US3799615A

US3799615A - Tunneling machine having generator means for liquid jets carried on cutter heads

Info

Publication number: US3799615A
Application number: US00266599A
Authority: US
Inventors: N Taylor; H Hilden; C Noren
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1972-06-29
Filing date: 1972-06-29
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26

Abstract

A machine for making tunnels through rock by slitting the tunnel front wall by means of high speed liquid jets which machine comprises a main frame, a carrier movably mounted thereupon, a cutter unit movably mounted on the carrier, whereby the cutter unit is able to cover the tunnel front wall with slots. The cutter unit consists of high speed jet generators which are powered by a non-movable low pressure driving fluid source on the main frame. Impacting devices are provided for breaking down of the remaining parts of the rock intermediate the slots.

Description

United States Patent r191 Taylor et a].

[ TUNNELING MACHINE HAVING GENERATOR MEANS FOR LIQUID JETS CARRIED ON CUTTER HEADS [75] Inventors: Nicholas Simon Hall Taylor,

Saltsjobaden; Hakon Olavi I-lildn; Carl Anders Norn, both of Saltsjo-Boo, all of Sweden [73] Assignee: Atlas Copco Aktiebolag,Nacka,

Sweden [22] Filed: June 29, 1972 [21] Appl. No.: 266,599

[52] US. Cl 299/59, 239/101, 299/31, 299/62, 299/71, 299/81 [51] Int. Cl. E0lg 3/04 [58] Field of Search 299/17, 60,62, 81, 31, 299/71, 59; 239/101, 102; 175/67 [56] References Cited UNITED STATES PATENTS 3,326,607 6/1967 Book 299/17 X Mar. 26, 1974 1,284,398 11/1918 McKinlay .I 299/62 X 3,490,696 1/1970 Cooley 239/102 X 3,521,820 7/1970 Cooley 239/102 X FOREIGN PATENTS OR APPLICATIONS 151,272 1962 U.S.S.R 299/17 176,543 1966 U.S.S.R..... 299/17 Primary Examiner-Ernest R. Purser Attorney, Agent, or Firm-Eric Y. Munson [5 7] ABSTRACT A machine for making tunnels through rock by slitting the tunnel front wall by means of high speed liquid jets which machine comprises a main frame, a carrier movably mounted thereupon, a cutter unit movably mounted on the carrier, whereby the cutter unit is able to cover the tunnel front wall with slots. The cutter unit consists of high speed jet generators which are powered by a non-movable low pressure driving fluid source on the main frame. Impacting devices are provided for breaking down of the remaining parts of the rock intermediate the slots.

9 Claims, 11 Drawing Figures PATENIEDmzs m4 SHEET 6 BF 6 TUNNELING MACHINE HAVING GENERATOR MEANS FOR LIQUID JETS CARRIED ON CUTTER HEADS BACKGROUND OF THE INVENTION This invention relates to a machine for making tunnels and drifts through rock which machine disinte- Known machines of this type disintegrate rock by making slots in the tunnel front wall by means of mechanical cutters. There are serious problems involved in using such machines partly because of the fact that it is a very hard wear of the cutters and partly because of the fact that very great feeding forces are required. These features are disadvantageous by themselves and have also a limiting effect on the machine power that is appliable to the rock surface.

This invention relates to a tunneling machine by which the above mentioned problems are solved. By a machine according to the invention the tunnel front wall is cut into slits or fissures by means of eroding high speed liquid jets. In such a machine there is no slitting BRIEF DESCRIPTION OF THE DRAWINGS A machine according to the invention will hereinafter. be described with'refererices to the drawings on which FIG. I is a side elevation of the machine according tothe invention at drifting of a tunnel. FIG. 2 is a horizontal view of the machine shown in FIG. 1. FIG. 3 is a schematical partly broken side elevation in a larger scale of the machine shown in FIGS. 1 and 2. FIG. 4 shows the front wall of a tunnel and the working means of the machine according to FIG. 3 and shows schematically how the machine according to FIG. 3 works the front wall of a tunnel. FIG. 5 is a partly exploded horizontal view of the working means of the machine according to FIG. 3 and the front wall of a tunnel showing the rockdisintegrating principle of this machine. FIG.

6 is a perspective view'of a cutter head according to an-' otherembodiment of the invention. FIG. 7 shows the same cutter head in another view which is a cut along line VIIVII in FIG. 6. FIGS. 8 and 9 show in two different views another machine according to the invention. FIG. 8 is a side elevation of the machine showing the cutter unit in an erected position. FIG. 9 is a top elevation of the same machine showing the cutter unit in a horizontal but lateral position. FIG. 10 shows in larger scale the front part of the machine according to FIG. 9. FIG. 11 is a cross section of a tunnel made by the machine according to FIGS. 8-10.

SUMMARY OF THE INVENTION The machine shown in FIGS. 1-3 comprises a movable main frame I which is connected to a tail 3 by means of fulcrum 2. The tail 3 is guided in a guide box 4 which is arranged to be braced relative to the tunnel walls. The bracing of the guide box 4 is accomplished by extending two

hydraulic jacks

5 and 6 into contact with the tunnel walls. Between the guide box 4 and the main frame 1 there are provided hydraulic jacks 7 and 8 by means of which steering of the machine in the tunnel is accomplished as well as stepwise feeding of the main frame relative to the guide box 4. i

During the advancement of the machine towards the tunnel front wall the guide box 4 is braced against the tunnel walls by means of the

jacks

5 and 6 whereupon the main frame 1 is forced forwards by the hydraulic jacks 7 and S. As these jacks have obtained their full length the guiding box is released from the tunnel walls by retracting the

jacks

5 and 6 whereupon the guide box 4 is pulled forwards by retracting the jacks 7 and 8. Then, the guide box 4 is again braced against the tunnel walls and another advance movement of the main frame can be performed.

In steering the machine the length of the hydraulic jacks 7 and 8 are adjusted individually so as to make 7 the tail 3 form an angle to the main frame 1. (As indicated in dotted lines.) Then, the tail 3 is locked in this position relative to main frame by means of a mechanical locking device. (Not shown). Now, the main frame can be advanced along a curved path by means of the hydraulic jacks 7 and 8. i

- At the forward end the machine rests in a guide shoe 9 and is supported by adjustable support means 11. By means of the support means 11, the machine is kept in level position while the guide box 4 is released from the tunnel walls.

Moreover, the machine is equipped with a conveyer 12 and a loading device 13 for collecting and transportation of disintegrated rock.

At the forward end of the main frame 1 there is journalled a carrier 14 (see especially FIG. 3) which is rotated by-a motor 15 via a gear 16. Upon the carrier 14 there is rotatably mounted a cutter unit 17 and mounting head 18 for supporting mechanical breaking means. The cutter unit 17- and the mounting head 18 are rotative about axes which are parallei to the rotation axis of the carrier 14 and when rotated together with the carrier they describe planetary movements. The cutter unit 17 and the mounting head 18 are rotated by a common motor 19 via a worm gear 20 and a spur gear 21. The worm gear 20 and the spur gear 21 have in common an intermediate wheel 22 which is journalled coaxially with the carrier 14. As the motor 19 is stationary the rotation speed of the cutter unit 17 and the mounting head 18 relative to the carrier 14 is defined by the difference in speed between thecarrier 14 and the intermediate wheel 22.

The cutter unit 17 comprises a high pressure generator consisting of a housing in which a doubleacting differential piston 23 is reciprocable. The piston 23 consists of two identical high pressure plungers 24a,b and an intermediate wider low pressure part 25. The former work in corresponding high pressure chambers in the housing to which are connected water supply conduit 26a,b, water outlet conduits 28a,b and jet nozzles 27a,b. The intermediate low pressure part 25 of the piston 23 works in adrive chamber 29 to which is connected conduits 3la,b for supplying and draining of hydraulic fluid. In the high pressure chambers there is obtained a pressure of about 3,000 to 6,000 atmospheres. The magnitude of the pressure obtained is due to the pressure of the driving hydraulic fluid as well as the relationship between the low pressure and high pressure areas of the piston 23. j

The high pressure chambers of the high pressure generator are continuously supplied with water by a pump 32 through a conduit 33 in the carrier 14 and check valves 34a,b in the cutter unit 17.. The drive chamber 29 is supplied with hydraulic fluid by a pump 35 through a control valve 36 and the conduits 3la,b. The

pump 35 is connected to a hydraulic fluid tank 38 by means of a conduit 37 and delivers hydraulic fluid at the pressure of 150-350 atmospheres. The pump 32 delivers water at a pressure of about 30 atmospheres.

The purpose of the control valve 36 is to alternately supply hydraulic fluid to the two sides of the drive chamber 29 for reciprocating of the piston 33. The control valve 36 is activated by an electric circuit which comprises a source of current 39, a contact means 40 and an electromagnetic coil 41. The contact means is mounted on the carrier 14 and is activated by a cam 42 on the cutter unit 17. The control valve 36 is shiftable just in one direction by means of the electric circuit and is biased in the other direction by a spring 43. The control valve 36 is shifted by means of the electric coil against the biasing force of the spring 43 as the cam 42 acts upon the contact means 40. In order to synchronize the reciprocation of the piston 23 relative to the rotation of the cutter unit 17 the cam 42 has to be of such a length that it acts upon the contact means at intervals separated by 180. By such an arrangement water jets are produced under a certain, predetermined angle interval of the rotation of the cutter unit 17 relative to the carrier 14.

Of course, the control valve can be shifted in other ways, for example hydraulically. The electric control circuit is then exchanged by a hydraulic circuit.

The mounting head 18 carries two impacting devices 44a,b which are located in parallel planes and which are directed in angles forwardly towards the front wall of the tunnel. Each of the impacting devices 44a,b consists of a cylinder 50, a hammer piston 45 and an impacting tool 46. The impacting devices 44a,b are actuated by hydraulic fluid delivered by a pump 47 through a conduit 48 in the carrier and control valves 49a,b. The pressure fluid may consist of compressed air or hydraulic oil and the pump 47 is consequently a compressor or a hydraulic pump.

As illustrated in FIGS. 4 and 5, disintegration of rock at this machine is accomplished by cutting cracks or fissures in the tunnel front wall and by breaking down of the remaining parts of the rock intermediate said cracks by means of the impacting devices 44a,b. As they are being cut during rotation of the cutter unit 17, the fissures are curved, having one end at the periphery of the tunnel and the other end near tunnel center. The slits are cut by eroding high speed water jets which are produced by the high pressure generator during a predetermined angle interval of the rotation of the cutter unit 17 relative to the carrier 14. The operating cycle of the piston 23 is for this purpose synchronized to the rotation of the cutter unit 17 relative to the carrier 14.

' This is accomplished by the cam controlled electric circult including the operating valve 36 so that the piston 23 always will make a work stroke within one and the same angle interval. As the high pressure generator is double-acting there are out two slots during each round of the cutter unit 17.

The operation of the machine is the following,

The guide box 4 is braced against the tunnel walls by the

hydraulic jacks

5 and 6 and the tail 3 is adjusted and locked in a predetermined angle relative to the main frame. Then the latter is pushed forward by means of the hydraulic jacks 7 and 8 along a predetermined path. Simultaneously, the carrier 14' is rotated by means of the motor 15 and the cutter unit 17 and the mounting head 18 are rotated by the motor 19. Now, the high pressure chambers of the high pressure generator are supplied with water by the pump 32.

The operation of the cutter unit 17 is hereinafter described with references to FIGS. 3 and 5.

In the position shown in FIG. 3 the piston 23 has just reached its upper end position and has during its upward stroke produced a water jet through the nozzle 27a. In this position the cam 42 acts upon the contact means 40 so that the control circuit is closed and the coil 41 has moved the control valve 36 to open the conduit 31b. Hydraulic fluid is fed from the pump 35 through the conduit 31b into the lower part of the drive chamber 29.

By further rotation of the cutter unit 17, the action of the cam 42 upon the contact means 40 will be interrupted so that the control circuit is broken and the shifting force of the coil 41 is interrupted. Thus, the biasing force of the spring 43 will move the control valve 36 to the opposite position wherein hydraulic fluid is conducted to the upper part of the drive chamber 29 through the conduit 31a. Meanwhile, the pump 32 has filled the lower high pressure chamber with water, and, as the piston starts on its downward stroke, the check valve 34b is closed and water is forced out through the conduit 28b and the jet nozzle 27b at a very high velocity. The water jet thereby obtained has a duration of almost half a revolution of the cutter unit rotation or more precisely until the cam 42 ones again acts upon the contact means 40, closing the control circuit and causing shifting of the control valve 36. As the control valve 36 is shifted, the piston 23 changes direction and the cycle is repeated in the opposite high pressure chamber. Yet, the cutter unit 17 has turned half a revolution and a water jet is produced within the same angle interval relative to the carrier as the previous situation.

As the carrier 14 has turned half a revolution, the impacting devices 44a,b will be able to break loose the parts of the rock which have been undermined by the cuts. The parts of the rock which have been broken loose fall down to the tunnel floor. In order to protect the cutter unit 17 from being damaged by the heap of crumbled stones on the tunnel floor, the carrier 14 is provided with a scrape 51 (see FIGS. 1 and 2). This scraper 51'(see FIGS. 1 and 2) is mounted on the carrier 14 so as to be ahead of the cutter unit 17 as the carrier 14 rotates to shove aside the stones so that they can be reached by the loading device 13 and so that the cutter unit 17 can freely pass.

The relationship between the depth of the slots and the distance between the slots should be at least l-l in order to make it possible for the impacting devices to break down the remaining parts of the rock intermediate the cuts. That means that the rotation speed of the carrier 14 has to be adapted carefully to the depth of the cuts that the water jets can make, so that the distances between the cuts will not exceed their depths.

The advancing speed of the machine must be adapted to the depth of the cuts in the tunnel direction so that the machine is moved forwards a distance equal thereto for each revolution of the carrier 14. To facilitate the breaking down of the rock the cut may be made at an angle relative to the tunnel direction.

The revolution speed of the cutter unit 17 relative to the carrier 14 as well as the size of the jet nozzles 27a,b

can be varied individually to adjust the cuttingaction of water jet to the physical properties of the rock being worked.

In the FIGS. 6 and 7 there is shown a cutter unit of a different type for use in a machine according to the invention. The difference between this cutter unit and the above described cutter unit is that the previously described'high pressure generator consisted of a doubl'e-acting pressure implifier of the differential piston type and cutter unit hereinafter described consists of four single-acting high pressure generators 61a,b of a free-piston type for producing high pressure water jets. These jet generators are mounted on a hub 62 and are directed forwards toward the tunnel front wall forming acute angleswith the rotation axis of the cutter unit. Each of these jet generators comprises a housing63, a piston 64, a control valve 65 of the same type as in the above described machine and the jet nozzle 66. The piston 64 has a wider part 67 which works in a drive chamber 68 which is supplied with driving fluid through the control valve 65 for reciprocating the piston 64 in the housing 63. The forward partof the piston 64 works in a water chamber 69 which communicates with the jet nozzle 66. The water chamber 69 is formed with a high pressure chamber 70 at its forward end which communicates directly with the jet nozzle 66. The forward part of the piston 64 fits snugly in the high pressure chamber 70. Each of the water jet generators 6la-d are also provided with a water inlet 71 to which is connected a check valve 72 and an accumulator 73.

The operating order of the jet generators is as follows,

As in the previously described embodiment, the control valve 65 is shifted by electrical means (or otherwise) during the rotation of the cutter unit so that drivingrfluid will alternately be supplied to the different parts of the drive chamber 68 to make the piston 64 reciprocate therein. During a working stroke the piston 64 is accelerated forwardly whereas the pressure in the water chamber 69 rises. Thereby, water flows out from the chamber partly through the inlet 71 and partly through the jet nozzle 66. As the check valve72 prevents water from flowing back into the supply conduit and as the size of the jet nozzle 66 is very small the main part of the surplus water will be forced into the accumulator .73.. This continues until the piston 64 reaches the high pressure chamber 70, where the latter closes and the water pressure therein rises to a very high level. By reason of this high pressure the water is discharged through the jet nozzle 66 at a very high velocity. During the return stroke of the piston, the water chamber 69 and its high pressure part 70 is filled with water, at first from the accumulator 73 and thereafter, I

when the pressure therein has decreased, water enters through the supply conduit. Another working stroke may now be initiated. This cycle is repeated in LOGO-6,000 double-strokes per minute and is characterized by the short time interval during which the high pressure jet lasts. Thus the duration of the water jet is short compared to the time period of the whole cycle, such as one-tenth thereof. 1

In FIGS. 8-10 there is shown another embodiment of the invention which comprises a main frame 101 and a trailing chassis 102. The main frame supports a carrier 103 which is pivotable about a horisontal axle 104. On the carrier 103 there is mounted a cutter unit 105 which consists of two high speed

water jet generators

106 and 107. These generators consist'of single-acting, differential piston pressure amplifiers provided with

jet nozzles

108 and 109. (The cutter units are not described in detail.)

As distinguished from the previously described embodiment of the invention, this machine is adapted for production of non-circular tunnels (See FIG. 11). The jet nozzles of the cutter unit of this machine is movable in substantially horizontal and vertical planes and is intended to cut a number of transverse slits in the tunnel front wall. As in the previously described embodiment, this machine is preferably provided with mechanical means for breaking down the remaining parts of the rock which has been undermined by the cuts. In order to avoid making the figures indistinct these breaking means are omitted in the drawings.

The main frame 101 rests upon four shoes 110 which are vertically adjustable by means of hydraulic jacks 111. The main frame 101 is also provided with four horizontally arranged hydraulic jacks 112 by means of which it can be braced against to the tunnel walls.

The main frame 101 and the trailing chassis 102 are interconnected by means of two

hydraulic cylinders

113 and 114 the purpose of which is to accomplish the feeding and the steering of the machine. The chassis 102 is provided with wheels 115 and horizontal jacks 116 for movement and embracement in the tunnel re spectively. On the trailing chassis 102 there are also disposed a hydraulic pump 117, an'electric motor 118 for driving the pump 117, an oil reservoir 119, a water pump 120 and an electric motor 121 for driving the pump 120. Moreover, the trailing chassis 102 is provided with a control box 122 comprising control means for the machine, an electric hoist block 123 suspended on a rail 124. The chassis also includes an operators platform 126.

Referring to FIG. 10 in particular, the cutter unit arrangement will be more closely described. The cutter unit 105 is swingably mounted on the carrier 103 which in turn is pivotable about a horizontal axle 104 which is perpendicular to the tunnel axis. By pivoting the carrier 103 the forward'ends of the high speed water jet generators are raised or lowered. The swing axisof the cutter unit 105 is perpendicular to the pivot axle of the carrier 103.

For accomplishing of the pivoting movement of the carrier 103 the pivot axle 104 is revolvable by means of a motor 127 and gear 128. The cutter unit 105 is swingable by means of a hydraulic cylinder 129. Bydraulic pressure fluid for driving the jet generators is supplied to the cutter unit 105 through the pivoting axle 104 of the carrier 103 which, for that purpose is provided with

swivel joints

131 and 132. The singleacting pressure amplifiers which constitute the

jet generators

106 and 107 are inter-connected hydraulically by means of a conduit 133 and a distributing valve 134.

The operation of the machine is following,

The cutter unit 105 is supplied with hydraulic driving fluid from the pump 117 via the swivel 131, the axle 104 of the carrier 103 and the. distributing valve 134. Depending upon the position of the distributing valve 134, the right jet generator 107 or the left jet generator 106, will be fed withdriving fluid. (The distributing valve 134 is shifted by any suitable means, for instance a hydraulic control circuit.)

In one position, the distributing valve 134 feeds the right jet generator 107 as indicated in FIG. 10. The pressure amplifying differential piston of the generator 107 is forced forwards, whereby a water jet is produced through the nozzle 109. Simultaneously, the hydraulic fluid which is situated in front of the low-pressure part of the differential piston is pressed out through the conduit 133. This conduit is connected to the front side of the differential piston of the left jet generator 106, whereby the conducted hydraulic fluid causes the left jet generator to perform a return stroke.

During the return stroke of the left pressure amplifier, hydraulic fluid flows from its rear end and is returned to the reservoir 119 via the valve 134, the axle 104 and the swivel joint 132.

As a water jet is produced by the right jet generator 107, the cutter unit 105 is swung to the left, whereby a slit is cut from the right hand wall of the tunnel to the middle of it. The swinging velocity of the cutter unit 105 is adjusted to the duration of the jet, so that the working stroke of the jet generator is completed at the same time as the swinging movement is completed.

Now, the distributing valve 134 is shifted, whereby the left jet generator 106 makes a working stroke. At the same time the cutter unit 105 is swung to the right by means of the cylinder 129 and a slit is cut from the left hand wall of the tunnel to the middle of it. A complete slot transverse the tunnel front wall is now cut. The cycle is repeated after the

jet nozzles

108 and 109 have been raised or lowered by pivoting the carrier 103. Such a pivoting is accomplished by activating the motor 127 which turns the pivot axle 124 of the carrier 103 via the gear 128.

As the tunnel front wall is covered with slits and the remaining parts of the rock have been broken down, the machine has to be advanced to a new cutting position. This is accomplished by releasing the chassis 102 from the tunnel walls by retraction of the jacks 116 and by retraction of the

hydraulic cylinders

113 and 114, whereby the chassis 102 is pulled forwards. When the

cylinders

113 and 114 are fully retracted, the chassis is again braced against the tunnel walls by extension of the jacks 116. Thereupon, the bracing jacks 112 of the main frame 101 are released and the

cylinders

113 and 114 are re-extended, whereby the main frame 101 is advanced to a new cutting position where it is braced to the tunnel walls by re-extension of the jacks 112. Now, the machine is ready for cutting another series of slits in the tunnel front wall.

Steering of the machine horizontally into curved paths is accomplished by individual manoeuvring of the

cylinders

113 and 1 14 so that the main frame 101 is disposed at an angle relative to the chassis 102. This angle-setting is maintained during the stepwise advancement of the machine.

Vertical steering of the machine is accomplished by manoeuvring of the jacks 1 11. The machine is also prevented from getting into a helical path by adjustment of the jacks 111.

The invention is not limited to the described and shown embodiment but can be freely varied within the scope of the claims.

What we claim is:

1. A tunneling machine, using high velocity fluid jets for making slits in the tunnel front wall, comprising a main frame movable on the tunnel floor, a carrier rotatably mounted on said main frame for rotation about an axis coaxial with the tunnel axis, a cutter unit engaging said carrier for rotation about an axis spaced from and parallel to the tunnel axis, said cutter unit comprising at least one high pressure generator connected to a jet nozzle at one end and to a power source at the other end, said power source being controlled to supply drive power at predetermined intervals to said generator, a mounting head rotatably engaging said carrier for rotation about a separate axis spaced from and parallel to the tunnel axis and supporting at least one mechanical breaking means for breaking down the undermined portion of the tunnel front wall between the slits produced by the fluid jets and motor means for rotating said carrier and separate motor means common to said cutter unit and said mounting head for moving the same in a planetary path about said carrier.

2. A tunneling machine according to claim 1, characterized in that each high pressure jet generator comprises a differential piston type pressure amplifier.

3. A tunneling machine according to claim 2, characterized by one double-acting differential piston type pressure amplifier arranged to alternately serve two jet nozzles.

4. A tunneling machine according to claim 1, characterized in that said high pressure jet generator of each cutter head comprises a free-piston type pressure jet producing device.

5. A tunneling machine, using high velocity fluid jets for making slits in the tunnel front wall, comprising a main frame movable on the tunnel floor a power source disposed on said main frame, a carrier pivotably mounted on the main frame for pivoting about a horizontal axis perpendicular to the tunnel axis, two cutter units arranged to swing together about an axis perpendicular to the pivot axis of said carrier, each of said two cutter units comprising a high pressure generator and a jet nozzle, said high pressure generator being energized by said power source to supply active power alternately to said generators.

6. A tunneling machine according to claim 5, characterized in that the cutter units are arranged to cut substantially horizontal slits in the tunnel front wall by swinging relative to the carrier and that one of the cutter units covers one half of the front wall, whereas the other cutter unit covers the other half.

7. A tunneling machine according to claim 6, characterized in that the distance between the jet nozzles are substantially equal to half the tunnel width and that each jet nozzle is arranged to be moved over a distance substantially equal to half the tunnel width only.

8. A tunneling machine according to claim 5, characterized in that said high pressure jet generator of each cutter unit consists of a differential piston type pressure amplifier.

9. A tunneling machine according to claim 5, characterized in that said pressure generator of each cutter unit consists of a free-piston type pressure jet producing device.

Claims

7. A tunneling machine according to claim 6, characterized in that the distance between the jet nozzles are substantially equal to half the tunnel width and that each jet nozzle is arranged to be moved over a distance substantially equal to half the tunnel width only. 8. A tunneling machine according to claim 5, characterized in that said high pressure jet generator of each cutter unit consists of a differential piston type pressure amplifier.