Roadways on Rock Slopes. On rock slopes when the in clination of the natural surface is not greater than one perpendicular to two base, the road may be constructed partly in excavation and partly in embankment in the usual manner, or by cutting the face of the slope into horizontal steps with vertical faces, and building up the embankment in the form of a solid stone wall in horizontal courses, laid either dry or in mortar. Care is required in proportion ing the steps, as all attempts to lessen the quantity of excavation by increasing the number and diminishing the width of the steps require additional precautions against settlement in the built-up portion of the roadway.
When the rock slope has a greater inclination than 1 :2 the whole of the roadway should be in excavation.
In some localities roads have been constructed along the face of nearly perpendicular cliffs on timber frameworks consisting of horizontal beams, firmly fixed at one end by being let into holes drilled in the rock, the other end being tupported by an inclined strut resting against the rock in a shoulder cut to receive it. There are also examples of similar platforms suspended instead of being supported.
Earth Roads. The term "earth road" is applied to roads where the surface consists of the native soil; this class of road is the most common and cheapest in first cost. At certain seasons of the year earth roads when properly cared for are second to none, but during the spring and wet seasons they are very deficient in the im portant requisite of hardness, and are almost impassable.
For the construction of new earth roads, all the principles pre viously discussed relating to alignment, grades, drainage, width, etc., should be carefully. followed. The crown or transverse contour should be greater than in stone roads. Twelve inches at the center in 25 feet will be sufficient.
Drainage is especially important, because the material of the road is more susceptible to the action of water, and more easily destroyed by it than are the materials used in the construction of the better class of roads. When water is allowed to stand upon the road, the earth is softened, the wagon wheels penetrate it and the horses' feet mix and kneed it until it becomes impassable mud. The action of frost is also apt to be more disastrous upon the more per meable surface of the earth road, having the effect of swelling and heaving the roadway and throwing its surface out of shape. It may in fact be said that the whole problem of the improvement and maintenance of ordinary country roads is one of drainage.
In the preparation of the wheelway all stumps, brush, vegetable matter, rocks and boulders should be removed from the surface and the resulting holes filled in with clean earth. The roadbed having been brought to the required grade and crown should be thoroughly rolled, all inequalities appearing during the rolling should be filled up and re-rolled.
Care of Earth Roads. If the surface of the roadway is prop erly formed and kept smooth, the water will be shed into the side ditches and do comparatively little harm; but if it remains upon the surface, it will be absorbed and convert the road into mud. All ruts and depressions should be filled up as soon as they appear. Repairs should be attended to particularly in the spring. At this
season a judicious use of a road machine and rollers will make a smooth road. In summer when the surface gets roughed up it can be improved by running a harrow over it; if the surface is a little muddy this treatment will hasten the drying.
During the fall the surface should be repaired, with special reference to putting it in shape to withstand the ravages of winter. Saucer-like depressions and ruts should be filled up with clean earth similar to that of the roadbed and tamped into place.
The side ditches should be examined in the fall to see that they are free from dead weeds and grass, and late in winter they should be examined again to see that they are not clogged. The mouths of culverts should be cleaned of rubbish and the outlet of tile drains opened. Attention to the side ditches will prevent overflow, and washing of the roadway, and will also prevent the formation of ponds at the roadside and the consequent saturation of the roadbed.
Holes and ruts should not be filled with stone, bricks, gravel or other material harder than the earth of the roadway as the hard material will not wear uniform with the rest of the road, but produce bumps and ridges, and usually result in making two holes, each larger than the original one. It is bad practice to cut a gutter from a hole to drain it to the side of the road. Filling is the proper course, whether the hole is dry or contains mud.
In the maintenance of clay roads neither sods nor turf should be used to fill holes or ruts; for, though at first deceptively tough, they soon decay and form the softest mud. Neither should the ruts be filled with field stones; they will not wear uniformly with the rest of the road, but will produce hard ridges.
Trees and close hedges should not be allowed within 200 feet of a clay road. It requires all the sun and wind possible to keep its surface in a dry and hard condition.
Sand Roads. The aim in the improvement of sand roads is to have the wheelway as narrow and well defined as possible, so as to have all the vehicles run in the same track. An abundant growth of vegetation should be encouraged on each side of the wheelway, for by this means the shearing of the sand is, in a great measure, avoided. Ditching beyond a slight depth to carry away the rain water is not desirable, for it tends to hasten the drying of the sands, which is to be avoided. Where possible the roads should be over hung with trees, the leaves and twigs of which catching on the wheelway will serve still further to diminish the effect of the wheels in moving the sands about. If clay can be obtained, a coating 6 inches thick will be found a most effective and economical improve ment. A coating of 4 inches of loose straw will, after a few days' travel, grind into the sand and become as . hard and as firm as a dry clay road.
The maintaining of smooth surfaces on all classes of earth roads will be greatly assisted and cheapened by the frequent use of a roller (either steam or horse) and any one of the various forms of road grading and scraping machines. In repairing an earth road the plough should not be used. It breaks up the surface which has been compacted by time and travel.