6 



BULLETIN 463, U. S. DEPARTMENT OF AGRICULTURE. 



is not realized that they can not be accomplished except by means of 

 a careful survey, and that such surveys can be made only by experi- 

 enced men who have been trained especially for such work. Farmers 

 and business men generally are inclined to underestimate the amount 

 of skill required to make a road survey properly and their influence 

 has been responsible in the past for much bungling and for uneco- 

 nomical road work for which they have had to pay in heavy taxes. 



Figure 1 illustrates an error which is made sometimes by inexpe- 

 rienced persons in grading a road without first having surveyed and 

 planned the work. In this figure, which is an actual profile of an ex- 

 isting road, line A shows' the original ground surface, line B shows 

 the grade to which the road was actually constructed, and the dotted 

 line (C) shows a grade line which, if it had been followed, not only 



T/^ - EXAMPLE OF HOW A GRADE LINE 

 pgggg^ SHOULD BE ESTABLISHED. 



;:] "A" shows the original grade of an old road 

 •^"B" shows a wrong. though greatly used method of 

 cutting the top of the hill and filling in at the bottom. 



The result is no improvement except to shorten 

 the grade 



"C'shoivs the proper method of cutting the face of 

 the hill instead of the lop, thereby reducing 

 the steepness of the grade without increasing the 

 amount of material moved 



Fig. 1. 



would have required no additional work, but would have reduced 

 the steep grade materially and thereby improved the road con- 

 siderably. 



In fitting the grade line to the ground surface and balancing cuts 

 and fills it should be borne in mind that earth, after being thoroughly 

 compacted, will occupy less space in an embankment or fill than in its 

 original position. The customary allowances for shrinkage and 

 waste in road work are : 



Per cent. 



For heavy cuts and fills ' 10 to 15 



For average grading 15 to 20 



For light grading 20 to 30 



For very light grading and considerable sod_: '. — 30 to 40 



Solid rock will expand from one-third to one-half of its original 

 volume when taken from a cut or excavation and placed in an em- 

 bankment. But the spaces between the particles of stone should be 

 filled with earth as the stone is being placed in the embankment. If 

 this is done, no allowance should be made for the increase in volume 

 when balancing cuts and fills. 



