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producing sufficient fall in the ditches is considered too expensive, it will then be judicious to test the practicability of the other method. This consists in what we call pit-drainage. Its practicability can always be ascertained by digging a well, or by boring with a pile or post auger. If a stratum of sand or gravel, which will absorb water, is reached at a reasonable depth, say not more than forty feet, this plan may be adopted. Three or four wells, equally distributed as to distance will be ample to drain a mile of road. If the wells are to be stoned with rough stones, they should be excavated six feet in diameter, and the depth continued three feet below the surface of the stratum which is found to absorb water. The rough stone wall may be laid dry, but the stones should extend from the inner face to the bank, the smaller ends forming the inner face, thus forming a complete arch of every layer of stones. The wells may all be on one side of the road, or a portion of them on each side, and they should be covered with a strong lattice of cast iron, with meshes about two inches square.
The gutters should fall each way toward the wells, and the low places in the gutters on the other side of the road should be opposite the wells. At each of these low points a well a foot or two in depth should be excavated and stoned up. A tile or a stone drain with good fall should connect the shallow with the deep well. The greater the fall in these cross drains, the smaller may the conduit be, and the less the liability to clog. A slight circular depression should be made in the bottom of the surface gutters around the wells, in which the sediment in the drainage water may be deposited before it flows into the wells. It sometimes occurs that the water, not being carried off rapidly enough, will rise up to, and even above, the top of the well; but this is rare, and the foregoing mode will generally provide satisfactory drainage under the circumstances described. When practicable, the surface gutters conveying the water to streams or to ravines may be of more simple and of preferable construction. Where the water is to be convered a long distance, say half a milo in one direction, a fall of three inches to one hundred feet will answer. This will require the gutter to be six feet eight inches in depth at the discharge end. The bottom of the gutters must be smooth and graded with accuracy. The angle of the slope of the banks should not exceed thirty-five degrees.
In tenacious clay soils the margin of the surface of the substructure, on which to place a Macadam road-bed, should be at least one foot above the bottom of the gutters. It should be made smooth and solid, and have an underdrain at each margin of the macadamizing from six to twelve inches in depth, and an average of twelve inches in width. These drains may have a fall each way for five to seven rods, to a low point from which a lateral drain should extend under the side road to the gutter into which they are to discharge. The longitudinal underdrains are to be made of broken stones, and are to be filled up to the level of the surface upon which the macadamizing is to rest. The earthbanks on each side of the macadamized portion of the road should be twelve inches in height, and be sufficiently sloped to be self-sustaining until the broken stone has been applied, which will render them perfectly secure. The stone should be so broken that all, or nearly all, the pieces will pass through a two-inch ring. This is the rule adopted in England, where this kind of road has reached the greatest perfection.
We say “nearly all,” for of course there will occasionally be stones which, unless too much time is spent in breaking them, will not come up to the standard. This subject is one of the utinost importance; and, if we are to be governed by the opinion of Macadam himself, we find
him declaring that cubes of one and a quarter inch are better than any larger; and he affirmed before a committee of the House of Commons, that his experience went to prove that the expense of keeping roads in repair was almost in the exact ratio of the sizes of stone used in each instance. Thus, a road constructed of metal broken down to cubes of one and a quarter inch would require to keep in repair but one-half the outlay necessary for one constructed of cubes of two and a half inches; so that the increased cost of construction in using the smaller broken metal will be fully compensated for by the saving in repairs and greater durability. In speaking of the metal as being in the form of cubes, it is not intended to convey the idea that each piece of stone must be a perfect cube, and all of equal size; practical men will of course understand that the term is figurative, and that the metal must of necessity be more or less irregular, and vary in size considerably. The broken stone for a new road should be applied to the depth of twelve inches and twenty feet in width to produce a first-class road. The lateral slope either way from the center of the road should correspond with that of the surface of the foundation; this slope should be about one. quarter of one inch to a foot. There should be an earth side track on either side of the macadamized portion of the road. The earth road, when dry and in good order, is more desirable than the Macadam, and mate. rially saves the wear upon it. The foregoing specification, although referring more particularly to a road nearly level longitudinally, is equally applicable as a direction for macadamizing any road of the width mentioned.
The preparation and application of broken stone in road-making have hitherto been very expensive, thus presenting great discouragement to those desiring to improve roads upon this system, which we have no hesitation in pronouncing the best all things considered, as yet discovered. The cost, however, has of late been greatly reduced by the introduction of the “ Blake Stone-Breaker," a machine of immense strength and efficiency, which has been satisfactorily tested in practical use. Thirty perches (twenty-five cubic feet to a perch) of the hardest trap boulders can be broken into the best road metal in ten hours by this machine. It requires about nine horse power to perform this amount of work in the time given. In a single hour it has been known to break four perches, or one hundred cubic feet, of stone of the foregoing character. With this machine the cost of breaking is reduced to thirty cents per perch, using coal at $5 50 per ton, and labor at $1 50 per diem, and an engineer at $2 50 per diem, who assists the two laborers employed in feeding the machine. The average day's work for a good hand in the spring, summer, or autumn is less than one perch, and in winter still less. The average price of such labor is about $1 50 per day at present, so that the reduction of expense by the use of the machine is not less than eighty per cent.
The stone-breaker referred to has elevators connected with it, which carry the stones to a considerable height above the machine, where they are deposited upon a sieve, through which the fine sand produced in breaking the stone passes, and is deposited by means of a chute in a tight compartment on the ground; while the stones running over the sieve are deposited in a kind of hopper, from which they are loaded upon wagons or carts by simply opening a slide or trap. In this manner the cost of loading is reduced to a nominal figure, being done almost instantaneously; while, if done by hand by shoveling from the heap, the cost of loading would be nearly half as much as breaking. · After what has been said with regard to the sand being carried down through a chute into a tight compartment, we will explain why the trouble is taken to separate the sand from the broken stones at all, or care taken to deposit it in a tight compartment. It was found that this sand, produced by the trituration of stones of this quality in the process of breaking, is the very best material yet discovered for manufacturing 66 concrete stone” under the Ransom patent of England, which is rapidly coming into use in this country. About one hundred pounds of sand are made for each perch of stones broken, and all yet made by the machine in question has found ready sale to the “Ransom Concrete Stone Company of Maryland," at one cent per pound. It will be seen that in the neighborhood of cities, where the concrete stone is being manufactured to any considerable extent, a road may be macadamized at a very low cost, if indeed it is not found that the stones can be broken and applied at a cost which shall be less than the proceeds of the sale of sand produced from the amount of broken stone required, thus preparing the road metal free of cost, and leaving a profit to the constructors besides.
In the application of the broken stones to form a road-bed, although the process is simple, it is important that the surface of the earth substructure be kept free from ruts and tracks, as any depressions will fill with water, and soften the foundation at these points, thus causing the road to settle unevenly. Depressions in the stoned surface cannot be well repaired without “picking up” the metal to the depth of several inches. The material used in repair should be somewhat smaller or finer than that of which the road is forined. The portiou repaired is to be thoroughly rammed with a 6 paver's rammer," and, when finished, should be slightly above the surface around it, which remains undisturbed. When the metal has been properly graded on a new road, the surface should have a slight dressing of clay, and a heavy roller should be passed over it until the inetal comes to its bearing, before vehicles are allowed to pass over it. A road-bed twenty feet in width and twelve inches in thickness will require 4,224 perches of broken stone to the mile. The surface gradle of the earth side tracks should correspond with, and be a continuation of, the grade of tho macadamized portion. The side tracks should not be more than nine feet in width, as unnecessary width increases the difficulty of surface drainage.
Many professional road makers will take exception to the clay surface dressing, but it has been thoroughly tested in practice, and alwars with success. The effect is to bring the metal to a bearing at once, and to prevent the action of the wheels from destroying the angularity of the surface metal, a very important quality, as it is almost impossible, after the surface stones have become rounded, to get them to bind one with another, and form a first-class road surface. The quantity of clay applied should be sufficient only to fill the interstices between the stones. on the immediate surface, when the metal has come to its bearing. Another advantage of such an application is to render the superstruture of macadamizing water-proof, almost from the first, the importanca of which, in assisting to maintain a dry foundation, is almost seit evident.
TIE GRAVEL AND OTHER ROAD-BEDS.
Where the natural soil of a road consists of gravel of proper texture. in its natural state, the process of producing a very desirable road, for all except very heavy trafiic, is simple and inexpensive. It only requires to have the surface of the road-bed raised by repeated plowings, the furrows all being turned toward the center of the road. In case the natural surface has a slope to one side, the execution can still be mainly and most economically performed by the use of the plow, by turning the furrows in one direction. The plow should be what is called the “ double right and left-hand plow," which may be used with great advantage. When the desired grade of the surface of the road and gutters shall have been produced, as nearly as practicable, by the use of the plow, it should then receive repeated harrowings. The remainder of the work may be most economically and efficiently performed by means of the grading machine, except the removal of considerable hills, or the filling of corresponding depressions, which, if the distance is short, may be best per: formed by the use of the common scraper; but, if it exceeds five or six rods, wheelbarrows, carts, or dump-wagons will be necessary. No hand grading is necessary, as the grader, propelled by a pair of active horses, will perform more of this character of work than fifty men, and at the same time (lo it better.
The width of such gravel road will, of course, be controlled by circumstances, the amount of travel and the character of it being the most important considerations. It may be remarked, however-and it is equally applicable to all roads, of whatever material—that they should not be made wider than is really necessary, otherwise the cost is greatly increased, as well as the difficulty of surface drainage, which, as was re marked in connection with Macadam road, is of great importance. A road constructed of natural gravel, and having a gravel sub-soil, will require to be raised less in the center, and the side gutters may be made more shallow than would be admissible with any other material.
Rotten rock.- This material is frequently found, in a natural state, quite well adapted to forming a road that will serve all the purposes for which earth and gravel roads are adapted. It rarely has a proper degree of tenacity, however, to enable it to bind, or retain desirable compactness.
Where this material lacks tenacity the defect is easily corrected by adding a due proportion of clay, but the proper proportion of each can be ascertained only by experiment. When prepared as they should be, a good road for ordinary country travel can be made from these substances.
Loam.-By the term loam tre mean clay with an admixture of fine sand, and generally a liberal proportion of vegetable matter.
When the proportions of clay and sand are such that the soil will not bake, por incrust when dry, nor become very adhesive when wet, it may properly be called loam. When the soil of a road-bed consists of loam, or the best soil obtainable, the directions for the use of clay are applicable, with the exception that loam does not require the extreme degree of surface slope recoinmended for clay.
The natural soil of the bed inay be either clay or sand. The application of the other by hauling it on to the bed and incorporating it by means of the plow and harrow, will enable the engineer to produce from these two materials (each illy adapted alone) an artificial soil, which will answer the purposes of a road-be quite satisfactorily: Gravel, consisting of water-worn pebbles, without an admixture of clay by which to cement them, is a poor road material. as it rolls trom under the feet of the ani. mals and from beneath the wheels, making the labor of teams on such a road very severe. A proper amount of clay added to, and well mixed with gravel, will greatly improve it as road paterial. The characteristics of all these materials are so various in difierent localities that the proportions need to be modified according to circumstances; and the proper proportions in each respective case will be most readily and satis. factorily determined by experimenting with a number of samples, say a cart load of each, in different proportions, which should be carefully Poted, all being placed contiguously on the road-bed where they will be equally exposed to wet and to use. A few months' experience, under such test of the various mixtures, will give the road maker data which theory cannot furnish.
In some sections of great area no other material than clay can be, obtained; hence it must be used as road material in its natural state. The general principles involved in the construction of gravel, loam, and other roads, and described under those heads, are to be observed in constructing a road exclusively of clay ; the gutters, how. ever, should be made as deep as is practicable, and the road-bed as narrow as the travel will admit, and be as highly crowned as is admissible, thus guarding against absorption of water from the gutters, and effectually shedding the rain-fall from the bed. There is no material in the catalogue treated that forms so perfect and delightful a road for pleasure. driving as clay, when in a certain condition; but it is so difficult to be maintained in the desired state that it is judicious to incorporate sand or gravel with it, wherever practicable.
There are districts of country many miles in extent, where nothing but drifting sand can be obtained for making roads. Where the depth of the sand is great before reaching a tenacious subsoil, a road-bed of sand will be more compact and better, if made lower than the surface of the land on either margin, so that water may flow on to, instead of being drained off from, the road. Like clay, pure sand is not a desirable ‘oad material, and quicksands, not unfrequently found in extensive sandy regions, are dangerous. Where drainage of quicksands is impracti. cable, two thicknesses of planking laid over the place to be crossed, the lower planks running in the direction of the road, and the upper ones across it, have been found to answer very well as a sort of a floatingroad. A contractor on the Knox and Lincoln railroad in Maine has recently encountered a quicksand into which he has sunk pile upon pile to the depth of one hundred and forty feet, and no indications of a hard substratum are yet apparent.
Plank roads have been so universally unsatisfactory that valuable space need not be occupied with directions for their construction.
I. A. Lewis, of Howard County, Missouri, says that a plank road was constructed in that county twenty-six miles in length, costing $100,000; butit haslong since been abandoned. Numerous instances may be cited of their failure from all parts of the country, but not one in which they have been a success. A plank road is a good road when in proper condition, and may be a necessary kind in some districts of the country; hence it may be well to state that it is claimed that, by steaming the plank, and charging them with creosote, costing about eight dollars per thou. sand feet, board measure, their durability will be doubled.
THE LONGITUDINAL GRADE FOR A ROAD.
There is perhaps no branch of the subject under consideration which demands more attention by the engineer than that of the reduction of road grades to the minimum under all practicable circumstances. We can better afford to increase the length of a road considerably than to