Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/267

 Marcu 29, 1872. THE BUILDING NEWS. 249 THE BUILDING NEWS. er LONDON, FRIDAY, MARCH 29, 1872. NOTES ON EARTHWORK.—I. OST of the readers of the Bur~pine News, we take it, have something to do with earthwork, and we intend to offer a few remarks on that subject. The ground we work in is naturally various in kind, and accordingly requires various appliances and means for its remoyal and disposal. Top soil, common earth, clay, marl, gravel, sand, shale, sandstone, limestone, and conglomerate rocks, all have to be dealt with under the head of earthwork. As in treating of carpentry we began by considering the natural properties and charac- teristics of timber, and in treating of brick- work by first considering the nature of the clays, limes and cements of which it is com- posed, so in these notes, before we proceed to consider the practical means of removing and disposing of earth, it may be well to consider first the characteristics of the various kinds. Top soil is always more or less composed of vegetable matter, but chiefly of the de- tritus of the underlying rock, and is generally of similar colour, being reddish on the new red sandstone, whitish on chalk, and yellowish, brownish, or blackish on the clays and shales. Over thick beds of gravel the rule does not hold good. The vegetable matter contained in top soil decays, and for this reason it is an unfit material for embank- ments ; it attracts to itself water to a great extent, and if placed in banks it is very liable to cause slips, not only of itself, but of the surrounding materials. A cubie yard of top soil weighs about a ton; when thrown loosely into a heap it occupies a space of 1} cubic yards, and it assumes a natural slope—that is, the angle which its face makes with the horizon—of 28 degrees; but whenit is deposited in layers and well rammed it can be made to stand at an angle of 45 degrees, or ata slope of 1to1. Under favourable circumstances it is worth 23d. per cubie yard to dig and fill into barrows, and 3d. into carts. The favourable circumstances are when it is of the full length of one spit or ‘‘ draw,” that is, 8 or 9 inches. When it is of less depth it is worth more per cubic yard ; also, when itis very dry or very wet. A common price for stripping soil from 7 to 9 inches deep, and wheeling it to a distance not exceeding 20 yards, is 3d. per square yard. In its natural position it is very porous, being full of worm and insect holes, and of spaces left open by decayed vegetable matter. When excavated and tipped in a heap it can, for this reason, be consolidated, by ramming, into a less space than it occupied in situ. Common earth is that mixture of sand, clay, and gravel commonly met with near the surface, which cannot be classed distinctly as sand, clay, or gravel, and which generally requires loosening with the pick before it can be removed. In most cases one pickman or getter will get as much as two men can fill into barrows and another ‘spurn out” or wheel away to the first stage or horsing. Lying directly under the top soil it is exposed also to atmospheric influences, and is full of cracks and small fissures caused by the descent of rain water, expansion by frost, and contraction in hot weather. For this reason it can be consolidated in bank, by sufficient ramming, to its original bulk, but when tipped loosely into a heap it occupies more space, and assumes a natural slope of about 30 degrees. Its weight in the solid is about 24cewt. per cubic yard. Clay is usually not so hard but that it can be dug out with tools. A grafting tool is the best for this purpose, being long and narrow, and hollow on the face, differing in this respect from a spade, which is nearly straight across the face, and not so long in propor- tion to its width. A grafting tool should be half an inch wider at the bottom than at the top, to free itself in working. A cubic yard of clay weighs about 27ewt. in the solid, and is more uniformly heavy in its natural state than other earths. If clay be purposely dried by exposure to the sun for a consider- able time, and then placed within reach of water, it will absorb one-third of its weight of water; but if we take clay ina naturally dry state, and place it so that it may absorb water, it will absorb from one-tenth to one- seventh of its weight, and haying done so, it does not readily part with it, and thus is preserved in a nearly uniform degree of moisture. A cubic yard of clay loosely tipped into a heap occupies a space of about 1% cubic yard, but it can be consolidated, by ramming, into its original bulk. Its natural slope is 45 degrees, or 1 to 1, when moderately dry, but when saturated with water its slope is very uncertain; about 15 degrees, or 4 to 1, is unusually assumed to be the natural slope of wet clay. When moderately dry it is so com- pact and tenacious that it will stand with a vertical face of 12ft. in height, or more, but under such circumstances it often gives away suddenly without apparent cause, although, when the face from which it has slipped away is examined, soapy veins areseen, from which, while it remained in a quiet state, its weight was insufficient to detach it, but on the pass- ing of a set of waggons, or other cause of vibration, these high vertical faces are not unfrequently thrown down. Clay, when not so dry but that it can be easily excavated with the grafting tool, is worth 3d. per cubic yard to dig and fill into barrows, 34d. into carts or earth-waggons, and 4d. to dig and cast up toa height of 6ft., or to a horizontal distance of 12ft. In esti- mating the value of earthwork it is often based on the quantity that one man can re- move ina day, but the quantities that men can remoye vary so much that it is better to state the value at per cubic yard. Marl, although chemically different from clay, may, as a class of earth, be considered as a hard clay. It contains more lime than clay does, and, in general, cannot be removed by digging, but must be got up with picks and filled with shovels. Clay does, indeed, in some situations—namely, those more than usually exposed to the evaporation or absorp- tion of the water it contains—oftenrequire the use of the pick as well as the marls; and it is difficult to draw a line of distinction between the two in respect of their practical excava- tion, but it seems advisable for the sake of proceeding gradually with the subject to give the name “clay” to that substance which can be dug out without the use of picks, and ‘‘marl” to that which cannot be got without their use. A cubic yard of marl weighs in the solid about 26cwt., and when tipped loosely into an embankment occupies a space of 13 eubie yard, and assumes a natural slope of 59 degrees. In railway em- bankments it is not practicable, or at least not usual, to consolidate the earth by ram- ming in thin layers, the usual way being to tip it from waggons to the full height of the bank at once, but some degree of consolida- tion may be had by keeping the outside tips in adyance of those occupying the central portion of the bank. The outer tip on each side, being kept in advance, forms a sort of footing for the inner portion to rest against, and a bank formed in this manner is in a better state of consolidation than one in whieh all the tips are worked in a line. In small affairs, such—as the foundations for the walls of buildings—the same workmen may use both pick and shovel, but in larger works the principle of the division of labour is adopted for cheapness. On the principle of the division of labour in general in the arts and in manufactures, we might here say a good deal if we were to allow our predi- lections to overrule our purpose in recording a few notes for use, and which must be made, to be of general use, with a full recognition of the general practice, and that certainly is to carry the division of labour to a too great extent. However, so far as earthwork and nayvies are concerned, there seems less reason to object to the principle than in any other art; art, we say advisedly, for itis an art to get and fill earth, and remove it in a proper manner. See a number of nayvies at work—say getters, and observe how one man strikes his pick into the ground with deliberation and precision, thought preceding physical action, an action which is much more effectual in loosening the earth than the blundering hap- hazard blows of another man, who may seem to be working harder but who is in reality doing less useful work. The one will lay down his pick at the end of his day’s work without having distressed himself, while the other poor fellow will have worked so much sweat out of him that the first thing to be done is to get some beer to make up for it, and if he should be so unfortunate as to get hold of some that is not genuine, he will probably be drunk before he gets home. The same thing holds good in filling as well as in getting earth. ‘The artistic workman will fill a greater quantity of earth in his day’s work than the man who blunders at it as if, instead of having barrows or waggons to fill all day, he weresuddenly called upon to heave something out of the way. Idleness, on the other hand, is as far removed from a proper form of working as rashness. The nayvy who is an artist is not so much artful as thoughtful. Earthwork is measured by the cubic yard, containing 27 cubic feet, in England and America ; and by the cubic métre, containing 35°31658 cubic feet, on the European conti- nent. In civil engineering works—that is to say excluding military engineering works, such as fortifications, which have their own pecu- liar terms for the various parts—earthwork consists of excavations and embankments. The generic term excavation is applied to various kinds of work under technical names, as a railway cutting, when the work is per- formed from the surface downwards; or a tunnel, when driven horizontally through the ground below the surface; a sewer trench, and a water-pipe trench ; a well or shaft sink- ing, When large enough for men to pass down, or a boring when performed with tools from the surface. A railway cutting is subdivided into the barrow roads, consisting of planks, trestles, box horses, packings, and stages, the distance from stage to stage being a run. Barrows are first used in commencing a cutting, to prepare for laying in the waggon road at or near the formation level of the intended rail- way, and then a gullet is excavated, being a narrow cutting with vertical sides, which is pushed forward up the centre of the main cutting at or near the bottom of it, for the purpose of procuring standing room for sets of waggons, which are filled, the foremost of them from the “face,” and the middle and hinder ones with barrows from higher parts of the cutting. For the purpose of reaching other faces, so as to give room for a greater number of men to work, inclined waggon roads are laid with temporary rails on one or both sides of the gullet, so that the cutting is divided vertically into a series of lifts, from the faces of which the earth is excavated and filled into the waggons, both directly from the faces and from barrow roads. Another way of removing earth is by horse runs, whereby a chain, reeved through a snatch-block at the bottom of a post, set at the top of the slope of acutting, and over a pulley at the top of it, is drawn horizontally by a horse, the other end of the chain being attached by slings to the hales of the barrow. The dobbin cart is useful in removing earth
 * to short distances on the level; it holds about