214 STRENGTH OF MATERIALS 



From the above, it follows that for an economical design the cross 

 section of a wall should be trapezoidal, the thickness of the base 

 being determined by the consideration of stability against overturn- 

 ing, and the thickness of the top by the maximum action of frost. 



The inclination of either face of a wall to the horizontal is usually 

 expressed by giving the ratio of the horizontal projection of this face 

 to its vertical projection. This ratio is called the batter, and is given 

 in inches of horizontal projection per foot of height. For example, if 

 a wall makes an angle of 80^ with the horizontal," it is said to be 

 "battered 2 to 1," since the ratio of its horizontal projection to its 

 vertical projection is equal to cot a, and in the present case 



cot a = cot 80^ = .1673 = YV, approximately. 



Problem 170. Design a concrete retaining wall to support a bank of loose earth 

 26 ft. high, the back of the wall to be inclined backward at a batter of 1J to 1. 



