary <br />of these measurements. <br />Table 1-Far-field measured horizontal stress in the BRL properties. <br />Site Depth of <br />cover, ft Max stress (P), psi Min stress (Q), psi Orientation of P <br />1 (Orchard Valley) 340 1,100 240 N 690 E <br />2 (Orchard Valley) 1,625 1,630 480 N 830 E <br />3 (D Seam, Bowie No. 2) 1,000 1,330 245 N 850 W <br />Overall trend N 800 to 900 E <br />Regional measurements show excess horizontal stress in the Somerset Coal Field along <br />the regional structural trend (N 74° to 80° E). Horizontal stress is only gravity induced <br />along the secondary direction (N 10° W). The excess stress is moderate, but increases <br />with depth (table 1). The far-field horizontal stress is very anisotropic in this basin. The <br />ratio of maximum to minimum secondary principal horizontal stress (P/Q ratio) is <br />approximately 4 to 6 (Maleki and others 1997). The orientation of maximum principal <br />stress is consistent, trending east-west near the BRL properties. It is possible that some <br />stress reorientation and concentration may be found near stream valleys. This may result <br />in the yielding of immediate roof layers, particularly if laminated, thus requiring support. <br />The yielding will be limited to the immediate roof rocks (within one diameter of the <br />opening if this occurs) and can be controlled through a high density of support. Mains <br />reorientation, if practical, may also prove helpful in enhancing immediate roof stability <br />and reducing support requirements. <br />3.3 Mechanical Properties <br />Mechanical and strength properties for coal-measure rocks and the C Sandstone are <br />reviewed here for addressing rock mass strength characteristics over the mains. Rock <br />mechanics tests are available from selected intervals along the two inspected coreholes. <br />The tests include- <br />• Uniaxial compressive strength (UCS) <br />• Young's modulus (E) and Poisson's ratio <br />Maleki Technologies, Inc. <br />Page 8