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Terry Tunnel Bulkhead <br /> Construction Certification Report <br /> Page 4 <br /> During the pour , 6 separate samples (4 cylinders) were taken <br /> for break tests. The approximate cumulative yardage points <br /> where sampling occurred were 1) 2 . 9 yards , 2) 7. 9 yards , 3 ) <br /> 12 . 9 yards, 4) 17. 9 yards, 5) 22. 9 yards and 6) end of pour <br /> (26. 9 yards) . The cylinders were cured at the bulkhead site <br /> until time for break tests. Test cylinders from each sample <br /> were broken at 7 days and 28 days with the remaining cylinders <br /> being saved for retest if required . <br /> The average break strength at 7 days was 4297 psi and at 28 <br /> days it increased to 5270 psi with the lowest break being 4320 <br /> psi at 28 days. All tests exceeded toe 3000 psi compressive <br /> strength required by design, therefore no additional testing <br /> was done or planned . The test reports are attached . <br /> 4e) Low pressure grouting of the concrete-rock interface. <br /> Drilling and grouting of the Terry Tunnel bulkhead was started <br /> on 9/22/94 and completed on 9/26/94 . Initially, a total of 10 <br /> holes were drilled into confirmed rock . The targeted contact <br /> intersection points were at the approximate center of the <br /> bulkhead at the left rib-sill intersection, left rib midway <br /> between sill and back , left rib-back intersection, back <br /> center , right rib-back intersection., right rib midway between <br /> sill and back , right rib-sill intersection. Additional <br /> targets were a wide spot in the left rib, a short back hole to <br /> the right of bulkhead center between the center and face of <br /> the bulkhead and a long back hole between the center and back <br /> of the bulkhead. All of these holes pressured to 200 psi with <br /> minimal take although the left rib-back intersection hole took <br /> a little grout. <br /> An additional back hole was drilled to within a foot of the <br /> back face of the bulkhead . This hole took grout and would not <br /> build pressure. Because access was available to the back <br /> face, grout was observed flowing along the concrete-rock <br /> contact in the back . Grouting was stopped at this point for <br /> the day. <br /> On 9/23/94 this hole was redrilled into rock contact and <br /> grouted . Grout pressure could only be built to 80 psi . Grout <br /> was again observed f lowing from the contact at the back of the <br /> bulkhead . Grouting was again stopped . On 9/26/94 this hole <br /> was again redrilled into rock contact and grouted . Grout <br /> pressure built to 200 psi with no take . A new hole was <br /> drilled to rock contact within one foot of the back bulkhead <br /> face to the left of the hole just grouted as a check on <br /> contact grout job completion. This hole immediately <br /> pressured to 200 psi with no grout take . <br />