| Quality of Soil. | Heading. | Excavation of Shafts. | Enlargement of Profile. | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| By hand. | By machine. | By hand. | By machine. | By hand. | |||||||||||
| Very loose soil | 16.7 | - | 26.8 | ... | 6.6 | - | 16.7 | ... | 6.6 | - | 16.7 | ||||
| Loose soil | 33.4 | - | 100 | ... | 16.7 | - | 33.4 | ... | 16.7 | - | 33.4 | ||||
| Soft rock | 66.8 | 233.8 | - | 334 | 33.4 | - | 66.8 | 66.8 | - | 132.6 | 33.4 | - | 50 | ||
| Hard rock | 50 | - | 66.8 | 233.8 | - | 334 | 33.4 | - | 50 | 66.8 | - | 132.6 | 66.8 | - | 100 |
| Very hard rock | 33.4 | 233.8 | - | 334 | 16.7 | - | 33.4 | 66.8 | - | 132.6 | 66.8 | - | 100 | ||
The following tables showing the average rate of progress have been compiled from the actual records made in the tunnels named:
| Name of Tunnel. | Dimensions in Feet. | Monthly Progress in Feet. | Character of Material. | Observations. |
|---|---|---|---|---|
| Excavation of headings by hand: | ||||
| Mount Cenis | 10 × 10 | 65.8 | Schist, | Bottom drift. |
| Sutro | 6.7 × 5.7 | 70.14 | Quartzose, | ... |
| St. Gothard | 8.4 × 8.7 | 70.14 | Granite, | Top heading. |
| Excavation of headings by machine: | ||||
| Mount Cenis | 10 × 10 | 188.7 | Calcareous schist, | Bottom drift. |
| Sutro | 8.15 × 10 | 227.45 | Quartzose, | ... |
| St. Gothard | 8.4 × 8.7 | 339.45 | Granite, | Top heading. |
| Trari | 8 × 9.35 | 167 | Gneiss, | Top heading. |
| Arlberg | 8.35 × 9.35 | 474.2 | Mica schist, | Bottom drift. |
| Palisades | 16 × 7 | 160 | Trap rock, | Top heading. |
| Busk | 15 × 7 | 126 | Granite, | Top heading. |
| Cascade | 16 × 8 | 180 | Basaltic rock, | Top heading. |
| Franklin | 15 × 7 | 240 | ... | Top heading. |
The following table shows the monthly progress of completed tunnel in feet excavated through rock:
| Name of Tunnel. | Progress in Feet. | Material. | Method. |
|---|---|---|---|
| Cascade | 207 | Basalt, | Top heading. |
| Palisades | 186 | Trap rock, | Top heading. |
| Busk | 190 | Granite, | Top heading. |
| Tennessee Pass | 169.5 | Granite, | Top heading. |
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:—
| Name of Tunnel. | Dimensions in Feet. | Depth in Feet. | Progress in Feet. | Character of Material. |
|---|---|---|---|---|
| Hoosac: | ||||
| East shaft | 15.4 × 27.7 | 1035 | 21.7 | Mica schist. |
| West shaft | 8 × 16 | 267 | 16.7 | Gneiss. |
| Musconetcong: | ||||
| Vertical shaft | 8.35 × 16.7 | 113.5 | 100 | Loose rock. |
| Inclined shaft | 8.35 × 26 | 304. | 32 | Loose rock. |
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.