EP2201217B1 - Method and device for positional stabilising of tunnel lining elements - Google Patents

Abstract

The invention relates to a method for positional stabilising of tunnel lining elements (2) applied in tunnel tubes (1) over the region adjacent to the shield tail (8) of the driving shield of a tunnel boring machine in which the backfilling (10) and stabilising are carried out. A retaining construction (5) is detachably connected to the inner surfaces (7) of the tunnel lining elements (2) to exert a tensile force, which is exerted in an essentially radially symmetrical fashion in the tunnel tubes (1) and to hold the tunnel lining elements (2) in the set position, wherein the detachable connection between the tunnel lining elements (2) and the multi-part retaining construction (5) is essentially maintained by a vacuum relative to the external air pressure or by a magnetic field acting on the reinforcements in the tunnel lining elements (2).

Description

The invention relates to a method for the stabilization of position of a tunnel tube offset tunnel construction elements, in particular tubbing, after the displacement and the Vor-direction thereto with a support structure, according to the preamble of the first method claim and the first device claim.

Tunnel boring machines facilitate propulsion even in poor, brittle soils and enable a high degree of mechanization in tunneling. The design and details of the construction of the machines are prepared for each site on the soil digestion results of geologists and hydrologists, according to the experience of the manufacturers of milling, trailing equipment, tubbing, and construction adapted. Nevertheless, in this hundreds of thousands or millions of tons of outbreak material comprehensive construction projects surprising problems that are referred to as subsoil risk can not be excluded.

In the case of tunnel boring machines with shields, for tunnel construction with segments, behind the cutting wheel is the cylindrical shield in which the drives of the cutting wheel, the transfer equipment for the excavated debris and the jacking cylinders for the jacking are arranged. The rear part of the shield, the tail shield, consists of a cylindrical pipe jacket with a length larger than the maximum dimension of the segments, in which a hydraulic manipulator, called Erector, with which the segments are made into a complete ring, with the closing block of 360 ° and connected to the already built-in pre-filled ring of Tubbingen.

For certain geological formations, or where sealing is required, diagonal engagement of the segments of a ring and adjacent rings is often made, or bolting, tapping or the like, to ensure the established stable circular position upon subsequent exit from the shield tail.

After solidification of the environment and the backfilling of cavities, can usually be done several yards behind the demolition and removed the built-in security parts and reused.

However, this procedure is associated with considerable labor and time.

It must subsequently be closed all screw holes, because of the numerous flanges, sleeves, plates rebar connections, etc. are thus associated with additional costs for the production of the segments and for the additional time required for processing.

In large tunnels and especially with large tube diameters large, wide segments are used with spherical joints, which act as hinges, which occur in local deviations from the circular shape of the tunnel tube no chipping or overstressing. This is bought with a lower form-fitting of the segments with each other.

Once the tunnel boring machine is supported on the youngest mounted tubbing ring in the forward drive direction and the next Propulsion stroke with cutting wheel and shield complete with caster, the newly installed tubbing ring leaves the shield tail, from which it is stabilized. In this case, the annulus between the inner contour of the milled out mountains and the outer diameter of the tubbing ring released and it may, depending on the milled material in addition to breakouts or caverns around the shield of the machine form or have formed.

It is therefore at the same time injected good flowable Perlkies for backfilling through holes in the tubbings or a mixture of Perlkies, cement, concrete suspension, foams, surfactants, plastics or mortar, etc. pressed. As a result, the circular tubbing vault from the outside of the surrounding mountain is positively supported by fighters formation and kept stable.

If the immediate backfilling is followed by a break or the after-crumbling of non-free-flowing, schistose, platy, bulky ones, the flow paths for the pearl gravel are blocked and clogged, as well as crevices for the inflow of grouting material.

In plate-shaped rock formations resulting cavities and segregations are sealed in the militant area of the elm and around the tunnel vault and are to be filled only by means of elaborate Bohrinjektionen, which requires a lot of time in which the mountains continue its backfilling by gravity and water.

Meanwhile, the segments, even outside the shield tail, must be kept stable in the desired position, so that the circular shape is not lost; If one applies grouting of mortar through holes in the tail shield, then the problem of the necessary delay of the setting time and thus delayed propulsion occurs.

Occurs in the unfavorable case further break after already done, meter-high cavitation with corresponding dynamic loading of the ridge stones through the falling mountains, in insufficiently backfilled Ulmsteinen or cavities in the mountains, the Tübbingringe eioder polygonal deformed slip the tubbing rings and even sole or Schlussteine or the tunnel tube drop by several cm. It can also, with lateral expansion of the elm, collapse the tubule arch.

Mitigation can be achieved in some rock types by creating a protective screen by pre-injecting through holes through flat-angled openings in the shield of the tunnel boring machine. However, this requires injectability and a necessary setting time. Radial anchoring can remedy where this measure is not possible, but does not solve the problem of uneven backfilling and support of the segments and takes time and is expensive.

The stable support of the segments can be achieved in those that are not provided for screwing only by additional, doweled on the tubbing steel support rings, several per meter, and tie rods and lashing and busbar, their subsequent disassembly, after stabilization of each tubbing ring, because of is necessary for the wake of the tunnel boring machine and takes a lot of time, slows down the propulsion.

The object of the invention is to increase the tunneling performance of a tunnel boring machine in difficult or unexpectedly rugged rock formations with fault zones, the method for position stabilization by a quasi-virtual extension of the shield tail of the tunnel boring machine and a device for exercising this new To provide a method by which the disadvantages described above are eliminated.

This object is achieved in the method and apparatus for its implementation with the features of the characterizing part of the method claim and the first device claim.

A method claim and a first device claim, as well as the subclaims simultaneously form part of the description of the invention.

For vaults, it is known and customary to exert pressure from outside to produce the stability. In full tunneling, this is inherently by the mountain pressure and water or, if necessary, artificially by backfills and / or injections.

If it is not possible due to the lack of mountain and / or water pressure to build up an overpressure from the outside, which would loosen the vault, then the inventive method intervenes, by means of one, on the blocks of the tunnel wall from the inside acting vacuum by vacuum, with the one Traction is transmitted, which is evenly distributed on the segments of a row of rings and exercised by tension elements. This negative pressure acts on the inner surfaces of the tubbings by means of suitable vacuum plates, as long as the newly manufactured tunnel section is still unstable and forms an apparent extension of the shield tail, which accordingly has no wall thickness.

So far vacuum hoppers and grippers have proven to be suitable for the installation of tubbings in any position in the space, which move and hold segments of cranes or the erector segments of more than 10 tons. The inventive method for stabilizing the position of tunnel tunneling elements displaced to a tunnel tube via the tailpipe of the tunneling shield of a tunnel boring machine, subsequent track in which the backfilling and stabilization takes place, uses a support structure releasably connectable to the tunneling elements on their inner surfaces to exert a tensile force.

This tensile force is directed substantially radially symmetrically in the tunnel tube and is exerted by tension elements.

Through the shield tail, the tunnel expansion elements of a ring are held in the predetermined position, until the stabilization of the respective ring, the detachable connection between the Tunnelausbauelementen and the multi-member mounting structure, by negative pressure relative to the outer air pressure or by, acting on the reinforcement of the Tunnelausbauelemente, magnetic field is, which allows the desired position freely.

It is essential that the tensile force to stabilize the tunnel lining elements of tensile forces of several attacking on the support structure holding elements, as tension elements and thus stabilizing, is exercised.

It is important that the tensile force, in the form of several tensile forces, is exerted as evenly distributed acting on the individual tunnel lining elements of the tunnel tube, the sizes of the tensile forces are respectively adapted to those areas in which the backfilling must be done to stabilize the tunnel tube and after stabilization of which the action of these tensile forces can be stopped.

It is for the production and for the solution of the connection between the Tunnelausbauelementen and the

Support structure (5), with the negative pressure of, on the support structure (5) mounted switchable suction plates / vacuum lifter (9) or magnetically switchable magnet, on the support structure (5) is generated, these in turn held by support members (6) and supported is, because it is the progressive expansion without delay by outs and internals possible.

If the holding elements acting on the support structure consist of hydraulic cylinders, their operation with the hydraulic system which is always present on large machines is possible and their adjustment can be made quickly and very accurately.

The support structure for stabilizing the position of tunnel construction elements as a train for rapid and semi-automatic position stabilization of tunneling elements, in particular Tübbingen, which is provided when squeezing out of the tail of a tunnel boring machine to compensate for missing supports on freshly milled or broken mountains, conveniently consists of a steel structure with Stiffening rings and flange plates, as it is usually used for anchor and anchor removal, which is then equipped with at least one or more vacuum lifters, vacuum mats, suction feet or with sufficient ferromagnetic content in the tunnel construction elements, such as cast iron or Schweißkonstruktstbbingen with strong switchable magnets ,

Thus, the stabilization of the segments or other expansion elements, by retaining the ring of the tunnel expansion elements in the desired position, while the backfilling and fixing by anchors and injections occurs.

In order to successfully use the connection between the steel construction for stabilizing the position of the tunnel construction elements, which is provided with a large number of switchable suction cups or permanently evacuated suction plates, they must be made adapted to the dimensions of the segments and snugly conforming to their contour and accordingly be well sealed.

To avoid additional load on the tunnel, the device for stabilizing position of the tunnel construction elements is mounted on an adjustable support structure, which is supported by the shield of the tunnel boring machine head or the front part of its tail or by a bridge between these parts.

A particularly space-saving self-propelled or intermittently Nachsetzbare arrangement is possible if the support structure is placed either on longitudinal rails in the dome, preferably sharing of existing rails, such as the carriage carriage near the ridge or the erector in the tail shield.

The most favorable working arrangement is obtained when the support structure, during the propulsion stroke of the tunnel boring drill head, against the moving sign or the caster, is movably supported and oriented exclusively to the already stable tunnel tube, to avoid movements of the tunnel components on the not yet stabilized segments are to be transmitted.

For a quick transfer and rapid adaptation of the support structure to the particular state of development of the tunnel tube hydraulically actuated adjusting means or actuators are preferred with which generates a quick-clamping effect and the monitored, biasing forces can be quickly controlled and adjusted, and make a very rapid implementation of the support structure possible ,

For automatic measurement and correction, the support structure is equipped with sensors and proportional controls, with which deviations from the ideal shape and ideal position of the tunnel tube or changes in the preload forces can be automatically measured and, if necessary, corrected.

When used in difficult areas of the tunnel, the support structure can also be equipped with extendable and preferably expandable, centering, in particular with separately operable inner counter-cone, for quick, accurate and easy positioning and to improve the safety, the slip resistance in sudden stresses occurring. The support structure and the tubbing rings is thus given an additional form-fitting hold and about in the case of a strong Kavernenverbruches slipping of the support structure is prevented by shearing the suction plates or the magnets.

It is advantageous because of the reduced conversion work, if the centering pins and the brackets for the holding elements) of the support structure, in the bottom and Ulmbereich the tunnel tube, while passing the entire tunnel boring machine, remain mounted and even used as caster roadway bearing blocks.

In order to improve the safety against slipping and slippage of the retaining elements of the support structure on the tunnel construction elements, it is advantageous if additionally securing dowels are attached in critical zones of the load.

In difficult spatial forms or clearances, the support structure may comprise retaining elements made of ropes, chains or tension rods or redirecting the tensile forces can be done with a support structure with which the position of the direct force axes, in the center axis of the tunnel boring machine, together with their Zusatzaggegaten is bypassed.

In order to improve the adhesion of the retaining elements of the support structure by negative pressure on the inner surfaces of the tunnel lining elements, a temporary treatment of the tunnel lining elements, in particular segments, with a highly viscous liquid can be made, with which they are sealed, which also closed an open-pore surface on the inner surface of the tunnel lining elements can be.

The shell of a tunnel tube, which is fragile compared to the mountain massif, and in particular a ring from Tübbingen, can hardly collapse due to external forces as long as the circular cross-section is maintained, because the solidly reinforced concrete withstands enormous pressures. If, in the absence of pressure from the outside, the bulging of the tubbing ring, even punctiform, is made possible, then the stability in all directions decreases abruptly by polygonal or egg-shaped formation of the tunnel tube cross-section and it can not oppose any slight pressure from the inside or from the outside more resistance become.

To avoid the tunnel tube being pushed inwards, the segments must never deviate outwards from the desired position.

With the application of a tensile force bias to the inside, according to the method, thus a uniform pre-pressing from the outside, at least during the stabilization time of the mortar or Perlkiesbettes the backfill of the new tubbing ring, simulated and thereby the resistance to a large and discontinuous application of force from the outside while only possible.

The erector mounted in the shelter of the tail shield the next tubbing ring stone by stone, then the Schlusstein is relined and used. Subsequently, the feed cylinder press this tubbing ring to the previous ring in the axial direction, until it stops and thus make a full edition of the segments.

In the lower Ulm- or Sohlsteinen support plates may be designed with pins and as a leading component mounted the trailing lane, be designed in modular form and remain until the passage of the tunneling machine in each tubbing. The anyway required road surface mounting on both sides of the Ulm is thus only brought forward in time.

In particularly critical zones, where dangerous cavities are detected outside the machine and, therefore, heavy bursts are expected behind the shield tail or the inner surface of the segments does not provide a safe suction plate attack, it is necessary to place conventional security dowels on the tabs provided therebetween; However, the otherwise required large-scale anchoring can be omitted.

While the support structure for weight reduction of ropes, chains and tension rods is constructed as a traction unit, spatial constraints such as cantilevers must support bending moments and the diversion of the tensile forces with adapted support structures are made.

Between the parts of the support structure there is always enough space for the radial introduction of injection or anchor holes for the final stabilization of the mountain.

The invention will be described with reference to the schematic drawing of an embodiment of the device.

Fig. 1

Querschnitt durch einen Berg mit einem Tunnelausbau mit Tübbingen und teilweiser Hinterfüllung in einem klüftigen, plattig schiefrigen, brüchigen Gestein;

Fig. 2

Querschnitt durch einen Berg mit einem Tunnelausbau mit Tübbingen nach Fig.1, mit durch Verbruch ausgelöstem Nachgeben des rechten Ulmes des dadurch eingedrückten Tunnelrohres;

Fig. 3

Querschnitt durch einen Berg mit einem Tunnelausbau mit Tübbingen, die sich noch im Schutz des Rohres des Schildschwanzes befinden, in einem klüftigen, plattig schiefrigen, brüchigen Gestein, mit an Dübeln verschraubt gesetzten Innenankern, als Ausbauträger, zur Erzeugung von Zugkraft im Gewölbe bis zur Stabilisierung des Ausbaues;

Fig. 4

Querschnitt durch ein Gebirge mit einem Tunnelausbau mit Tübbingen, die sich noch im Schutz des Rohres des Schildschwanzes befinden in einem klüftigen, plattig schiefrigen, brüchigen Gestein, mit an den Tübbingen festgesaugten Saugplatten zur Übertragung der Zugkraft, von Hydraulikzylindern, die als Zuganker oder Halteelemente dienen, einer Haltekonstruktion ausgeführt;

Fig. 5

Querschnitt durch ein Gebirge mit einem Tunnelausbau mit Tübbingen, die sich noch im Schutz des Rohres des Schildschwanzes befinden, einem klüftigen, plattig schiefrigen, brüchigen Gestein, mit einer Haltekonstruktion nach Fig.4 mit von den Tübbingen abgehobenen Saugplatten und dem angedeuteten Rahmen der Tunnelbohrmaschine samt Nachlauf, als Schienenfahrweg für die Haltekonstruktion.

It shows:

Fig. 1

Cross section through a mountain with a tunnel extension with tubbing and partial backfilling in a fissured, platy schistige, brittle rock;

Fig. 2

Cross section through a mountain with a tunnel with Tübbingen after Fig.1 with, by breaking yielded yielding of the right Ulmes of the thus pressed in tunnel tube;

Fig. 3

Cross-section through a mountain with a tunnel extension with tubbing, which are still in the protection of the tube of the tail shield, in a fissured, platy schistigen, brittle rock, with anchors bolted to anchors set as expansion beams, to generate traction in the vault to stabilization the expansion;

Fig. 4

Cross section through a mountain range with a tunnel extension with tubbing, which is still protected by the Pipe of the shield tail are in a fissured, platy schistose, brittle rock, with sucked on the tubbing suction plates for transmitting the tensile force of hydraulic cylinders, which serve as tie rods or retaining elements, designed a support structure;

Fig. 5

Cross-section through a mountain range with a tunnel extension with tubbing, which are still in the protection of the tube of the tail shield, a fissured, platy schistose, brittle rock, with a holding structure according to Figure 4 with suction plates lifted off the tubbing segments and the indicated frame of the tunnel boring machine including caster, as a rail track for the supporting structure.

In Fig.1 the cross-section through a tunnel tube (1) is shown, which consists of tunnel construction elements (2) in the form of segments, which are assembled in a circular ring, with a bottom embedded in a bedding stone (3). The segments are strung together with crowned end faces and close close to the already pre-filled previous ring of Tübbingen.

The backfilling 10 with gravel occurred, as shown on the right side, by filling holes 12, partially insufficient.

The reason for the insufficient filling is the schistige strong brittle nature of the mountains through which it comes to collapse collapses, while the material completely displaced the way for the backfill, thereby preventing the construction of a uniform external pressure on the tunnel tube 1.

The result is in Fig.2 shown, in which it is shown how the tunnel structure elements 2 buckle right due to lack of resistance to the outside and then up inwards, which can lead to destruction, if not, as in

Fig. 3 is shown, by installation a support structure 5, in the form of a steel frame, which is connected to the tubbing of tunnel construction elements 2 with a very large number of dowels 4 and with at least one holding element 6 for a ring of tubbing, as a tie rod or pull rope through Traction be held in the circular ring position.

The inventive support structure 5 now consists of several articulated parts, the suction plates 9 are positioned and held by holding elements 6, are fixed by vacuum on the inner surface 7 of the tubbings, with centering pins 14 are inserted into holes in the tubbings and thus the exact location of the suction plates. 9 Secure the support structure 5.

The tensile force for securing the position of the tunnel lining elements 5 is generated with the holding elements 6, which can exert a uniform and finely graded and rapidly adjustable force as a hydraulic cylinder. These also serve to collapse the support structure 5 when moving after stabilization of a section of the tunnel tube 1.

The support structure 5 extends over a large portion of the ring of the segments, wherein the bottom portion of both sides of the wedge stone 3 requires no support force, and is based on both sides of support brackets 11, which are bolted into the tubbing.

Fig. 5 shows the same arrangement of a support structure 5, which is not yet connected to the Tunnelausbauelementen 2. This is supported by a frame 16 which is movable with wheels on a rail 15 and arranged in the ridge area of the tunnel tube 1, to have underneath space for the components of the tunnel boring machine and still be with their propulsion with movable.

In the drawings, 13 denotes the rugged mountains.

LIST OF REFERENCE NUMBERS

1

tunnel

2

Tunnel lining element

3

Keilstein

4

dowel

5

support structure

6

Retaining element (hydraulic cylinder)

7

Inner surface of the Tunnelausbauelementes 2

8th

shield tail

9

Suction Plates

10

backfill

11

Centering pin with bracket

12

filling holes

13

rugged mountains

14

Centering pin the

15

rail

16

Frame of the support structure 5

Claims (17)

1. Procedure for stabillising the position of extension elements (2), shifted with respect to a tunnel tube (1), over the section following the shield tail (8) of the driving shield of a tunnel boring machine, in which backfilling (10) and stabilisation take place. For this purpose, a detachable bracing construction (5) is connected to the tunnel-lining elements (2), on which internal surfaces (7) a tensile force is exerted in an essentially radially symmetrical direction into the tunnel tube (1), holding the tunnel-lining elements (2) In the predetermined position, characterised by the fact that the removable connection between the tunnel extension elements (2) and the multi-member bracing construction (5) is essentially maintained by a vacuum pressure relative to the external air pressure, or by a magnetic field acting on the steel reinforcement of the tunnel-lining elements (2).
2. Procedure according to the above-mentioned claim, characterised by the fact that the tensile force for the stablilsation of the tunnel-lining elements (2) la exercised by the tensile forces of several bracing elements (8), gripping on the bracing construction (5) as tensile elements.
3. Procedure according to claim 1, characterised by the fact that on the section following the shield tail for the stabilisation of the tunnel extension elements (2) a tensile force consisting of several tensile forces is exercised, evenly distributed over the Individual lunnel-lining elements (2) of the
   tunnel tube (1), whereby the magnitudes of the tensile forces are always adapted to the respective areas that are backflilled for the stabilisation of the tunnel tube (1). Once these areas are stabilised the action of these tensile forces is ended.
4. Device to exercise the procedure according to one of the claims 1 to 3 with a bracing construction (5), characterised by the fact that the removable connecticn between the tunnel-lining elements (2) and the bracing construction (5), with the vacuum pressure of the switchable suction plates/vacuum Ilfters (9) or the switchable magnetic field caused by the magnets, is exercised on the bracing construction (5) maintained and supported by the bracing elements (6).
5. Device according to claim 4, characterised by the fact that the gripping bracing elements (6) on the bracing construction (5) consist of hydraulic cylinders.
6. Device according to one of the claims 4 or 5, characterised by the fact that the bracing construction (5) acts as a traction combination for quick positional stabilisation of tunnel extension elements (2), particularly tubbing segments, with at least one or more vacuum lifters, vacuum mats, suction cups or, if there is a sufficient ferro-magnetic content in the tunnel-lining elements, as with cast Iron or welded tubbing segments, equipped with switchable magnets, by means of which the stabilisation of the tunnel lining elements (2), in particular tubbing segments or suchlike, Is achieved by bracing them in the desired position, during which the backfilling and fastening occurs through anchorings and injections.
7. Device according to one of claims 4 to 6, characterised by the fact that the bracing construction (5) for position stabilisation of tunnel-lining elements (2) over a large area is to be provided, equipped with multiple switchable suction cups or permanently vacuumpumped suction plates (9), manufactured according to the tubbing segment dimensions, properly fitting within their contours and accordingly providing a strong seal.
8. Device according to claims 4 to 7, characterised by the fact that bracing construction (5) for position stabilisation of the tunnel-lining elements (2) are borne by an adjustable supporting construction, as a frame (18), supported by the shield of the tunnel drilling machine's drill bit or by the front part of its tail action, or by a bridge between these components In order to avoid an additional tunnel load.
9. Device according to claims 4 to 8, characterised by the fact that bracing construction (5) Is designed either on lengthwise rails (11) in the calotte, preferably under joint use of the available rails, perhaps of the nearest carriage or the erector carriage in the shield tail (8), as a self-propelling unit or unit deployable in segments.
10. Devices according to one of the claims 4 to 9, characterised by the fact that the bracing construction (5), during the propelling stroke of the tunnel drilling machine's drill bit, is movable, orienting itself exclusively on the already stabilised tunnel tube (1) in order not to transfer the movements of the tunnel-lining elements (2) onto tubbing segments not yet stabilised.
11. Device according to one of the claims 4 to 10, characterised by the fact that the bracing construction (5) is to be provided, preferably, with hydraulically-operated bracing elements (6) as a means of adjustment, or actuators, by means of which the monitored pre-tensioning forces are controlled and adjusted to the respective dismantling condition and the stabilisation of the tunnel tube (1) allowing for quick adjustment of the bracing construction (5).
12. Device according to one of the claims 4 to 11, characterised by the fact that the bracing construction (5) is equipped with sensor circuits and proportional controls, by means of which the tunnel tube's (1) deviations from the Ideal form and the ideal position or deviations of the pre-tansloning forces can be automatically detected and, if necessary, corrected by the adjustment of the bracing elements (6) in case of violation of the tolerance limit.
13. Device according to claims 4 to 12, characterised by the fact that the bracing construction (5) is equipped with a wheel-away and preferably expandable centring pin (14), particularly with a separately operable inner counter cone, for improvement of the anchoring security and slip-prevention of the bracing construction (6) protecting it against shook loads.
14. Device according to claim 13, characterised by the fact that the centring pins (14) and the consoles for the bracing elements (9) of the bracing construction (5), in the base and the side sections of the tunnel tube (1) are located outside the envelope of the tunnel boring machine, remaining in place during its passing and which may be provided as follow-up rail support blocks.
15. Device according to claim 13 or 14, characterised by the fact that for the enhancement of anchoring security and slip-prevention of the bracing construction (5), on the tunnel-lining elements (2) In critical zones of the load, additional securing pins (4) are attached to the bracing elements (9) of the bracing construction (5).
16. Device according to one of the claims 13 to 15, characterised by the fact that the bracing construction (5) consists of retaining elements (9) such as cables, chains or tension rods or that, based on considerations of space, a supporting construction deflects tensile forces to avoid the area of the direct power axis In the centre axis of the tunnel boring machine and Its auxiliary devices.
17. Device according to one of the claims 4 to 16, characterised by the fact that the retaining elements (9) of the bracing construction (5) particularly tubbing elements, be sealed with a temporary treatment of a highly viscose fluid for grip enhancement during exposure to vacuum pressure upon inner surfaces (7) of tunnel-lining elements (2),

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