1995-07-12_INSPECTION - M1977378

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1 American Tunnel B head Construction Pac 2 July 12, 1995 positions with plastic attached to the face of the form and contact grout hole locations with faucet washers nailed the face of the form. The #6 shrinkage and temperature bars at the water-side end of the form were tied into the cage on the specified 12-inch spacing and the #6 bars had been tied into the waterside cage at approximately 4 inches from the bulkhead form. There were no splices used in either rebar cage. The corners of both the upstream and downstream pipe penetrations of the rebar cages had been reinforced by #6 rebar. The corner reinforcement installed where the bypass pipe passed through the upstream temperature and shrinkage rebar cage was not required because even though two bars had to be cut to permit the 12.750 outside diameter to pass through the rebar cage, i.e. the upstream shrinkage and temperature rebar performs no structural function. The irregularities present in the roof, ribs and floor are, by themselves, more than adequate to prevent the bulkhead from being forced down the American Tunnel. This is demonstrated by the roof-to-floor and wall-to-wall profiles. The largest irregularity present is an approximately 2-foot deep depression in the floor, about 7 feet upstream from the air-side form. Irregularities, an amplitude of greater than one foot, are present in the roof and walls inside the form. It will be impossible to force the bulkhead to move toward the portal without crushing the concrete. It is impossible to crush the 3000 psi design concrete strength American Tunnel bulkhead by applying the maximum possible 670 psi hydraulic pressure. The miners had done an excellent job of removing loose rock from the tunnel roof, walls and floor. I could not find any loose rock. There was no dust, mud or alteration products present on any of the rock exposed on the tunnel roof, walls and floor. The minor quantity of water near the water-side bulkhead form was vacuumed up after our inspection. After vacuuming up the minor quantity of ponded water and cleaning the form one last time, personnel exited the form. The nominal 12-inch diameter, actually 11.750-inch inside diameter, Schedule 80 (Extra Strong) 316L Stainless Steel American Tunnel Bulkhead bypass pipe was supported by circular concrete pedestals. The cylindrical pedestals provide a better support for the bypass pipe than the solid concrete block specified because they fully bear on the floor and they are wider than concrete blocks. The cardboard tube form for the pedestals had been removed prior to my inspection. Therefore, the bulkhead concrete pour should fully bond the pedestals. The maximum span between pedestal supports is 5 feet 10 inches. The original 5-foot design spacing between supports was based on two conservative assumptions, 1) a lower strength Schedule 40 (Standard Weight) pipe would be installed and 2) the pipe had to support 13 feet of concrete. The Schedule 80 bypass pipe installed was adequately supported by the concrete pedestals. The bypass pipe and the 1-inch diameter water pressure monitoring pipe were anchored into position by wire ties to rock anchors to prevent movement or distortion during filling of