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Sunnyside Gold Corp. Page 6 March 10, 1993 <br /> more steel per splice with #10 bars. A single #10 bar for the <br /> American Tunnel bulkhead weighs only 56 lbs. For the #6 bars a 48 <br /> inch development length is recommended. For the #4 bars a 32 inch <br /> development length is recommended. <br /> The acceleration from the "maximum credible earthquake" for <br /> the Sunnyside Mine area was conservatively applied to all bulkhead <br /> orientations and checked against ACI code requirements for <br /> earthquake loading. All design bulkheads exceed ACI code <br /> requirements. <br /> INTRODUCTION <br /> The bulkhead designs contained in this report have been <br /> conservatively prepared. Conservatism was necessary because of the <br /> safety and environmental implications of a bulkhead failure, the <br /> long life required for the bulkheads and the ultimate <br /> inaccessibility of the bulkheads. The American Concrete <br /> Institute's "Building Code Requirements for Reinforced Concrete <br /> (ACI 318-89) " was utilized because the bulkheads are analogous to <br /> reinforced deep-beam concrete structures and because of the <br /> inherent conservatism of the code. The deep-beam bulkhead was <br /> further, conservatively assumed to act only one-way, between the <br /> walls, ribsides, of the tunnel. However, two-way reinforcing steel <br /> is provided in the design to transfer the load to the roof and <br /> floor. The one-way design assumption in effect produces a factor <br /> of safety of two, provided the more difficult roof and floor <br /> contacts between the bulkhead concrete and the rock is achieved. <br /> The blasted irregularities along the tunnel roof, walls and floor <br /> effectively key a bulkhead to the adjacent rock. The American <br /> Tunnel calculations are presented in Appendix A. <br /> The U.S. Bureau of Reclamation's manual for the "Design of <br /> Small Dams" (USBR, 1977) was not utilized because only one of the <br /> three failure criteria for dam stability is even remotely involved <br /> in bulkhead design, namely, sliding on the base of the dam. The <br /> other two criteria, overturning of the dam and piping of water <br /> through and erosion of the foundation material under the dam are <br /> not pertinent to bulkheads. The driving force tending to move a <br /> dam is the hydraulic thrust against the dam face. The sliding of a <br /> mass concrete dam is resisted by the weight of dam and the <br /> coefficient of friction between the concrete and the rock on which <br /> the dam sits. Kvapil (1965) reports coefficients of surface <br /> friction between concrete and granite ranging from 0.70 to 0.90. <br /> If the bulkhead were simply sitting on the rock floor of the <br /> tunnel, frictional resistance of the approximate 320 ton reinforced <br /> concrete bulkhead planned for the American Tunnel would not prevent <br /> the bulkhead from being pushed down the tunnel by the over 8100 <br /> tons of design hydraulic thrust applied to the water-side of the <br /> bulkhead. The irregular blasted surface of the tunnels and the <br /> intimate contact between the concrete bulkheads and the rock roof, <br /> walls and floor of the tunnels permit a bulkhead to resist the <br /> applied thrust. The only way a bulkhead can fail in shear is by <br /> shearing through intact concrete or rock, not frictional sliding. <br />