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I I I I I I I I I I I I I I I I I I I TABLE I RCC AND ROCK PROPERTIES USED IN DESIGN MATERIAL COMPRESSIVE FRICTION COHESION UNIT STRENGTH ANGLE (psI) WEIGHT (psl) (degrees) (ocf) FOUNDATION N/A 46 17.4 & 0.0 190 ROCK RCC 2000 45 20,0 & 0.0 160 c. Stablllty Analysis, The stablllty of the dam was determined using the procedures outlined In the DESIGN OF GRAVITY DAMS, Design Manual For Concrete Gravity Dams, Bureau of Reclamation, 1976 and ROLLER COMPACTED CONCRETE DAMS, by Hansen and Reinhardt. The design method employed Is a two dimen- sional gravity analysis of the loads acting on the dam. No flnlte element or twist type of analysis was conducted on the dam, Three sections were analyzed and Tab]e 2 summarizes the factors of safety determined for each condition analyzed, The three sections analyzed were at Stations 0+26, I +26, and 2+26. The conditions analyzed are USUAL, UNUSUAL, AND EXTREME. The loads utlllzed for the three conditions are as outlined In the DESIGN OF GRAVITY DAMS. The slldlng and overturning etablllty of the dam has been determined assuming full hydrostatic uplift as the dam has no Internal drainage system. There are drains at the toe of the dam beneath the plunge pool, however, these were not Included In the calculations. For sliding at the lifts, the Internal pore pressures In the dam were assumed to be full hydrostatic at the upstream face and to vary linearly to zero at the downstream face due to the drains and high permeablllty of the downstream glacial till. The required factors of safety for each condition analyzed are summarized In Table 2. The sliding resistance of the dam at Station I +26 was also checked assuming no bond (cohesion) between the RCC lifts or between the RCC and foundation rock and are summarIzed In Table 9. The factors of safety required for thIs condition were taken from "DAMS ON ROCK FOUNDATIONS-SOME DESIGN QUESTIONS". by Don U. Deere, ASCE Specialty Conference, Rock Enl!lneerlng For Foundations and Slopes, August 15-18, 1976, Boulder, Colorado and also based on engineering Judgement. The required factors of safety for this condition are much less than when bond Is Included In the calculations. This Is due to the stability being based only on the normal force on the plane being analyzed and the angle of friction of the materiaL The angle of friction Is not as dlfflcult to determine and Is not as variable. The eliding resistance of the dam at Station 1 +26 was also checked for the USUAL condition assuming overtopping of the dam had occurred and removed all PAGE 3 Peterson Lake Dam Deelgn Report