2008-11-24_PERMIT FILE - C1996083 (14)

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Geotechnical Evaluation of Mine-Induced Earthquakes on Bruce Park°Dam Bowie Resources, Limited June 2002 •) Consolidation stress at a specific depth in the dam was estimated by calculating mean effective stress at that depth based on the overlying materials and the water pressure conditions described in Section 3.5. Dynamic shear strength, which is what was used in the analysis, was considered to be 80 percent of static shear strength to account for possible degradation in strength due to cyclic loading. Selected material properties for each of the four material types are presented in Table 3.1. Maximum shear modulus for each material type was estimated using an empirical correlation developed by Weiler (1988) that relates maximum shear modulus to overconsolidation ratio, plasticity index, and undrained strength. As a result of shear strains caused by seismic loading, the shear modulus of the soil decreases and the damping characteristics of now-less- stiff soil increases. In the absence of laboratory data, we selected from typical modulus reduction curves and damping curves available in SHAKE that in our opinion reasonably represent the material types in the dam and foundation. The selected material parameters are summarized in Table 3.2. TABLE 3.1 MATERIAL PROPERTIES USED IN THE PSEUDO-STATIC ANALYSIS OF THE MAIN DAM ?J Material Type Moist Unit Weight c Saturated Unit Weight Soil Layer Number*(" Dynamic Undrained Strength s New Embankment 123 125 1 880 2 880 3 940 4 1,140 15 1,140 16 1,140 17 1,140 18 1,140 Old Embankment 118 122 13 1,470 14 1,470 5 1,490 6 1,630 7 1,780 8 1,930 Foundation Soils 126 126 9 1,770 10 1,890 11 2,010 12 2,130 Bedrock 133 139 19 11,200 Notes: (1) * - Refer to Figure 3.1 ,40 02-05-22 Geotechnical Evaluation of dine-Induced Earthquakes GEI Consultants, Inc. 9