In the design of coastal structures subjected to high breaking waves, the designer finds that conventional structures constructed with natural stone became impracticable. When the design wave exceeds about 10 meters (30 feet), current practice normally dictates the use of artificial concrete blocks of various shapes which are relatively more stable than stone. A review of published stability coefficients for armor units indicates that the Dolos shape yields the most stable structure for a given weight of unit of any non-articulated shape known. After review of published literature and laboratory testing, a design for rehabilitation of the seaward heads of the Humboldt Jetties at the entrance to Humboldt Bay, California, U.S.A., was formulated using Dolos of 38 metric tons (42 short tons) and 39 metric tons (43 short tons), with specific weights of 2.5 t/cu. m. (155 pounds/cubic feet) and 2.6 t/cu. m. (160 pounds/cubic foot), respectively. The design wave for these structures is 13 meters (40 feet) breaking directly on the structure. This is believed to be the highest design wave described in the published literature for a flexible structure. A summary of results of the hydraulic model tests conducted for this project is presented in the paper. In order to reach a stable section, calculation indicated that high specific weight concrete would be required in the transition between circular head and the existing jetty trunk. Additional investigations of the effect of armor unit specific weight on stability is required in order to take full advantage of this effect. Consideration is being given to prototype testing of very heavy specific weight concrete in the range of 3.2 t/cu. m. (200 pounds/cubic foot). Based on experience at several coastal structures using concrete armor units larger than about 18 metric tons (20 short tons), it was concluded that the Dolos units used at the Humboldt Jetties should be reinforced and that the geometric section should be slightly modified. Review of available literature indicates that little factual information is available to quantify the decision for placing steel in concrete armor units. Additional research is urgently needed on this subject. Full scale prototype testing of unreinforced Dolos is also being considered at the Humboldt Jetties. Casting of the Dolos is underway and it is expected that Dolos placement will commence in the summer of 1971 on the Humboldt South Jetty and on the North Jetty in the summer of 1972. Placement will be entirely by mobile land-based equipment carefully controlled to insure the desired position of armor units underwater.

  • Supplemental Notes:
    • Abstract of paper delivered at the First International Conference on "Port and Ocean Engineering under Arctic Conditions" held at Trondheim, Norway, August 23-30, 1971
  • Corporate Authors:

    POAC Conference

  • Authors:
    • Magoon, O T
    • SHIMIZU, N
    • Weymouth, O F
  • Publication Date: 1971-8-23

Subject/Index Terms

Filing Info

  • Accession Number: 00025676
  • Record Type: Publication
  • Source Agency: Arctic Institute of North America
  • Files: TRIS
  • Created Date: Mar 28 1972 12:00AM