Selection of Test Conditions 



All tests were conducted with a Texel, Marsen, Arsloe (TMA) spec- 

 trum. For tests described herein, the wave flume was calibrated for peri- 

 ods of 1.5, 2.25, 3.0, and 4.0 sec in water depths of 0.80 and 1.60 ft, thus 

 assuring a range of relative depths (d/L's) that is consistent with the major- 

 ity of conditions to which prototype structures are exposed. Goda and 

 Suzuki's (1976) method was used to resolve the incident and reflected 

 spectra. 



All tests were conducted on stone sections of the type shown in Figures 

 2 and 3 and Photos 1-4. Both sea-side and beachside slopes were held 

 constant at IV on I.5H. 



Design wave heights for the no-damage criterion were determined by 

 subjecting the test sections to irregular waves successively larger in height 

 in 0.01- to 0.02-ft increments until the maximum heights for which the ar- 

 mor was stable were reached. Each was allowed to attack the breakwater 

 for a time equivalent to at least 1,000 peak wave periods, then the test sec- 

 tions were rebuilt prior to attack by the next added increment wave. This 

 1,000-wave duration allowed sufficient time for a statistically stable ir- 

 regular wave condition to develop in the wave tank and also was sufficient 

 for the test sections to stabilize. 



Sliallow-Water Test Results (d = 0.80 ft) 



Shallow- water stability test results are summarized in Table 1. Pre- 

 sented therein are experimentally determined design wave heights and cor- 

 responding stability coefficients as functions of wave period, spectral 

 width parameter (gamma), GI, and relative depth (d/L). Photos 5-8 show 

 typical after-testing views of the structures at the 0.80-ft depth. As evi- 

 denced in these photos, the design wave conditions allowed occasional dis- 

 placement of a few random armor units, but the damage never exceeded 

 the acceptable design criteria of more than 2 percent of the total number 

 of armor units in the primary cover layer. Results of a few tests did ex- 

 ceed the acceptable design criteria, however, the test conditions were 

 never allowed to totally destroy the test section. 



Figure 4 presents K^, the Hudson stability coefficient, as a function of 

 gamma for all wave periods investigated and Figures 5-8 present results 

 for constant wave period. These data show stability to be influenced by 

 wave period with the lower stabilities being observed at the longer wave 

 periods. Also, the lower stabilities generally occur at the higher values of 

 gamma. Figure 9 depicts stability as a function of grouping intensity, i.e., 

 number of wave groups per hour of test waves. As would be expected, the 

 lower stabilities are generally associated with the higher grouping 

 intensities. 



Chapter 2 Tests and Results 



