Injection system and tunnel excavation method

Abstract

To effectively inject additives into target materials during shield tunnel construction.SOLUTION: Injection systems 10A, 10B are applied to a shield tunneling machine 30, which includes a skin plate 31, a cutterhead 40 mounted at the front end of the skin plate 31 in the excavation direction, and a bulkhead 50 positioned within the skin plate 31 behind the cutterhead 40, and inject additives into a target area located in front of the bulkhead 50 and / or outside the skin plate 31. The systems include generating means 11 for generating microbubble water containing microbubbles, liquid preparation means 13, 14 for preparing a microbubble-containing additive by mixing the microbubble water generated by the generating means 11 with raw additive material, and injection means 20, 25, 26, 27, 28, and P for injecting the microbubble-containing additive prepared by the liquid preparation means 13, 14 into the target area.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an injection system and a tunnel excavation method, and in particular to a technique suitable for shield tunnel construction using a shield machine. [Background technology]

[0002] For example, Patent Document 1 discloses a technology for increasing the fluidity of excavated soil by injecting ultra-fine bubble water as an additive into the excavated soil filled in the chamber of a shield tunneling machine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-84444 Summary of the Invention [Problem to be solved by the invention]

[0004] In shield tunnel construction using an earth pressure shield machine, excavation additives made from mineral-based (bentonite, clay, etc.) or polymer-based raw materials are sometimes injected into the excavated soil in the chamber to ensure the excavated soil has adequate plastic flow and water-tightness. For the excavated soil in the chamber to have adequate plastic flow and water-tightness, it is desirable for the excavation additives to penetrate evenly into the gaps between the soil particles in the excavated soil and create a uniformly mixed, homogeneous mud. However, mixing the excavation additives alone with the mixing blades attached to the cutter head, etc., is difficult, resulting in variations in the properties of the excavated soil.

[0005] Furthermore, in shield tunnel construction, if the soil being excavated is clayey or the like, the excavated soil will adhere to the cutter head, which can lead to a decrease in excavation efficiency. Therefore, to ensure the plastic flow of the excavated soil in the chamber while preventing soil from adhering to the cutter head, it is necessary to inject anti-adhesion materials such as dispersants and permeation materials into the tunnel face in addition to the excavation additive, which poses the problem of increasing labor and construction costs.

[0006] Furthermore, in shield tunnel construction, in order to suppress vibrations and other issues caused by friction between the skin plate (outer shell) and the ground when the shield machine is excavating, a lubricant that reduces friction resistance may be injected into the ground outside the skin plate. Mineral-based (bentonite, clay, etc.) or polymer-based raw materials are used for such lubricants. However, because the lubricant has low permeability into the ground, the lubricant is injected only partially into the ground, which creates the problem of not being able to fully reduce friction.

[0007] The technology disclosed herein has been made in consideration of the above circumstances, and aims to effectively inject additives into the target during shield tunnel construction. [Means for solving the problem]

[0008] The injection system of the present disclosure comprises: An injection system (10A, 10B) is applied to a shield machine (30) including a cylindrical skin plate (31), a cutter head (40) provided at the front end of the skin plate (31) in the excavation direction, and a partition wall (50) arranged rearward of the cutter head (40) within the skin plate (31) and facing the cutter head (40) at a distance from the cutter head (40), and the injection system injects an additive into an injection target located in front of the partition wall (50) and / or outside the skin plate (31), A generating means (11) for generating fine bubble water containing fine bubbles; a liquid preparation means (13, 14) for preparing a liquid of a microbubble-containing additive containing microbubbles by kneading the microbubble water generated by the generation means (11) with a raw material of the additive; and an injection means (20, 25, 26, 27, 28, P) for injecting the microbubble-containing additive prepared by the liquid preparation means (13, 14) into the object to be injected. It is characterized by:

[0009] In another aspect of the infusion system of the present disclosure, The liquid preparation means (13) prepares a liquid of a microbubble-containing excavation additive containing microbubbles by kneading raw materials used for an excavation additive that improves the fluidity of excavated soil and sand with the microbubble water, The injection means (20, 25, P) injects the microbubble-containing excavation additive into the excavated soil filled in the chamber (55) between the cutter head (40) and the partition wall (50). It is characterized by:

[0010] In another aspect of the infusion system of the present disclosure, The liquid preparation means (13) prepares a liquid of a microbubble-containing excavation additive containing microbubbles by kneading raw materials used for an excavation additive that improves the fluidity of excavated soil and sand with the microbubble water, The injection means (20, 26, 27, P) injects the microbubble-containing drilling additive into the face in front of the cutter head (40). It is characterized by:

[0011] In another aspect of the infusion system of the present disclosure, The liquid preparation means (14) prepares a liquid of a microbubble-containing lubricant containing microbubbles by kneading raw materials used for the lubricant that reduces friction of the natural ground with the microbubble water, The injection means (20, 28, P) injects the microbubble-containing lubricant into the natural ground outside the skin plate (31). It is characterized by:

[0012] In the injection system of the present disclosure, The fine bubbles are ultrafine bubbles with a diameter of less than 1 μm or fine bubbles with a diameter of 1 μm or more and less than 100 μm. It is desirable.

[0013] The tunnel excavation method of the present disclosure comprises: A tunnel excavation method using a shield machine (30) including a cylindrical skin plate (31), a cutter head (40) provided at the front end of the skin plate (31) in the excavation direction, and a partition wall (50) arranged rearward of the cutter head (40) within the skin plate (31) and facing the cutter head (40) at a distance from the cutter head (40), Generates fine bubble water containing fine bubbles, The resulting microbubble water is mixed with raw materials for an additive to prepare a microbubble-containing additive containing microbubbles; The prepared microbubble-containing additive is injected into the target on the front side of the partition wall (50) and / or on the outside of the skin plate (31). It is characterized by:

[0014] In the above description, to aid in understanding the present disclosure, the symbols used in the embodiments are added in parentheses to components corresponding to the embodiments, but each component is not limited to the embodiment defined by the symbol. [Effects of the Invention]

[0015] According to the injection system and tunnel excavation method of the present disclosure, additive material can be effectively injected into the target during shield tunnel construction. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic vertical cross-sectional view showing a shield tunneling machine to which an injection system according to a first embodiment is applied. [Figure 2] FIG. 2 is a schematic front view showing the cutter head of the shield machine according to the first embodiment. [Figure 3] FIG. 10 is a schematic vertical cross-sectional view showing a shield machine to which an injection system according to a second embodiment is applied. [Figure 4] 10 is a schematic cross-sectional view of a skin plate provided in a shield tunneling machine to which an injection system according to a second embodiment is applied. FIG. [Figure 5] 10A and 10B are diagrams illustrating the results of a test to confirm the effect of reducing fluid resistance. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the injection system and tunnel excavation method according to the present embodiment will be described with reference to the accompanying drawings. This article explains:

[0018] [First embodiment] FIG. 1 is a schematic vertical cross-sectional view showing a shield machine 30 to which an injection system 10A according to a first embodiment is applied.

[0019] The shield machine 30 constructs a shield tunnel T by assembling multiple segments S on the inner wall of a borehole excavated in the natural ground. Hereinafter, the excavation direction of the shield machine 30 will be referred to as the "forward" direction, and the direction opposite to the excavation direction will be referred to as the "rear" direction.

[0020] The shield tunneling machine 30 comprises a cylindrical skin plate (outer shell) 31, a cutter head 40 arranged at the front end of the skin plate 31, and a partition wall 50 arranged behind the cutter head 40 within the skin plate 31 and facing the cutter head 40 at a distance.

[0021] The rotary joint 41 of the cutter head 40 is rotatably supported by the partition wall 50 via a bearing or the like (not shown). In addition, the rotating ring 32 is rotatably supported by the partition wall 50 via a bearing or the like (not shown). The rotating ring 32 is connected to the cutter head 40 via a connecting beam 33 so as to be rotatable integrally with the cutter head 40.

[0022] A plurality of drive motors 35 capable of transmitting rotational force to the rotating ring 32 via a gear mechanism (not shown) or the like are provided inside the skin plate 31. When the rotating ring 32 is rotated by the rotational power of the drive motors 35, the cutter heads 40 rotate while pressed against the natural ground, thereby excavating the natural ground.

[0023] A chamber 55 is defined between the cutter head 40 and the partition wall 50 inside the skin plate 31. The excavated earth and sand excavated by the cutter head 40 is filled into the chamber 55 through an opening 49 (see Figure 2) in the cutter head 40. The shield machine 30 is a so-called mud pressure shield machine that generates mud pressure by filling the chamber 55 with excavated earth and excavating, and excavates with this mud pressure counteracting the earth pressure at the face.

[0024] An excavation additive mixed with ultra fine bubbles (hereinafter, UFB) (hereinafter, UFB-containing excavation additive) is injected into the excavated soil in chamber 55 by injection system 10A, which will be described later. For this purpose, partition wall 50 is provided with injection port 25 connected to injection piping 20 of injection system 10A. The UFB-containing excavation additive turns the excavated soil in chamber 55 into mud in a plastic flow state.

[0025] A screw conveyor 60, a jack 64, and an erector 68 are provided behind the partition wall 50 within the skin plate 31. The screw conveyor 60 opens at the lower end side of the partition wall 50. The cutter head 40 is provided with an agitating blade 56A that rotates integrally with the cutter head 40. The partition wall 50 is provided with an agitating blade 56B fixed to the partition wall 50. The mud agitated by the agitating blades 56A and 56B is discharged behind the shield machine 30 by the screw conveyor 60.

[0026] A plurality of jacks 64 are arranged at predetermined intervals circumferentially on the inner surface of the skin plate 31. The jacks 64 cause the shield machine 30 to excavate forward by taking reaction force from the existing segments S. The erector 68 holds the segments S and rotates circumferentially, thereby assembling the segments S into a ring shape.

[0027] 1 indicates the backfill material injected between the outer periphery of the segment S and the inner wall of the excavation hole using a backfill injection device (not shown) through an injection port 28 provided in the skin plate 31. A tail seal 69 is provided on the rear end side of the skin plate 31 to prevent the backfill material BM, groundwater, etc. from seeping in through the gap between the skin plate 31 and the existing segment S.

[0028] [Cutter head] The cutter head 40 includes an outer ring 42, an inner ring 43, a central cylindrical portion 44, a plurality of cutter spokes 45, a center cutter 46, a plurality of cutter bits 47, and a plurality of auxiliary cutter spokes 48 (see FIG. 2). Note that the inner ring 43 and the auxiliary cutter spokes 48 may not be included depending on the diameter of the cutter head 40, etc.

[0029] The outer ring 42 is formed in a ring shape with approximately the same diameter as the skin plate 31. The inner ring 43 is formed in a ring shape with a smaller diameter than the outer ring 42. The central cylinder portion 44 is formed in a cylindrical shape with both ends closed. The outer ring 42, inner ring 43, and central cylinder portion 44 are arranged concentrically. The connecting beam 33 is connected to the rear end of the inner ring 43.

[0030] A rotary joint 41 is connected to the rear surface of the central cylinder 44. Cutter spokes 45 are connected to the outer circumferential surface of the central cylinder 44. The central cylinder 44, rotary joint 41, and cutter spokes 45 are formed hollow, and an injection pipe 20 (described later) and the like are disposed inside them.

[0031] As shown in FIG. 2, a plurality of cutter spokes 45 are arranged radially from the central tube portion 44 to the outer ring 42. A plurality of cutter bits 47 are attached to the front and side surfaces of the cutter spokes 45. A plurality of auxiliary cutter spokes 48 are arranged at approximately midpoints between adjacent cutter spokes 45 in the circumferential direction. The auxiliary cutter spokes 48 are arranged from the inner ring 43 to the outer ring 42. A plurality of openings 49 are formed between the outer ring 42, the inner ring 43, the cutter spokes 45, and the auxiliary cutter spokes 48 to allow excavated earth and sand to pass through. The number of cutter spokes 45 and auxiliary cutter spokes 48 is not limited to the illustrated example, and can be any number appropriate depending on the diameter of the cutter head 40, etc.

[0032] Injection ports 26 are provided on the front faces of the cutter spokes 45 (one for each of the four cutter spokes 45 in the illustrated example). One injection port 27 is provided on the front face of the center cutter 46. Each injection port 26, 27 is connected to the injection pipe 20 (see FIG. 1) of the injection system 10A. By injecting the UFB-containing excavation additive into the face through the injection ports 26, 27, it is possible to effectively prevent excavated soil from adhering to the cutter spokes 45, the center cutter 46, and the auxiliary cutter spokes 48 without the need for a separate anti-adhesion agent. The number of injection ports 26, 27 is not limited to the illustrated example and can be any number appropriate depending on the diameter of the cutter head 40 and the soil properties of the ground to be excavated. Furthermore, the location of the injection ports 26 is not limited to the front faces of the cutter spokes 45, but can also be provided on the side faces of the cutter spokes 45 or the front or side faces of the auxiliary cutter spokes 48.

[0033] [Injection System] Referring again to FIG. 1, the injection system 10A according to the first embodiment will be described in detail.

[0034] 1, injection system 10A includes UFB water generator 11 that generates UFB water, water supply pipe 12 that supplies tap water to UFB water generator 11, drilling additive preparation unit 13 that prepares a UFB-containing drilling additive, UFB water supply pipe 15 that supplies UFB water from UFB generator 11 to drilling additive preparation unit 13, injection pipe 20 that supplies UFB-containing drilling additive from drilling additive preparation unit 13 to each injection port 25, 26, 27, and pump device P provided on injection pipe 20. For convenience of illustration, injection system 10A is shown inside shield tunnel T, but UFB water generator 11, water supply pipe 12, drilling additive preparation unit 13, etc. can also be installed outside the tunnel.

[0035] The UFB water generator 11 generates UFB water by generating UFB in water supplied from the water supply pipe 12. Here, UFB refers to fine bubbles with a diameter of less than 1 μm, for example. The water supplied to the UFB water generator 11 is not limited to tap water, and water stored in a water storage tank installed on-site can also be supplied. In this case, the water can be supplied by pumping it up from the water storage tank using a pump.

[0036] The excavation additive preparation unit 13 prepares a UFB-containing excavation additive by mixing the excavation additive raw materials with UFB water. Mineral-based (bentonite, clay) or polymer-based raw materials can be used as the excavation additive raw materials. The UFB-containing excavation additive prepared by the excavation additive preparation unit 13 is injected through the injection pipe 20 from the injection port 25 into the excavated soil in the chamber 55, and from the injection ports 26 and 27 into the face in front of the cutterhead 40. For convenience, the injection pipe 20 is shown as a branch pipe with multiple branches on the downstream side connected to the injection ports 25, 26, and 27. However, multiple injection pipes 20 may be configured to be connected in parallel to the injection ports 25, 26, and 27, respectively. In this case, a pump device P may be provided for each of the multiple injection pipes 20.

[0037] According to the injection system 10A of the first embodiment described above in detail, UFB water produced in the UFB water generator 11 is supplied to the excavation additive preparation unit 13, and the raw materials for the excavation additive are mixed with the UFB water in the excavation additive preparation unit 13 to prepare a UFB-containing excavation additive in which the UFB is uniformly mixed throughout the excavation additive. The UFB-containing excavation additive prepared in the excavation additive preparation unit 13 is injected sequentially from the injection ports 25, 26, and 27 through the injection piping 20 into the excavated soil in the chamber 55 and into the face in front of the cutterhead 40 during tunnel excavation.

[0038] When UFB-containing excavation additive, in which UFB is evenly mixed throughout, is injected into the excavated soil in chamber 55, the surfactant properties of the UFB effectively reduce fluid resistance, allowing the excavation additive to more easily penetrate into the gaps between the soil particles in the excavated soil, compared to when an excavation additive without UFB is injected. In other words, the excavated soil in chamber 55 can be made into a homogeneous mud in which the excavation additive is mixed throughout. As a result, compared to conventional methods in which an excavation additive without UFB is injected, the plastic flow properties and water cutoff properties of the excavated soil in chamber 55 can be reliably improved, enabling effective stabilization of the tunnel face during excavation.

[0039] Furthermore, when a UFB-containing excavation additive with UFB evenly mixed throughout is injected into the face in front of the cutter head 40, the surface-active properties of the UFB reduce fluid resistance, making it easier for the excavation additive to penetrate into the gaps between the soil particles in the excavated soil excavated by the cutter bit 47. This means that the excavation additive can be evenly dispersed and injected across the entire face. Furthermore, the surface-active properties of the UFB create a bearing effect, effectively preventing sediment adhesion to the cutter head 40. This means that sediment adhesion to the cutter head 40 can be prevented without the need for additional anti-adhesion materials, minimizing increases in labor and construction costs while also effectively preventing a decline in excavation efficiency due to sediment adhesion.

[0040] [Second embodiment] 3 is a schematic diagram illustrating an injection system 10B according to the second embodiment. The shield machine 30 to which the injection system 10B of the second embodiment is applied is similar to that of the first embodiment, and therefore a description of the shield machine 30 will be omitted.

[0041] The injection system 10B according to the second embodiment includes a UFB water generator 11, a water supply pipe 12, a lubricant preparation unit 14 that prepares a lubricant containing UFB (hereinafter referred to as UFB-containing lubricant), a UFB water supply pipe 15, an injection pipe 21 that supplies the UFB-containing lubricant from the lubricant preparation unit 14 to each injection port 28, and a pump device P provided on the injection pipe 21. The UFB water generator 11, the water supply pipe 12, the UFB water supply pipe 15, and the pump device P have the same configuration as those in the first embodiment, and therefore detailed description thereof will be omitted.

[0042] The lubricant preparation unit 14 prepares a UFB-containing lubricant by kneading the lubricant raw materials with UFB water. Mineral-based (bentonite, clay) or polymer-based lubricant raw materials can be used as the lubricant raw materials. The UFB-containing lubricant prepared by the lubricant preparation unit 14 is sequentially injected into the natural ground outside the skin plate 31 through each injection port 28 via the injection pipe 20. For convenience, the injection pipe 20 is shown as a branch pipe whose downstream side branches into multiple pipes connected to each injection port 28. However, multiple injection pipes 20 may be configured to be connected in parallel to each injection port 28. In this case, a pump device P may be provided for each of the multiple injection pipes 20.

[0043] FIG. 4 is a schematic cross-sectional view of a skin plate 31 provided in a shield machine 30. The skin plate 31 has multiple injection ports 28 arranged at a predetermined pitch around the circumferential direction. The injection pipes 20 are connected to the injection ports 28 at the locations where vibrations are occurring as the shield machine 30 advances. In the illustrated example, vibrations occur at two locations, top and bottom, of the skin plate 31, and the injection pipes 20 are connected to the two injection ports 28 at the top and bottom. If vibrations are occurring in other locations (for example, the side), the injection pipes 20 can be connected to the injection ports 28 corresponding to those locations. If vibrations are occurring around substantially the entire circumference of the skin plate 31, the number of injection pipes 20 can be increased, and the injection pipes 20 can be connected to four injection ports 28, for example, at the top, bottom, left, and right.

[0044] According to the injection system 10B of the second embodiment described above in detail, UFB water produced in the UFB water generator 11 is supplied to the lubricant preparation unit 14, where the lubricant raw materials and the UFB water are mixed together to produce a UFB-containing lubricant in which UFB is uniformly mixed throughout the lubricant. The UFB-containing lubricant produced in the lubricant preparation unit 14 is injected sequentially from each injection port 28 through the injection piping 20 into the natural ground outside the skin plate 31 during tunnel excavation.

[0045] When a UFB-containing lubricant with UFB evenly mixed throughout is injected into the natural ground outside the skin plate 31, the surfactant properties of the UFB effectively reduce fluid resistance compared to when a lubricant without UFB is injected. When such a UFB-containing lubricant is injected into the natural ground outside the skin plate 31, the UFB-containing lubricant easily penetrates into a wide area of the natural ground surrounding the skin plate 31. As a result, friction between the skin plate 31 and the natural ground can be reliably reduced, and vibration generation can be effectively suppressed, compared to conventional construction methods that inject lubricants without UFB. Furthermore, the thrust required for the shield machine 30 during excavation can be reduced, improving construction efficiency and productivity.

[0046] [Confirmation test] A test was conducted to confirm the effect of reducing fluid resistance obtained by mixing a mineral additive (bentonite) with UFB water. Table 1 shows the details of the samples used in the test. Sample 1 is an example of the present invention, in which a mineral additive (80 kg / m3) was mixed with UFB water (785 kg / m3). Sample 2 is a comparative example of the present invention, in which a mineral additive (80 kg / m3) was mixed with normal water (785 kg / m3) that did not contain UFB.

[0047] [Table 1]

[0048] In the confirmation test, the specific gravity, funnel viscosity, and B-type viscosity of each sample 1 and 2 were measured. The funnel viscosity was measured by putting samples 1 and 2 into a funnel-shaped funnel viscometer and measuring the time it took for the entire amount to flow down. The B-type viscosity was measured using a B-type viscometer with the rotor rotation speed set to 3 rpm, 6 rpm, 12 rpm, and 30 rpm. The results of the confirmation test are shown in Table 2 and Figure 5.

[0049] [Table 2]

[0050] No difference in specific gravity was observed between Sample 1 and Sample 2. Regarding funnel viscosity, the measurement result for Sample 2 of the comparative example was 92.9 seconds, while the measurement result for Sample 1 of the example was 73.0 seconds. In other words, when the mineral additive was mixed with UFB water, the funnel viscosity was reduced by approximately 21.4% compared to when ordinary water was mixed. Regarding B-type viscosity (yield value), the measurement result for Sample 2 of the comparative example was 10.3 Pa, while the measurement result for Sample 1 of the example was 7.9 Pa. In other words, when the mineral additive was mixed with UFB water, the B-type viscosity (yield value) was reduced by approximately 23.3% compared to when ordinary water was mixed. These results confirm that when the mineral additive was mixed with UFB water, the viscosity of the material was reduced, resulting in a reduction in fluid resistance.

[0051] [others] The present disclosure is not limited to the above-described embodiments, and can be appropriately modified and implemented within the scope of the present disclosure.

[0052] For example, in this specification, the first embodiment and the second embodiment have been described as separate embodiments, but the configurations of the first embodiment and the second embodiment may be combined and implemented.

[0053] Furthermore, the shield machine 30 to which the injection systems 10A and 10B of the present disclosure are applied is not limited to the illustrated mud pressure shield machine, but may also be a mud shield excavator. Specifically, the configuration of injecting the UFB-containing excavation additive into the face in front of the cutter head 40 in the first embodiment and the configuration of the second embodiment can also be applied to a mud shield excavator.

[0054] Furthermore, the technology of the present disclosure is not limited to UFB, and it is also possible to use fine bubbles with a bubble diameter of 1 μm or more and less than 100 μm, for example. [Explanation of symbols]

[0055] 10A, 10B...injection system, 11...UFB water generator, 12...water supply piping, 13...excavation additive liquid production unit, 14...lubricant liquid production unit, 15...UFB water supply piping, 20...injection piping, 25, 26, 27, 28...injection port, P...pumping device, 30...shield tunneling machine, 31...skin plate, 32...rotating ring, 33...connecting beam, 35...drive motor, 40...cutter head, 41...rotary joint, 42...outer ring, 43...inner ring, 44...center tube, 45...cutter spokes, 46...center cutter, 47...cutter bit, 48...auxiliary cutter spokes, 49...opening, 50...partition wall, 55...chamber, 60...screw conveyor, 64...jack, 68...erector, 69...tail seal, S...segment, BM...backfill material

Claims

1. An injection system that is applied to a shield machine including a cylindrical skin plate, a cutter head provided at the front end of the skin plate in the excavation direction, and a partition wall arranged rearward of the cutter head in the skin plate and facing the cutter head at a distance, and that injects an additive into an injection target located in front of the partition wall and / or outside the skin plate, A generating means for generating fine bubble water containing fine bubbles; a liquid preparation means for preparing a microbubble-containing additive containing microbubbles by kneading the microbubble water generated by the generation means with a raw material of the additive; and an injection means for injecting the microbubble-containing additive prepared by the liquid preparation means into the target. An injection system comprising:

2. 10. The injection system of claim 1, The liquid preparation means prepares a liquid of a microbubble-containing excavation additive containing microbubbles by kneading raw materials used in an excavation additive that improves the fluidity of excavated soil and sand with the microbubble water, The injection means injects the microbubble-containing excavation additive into the excavated soil filled in the chamber between the cutter head and the partition wall. An injection system comprising:

3. 10. The injection system of claim 1, The liquid preparation means prepares a liquid of a microbubble-containing excavation additive containing microbubbles by kneading raw materials used in an excavation additive that improves the fluidity of excavated soil and sand with the microbubble water, The injection means injects the microbubble-containing drilling additive into the face in front of the cutter head. An injection system comprising:

4. 10. The injection system of claim 1, the liquid preparation means prepares a lubricant containing microbubbles by kneading raw materials used for the lubricant that reduces friction of the natural ground with the microbubble water, The injection means injects the microbubble-containing lubricant into the natural ground outside the skin plate. An injection system comprising:

5. 10. The injection system of claim 1, The fine bubbles are ultrafine bubbles with a diameter of less than 1 μm or fine bubbles with a diameter of 1 μm or more and less than 100 μm. An injection system comprising:

6. A tunnel excavation method using a shield machine including a cylindrical skin plate, a cutter head provided at the front end of the skin plate in the excavation direction, and a partition wall arranged rearward of the cutter head within the skin plate and facing the cutter head at a distance, Generates fine bubble water containing fine bubbles, The resulting microbubble water is mixed with raw materials for an additive to prepare a microbubble-containing additive containing microbubbles; The prepared microbubble-containing additive is injected into an object in front of the partition wall and / or outside the skin plate. A tunnel excavation method characterized by:

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