Shield machine and excavation method

Abstract

To provide a shield machine and an excavation method capable of reducing vibration during construction of a shield tunnel.SOLUTION: A shield machine according to one embodiment is a shield machine 1 that excavates underground ground G. The shield machine 1 includes a cutter 2 that rotates about an axis L that extends in an excavation direction, which is a direction in which the shield machine 1 excavates, and an inorganic granular material supplying unit 10 that extends from the axis L toward an outer periphery of the cutter 2 and supplies inorganic granular material M containing stone powder and water to an excavation section S formed on an outer periphery of the cutter 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a shield machine and an excavation method for excavating underground ground. [Background technology]

[0002] Patent Document 1 describes a large-diameter shield tunnel excavation method and a shield excavator. The shield excavator includes a cylindrical skin plate, a cutter device that is provided at the front end of the skin plate and rotates by a drive shaft to excavate the natural ground, and a propulsion jack whose base end is connected to a partition plate provided inside the skin plate. In the excavation method, while the natural ground is excavated by the cutter device, lining segments are assembled along the inner wall of the excavated tunnel, and propulsion force is obtained by applying the reaction force of the propulsion jack to the segments. The excavated soil excavated by the cutter device is transported to the rear of the tunnel by a soil discharge device and discharged to the ground from a standing pile or the like.

[0003] A friction cut is provided behind the cutter device, which extends circumferentially along the outer peripheral surface of the tip of the skin plate. A notch extending circumferentially is formed on the outer peripheral surface of the skin plate located behind the friction cut. The notch is composed of an orthogonal surface perpendicular to the axial direction of the skin plate and an inclined surface extending from the orthogonal surface toward the outer peripheral side of the skin plate. A plurality of injection ports are formed on the inclined surface.

[0004] The injection port is the opening at the tip of the injection pipe, which extends toward the inside of the skin plate. The injection pipe is connected to an injection pump vehicle having a tank. The tank is filled with a lubricant to reduce friction between the skin plate and the inner wall of the borehole. Polymer materials such as urethane and epoxy are used as the lubricant. The lubricant penetrates into gaps formed on the outer surface of the skin plate as the tunneling machine advances, and has the function of reducing the coefficient of friction between the skin plate and the inner wall surface of the borehole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-156888 Summary of the Invention [Problem to be solved by the invention]

[0006] When a shield machine excavates underground ground, vibrations generated by the shield machine may reach the ground surface. After propagating through the ground, the vibrations may be transmitted to houses and other buildings, causing complaints. However, there are currently few concrete methods for effectively reducing vibrations in shield tunnel construction.

[0007] The present disclosure aims to provide a shield machine and an excavation method capable of reducing vibration during shield tunnel construction. [Means for solving the problem]

[0008] (1) A shield machine according to the present disclosure is a shield machine for excavating underground ground. The shield machine includes a cutter that rotates about an axis that extends in the excavation direction, which is the direction in which the shield machine excavates, and an inorganic granular material supply unit that extends from the axis toward the outer periphery of the cutter and supplies inorganic granular material containing stone powder and water to an excavation section formed on the outer periphery of the cutter.

[0009] This shield machine excavates the ground with a cutter that rotates around an axis extending in the excavation direction, which is the direction in which the shield machine excavates. The shield machine has an inorganic granular material supplying section, which supplies inorganic granular material containing stone powder and water to a pre-excavation section formed on the outer periphery of the cutter. Since the inorganic granular material is supplied to the pre-excavation section from the outer periphery of the rotating cutter, the inorganic granular material can be supplied to cover the entire circumference of the skin plate as the shield machine excavates. The inorganic granular material generates negative pressure in the gaps between the soil particles in the ground, and the negative pressure reduces vibrations caused by shear transmitted through the ground. Therefore, the vibrations generated by the shield machine during construction of the shield tunnel can be reduced, and the vibrations can be prevented from reaching the ground surface. Furthermore, since the inorganic granular material is supplied to the pre-excavation section, the material for reducing vibrations can be made environmentally friendly. That is, the inorganic granular material is closer to the natural materials that make up the ground, etc., compared to organic materials such as resins, and therefore the load on the environment can be reduced. Furthermore, inorganic particulate materials have the advantage that they are more stable and less prone to deterioration than organic materials.

[0010] (2) In the above (1), the moisture content of the inorganic granular material may be 20% or more and 28% or less. By having the moisture content of the inorganic granular material be 20% or more, the inorganic granular material can have a suitable fluidity. By having the moisture content of the inorganic granular material be 28% or less, the inorganic granular material can have a suitable viscosity.

[0011] (3) In the above (1) or (2), the inorganic granular material may contain kaolin. Kaolin is composed of kaolinite, a clay mineral with low reactivity, and therefore can be a more stable inorganic granular material.

[0012] (4) In any of the above (1) to (3), the shield machine may further include a lubricant supply unit that supplies lubricant to the pre-excavation portion through a hole formed in the assembled segment. In this case, the inorganic granular material and the lubricant are supplied to the pre-excavation portion, thereby further enhancing the vibration reduction effect of the inorganic granular material.

[0013] (5) A method of excavating underground ground using a shield machine includes rotating a cutter of the shield machine about an axis extending in an excavation direction, which is a direction in which the shield machine excavates, and supplying an inorganic granular material containing stone powder and water to an excavation section formed on the outer periphery of the cutter.

[0014] In this excavation method, as with the previously described shield machine, a cutter rotating about an axis extending in the excavation direction excavates the ground, and inorganic granular material containing stone powder and water is supplied to the excavation section formed on the outer periphery of the cutter. Since the inorganic granular material is supplied to the excavation section from the outer periphery of the rotating cutter, it is possible to supply the inorganic granular material so as to cover the entire circumference of the skin plate as the shield machine excavates. This makes it possible to reduce vibrations caused by shear transmitted through the ground during shield tunnel construction. Since this excavation method uses inorganic granular material, the material for reducing vibrations can be environmentally friendly, and the same effects as those of the previously described shield machine can be obtained. Effect of the Invention

[0015] According to the present disclosure, vibrations can be reduced during shield tunnel construction. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing a shield machine according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a schematic internal structure of the shield machine according to the embodiment. [Diagram 3] FIG. 2 is a perspective view showing a cutter of the shield machine of FIG. 1. [Figure 4] FIG. 2 is a schematic diagram of an inorganic particulate material. [Diagram 5] FIG. 2 is a diagram showing a schematic diagram of inorganic particulate material being supplied to an extra excavation portion. [Figure 6]FIG. 6 is a diagram showing a schematic diagram of a state in which a lubricant is supplied to an overexcavation portion in the state shown in FIG. 5. [Figure 7] FIG. 2 is a schematic diagram showing the filling of inorganic granular material into an excavation section located between a skin plate and the ground. [Figure 8] 1 is a graph showing the relationship between moisture content and viscosity in an inorganic particulate material. [Figure 9] FIG. 2 is a diagram showing a schematic diagram of an experimental apparatus using inorganic particulate materials according to an embodiment and materials according to a comparative example. [Figure 10] 10 is a graph showing the results of the acceleration ratio in the experiment of FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the shield machine and the tunneling method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional ratios and the like are not limited to those shown in the drawings.

[0018] FIG. 1 is a perspective view showing a shield machine 1 according to this embodiment. The shield machine 1 excavates the ground G underground. In the ground G, construction of a large cross-section shield tunnel is carried out. The shield machine 1 has a cutter 2 that rotates around an axis L extending in an excavation direction D1, which is the direction in which the shield machine 1 excavates, and a skin plate 3 that extends from the cutter 2 in a direction D4 opposite to the excavation direction D1 (hereinafter, also referred to as "rear") and has a cylindrical shape. The excavation method according to this embodiment is a shield method for constructing a tunnel using the shield machine 1. In the shield method, the cutter 2 of the shield machine 1 excavates the ground G (underground), and then segments 5 (lining) are sequentially placed.

[0019] For example, the cutter 2 is a circular cutter disk that rotates in a rotation direction D2 around an axis L. FIG. 2 is a diagram showing the internal structure of the shield machine 1. As shown in FIG. 2, the shield machine 1 has a motor 6 that is located behind the cutter 2 and rotates the cutter 2 around the axis L. The motor 6 drives the shaft 2c of the cutter 2, causing the cutter 2 to rotate around the axis L.

[0020] The shield machine 1 has an earth discharge pipe 4 inside the skin plate 3. The earth discharge pipe 4 extends from the cutter 2 into the inside of the skin plate 3. The earth discharge pipe 4 is supplied with earth excavated by the cutter 2, and the earth discharge pipe 4 discharges the earth excavated by the cutter 2 to the outside of the shield machine 1.

[0021] The shield machine 1 has an inorganic granular material supplying section 10 that supplies inorganic granular material M containing stone powder and water to an extra excavation section S formed on the outer periphery 2b of the cutter 2. For example, the inorganic granular material supplying section 10 extends from the axis L toward the outer periphery of the cutter 2. The extra excavation section S indicates a region that extends rearward from the outside in the radial direction D3 of the rotation trajectory of the cutter 2, which has a circular shape.

[0022] Fig. 3 is a perspective view showing the cutter 2. As shown in Fig. 2 and Fig. 3, for example, the inorganic particulate material supply section 10 has a material storage section 11 located inside the skin plate 3, a pipe 12 extending from the material storage section 11 to the cutter 2, and a cutter internal piping 13 extending from the axis L inside the cutter 2 toward the outer periphery 2b of the cutter 2.

[0023] The cutter 2 has, for example, a shaft portion 2c, spokes 2d extending radially from the shaft portion 2c, and a plurality of bits 2f formed on the spokes 2d. The spokes 2d are formed of a plurality of rod-shaped portions 2g extending from the shaft portion 2c, and the bits 2f are formed on each of the rod-shaped portions 2g. Note that the configuration of the cutter 2 is not limited to the above example.

[0024] For example, the cutter internal piping 13 is formed inside any one of the rod-shaped portions 2g. As an example, the cutter internal piping 13 is formed inside two rod-shaped portions 2g extending in opposite directions from the shaft portion 2c. The cutter internal piping 13 has an opening 13b at an outer end of the cutter 2 in the radial direction D3.

[0025] As shown in Figs. 2 to 4, inorganic granular material M is stored in the material storage section 11. In the inorganic granular material M, additives are added to stone powder. This allows the inorganic granular material M to have a low moisture content. The inorganic granular material M has thixotropy. That is, when the inorganic granular material M is subjected to shear stress, its viscosity decreases and it becomes liquid, and when it is not subjected to shear stress, its viscosity is restored. In addition, the inorganic granular material M has high self-filling properties. Therefore, it is possible to fill the inorganic granular material M in the excavation section S formed between the skin plate 3 and the ground G by pouring the inorganic granular material M into the excavation section S formed between the skin plate 3 and the ground G using a squeeze pump or the like.

[0026] When the inorganic granular material M is subjected to shear stress, its dilatancy becomes positive and negative pressure acts inside. When the inorganic granular material M is subjected to shear stress, negative pressure acts inside the inorganic granular material M, so the inorganic granular material M is considered to be a material that is not easily broken. The inorganic granular material M is injected into the outer periphery (outside in the radial direction D3) of the cutter 2 of the shield machine 1 in order to reduce vibrations caused by the shield machine 1. In other words, the inorganic granular material M has the effect of attenuating vibration energy. For example, the inorganic granular material M contains stone powder, water, and a water-reducing agent. For example, the moisture content of the inorganic granular material M is 20% or more and 28% or less.

[0027] As an example, the stone powder is limestone powder (calcium carbonate). Limestone powder is limestone (CaCO 3 For example, 70% or more of the components of the inorganic granular material M are limestone powder having a particle size of 75 μm or less. The void ratio of the inorganic granular material M is, for example, 0.3 or more and 0.6 or less.

[0028] In this case, it is possible to prevent the inorganic granular material M from having too much moisture, and to maintain the thixotropy of the inorganic granular material M. As a more preferred example, 75% or more of the components of the inorganic granular material M are limestone powder having a particle size of 75 μm or less, and the void ratio of the inorganic granular material M is 0.40 or more and 0.55 or less.

[0029] For example, the inorganic particulate material M includes kaolin, which is a clay (ore) containing at least one of kaolinite (kaolinite), tikumite, and nakuruite. Kaolinite contains aluminium silicate (Al 2 O 3 2H 2 O 2SiO 2 When kaolin containing water is kneaded, it becomes plastic, and when it dries, it becomes strong.

[0030] The inorganic granular material M may contain an admixture. In this case, the admixture may account for 0.08% or more and 10% or less of the components of the inorganic granular material M. The admixture may contain, for example, at least one of a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, a retarder, a dispersant, and a thickener.

[0031] The inorganic granular material M may contain inorganic particles, moisture, and admixtures. The inorganic particles constituting the inorganic particles may be inorganic particles that are non-hydraulic substances. The inorganic granular material M may contain at least one of limestone powder, silt, clay, crushed stone, blast furnace slag, and coal ash. For example, the inorganic granular material M is produced by adjusting the mixing ratio of the inorganic particles, admixtures, and moisture.

[0032] As shown in Figures 2 and 5, for example, inorganic granular material M stored in material storage section 11 is supplied to the overexcavation section S by passing through pipe 12 and cutter internal piping 13 and being discharged from opening 13b. The inorganic granular material M is supplied to the overexcavation section S when the shield machine 1 excavates in excavation direction D1 and the cutter 2 rotates. Thus, the inorganic granular material M moves in the opposite direction D4 to the excavation direction D1 relative to the shield machine 1 and flows spirally along the rotation direction D2. Therefore, by supplying the inorganic granular material M to the overexcavation section S from the outer periphery of the cutter 2 when the shield machine 1 excavates and the cutter 2 rotates, the inorganic granular material M can be distributed over almost the entire periphery of the shield machine 1.

[0033] As shown in Fig. 6, the shield machine 1 may have a lubricant supply unit 15 that supplies lubricant K to the pre-excavation portion S. The lubricant supply unit 15 supplies the lubricant K to the pre-excavation portion S, for example, from holes 5b formed in the assembled segments 5. For example, the lubricant K may be an inorganic granular material M. In this case, a thicker vibration-reducing layer made of the inorganic granular material M can be formed in the pre-excavation portion S.

[0034] Next, an example of an excavation method according to this embodiment will be described. As shown in Fig. 1, a shield machine 1 is placed in the ground G underground, and the shield machine 1 excavates the ground G. At this time, the shield machine 1 rotates the cutter 2 about the axis L (step of rotating the cutter). The rotation of the cutter 2 causes the bit 2f to excavate the ground G, and the excavated soil is discharged outside the shield machine 1 via the soil discharge pipe 4. As the ground G is excavated, segments 5 are sequentially placed, and the segments 5 are assembled.

[0035] Then, inorganic granular material M is supplied to the pre-excavation portion S formed on the outer periphery of the cutter 2 (step of supplying inorganic granular material). As described above, the inorganic granular material M moves in the opposite direction D4 to the shield machine 1 and flows spirally along the rotation direction D2. In this way, by rotating the cutter 2 to excavate the ground G and filling the pre-excavation portion S with inorganic granular material M, it is possible to reduce noise and vibrations that occur with the excavation of the ground G.

[0036] Next, the effects and advantages obtained from the shield machine 1 according to this embodiment will be described in more detail. The shield machine 1 excavates the ground G with the cutter 2 that rotates about an axis L extending in the excavation direction D1, which is the direction in which the shield machine 1 excavates. As shown in Fig. 2, the shield machine 1 has an inorganic granular material supplying section 10 that supplies inorganic granular material M containing stone powder and water to an overexcavation section S formed on the outer periphery of the cutter 2. Since the inorganic granular material M is supplied to the overexcavation section S from the outer periphery of the rotating cutter 2, the inorganic granular material M can be supplied to cover the entire circumference of the skin plate 3 as the shield machine 1 excavates.

[0037] The inorganic granular material M generates negative pressure in the gaps between the soil particles in the ground G, and the negative pressure reduces vibrations caused by shearing transmitted through the ground G. For example, the inorganic granular material M is a material with an extremely small void ratio. As shown in FIG. 7, the inorganic granular material M tries to expand due to a positive dilatancy effect caused by the generation of shearing force, for example, and a force that pulls the particles together inside the inorganic granular material M generates negative pressure, and the rigidity of the inorganic granular material M increases. When the rigidity of the inorganic granular material M increases, the inorganic granular material M resists the vibration. That is, the shield machine 1 and the like may vibrate as the shield machine 1 excavates, but the inorganic granular material M can suppress the vibration by resisting the vibration.

[0038] Therefore, the vibration generated by the shield machine 1 during construction of a large cross-section shield tunnel can be reduced, and the vibration can be prevented from reaching the ground surface. Furthermore, since the shield machine 1 supplies the inorganic granular material M to the excavation section S, the material for reducing vibration can be environmentally friendly. That is, compared to organic materials such as resin, the inorganic granular material M is closer to the natural materials that make up the ground G, and therefore the burden on the environment can be reduced. Furthermore, the inorganic granular material M has the advantage of being more stable and less prone to deterioration than organic materials.

[0039] In this embodiment, the moisture content of the inorganic granular material M is 20% or more and 28% or less. When the moisture content of the inorganic granular material M is 20% or more, the inorganic granular material M can have a suitable fluidity. When the moisture content of the inorganic granular material M is 28% or less, the inorganic granular material M can have a suitable viscosity.

[0040] Fig. 8 is a graph showing the relationship between the moisture content and viscosity of inorganic granular material M. As shown in Fig. 8, when the moisture content of inorganic granular material M is 20% or more and 28% or less, the viscosity of inorganic granular material M is 2000 (mPa·S) or more and 12500 (mPa·S) or less.

[0041] When the viscosity of the inorganic granular material M is 2000 (mPa·S) or more and 12500 (mPa·S) or less, the inorganic granular material M has an appropriate fluidity, so that the vibration reducing effect of the inorganic granular material M can be further enhanced. Furthermore, when the relationship between the water content and viscosity of the inorganic granular material M is within the range of right-angled triangle X in the graph of Fig. 8, the vibration reducing effect of the inorganic granular material M becomes more remarkable.

[0042] In this embodiment, the inorganic granular material M contains kaolin. Kaolin is made of kaolinite, a clay mineral with low reactivity, and therefore can be a more stable inorganic granular material.

[0043] In this embodiment, the shield machine 1 further includes a lubricant supply unit 15 that supplies lubricant K to the excavation section S through holes 5b formed in the assembled segments 5. In this case, by supplying the inorganic granular material M and the lubricant K to the excavation section S, the vibration reduction effect of the inorganic granular material M can be further enhanced.

[0044] In the excavation method according to this embodiment, as shown in Fig. 1, a cutter 2 rotating about an axis L extending in an excavation direction D1 excavates the ground G, and an inorganic granular material M containing stone powder and water is supplied to an overexcavation section S formed on the outer periphery of the cutter 2. Since the inorganic granular material M is supplied to the overexcavation section S from the outer periphery of the rotating cutter 2, the inorganic granular material M can be supplied so as to cover the entire periphery of the skin plate 3 as the shield machine 1 excavates. This makes it possible to reduce vibrations caused by shear transmitted through the ground G during construction of a large cross-section shield tunnel. Since this excavation method uses inorganic granular material M, the material for reducing vibrations can be environmentally friendly.

[0045] Next, a shear soil tank experiment for the inorganic granular material M according to the embodiment and the material according to the comparative example will be described. Fig. 9 shows the experimental apparatus A used in the shear soil tank experiment. As shown in Fig. 9, the experimental apparatus A has a soil tank A1 that contains the imitation soil Y and the material Z, an iron plate A2 that constitutes the bottom surface of the soil tank A1 and is movable in the horizontal direction D5, and a vibration exciter A3 that vibrates the iron plate A2 in the horizontal direction D5.

[0046] The steel plate A2 simulates the outer periphery of the shield machine, the simulated soil Y simulates the ground, and the material Z simulates the material supplied between the outer periphery of the shield machine and the ground. The vibration generator A3 vibrates the steel plate A2 that forms the bottom surface of the soil tank A1 at a specific frequency, and the extent to which the vibration transmitted from the steel plate A2 is attenuated at the ground surface was verified.

[0047] The vibration exciter A3 has a vibration exciter body A31 and a connection part A32 that connects the vibration exciter body A31 and the iron plate A2 to each other. Furthermore, the experimental device A has an acceleration sensor A4 located between the vibration exciter body A31 and the connection part A32, an acceleration sensor A5 located between the connection part A32 and the iron plate A2, an accelerometer A6 located on the top surface of the soil tank A1, and an accelerometer A7 located on the top surface of the iron plate A2.

[0048] In the shear soil tank experiment, the iron plate A2 was vibrated using the material Z as the inorganic granular material M according to the embodiment and the materials according to Comparative Examples 1 to 11. The material according to Comparative Example 1 was simulated soil Y, the material according to Comparative Example 2 was aerated mixed soil, the material according to Comparative Example 3 was a urethane foam material, and the material according to Comparative Example 4 was plastic fluidized soil. The material according to Comparative Example 5 was bentonite 70, the material according to Comparative Example 6 was a natural mineral material, and the material according to Comparative Example 7 was highly elastic urethane foam. The material according to Comparative Example 8 was bentonite 140, the material according to Comparative Example 9 was konnyaku, the material according to Comparative Example 10 was a highly water-absorbent resin material, and the material according to Comparative Example 11 was a polymer material.

[0049] As described above, the material Z was the inorganic particulate material M according to the embodiment and the materials according to the comparative examples 1 to 11, and the iron plate A2 was vibrated, and the acceleration ratio was measured. The acceleration ratio indicates the ratio of acceleration when the measured acceleration / input acceleration in the case of the comparative example 1 is set to 1. The smaller the acceleration ratio, the stronger the vibration reduction effect.

[0050] The results of the shear soil tank experiment are shown in Figure 10. As shown in Figure 10, in the cases of Comparative Examples 9 to 11 in which material Z was konjac, a highly water-absorbent resin-based material, or a polymer-based material, the acceleration ratio was higher than when material Z was model soil Y (Comparative Example 1). In contrast, in the cases of Examples and Comparative Examples 1 to 8 in which material Z was inorganic granular material M, aerated soil, urethane foam-based material, plastic fluidized soil, bentonite 70, natural mineral-based material, highly elastic urethane foam, or bentonite 140, the acceleration ratio was lower than when material Z was model soil Y (Comparative Example 1).

[0051] In particular, in the embodiment in which the inorganic granular material M according to the embodiment was used as the material Z, it was found that the acceleration ratio could be reduced to 0.30, and a significant vibration reduction effect could be achieved. In addition, in the case in which the material Z was aerated soil (Comparative Example 2), it was found that the acceleration ratio could be reduced to 0.58, and the second most significant vibration reduction effect could be achieved.

[0052] The above describes the embodiments and examples of the shield machine and tunneling method according to the present disclosure. However, the shield machine and tunneling method according to the present disclosure are not limited to the above-mentioned embodiments or examples, and may be modified within the scope of the gist described in the claims. In other words, the configuration, shape, size, material, number and arrangement of each part of the shield machine, as well as the content and order of the steps of the tunneling method, may be modified as appropriate within the scope of the above gist.

[0053] In the above-described embodiment, the inorganic granular material M is filled in the excavation portion S formed between the skin plate 3 and the ground G. In addition to filling the inorganic granular material M, the operation during construction may be changed to further effectively reduce vibration. Specifically, for example, if there is concern about the occurrence of large vibration, the excavation speed of the shield machine 1 or the rotation speed of the cutter 2 may be slowed down. For example, the jack pressure of the long jack of the shield machine 1 may be reduced before the long jack is fully extended to eliminate the twist of the jack. The rotation direction may be reversed so that the amount of rolling does not become too large. From these measures, a measure that does not slow down the process too much may be appropriately selected.

[0054] In the above-mentioned embodiment, inorganic granular material M is supplied to the excavation section S formed between the skin plate 3 and the ground G. At least one of a mud-adding material, a replacement material, a plasticizer, and a foaming material may be further supplied to the excavation section S. The mud-adding material is, for example, a material mainly made of clay or bentonite to which fine particles that increase the fluidity and water impermeability of the soil and sand are added. The replacement material replaces water with air bubbles in the air bubble shield method to increase the water cutoff properties of the excavated soil. The plasticizer is a substance added to the material to make it flexible or easier to process.

[0055] Moreover, in the above-mentioned embodiment, an example in which the lubricant K is supplied to the overexcavation portion S has been described. However, it is also possible to omit the supply of the lubricant K. Furthermore, in the above-mentioned embodiment, an example in which the inorganic granular material M contains kaolin has been described. However, the inorganic granular material M may be a material that does not contain kaolin. The inorganic granular material M may be a backfilling material. The backfilling material may be cement-based or non-cement-based. The cement-based backfilling material may be a plastic injection agent or a non-plastic injection agent. In this way, the material of the inorganic granular material M can also be changed as appropriate. [Explanation of symbols]

[0056] 1...Shield machine, 2...Cutter, 2b...Outer circumference, 2c...Shaft, 2d...Spoke, 2f...Bit, 2g...Rod-shaped portion, 3...Skin plate, 4...Soil discharge pipe, 5...Segment, 5b...Hole, 6...Motor, 10...Inorganic granular material supply portion, 11...Material storage portion, 12...Pipe, 13...Internal piping of cutter, 13b...Opening, 15...Lubricant supply portion, A...Experimental equipment, A1...Soil tank, A2...Iron plate, A3...Vibrator, A4...Acceleration sensor, A5...Acceleration sensor, A6...Accelerometer, A7...Accelerometer, A32...Connection portion, D1...Excavation direction, D2...Rotation direction, D3...Radial direction, D4...Opposite direction, D5...Horizontal direction, G...Ground, K...Lubricant, L...Axis, M...Inorganic granular material, S...Excavation portion, X...Right triangle, Y...Simulated soil, Z...Material.

Claims

1. A shield machine for excavating underground ground, A cutter that rotates around an axis extending in the excavation direction, which is the direction in which the shield machine excavates; A skin plate extending from the cutter in a direction opposite to the excavation direction and having a cylindrical shape; an inorganic granular material supplying section extending from the axis toward the outer periphery of the cutter and supplying an inorganic granular material including stone powder and water to an excavation section formed on the outer periphery of the cutter; Equipped with Shield machine.

2. The moisture content of the inorganic particulate material is 20% or more and 28% or less. The shield machine according to claim 1.

3. The inorganic particulate material comprises kaolin; The shield machine according to claim 1 or 2.

4. A lubricant supply unit is further provided which supplies a lubricant to the overcut portion through a hole formed in the assembled segments. The shield machine according to claim 1 or 2.

5. A method for excavating underground ground using a shield machine, comprising: A step of rotating a cutter of the shield machine about an axis extending in an excavation direction, which is a direction in which the shield machine excavates; supplying an inorganic particulate material containing stone powder and water to an overcut portion formed on an outer periphery of the cutter; Equipped with Excavation method.

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