John Newman

“ With regard to the inclination and the form of a slope, and the prevention of slips in earthwork, in any slip the surface must be affected; therefore, to determine the slope of permanent stability of any earth, whether in a cutting or an embankment, is of great importance. An unnecessarily flat slope is not only a monetary waste but may be a cause of instability, for it exposes a larger surface to deterioration by the weather. ”

“ A considerable margin of stability should in all cases be allowed. Although it may not be absolutely necessary to experiment when the nature of the ground is well known, wherever stability is of great importance, the cost of a practical experiment being so small, there is no sufficient reason why an actual test of the sustaining power of the soil should not be made in the majority of instances, for there are many earths whose friction and cohesiveness can alone be depended upon for resistance to displacement. In such cases the initial pressure upon the earth should not be much exceeded. ”

“ Merely comparing the weight of a train with that of an embankment, and assuming that the results of vibration at the same rate of speed are so governed is incorrect, for the effect of vibration at the formation level is not regulated by the height of an embankment or the depth of a cutting. The weight of a train may bear a very small relation to that of the quantity of earth slipped, yet the soil may have gradually become in such a state of delicate equilibrium that at last the least vibration will destroy it, even a little of the top soil falling upon the slope ”

“ The marvellous labours of geologists and others have enabled an accurate opinion to be formed of the locality and the depth at which water and certain minerals are to be found and also to indicate the earths in which fissures and seams are frequent; but it must ever be impossible for man to absolutely state that no unstable seams or veins exist over a considerable area of ground, more especially in the superficial beds upon which a dock-wall has to be constructed, although the probability of their presence may be determined with some degree of precision. ”

“ In treacherous earth do not locate a railway close to a road, except at a station, as if the line be placed above the road, a slip upon the railway may result in a slip upon the road; and should the line be below a road, the extra weight or vibration may cause the road to follow the railway and act, as it were, in unison with it. ”

“ In dock, canal, or any earthworks made for the purpose of containing or expelling water, it is obvious the position is entirely dissimilar to that of railway works: for whereas a slip or a subsidence in an embankment upon railway work may be of slight moment and give comparatively little trouble or anxiety, any movement in earthwork constructed for the purposes named is of grave importance, as it may mean the destruction of the work, loss of life and property, not only upon the site but also in the surrounding district. ”

“ In Holland, where the peat is superimposed upon sandy soil, in order to prevent slips in embankments it is found advisable to excavate a trench about 15 to 20 feet in width and as wide as the formation width of a railway or road, until it reaches the subsoil, and to fill it with sand; and when an embankment has to be formed of very porous earth, to make a trench at the toe of each slope, and to fill it with sand so as to act as a counterfort. Peat and sand have been found to laterally spread the most, clay and sand less, and therefore the latter soil stands at a steeper slope. ”

“ In peaty soils an embankment should be formed of light dry materials, be spread out, have equal bearing, and be of as little height as possible, and all hollows and depressions should be carefully filled. The worst state of peaty or bog soils upon which an embankment has to be tipped is when they are no better than a floating mass.
Where a stratum of sound firm soil, such as gravel, lies upon a soft bed of great depth, by increasing the bearing area upon the firm earth and not interfering with it, a stable foundation for an embankment may be obtained. ”

“ In adopting two systems of design of a wall, it is advisable that the change of form be gradual and not made abruptly, or cracks may occur from unequal settlement or load upon the foundations, and also when a concrete bed is used under a wall a lime concrete layer cannot be firmly joined to one composed of more solid and unyielding material, such as Portland cement concrete. Similar walls erected upon different soils are not equally strained, as one earth may scarcely change from the effects of air and water, and another may vary daily according to the weather. ”

“ The same conditions are found in all soils, and the sides of a cutting vary, one may be comparatively compact and free from water, the other in a wet state and disintegrated. They will not permanently repose at the same angle, the slope varying according to the degree of dryness, size, and uniformity of the particles. In all earths in which cohesion is liable to be quickly destroyed, a straight slope is the best as having an even surface, which prevents the formation of depressions and causes the water to drain away, and also offers the least surface to the weather. ”

“ In cohesive soil, such as clay or clay marls, surface protection, combined with systematic and thorough drainage, may be all that is required to make a slope stable, and the erection of an impervious or solid high wall be unnecessary, always provided the earth cannot slide from being superimposed upon an inclined stratum. In fact, retaining walls in retentive soil have been found to induce a slip, because they neither drain the earth nor prevent the additional impregnation of water, and they have consequently been destroyed. ”

“ Should any excessive or violent rainfall succeed a period during which the heat of the sun has caused fissures in the surface of the earth, allowing water to enter, the state of the soil is favourable to movement. Land has also become unstable in mountainous countries because a district has been deforested, or tree-protection much reduced, movement of the earth usually happening after the first heavy rains or thaw succeeding frost or snow. ”

“ In an exceptional situation where a railway must be located in a ravine and close to a river, and the material of which an embankment is made is compact earth or the ground firm, it may be advisable to allow the overflow waters of a river, or the flow of surface water towards it, when the extreme flood level is known, to gently pass over a line of railway, it being kept at such a level as not to impede free working, and to ensure that any back water is not prevented from escaping. ”