EP0077943B1 - Method of constructing a tunnel - Google Patents

Abstract

Tunnels are constructed by freezing soil and removing frozen soil between starting and end shafts of the tunnels. Tunnels are driven in an uncomplicated manner in rapidly changing soils without auxiliary construction means. A hole is bored in or near the planned axis of the intended tunnel between starting and end shafts. A soil freezing work pipe is inserted into the hole. The pipe is cooled by a cooling agent. The soil freezing work pipe continues to be cooled until an ice and frozen soil mass has formed around the work pipe, which frozen mass has a diameter which is larger than that of the planned tunnel. Frozen soil is subsequently excavated, leaving a frozen soil lining, which is immediately supported by a primary support lining or a permanent lining.

Description

The invention relates to a method for creating a tunnel between a starting and a target shaft by means of ground freezing.

Various methods are known for creating a tunnel. The type of tunneling method and the optimal tunneling device is mainly determined by the intended use, the required cross-section with the associated expansion and the given type of rock or soil. Criteria of paramount importance continue to be cost-effectiveness and, in difficult ground conditions, safety both for the people who build the tunnel and for the property itself.

A conventional method that is used for driving in loose rock is knife driving, in which the ground is supported before it is mined. However, knife jacking cannot be used or can only be used to a limited extent on soils that are low in consistency or under water pressure. In addition, deformation of the knife or deviations in the direction of advance cause considerable difficulties.

Shield construction is a semi-mechanical process. With this method, the pre-pressing takes place automatically. The shield construction is suitable for large cross-sections both in dry and under water - then with a compressed air shield. The shield, a tubular steel structure with the cross-section of the required excavation, engages with the front edge, the cutting edge, in the face, the face, the tunnel tube. In the protection of its rear part, the shield tail, the segment-shaped parts of the extension, the tubbings, are made of cast iron or reinforced concrete. The shield is pushed against the face using presses that support the expansion. Shields are used in clay, sand and rubble. If hard, large rock inclusions occur, the method can only be used to a very limited extent.

A variant of this is the compressed air shield, which is used in the groundwater. This very complex process is only used when lowering groundwater is not possible. As with normal shield jacking, its limits are set out. In addition, changing floors or tunnels in well-drained soils with little overlap cannot be driven due to the risk of blow-out.

In addition to the shield drives, there are mining drives, some of which work in difficult soil with additional construction measures. B. the tunnel construction with shotcrete protection, injections, groundwater lowering or icing etc. All methods can be used to a greater or lesser extent, depending on the type of soil, water content, consistency, tunnel cross-section, coverage and the total costs.

To create a tunnel using ground freezing, boreholes are drilled parallel to the tunnel axis at certain intervals from the planned outer boundary of the tunnel and inserted into these pipes through which a coolant circulates (see e.g. Die Bautechnik, Volume 12, 1973, HL Tessberger et al. "Application of the Freezing Process", pages 414-420). The coolant removes heat from the ground until a frost body has formed around the planned tunnel cross-section, which supports the surrounding ground during mining and secures the tunnel space that has already been created against groundwater and ground burglary.

The latter method involves relatively high costs for the creation and maintenance of the frost body. The other known methods have decisive technical disadvantages: they cannot be used in near-surface tunnel structures that are to be created in a rapidly changing subsoil and where water is to be expected, or can only be used with the help of considerable construction aid measures. The auxiliary construction measures generally represent an almost unreasonable burden on the environment and are often only approved because there are no technical alternatives and the construction project must be carried out.

The invention is therefore based on the object of specifying a method of the type described at the outset by means of which a tunnel can be created in a simple manner without construction aid measures in a rapidly changing ground.

This object is achieved in that a bore is drilled in or near the planned axis of the future tunnel between the start and target shaft within the cross-sectional area of the planned tunnel, a freezing working pipe is introduced into the borehole formed, the freezing working pipe through a The coolant is cooled until a frost body with a larger diameter than the planned tunnel diameter has been formed around the freezer work pipe and then the frozen soil is broken down.

As with any knife or shield jacking, a more or less large starting and target shaft is also necessary in the method according to the invention. A cooling fluid is passed through the freezing working pipe until a freezing body with an essentially circular cross section has formed around the freezing working pipe with a diameter which is so large that a freezing body of circular cross section remains after the tunnel cavity has been created. This remaining frost body serves on the one hand to seal against water and on the other hand for the purpose of statics, i. H. to secure the tunnel cavity and the people working in it.

According to the invention, the soil around the freezer work pipe is broken down in the frozen state. In an advantageous manner, the method according to the invention creates a soil to be dismantled, which can be degraded in a targeted manner and without technical problems due to its uniformity. The frost body enables, for example, mining to be mined, since there is a backup - in relation to the tunnel axis - both in the radial and in the axial direction. Since the tunnel is always driven into a frost body with a circular cross-section and an annular frost body always remains, the method according to the invention offers a safe temporary installation until a first safety shell is inserted or until the final expansion has been carried out.

The proposed method therefore enables propulsion that is independent of the depth of the tunnel and is also possible in strongly changing soil types. In particular, this method can also be used in an environmentally friendly manner in groundwater without compressed air or other construction aid measures.

In a particularly economical variant of the method according to the invention, the frost body is created in sections. In this embodiment, a frost body is always formed only in a part of the floor area between the start and the target shaft. As a result, the energy costs are significantly reduced compared to a method in which the frost body along the entire drilled route, i. H. in this case between the start and the target shaft. Known methods of creating a frost body in several sections work, for example, with freezer working tubes which are divided into several freezer tube sections by partitions which are gradually cut through. Sectional freezing is also possible if an inner tube is inserted into the freezing work tube, with the help of elastically deformable seals in the area of the floor to be iced, a liquid-tight space is formed between the freezing work tube and the inner tube and in this space one is used for heat exchange with the cooled one Fluid freezing liquid is introduced and subsequently a cooled fluid is introduced into the inner tube. According to another method, an inner tube is also inserted into the freezing working tube, this being equipped with a heat-insulating layer over part of its length.

Each of the specified methods enables the frost body to be created in sections. In accordance with the progress of the tunneling, the frost body is first created in the area of the starting shaft in which tunneling begins. Depending on the progress of the work following the freezing of the ground - essentially this is the excavation of the ice-earth material around the freezing work pipe - a frost body is created in further sections.

According to a further advantageous embodiment of the inventive concept, a low-boiling, liquefied gas, in particular liquid nitrogen, is used as the cooling fluid. Because of their low boiling temperatures, these gases can extract significant amounts of heat from the ground. A particularly suitable low-boiling liquefied gas is liquid nitrogen because it is cheap, because of its low boiling point it cools down quickly and is also easy to handle. Brine can also be used as a coolant.

Basically, it is possible to insert the freezer work pipe into the bore driven between the start and target shaft and then to pull the drill pipe. In a particularly expedient variant of the inventive concept, however, the drill pipe itself is designed as a freezing working pipe. The drill pipe therefore does not have to be pulled, but can remain in the ground and thus forms the »tunnel axis«.

In an advantageous embodiment of the concept of the invention, several holes are drilled between the start and the target shaft in large tunnel cross-sections, corresponding to the later tunnel cross-section, a freezing working tube being introduced into each borehole. In this variant, not only is a freezer work tube, but several freezer work tubes are placed in parallel or in cycles according to the cross-section and profile. The number or arrangement of the freezer work tubes is selected according to the tunnel cross-sectional area and geometry.

Conventional mining methods all have in common that they are either carried out manually or require devices that are supported to the rear - that is, absorb the reaction forces generated by the pressure of the tools on the working face. According to a particularly advantageous variant according to the invention, the frozen soil is broken down by means of a mining device supported on the freezing working pipe. If several freezer work pipes are placed in the case of large tunnel cross-sections, then several dismantling devices are also used according to the invention, which work side by side in parallel or in cycles. With this procedure, the freezer working tube absorbs the reaction forces on the one hand and at the same time serves as a guide element for the direction of advance. With the position or measurement and exact placement of the freezing working pipe, the oil deviation of the tunneling is determined and no longer needs to be monitored.

The freezer work tube itself is provided on the outside with a thread, rack or the like, which serve as a guide and abutment when feeding the excavation device. Since the freezer work tube is composed of more or less long sections, as are customary in drilling technology, the end that is released can be removed during the advance taken and used again later.

In this variant, the freezing work tube is subjected to tension and has to absorb very high reaction forces. Experience has shown that the freezing work pipe cannot be detached from the building site as long as the icing leading to the dismantling forms a sufficient abutment.

The excavation device itself can be completely geared to the requirement of rapid, economical dismantling of the frozen ground. The building site can be dismantled, loaded or transported fully automatically - centrally through the freezer work tube - by hammers, chisels, milling cutters or similar or combined tools. The axial position of the freezing work tube also offers the possibility of using a rotating device which, for example with the help of the above-mentioned rack-freezer work tube, jerks into the ice / earth body or with a thread in a helical manner. Hydro or thermal removal processes are also conceivable. The dismantling can immediately be expanded e.g. B. shotcrete fuse or final expansion z. B. Follow extruded concrete.

Depending on the diameter of the freezer working tube, frost body diameters of up to approx. 5 m can be achieved with the methods according to the invention. The proposed method is therefore preferably to be used in tunnels with a relatively small diameter. In the case of larger tunnel cross-sections, several freezer work pipes can be arranged at appropriate intervals within the excavation profile in such a way that a sufficiently large, overlapping frost body is created and can be dismantled simultaneously or intermittently with several tools.

• Zum Erstellen eines Tunnels ist ein Startschacht 1 mit Schachtwand 3 und ein Zielschacht 2 mit Schachtwand 4 ausgehoben worden. Zwischen Startschacht 1 und Zielschacht 2 ist eine Bohrung vorgetrieben worden. Das Bohrgestänge ist als Gefrier-Arbeitsrohr ausgebildet und verbleibt daher nach Durchführung der Bohrung im Bohrloch 5. Das Gefrier-Arbeitsrohr 6 besteht im Ausführungsbeispiel aus mehreren Teilstükken 6', die z. B. über ein Außengewinde mittels geeigneter Muffen mit Innengewinden miteinander verbunden sind und auf ihrer Außenseite eine Zahnstange tragen. In das Gefrier-Arbeitsrohr wird ein verschiebbares Innenrohr 7 eingeführt. Dieses Innenrohr dient zur abschnittsweisen Vereisung des Erdreiches um das Gefrier-Arbeitsrohr zwischen Start- und Zielschacht und besitzt an seiner in der Skizze dargestellten Spitze einen Durchmesser, der größer ist als in seinem übrigen Bereich. Das übrige Innenrohr erstreckt sich zwischen der Innenrohrspitze und beispielsweise dem Zielschacht 2. Beidseitig des Innenrohrbereiches mit großem Durchmesser sind zwei Gummidichtungen 8, 9 entlang des Umfanges des Innenrohres angeordnet. Diese Gummidichtungen können mittels Druckluft so verformt werden, daß sie an der Innenwand des Gefrier-Arbeitsrohres anliegen und einen wasserdichten Kontakt herstellen. In dem Raum 10 zwischen Innenrohr und Gefrier-Arbeitsrohr 6 bzw. zwischen den Dichtungen 8, 9 wird nun Wasser eingeleitet und anschließend ein verflüssigtes, tiefsiedendes Gas (im Ausführungsbeispiel flüssiger Stickstoff) in das Innenrohr eingeleitet. Im indirekten Wärmetausch gefriert das durch die Gummidichtungen eingeschlossene Wasser im•Ringreum 10 und stellt dadurch eine gute Wärmebrücke zwischen dem Gefrier-Arbeitsrohr 6 und dem Erdreich bzw. dem Innenrohr 7 her. Zum Verschieben des Innenrohres wird der Ringraum 10 durch warmes Wasser oder Dampf aufgetaut, die Luft aus den Dichtungen 8 und 9 abgelassen und das Innenrohr vom Zielschacht 2 her verschoben. Im Zielschacht befindet sich ein Einspeisekopf 11 über den flüssiger Stickstoff, der z. B. aus einem Vorratstank 12 entnommen und über Leitung 13, die vakuumisoliert sein kann, zum Einspeisekopf 11 geleitet worden ist, in das Innenrohr 7 eingeleitet wird. Der im Wärmetausch mit dem Erdreich verdampfte Stickstoff wird über das Innenrohr, den Einspeisekopf sowie eine Leitung 18 abgeführt und an die Umgebung abgegeben. Vom Zielschacht 2 her werden auch die erforderliche Luft bzw. das Wasser zur Innenrohrspitze geleitet.

An exemplary embodiment of the method according to the invention with a freezer working tube is to be explained below with the aid of a schematic sketch:

• To create a tunnel, a starting shaft 1 with shaft wall 3 and a target shaft 2 with shaft wall 4 have been excavated. A hole has been drilled between the start shaft 1 and the target shaft 2. The drill pipe is designed as a freezing working tube and therefore remains in the borehole 5 after the bore has been drilled. In the exemplary embodiment, the freezing working tube 6 consists of a plurality of partial pieces 6 'which, for. B. are connected to each other via an external thread by means of suitable sleeves with internal threads and carry a toothed rack on their outside. A displaceable inner tube 7 is inserted into the freezing working tube. This inner pipe is used for section-by-section icing of the soil around the freezer work pipe between the start and finish shafts and has a diameter at its tip shown in the sketch which is larger than in its remaining area. The rest of the inner tube extends between the inner tube tip and, for example, the target shaft 2. Two rubber seals 8, 9 are arranged on both sides of the inner tube region with a large diameter along the circumference of the inner tube. These rubber seals can be deformed by means of compressed air so that they rest on the inner wall of the freezer work tube and make a watertight contact. Water is then introduced into the space 10 between the inner tube and the freezing working tube 6 or between the seals 8, 9, and then a liquefied, low-boiling gas (liquid nitrogen in the exemplary embodiment) is introduced into the inner tube. In indirect heat exchange, the water enclosed by the rubber seals freezes in the • ring area 10 and thereby creates a good thermal bridge between the freezing working pipe 6 and the ground or the inner pipe 7. To move the inner tube, the annular space 10 is thawed by warm water or steam, the air is discharged from the seals 8 and 9 and the inner tube is moved from the target shaft 2. In the target shaft there is a feed head 11 via the liquid nitrogen, which, for. B. removed from a storage tank 12 and has been passed via line 13, which may be vacuum insulated, to the feed head 11, is introduced into the inner tube 7. The nitrogen evaporated in the heat exchange with the ground is discharged via the inner tube, the feed head and a line 18 and released into the environment. From the target shaft 2, the required air or water is also directed to the inner tube tip.

On the side of the inner tube tip facing the starting shaft, a device 14 is attached, with which the position of the inner tube and thus the area to be frozen can be determined.

First, the area immediately adjacent to the starting shaft is frozen. If a frost body with a sufficiently large diameter D, which is larger than the diameter d of the planned tunnel, has formed around the freezing working pipe, the dismantling of the first section can begin. In the exemplary embodiment, a rotating jacking device 15 is to be used, which rotates around the freezing working tube and has a diameter corresponding to the planned tunnel diameter. In order to set the propulsion device in rotation and in forward movement, a drive is provided which is supported against the freezing working tube. The drive device 15 is cyclically guided towards the ice / earth material body by drive 16. Immediately after dismantling, segments 17 can be moved to secure the tunnel. For this, z. B. is used around the axis of the propulsion device rotatable crane arm (erector). The space between the expansion and the soil is pressed out with cement mortar. At this point at the latest, the inner pipe is moved to the next tunnel section and the surrounding soil frozen. According to the invention, the icing must always lead the dismantling to such an extent that there is sufficient abutment for the freezing working tube to absorb the reaction forces caused by the drive 11.

• 1. ein von der Tiefenlage des Tunnels unabhängiger Vortrieb möglich ist,
• 2. ein abzubauender Baugrund geschaffen wird, der aufgrund seiner Gleichmäßigkeit gezielt und ohne technische Schwierigkeiten abgebaut werden kann,
• 3. ein sicherer, temporärer Verbau bis zur Einbringung einer Sicherung gegeben ist,
• 4. nur ein geringer Aufwand an Geräten vorort erforderlich ist,
• 5, ein störungsarmer und reparaturfreundlicher Betrieb möglich ist,
• 6. nur eine sehr einfache Überwachung erforderlich ist, wodurch ein hoher Sicherheitsfaktor erreicht wird und
• 7. ohne Druckluft und Bauhilfsmaßnahmen umweltfreundlich im Grundwasser gearbeitet werden kann.

In summary, it can be stated that the procedure according to the invention

• 1. tunneling is possible regardless of the depth of the tunnel,
• 2. a building ground to be dismantled is created which, due to its uniformity, can be removed in a targeted manner and without technical difficulties,
• 3. there is a safe, temporary installation until a safety device is installed,
• 4. only a small amount of equipment is required on site,
• 5, trouble-free and repair-friendly operation is possible,
• 6. only a very simple monitoring is required, whereby a high safety factor is achieved and
• 7. You can work in an environmentally friendly manner in groundwater without compressed air and construction measures.

Claims (8)

1. A method of constructing a tunnel between a starting shaft and an objective shaft (1 and 2) by ground freezing, characterised in that between the starting shaft and the objective shaft within the cross-sectional area of the planned tunnel, a bore (5) is driven into or in the vicinity of the planned axis of the future tunnel, a freezing working pipe (6) is inserted into the bore hole formed, the freezing working pipe is cooled by a coolant until a frozen mass having a larger diameter (D) than the diameter (d) of the planned tunnel has been formed around the freezing working pipe, and the frozen earth is subsequently removed.

2. A method as claimed in claim 1, characterised in that the frozen mass is produced section- wise.

3. A method as claimed in one of claims 1 or 2, characterised in that as coolant, brine or a cooling liquid, e. g. a low-boiling, liquefied gas, in particular liquid nitrogen, is used.

4. A method as claimed in one of claims 1 to 3, characterised in that the boring rods are designed as a freezing working pipe.

5. A method as claimed in one of claims 1 to 4, characterised in that in large tunnel cross-sections for the subsequent tunnel cross-section, a plurality of bores are driven between the starting and the objective shaft and a freezing working pipe (6) is inserted into each borehole.

6. A method as claimed in one of claims 1 to 5, characterised in that the frozen earth is removed by means of one (a plurality of) removing device(s) (16) which is (are) supported on a freezing working pipe (6).

7. A method as claimed in claim 6, characterised in that the removing device (15) consists of hammers, chisels, cutters or combined tools, or is a hydraulic or thermal removing device.

8. A method as claimed in claim 6, characterised in that the removing device (15) consists of a device which rests, or moves, e. g. rotates, around the freezing working pipe (6), in the radial direction and which moves rhythmically or continuously in the axial direction of the freezing working pipe.

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