Earthwork Slips and Subsidences upon Public Works Their Causes, Prevention, and Reparation
Chapter V.: and by the insertion of a cylinder, with a properly designed
bottom, to prevent the issue of soil to a level some feet below the lowest intended excavation upon the site, or to the depth at which the greatest flow of water is obtained; care being taken that no run of sand or soil is allowed and that the water is not charged with earth, either by a thick gravel layer until the sand ceases to pass through it, or by other means, remembering that the motive power of running sand is that of the pressure of water. The flow should be gently led away, if necessary, to a sump, and discharged by pumping, thus draining the works. The sump should always be lined, not only to prevent any flow upon or into the surface causing saturation, but so as to control and regulate the water some feet below the lowest level of the foundations, the great point being to draw downwards the water from the earth and then to carry it away. An iron or wooden cylinder sump is to be preferred to one constructed of sheet piles or timber-lined, as the soil may be so loose that any shaking or vibration should not be allowed, and a close joint is not easy to attain in timber pile work. It is well to deposit some clay puddle for a little distance round the sump after sinking it in order to weight the soil and steady the cylinder. When a discharging outlet has been made it should be maintained in perfect condition, or a slip or subsidence may occur from leakage or diversion of the flow. It may also happen that no discharge is necessary, for if the “boil” is only, as it were, of local extent and caused by a weak vein in otherwise stable soil, the water may rise to the head level and there remain; the equilibrium being restored which had been destroyed by reason of the upper strata of an impervious character being excavated. The removal of the normal pressure upon the loose soil to some extent, liberates the water, and the head ceasing to be balanced by it, the earth cannot do otherwise than allow water to upraise it. A calculation of the weight of the earth removed may give an indication within which will be the probable head level of the supply, and usually it is much below a head of water that would equal the normal pressure of the soil. Supposing the weight of the earth to be twice that of water, when 10 feet of soil is excavated before a “boil” began, its removal would approximately be equivalent to a 20 feet head of water.
The great point is to confine a “boil” within a certain space, and there to treat it and so prevent the appearance of others and interruption to the prosecution of the works. All agitation of the surface of sand, especially when a “boil” appears, must be prevented, as inducing a disturbed and more porous condition.
When the seat of a “boil” must be built over, the well system of foundations can be used as not only affording reliable support, but also preventing a “boil” extending, and allowing the flow of water to be discharged, care being taken that complete connection is made with a wall constructed upon any other principle. If “boils” appear over a considerable area, it is evident that the disturbance is general, and may either be because the site or the foundations of the works are below the level at which water is usually found in the district, or be produced by the rise and fall of tidal waters. When by the former, drains are required a few feet below the general water-bearing level, and they should intercept the percolation of the land waters and conduct them from the site of the works, or so gently localize them that they can be treated as before described. The land waters are the most troublesome because their volume, time of appearance, and duration of flow will vary, whereas the range of the tidal waters is known, and therefore the effects may be ascertained with some approach to accuracy.
It may be impossible to erect walls in very loose soils without encircling the site with sheet piles to prevent a run of sand, to lessen “blows” and to reduce the disturbance, as placing them upon an impervious stratum maybe prohibitory because of the expense: but the adoption of the well system of foundations down to a firm stratum, or at a sufficient depth to be stable, and the building walls thereon may cause the temporary pile support to be unnecessary and prevent a slip or subsidence. Quick erection and the least exposure or disturbance of earth are essentials in such cases.
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.
Crown 8vo., cloth, price 4s. 6d.
NOTES ON CONCRETE AND WORKS IN CONCRETE.
BY JOHN NEWMAN, _Assoc. M. Inst. C.E._
REVIEWS OF THE PRESS.
=ENGINEERING=—_11th November, 1887_.
“_An epitome of the best practice which may be relied upon not to mislead._”
“The successful construction of works in concrete is a difficult matter to explain in books.”
“All the points which open the way to bad work are carefully pointed out by our author with a pertinacious insistence which demonstrates his clear appreciation of their value.”
=IRON=—_21st October, 1887_.
“As numerous examples are cited of the use of concrete in public works, and details supplied, _the book will greatly assist engineers engaged upon such works_.”
=THE BUILDER=—_24th September, 1887_.
“A very practical little book, carefully compiled, and _one which all writers of specifications for concrete work would do well to peruse_.”
“_The book contains reliable information for all engaged upon public works._”
“A perusal of Mr. Newman’s valuable little handbook will point out the importance of a more careful investigation of the subject than is usually supposed to be necessary.”
AMERICAN PRESS.
=BUILDING=—_19th November, 1887_.
“To accomplish so much in so limited a space, the subject-matter has been confined to chapters.”
“_We take pleasure in saying that this is the most admirable and complete handbook on concretes for engineers of which we have knowledge._”
LONDON: E. & F. N. SPON, 125, STRAND.
TRANSCRIBER’S NOTES
1. Changed “the sinking a sump” to “the sinking of a sump” on p. 202. 2. Silently corrected typographical errors. 3. Retained anachronistic and non-standard spellings as printed. 4. Enclosed italics font in _underscores_.