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Spreading the Stone

thickness, road and layers

SPREADING THE STONE. The stone is usually hauled from the crusher to the road in wagons or carts, dumped upon the roadway, and spread by forks or rakes. This practice is objec tionable, since the coarse and fine fragments become separated in the process. producing a layer of unequal density and an irregular surface after rolling. It is sometimes specified that the stone shall be dumped upon a plank platform, from which it is distributed with shovels. This last method of spreading costs 4 to 6 cents per cubic yard—about twice that by dumping and raking (see § 356)—and is appropriate only when the very best results are sought. Wagons are upon the market which automatically dump and distribute the stone in layers of uniform thickness; but owing to their cost and weight they are not in very general use. Some contractors use a road leveler to distribute the broken stone, for which purpose the Shuart grader, Fig. 62, has some marked advantages. The blade can be set at any angle with the line of draft, and is adjustable in height. The guards at the ends of the

blade can be swung entirely out of the way, and then the machine may be used to level or crown the subgrade.

The stone should be applied in uniform layers, the thickness of each depending upon the total thickness of the road. Two methods are in use for gaging the thickness of the layers of stone. 1. On the finished subgrade. wood cubes of a depth equal to the thickness of the layer are set at frequent intervals, and the loose stone is laid even with the tops of these blocks. This method is sometimes described as building by blocks, and is the one em ployed on the state-aid roads of New Jersey. 2. The soil is brought to an established grade, and the finished road is required to be brought to another established grade, -in which case neither the absolute thickness nor the uniformity of the several courses is a matter of much importance. This method is employed on the state-aid roads in Massachusetts.