Laserfiche WebLink
I <br />4-2 <br />• The dam was modeled as a single material representative of the core <br />s material because only direct information on the character of the core <br />material was available. Likely variation in strength between the core <br />and shell zones is not considered large and the suspected coarser <br />character of the shell zones should provide a higher friction angle for <br />the shell material than the core. Assuming the entire dam to be <br />equivalent to the strength of core material is considered to be conser- <br />vative. <br />The geometries of the geologic and analytical models'are very similar as <br />shown, with the major difference being the use of straight line segments <br />to simplify the analytical model. <br />4.1.1 Material Properties <br />Available data, laboratory test results, and previous experience with <br />similar materials were used to select representative strength and <br />density values for each of the five material types in the analytical <br />model. The material properties used in the stability analysis are <br />presented on Figure 8 and discussed below. <br />Effective strength properties selected for the dam fill (material Type <br />1) were based on a review of field data (boring logs and standard <br />penetration resistance "N" values), previous and current laboratory data <br />and experience with similar soils on other projects. The selected <br />values were: <br />- Angle of Internal Friction = 33" <br />Cohesion - 300 PSF <br />The fill material was logged mainly as clayey or silty sands with <br />occasional cobbles or rocks. The "N" values indicate that the material <br />is mostly medium dense. Strength values from laboratory direct shear <br />tests were available from Dames and Moore (1975), however, the results <br />i n0 <br />