Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />~ <br /> <br />high tensile stresses. It should be noted that the existing one-inch twisted <br />steel rebar spaced on one foot centers, the steel rebar to be embedded in the <br />upstream shotcrete face, and the rock bolts placed in compression will carry <br />additional tensile stresses and help alleviate any tension cracking. <br />A pseudo-static earthquake analysis of the repaired structure was con- <br />ducted assuming a 0.16g horizontal acceleration. Maximum estimated compressive <br />stresses for this "extreme" loading combinatio~ were 149 psi, which are less <br />than the specified compressive strength of 4,000 psi for the repaired dam. The <br />maximum estimated tensile stresses were 51 psi. Tensile strengths of five NX <br />cores from the existing dam ranged from 265 psi to 1,086 psi with an average of <br />693 ps i. <br /> <br />VII 1. DAM REPAIR <br />The goals behind a successful repair of Bluebird Dam are to produce a <br />coherent load carrying arch that is both resistant to temperature degradation <br />and to relatively high tensile stresses. It is desirable to reduce the amount <br /> <br />, <br />of equipment, materials, and manpower required so that repairs can be performed <br />economically and with minimal environmental impacts. We recommend that a com- <br />bination of reinforced shotcrete, low-pressure grouting, and tensioned bolts be <br />used to repair the structure. A typical repair section is shown in Figure 11. <br />Water Diversion <br />- <br /> <br />A diversion structure should be prepared in Mayor early June prior to a <br />water elevation rise caused by snow-melt runoff. The cofferdam can be built <br />about 100 feet upstream of the lower outlet at a natural rock outcrop at the lip <br />of the cirque. Remnants of the 1918 cofferdam, a one foot thick concrete wall, <br />are still evident at this location. We believe that adequate draw down and <br />resulting freeboard can be accomplished by siphoning and pumping from the <br />natural lake to a point downstream of the existing dam. The cofferdam should be <br /> <br />-24- <br />