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Geotechnical Evaluation of Mine-Induced Earthquakes on Bruce Park Dam <br />Bowie Resources, Limited <br />June 2002 <br />Section 4 - Landslide Stability <br />Analvsis <br />4.1 General <br />We evaluated the stability of the existing landslide using the following procedure: <br />• Estimated the pre-failure geometry of the slope and performed static stability analyses <br />to estimate the likely shear strength and pore pressures along the probable failure <br />plane at the time of failure. This is referred to as the "back calculated" shear strength. <br />• Estimated the shear strength of the materials along the probable failure plane based <br />on information from the borings and laboratory tests performed on materials in the <br />landslide (GEI, 2002). <br />• Performed a static stability analysis of the existing landslide (post-failure geometry) <br />• using the strengths estimated from the above analyses. <br />• Evaluated probable permanent deformations of the existing landslide from mine- <br />induced ground motions using the methods presented in Section 3. <br />The overall stability analysis for the landslide was similar to that for the main dam (Section <br />3.1) except we used the modified Janbu method with block-type failure surfaces for the <br />landslide analysis. <br />4.2 Pre-Failure Static Stability Analysis <br />4.2.1 Representative Cross Section <br />Using the existing topography around the landslide and information from the borings drilled <br />in the landslide (GEI, 2002), we developed a section to represent the pre-failure conditions. <br />We represented the subsurface stratigraphy with three layers: firm glacial till underlain by a <br />1-foot thick "failure zone", which is considered to be reworked glacial till, over bedrock. <br />This representative section is shown on Figure 4.1. <br /> <br />02-03-22 Geotechnical Evaluation of Muic-Induced Earthquakes <br />GEI Consultants, Inc. 12