Tests of Low-Density Marine Limestone for Use in Breakwaters.
COASTAL ENGINEERING RESEARCH CENTER FORT BELVOIR VA
Pagination or Media Count:
A porous, low-density limestone cemented shell stone available from a quarry in New Bern, North Carolina, was suggested for use as a cover layer in coastal structures. The stability of the New Bern stone as a rubble-mound armor unit was tested in the large wave tank at CERC. Fourteen tests were conducted with 3.75-, 5.60-, and 7.87-second wave periods and wave heights ranging from 2.5 to 4.2 feet. The armor stones were also numbered and weighed at the beginning and end of testing to evaluate the durability of the stone. Results of the stability test showed armor unit stability coefficients of 2.8, 3.5, and 7.8 for the 3.75-, 5.60-, and 7.87-second wave periods, respectively. The stones still identifiable at the end of testing lost an average of 5.5 percent of their original weight. As a result of the stone weight losses experienced in the laboratory tests, 13 stones were placed on or near a jetty in Fort Macon, North Carolina, by the U.S. Army Engineer District, Wilmington. The stones were periodically removed, weighted, and replaced for about 18 months. Results showed that the stones considered to be of the best quality had lost from 5 to 20 percent of their original weight after 6 months. Additional heavy weight losses 45 to 65 percent to those stones still located at the end of testing indicated that excessive weight loss would continue. The use of New Bern stone as a cover or underlayers of rubble-mound coastal structures is not recommended. Author
- Civil Engineering