Table 6-6. Model-prototype quarry stone relationship for Texas City, Texas. 



Type of quarrystone 



Model 



Prototype 



Wa 



^50 



7 



W 



W50 



7 





(lb) 



(lb) 



(lb/ft3) 



(ton) 



(lb) 



(lb/ft3) 



Armor units 



0.60 





141 



8.0 





162 



Armor units 



0.46 





139 



6.0 





162 



Armor units 



0.27 





142 



3.3 





162 



Crushed stone 





1.45 X 10-5 



165 





0.75 



162 



Blanket stone 





6.17 X 10-"* 



165 





32 



162 



Riprap 





1.05 X 10-3 



176 





70 



162 



Core stone 





6.77 X 10-3 



176 





450 



162 



A-rock underlayer 





9.40 X 10-3 



176 





625 



162 



Toe stone 



1 





4.82 X 10-2 



165 





2,500 



162 



The gradations o£ these materials were based on the different sizes 

 of stones obtained economically from quarries near Texas City. The sizes 

 of the various imderlayer stones were also selected to prevent the leach- 

 ing of smaller material through the voids of the upper layers. 



(h) Test Procedures . Model sections, simulating each type 

 of seawall proposed for Texas City, were tested with a 90° angle of wave 

 incidence. Concrete bottoms in the flume reproduced the natural ground- 

 line profiles shown in Figure 6-43. Photos were taken of most wave con- 

 ditions and seawall sections tested. Visual observations were made to 

 determine the behavior of the test structures under wave attack and to 

 select the no-damage wave heights; i.e., the largest waves that would not 

 damage the seawall sections. The volume of overtopping water was measured 

 (in all tests where overtopping occurred) by a calibrated tank located im- 

 mediately behind the test section. The amount of overtopping water was 

 measured in cubic feet per second per foot of wave crest; i.e., the volume 

 of overtopping water per foot of crest divided by the wave period. Wave 

 forces were measured at various increments on the vertical face of the 

 seawalls tested with a vertical wall. These measurements were made using 

 a 1-foot -wide part of the 5-foot-wide test section. The bottom of a 

 weighted block was placed on a plane horizontal surface with its vertical 

 face in the plane of the vertical-wall part of the test section. A plas- 

 tic sheet prevented uplift pressures from acting on the bottom of the 

 block. Weights were removed from the block in small decrements until 

 the wave forces caused a slight movement of the block. The force re- 

 quired to move the block was then measured by a spring balance with an 

 accuracy of ±0.1 pound. The seawall sections with parts composed of 

 underlayers protected by quarrystone armor units were constructed by 

 hand-placing the armor units in a manner corresponding to placement by 

 crane in the prototype. The water levels used in stability models of 

 coastal structures are selected so that the effects of water depth on 

 the breaking characteristics of the waves that attack the prototype 

 structure are reproduced as accurately as possible. Based on a study 

 of storm-surge frequency in the Texas City area, water depths for the 

 different test sections were selected using a storm-surge elevation 



412 



