Earthwork Slips and Subsidences upon Public Works / Their Causes, Prevention, and Reparation

by John Newman

By the use of Portland cement concrete, foundations can now be cheaply obtained with the ground in a wet condition, which in the days when it was considered only suitable for secondary works, would have required the employment of expensive methods of construction. It may be unwise to arrest the upward flow of the tidal waters in loose soil except by intercepting, lessening, or preventing it by shore protection, for the upward pressure of the head of water may “blow” up the earth and cause disturbance; on the other hand, should the “boils” be merely superficial and the head very little, a thick watertight covering of Portland cement concrete, when accompanied by the necessary drainage operations, may suffice; the surface water blows being covered, and the pressure of the water being overbalanced by the superimposed weight.

All works to prevent “boils” or to drain waters from the site should, if possible, be executed prior to the excavation, as the effect of draining can then be observed and whether any “boils” arise from land waters or from a tidal flow, and the earth will have had some time in which to subside and become consolidated. A month’s test will afford some criterion in a variable climate and when changes of weather are frequent; but should a long period of drought prevail it may be no indication of the state in which the earth would be in a wet season, or under ordinary meteorological influences; and further, the land waters may take a considerable time in flowing to the shore, depending upon the catchment area, character of the soil, position of the beds, whether the district is drained or not, and many other local conditions.

When the soil is firm clay, the locality of any leakage or water seam in it will usually be indicated by surface exudation over the water-charged vein; also in nearly all compact earth, particularly if of a clayey or loamy nature, and therefore the seat of disturbance may not have to be discovered as in looser or sandy soils.

Should a water-bearing fissure occur in rock and it be necessary to stop it, there being no danger of diverting the flow to another place upon the site of the works, it can be done by means of neat Portland cement mortar pressed down and kept in place by timber strips, weights or other means until it has set; the face of the fissure should be made as clean as possible, and the water-bearing seam be filled and weighted directly a leak appears, or the flow may become much increased and accelerated and a current of water be induced which may become of serious extent.

To avoid slips and movement of the ground when it is necessary that a water-charged bed of sand be excavated to enable a structure to be built upon a firm impervious stratum below it, sheet piles can be used or corrugated iron sheets, strutted at intervals, so as to prevent a run and slip of sand; and the space between them can be excavated, a Portland cement concrete foundation being inserted upon the firm soil, the wall being erected in lengths, and the piles or case being practically three-sided so as to leave no unsupported surface of sand, care being taken to prevent any run between the front and the back of the last built length of wall and the earth, so that each length is erected in a contained area.

INDEX.

• A.
• Absorption, broken earth, [70]
• ——, chalk, [29]
• ——, sand, [34]
• Alignment of public works, vide location, [9]–12, [146]
• Alluvial deposits, safe load upon, [88]–89
• ——, soil, slope, [100]
• ——, protection of the banks of rivers, [126]
• Angular particles in earth, [36]
• Approaches to culverts, [84], [85]
• Arched system, dock-walls, [210], [211]
• Argillaceous rocks, slopes, [24]
• Ashes, slope, [100]
• Atmospheric pressure, influence of, [17]
• B.
• Backing, dock-walls, [214], [215]
• Ballast, upon soft soil, [82], [151]
• Basalt, [18]
• Beach, artificial slope, [180]
• ——, natural slope, [100], [101]
• Benching ground, [160], [162]
• Blue clay, [38], [89]
• Bog-land, safe load upon, [88]
• ——, sustaining power, [152]
• ——, treatment of, [149]–151
• “Boils” in foundations, ascertaining character of, [218], [219], [224]
• ——, disturbance of soil, [218], [220], [221]
• ——, origin and source, [218], [219], [223], [224]
• ——, treatment of, [216], [218]–225
• “Boils” in foundations, well system of foundations for, [223]
• Borings, effect of, [217], [220]
• Boulders, [22]
• Breakwaters and piers, foundations of, [181], [182]
• Brown clay, [13], [42], [43]
• Bulging of ground, [147], [148]
• ——, of walls, [207], [213]
• Burning, slipped earth, [62], [63]
• C.
• Canal and similar earthworks.
• ——, admittance of navigation water, [190]
• ——, clay and loamy soils, [190]
• ——, concrete wall, [193]
• ——, consolidation, [190]–192
• ——, drawing off water, [188], [196]
• ——, failure of, [8], [194]–196
• ——, leakage in, [189]
• ——, peat and bog, [187]
• ——, precautions, [190], [193]
• ——, preparation of foundations, [191]
• ——, protection of surfaces, [188], [192]–194
• ——, puddle wall, when objectionable, [192]
• ——, sand, [187]
• ——, selection of earth, [191], [192]
• ——, —— location, [146], [190]
• ——, time of occurrence of slips, [190]
• Catchwater drains, [76], [77]
• Causes of slips and subsidences in earth.
• ——, principal, [8]
• Causes of slips and subsidences in earth, universality, [1]
• ——, variety of, [1]
• ——, water, the chief cause, [8]
• Causes of slips in cuttings and embankments, enumeration thereof, [2]–8
• Chalk, absorption of, [29]
• ——, affinity for water, [28]
• ——, angle of friction of water in, [28], [29]
• ——, characteristics of, [30]
• ——, classification for earthwork purposes, [31], [32]
• ——, cohesion of, [31]
• ——, cuttings in, [33]
• ——, difficulty of draining, [29]
• ——, discharge of water in, [29]–30
• ——, faults, crevices and pot-holes, [28]
• ——, flints in, [28]
• ——, magnitude of many slips in, [32]
• ——, mutability of, [29]
• ——, non-water bearing, [30]–31
• ——, pressure on, effects of, [33]
• ——, safe load upon, argillaceous, [89]
• ——, —— white, [89]
• ——, separation, danger of, [28]
• ——, slopes, [27], [100]
• ——, treacherous condition, [31]
• ——, —— soil, [13]
• ——, treatment of springs in, [29]
• ——, tunnel entrances in, [32], [33]
• ——, use as drains in other soils, [28]
• ——, varieties of, [26], [27]
• ——, veins and seams in, [29]
• ——, water-bearing level in, [30]
• Classification of earths, [23], [36], [46]
• Clay, beds of, [41], [42]
• ——, characteristics of, [37], [38], [40]–43
• ——, classification of, [46]
• ——, condition of stability, [39]
• ——, contraction of, [38], [39]
• ——, expansion of, [37], [38]
• ——, fissures and cracks in, [38], [39]
• ——, humid, [41]
• ——, load upon, blue, [89]
• ——, —— damp, [89]
• ——, —— diluvial, [89]
• ——, —— intermixed beds, [89]
• Clay, load upon, muddy, [88]
• ——, —— solid, [89]
• ——, —— upheaved beds, [89]
• ——, —— wet, [88]
• ——, —— yellow, [89]
• ——, mud mistaken for solid clay, [42], [43]
• ——, notes upon, blue, [38], [39]
• ——, —— boulder 13, [42], [43]
• ——, —— brown, [13], [42], [43]
• ——, —— gault, [43]
• ——, —— lias, [13], [39]
• ——, —— marl, [45], [46]
• ——, —— mica in, [43]
• ——, —— red, [43]
• ——, —— rock, [22]
• ——, —— sandy, [39]–41
• ——, —— slate, [18]
• ——, over-draining it, [39]
• ——, protecting the surface of, [40]
• ——, slopes, [14], [46]–49, [100], [108]
• ——, testing character of, [40], [41]
• ——, time of slip in, [43]
• ——, underground excavation in, [49]
• ——, weakness in, [43], [44]
• Cohesion of earths, general consideration, [14], [105], [106]
• ——, values, [106]
• Concrete blocks, slopes of, [101]
• Condition of earth, worst, [16]
• Configuration of ground, influence of, [18]
• Consolidation, soft soil, [148], [149], [153], [154]
• Continuous surface, value of, [87]
• Counterforts, earth, [57], [58], [61], [121]
• ——, in slopes, [119]–122
• Covering, nature of, [122], [123]
• ——, slope, [122]
• Crumbling of the surface, [2]
• Crystalline rocks, [21]
• Culverts, approaches to, [84], [85]
• ——, design of, [85]
• ——, failures of, [195]
• ——, form, [83], [84]
• ——, general considerations, [83], [84]
• ——, influence on slips and subsidences in earthwork, [83]
• ——, special systems, [85], [86]
• Cuttings, causes of slips in, [2]–5
• ——, side, [157]
• ——, slips in, require separate consideration, [2]
• ——, vibration in, [136]–141
• D.
• Deposition of embankments.
• ——, effect of, [161]
• ——, failure of, [167]
• ——, form of tip head, [168]
• ——, general, [156], [157], [159]
• ——, height of tip, [163], [164], [165], [166], [167]
• ——, junction of high embankments, [164], [165]
• ——, long lead, [163]
• ——, method of, on soft soils, &c., [154], [155]
• ——, precautions in the, [157], [158], [161], [162]
• ——, preparation of ground, [159], [160]
• ——, from side-cutting, [157], [158]
• ——, side tipping, [167], [168]
• ——, specifications, impracticable, [156], [157]
• ——, steam navvy and the, [169], [170]
• ——, systems of, [159], [161]–164, [166]–169
• ——, weather influence, [167]
• Depth, influence of, in cuttings, [87]
• ——, —— embankments, [87]
• ——, —— foundations, [89], [90]
• Diluvial soil, safe load upon, [89]
• Diversion of land waters, [15]
• ——, —— rivers, streams &c., [196], [197]. Vide River.
• Dock earthworks.
• ——, ascertaining nature of soil, [198], [199], [208]–210, [217], [218]
• ——, “Boils” in foundations, [216]. Vide “Boils.”
• ——, causes of slips and subsidences in, [3]–8
• ——, difficulties of construction, [198]–200
• ——, ditches and watercourses, [201]
• ——, drainage of site and pumping of water, [202], [203], [216], [224]
• ——, execution of, [203], [204]
• ——, foundation, [201]
• ——, liability to slip, [199]–201,204, [205]
• ——, location of, [200]–202, [216], [217]
• ——, pressure of water in, [199], [200]
• Dock-walls.
• ——, arched system, [210], [211]
• ——, back drainage, [213], [215]
• Dock-walls, backing, [214], [215]
• ——, bulging, [207], [213]
• ——, construction of, [205]–207, [211]–213
• ——, counterforts to, [212]
• ——, jetties as face counterforts, [207], [208]
• ——, material, [203], [210]
• ——, piles, use of in, [209]
• ——, Portland cement concrete wall, [223]
• ——, prevention of movement in, [207]–212
• ——, repairing a slipped wall, [213], [214]
• ——, sliding forward of, [207], [208], [213]
• ——, well system of, [223]
• Drainage, ballasting, [82]
• ——, catchwater drains and ditches, [76], [77]
• ——, chalk, [29]
• ——, clay, [73]–75
• ——, controlling discharge, [74]
• ——, counterforts and trench drains, [77]–80
• ——, culverts, [83]–85
• ——, equable, necessary, [150]
• ——, field drains, interception of, [77]
• ——, filling of trench drains, [78], [79]
• ——, formation, [81], [82]
• ——, mixed soils, [72]
• ——, number and depth of drains, [75]
• ——, object of, [65], [72], [73], [81]
• ——, overflowing earthworks, [74], [75]
• ——, peat, [77], [149], [150]
• ——, sand, [77], [80], [81]
• ——, seat of an embankment, [82], [83], [85], [86]
• ——, slope drains, [77]–80, [111], [112]
• ——, soft soils, [73], [149], [150]
• ——, spoil banks, [80]
• ——, springs, [75], [76], [80], [81]
• ——, systems required, [72]–77, [80], [81]
• ——, well system, [81]
• Drifts of snow, protection against, [131]–134
• Drift soil, treacherous, [13], [18]
• ——, —— upon sidelong ground, [143]–145
• E.
• Earths, preservation when loaded, [88]
• ——, maximum safe load upon, [87]–91
• ——, table of weights of, [92]
• ——, treacherous, [13]
• ——, universality of slips in, [2]
• Effect of a slip, cuttings, [50]
• ——, embankments, [50]
• ——, influence of depth of cutting and height of embankment, [50], [51]
• Embankments, ballast upon, [151]
• ——, causes of slips and subsidences, [2], [5]–8
• ——, condition of earth, [97]
• ——, consolidation of soft soil, [148]–151, [153]–155
• ——, consolidation by time, [17]
• ——, deposition of, [156]–159, [161]–9
• ——, deposition, from side cutting, [157], [158]
• ——, depositing upon soft soil, [154], [155], [168], [169]
• ——, deterioration of excavated earth, [93], [94]
• ——, drainage of the seat of, [160], [161]
• ——, failure of, [167]
• ——, fascine mattress bed, [155]
• ——, forming, [158]
• ——, height, safe, [91], [92]
• ——, —— of tip, [164]–167
• ——, high, [95]
• ——, homogeneousness, [158]
• ——, junction of, precautions, [164], [165]
• ——, long lead, [163]
• ——, precautions in deposition, [157]–159, [161]–163
• ——, preparation of ground, [159]–161
• ——, safe maximum heights of, [94]–96
• ——, safe load upon, [88], [93], [94]
• ——, sidelong ground, [142], [143], [145]
• ——, side tipping, [167], [168]
• Embankments.
• ——, soft soil, [147]–149
• ——, specifications, impracticable, [156], [157]
• ——, steam navvy, influence of, [169], [170]
• ——, systems of deposition, [159], [161]–169
• Embankments, tip head, form of, [168]
• ——, vibration, effects of, [136]–141
• ——, weather influence during deposition, [167]
• Estuary or shore embankments.
• ——, closure of, [177]
• ——, deposition of, [176]–177
• ——, design, [171]–173
• ——, effect of erection, [173], [179], [180]
• ——, excavation for, [176], [177], [187]
• ——, height, [179]
• ——, material, [187]
• ——, pressures, calculations showing changes of 182–187
• ——, protection of slope, [174]–180
• ——, shore deposit protection, [176], [177]
• ——, site, [171]
• ——, slope, form of, [174], [180]
• ——, trestle work, and on sea-shore, [180]
• ——, viaducts and, [172], [173], [180]
• F.
• Fascine covering of slopes, [128], [129], [178], [179]
• Field drains, interception of, [77]
• Fissures in slopes, [127], [128]
• Flint, beds in chalk, [28]
• Flood-waters, protection against, [57]
• Foot of slope, general considerations, [115]
• ——, protection and preservation, [115]–131
• Formation, special form of, [159]
• Formation width, ballast, [151]
• ——, influence of, [134], [135]
• ——, junction of embankments, [136]
• ——, lateral settlement, [135]
• ——, severe climates, [134], [135]
• ——, sidelong ground, [143]
• ——, temperate climates, [135]
• ——, value of width, [134], [135]
• ——, wet cuttings, [134]
• “Forming” embankments, [158]
• Friable rock, slopes, [24]
• ——, chalk, slopes, [27]
• Friction of earths, effects of water on, [103]
• ——, general considerations, [101]–103, [105], [106]
• Friction of earths, necessity of relying upon, [105], [106]
• ——, relation to slope, [102]
• ——, table of slopes calculated from coefficient of friction, [104]
• G.
• Glacial deposits, treacherous, [18]
• Gneiss, slopes, [23]
• Granite, slopes, [23]
• Grass, covering slope with, [122]–124
• Gravel, angularity and roundness of particles, [36]
• ——, ascertaining character of, [36]
• ——, boulder, and gravel and sand, safe load upon, [89]
• ——, capability of subsidence, [35]
• ——, classification for earthwork purposes, [36]
• ——, compact, safe load upon, [89]
• ——, counterforts, [119]
• ——, interstices in, [35]
• ——, slopes, [37], [100], [101], [106], [107]
• Ground, configuration of, [18]
• Groynes, protecting slopes by, [174]–176
• H.
• Height, of embankments, [91]–97
• ——, influence of length on safe, [95]
• ——, influence of nature and condition of earth, [97]
• ——, limit of, in embankments, [91]–96
• ——, table of approximate safe maximum heights for different earths, [94]–96
• ——, usual limitations, [94], [95]
• I.
• Igneous rocks, slopes, [23]
• Impairing elements, variableness of, [1]
• Inclined beds, danger in rock, [20], [21], [26]
• Instability, earth’s crust, [1]
• Irrigation earthworks, special causes of slips and subsidences, [187]. Vide Estuary Embankments.
• J.
• Jetties, as counterforts to dock walls, [207], [208]
• ——, foundations of, [181], [182]
• Junction, of high embankments, [136], [164], [165]
• L.
• Land drains, cause of slips, [15]
• Land waters, diversion of, [15]
• Lateral settlement, in embankments, [135], [136]
• Lead, effect of long, [163]
• Lengths, short excavated lengths, when necessary, [33], [143], [203], [204], [225]
• Limestone, [18], [24], [25]
• Load on earth, continuous surface, [87]
• ——, detached portions, [87]
• ——, experiments to ascertain safe, [87], [88]
• ——, influence of area, [87]
• ——, influence of normal load, [90], [91]
• ——, safe, [87]–90
• Loamy soils, slopes, [37]
• ——, safe load, [89]
• Location of earthworks, configuration of ground, [10], [12], [146]
• ——, drift soil, [9], [11], [146]
• ——, obstructing drainage, etc., by embankment, [9]–11
• ——, river near to, [10]
• ——, river and stream diversions, [10]
• ——, road, near to, [10]
• ——, road approaches, [11]
• ——, stations, position of, [10]
• ——, trestles or solid embankment, [12]
• ——, tunnels or cuttings, [11]
• ——, valley or hill-side line, [11]
• ——, valley, stable side of, [10]
• ——, valley, sunny or wooded side, [11]
• ——, wetter side of a hill, [12]
• Loose chalk, [27]
• Loose rock, [24]
• M.
• Maintenance, soft ground, [151]
• Marly chalk, slopes, [27]
• Marly soils, characteristics of, [44]–46
• ——, difficulty of draining, [46]
• ——, safe load upon, [89]
• ——, slopes, [100]
• Marsh earth, slope, [100]
• Marsh land, safe load upon, [88]
• Metalling, slope, [101]
• Mica-schist, hardness of, etc., [24]
• ——, quantity of quartz in it, [24]
• Mixtures of earth, troublesome, [20]
• Moraine, treacherous soil, [18]
• Morass, safe load upon, [88]
• Mud, consolidated, slope, [100]
• Mutability, of the created elements, [1]
• N.
• Normal load, influence of, [89]–91
• Normal pressure, consideration of, [91]
• Number of drains, [75]
• O.
• Object of, drainage, [72], [73], [74], [81]
• Obstruction, of drainage by embankment, [9], [10], [11]
• Open trestle work versus embankments, [180]
• Overflow, drainage by, [75]
• P.
• Peat moss, safe load upon, [88]
• Peat soil, consolidation of, [153], [154]
• ——, drainage of, [149]–151
• ——, nature of, [152], [153]
• ——, necessary test, [151], [152]
• ——, sustaining power of, [151], [152]
• Peat turf, slope, [100]
• Percolation of water, overflow and requisite pumping, [69], [70]
• ——, chalk, [70], [71]
• ——, clay soils, [70]
• ——, cuttings and embankments, [65]–67
• ——, effect of, [66]–69
• ——, excavated earth, [70]
• Percolation of water, fissures, [69]–71
• ——, loamy soils, [70]–72
• ——, marly clays, [70]
• Percolation of water, maximum, [66], [68]
• ——, principles of, [67]–72
• ——, regulation of, [65], [66]
• ——, sand, [71]
• ——, top soil, [70]
• Piers, foundations of, [181], [182]
• Pitching, on unequally consolidated soil, [131]
• ——, precautions respecting, [130]–131
• ——, protection of slope by, [129], [130]
• ——, when necessary, [129], [130]
• Porphyry, slope, [23]
• Pressure, normal, on earth, [91]
• Probability of a slip, [13]–18
• Protective works, burning the slipped earth, [62], [63]
• ——, cover shed and catch trenches, [59], [60]
• ——, different methods necessary, [52]–60
• ——, earth counterforts, [57], [58], [61], [121]
• ——, enumeration of, [53]–55
• ——, exceptional, [55], [57], [58]
• ——, flexible v. rigid drains, [56]
• ——, flood waters, [57]
• ——, general principles, [55]–58
• ——, object of, [52]
• ——, salifiable earth, [59]
• ——, slopes, general considerations, [115]–117
• ——, trickling of surface soil, [58]
• ——, turf and plant, [122]–124
• ——, weighting the foot of, [119]
• ——, when drainage alone required, [56]
• ——, when required, [52]
• ——, where to commence drainage operations, [56]
• Q.
• Quartz, slope, [23]
• Quicksand, safe load upon, [88]
• R.
• Rainfall, influence of, [15], [16]
• Rammed earth counterforts, [61], [121]
• ——, thickness of layers, [120]
• Reclamation embankments. Vide Estuary Embankments.
• ——, special causes of slips in, [8]
• Removal of slipped earth, general considerations and treatment, [60]–64
• Repairing slope, [121]
• Reservoir embankments, [187], etc. Vide Canals.
• Retaining walls, desirability, [117], [118], [146]
• ——, draining back of, [117]
• ——, failure of, when probable, [118]
• ——, form, [118], [119]
• ——, protection to slope, [115]–119
• River banks. Vide Canals, [187], and
• ——, ——, Estuary Embankments.
• ——, protected v. unprotected slopes, [48], [49]
• ——, slopes of, [48]
• ——, tree protection of, [126], [127]
• River diversions, [196], [197]
• Road metalling, slope, [101]
• Rock, ascertaining character of, [18]–21
• ——, character, etc., [18]–22
• ——, classification for earthwork purposes, [23]
• ——, crystalline, [21]
• ——, examination of, [19]
• ——, general consideration, [18]–26
• ——, inclined beds, [20], [21], [26]
• ——, mica schist, [24]
• ——, nature of some, [21], [22]
• ——, safe load upon, [90], [91]
• ——, sandstone, [90]
• ——, schistose, [24]
• ——, slopes, friable, [24]
• ——, ——, loose, [24]
• ——, ——, sedimentary, [23]
• ——, stratified, [18]–20
• ——, treacherous condition of, [8], [9]
• ——, unevenness of surface, [18], [19]
• ——, unstratified, [18]
• ——, variation of character, [18], [19]
• ——, water levels in, [24]
• Rubble mound, safe load upon, [91]
• ——, slope, [101]
• S.
• Salifiable earth, [59]
• Sandstone, [19], [22], [25]
• Sandstone, slope, [23], [24]
• ——, in tropical climates, [25]
• Sand, absorption of water, [34]
• Sand, angularity v. roundness of particles, [36]
• ——, capability of subsidence, [35]
• ——, compact, safe load upon, [89]
• ——, delicate state of some, [34]
• ——, drainage of, [34]
• ——, drawing away of, [33]
• ——, excavating in short lengths, [33], [143], [203], [204]
• ——, firm, safe load upon, [89]
• ——, interstices in, [35]
• ——, light sand, protection of, [123]–125
• ——, loose sand, safe load upon, [89]
• ——, mutability of condition, [34]
• ——, sand “boils” in foundations, Vide “Boils.”
• ——, silty, safe load upon, [89]
• ——, slopes of repose, [36], [37], [100], [106], [107]
• ——, soft sand rock, [90]
• ——, springs in, [33]
• ——, superficial beds of, [89]
• ——, when likely to slip, [34]
• Sandy clay, [39], [40]
• Schistose rock, [24]
• Seat of embankment, drainage, [160]
• Setting out, with reference to earthwork, [9]–12
• Settlement, lateral, of an embankment, [135]
• ——, provision against in slopes, [125], [126]
• Shales, characteristics of, [20], [21], [44]
• ——, iron pyrites in, [44]
• ——, safe load upon, [89]
• ——, slopes, [21], [100]
• Shore embankments. Vide Estuary Embankments.
• Sidelong ground, cuttings and embankments upon, [142]–146
• ——, depositing embankments upon, [145], [146]
• ——, excavating in short lengths, [33], [143], [203], [204], [225]
• ——, object of precautionary works, [142]–145
• ——, precautions, [142]–146
• ——, when inclined rock, [146]
• ——, when especially treacherous, [144]–146
• ——, varying the slope, [146]
• Silt, safe load upon, [88]
• ——, slope, [100]
• ——, treacherous, [18]
• Slake, safe load upon, [88]
• Slate rock, [21]
• Slipped earth, treatment and removal of, [60]–64
• Slips in canals, special causes, [8], [187]
• —— time of occurrence, [190], etc.
• —— docks of occurrence, [187]
• —— drainage works, [187]
• —— irrigation works, [187]
• —— reclamation works, [187]
• —— waterworks, [187]
• Slips in cuttings, causes of, [2], [3], [4], [5], [8]
• ——, embankments, causes of, [5]–8
• Slips, immediate action necessary, [61]
• Slopes, bare, when can be left, [125]
• ——, cess upon, [111], [113], [114]
• ——, counterfort at foot of, [119]–122
• ——, curved, [109]–111
• ——, disturbance of, [111], [112]
• ——, fascine covering, [128], [129]
• ——, fissures in, treatment of, [127]–128
• ——, flat, should not be too, [98]
• ——, form of, [107]–108, [110], [111]
• ——, general considerations, [98]–99, [105]–110
• ——, nature of covering, [122]–131
• ——, object of protection, [119], [122]
• ——, permanent, of earth, [98]–101, [106]–109, [146]
• ——, precautions concerning tree protection, [126], [127]
• ——, protection and preservation, general considerations and different systems, [115]–131
• ——, protection against burrowing animals and crustacea, [127]
• ——, protection of light sand, [123]–125
• ——, protective coverings, [122]–129
• ——, provision against settlement, [125], [126]
• ——, range of slopes in different earths, [100], [101]
• ——, repairing, [61]–64, [121], [122]
• ——, sand veins in, [120]
• ——, steepest, [112], [113]
• Slopes, stone pitching upon, [129]–131
• ——, terraced, [111]
• ——, time to trim, [125]
• ——, trees and shrubs upon, protection by, [126], [127]
• ——, trench drains in, [77], [78], [111], [112], [121]
• ——, trimmed as excavated, [111]
• ——, turfing, grass and plant protection, [122]–127
• ——, varying the form of, [109], [110], [111]
• ——, walls, [117]–119
• Snow-drifts, prevention of, protection against, [131]–134
• Soft soil, consolidation of, [153], [154]
• ——, depositing embankments upon, [154], [155]
• ——, drainage, [73], [149]–151
• ——, embankments upon, [147]–149
• ——, equable drainage necessary, [150]
• ——, influence of ballast on formation, [151]
• ——, sustaining power of, [151], [152]
• ——, testing, [148], [149], [152]
• Springs in chalk, treatment of, [29]
• Subsidence, capability of sand, [35]
• —— in soft ground, [151]
• Subsidences in embankments, causes of, [5]–8
• T.
• Time of occurrence, slips, [13]–17
• ——, usual, [15]–17
• ——, submerged and unsubmerged work, [17], [189]
• Trap rock, slopes, [23]
• Treacherous earths, [13], [204], [217]
• Tree protection, general, [16], [126]
• ——, precautions concerning, [126], [127]
• ——, slopes, [126], [127]
• Trickling of surface soil, [58]
• Trimming slopes, [111], [125]
• Tunnels, entrances of, in chalk, [32]
• Turfing slopes, [122]–126
• U.
• Universality of slips, [1], [2]
• Unstable soils, [13], [204], [217]
• Upheaval of ground, [147], [148]
• V.
• Variableness of, impairing elements, [1]
• Variety of causes of slips and subsidences, [1]
• Viaduct, versus embankment, [171]–173, [179], [180]
• Vibration, in cuttings and embankments, [136], [137]
• ——, deteriorating influence of, [136]–141
• ——, effect on earths, [136], [137]
• ——, influence of, [8], [9]
• ——, lateral pressure and, [137]
• ——, test of effects, [141]
• W.
• Water, the chief cause of deterioration of earth, [8]
• Water-bearing level, [14], [24]
• Waterwork earthworks, special causes of slips and subsidences in, [8], [187]. Vide Canals, etc.
• Water pressure in cuttings, [14]
• Weights of different earths, [92]
• Widening works, consideration respecting slopes, [112]–114
• ——, steepening the slopes, [112]–114
• Y.
• Yellow-clay, [43], [89]

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, STAMFORD STREET AND CHARING CROSS.

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