196 



EARTHWORK 



The center depth is the difference between the corresponding 

 numbers in the second and third columns. This is a fill if 

 the subgrade is higher than the natural surface; otherwise, 

 it is a cut. 



Slope Stakes. In addition to center stakes, slope stakes are 

 used to mark the points where the side slopes of a cut or a fill 

 intersect the natural surface of the ground. In Fig. 4, c is 

 the center stake and m and m' are the slope stakes. 



The method of locating slope stakes is as follows, all letters 

 referring to Pig. 4: 



Let 6 be the width 'l V of the roadbed; d, the depth ce of the 

 center stake; and s the slope ratio = Ik -f- mk = I'k' -=- m'k'. For 

 the upper stake at m, let * be the distance mq from the slope 

 stake to the center line; y+d, the elevation of m above the 

 subgrade = qc+ce =mk. Similarly for the lower stake at m', 

 let x' be the horizontal distance m'q' from m' to the center line, 

 and let dy' = m'k', the elevation of m' above the subgrade. 



b 

 Then, x=-+sXd + sXy (1) 



