9 Test 9. Purpose : To determine the stability of 32- 

 ton dolos armor unTts (this unit weight became available at test time 

 from another study under investigation). The results of these tests 

 would then be used, in conjunction with the stability equation, to esti- 

 mate the required weight of dolos required for stability. 



Results: Tests of 32-ton dolosse showed that the maximum no-damage 

 waves for this unit were 36 feet in height for the +7 foot Stillwater 

 level and 30 feet in height for the 0.0-foot Stillwater level. It was 

 estimated that 48-ton (150 pounds per cubic foot) dolos armor imits would 

 be stable for both high tide and low tide design wave conditions. 



10 Test 10. Purpose : On the basis of the series 9 

 test results, a prototype repair section using 48-ton (150 pounds per 

 cubic foot) dolos was indicated for the north jetty head section. Be- 

 cause a modest increase of specific weight would allow a comparatively 

 large decrease in armor-unit weight, for the same armor-unit stability, 

 a repair section using 42-ton (155 pounds per cubic foot) dolos on the 

 shoreward end area of the structures was proposed. The lighter weight 

 units, both using the same forms for molding, would allow a smaller toe 

 distance from the monolith. Thus, the use of a lighter weight unit and 

 a shorter toe distance would decrease the required lifting and reaching 

 capability of the crane. The series 10 tests were conducted to check 

 the stability of this revised design section. 



Results : This test series concluded that 43-ton (160 pounds per cubic 

 foot) dolos armor units would be satisfactory if a minimum toe distance 

 of 215 feet from the radius point of the monolith is used (Fig. 6-32). 



(3) Composite Breakwater Trunk; Nonbreaking Waves (Example of 

 Combined Model and Analytical Design ) . 



(a) Project . Proposed construction of a vertical-wall 

 parapet on an existing rubble breakwater, Indiana Harbor, Indiana. 



(b) Reference . Hudson and Wilson (1953). 



(c) Laboratory . WES. 



(d) Test Period . October 1952 to January 1953. 



(e) Problem . Indiana Harbor is located on the south shore 

 of Lake Michigan about 5 miles from the southeast limits of Chicago, and 

 is exposed to waves from the northerly directions. Previous tests on a 

 l:150-scale model of Indiana Harbor indicated that the crest of the rubble- 

 mound east-west breakwater (Fig. 6-33) should be raised to an elevation of 

 about +15 feet LWD for adequate protection from wave overtopping to allow 

 construction of a proposed inner-harbor pier expansion. A vertical -wall 

 parapet situated on top of the existing east-west breakwater was proposed 

 for this purpose. 



(f) Purpose of Model Study . The combined scale model and 

 analytical investigation was conducted to determine the wave forces on 

 the proposed vertical-wall parapet, and the weight of parapet necessary 

 to ensure its stability against overturning and sliding. 



398 



