EARTHWORK 



195 



increases or decreases in 100 ft. It is usually marked on the 

 grade line in the manner shown in Fig. 3. The depth of 

 center stake is the difference between the elevation of the 

 natural surface at any stake and the elevation of the sub- 

 grade. The elevation of the natural surface is found in the 

 level notes, while the elevations of the subgrade are computed 

 from the gradients and also entered in the level notes. The 

 difference for each stake is then figured and entered in a cplumn 

 headed Depth of Center Stake, being preceded by the letter 

 C or F to indicate cut or fill. 



EXAMPLE. Stakes are set at the stations indicated in the 

 first column of the accompanying field notes. The gradient 

 is +.76% from Sta. 90 to Sta. 93, and -.50% beyond Sta. 93. 

 The elevation of the established grade at Sta. 90 is 100.00 ft.; 

 the elevation of the natural surface at each stake is given 

 in the third column. Find the center depth at each stake. 

 (See Fig. 3.) 



SOLUTION. The elevations of the subgrade at the station 

 stakes are determined as follows: 



Station Elevation 



91 100.00 + 1.00 X .76 = 100.8 

 91+32 100.00 + 1.32X .76=101.0 



92 100.00+2.00X .76=101.5 

 92 + 51 100.00+2. 51X .76 = 101.9 



93 100.00+3.00X .76=102.3 



94 102.28 + 1.00X-. 50 = 101.8 



