48 HIGHWAY CONSTRUCTION 



masses, or boulders measuring more than three cubic feet, and which 

 can only be removed by blasting. 



Prosecution of Earthwork, No general rule can be laid 

 down for the exact method of carrying on an excavation and dis- 

 posing of the excavated material. The operation in each case can 

 only be determined by the requirements of the contract, character 

 of the material, magnitude of the work, length of haul, etc. 



Formation of Embankments. Where embankments are to be 

 formed of less than two feet in height, all stumps, weeds, etc. should 

 be removed from the space to be occupied by the embankment. 

 For embankments exceeding two feet in height stumps need only 

 be close cut. Weeds and brush, however, ought to be removed and 

 if the surface is covered with grass sod, it is advisable to plow a fur- 

 row at the toe of the slope. Where a cutting passes into a fill all 

 the vegetable matter should be removed from the surface before 

 placing the fill. The site of the bank should be carefully examined 

 and all deposits of soft, compressible matter removed. When a bank 

 is to be made over a swamp or marsh, the site should be thoroughly 

 drained, and if possible the fill should be started on hard bottom. 



Perfect stability is the object aimed at, and all precautions neces- 

 sary to this end should be taken. Embankments should be built in 

 successive layers, banks two feet and under in layers from six 

 inches to one foot, heavier banks in layers 2 and 3 feet thick. The 

 horses and vehicles conveying the materials should be required to 

 pass over the bank for the purpose of consolidating it, and care 

 should be taken to have the layers dip towards the center. Embank- 

 ments first built up in the center, and afterwards widened by dump- 

 ing the earth over the sides, should not be allowed. 



Embankments on Hillsides. When the axis of the road 

 is laid out on the side slope of a hill, and the road is formed partly 

 by excavating and partly by embanking, the usual and most simple 

 method is to extend out the embankment gradually along the whole 

 line of the excavation. This method is insecure; the excavated 

 material if simply deposited on the natural slope is liable to slip, 

 and no pains should be spared to give it a secure hold, particularly 

 at the toe of the slope. The natural surface of the slope should be 

 cut into steps as shown in Figs. 23 and 24. The dotted line AB 



