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Bruce Park Landslide Project No. 25-196 <br />Bowie Mine #2 <br />I? <br />L <br />The soils encountered in the borings (piezometers) consisted of sandy clay and clayey <br />sand underlain by sandstone and/or shale bedrock to the maximum explored depth of 22 feet. <br />Inclinometers were drilled as much as 26 feet deep. The clay and sand was encountered to <br />depths of 3.5 to 17 feet. The clay was medium stiff to very stiff, the sand was loose to medium <br />dense and the bedrock was medium hard to very hard based on field penetration resistance <br />testing. The clay samples tested had 74 to 99 percent silt and clay (material passing the No. <br />200 sieve). Atterberg limit test results indicated the clay had liquid limits of 33 to 56 percent and <br />plasticity indices of 16 to 36 percent. Three clay samples from depths of less than 10 feet had <br />unconfined compressive strengths of 3,400 to 4,400 psf. The laboratory test results are <br />presented in the Summary of Laboratory Test Results table in Appendix B. The clay classified <br />as silty to sandy, low to high plasticity clay (CL and CH) based on the Unified Soil Classification <br />System (USCS). <br />Two samples were submitted to Advanced Terra Testing, Inc. (ATT) for direct shear <br />testing. ATT reports the peak and ultimate shear stress. For discussion in this report, the <br />ultimate strength is considered the residual strength. The test results for peak and ultimate <br />(residual) strength values are presented in the following table: <br />Table 1 - Direct Shear Strength Testing <br />Sample P-2 at 11 feet P-6 at 4 feet <br />Liquid Limit 33% 53% <br />Plasticity Index 17% 36% <br />Minus No. 200 sieve 74% 99% <br />USCS Classification CL CH <br />Peak Friction Angle, 33 degrees 25 degrees <br />Peak Cohesion, c 242 psf 858 psf <br />Ultimate (Residual) <br />Friction Angle, ? 33 degrees 25 degrees <br />Ultimate (Residual) <br />Cohesion, c 186 psf 261 psf <br />• <br />3