US147055A - Improvement in the art of tunneling - Google Patents

Description

UNITED lSTATES PATENT OFFICE.

DF. TITT C. IIASKIN, OF VALLEJO, CALIFORNIA.

IMPROVEMENT IN THE ART OFTUNNELING.

Specification forming part of Letters Patent No. 147,055, dated February 3, 1874; application filed December 9, 1.873.

of the excavation or the infiltration or irruption of water is to be apprehended. Its object is effeetually to prevent such incidents :in a cheap and simple way, to which end my improvement consists in filling the excavation with compressed air of a density sufficient to resist the inward pressure during the construction of the shell or wall of the tunnel.

The mechanical appliances for carrying out my invention are well known to engineers, and obviously may be varied in many ways in the details of their construction and application to meet the varying conditions under which the operations are to be performed, such application, however, involving` nothing more than engineering skill or that of the constructor.

The accompanyingl drawings represent the best way of carrying out the details of my invention now' known to me.

Figure l represents a vertical longitudinal central section through a tunnel in process of construct-ion by my improved plan; Fi 2, a vertical transverse section therethrough on the line A of Fig. l. Fig. 3 represents a side elevation, part-ly in section, through the airlock.

In this instance the tunnel is shown as partially completed. A working-shaft, a, leads into the tunnelb, which is divided into two or more compartments by an air-tight diaphragm, bulk-head, or air-lock, d. This air-lock is constructed so as to be movable at pleasure, and is, by preference, kept up as close to the tunnelhead as convenience will permit. The com partment or portion of the tunnel in advance of the air-lock forms a workin gchamber or compressed-air chamber, b. Compressed air is forced into this chamber by means of a pipe, g, communicating with a suitable pump, and passing through the air-lock. This pipe is made flexible and extensible in order to accommodate the adjustments of the airlock. The airpump may be located in the workingchamber, if preferred. A gas-pipe, f, may also be introduced through the air-lock. An exitpipe, or waste-pipe, fi, leading from the compressed-air chamber to the surface, may be used for ventilation or to carry off waste water, sand, Ste. The air-lock is supplied with valves or doors 7L to retain the air, while permitting ingress and egress to the working-chamber.

I make no claim to the special construction of the devices above described, as they are well known to engineers.

In working by my improved system,the air lock is adjusted in position, the air compressed in the chamber b, and the excavation proceeds in the ordinary waybeyond the masonry-work K. The distinguishing feature of my system, however, is, that instead of using temporary facings of timber or other rigid material, I rely upon the airpressure to resist the caving in of the wall or the infiltration of water until the masonry wall is completed.- This pressure is, of course, to be regulated by the exi gencies of the occasion and may be varied from anything above that of the atmosphere to iifty pounds to the square inch, which is about as much as the human system will bear with safety. The effect ol' such pressure has been found to be to drive water in from the surface of the excavation, so that the sand becomes dry. In case a jet-seam or small stream of water is encountered, I supply a temporary shield of canvas, leather, or other light flexible integument to the wall, against which the pressure instantly forces it and sea-ls the leak. This device is also very efficacious in preventing the escape ofthe compressed air through leaks in the sides or walls of the excavation. After completing the masonry walls of large tunnels, I allow the debris (l to accumulate in the bottom, as shown -in Fig. l, until the tunnel is completed, leaving an opening only large enough for working purposes. By this means the area of the airlock, the surface exposed to pressure, and the consequent liability to leaks are materially diminished.

These three features constitute the leading characteristics of myinvention, namely: First, the use of compressed air acting directly upon the excavation walls to prevent leakge or cav 2. The method herein set forth of preveniing` leakage in the excavation surface of the Working-chambenby the application thereto of a liexible integument held in position by atmospheric pressure.

3. The method herein `set forth of partially rei'illingg,` the completed tunnel in advance ot the air-lock7 to diminishthe air-surface thereof.

In testimony whereof l have hereunto sub scribed my name.

D. C. HASKIN. W'itnesscs:

E. C. DAVIDSON, H. Monsns

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