Tunneling: A Practical Treatise.

In the December, 1901, number of “Compressed Air,” a magazine especially devoted to the useful application of compressed air, is read:

Quantity of Air.

—The quantity of air to be introduced into tunnels must be in proportion to the oxygen consumed by the men, the animals, and the explosions. It is allowed that the quantity of air required for breathing purpose and explosions is as follows:

In a long tunnel excavated through hard rock the number of workmen all together may be assumed at 400 at each end, and each workman is supposed to be furnished with a lamp. No less than ten horses are employed, and the average quantity of dynamite consumed is 600 lbs. per day. From the data given the consumption of air by workmen and lamps would be: 240 × 400 = 96,000 cu. yds.; the consumption of air by horses would be 850 × 10 = 8500 cu. yds.; the consumption of air by dynamite would be 150 × 600 = 90,000 cu. yds.; making a total consumption of air per day of 194,500 cu. yds., or about 8000 cu. yds. per hour.

To obtain good ventilation, then, it will be necessary to furnish every hour a quantity of fresh air amounting to not less than 8000 cu. yds. Since, however, a large quantity of pure air is expelled with the foul air, it is necessary greatly to increase this quantity.

It may be observed, in closing, that the water having its particles divided, as in a fog or mist, rapidly precipitates the gases produced by explosions. Now, when hydraulic machines are used, there is a hollow ball pierced by holes that are almost imperceptible, from which the compressed water spreads in very subtile particles, and this causes the fall of the gases from explosions. Such a method of precipitating gases is very good, but does not have the advantage of supplying new oxygen to replace that consumed by the men, animals, lamps, and explosions; besides, it has the defect of increasing the quantity of water to be removed. In tunnels the pipes used either for conveying the fresh air or for carrying away the foul air, are of iron, having a diameter of about 8 in.; they are fixed along the side walls about 3 ft. above the inverted arch.

LIGHTING.

The object and necessity of a perfect lighting of the tunnel-workings during construction are so obvious that they need not be enlarged upon. Comparatively few tunnels require lighting after completion; and these are generally tunnels for passenger traffic under city streets, of which the Boston Subway is a representative American example. Considering the methods of lighting tunnels during construction, we may, for sake of convenience, chiefly, divide the means of supplying light into (1) lamps and lanterns usually burning oil; (2) coal-gas lighting; (3) acetylene gas lighting; and (4) electric lighting.

Lamps and Lanterns.

—Lamps and lanterns are commonly employed by engineers for making surveys inside the tunnel, and to light the instrument. For ranging in the center line, a convenient form of lamp consists of an oil light inclosed in glass chimney covered with sheet metal, except for a slit at the front and back through which the light shines, and on which the observer sights his instrument. To direct the operations of his rodmen the engineer usually employs a lantern, either with white or colored glass, much like the ordinary railway trainman’s lantern, which he swings according to some prearranged code of signals.

Lamps and lanterns are used by the workmen both for signaling and for lighting the workings. For signaling purposes red lanterns are usually placed to denote the presence of unexploded blasts or other points of possible danger; and colored or white lights are usually placed on the front and rear of spoil and material trains. For lighting purposes, two forms of lamps are employed, which may be somewhat crudely designated as lamps for individual use and lamps for general lighting. Individual lamps are usually of small size, and burn oil; they may be carried in front of the miner’s helmet, or be fixed to standards, which can be set up close to the work being done by each man. Miners’ safety lamps should be employed where there is danger from gas. A great variety of lamps for mining and tunneling purposes are on the market, for descriptions of which the reader is referred to the catalogues of their manufacturers.

Lamps for general lighting are always of larger size than lamps for individual use. A common form consists of a cylinder ten or twelve inches in diameter, provided with a hook or bail for suspension, and filled with benzine, gasolene, or other similar oil. Connected with this cylinder is a pipe of considerable length and small diameter through which the benzine or gasolene vapor runs, and burns when lighted with a brilliant flame. Lamps of this type burning gasolene were extensively employed in building the Croton Aqueduct tunnel. Various patented forms of lamps for burning coal-oil products are on the market, for descriptions of which the manufacturers’ catalogues may be consulted.

Coal-gas Lighting.

—A common method of lighting tunnel workings is by piping coal-gas into the headings and drifts from some nearby permanent gas plant, or from a special gas works constructed especially for the work. Gas lighting has the great advantage over lamps and lanterns of giving a light which is more brilliant and steady. Its great objection is the danger of explosion caused by leaks in the pipes, by breaks caused by flying fragments of rock, and by the carelessness of workmen who neglect to turn off completely the burners when they extinguish the lights. In nearly every tunnel where gas has been used for lighting, the records of the work show the occurrence of accidents which have sometimes been very serious, particularly when fire has been communicated to the tunnel timbering.

Acetylene Gas Lighting.

—The comparatively recent development of acetylene gas manufactured from carbide of calcium has given little opportunity for its use in tunnel lighting, and the only instance of its use in the United States, so far as the author knows, is the water-works tunnel conduit for the city of Washington, D. C. Col. A. M. Miller, U. S. Engineer Corps, who is in charge of this work, describes the method adopted in his annual report for 1899 as follows:—

Electric Lighting.

—By far the most perfect, and at present the most commonly employed means for lighting tunnel workings, is electricity. The light furnished by electric lamps is steady and brilliant, and does not consume oxygen or give off offensive gases. The wires are easily removed and extended, and the lamps are easily put in place and removed. About the only objection to the method is the fragility of the lamps, which are easily broken by the flying stones and the concussion produced by blasting.

CHAPTER XXV.
THE COST OF TUNNEL EXCAVATION AND THE TIME REQUIRED FOR THE WORK.

Cost.

—The cost of a tunnel will depend upon the cost of the two principal operations required in its construction, viz., the excavation of the cross section and the lining of the excavation with masonry, metal, or timber. These two operations may in turn be subdivided, in respect to expense, into cost of labor and cost of materials. It is a comparatively simple matter to calculate the cost of the building materials required to construct a tunnel; but it is very difficult to estimate with accuracy what the cost of labor will be. The reason for this is that it is impossible to foresee exactly what the conditions will be; the character of the material may change greatly as the work proceeds, increasing or decreasing the cost of excavation; water may be encountered in quantities which will materially increase the difficulties of the work, etc. Nevertheless, while accurate preliminary estimates of cost are not practicable, it is always desirable to attempt to obtain some idea of the probable expense of the work before beginning it, and the more usual means of getting at this point will be discussed here.

Two methods of estimating the cost of tunnel work are employed. The first is to calculate the probable expense of the various items of work, based upon the available data, per unit of length, and then add to this a margin of at least 10% to allow for contingencies; the second is to apply to the new work the unit cost of some previous tunnel built under substantially the same conditions. In the first method it is usual to consider the strutting and hauling as constituting a part of the work of excavation. To estimate the cost of excavation involves the consideration of three general items, viz., the excavation proper, the strutting of the walls of the excavation, and the hauling of the excavated materials and the materials of construction.

The cost of excavating the preliminary headings or drifts is greater per unit of material removed than that of excavating the enlargement of the section. The cost of bottom drifts is also always greater than that of top headings, the material penetrated remaining the same. Mr. Rziha gives the comparative unit costs of excavating drifts, headings, and enlargement of the profile as follows:—

The cost of hauling increases with the length of the tunnel. This fact and amount of this increase are indicated by the following actual prices for the Arlberg tunnel:—

In all the prices given above, the cost of strutting and hauling is included in the cost of excavation.

The cost of excavation is not always the same for the same character of materials in different tunnels. The following figures show the prices paid for the excavation of calcareous rock in four different German tunnels:—

The method of tunneling has little influence upon the cost of the work, as shown by the following figures from tunnels excavated through calcareous rock by different methods:—

The Martha and Merten tunnels, excavated through soft ground by the Austrian and German methods respectively, cost $87.95 and $87.55 per lin. ft. respectively. In the excavation of the various sections of the tunnel for the new Croton Aqueduct in America, the following prices were paid:—

It is the practice in America to include the work of hauling under excavation, but not to include the strutting, which is paid for separately. In some cases only the market price of the timber is paid for separately, the cost of setting up being included in the price of excavation. The writer prefers the European practice of including the total cost of timbering under excavation, since the two operations are so closely connected, and since the contractor employs the same timber over and over again. Knowing the dimensions of the several members of the strutting, it is a simple, although somewhat tedious, process to calculate the total quantity required. An idea of the quantity of timber required for strutting in soft ground may be had from the data given on page 55. The quantity will decrease as the cohesion of the material penetrated increases, until it becomes so small in hard rock-tunnels as to cut very little figure in the total cost.

The cost of hoisting excavated materials through shafts depends upon the depth from which it is hoisted, and upon the character of hoisting apparatus employed. The following table, showing the cost of hoisting for different lifts and by different methods, is given by Rziha, the cost being in francs per cubic meter:—

Mr. Séjourné, a French engineer, who has been connected with the construction of numerous tunnels by the Belgian method where he was in position to secure comparative figures, has given the following rules for calculating the cost of tunnels. Assuming A to represent the cost of excavating a cu. yd. in the open air, the cost of excavating the same quantity underground in driving headings will be from 9 A to 11 A, and in enlarging the profile it will be about 5 A. The cost of constructing single-track tunnels varies with the thickness of the lining, and may be calculated by the following formulas:

In these formulas C is the cost per cu. yd. of excavation, including the masonry. For double-track tunnels the amounts given by the above formulas may be used by reducing them about 7¹⁄₂% or 8%.

The second method of estimating the cost of tunnel work consists in assuming as a unit the unit cost of tunnels previously excavated under similar conditions. Mr. La Dame gives the following unit prices for a number of tunnels driven through different materials:

In the following table is given a list of tunnels excavated through different soils, from the most compact to very loose materials, and driven according to the various methods which have been illustrated.

DOUBLE-TRACK TUNNELS.

SINGLE-TRACK TUNNELS.

The Habas tunnel through quicksand, between Dax and Ramoux, France, cost $118.50 per lin. ft. The cost of the Boston subway was $342.40 per lin. ft. The Severn and Mersey tunnels, constructed through rock under water, cost respectively $208.38 and $263 per lin. ft. The First Thames Tunnel, driven by Brunel’s shield, cost $1661.66 per lin. ft. The Hudson River and St. Clair River tunnels, excavated through soft ground by means of shields and compressed air, cost respectively $305 and $315 per lin. ft. The Blackwall double-track tunnel under the River Thames, which is the largest tunnel ever built by the shield system, cost $600 per lin. ft.

In making estimates of the cost of projected tunnel work based on the cost of tunnels previously constructed through similar materials, it is important to keep in mind the date and location of the work used as the basis for calculations. For example, a tunnel excavated in Italy, where labor is very cheap, will cost less than one excavated in America, where labor is dear, all other conditions being the same. Other reasons for variation in cost due to difference of date and location of construction will suggest themselves, and should be taken into full consideration in estimating the cost of the new work.

Time.

—The time required to excavate a tunnel depends upon the character of the material penetrated and upon the method of work adopted. Tunnels driven through soft ground by hand require about the same time to construct as tunnels driven through hard rock by the aid of machinery. Tunnels can be driven through hard rock at about as great a speed as through soft or fissured rock, chiefly because the work of blasting is more efficient in hard rock, and because no time is required in timbering. The following table shows the average rate of progress in different parts of the tunnel excavation through both hard and soft materials in feet per month:—

The following tables showing the average rate of progress have been compiled from the actual records made in the tunnels named:

The following table shows the monthly progress of completed tunnel in feet excavated through rock:

The average monthly progress in feet of excavating tunnels through treacherous ground may be quite generally assumed to be for: (1) clay of the first variety from 43.4 ft. to 60 ft.; for clay of the second variety from 33.4 ft. to 43.4 ft.; for clay of the third variety from 23.3 ft. to 33.4 ft., and for quicksand from 30 ft. to 50 ft. The monthly progress in feet made in sinking the shafts of the Hoosac and Musconetcong tunnels in America was as follows:—

The average monthly progress of sinking shafts in treacherous soils may be assumed to be as follows: clay of first variety, 50 ft. to 75 ft; clay of second variety, 36.75 to 50 ft; clay of third variety, 23.4 ft. to 36.75 ft; quicksand, 16.7 ft. to 33.4 ft.

For the reason that the details change with the various conditions encountered in every work, all the tunnel operations have been treated in a general way, purposely avoiding to give any detail. Also the rate of progress and items of cost of tunnels have been given in a broad manner because they greatly vary in the different works. This information, however, can be easily obtained by consulting the Engineering Magazines, where are reported all the tunnel works of America and Europe, and where are given so many details which are very valuable to expert engineers in charge of similar works, but not to students and people who are looking only for general knowledge.

INDEX

• Accidents and Repairs in the Belgian Method, 152
• Accidents in Tunnels:
• After Construction, 308
• Baltimore Belt Line, 165
• Chattanooga Tunnel, 311
• During Construction, 301
• General Discussion, 301
• Giovi Tunnel, 309
• Repairing of, 304
• Acetylene Gas Lighting, 334
• Air Compressors, Description of, 87
• Air Locks, 264-272
• Air Pressure, 268
• American Method:
• General Description, 172
• Excavation, 172
• Strutting, 174
• Hauling, 175
• Arrangement of Drill Holes, 90
• Artificial Ventilation, 327
• Austrian Method of Tunneling:
• Advantages and Disadvantages, 180
• Excavation, 176
• General Description, 176
• Lining, 180
• Strutting, 177
• Average Progress in Tunnels, 342
• Baltimore Belt Line Tunnel, General Description, 160
• Barlow’s Shield, 242
• Beach’s Shield, 246
• Belgian Method:
• Accidents and Repairs, 152
• Advantages and Disadvantages, 152
• Excavation, 145
• General Description, 144
• Lining, 148
• Hauling, 150
• Strutting, 146
• Bench, 131
• Bends, 268
• Blackwall’s Tunnel Shield, 248
• Blasting-cone, 33
• Blickford Match, 31
• Boston Subway:
• General Descriptions, 203
• Roof Shield, 251
• Boulder Tunnel Relined, 315
• Box-cars, 61
• Box Strutting, 51
• Brandt Drilling Machine, 28, 112
• Brown, W. L., 269
• Brunel’s Shield, 240
• Caissons, 293
• Canals and Pipe Lines, 86
• Cascade Tunnel, 98
• Center-cut, 91
• Center Line:
• Curvilinear Tunnels, 14
• Determination of, 9
• Rectilinear Tunnels, 9
• Simplon Tunnel, 106
• Submarine Tunnels, 265
• Triangulation, 12
• Transferred through Center Shafts, 13
• Transferred through Side Shafts, 14
• Value’s Device, 10
• Centers:
• For Arches, 68
• English Method, 169
• Ground Molds, 66
• Italian Method, 184
• Lagging, 71
• Leading Frames, 67
• Setting Up, 70
• Striking, 71
• Chattanooga Tunnel, Accident, 311
• City and South London Railway Shield, 250
• Classification of Tunnels, 42
• Coal-gas Lighting, 333
• Cofferdam Method of Tunneling, 281
• Van Buren Street Tunnel, Chicago, 282
• Collapse of Tunnels, 302
• Compressed Air:
• For Power, 87
• For Ventilation, 330
• Concrete Lining, 75
• Fort George Tunnel, 139
• Murray Hill Tunnel, 126
• Cost of:
• Double-track Tunnels, 340
• Hauling, 338
• Headings, 337
• Hoisting, 338
• Single-track Tunnel, 340
• Submarine Tunnels, 341
• Subways, 209-217
• Tunnels, 336
• Craven, Alfred, 39
• Craven’s Sunflower, 39
• Cross-section:
• Dimensions of, 20
• Form of, 18
• Hudson River Tunnel Pennsylvania Railroad, 277
• Crown-bar (see American Method).
• Subways, 204-211
• Croton Aqueduct Tunnel, 95
• Culverts, 80
• Detroit River Tunnel, 296
• Diamond Drilling Machine, 27
• Directing the Shield, 265
• Drift, 37
• Drift Method:
• General Discussion, 102
• Murray Hill Tunnel, 123
• Simplon Tunnel, 103
• Drilling Machines:
• Brandt, 112
• Ingersoll, 26
• Drills:
• Diamond, 27
• Hand, 23
• Mountings for, 25
• Percussion, 24
• Power, 24
• Rotary, 27
• Dumping Cars, 60
• Electric Firing, 32
• Electric Lighting, 335
• English Method:
• Advantages and Disadvantages, 171
• Centers, 169
• Excavation, 166
• General Discussion, 166
• Lining, 170
• Strutting, 167
• Enlargement of the Profile, 38
• Entrances, 81
• Erector, 272
• Excavation:
• American Method, 172
• Arrangement of Drill Holes, 90
• Austrian Method, 176
• Belgian Method, 145
• Center-cut, 91
• Enlargement of Profile, 38
• English Method, 166
• Fort George Tunnel, 136
• German Method, 155
• Headings, 37, 91
• Hudson River Tunnel of Pennsylvania Railroad, 273
• Italian Method, 182
• Murray Hill Tunnel, 124
• Quicksand Method, 189
• Pilot Method, 193
• Shield and Compressed Air Method, 267
• Simplon Tunnel, 110
• Excavating Machines:
• For Earth, 22
• For Rock, 23
• Explosions, 33
• Dynamite, 30
• Gunpowder, 28
• Nitroglycerine, 29
• Quantity of, 34
• Storage of, 30
• Failure of Tunnel Roof, 305
• Forgie, James, 269
• Fort George Tunnel, 135
• Foundations for Lining, 76
• Fox, Charles B., 103
• Frame Strutting, 49
• Fuses, 31
• Geological Survey, 3
• German Method:
• Advantages and Disadvantages, 159
• Excavation, 155
• General Description, 155
• Hauling, 158
• Strutting, 156
• Giovi Tunnel Accident, 309
• Graveholz Tunnel, 98
• Greathead’s Shield, 245
• Hand Drills, 23
• Harlem River Tunnel, 285
• Hauling:
• American Method, 175
• Belgian Method, 150
• Italian Method, 185
• German Method, 158
• Hudson River Tunnel of Pennsylvania Railroad, 278
• Motive Power, 61
• By Way of Entrances, 59
• Simplon Tunnel, 111
• By Way of Shafts, 62
• Heading and Bench Method:
• Fort George Tunnel, 135
• General Discussion, 130
• St. Gothard Tunnel, 1
• Headings, 37, 91
• Hewett, H. B., 269
• History of Tunnels, xiii
• Hoisting Machines:
• General Discussion, 62
• Elevators, 64
• Horse Gins, 63
• Windlass, 63
• Hoosac Tunnel, 93
• Hopkins, Stephen W., 135
• Hudson River Tunnel of Pennsylvania Railroad, 269
• Hydraulic Jacks, 260, 271
• Hydraulic Rams, 271
• Illumination:
• Acetylene Gas, 334
• Coal-gas, 333
• Electric, 335
• Hudson River Tunnel of Pennsylvania Railroad, 280
• Lamps and Lanterns, 330
• Inclination of Strata, 6
• Ingersoll Drilling Machine, 26
• Inverted Arch Lining, 77
• Iron and Masonry Lining, 74
• Iron Lining, 73, 261, 276
• Iron Strutting, 55
• Full Section, 56
• Headings, 56
• Shafts, 57
• Italian Method:
• Advantages and Disadvantages, 188
• Excavation, 182
• General Description, 182
• Modifications, 186
• Strutting, 183
• Jacks, 260, 271
• Joining the Caissons, 295
• Lagging, 71
• Lamps and Lanterns, 330
• Lighting (see Illumination).
• Lining:
• Austrian Method, 180
• Belgian Method, 148
• Concrete, 126, 139
• English Method, 170
• Foundations, 76
• General Observations, 78
• German Method, 158
• Hudson River Tunnel Pennsylvania Railroad, 276
• Invert, 77
• Iron, 73, 261, 276
• Iron and Masonry, 74
• Italian Method, 185
• Masonry, 74
• Quicksand Method, 191
• Roof Arch, 77
• Side Tunnels, 79, 83
• Side Walls, 77
• Subways, 207-213
• Timber, 72
• Thickness of Masonry, 78, 83
• Little Tom Tunnel Relined, 321
• Loose Soil (see Soft Ground).
• Masonry (see Centers).
• Masonry Culverts, 80
• Masonry (see Lining).
• Masonry Lining, 74
• Masonry Niches, 81
• McBean, Daniel, 285
• Mechanical Installations for Tunnel Work, 84
• Milwaukee Tunnel, 226
• Mont Cenis Tunnel, 92
• Monthly Progress of Tunnels, 342
• Mullan Tunnel Relined, 319
• Murray Hill Tunnel, 123
• Natural Ventilation, 326
• New York Rapid Transit Subway, 209
• Niagara Falls Power Tunnel, 97
• Niches, 81
• Open Cut or Tunnel, 1
• Open-cut Tunneling:
• General Discussion, 195
• Parallel Longitudinal Trenches, 197
• Single Trench, 196
• Single Narrow Trench, 197
• Transverse Trenches, 200
• Tunnels on the Surface, 200
• Palisade Tunnel, 94
• Pennsylvania Railroad Shield, 270
• Percussion Drills, 24
• Pilot Method of Tunneling, 192
• Plank Centers, 69
• Platform Cars, 59
• Plenum Method of Ventilation, 329
• Pneumatic Caissons, 287
• Polar Protractor, 39
• Portals, 81
• Power Drills, 24
• Power Plants:
• Air Compressors, 87
• Canals and Pipe Lines, 86
• Cascade Tunnel, 98
• Croton Aqueduct Tunnel, 95
• General Description, 84
• Graveholz Tunnel, 98
• Hoosac Tunnel, 93
• Hudson River Tunnel Pennsylvania Railroad, 279
• Mont Cenis Tunnel, 92
• Murray Hill Tunnel, 128
• Niagara Falls Power Tunnel, 97
• Palisades Tunnel, 94
• Receivers, 89
• Reservoirs, 86
• Simplon Tunnel, 117
• Sonnstein Tunnel, 99
• St. Clair River Tunnel, 99
• St. Gothard Tunnel, 133
• Steam, 85
• Strickler Tunnel, 96
• Turbines, 86
• Prelini’s Shield, 251
• Presence of Water, 7
• Prevention of Collapse, 303
• Progress in Sinking Shafts, 343
• Progress of Excavation, 342
• Progress of the Work, 342
• Progress in Simplon Tunnel, 122
• Quantity of Air for Ventilation, 331
• Quicksand Tunneling:
• General Discussion, 188
• Removing the Seepage Water, 191
• Quantity of Timber in Strutting, 54
• Receivers, 89
• Relining Tunnels, 315
• Boulder Tunnel, 315
• Little Tom Tunnel, 321
• Mullan Tunnel, 319
• Repairing of Accidents in Tunnels, 308
• Reservoirs, 86
• Roof Arch Lining, 77
• Roof Shield for Boston Subway, 251
• Roof of Caissons, 287-291
• Rotary Drills, 27
• Ryder, B. H., 296
• Saccardo System of Ventilation, 330
• Saunders, W. L., 88
• Seepage Water, 191
• Seine River Tunnel, 293
• Setting up Centers, 70
• Severn Tunnel, 221
• Shafts, Description of, 40
• Shaler, Ira A., 142
• Shield and Compressed Air Method, 263
• Shield Construction:
• Diaphragm, 256
• Cellular Division, 255
• Dimensions of Shields, 259
• Front End, 254
• General Form, 252
• Rear End, 257
• Shell, 253
• Shield Method:
• Barlow Shield, 242
• Beach’s Shield, 245
• Blackwall Tunnel Shield, 248
• Brunel Shield, 240
• City and South London Railway Shield, 250
• Greathead’s Shield, 245
• History, 238
• Prelini’s Shield, 251
• St. Clair River Tunnel Shield, 247
• Side Shafts, 41
• Side Tunnels Lining, 79
• Side Walls Lining, 77
• Simplon Tunnel, 103
• Soils Encountered in Tunnels, 3
• Sonnstein Tunnel, 99
• Stations of Subways, 207-216
• St. Clair River Tunnel Shield, 247
• St. Gothard Tunnel, 132
• Steam Power Plant, 85
• Stratification of the Soils, 6
• Strickler Tunnel, 96
• Striking the Centers, 71
• Strutting:
• American Method, 174
• Austrian Method, 177
• Belgian Method, 146
• Dimensions of Timber, 54
• English Method, 167
• Fort George Tunnel, 137
• Full Section, 51
• German Method, 156
• Headings, 48
• Italian Method, 183
• Murray Hill Tunnel, 125
• Pilot Method, 193
• Quantity of Timber, 54
• Shafts, 52
• Iron: Full Section, 56
• Headings, 56
• Shafts, 57
• Submarine Tunneling:
• Cofferdam Method, 281
• Compressed Air Method, 225
• Detroit River Tunnel, 296
• General Discussion, 218
• Harlem River Tunnel, 285
• Hudson River Tunnel Pennsylvania Railroad, 269
• Lining, 261
• Milwaukee Water-Works Tunnel, 226
• Pneumatic Caisson Method, 284
• Seine River Tunnel, 293
• Severn Tunnel, 221
• Shield and Compressed Air Method, 263
• Shield System, 238
• Sinking and Joining Sections Built on Land, 293
• Van Buren Street Tunnel, 282
• Subways:
• Boston, 203
• Cost of, 209-217
• Cross-sections, 204-211
• General Discussion, 195-202
• Lining, 207-213
• New York Rapid Transit Railway, 209
• Stations, 207-216
• Sutro, Adolph, 330
• Tamping, 32
• Thickness of Lining Masonry, 78, 83
• Thomson Excavating Machine, 22
• Timber Lining, 72
• Timbering (see Strutting).
• Tremies, 299
• Trussed Centers, 70
• Tunnel or Open Cut, 1
• Tunnels:
• Baltimore Belt Line, 160
• Classification of, 42
• Fort George, 135
• Murray Hill, 123
• Simplon, 103
• St. Gothard, 132
• Hard Rock, 84
• Drift Method, 102
• Comparison of Methods, 141
• Heading and Bench Method, 152
• Heading Method, 130
• Soft Ground:
• American Method, 172
• Austrian Method, 176
• Belgian Method, 144
• English Method, 166
• German Method, 155
• Italian Method, 182
• Pilot Method, 192
• Quicksand Method, 188
• Submarine:
• Detroit River Tunnel, 296
• Harlem River Tunnel, 285
• Hudson River Tunnel of Pennsylvania Railroad, 269
• Milwaukee Tunnel, 226
• Seine River Tunnel, 293
• Severn Tunnel, 221
• Van Buren Street Tunnel, Chicago, 282
• Under City Streets:
• General Description, 201
• Boston Subway, 203
• Turbines, 86
• Vacuum Method of Ventilation, 328
• Value, Beverley R., 10
• Van Buren Street Tunnel, 282
• Ventilation, 325
• Artificial, 327
• Compressed Air, 330
• Natural, 326
• Plenum Method, 329
• Quantity of Air, 331
• Saccardo’s System, 330
• Simplon Tunnel, 120
• Vacuum Method, 328
• Vernon-Harcourt, L. F., 221
• Working Platforms, 286
• Wyman, Erastus, 293