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Near surface concrete tunnel bulkheads can be safely designee to impound <br /> acid nine crater by considering the leakage potential along the concretefrock <br /> contact, the shear stress developed is the concrete and the rock. the bending <br /> moment resistance of the bulkhead. the hydrofracturing potential and the <br /> corrosion rates for the piping and concrete. L.ow-pressure grouting of the <br /> --- te/rock contact is recomaeaded to increase the hydraulic gradient <br /> resistance between the plug and the rock and to decrease the length of the <br /> bulkhead. The shear strength of the concrete and the rock must exceed the <br /> shear stress for the maxism head. 7M bending stress at the downstream face <br /> must either be kept below allowable plain concrete design tensile strength or <br /> steel tensile reinforcement must be placed near the dawn stream face to <br /> support the potential tensile stresses. The bulkhead must be installed at a <br /> depth srfficient to prevept Wrofracing the formation and the loss of acid <br /> water to the joint system. The corrosion rate of the piping through the <br /> bulu*W must be balanced by sufficiently thick pipe malls to provide for the <br /> 0 required minim i bulkhead life. <br /> The fiaat design of the Friday Lowden bulkhead as determined by the above <br /> analyses and presented as an example is shown on Figure 2. <br /> • • iDeferenoes <br /> Americn Concrete Iastitdteo 'Building code requirements for reinforced <br /> am eta (ACI 318413)'o: ACI (1983) , <br /> American Concrete Institute. 'Building code requirements for reinforced <br /> concrete (ACI 318-77)00 ACI (1977). <br /> G. Volffo V.S. Keys and E. Shuters aNydraulic fracturing to <br /> J.D. dreddaeft. R- <br /> determine the regional is situ stress field. Piceance Basis: Colorado'. <br /> GSA Bulletin r 07' (1976)9 P <br /> 6.J. Chekano 'Design of bulkheads for controlling water in underground mines'. <br /> - g58M Info Circ-9o2c (1985). 36 p:-- - - -- <br />