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. Table 6. Effective Stress Shear Strength Parameters of Gob <br />From CU Triaxial Testing <br />Sample Borehole ~' Cohesion, <br />ID ID (degrees) c'(psf) <br />BS-3 N/A 31 330 <br />SH-1 8G05-05 34 60 <br />SH-2 BG05-06 33 60 <br />4.2.4 Consolidated-Undrained (CU) Triaxial Testing on Foundation Soils <br />One CU triaxial test with pore pressure measurement was conducted on athin-walled sample of <br />the foundation soils at Gob Pile No. 3. The sample (ST-3) was tested at three different <br />consolidation pressures (20 psi, 40 psi, and 80 psi). The results from the CU triaxial test data <br />were used to estimate effective stress strength parameters (Mohr-Coulomb Q' and c') for ]ong- <br />term stability analyses. Table 7 presents the effective stress parameters determined of foundation <br />soils determined from the CU triaxial tests. Laboratory data from the testing are presented in <br />Appendix D of this report. <br />Table 7. Effective Stress Shear Strength Parameters of Foundation Soils <br />From CU Triaxial Testing <br />Sample Borehole ~' Cohesion, <br />ID ID (degrees) c'(psf) <br />ST-3 BGO6-04 39 0 <br />5.0 STABILITY EVALUATIONS <br />Slope stability of the proposed Gob Pile No. 3 was evaluated using two-dimensional limiting <br />equilibrium stability analyses with [he computer software SLIDE developed by Rocscience <br />(2004). The factor of safety was determined for critical circular and block-type failure surfaces <br />using total and effective stress analyses. The simplified Bishop and Spencer procedures were <br />used and only static loading conditions were evaluated. <br />5.1 Cross-Sections and Geometry <br />Stability of [he proposed gob pile was evaluated for three cross-sections, as indicated on <br />Drawing 2. Cross-section A-A' is anorthwest-southeast trending section at the maximum cross- <br />section of the gob pile. Cross-section B-B' is transverse to Section A-A'. Section C-C', roughly <br />parallel to Section A-A', is located at the southern portion of the gob pile with a smaller crest <br />area and smaller cross-sectional area. This section is considered representative of the northern <br />portion of the gob pile. <br />Cross-section A-A' is considered the critical section due to its maximum cross-sectional area, <br />• deepest footprint distance (approximately 580 feet), and potential for maximum height. Various <br />slope geometries were evaluated for the proposed gob pile with an objective of determining <br />Bowie Gob Pile No. 3 stability report <br />Project #06-481-002 <br />Page I I of 17 <br />