EP0985082B1 - Tunnel-boring machine - Google Patents

Abstract

The tunnel rock drill (100) for driving a tunnel bore optionally in open or shielded mode comprises a shield tail (33), which is connected to the drill head (10) and which covers optionally the bore wall over a defined length; a bracing device (20), which can be optionally fixed in the tunnel bore; at least one optionally activaatable advancement device (25), which, on the one hand, rests on the bracing device (20) and , on the other hand, acts on the drill head (10); and an optionally activatable force generator (35), which has a variable length and which, on the one hand, rests on a tubbing support (32) and, on the other hand, acts on the drill head (10). To introduce the advancement forces into the drill head in open mode, there is an inner kelly (16), which can be moved in the direction of boring in relation to the bracing device (20) and to which the advancement generator (25) is hinged and whose breast-sided end bears the drill head (10).

Description

The invention relates to a tunnel boring machine of the type corresponding to the preamble of claim 1 and also relates to a method according to claim 15.

• a) Beim sogenannten offenen Verfahren befindet sich hinter dem Bohrkopf ein freier Raum, d.h. die Bohrungswandung ist nicht durch irgendwelche Vorrichtungsbauteile wie Schutzschilde o.ä. überdeckt. Während des Bohrvorganges können in diesem Freiraum wahlweise Ausbausysteme, wie beispielsweise Stahlringe, Ankerbohreinrichtungen und/oder Spritzbetonauskleidungen, eingebracht werden. In dem Bereich, in dem die gewünschten Ausbausysteme bereits installiert sind, ist eine Verspannvorrichtung vorhanden, welche etwa radial gegen die Tunnelaußenfläche verspannt werden kann, um so die üblicherweise über eine Vielzahl von Vorschubzylindern von dem Bohrkopf übertragenen Reaktionskräfte in das die Tunnelbohrung begrenzende Gestein abzuleiten.
  Da beim offenen Betrieb unmittelbar hinter dem Bohrkopf keinerlei Überdeckung bzw. Unterstützung der Tunnelbohrung vorhanden ist, eignet sich dieses Verfahren lediglich zum Einbringen von Tunnelbohrungen in standfesten Formationen, bei dem die Gefahr eines Kollabierens des noch nicht ausgebauten Abschnitts der Tunnelbohrung nicht besteht.
• b) Beim sogenannten Schildbetrieb ist im Anschluß an einen meist hinter dem rotierenden Teil des Bohrkopfes vorgesehenen Bohrkopfschild ein sogenannter Schildschwanz vorgesehen, dessen Außendurchmesser - je nach Konvergenzneigung des Gesteins - etwas kleiner als der wirksame Außendurchmesser des Bohrkopfes oder auch nach hinten konisch zulaufend gewählt ist. Der Schildschwanz dient der Abstützung der unmittelbar an den Bohrkopfraum angrenzenden Tunnelwandung, um so ein Kollabieren derselben zu verhindern.

When drilling a tunnel, it is known to alternate between the following two processes, depending on the nature of the soil:

• a) In the so-called open method, there is a free space behind the drill head, ie the bore wall is not covered by any device components such as protective shields or the like. covered. During the drilling process, optional expansion systems such as steel rings, anchor drilling devices and / or shotcrete linings can be installed in this free space. In the area in which the desired expansion systems are already installed, there is a bracing device that can be braced, for example, radially against the outer surface of the tunnel, in order to divert the reaction forces, which are usually transmitted from the drill head via a large number of feed cylinders, into the rock delimiting the tunnel bore.
  Since there is no overlap or support of the tunnel bore immediately behind the drill head during open operation, this method is only suitable for drilling tunnel bores in stable formations, where there is no risk of the section of the tunnel bore which has not yet been removed from collapsing.
• b) In so-called shield operation, a so-called shield tail is provided in connection with a drill head shield usually provided behind the rotating part of the drill head, the outer diameter of which - depending on the tendency of the rock to converge - is selected to be somewhat smaller than the effective outer diameter of the drill head or also tapered towards the rear. The shield tail serves to support the tunnel wall directly adjacent to the drill head space, in order to prevent the same from collapsing.

During the drilling process, a segmental expansion is carried out in the shield operation within the area covered by the shield tail at a distance from the inner circumferential surface of the shield tail, in which mostly individual, prefabricated concrete components are put together with suitable aids to form a tubular expansion covering the entire tunnel wall. Since the shield tail and the segmental lining always overlap by a certain amount with regard to the longitudinal extent of the tunnel bore, collapse of the tunnel wall is impossible. The shield operation is therefore particularly suitable for the drilling of tunnel bores in soft rock or less stable formations.

During shield operation, tunneling is carried out using so-called tubbing cylinders, which are provided between the (non-rotated) drill head shield and the front face of the tubbing extension with respect to the longitudinal extent of the bore, and thus propulsion and rotational reaction forces into the tubbing expansion or at the start of shield operation, ie if there is no tubbing expansion yet, into a steel ring that is radially braced against the mountains.

Especially in the case of longer tunnel bores, these often extend through different rock formations, which means that the two methods have to be used alternately. For this purpose it is known, depending on the respective rock formations, to transport and to erect various devices for the working face suitable for the application of the respective method. This procedure is disadvantageous since the required assembly and dismantling measures for both devices require considerable effort and thus significantly increase the production costs for a bore.

From the company Wirth, Erkelenz, a generic tunnel boring machine is known from the brochure "Telescopic shield machine for Lesotho project Ø 5.39 m, which is suitable for use in hard rock as well as in soft rock formations, that is, either using the open or the shield method This device comprises a shield tail which always covers the tunnel space immediately behind the drill head shield and which consists of two telescopically interlocking shield tail segments, the telescopic overlap of the shield tail segments taking place over a length which is greater than the maximum stroke of a plurality of feed cylinders provided within the shield tail , so that regardless of their operating state, the bore wall in this area is completely covered by the shield tail.

The feed cylinders extend between the rear wall of the drill head shield and a bracing device which - as already explained above - can be braced radially against the borehole wall to absorb drilling reaction forces, provided the properties of the rock formation permit this.

To use the device in the shield mode, tubbing cylinders are provided on the bracing device, pointing backwards with respect to the direction of the bore and distributed over the circumference of the bore, which are suitable for fitting a tubbing expansion that has already been carried out or has been used in the manner described above Support the steel ring and thus transfer drilling reaction forces into the tubbing extension when the tensioning device is released.

If this tunnel boring machine is used in hard rock, the tubbing cylinders are out of operation, whereas the bracing device for absorbing the reaction forces is braced against the tunnel wall. The feed of the drill head takes place by extending the feed cylinders, the feed being accompanied by the extension of the telescopic shield tail. If the tunnel boring driven in this way and by corresponding repositioning of the tensioning device encounters soft rock information, the support device is deactivated and the drilling reaction forces are derived via the tubbing cylinders in the tubbing expansion in the manner already described.

With this device, it is possible to advance a tunnel bore even in changing rock formations without the need for time-consuming, complete conversion measures on the tunnel boring machine, but it is disadvantageous that the area of the tunnel bore adjoining the drill head space is continuously removed due to the telescopic shield tail extending during the drilling process a considerable length is covered by the shield tail. In this way, it is not possible, on the one hand, to attach desired extension systems to the tunnel wall directly after the drill head space in the case of hard rock, on the other hand, changes in direction are impeded by the length of the shield tail. Furthermore, due to its telescopic design, the shield tail has a shoulder into the material that collapses from the tunnel jacket penetrate and can obstruct or even block the displacement of the shield and thus the feed. This is particularly problematic when a rock tail tapering towards the rear is required due to rock formations that tend to converge.

The invention has for its object to further develop a generic tunnel boring machine, which is suitable both for open operation and for shield operation and thus for driving tunnel boring both in hard rock and in soft rock formations, in such a way that these disadvantages are improved.

This object is achieved by the tunnel boring machine shown in claim 1.

Characterized in that the tunnel boring machine comprises an inner kelly which is displaceable with respect to the tensioning device and which bears the drill head at its end on the face side and the feed generators are articulated to the inner kelly, the bore region directly adjoining the drill head space is no longer covered by the feed generators, so that already therefore the bore wall is more accessible. Furthermore, this configuration makes it possible to arrange the fixed parts of the feed generators mounted on the bracing device in such a way that only the movable components of the feed generators protrude on the face side. With this measure, a telescopic design of the shield tail can be dispensed with and the length can be reduced compared to the generic device. As a result, changes in direction of the tunnel bore can be made more easily.

An embodiment according to claim 2 is particularly advantageous, in which the shield tail is designed in such a way that the region of the bore wall which it covers can be selectively released. This measure allows the length of the region of the bore wall which is always covered to be reduced even further, on the one hand making it even denser extension systems to be installed behind the working face in hard rock can be built, on the other hand even tighter changes of direction can be achieved. In terms of construction, the configuration according to claim 2 can be accomplished, for example, in that the shield tail consists of a plurality of pipe segments which are divided in the longitudinal direction and are either attached to the drill head shield or are hinged to the center of the bore.

The inner kelly is preferably mounted in the tensioning device itself, namely longitudinally displaceable, but non-rotatable. Through these measures, the inner kelly is always essentially in the center of the hole, so that there is always a maximum free space for attaching extension systems to the wall of the hole; on the other hand, momentary reaction forces can also be released via the inner kelly and the bracing device into the rock formation forming the hole wall.

A drive block is then preferably provided between the drill head and the inner bowl, with which the drill head can be set in rotation. The drive block is designed such that the drive reaction moments are introduced directly into the inner kelly.

In a particularly preferred embodiment of the tunnel boring machine according to the invention, the drilling head is arranged in an articulated manner on the inner beam, in such a way that, during operation, the axis of rotation of the drilling head can be pivoted with respect to the longitudinal axis of the inner beam. As a result of this measure, in particular in connection with an embodiment according to claim 6, in which the inner bracket is mounted in the tensioning device so as to be pivotable about any axis perpendicular to its longitudinal axis, and the possibility of minimizing the longitudinal extent of the drill head by the removable shield tail is particularly narrow Change of direction of the tunnel drilling achievable.

The change in direction of the drill head, i.e. the pivoting of its axis of rotation relative to the longitudinal axis of the bore is preferably carried out according to claim 7 with the aid of a variable-length control device which is connected on the one hand to a part of the drill head or the drive block which is fixed with respect to the rotation, and on the other hand to the inner bowl.

The mounting of the drill head on the inner bowl can be relieved if, according to claim 8, the control device is designed in such a way that it can equally serve to transmit the feed reaction forces from the drill head to the inner bowl and vice versa.

In a preferred embodiment of the tunnel boring machine according to the invention, the control device, the feed generators and / or the force generators are formed by hydraulically actuated piston / cylinder units.

The articulated connections between the drill head and inner cell and / or between the inner cell and bracing device are preferably formed by ball joints.

The drill head is preferably driven electrically and / or hydraulically.

A preferred embodiment of the tunnel boring machine according to claim 12 comprises integrated means for the simultaneous attachment of bore supports and / or casing during the boring process, which are designed to be stationary with respect to the bore wall. As a result of this measure, the time required to advance a bore stroke can be used to attach extension systems.

Preferably, the means for attaching bore supports and / or casing between the drill head and the bracing device are arranged according to claim 13, so that the expansion systems can be installed directly after the drill head space.

The drilling material detached from the working face is preferably transported away during the drilling process with the aid of a drilling material conveyor running through the inner bowl. This measure in turn does not restrict the free space required behind the drill head for tunnel expansion (claim 14).

The procedural aspect of the invention is given in claim 15.

In the drawing, an embodiment of the invention is shown.

• Fig. 1 einen durch die Tunnelachse gehenden Längsschnitt durch den vorderen Teil einer in dem Tunnel nach dem Schildverfahren arbeitenden Tunnelbohrmaschine beim Nachsetzen der Verspannvorrichtung;
• Fig. 2 dieselbe Tunnelbohrmaschine in einer entsprechenden Ansicht bei Fortschreiten der Tunnelbohrung in einer Weichgesteinformation sowie
• Fig. 3 dieselbe Tunnelbohrmaschine in der offenen Betriebsweise.

Show it:

• 1 shows a longitudinal section through the tunnel axis through the front part of a tunnel boring machine working in the tunnel according to the shield method when the tensioning device is being adjusted;
• Fig. 2 shows the same tunnel boring machine in a corresponding view as the tunnel drilling progresses in a soft-gesture information as well
• Fig. 3 the same tunnel boring machine in the open mode.

The tunnel boring machine, designated as a whole by 100, serves to drive up a tunnel 1 in the floor 2. The components which are important for the invention are shown in the drawing.

If in the following we speak of "in front", then we mean the part of the tunnel boring machine 100 shown on the left in the drawing facing the working face 3; "Rear" therefore designates the side of the tunnel boring machine 100 facing away from the working face 3 and shown on the right in the drawing.

The front part of the tunnel boring machine 100 adjacent to the working face 3 has a central axis M which essentially coincides with the central axis of the tunnel 1, the latter not having to be straight, but can also run in an arc. The inner kelly can also be offset from the tunnel axis.

The tunnel boring machine 100 comprises a boring head designated as a whole as 10, which essentially comprises a rotating drilling tool carrier 11, which serves to break down the rock standing against the working face, a fixed boring head shield 12 adjoining this to the rear, which bores the actual boring head space 13 from the separates already opened tunnel, as well as a drive block 14, which - usually operated electrically or hydraulically - sets the drilling tool carrier 11 in rotation. The drilling head 10 and the components forming the drive head are those of a conventional type belonging to the prior art, so that they will not be discussed in detail here.

The drill head 10 and the drive block 14 are mounted on a bearing 15 on a rearwardly extending inner bracket 16. The bearing 15 is designed such that the drill head 10 and the drive block 14 can be pivoted such that the central axis of the drill head M 'is tilted to the central axis M during the drilling operation by a certain angle. This configuration makes it possible to change the direction of the tunnel bore. Furthermore, the bearing 15 comprises torque transmission elements 17, so that reaction torques caused by the drive of the drilling tool carrier 11 are derived via the bearing 15 into the inner wall 16.

The transmission of feed forces and the swiveling of the drill head 10 is served by a control device 18, which acts on the one hand on the inner wall 16, on the other hand on the drill head shield 12 or on a fixed part of the drive block 14. In the exemplary embodiment of the tunnel boring machine according to the invention shown in FIG. 1, the control device 18 is formed by a piston / cylinder unit 19. Of course, it is also possible to use other or further variable-length force generators distributed over the circumference of the inner shell 16 as the control device.

The inner kelly 16 extends rearward through a bracing device 20 which comprises a plurality of piston / cylinder units 21 which are equipped with bracing claws 22 at their radially outer ends. Since the operating state of the tunnel boring machine 100 according to the invention, the repositioning of the tensioning device is shown in FIG. 1, the piston / cylinder units 21 are in the retracted state, so that the tensioning claws 22 do not rest against the tunnel wall, but rather the device rests on the rear support 27.

The bearing of the inner kelly 16 in the clamping device 20 is a bearing 23, which is designed such that the inner kelly is pivotable relative to the clamping device 20 and displaceable in the longitudinal direction, but not rotatable, the latter property in turn being accomplished by torque transmission elements 24 provided in the bearing 23 becomes.

In the embodiment shown in the drawing, the feed device 20 accommodates two feed generators 25, which are designed as piston / cylinder units. They are supported on the one hand on the tensioning device 20, on the other hand via radial extensions 26 on the inner cell 16, so that forces exerted by the feed generators 25 can be introduced into the drill head 10 via the inner cell 16 and the control device 18.

At the rear end, an extendable support device 27 is provided on the inner wall 16, which is located in the extended position in the extended position shown in FIG. 1, in which it is supported on the bore wall or on the inner wall of a bore extension. With the help of the support device 27, which can also be designed as a parallelogram, ie can be displaced in a known manner transversely to the tunnel axis, the inner frame 16 is held approximately in the middle of the tunnel when the bracing device 20 is not activated.

In the embodiment of the tunnel boring machine 100 shown in the drawing, the inner kelly has a square cross section, i.e. it is designed as a kind of box profile. A drill material conveyor 28 of known construction extends through the interior of the inner kelly and serves to remove the drill material loosened on the face 3.

A so-called erector 29 is provided between the drill head 10 and the clamping device 20 — displaceable in the direction of the central axis M. This comprises an extendable middle part 30 and a holding device 31 arranged at the end of the middle part 30. It serves for the displacement of prefabricated components - for example made of concrete - for the production of a segment lining 32, which is indicated schematically in FIG. 2.

At the back of the drilling head shield 12 there is a shield tail 33 which covers the inner wall of the borehole over a certain area and which supports the wall of a tunnel borehole driven in soft-gesture information, which has not yet been secured by a segment lining 32, against collapse. The shield tail 33 is connected to the drill head shield 12 via a series of piston / cylinder units 34 distributed over the circumference, only one of which is shown in FIGS. 1 and 2. With the aid of the piston / cylinder units 34, the shield tail 33 can be displaced slightly relative to the drill head shield 12, as is necessary if the drill head 10 is to be pivoted relative to the axis M in order to change the direction of the tunnel bore.

In the shield operation shown in FIG. 1, the bracing device 20 is - as already mentioned - out of operation. Both the advance of the drill head 10 and the absorption of drive reaction moments serve a plurality of variable-length force generators 35 distributed over the circumference of the tunnel bore, only one of which is shown as an example in FIGS. 1 and 2 is. The variable-length force generators 35, which are preferably designed as piston / cylinder units and are optionally removable, extend between the drill head shield 12 and an end wall 36 which is present in the bore and faces the working face 3 and which, as shown in FIG. 1, begins at the start of shield operation of a steel ring 37 braced against the bore wall, as the tubbing expansion progresses - as shown in FIG. 2 - is formed by the end face of the tubbing expansion itself.

• a) In Fig. 1 ist die Tunnelbohrmaschine im Schildbetrieb während des Nachsetzens der Verspannvorrichtung in einer Weichgesteinformation dargestellt. Der hintere Teil der Innenkelly 16 sowie die nicht aktivierte Verspannvorrichtung 20 ruhen auf der Abstützvorrichtung 27. Da ein Tübbing-Ausbau noch nicht vorhanden ist, dient der Aufnahme der Vorschub- und Momentreaktionskräfte beim anschließenden Bohrvorgang, bei dem sich die Verspannvorrichtung 20 in ihrem aktivierten, in Fig. 1 gestrichelt dargestellten Betriebszustand befindet, die Abstützvorrichtung 27 hingegen - ebenfalls gestrichelt dargestellt - deaktiviert ist, der gegen die Bohrungswandung verpreßte Stahlring 37, an dem sich der Bohrkopf 10 über die längenvariablen Krafterzeuger 35 abstützt. Der Vorschub des Bohrkopfes wird durch Ausfahren der Krafterzeuger 35 bewirkt. Der vorhandene Schildschwanz 33 verhindert ein Kollabieren der Bohrungswandung in dem Bereich hinter dem eigentlichen Bohrkopfraum 13.
• b) In Fig. 2 ist die Tunnelbohrmaschine 100 während des Bohrvorganges ebenfalls im Schildbetrieb dargestellt, und zwar bei weiter fortschreitender Bohrung im Weichgestein, so daß bereits ein Tübbing-Ausbau 32 die Bohrungswandung abstützt. Die Verspannvorrichtung 20 wurde vor Beginn des Bohrvorganges aktiviert, indem durch Ausfahren der Kolben/Zylindereinheit 21 die Verspannprotzen 22 aus der in Fig. 2 gestrichelt dargestellten in die ausgezogene Position verlagert wurden, in der sie sich am Tübbingausbau 32 der Tunnelbohrung abstützen. Hingegen wurde die Abstützvorrichtung 27 aus der gestrichelt dargestellten Betriebsposition eingefahren, so daß die Innenkelly 16 gegenüber der Verspannvorrichtung 20 nun in Richtung der Tunnelbohrung verlagerbar ist. Zur Aufnahme von Vortriebs- und Momentreaktionskräften stützen sich die Krafterzeuger 35 nun auf der Stirnseite 36 des Tübbing-Ausbaus ab.
  Wie insbesondere im unteren Teil von Fig. 2 erkennbar ist, findet der Tübbing-Ausbau innerhalb des von dem Schildschwanz 33 überdeckten Bereich statt, so daß ein Kollabieren des an der Bohrungswandung anstehenden Gesteinsmaterials zuverlässig verhindert ist.
• c) In Fig. 3 ist nun die offene Betriebsweise der Tunnelbohrvorrichtung 100 dargestellt. Wie unmittelbar erkennbar ist, fehlt hier der Tübbing-Ausbau; zur Sicherung der Bohrungswandung sind lediglich Stahlstützen 38 vorgesehen. Die Aufnahme der Vorschub- und Momentreaktionskräfte erfolgt über die aktivierte Verspannvorrichtung, deren Verspannpratzen 22 mit Hilfe der Kolben/Zylindereinheit 21 nun gegen die Bohrungswandung gepreßt ist. Der Vorschub wird ausschließlich durch die Vorschuberzeuger 25 bewirkt, so daß die Krafterzeuger 35 für eine bessere Zugänglichkeit der sich an den Bohrkopfschild 12 anschließenden Bohrungswandung entfernt werden konnten. Da ebenso kein Schildschwanz 33 zur Abstützung der Bohrungswandung benötigt wird, dieser demnach entfernt oder auch nur angeklappt werden kann ist der an den Bohrkopfschild 12 anschließende Bohrungswandungsbereich zum Anbringen von Ausbausystemen unmittelbar zugänglich.

The various modes of operation possible with the tunnel boring machine 100 according to the invention are to be explained below:

• a) In Fig. 1 the tunnel boring machine is shown in the shield mode during the repositioning of the tensioning device in a soft gesture information. The rear part of the inner frame 16 and the non-activated bracing device 20 rest on the supporting device 27. Since there is no tubbing expansion, the feed and moment reaction forces are used during the subsequent drilling process, in which the bracing device 20 is activated in its 1, the support device 27, on the other hand - also shown in dashed lines - is deactivated, the steel ring 37 pressed against the bore wall, on which the drill head 10 is supported via the variable-length force generator 35. The feed of the drill head is effected by extending the force generator 35. The existing shield tail 33 prevents the bore wall from collapsing in the area behind the actual drill head space 13.
• b) In Fig. 2, the tunnel boring machine 100 is also shown in shield operation during the boring process, specifically as the drilling progresses in soft rock, so that a segmental lining 32 already supports the wall of the hole. The tensioning device 20 was before The beginning of the drilling process is activated by the bracing protrusions 22 being moved from the position shown in dashed lines in FIG. 2 to the extended position by extending the piston / cylinder unit 21, in which they are supported on the segmental lining 32 of the tunnel bore. In contrast, the support device 27 was retracted from the operating position shown in dashed lines, so that the inner frame 16 can now be displaced relative to the bracing device 20 in the direction of the tunnel bore. To absorb propulsive and momentary reaction forces, the force generators 35 are now supported on the end face 36 of the segmental lining.
  As can be seen in particular in the lower part of FIG. 2, the tubbing expansion takes place within the area covered by the shield tail 33, so that a collapse of the rock material lying against the bore wall is reliably prevented.
• c) The open mode of operation of the tunnel boring device 100 is now shown in FIG. 3. As can be seen immediately, the tubbing expansion is missing here; only steel supports 38 are provided to secure the bore wall. The absorption of the feed and moment reaction forces takes place via the activated bracing device, the bracing claws 22 of which are now pressed against the bore wall by means of the piston / cylinder unit 21. The feed is effected exclusively by the feed generator 25, so that the force generator 35 could be removed for better accessibility to the bore wall adjoining the drill head shield 12. Since likewise no shield tail 33 is required to support the borehole wall, it can therefore be removed or even only folded up, the borehole wall region adjoining the drill head shield 12 is directly accessible for attaching extension systems.

3 shows an example of a concrete spraying device 39 and an anchor drilling device 40.

In summary, the tunnel boring machine 100 according to the invention can be used to switch between shield operation and open operation in a simple manner. It is only necessary to put the tensioning device 20 into operation or to put it out of operation and to remove or install the force generators 35 and the shield tail 33.

Claims (15)

1. Tunnel boring machine (100) for driving a tunnel, operating at will either in open mode or in shield mode,

   with a boring head (10)

   with a shield tail (33) joined to the boring head (10) and at will at least partially overlying the wall of the bore of the tunnel over a limited length,

   with a clamping device (20) which can be secured at will in the bore of the tunnel and which serves for transmitting reaction forces produced by the boring process,

   with at least one advancing device (25) which can be brought into operation at will and which abuts on the one hand against the clamping device (20) and on the other hand against the boring head (10), for applying advancing forces to the boring head (10) when operating in open mode and

   with at least one force generator (35) of variable length and capable of being brought into operation at will, and which on the one hand abuts against a tubbing lining (32) or an abutment (37) for the tubbing lining, and on the other hand acts on the boring head (10) for applying advancing forces to the boring head (10) during operation in shield mode,

   characterised in that
   an inner kelly (16) is provided, which can be moved with respect to the clamping device (20) in the boring direction and which carries the boring head on that end nearest the workface, and that the at least one advancing device (25) is pivotally connected to the inner kelly.
2. Tunnel boring machine according to Claim 1, characterised in that the shield tail (33) is designed in such a way that the region of the wall of the bore which can be overlain by it can be exposed.
3. Tunnel boring machine according to Claim 1 or 2, characterised in that the inner kelly (16) is mounted in the clamping device (20) to be displaceable longitudinally but not rotationally, and that the boring head (10) is mounted rotatably on the inner kelly (16).
4. Tunnel boring machine according to Claim 3, characterised in that a driving block (14) for rotary driving of the boring head (10) is provided between the boring head (10) and the inner kelly (16) and is designed so that the driving reaction torques are transmitted into the inner kelly (16).
5. Tunnel boring machine according to one of Claims 1 to 4, characterised in that the boring head (10) is pivotally mounted on the inner kelly (16) in such a way that in operation the axis of rotation (M') of the boring head (10) can be tilted with respect to the longitudinal axis (M) of the inner kelly.
6. Tunnel boring machine according to Claim 5, characterised in that the inner kelly (16) is mounted in the clamping device (20) to be capable of pivoting about a chosen axis perpendicular to its longitudinal axis.
7. Tunnel boring machine according to Claim 6 or 6, characterised in that at least one control device (18) of variable length is provided, connected on the one hand to a part of the boring head (10) or of the driving block (14) which is fixed with regard to rotation, and on the other hand to the inner kelly (16).
8. Tunnel boring machine according to Claim 7, characterised in that advancing reaction forces are transmitted from the boring head (10) to the inner kelly (16) via the control device (18).
9. Tunnel boring machine according to one of Claims 1 to 8, characterised in that the control device (18), the advancing device (25) and/or the force generator (35) are formed by hydraulically actuated piston/cylinder units.
10. Tunnel boring machine according to one of Claims 1 to 9, characterised in that ball joints are provided for forming the pivotal connection between the boring head (10) and inner kelly (16) and/or between inner kelly (16) and clamping device (20).
11. Tunnel boring machine according to one of Claims 1 to 10, characterised in that the driving of the boring head (10) is achieved electrically and/or hydraulically.
12. Tunnel boring machine according to one of Claims 1 to 11, characterised in that means are provided for simultaneously introducing bore-supporting props and/or linings during the boring process.
13. Tunnel boring machine according to Claim 12, characterised in that the means are mounted between the boring head and the clamping device (20).
14. Tunnel boring machine according to one of Claims 1 to 13, characterised in that a spoil conveyor (28) extending through the inner kelly serves for transporting away the spoil released from the workface.
15. Method of driving a tunnel bore, in which, according to the nature of the ground material surrounding the bore one switches between an open mode of operation and a shield mode, in which during the open mode the advancing forces are transmitted from a clamping device through an inner kelly carrying the boring head on its workface end and in which during the shield mode of operation the advancing forces are applied to the boring head through at least one force generator acting between a tubbing lining or an abutment for the tubbing lining and the boring head.