EP2910733A1 - Foam generator for an earth pressure shield tunnel propulsion machine and method for conditioning removed soil material as a support medium for an earth pressure shield - Google Patents

Abstract

A foam generator (14) for an earth-pressure tunneling machine comprises a mixing chamber having a first inlet port (22) for a foamable fluid and a second inlet port (23) for a gas and a foam exit port (24) connected to the first port (22) A liquid supply device and a gas supply device connected to the second inlet port (23). The mixing chamber includes a tubular flow chamber (28) having the first inlet opening (22) at one end and the foam exit opening (24) at the other end. A portion of the flow chamber (28) is formed as a gassing with a gas-permeable porous wall (26) and adjacent to a second inlet opening (23) having pressure chamber (29) such that through the second inlet port (23) supplied under a pressure Gas enters through the porous wall (26) in the flow chamber (28) and mixes there with the liquid to foam.

Description

The invention relates to a foam generator for a Erddruckschild tunnel boring machine with a mixing chamber having a first inlet opening for a foamable liquid and a second inlet opening for a gas and a foam outlet opening, one connected to the inlet opening for the foamable liquid Flüssigkeitszuführvorrichtung and one with the inlet opening for the gas-connected gas supply device, the mixing chamber having a tubular flow chamber at one end of which the foamable liquid inlet and at the other end the foam discharge orifice, and a method of conditioning excavated soil material as a support medium for an earth pressure shield of a tunnel boring machine removed from the ground and fed to a excavation chamber of the tunnel boring machine, a foam is provided depending on the nature of the excavated soil By providing at least one foam generator having a tubular flow chamber and supplying a foamable liquid to the foam generator at one end of a tubular flow chamber, the foam leaving the other end of the tubular flow chamber is fed to the extraction chamber and mixed with the excavated soil.

A foam generator for an earth pressure tunneling machine and a method for conditioning excavated soil material as a support medium for a Erddruckschild a tunnel boring machine are known from M. Thewe and C. Budach, "Schildvortrieb mit Erddruckschilden: Possibility and Limitations of the Conditioning of the Support Medium", 7th Colloquium Building in Soil and Rock, Technische Akademie Esslingen, 26.-27.01.2010, S. 171-183 ,

In these known foam generators, a surfactant solution is first prepared by mixing water and surfactant, and this surfactant solution is fed to a foam generator where it is mixed with air. The air-surfactant solution mixture is then passed through a flow channel containing contaminants. The disruptive bodies comprise grids arranged transversely to the flow direction and / or glass spheres arranged in the flow cross section between holding sieves. These bluff bodies generate turbulence and thereby foam, which is then passed into the excavation chamber.

The structure and size of the foam bubbles thus produced are more or less random and can not be tailored to the nature of the pending soil.

Further, from the utility model DE 20 2004 015 637 U1 a foam lance is known, in which flows into a tubular flow channel at one end of compressed air and a liquid foaming agent is sprayed onto a transversely arranged air flow baffle plate, then pressed the turbulent air-foaming agent mixture at the other end of the flow tube through a flow channel covering the porous foam generator is, wherein beyond the foam generator, the foam formed enters a housing volume and leaves the housing via an outlet opening.

The invention has for its object to provide a foam generator and a method of the type mentioned above, which allows a vote of structure and size of the foam bubbles produced on the nature of the pending soil and at the same time an admixture of additives, such as solid Ingredients allowed for the foam formed.

This object is achieved by a foam generator for a Erddruckschild tunnel boring machine with the features of claim 1 and a method for conditioning abraded soil material as a support medium for Erddruckschild a tunnel boring machine with the features of claim 10.

The foam generator for an earth pressure plate tunnel boring machine according to the invention comprises a mixing chamber, which has a first inlet port for a foamable fluid and a second inlet port for a gas and a foam exit port, a liquid supply device connected to the inlet port for the foamable fluid and a gas supply device connected to the inlet port for the gas. In addition to a first and a second inlet opening and an outlet opening, further such inlet or outlet openings may also be provided. The mixing chamber has a tubular flow chamber, at one end of which the inlet opening for the foamable liquid and at the other end of which the foam outlet opening is located. This tubular flow chamber basically does not need to have either a constant or a circular cross-section and, moreover, can also be curved. A section of the tubular flow chamber is designed as a gassing section with a gas-permeable porous wall. The section of the tubular flow chamber designed as a gassing section is surrounded by a pressure chamber. The pressure chamber has the inlet opening for the gas and surrounds the portion of the tubular flow chamber formed as Begasungsstrecke such that the supplied through the inlet opening under a pressure gas enters through the gas-permeable porous wall in the tubular flow chamber and there with the foamable liquid to foam mixed. The gas supply device and the liquid supply device are formed so that the pressure of the gas supplied to the pressure chamber can be adjusted so that the pressure is greater than the pressure exerted by the liquid on the gas-permeable porous wall and that a desired ratio of supplied gas to supplied liquid is achieved.

A basic idea of the invention consists of narrow-meshed barriers, such as the lattices, holding sieves or glass bead packs or the porous foam generators known from the aforementioned utility model, from the flow path between the surfactant solution inlet and the foam outlet opening keep out because such close-meshed barriers can become clogged due to particles contained in the solution.

In a preferred embodiment of the method according to the invention, the gas supply device and the liquid supply device are designed so that the pressure of the gas supplied to the pressure chamber can be adjusted so that the pressure 0.5 to 2 bar, preferably 1 to 2 bar, greater than the pressure of Liquid is. This allows sufficient access of air for a desired ratio between foam volume flow and fluid delivery, i. a desired FER (Foam Expansion Ratio).

The pressure chamber can adjoin the flow chamber on one side; Preferably, it surrounds or encloses the flow chamber partially or completely (except for the inlet and outlet ports).

In one embodiment, the section of the tubular flow chamber designed as a gassing section has a constant flow cross-section. Preferably, the portion of the tubular flow chamber also has a circular cross-section. This simplifies the production.

In one embodiment of the foam generator, the section of the tubular flow chamber designed as a gassing section is a hollow cylinder with a gas-permeable porous wall extending between the inlet opening for the foamable liquid and the foam outlet opening. Preferably, the hollow cylinder has a gas-permeable porous wall of constant thickness.

In a preferred embodiment, the gas supplied is air (i.e., compressed air) and the gas supply device is a compressor. In this case, the foamable liquid is a water-surfactant mixture and the liquid supply device comprises a water-surfactant mixing device with which the quantitative ratio of water and surfactant can be adjusted.

In the method according to the invention for conditioning removed soil material as support medium for an earth pressure shield of a tunnel boring machine, soil is removed and a excavation chamber of the tunnel boring machine fed. Depending on the nature of the excavated soil, a foam is provided by providing at least one foam generator with a tubular flow chamber, supplying a foamable liquid to the foam generator at one end of a tubular flow chamber, and a gas flow passage portion of the tubular flow chamber porous gas is supplied to a foaming liquid in the flow chamber with the foamable liquid mixing gas by a pressure chamber which surrounds the gassing section formed section, the gas is supplied under a pressure which is greater than that of the liquid on the gas-permeable porous Wall applied pressure is. In this case - depending on the nature of the removed soil - a foam generator with a Begasungsstrecke a predetermined length, a predetermined flow cross-section and a predetermined pore size and density provided and the ratio of supplied gas is adjusted to supplied liquid, so that a desired structure and size of the foam bubbles. The foam exiting the other end of the tubular flow chamber is fed to the excavation chamber and mixed with the excavated soil.

In a preferred embodiment of the method according to the invention, the gas is supplied to the pressure chamber at a pressure which is 0.5 to 2 bar, preferably 1 to 2 bar, greater than the pressure of the liquid. This allows for a desired ratio between foam volume flow and fluid delivery, i. a desired FER (Foam Expansion Ratio).

In a preferred embodiment of the method according to the invention, the foam is supplied to the excavation chamber at a pressure which is 1 to 2 bar greater than the pressure in the excavation chamber. This allows the injection of desired amounts of foam.

Preferably, the foam emerging from the tubular flow chamber is at several injection sites in the Discharge chamber supplied to achieve a desired distribution of the foam. In this case, the foam emerging from the tubular flow chamber can be supplied to injection sites on a cutting wheel and to a side of a pressure wall facing the excavation chamber. In addition, the foam exiting the tubular flow chamber may be supplied to injection sites in a screw conveyor conveying the excavated soil from the excavation chamber.

In a preferred embodiment of the method for conditioning abraded soil material as a support medium for Erddruckschild a tunnel boring machine, the foam generator at the one end of the tubular flow chamber is supplied together with the foamable liquid, a solid. Preferably, the solid contains a bentonite powder or granules. The advantage of a barrier-free flow through the surfactant solution through the flow channel is utilized.

In a preferred embodiment, the foam generator is provided with a Begasungsstrecke a predetermined length, a predetermined flow cross-section and a predetermined pore size and density depending on the nature of the removed soil by using a selected parameters of the excavated soil serving as Begasungsstrecke hollow cylinder length and predetermined internal cross-section is selected with a gas-permeable porous wall predetermined pore size and density for the foam generator. This allows for easy adaptation of the foam composition to changing soil conditions. The differently shaped, serving as a gassing hollow cylinder can be easily replaced.

Alternatively, in one embodiment, a plurality of gassing sections may be arranged in parallel in terms of flow, in which case a gassing section having the selected parameters is selected from the plurality of gassing sections arranged in parallel with respect to flow, by the supply of Liquid and gas to the other fumigation routes is blocked.

Advantageous and / or preferred embodiments of the invention are characterized in the subclaims.

• Figur 1 eine schematische Darstellung einer Tunnelvortriebsmaschine mit den für die Erfindung wesentlichen Elementen;
• Figur 2 eine schematische Längsschnittansicht eines erfindungsgemäßen Schaumgenerators; und
• Figur 3 eine schematische Querschnittansicht des Schaumgenerators gemäß Figur 2.
• Figur 1 zeigt schematisch einige für die vorliegende Erfindung wesentliche Elemente einer Tunnelvortriebsmaschine 1.

Ein Schneidrad 2 trägt mit Hilfe von Schälmessern und Schneidrollen den Boden an einer Ortsbrust des Tunnels ab. Der abgetragene Boden fällt daraufhin in eine Abbaukammer 3. Die Abbaukammer 3 wird rückseitig von einer Druckwand 4 der Tunnelvortriebsmaschine 1 begrenzt. In der Abbaukammer 3 wird der abgetragene Boden mit Hilfe von Mischflügeln, die sich sowohl am Schneidrad 2 als auch an der Druckwand 4 befinden, durchmischt und üblicherweise mit Konditionierungsmitteln vermengt. Das in der Abbaukammer 3 gebildete Gemisch wird dann mittels einer Förderschnecke 5 aus der Abbaukammer 3 abgezogen und auf ein Förderband 6 zum Abtransport geleitet. Über die Drehzahl der Förderschnecke 5 werden die aus der Abbaukammer 3 abgeführte Menge und somit der nötige Stützdruck geregelt. Der Vortrieb wird über (in Figur 1 nicht dargestellte) hydraulische Vortriebszylinder geregelt, die sich rückseitig an einem zuletzt errichteten Tunnelring abstützen, wobei sich der Tunnelring aus Tübbings genannten Stahlbetonsegmenten zusammensetzt.The invention will be explained with reference to preferred embodiments illustrated in the drawings. In the drawings show:

• FIG. 1 a schematic representation of a tunnel boring machine with the essential elements of the invention;
• FIG. 2 a schematic longitudinal sectional view of a foam generator according to the invention; and
• FIG. 3 a schematic cross-sectional view of the foam generator according to FIG. 2 ,
• FIG. 1 1 schematically shows some elements of a tunnel boring machine 1 essential to the present invention.

A cutting wheel 2 carries with the help of peeling knives and cutting rollers from the ground at a working face of the tunnel. The excavated soil then falls into a excavation chamber 3. The excavation chamber 3 is bounded on the back by a pressure wall 4 of the tunnel boring machine 1. In the excavation chamber 3, the excavated soil is mixed by means of mixing blades, which are located both on the cutting wheel 2 and on the pressure wall 4, and usually mixed with conditioning agents. The mixture formed in the excavation chamber 3 is then withdrawn by means of a screw conveyor 5 from the excavation chamber 3 and passed to a conveyor belt 6 for removal. About the speed of the screw conveyor 5, the amount discharged from the excavation chamber 3 and thus the necessary support pressure are regulated. The propulsion is over (in FIG. 1 not shown) controlled hydraulic jacking cylinder, which are supported on the back of a last-built tunnel ring, wherein the tunnel ring composed of Tuebbings mentioned reinforced concrete segments.

Naturally grown soils often do not have the geological properties that would be required so that only the excavated soil in the excavation chamber serve as a support medium can. Therefore, conditioning agents are added. Currently, water, clays (including bentonite), polymers and foams are used as conditioning agents in earth pressure shields. While water, clays and polymers are mainly used for the conditioning of fine-grained soils, with coarse-grained soils, surfactant foams are usually introduced into the soil-filled decomposition chamber 3 in order to condition it. The surfactant foams usually consist of a large proportion of air, a proportion of water and a small amount of a surfactant.

To prepare the surfactant foams, a surfactant solution is first prepared by combining water and surfactant in a predetermined ratio and mixing them into the surfactant solution. FIG. 1 shows a surfactant solution tank 16, to which a surfactant from a reservoir 17 and water via a line 18 are supplied. The surfactant solution is fed via a line 15 to a foam generator 14. At the same time the foam generator 14 is supplied via a line 19 compressed air. A (in FIG. 1 not shown) control device ensures that the surfactants and the supplied water are mixed in a predetermined ratio and fed to the tank 16 and that the surfactant solution via the line 15 and the compressed air via line 19 in a predetermined ratio and at predetermined pressures the foam generator 14 are supplied.

In the foam generator 14 described in more detail below, a foam is produced from the surfactant solution and the compressed air, which is then fed via a line 8 to a distributor 9. The distributor 9 distributes the foam via lines 10 to injection points 11 in the cutting wheel 2 and via further lines 7 to injection points 12 on the pressure wall 4 as well as injection points 13 in the screw conveyor 5.

A (in FIG. 1 not shown) control device controls the respective injection sites 11, 12 and 13 supplied amounts of foam by a corresponding locations of the arranged in the lines control valves.

FIG. 1 schematically shows only a foam generator 14. In alternative and / or preferred embodiments can also a plurality of foam generators may be provided, which may alternatively be coupled into the flow path and which may also produce different foams. Alternatively, separate foam generators may be provided for the different injection sites, allowing the parameters of the foams injected at the different injection sites to be adapted to the nature of the mixture at the respective injection sites.

During propulsion, the nature of the soil may change, so that the parameters of the foam, such as the ratio of air and liquid or the size of the foam bubbles, may be varied depending on the soil quality detected, until a satisfactory result for propulsion is obtained becomes. By means of preliminary tests, it is possible to determine an optimum pore size of the surfactant foam for a soil composition which is found in each case. On the basis of these experimentally determined relationships, it is then possible to adjust the desired foam parameters, such as the foaming rate FER and the foam pore size, with the help of the foam generator according to the invention described below. In addition, the foam generator 14 according to the invention allows, in addition, a solids content, for example a clay (in particular bentonite), to be added to the surfactant solution fed in via line 15. This is for example the stabilization of loose soil. This option expands the field of application of earth pressure shields.

FIG. 2 shows a schematic longitudinal sectional view of the foam generator according to the invention 14. A housing consists of two housing shells 20, 21, which are pressed together by means of bolts 31, wherein a seal 30 between the housing halves 20 and 21 is arranged. In the FIG. 2 Housing half 21 shown below has an inlet opening 22 into which a surfactant solution can enter. The upper housing shell 20 has a foam outlet opening 24. Inside the Foam generator 14 is between the housing shells 20 and 21, a hollow cylinder 25 with a porous wall 26 arranged such that an end face 27A of the hollow cylinder 25 is tightly against a front wall of the housing shell 21, so that the inflow into the inlet opening 22 surfactant completely into a flow chamber 28th inside the hollow cylinder 25 occurs. On the opposite side, the other end face 27B of the hollow cylinder is also tightly connected to an end face of the housing shell 20, so that the foam emerging from the flow chamber 28 completely exits the outlet opening 24.

If the housing shells 20 and 21 are separated from each other, the hollow cylinder 25 can be used with a porous wall 26 between the housing shells 20 and 21, so that after assembling and tightening the bolts 31, both the hollow cylinder with its end faces 27 A and 27 B at sealing surfaces of Housing shells rests as well as both housing shells are pressed tightly together. Inside the housing shells 20 and 21, a pressure chamber 29 surrounds the hollow cylinder 25. This pressure chamber 29 is connected to an inlet port 23 for compressed air. The compressed air flowing into the pressure chamber 29 via the inlet opening 23 penetrates via the pores of the wall 26 of the hollow cylinder 25 into the flow chamber 28, so that small air bubbles are added to the surfactant solution flowing through the flow chamber 28. This creates a foam that emerges through the outlet opening 24. The pore size of the foam and the ratio between liquid and air, ie the foaming rate, depend on the one hand on the dimensions of the hollow cylinder and the pore size of the wall 26, on the other hand on the pressure ratios, ie the pressure of the air in the pressure chamber 29 and the pressure of the liquid It should be noted that the pressure of the foam at the outlet opening 24 should preferably be 1 - 2 bar above the pressure in the excavation chamber 3 at the inlet opening 22 and the pressure in the associated with the outlet opening 24. The air pressure in the pressure chamber 29 is then between 1 and 2 bar above the Pressure of the surfactant-water mixture at the inlet opening 22. In the usually occurring in the excavation chamber 3 pressures then results in an air pressure in the pressure chamber 29 of 1.5 - 6.5 bar.

FIG. 3 shows a cross-sectional view of the in FIG. 2 In the illustrated embodiment, the two housing halves 20 and 21 are held together with six stud bolts 31. It is in FIG. 3 to recognize the radially flanged to the housing shell 21 nozzle with the air inlet opening 23.

Numerous alternative embodiments are conceivable within the scope of the inventive concept. For example, a plurality of parallelly arranged hollow cylinders with flow chambers 28 may be arranged in the pressure chamber formed by the housing shells 20, 21. It is also conceivable, conversely, for a concentric tube with a porous wall to be arranged inside a cylindrical flow chamber through which the surfactant liquid flows, the compressed air being supplied to the interior of this tube, so that the air is directed outward through the porous wall is pressed into the surrounding flow chamber. In yet another embodiment, the porous walls between one or more pressure chambers and one or more flow chambers may be planar plates, the chambers being disposed in parallel adjacent one another.

Claims (19)

Foam generator (14) for a Erddruckschild tunnel boring machine (1) with
a mixing chamber having a first inlet opening (22) for a foamable liquid and a second inlet opening (23) for a gas and a foam outlet opening (24),
a liquid supply device (15-18) connected to the inlet port (22) for the foamable liquid; and
a gas supply device (19) connected to the inlet port (23) for the gas,
wherein the mixing chamber has a tubular flow chamber (28) at one end of which the inlet opening (22) for the foamable liquid and at the other end of which the foam outlet opening (24) is located,
characterized,
that a portion of the tubular flow chamber (28) is designed as a gas supply Allows with a gas-permeable porous wall (26),
in that the section of the tubular flow chamber (28) designed as a gassing section adjoins a pressure chamber (29),
in that the pressure chamber (29) has the inlet opening (23) for the gas and adjoins the section of the tubular flow chamber (28) that is formed as a gassing path such that the gas supplied under pressure through the inlet opening (23) passes through the gas-permeable porous wall (FIG. 26) enters the tubular flow chamber (28) and mixes there with the foamable liquid to foam, and
that the gas supply device (19) and the liquid supply device (15-18) are formed so that the pressure of the pressure chamber (29) gas supplied can be adjusted so that the pressure greater than that of the Liquid is on the gas-permeable porous wall (26) applied pressure and that a desired ratio of supplied gas is achieved to supplied liquid. Foam generator (14) according to claim 1, characterized in that the gas supply device (19) and the liquid supply device (15-18) are designed so that the pressure of the gas supplied to the pressure chamber (29) can be adjusted so that the pressure is 0, 5 to 2 bar, preferably 1 to 2 bar, greater than the pressure of the liquid. Foam generator according to claim 1 or 2, characterized in that the pressure chamber (29) at least partially surrounds the flow chamber (28). Foam generator according to one of claims 1 to 3, characterized in that the section of the tubular flow chamber (28) designed as a gassing section has a constant flow cross-section. Foam generator according to claim 4, characterized in that the gassing section of the tubular flow chamber (28) has a circular cross-section. Foam generator according to one of claims 1 to 5, characterized in that the section of the tubular flow chamber (28) designed as a gassing section comprises a hollow cylinder (25) with gas-permeable porous material extending between the inlet opening (22) for the foamable liquid and the foam outlet opening (24) Wall (26) is. Foam generator according to claim 6, characterized in that the hollow cylinder (25) has a gas-permeable porous wall (26) of constant thickness. Foam generator according to one of claims 1-7, characterized in that the gas is air and that the gas supply device comprises a compressor. Foam generator according to any one of claims 1-8, characterized in that the foamable liquid is a water-surfactant mixture and in that the liquid supply device (15-18) comprises a water-surfactant mixing device (16) with which the quantitative ratio of water and Surfactant can be adjusted. A method of conditioning abraded soil material as a support medium for an earth pressure shield of a tunnel boring machine, wherein
Soil is removed and fed to a excavation chamber of the tunnel boring machine,
foam is provided depending on the nature of the soil removed, by
at least one foam generator is provided with a tubular flow chamber,
the foam generator at one end of a tubular flow chamber, a foamable liquid is supplied, and
a gas-permeable porous wall is formed in the section of the tubular flow chamber formed as a gassing section through which a gas mixing with the foamable liquid in the flow chamber is foamed by supplying the gas under a pressure to a pressure chamber enclosing the gassing section; which is greater than the pressure exerted by the liquid on the gas-permeable porous wall,
wherein - depending on the nature of the removed soil - a foam generator with a Begasungsstrecke a predetermined length, one predetermined flow cross section and a predetermined pore size and density is provided and the ratio of supplied gas is adjusted to supplied liquid, so as to give a desired structure and size of the foam bubbles,
the foam leaving the other end of the tubular flow chamber is fed to the excavation chamber and mixed with the excavated soil. A method of conditioning according to claim 10, characterized in that the gas is supplied to the pressure chamber at a pressure which is 0.5 to 2 bar, preferably 1 to 2 bar, greater than the pressure of the liquid. A conditioning process according to claim 11, characterized in that the foam is supplied to the excavation chamber at a pressure of 1 to 2 bar greater than the pressure in the excavation chamber. A conditioning process according to any one of claims 10 to 12, characterized in that the foam leaving the tubular flow chamber is fed at several injection sites in the excavation chamber. A method of conditioning according to claim 13, characterized in that the emerging from the tubular flow chamber foam is supplied to injection sites on a cutting wheel and on a side facing the excavation chamber of a pressure wall. A conditioning method according to claim 14, characterized in that the foam emerging from the tubular flow chamber is additionally supplied to injection sites in a conveyor screw conveying the excavated soil from the excavation chamber. A conditioning process according to any one of claims 10-15, characterized in that a solid is fed to the foam generator at one end of the tubular flow chamber together with the foamable liquid. A conditioning process according to claim 16, characterized in that the solid contains a bentonite powder or granules. A conditioning method according to any one of claims 10 to 17, characterized in that the foam generator is provided with a gassing section of a predetermined length, a predetermined flow cross section and a predetermined pore size and density depending on the nature of the excavated soil, by using selected parameters of the excavated soil, a hollow cylinder of predetermined length and predetermined inner cross-section serving as gasification section is selected for the foam generator with a gas-permeable porous wall of predetermined pore size and density. A conditioning method according to claim 18, characterized in that a gassing section with the selected parameters is selected from a plurality of gassing sections arranged in parallel in terms of flow, by blocking the supply of liquid and gas to the other gassing sections.

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