US1277107A

US1277107A - Tunneling.

Info

Publication number: US1277107A
Application number: US21487718A
Authority: US
Inventors: John F O'rourke
Original assignee: Individual
Current assignee: Individual
Priority date: 1918-02-01
Filing date: 1918-02-01
Publication date: 1918-08-27
Anticipated expiration: 1935-08-27

Description

J. F. OROURKE.

TUNNELING. vlumlcnmou FILED ria. l. |919,

Patented Aug. 27, 1918"- l SHEETS-SHEET 2 0%? www we.

@MW n @55M J. FOROURKE. TUNNELING. A'Pmcfnou hun ria. l'. ma.

'Patented Aus. 21, 19m l igt J. F. GROURKE.

TUNNELmm APPLICATION FILED FEB. 1.1918.

E SHEETS-SHEET 4.

@www "Af-@M I. F. O'ROURKE.

TUNNEUNG. y

APPLICATION FILED FEB. I IQIB.

1,277,1@1 Patented Aug. 27, 191s.

6 SHEETS-SHEEI' 5.

J. F. URUUHKE.

TUNNELING. APPLICATION FILED FEB. l. 19,18.

'Patented Aug 27,1918

wwf a Jolmwowourk UNITED STATES PATENT OFFICE.l

JOEIN F. OROULILKLEI,r OF NEW YORK, N. Y.

TUNNELING.

Specification of Letters Patent. Patente Aug', .27, 191 8.

Application filed February 1, 1918. Serial No. 214,877.

To all whom t may concern:

Be it known that I, JOHN F. ORoUuxa,

face would not stand up of itself and into such spare the shield was shoved forward thus providing space in the tail of the shield in which to erect another ring.l Repeating this process of excavation, shoving and erecting successive rings constitutes the method of shield tunneling.- y

As the bottom of the shield is usually'. built about the length of a ring or shove shorter than the top, .the faceJof the excavatio'n lies just under the end of theshield at the-top, and a slope of earth is allowed to stand at the bottom when the ground per'- mits, into which the shield readily. shoves,

so that generally the vertical face of the excavation extends onl 1mm. In 'soa grou ,like sin, the shield is closed in front and shoves theground ahead of it, or the shield may have a small opening through which some of the ground enters during a shove, but this condition is unimportant in designing the shield as it must be prepared to go through harder ground when encountered, and so is valways built with an open face overhanging at the top.

`It is also usual to divide the shield into two or three levels at the forward end` divided by platforms fitted with extensible fronts operated lwith hydraulic jacks from which the `excavation is carried on, and which hold the timbering and breast boards before and during the shove. These platforms have always been designed to reach the one vertical yface heretofore used and "the form of the Vshield itself'hasbeen' adapted to inclose one vertical faceof the excavation.

When a tunnel is under water or in waterbearin'g ground compressed air is generally used. The pressure is usually maintained in the tunnel and shield alike, equal to the pressure in theground water at or near the only part way to the bot-' bottom of the shield, so that the pressure 0f the compressed air at the top of the shield is in excess of the pressure of the ground water at that level, proportional to the height of the shield. The tendency of this unbalanced pressure is to blow out the ground at the top of the shield, which sometimes happens When the cover of earth is insuilicient to hold the air. The usual practice to prevent this is to maintain.. a cover vof earth one and a quarter times the diameter of the tunnel above the shield, which A gives a small margin of weight in excess of l the lifting power of the unbalanced air pressure.

It is obvious that if the air pressure 'at the top of the shield could be'kept atsomething near the water. pressure at that i, oint that` the danger of blowouts would e greatly lessened, and that the work would be done 1n the upper part of the shield underless air ressure and with less and abor. of the larger tunnels-that have'been constructed, and in the shields for which airA chambers on separate levels wereiprovided, but it was 4foun impossible', in the desi gn of shlelds used, to prevent thehigher ressure in the lower air chamber from passing into` that above4 at the common vertical face.

As the tunnels in which the attempt was made, so far as I am aware, were of mqd'- erate diameter and well within the limite` up to'which clay blankets could be used v(if suficient thickness to counter-balance the unbalanced air pressure, the work was done Without the use ol the multiple air pressures. Had a tunnel been designed of such size that theclay blankets would block up the river above, such tunnels would not have been built by the known methods and a number of smaller tunnels would have been built, wherefore small tunnels have been thenrule heretofore. i

One object of my invention` is .to rovide meansby which air chambers in tie forward part of the shield on successive levels can maintain air pressures in each suitable for 'working against the water pressure in the ground ,in mnt of itself without being aifected by the higher air pressure of a lower cost for" power This Vfatt was perceivedlu some tion in eorres|mmliug steps, separated from ear-h other by floors in the shield. and their cutting edges on the forward parts, thereof, which are air tight and compel the comt5 pressed air that escapes into the ground to ascend without obtainiugacress to the chamber above. lintrauce of air from a chamber below into a chamber above is etfectually prevented b v the tact that'. thi` compressed air when it enters the ground and commences to rise. immediately expands to the pressure of the adjacent ground water, which pressure is constantly lasst-ning upward. so that the es( apingr an' in the ground can liever be at a higher pressure than that ot' the air in the chamber itlis passing, since that pressure also is regulated by the water pressure in front.

There might be circumstances in which it would be advantageous to have the air chambers step backward from top to bottom and also cases in which the air chambers would be given independent telescopic motion in the shield` but the principle remains the same of maintainin the. faces of the excavation in Ldifferent mrtlcal planes so as to' spill separately theV compressed air o fditferent pres- -su'res'f-out into the'groundwhere Vthey can harmlssly expand unconfned'.

The height of the 4floors above one another can be' made as most convenient -for theexcavation and unbalanced air ir'ess'ure. The

, unbalanced air pressure iat t ie top of the shield-in thecase of multiple air chambers necessary earth cover, or clay blanket in lieu of same, is no longerrequired proportional tthediarneter-'ofthe #shield butto `the heightof the top air chamber where that or chambers bclow and so with my improved shield the formel-'limitation of size of tunnels to be constructed with the use of. compressed air disappears.- 1

plished by having air chambers ea able of maintaining di'erent pressures at i'erent levels is that the pressure in the tunnel itself can'be maintained at a desired pressure independent et the air pressures in the air chambers. The d'oorsof the air locks are hung` on the sides of the openings inst which the pressure comes. The air loc S are fitted ,with butts inside and outside of the openings so that when the doors are hun correspondingly they act. equally we whether the 'higher pressure is in the air chamber or in the tunnel. The aforesaid independence of pressures between those at the front. of the shield and that in the tunnel proper gives great latitude in the use of compressed air in tunnel construction. Heretofore if the top of tite. shield was above water level in loose ground with enough wa' G5 ter in the ground at the bottom part of the isonly that of the top chamber, so'that the' height-is not less than that of the chamber- Another very important object accom-- shield to require the use of compressed air, great ditiieulty was encountered because of the water, even in small diameter tunnels. By the use of my improved shield, having air chambers adapted for different pressures corresponding to the water pressures at their fronts, the aforesaid ditiiculties are overcome. Air chambers above the water level would contain free air. Such free air chambers and any chambers below water level holding compressed air of less pressure than that in thetunnel, would have their air locks arranged to hold against the tunnel pressure and thus former ditiiculties in holding compressed air in'a tunnel that is partly above water level is obviated. The importance of the foregoing is obvious when it is considered that improved methods of shield tunneling enable such tunnels to be driven under city streets without disturbing the surface or adjoining buildings and that by reason of this improved shield'the matter of where the top of the ground water lies is no longer of importance, since compressed air can 'be used with the to i of the. water lyilplg at any level in the shie d,-;f

invention alsocoinpriscs' no vel details of nnprove'menLand combinations of arts that willwbe more fully hereinafter set orth and then pointed'outJnthe claims.

Reference is to lbeliadto theyaccompanying drawings forming art hereof -whereim g `ig'ure 1 is al'vc'rtrca sectionof-a-tunnl shield embodying my invention,lillu'strating the location of the sheeting orbreastboarding 1 00 l at the'face oiseveral. com artments before shoving the ShieldfprWar ly; '-'Figs. 1 and l" are detail` sections 'throughjair locks in the shield; Fig. 2 iszayiew 'substantially similar to Fig. 1, illustratin the shield as shoved forwardly iii thefeart i,'ffshowing the faces of several working lair-chambers on di'erent planes ready 'for excavation thereof; Fig. 3 is an enlarged detail section of the cutting edge of a chamber of the shield; Fig. 4 is an end view of the shield looking from the'lefthand side of Figs. 1 and 2; Fi 5 is a cross section of an air lock of the lshield; Fig. 6 isa perspective view within a tunnel lookin in the direction of my im- 1 15 proved shield, iustrating astep in the erection ofblocks in the tunnel lining; Fig. 7 is a vertical section of my-im roved shield provided with movable r'orklng air chambers; Fig. 8 is an enlar ed detail of part o f Fig. 120 7 ;-Fig. 9 is an en urged section illustrating movable working air chambers of the shield; Fig. 10 is an enlarged detail of part of Fig. 9.

n the accompan ing drawin the 'numeral 1 indicates t egnor s ell of the 125 main body )ortion ofl l improved shield` which may e constructed in any approved manner, such as by means of plates, beams and the like properly riveted and bolted together as usual in a circular form of tun- 18.0

' nel shield. Within thtail of the shield the rings 2 of the tunnel ning may be erected in any usual or suitable manner, wluch'rings may comprise blocks 21 of concrete, metal, or other material installed in any desired manner. Within the shield, and forward of the tail portion where the lining is erected, are working air chambers indicated at 3,11, 5, (i, which are open at their forward or cutting edges, which forward or cutting edges are on different planes` and said chainbers are on different levels. There may be two or more such chambers on different levels according to the diameter of the shield or the work to be done. I haveillustrated chambers on four levels assuming that the shield illustrated is adapted for the construction of a tunnel of relatively lar e diameter, sayr from forty to fifty feet in iameter. The floor or bottom Wall 7 of the Y lowest chamber and the roof or upper wall 8 of the upper chamber may be comprised in the wall or skin of the shield, and the Hoors of the intermediate chambers may comprise platforms 9` 10 and 11 suitably built horizontally within the shield. Such floors or platforms may comprise horizontally disposed beams 12 and upper and

lower plates

13, 14, preferably riveted together and secured to the skin of the shield, whereby the floors or platforms wi ll be united to the skin of the shield in a rigid and lair Itight manner. A partition or wall is indicated at l5 at the rear of each chamber, and which may be secured to beams 16 that are'secured 1between the several -floors. Angle irons at "1 7fmay be provided between the floors, walls 1,5-and beams 16 for rigidly securing them together and to make air tight joints. At 18 are air locks for each chamber adapted to open at one end within the corresponding chamber and at the other end within or toward the tail of the shield behind thewall 15. Said air locks may be of any approved form `-secured air tight in openings in the Walls 15, as by means of angle irons 20 riveted respectively to thcwall l5 and posts 16.

Doors

21, 22 are provided at opposite ends of said airlocks to permit the passage of men and materials to or through the air locks. Since there will be, under some conditions of use of 'my improved shield,

material difference of air pressure in thelocks, on the lefthand sides facing the locks from either end, (Figs. 1, 1", 2, 4; and 5), and the butts 25 are on the inside faces of thel end walls of the air locks, but on the opposite sides of said end walls with respect` a

chamber

3, 4, 5 or 6 is greater than that in the tunnel, the doors may be hung agalnst theends of the air locks, as illustrated in Figs. 1 and 2, wherein the door 22 within the chan'ibcr closes against the exterior of the end wall of the lock within such chamber` and the door 21 within such lock closes against the inner wall at the rear ot' the lock toward the tail of the shield, whereby passage through such lock under such different air pressures may be effected. If, however, the air )ressure within one of such chambers is equal to or lower than the air pressure within the tunnel such doors will be re` versed, that is to say, the door 22 would be removed and replaced within the lock and hung upon its forward butts therein to swing against the wall of the lock `within the chamber,.and the. door 21 wouldbe removed and hung upon the butts 25 within the tail of the shield, to swing against the exterior face of the wall at the rear of such loclft` within thel tail of the shield, whereby passage through the lock may be effected. The arrangement described is such that only one door is provided for each end of each lock, and by reason of the ability to shift the door so as to swing against the outer or the inner face of an end wall of the lock, there is no danger of improperly setting the doors at the ends of the lock with respect to air pressures, which might occur were two doors provided at each end of the lock, such as one exterior thereof and one therein.

With the' arrangements described, air pressures may be, maintained within the

chambers

3, 4,- 5, 6 of any desired degree irrespective of the air pressure i'naintained within the tail of the shield beyond the locks and within the tunnel, to hold back water and ground `at-'tlle faces 2G in the cxcavations in the earth. The forward working or cutting edges of the chambers 3. 4, 5, 6, indicated at 3, 4*, 5, 6, are in different planes and different levels, which is effected by having such cutting edge of one chamber extending forwardly beyond the main circumferential portion of the shield farther than lthe cutting edge of another chamber.' In the accompanying drawings I have illustrated the cutting edge of chamber 2 as ex'- tending farther forwardly than the cutting edge of the chambers thereabove, the cutting edge 4' as extending farther forwardly than the cutting edges, 5*. 6*, and the cutting edge 5 as extending farther forwardly than the cutting edge'ti. Such arrangement will hold good with respect to the number of 3 such compressed air working chambers as the shield may be provided with, whereby the chambers and their respective cutting edges extend beyond one another in steps. By the arrangement described a higher air l0 pressure may be maintained in a lower chamber than in a chamber or chambers thereabove, and so on with respect to each of the chambers upwardly. The aforesaid cutting edges may bc constructed in any suitable manner, such as by means' of Ysections securely fastened respectively to the skin and to the walls or platforms 9, l0, 1l of the shield, as illustrated in Figs. 1` 2 and 4. Since the shield is circular in form.

the lower cutting edge 3b of chamber 3 and the upper cuttin edge 6 of chamber t) are attachedto the s in of the shield, (the cuttin edges 3*, 4, 5' being respectively attac ed to the'floors or platforms 9. 10. ll, :is

g5 above stated), and the cutting edges 4", Ji"

at the sides of the chambers Pand '5 re-. spectively are attached to the' corresponding portions of the skin of the shield (sec Fig. 4).'

Within each working

chamber

3,4. 5, 6 suitable supports'27 and abutments 28 :ire secured adapted respectively to support and `oppose suitable jacks 29, whose plungers or ram`s 30 are ada ted to coperate with suit- 85 able' breastlboartlling or sheeting and

rangers

31, 32. )laced against the corresponding faces26 o the several excavations to temrporarily retain such sheeting in a well nown manner.. Said jaeksmay be hy- 40 draulie jacks 4'controlled in the usual way, (Fig. 2). At 33 are jacks tted within the tail of the shield to coperate therewith and with the tunnel lining rings 2, for shoving the shield forwardly, in any well known manner. I The jacks 33 may be hydraulic jacks operated in a usual n'ianner for shoving tunnel shields. I

While I have illustrated and described a shield constructed with the working

charnbers

3, 4, 5, 6 arranged on different levels, with such chambers projecting respectively farther outwardly from the bottom to the top, somewhat in the nature of a flight of steps, it will be understood that the principle of my invention may be carried out in conjunction with a shield 1n which the an' chambers projectfarther outwardly from the top downwardly than from the bottom upwardly, that is to say, that the upper cutting edge of an upper chamber projects' fartheil outwardly than the upper cutting edge of another chamber or chambers therebelow, and so on correspondingly downwardly, so that the cutting edge of a lower chamber willproject less outwardly than the cutting edge of a chamber or chambers thereabove, as like Steps leading backwardly. ISuch :form of shield might be used for tunneling Nhe're sand is at the top and clay at, the bottom, and the diffusion of the air within the ground will be such -as to overcome the. mingling of air 0f a higher pressure from a chamber on a lower level with air of n. lower pressure in a chamber on a higher level, since the faces 26 of the excavations 75 on the different levels are in different planes and considerable earth intcrvenes between the cutting edge of one chamber and the cutting edge of another chamber.A i

)Vliilc 1 have described a tunnel shield 80 wherein the working

air chan'ibers

3, 4, 5, (iare fixed in relation to the main body of the shield and work together 'as a unit, it will be understood that my improvements also contennilate a shield wherein the air chambers have independent movement with respect to the shield and to one another. Such a construction is illustrated in Figs. 7 to 10. In such construction each of said chambers muy be made with all of its walls separate 90 from the parts of the shield. the rear wall 15 ofeaeh such chamber being secured tb to, bottom and side walls 15'1 thereof, rigidi) connected together in any suitable manner, such as by posts 164'. The cutting edges '3"l 95 'tom vwalls of said chambers rest; iipon,'the

floors. or

platforms

7, 9, 10 and 11.2 'Ehere'ar portions of the cutting edges 3*, 4'i, 5*, 6?, are shown provided with webs 3, 4f, 5u, 63,' respectively overlying or opposing adjaeparts of the

floors

9, 10. 11 and the skid 8 of the shield, the cutting odge 3* having a web 3 opposing the skin at the lower part of the shield (Fig. 7). The interior of each 110 of said movable working chambers may be provided with uprights or abutments to eooperate with the jacks 2t) in ii 'manner before described. Jacks 35 (such as liydiauliev jacks before referred to) may be secured td i-l5 each movable chamber 3, l, 5, 6 in position forcoperation of its plunger or' ram 36, with an abutment 37, such as a'n I-beam, sc-' cu'red within the shield behind the corre,

s ending movable chamber (Figs. 7. 8 and 120 9g, whereby said chambers may be moved forward toward the face of the excavation as required. The jacks 35 of each chamber may be located in a jack circle indicated ai:

18 which may comprise plates 18b and posts 125 18 secured between the corresponding air lock 1S and wall 15 of a workingr chamber,

to prevent- .passage of air around the. locks between the. tunnel and the chambers (Figs.

7 and 8). With the arrangement described, 180

the desired air pressure may be maintained in each of said movable working chambers as in manner before set forth, and when the excavations at the open ends of such chambers have been completed for each step and the sheeting applied and sustained by the jacks 29, the jacks 35 of the corresponding movable `working chambers may he operated to. force 'such chambers forward in proper .10 orderV to the required extent in accordance with the excavation made 4in front thereof, each cliam'ber there\1pon sliding forwardly within the shield. When such movements of `said chambers have been completed, thc en tire s'hield may be moved forwardly byv the operation of v,the jacks 33, the

jacks

29 and 35 then being relieved of pressure as required while the shield moves forwardly along the

chambers

3, 4, 5, 6 to a required position, and the work of excavating in front of said chambers may again proceed, and so on. By means ofthe movable working air chatnbcrsv'withi the shield it will be apparent that `all of the advantages before described may be carried out, and also that one of the movable chambers may be moved forwardly more or less for any given shove ofthe main body of the shield in case rock or other obstruction may have been encountered in front -of such chamber which slowed the V work as compared to the work done in front of the otherchamber or chambers at any given time. r

By `means ofthe arrangements described,

' a5 a plurality of faces or working points of the tunnel excavation are rovided independent of one another, on di erent planes, and the 'height of each working face is less than the lvertical diameter of the shield. While, 40 undersome circumstances, the air pressure in all of the chambers may be the same, and if.desired, the same as within the tall of the shield andthe tunnel, a great advantage o f my'impro'vement is that the air pressure in one working chamber of the shield may be less than the air pressure in one or more other of'such chambers, such as according to the diameter of the shield-and the depth in the earth at which the tunneling is carried on; 1n other words,l compressed air may be used of suitable-pressure for the level at which any of the chambers is located, vand. not as customary in shielddriven tunnels at a comnion ressure for the whole shield and tunnel, an the air pressure in one chamber will be maintained se arate from the air A ressure'in the other c amber or chambers, by reason of the. fact that the face 26 of the excavation 4of a lower chamber projects far- A ther into the round than the face 26 of the excavation o any chamber or'l chambert thereabove, since the air under a higher pressure escapes from a lower chamber mbo 4the ground in front in a lane different from the plane of the face or aces 26 thereabove.

As such air rises nnconfined from a given working chamber of the shield it continually expands to the same pressure as' the ground water at the level it 1s at the moment pass. ing, and since each

air chamber

3, 4, 5, 6 70 may have its compressed air regulated to suit`the water pressure in the ground at its front, it is apparent that such air will. not enter an upper chamber or affect its air pressure, since the pressure of the air escaping from a lower chamber never exceeds the pressure in the ground water holding'it. \Vhle different mr pressures have heretofore been suggested for tunnel shields, it was, so far as I am aware, only in connection with a shield having one common working face for excavation in the earth, hence the air pressure can pass from a chamber on one level to a chamber on another level to affect or raise the air pressure in the lat.- ter without the outside or independent diffusion in the ound of the air from the chambers,l whic my invention provides for. The work of excavation, applying the sheeting or breast-boarding and sustainin them with the jacks 29 may be carried on 1n each, working chamber of the shield under a given pressure,.without-regard to the air ress'ure 1n any other cha'mber, 'whereb w en 'the faces 26 at the different levels o the excaya- 95 tion have all been completed to the required position'for each chamber, the entire shield may be shoved forward a suitable. distance so that similar work for the ,faces at the several levels may continue 'preparatory tn another shove of the shield, and so on successively, It will be noted that during the excavation of aface 26 ofa lower chamber of the shield, the earth above theforward portion of such chamber, into which the face 105 26 of the excavation of the chamber next above is'being made, is sustained .intact by the forwardly rejecting upper portion of the lower cham er, and so on for the chainbers on each level, such earth above 'such 110 forwardly projecting portion of a. lower chamber thereby acting as an obstruction against the flow of com ressed air from`a chamber below into anot er chamber above.

Another important feature of my in\'en- 115 tion is that in cases where the top of the shield is situated only a short distance below the water level, or even above the water level, one or more working chambers may have the doors of their air locks arranged to hold against a higher air pressure in the tunnel than in `a working. chamber, whereby a tunnel may be driven with water in front of the shield in its'lower vpartheld by comres'sed air in its lower working air cham- 125 ers, with the tunnel itself containing compressed air which is prevented from escaping at the top by means of the upper air chamber or chambers either heldin air of lower pressure than that in the tunn or even free air when such chamber is above the water level. A further important feature of my invention is that the use of compressed air may be restricted to the working chambers of the shield. leaving free air in the tunnel.

An advantage of in v invention is that since a lower airlplessure may be maintained in an upper chamber than in a lower chamher, a great saving in the cost of operation may be etl'ected. because of the less cost of maintaining such air pressure and because wages of the workmen are less under low air pressure than under high air pressure, and they can work longer per day under low air pressure than under high air pressure, and with less danger.

lVhile l have illustrated the shield and liningr rings of circular form, the. latter constituting a circular cylinder, it will be understood that a cylinder of any other form may be constructed by the method and apparatus set forth herein` the form of the cross section not being an essential part of my invention.

Having now described my invention what I claim is: y

1. The method of constructing a shield driven tunnel consisting in excavating the ground at the front of a shield in separate chambers` on different levels and producing faces of the excavations in stepped relation in front of the several chambers, advancing the shield toward such faces, and erecting a linin within the tail of the shield after such a vances.

' 2. The'mcthod of constructing a shield driven tunnel consisting in excavating the earth in front of a shield in separate chambers on different levels and producing faces Qf the excavations at the front of such chamliers in different upward planes, maintaining air pressure greater in a lower than in an upper chamber to restrain the flow of water and material from said faces, advancing the shield toward said faces, and erecting a lining within the tail of the shield after such advances.

3. The method of constructing a shield driven tunnel consisting in excavating lthe earth in front of a shield in separate chambers on di li'crent levels in which a chamber on one level is longer in the direction of the tunnel than a chamber on another level, producin r faces of the excavations in the front of suc 1 chambers in different planes forward of one` another, maintaining air pressure ater in a lower than in an upper chamr, advancing the shield bodily?, toward said faces, and erecting lining within the tail of the shield after such advances.

4. A shield for tunneling having separate chambers at its forward end in a unitary structure, the forward end of one chamber extendin farther outwardly than the f0rward en of another chamber.

5. A shield for tunneling having a plurality of workin chambers in a unitary structure at its orward end on different levels, one chamber having a cutting ed located farther forward from the main bog; of the shield than the cutting edge of another chamber.

(l. A shield for tunneling having separate chambers in its forward part having-their forward edges extending beyond another in stepped relation, and an air lock for each chamber, said locks all being adapted to communicate with the space within the tail of the shield.

7. A shield for tunneling having a plurality of horizontal floors therein and transverse walls between the floors providing a plurality of chambers at the forward part of the shield, one floor extendin farther forwardly than another floor, and cutting edges at the forward ends of said floors located in different vertical planes.

8. A shield for tunneling having a plurality of horizontal floors therein, beams se.- sured between said floors, transverse walls secured to said beams and to the skin of the shield providing chambers on different levels within the shield, a chamber onone level extending forwardly from the main body of the shield farther than a chamber on another level, and air locks in said walls.

9. A shield for tunneling having unitary chambers in its forward part extending beyond one another in horizontal stepped relation, jacks in tiers and upright suplmrtstherefor at the forward end of each chamber whereh v the jacks in each chamber may hold sheeting at the face of the excavation in cach chamber.

10. Apparatus for shield driven tunnels comprising 'a shield having unitary air chambers in different levels and different face planes in stepped relation, and means for maintaining air pressure in one chamber independently of the pressure. in anyv other chamber.

Signed at New York city, in the county of New York and State of New York, this 29th day of January, A. D. 1918.

.ioHN F. oRoURKE.-