2001-03-15_REVISION - M1977378 (3)

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Terry Tunnel Near Surface Bulkhead Construction Certification Report Page 3 Perimeter area irregularity The rock contact perimeter area irregularity required to develop the design compressive strength of the concrete when subject to the maximum design thrust was determined to be 8% of the area with a projection of 0.15" or more. Quantification of a minimum perimeter area irregularity was accomplished by measuring x- sections within the bulkhead length and using the generated x- sections to quantify intrusive area as a percentage of the total area between sections. A summation of the individual areas between x- sections was used for quantification of the total percentage of intrusive area within the bulkhead. This method provided an estimate of rock area irregularity of 39.5% which exceeds the design minimum of 8 %. Attached to this report are the x- sections and table generated to quantify that this requirement was met. Pumping of concrete, filling of forms and concrete compressive strength The same concrete mix that proved successful for the American Tunnel bulkhead was used for this bulkhead except that Type II cement was used instead of Type V. This change was made because Type V cement was not available at the time of the pour. Based on sulfate exposure criteria, Type V cement was not necessary and use of Type II cement and flyash exceeds recommended specifications for the anticipated exposure. The design engineer, John F. Abel Jr., addresses and approves of this modification in his attached report and the mix modification was addressed in TR -23, approved prior to the pour. The modified concrete mix was as follows: # /cu. yd. Portland Type II 720 Coarse Aggregate 1673 Fine Aggregate 1004 Fly Ash, Class F 115 Water 324 Delay Set Delay set was not needed in batches hauled dry and mixed on -site.