UK 1H WAY CONSTRUCTION 



2T, 



figures in column A represent the elevation of the ground at every 

 100 feet, or where a stake has been driven, above datum. The 

 figures in column H are the elevations of the grade alxwe datum. 

 The figures in column C indicate the depth of cutting or height of 

 fill; they are obtained by taking the difference between the level of 

 the road and the level of the surface of the ground. The straight line 



-CLEARING -ACRES 



*TH & GRAVEL OPTING-C.YDS 



5 



- - fWCK CUTTING - - CYDii 

 (0 



r 



EARTH CXC.---C.VDS. 



? 5 



2 J n M 



Fig. 7. 



at the top represents the grade of the road; the upper surface of the 

 road when finished would be somewhat higher than this, while the 

 given line represents what is termed the sub-grade or formation level. 

 All the dimensions refer to the formation level, to which the surface 

 of the ground is to be formed to receive the road covering. 



At all changes in the rate of inclination of the grade line a heavier 

 vertical line should be drawn. 



Gradient. The grade of a line is its longitudinal slope, and 

 is designated by the proportion between its length and the difference 

 of height of its two extremes. The ratio of these two qualities gives 

 it its name; if the road ascends or falls one foot in every twenty feet 

 of its length, it is said to have a grade of 1 : 20 or a 5 per cent grade. 

 Grades are of two kinds, maximum and minimum. The maximum 

 is the steepest which is to be permitted and which on no account is to be 

 exceeded. The minimum is the least allowable for good drainage. 

 (For method of designating grades see Table 9). 



Determination of Gradients. The maximum grade is fixed 

 by two considerations, one relating to the power expended in ascend- 

 ing, the other to the acceleration in descending the incline. 



There is a certain inclination, depending upon the degree of 

 perfection given to the surface of the road, which cannot be exceeded 



