percentage of damage incurred by a test section during the early 1950 's. This 

 method has proven satisfactory and was used as a means for analyzing and com- 

 paring the stability tests delineated herein. 



10. The WES damage-measurement technique requires that the cross- 

 sectional area occupied by armor units be determined for each stability test 

 section. Armor unit area is computed from elevations (soundings) taken at 

 closely spaced grid-point locations before the armor is placed on the under- 

 layer, after the armor has been placed but before the section has been sub- 

 jected to wave attack, and finally after wave attack. Elevations are obtained 

 with a sounding rod equipped with a circular spirit level for plumbing, a 

 scale graduated in thousandths of a foot, and a ball-and-socket foot for 

 adjustment to the irregular surface of the breakwater slope. The diameter in 

 inches of the circular foot of the sounding rod was related to the size of the 

 material being sounded by the following equation: 



where 



C = coefficient 



W = weight of an armor unit, lb 



Y = specific weight of armor unit, pcf 

 C = 6.8 for tribars and stone and 13.7 for dolosse. A series of sounding 

 tests in which both the weight of the armor and the diameter of the sounding 

 foot were varied indicated that the above relation would give a measured 

 thickness which visually appeared to represent an acceptable two-layer 

 thickness. 



11. Sounding data for each test section were obtained as follows: 

 after the underlayer was in place, soundings were taken on the slopes of the 

 structure along rows beginning at and parallel to the longitudinal center line 

 of the structure and extending in 0.25-ft* horizontal increments until the 

 edge of the armor was reached. On each parallel row, sounding points, spaced 



* A table of factors for converting non-SI units of measurement to SI metric 

 units is presented on page 3. 



