■731 X .142 3 , 0.67 



.731 X .93h 2 



s 1^000 pounds 



I4760 The raaximum moment of horizontal pressure would bes 

 Mvi = 1000 X 5/3 = 1,670 foot-pounds 



If the -vertical component of earth pressure is neglected, which maybe 

 done unless it has a large effect on stability, the vertical load of the 

 wall passes through the centerline of the base, and the above moment 

 becomes the moment around the centerline of the base, 



I4.770 Assuming a block with a 7-foot base, a 3-foot top width, and 

 S feet high, the weight per linear foot in air would be 



5 ^7 * 3) X 150 = 3,700 pounds 



With this block, the stress in the outer fibre would be 



f - P + ^ . 37^0 ^ 6(1670) ^ 536 + 200 (161) 



- A - bd2 1 X 7 - (7)2 



= 536 + 205 s 7UI pounds per square foot, 



s 536 - 205 s 331 pounds per square foot. 



These pressures are satisfactory both for concrete and for the founda- 

 tions . 



14.780 To check the possibility of sliding; 



P . 1000 _ 27 



W ^ 37^ " ° 

 This is less than the coefficient of friction for masonry on sand and is 

 considered satisfactory, 



1479" Wave Pressures » - With a 5-foot high block, the maximum 

 wave conditions would occur when the water is about 3,7 feet deep at the 

 groin, at which time a wave 3o7/lo3 = 2,8 feet high would be possible- 

 Using a 10-second wave and a beach slope of 1 on 20 



^ s 3^7 . ^0073 and ^ s »03i4 

 L„ 512 L 



o°o L = d/c03l4 = 3,7/0,0314 = 109 feet 



227 



