Method of Constructing Test Sections 



All experimental breakwater sections were constructed to reproduce as 

 closely as possible results of the usual methods of constructing full-scale 

 breakwaters. The core material was dampened as it was dumped by 

 bucket or shovel into the flume and was compacted with hand trowels to 

 simulate natural consolidation resulting from wave action during construc- 

 tion of the prototype structure. Once the core material was in place, it 

 was sprayed with a low-velocity water hose to ensure adequate compac- 

 tion of the material. The underlayer stone then was added by shovel and 

 smoothed to grade by hand or with trowels. Armor units used in the cover 

 layers were placed in a random manner corresponding to work performed 

 by a general coastal contractor; i.e., they were individually placed but 

 were laid down without special orientation or fitting. After each test the 

 armor units were removed from the breakwater, all of the underlayer 

 stones were replaced to the grade of the original test section, and the ar- 

 mor was replaced. 



Test Equipment and l\/laterials 



Equipment used 



Tests were conducted in a concrete wave flume, 1 1 ft wide, 6 ft deep, 

 and 245 ft long.' The cross section of the tank in the vicinity of the struc- 

 tures was partitioned into two 3-ft-wide channels and two 2.5-ft-wide 

 channels (Figure 1). Identical test sections were constructed in the 3-ft 

 channels while wave absorption was achieved in the 2.5-ft channels, 

 which were left empty. The flume is equipped with an electro-hydraulic, 

 horizontal-displacement wave generator capable of producing monochro- 

 matic and irregular waves of various periods and heights. Changes in 

 water surface elevation as a function of time (wave heights) were meas- 

 ured by electrical capacitance-type gauges at selected locations. The 

 wave machine was controlled by and data were collected with an on-line 

 Dec Micro Vax I computer. Data then were transferred to a Vax 3600 for 

 analysis. 



Materials used 



Rough hand-shaped granitic stone (W^) with an average length of about 

 two times its width, average weight of 0.38 lb, and a specific weight of 

 167 pcf was used. Sieve-sized angular-shaped limestone (unit weight = 

 165 pcf) was used for the underlayers and core. 



' A table of factors for converting non-SI units of measurement to SI units is presented on page v. 



Chapter 2 Tests and Results 



