dynamic force distribution is cumbersome were deciding factors in selecting 

 the simplied loading diagrams. 



b. Causeway Construction Procedures - The bid documents provided for 

 five optional combinations of steel pipe or prestressed concrete piles 

 with steel or concrete caps, steel stringers and timber deck, or 40-foot 

 prestressed concrete slabs. Pile emplacement alternates were driving, 

 driving and jetting, or drilling and grouting in the shale rock. It was 

 presumed that driving might be practical for the steel pipe pile alter- 

 nate, but that drilling and grouting would be required for concrete piles 

 near shore. 



The low bid submitted was for steel piles, steel caps and stringers, 

 and timber deck. Before final award of the contract, two test piles were 

 driven into rock on shore to determine whether or not it would be necessary 

 to drill and grout the steel pipe piles. The 16-inch-diaraeter test piles 

 with 0.5-inch-thick walls were successfully driven with a heavy drop hammer. 

 As a result of these tests, the option of driving the steel piles was 

 selected; a lump sum contract was awarded on that basis. 



The contractor's construction plan was to build a temporary work 

 trestle of his own design from which the piles for the causeway were driven 

 by a heavy drop hammer handled by a small crawler crane. Stringer assem- 

 blies were shop- fabricated and placed by a truck crane operating on the 

 work trestle. The cap connection to the piles consists of a stiffened 

 connection plate welded to the bottom flange of the cap, which fits into 

 vertical transverse slots in the piles as shown in Figure 15. The work 

 trestle afforded ready access for aligning the piles and cutting the slots, 

 and thus made the erection work a simple operation. Construction of the 

 work trestle paced the causeway erection work. 



Specified pile penetration for the typical single-pile and double- 

 pile, transverse-battered bents was 8 feet into the shale formation or a 

 minimum penetration of 20 feet into other materials and a driving resis- 

 tance giving not less than 45-ton safe load by use of the Engineering News 

 Record (ENR) pile driving formula. Required penetration for the four 

 longitudinally-battered bents was 50 percent greater. Pile dimensions 

 ranged from 16-inch diameter, 0.375-inch wall at the shore end to 24-inch 

 diametei, 0.563-inch wall for the deepwater longitudinally-battered bents. 

 All piling was sandblasted and coated with coal tar enamel. The expansion 

 joints are semi-insulated for a cathodic protection system. Concrete pipe 

 sleeves were installed at the bottom line on the first nine nearshore bents 

 as a precaution against sand abrasion. 



Work on the causeway started in November 1957; the first vehicles 

 crossed in July 1958. The 26 January 1958 storm caused about 1 month's 

 delay by knocking over about 750 feet of the contractor's temporary work 

 trestle. Only the onshore abutment of the causeway had been completed 

 at this time. 



45 



