US2107671A - Method of constructing tunnels - Google Patents

Description

. Feb. 8, 1938. I M. l. KILLMER METHOD OF CONSTRUCTINC' TUNNELS Filed July 51, 1937 2 Sheets-Sheet l INVENTOR M795 [KY/27262" BY @5 4); 93 ATTORNEYS .6 5 flaw,

Feb-8, 1938 M. I. KILLMER METHOD OF CONSTRUCTING TUNNELS 4 Filed July 51, 1957 2 Sheets-Sheet 2 Patented Feb. 8, 1938 UNITED STATES PATENT OFFICE METHOD OF CONSTRUCTING TUNNELS Application July 31, 1937, Serial No. 156,648

Claims.

This invention relates to an improved method of tunneling beneath rivers and other bodies of Water.

When constructing a tunnel by the shield 5 method it is customary to advance a shield through the ground and to build up the lining of the tunnel at the rear of the shield. The lining is usually composed of metallic segments having perforated flanges along their side edges by means of which the segments are bolted or riveted together but may be composed of concrete or other material. When the tunnel is being constructed under a body of water this work has to be done under sufficient air pressure to prevent water from entering the shield.

When tunneling through yielding material such as silt, clay, and the like, the greater portion of the material in the path of the shield is displaced upwardly, downwardly and sidewise and only a sufficient amount of the material is admitted into the shield to guide the shield in the desired direction. Hence only a part of the material in the path of the shield has to be mucked out that is, removed by excavating with pick and shovel and tram car. On account of the comparatively impermeable nature of displaceable materials such as silt, clay and the like, there is little tendency for the air under pressure within the shield to escape through the open end of the shield or between the tail of the shield and the tunnel lining. Consequently, the tunneling operations can be carried on with a moderate air pressure, with small constant loss of air and with no danger of a blow, which is a sudden escaping of a large volume of air at the face and consequently a sudden drop of air pressure in the tunnel.

On the other hand when the ground through which the shield is being advanced comprises unyielding porous material such, for example, as sand, gravel, or the like or mixtures of such mateterials, Very little, if any, of the material in the path of the tunnel can be displaced by the forward movement of the shield. Practically all the material in the path of the tunnel has to be excavated within the shield and removed through the shield and the portion of the tunnel back of the shield. This greatly increases the time required to construct a tunnel of given length and correspondingly increases the cost. In addition, on account of the porous nature of the material the air under pressure may escape in large quantities from the tunnel and pass upwardly through the sand, gravel or the like, and be lost.

Furthermore, because of the ease with which water can descend from the river through the porous river bed and enter the tunnel, and for other reasons, it is necessary to maintain a substantially higher air pressure within the tunnel in order to balance the water pressure and prevent it from entering the tunnel. Thus a greater amount of excavating work has to be carried on under a much higher air pressure than when tunneling through displaceable material such as silt or clay. The higher the air pressure the greater the danger to the laborers and others Working in the shield and tunnel. Also the fact that this great amount of excavating work must be done under higher air pressure greatly increases the cost of construction on acount of the fact that the workmen are paid at a rate which increases very abruptly with the increase in air pressure, or, what amounts to the same thing, the number of hours per day which they are permitted by law to work are much shortened as the air pressure under which they are required to work is increased.

A further fact which increases the cost of tunneling through such material is that it is often necessary to lay a clay blanket on the bed of the river in order to weigh down the porous unyielding material through which the tunnel is to be built. This clay blanket helps to reduce the loss of air through the porous material and provides the weight necessary to prevent the higher air pressure required by the porous material from escaping suddenly and disastrously in a blow.

The object of my present invention is to provide an improved method of tunneling through unyielding porous material under conditions where high air pressures are usually required in order to prevent water from entering the tunnel, which will enable such tunneling operations to be carried on under greatly reduced air pressure, thus enabling the work to be done with greater safety and at less expense.

The invention also aims to reduce or eliminate entirely the necessity of laying the clay blanket above referred to on the river bed and to greatly reduce the amount of material which has to be excavated through the tunnel shield.

In accordance with my present invention, when a tunnel is to be constructed through unyielding porous material beneath a body of water, I propose to excavate a trench in such material forming the bed of the body of water, this excavating work being done from the surface of the water, preferably by means of an appropriately constructed dredging apparatus. Where conditions permit, this trench is to be excavated to a depth a material which is easily tunnelable, such, for

example, as clay, silt, or the like. After the refilling of the trench in this manner, I propose to drive the tunnel, or tunnels, through this easily tunnelable material employing a shield, or shields, and advancing them through the displaceable material in the customary manner when tunneling through such material.

In the accompanying drawings, the method of my invention has been illustrated diagrammatically. In these drawings:

Fig. 1 is a vertical section taken transversely of the path, or right-of-way, of the tunnel before tunneling operations are commenced;

Figs. 2 and 3 show similar views after two of the steps have been carried out;

Fig. 4 is a similar viewafter the tunnels (in this case two) have been completed;

Fig. 5 is a view similar to Fig. 3 showing the completion of one of the intermediate steps of building a tunnel through a somewhat different earth formation than that shown in Figs. 1 to 4, inclusive;

Fig. 6 is a view similar to Fig. 5 after the completion of a further intermediate step; and

Fig. 7 is a similar view after the tunnels have been finished.

- Referring now to these drawings, in Fig. 1 the body of water, river, bay, etc. is indicated by reference numeral I and the bed of the river by reference numeral 2. Thematerial indicated by reference numeral 3 comprises a deep layer of sand and gravel which, in Figs. 1 to 4, inclusive, extends to a depth greater than the bottom of the tunnel and rests upon rock which is indicatcdby numeral 4. r

In Fig. 2 a trench 5 has been excavated to a depth below that at which the bottoms of the tunnels are to be located. This trenchextends in the direction of the tunnels and in the event that the upper surface of the rock 4 does. not rise. above the level of the bottom of the tunnels at any point, this trench will be excavated to a uniform depth, such as indicated at Fig. 2, throughout the entire width of the river, or other body of water. I

T As shown in Fig. 3, the trench 5 has been filled with a yielding, or displaceable, material 6, such I for example, as clay, and in Fig. ethetwo tunnels 1 and 8 have been driven through the clay 6 within the trench. In laying the clay 6 within trench 5 it is preferable, if conditions will permit; not to fill the trench entirely full, but to leavedepressions, or hollows, 9 above the locations of the tunnels I and 8, since the driving of the tunnels through the clay forces the material upwardly and levels it off, as shown in Fig. 4. It will be understood that this cannot be done unless the tunnels are to be located a substantial distance below the bottom of the river bed; there must be a sufficient depth of clay above the tops of the tunnels to prevent the air pressure within the tunnel from blowing up through the .end of the tunnel shield.

" The earth formations through which it may be desirable to tunnel vary a great deal, and in Figs. 5 to 7 inclusive, a formation is shown in which the layer of sand and gravel 39, between the surface of the rock 4a and the bed of the river 2a, is shallower than that indicated in the preceding figures. In order to place the tunnels 1a and 89, at the desired depth, the bottoms of the tunnels must be below the upper surface of the rock formation 45. Under such circumstances, it is more practical to excavate the shallower trench 59, than to dig the trench clear down to the surface of the rock 4a. The trench 5a is thereforeexcavated to a depth below the top of the tunnels 1a and 8a and the trench is filled with silt, or clay, 6a. The trench 5a is excavated to a depth below the 'top of the tunnels sufiiciently to permit the dumping of the impermeable material at such a depth that, for example, the upper third of the face will be in impermeable and "yielding material and hence the upper third of the shield may be kept closed with a consequent reduction in the constant-loss of air through the face and a consequentreduction or entire elimination of the danger of a blow or sudden loss of all of the air in the tunnel.

Bulkheadsmay'be built in the tunnel shields extending downwardly from the tops of the' shields to approximately the level of the bottom of the trench 53,, that is to say, the line of demarcation between sand and gravel and clay.

The clay, being displaceable by the movement of the tunnel shield, does not have to be excavated, or mucked out, through the tunnel shield, but is pushed aside by the bulkheads.

While the full advantages of my invention cannot be availed of when tunneling through such formations, since the sand and gravel and rock in the paths of the tunnels must be removed through the shield by pick and shovel, the rock being first blasted to loosen the same, nevertheless it is extremely desirable to employ the improved method. In the first place the placing of the dense, yieldable clay 63, above the tunnels and surrounding the upper portions thereof greatly reduces the direct passage of water from the river vertically downward into the tunnel shields and reduces the escape'of air and the consequent danger of blowing through to the surface of the river. This makes the tunneling operations much safer for the workmen, and, in addition, greatly reduces the cost of construction.

A further advantage is the fact that the amount of material which has to be removed through the tunnel shields is'reduced proportionally to the distance below the tops of the tunnels through which the trench 5a is excavated, this material being displaced to one side by the bulkheads of the tunnel shields.

When the tops of the tunnels 7 and 8 must necessarilybe located at a comparatively shallow distance'below the bottom of the river, it may be necessary to fill in the trench 5s withthe dense yielding clay material to a depth somewhat greater than the normal levelof the river bed 25,, as indicated in Fig. 6. In other words, in addition to filling thetrench '5 a 'clay blanket llJ may advantageously be laid over the tunnels and then dredged out after the tunneling operations are completed. Under these circumstances, the laying of the objectionable clay blanket referred to heretofore is .not entirely eliminated, but the blanket is reduced in thickness to a comparatively small fraction of the depth of clay blanket which would be necessary if the method of my invention should not be employed and the tunnel should be constructed through the sand and gravel and rock without excavating the trench 5a and filling it with the dense, yieldable material 6*.

Reviewing briefly the advantages of the present invention, although a greater amount of material must be excavated to dig the trenches 5 or 5a than would be necessary to excavate under the present practice, the excavating work can be done by machine rather than by hand. This machine which consists of a deep dredging apparatus operating from the surface of the river, can be operated by workmen who are working comfortably under normal atmospheric pressure conditions rather than under air pressure within the tunnel shield. This excavating work can be done without any unusual hazards, and consequently no wage premium has to be paid.

- When the tunnels themselves are being driven, the air pressure under which the men work will be in most cases, greatly reduced, thereby resulting in greater safety and reducing the wage premium to a minimum.

It will be understood that the conditions of earth formation through which it may be desired to construct tunnels vary a great deal and that under some conditions full advantage of the invention can be taken, whereas under others, only some of the advantages may be made use of. It may occur also that full advantage of the invention may be taken for only a part of the construction of a given tunnel. Due to changes in the earth formation along the proposed tunnel route, it may be possible to excavate the trench 5 to full depth, as shown in Figs. 1 to 4, inclusive, for only a portion of the distance, whereas along other portions of the route it may be necessary to excavate the trench to less than full depth, as shown in Figs. 5 to 7, inclusive. In either event, however, wherever it is possible to take advantage of the principle of my invention, the tunnel operations may be carried on with greater safety, more expeditiously, and at less cost than if the tunnel were constructed following the methods employed heretofore.

I claim:

1. The method of tunneling through porous material beneath a body of water which comprises excavating a trench in the porous material, filling the trench with yielding and impermeable material, and advancing the tunnel through said yielding material.

2. The method of tunneling through porous material beneath a body of water which comprises excavating a trench in the porous material to some level below the top of the tunnel but above the bottom thereof, filling the trench with yielding and impermeable material and advancing 60 the tunnel through material comprising said yielding and impermeable material in the upper part of the tunnel and the original porous material below.

3. The method of tunneling through porous material beneath a body of water which comprises excavating a trench in the porous material,

filling the trench with yieldable material having greater density than the excavated material and advancing the tunnel through said yieldable material.

4. The method of tunneling through porous material beneath a body of water which comprises excavating a trench in the porous material to a depth below the top of the tunnel, filling the trench with easily tunnelable material, and advancing the tunnel partly through the porous material and partly through the easily tunnelable material.

5. The method of tunneling through porous material beneath a body of water which comprises excavating a trench in the porous material to a depth below the bottom of the tunnel, filling the trench with easily tunnelable material, and driving the tunnel through said easily tunnelable material.

6. The method of tunneling through porous material beneath a body of water which comprises excavating a trench in the porous material to a depth below the top of the tunnel and above the bottom thereof, sealing the upper portion of the tunnel shield from the top to the level of the bottom of the trench, filling the trench with easily tunnelable material, and advancing the tunnel partly through the porous material and partly through the easily tunnelable material, the latter material being displaced by the advance of the tunnel shield.

'7. The method of tunneling through porous material beneath water which comprises excavating a trench in the porous material to a level below the top of the tunnel but above the bottom thereof, filling the trench with easily tunnelable material to a level substantially above the top of the tunnel, and advancing the tunnel through material comprising said easily tunnelable material in the upper part of the tunnel and said porous material below.

8. The method of tunneling through porous material beneath water which comprises excavating a trench in the porous material to a level below the top of the tunnel but above the bottom thereof, filling the trench with clay, silt or the like to a level substantially above the top of the tunnel, and advancing the tunnel through material comprising said clay, silt or the like in the upper part of the tunnel and said porous material below.

9. The method of tunneling through porous material beneath water which comprises excavating a trench in the porous material, filling the trench with easily tunnelable material to a level substantially above the top of the finished tunnel, and advancing the tunnel through said easily tunnelable material.

10. The method of tunneling through porous material beneath water which comprises excavating a trench in the porous material, filling the trench with clay, silt or the like to a level sub.- stantially above that of the finished tunnel, and advancing the tunnel through said clay, silt or the like.

MILES I. KILLMER.

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