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where parameters 6c cs and Npc are assigned separately for compressive (i.e., 63 > 0) and <br /> tensile stresses (i.e., 63 G 0). For compressive stresses: <br /> 6 a-1 <br /> Noy = 1 + a * mb (mb 3+ S) <br /> 6ci <br /> 6cucs = u3(1 — Noc) + aci (Mb 6 3 + S)a <br /> 6ci <br /> and for tensile stresses: <br /> N,pc = 1 + a * mb(S)a-1 <br /> ucs ( )a <br /> 6c = 6ci S <br /> where Hoek-Brown properties are defined in Section 5.1. <br /> For the local stability analyses, it is necessary to exclude from consideration the material <br /> outsize the region of interest for local stability failures (i.e., more than 3 benches above and 3 <br /> benches below the target bench). This is performed by assigning unrealistically large values <br /> of cohesion and tension (i.e., 1020 psf)to prevent failure in these regions. <br /> 6.3.4 Material Properties used in Stability Analyses <br /> Unit Weight <br /> A total of 28 rock samples were obtained for laboratory testing as described in Section 4. The <br /> reported unit weights of the tested samples ranged from 159.5 pcf to 171.7 pcf with an <br /> average unit weight of 164 pcf. The average unit weight or rock of 164 pcf was selected for <br /> use in stability analyses. <br /> Strength Properties <br /> Modified Hoek-Brown strength properties were used in the stability analyses and were <br /> developed separately for localized bench stability and global slope stability evaluations as <br /> presented in Section 5.1. The local bench stability evaluation was developed for highwalls as <br /> steep as 30H:70V with slopes as high as 250 feet. Strength properties were developed for <br /> localized bench stability using the Hoek-Brown method and account for disturbance due to <br /> blasting at the highwall face or rebound from stress relief. The global bench stability <br /> evaluation includes highwall slopes as high as 1,400 feet. Following the approach for local <br /> bench stability, strength properties were developed for global stability using the Hoek-Brown <br /> method and did not include a disturbance factor. <br /> 30 <br /> Aggregate Industries—Morrison Quarry GEI Consultants, Inc. <br /> AM-07 Geotechnical Stability Exhibit November 2020 <br />