Tunnel boring machine

Abstract

To provide a tunnel boring machine that allows for safe and easy bit replacement, and in which the replacement bit body can be installed adjacent to the rotating head in the radial direction. [Solution] The system is provided on the rotating head of a tunnel boring machine and is rotatable around a rotation axis 62 that is tangential to the rotating head. It comprises a plurality of adjacent interchangeable bit bodies 6 arranged along the radial direction of the rotating head, and an interchangeable bit group 610 consisting of a plurality of interchangeable bits 61 provided in the circumferential direction of the rotation axis 62, which can simultaneously excavate the tunnel face. The first interchangeable bit group 610a and the second interchangeable bit group 610b, which are adjacent to each other, are arranged such that a first arrangement line 611a, which is a straight line passing through the tip of the first interchangeable bit group 610a, and a second arrangement line 611b, which is a straight line passing through the tip of the second interchangeable bit group 610b, intersect at an acute angle.

Description

Technical Field

[0001] The present invention relates to a tunnel boring machine having a rotating head.

Background Art

[0002] In recent years, tunnel construction using tunnel boring machines such as shield tunneling machines has been characterized by longer distances and greater depths. In long-distance tunnel boring, there is concern that the bits provided on the rotating head may wear during the excavation.

[0003] Especially when excavating through sand layers or gravel layers over a long distance, the cemented carbide tips at the bit tips are worn or chipped, so it is necessary to replace the bits.

[0004] To replace the bits, the face was improved, and workers entered the chamber between the cutter and the partition to manually replace the bits. However, not only does it require high costs and time for ground improvement, but it is also dangerous and labor-intensive to carry and fix heavy bits in a narrow space.

[0005] Also, in a slurry shield tunneling machine under a river bottom or a seabed, divers would dive into the chamber and replace the bits by high-pressure work. However, the work under high pressure has time limitations and a high risk of decompression sickness, so the bit replacement work has caused cost increases and project delays.

[0006] Patent Document 1 discloses a bit switching device including a cutter head having a head member (cutter spoke) that rotates with respect to the face and is arranged to extend in the radial direction, a rotating shaft that is rotatable about an axis extending along the rotation direction of the head member and at least one end of which protrudes from the side portion of the head member to the outside of the head member, a plurality of bits provided at a predetermined interval in the rotation direction at the end portion of the rotating shaft protruding to the outside of the head member, a rotation restraining means for restraining the rotation of the rotating shaft, and a rotation means for rotating the rotating shaft in a state where the rotation restraint of the rotating shaft by the rotation restraining means is released. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 4891661 [Overview of the initiative] [Problems that the invention aims to solve]

[0008] In a device having multiple rotatable bits, as described in Patent Document 1 above, worn bits can be easily replaced with new ones without requiring dangerous and costly replacement work. When changing bits, the tunneling machine is stopped, and the rotating shaft, which is equipped with multiple bits, is rotated to position the new, unworn bit on the excavation surface.

[0009] To rotate multiple bit switching devices installed on a radially extending head member, it is necessary to prevent adjacent bit switching devices from interfering with each other. Patent Document 1 addresses this by providing separate rotation drive mechanisms on one and the other of adjacent rotating shafts to prevent them from rotating simultaneously. However, a configuration like that in Patent Document 1 requires separate rotation drive mechanisms on adjacent rotating shafts, which increases installation space and makes the structure more complex.

[0010] Furthermore, when multiple rotation axes of bit switching devices installed on radially extending head members are rotated simultaneously by a single rotary drive mechanism, it is necessary to space the bit switching devices at a certain distance apart to prevent interference between adjacent bit switching devices. However, the radial length of the head member is constrained by the diameter of the tunnel being excavated, and if the radial length of the head member cannot be secured to accommodate the required number of bit switching devices, the number of head members must be increased, which complicates the structure of the tunnel boring machine and increases costs.

[0011] The problem that this invention aims to solve is to provide a tunnel boring machine that allows for safe and easy replacement of bits and enables the replacement bit bodies to be installed adjacent to the rotating head in the radial direction. [Means for solving the problem]

[0012] The invention according to claim 1 is a tunnel boring machine having a rotating head, comprising: a plurality of interchangeable bit bodies provided on the rotating head and rotatable about a rotation axis provided along the tangential direction of the rotation circle of the rotating head, and arranged adjacent to each other along the radial direction of the rotation circle of the rotating head; and a plurality of interchangeable bit groups provided in the circumferential direction of the rotation axis of the interchangeable bit bodies and composed of interchangeable bits capable of simultaneously excavating a tunnel face, wherein the interchangeable bit group comprises a first interchangeable bit group and a second interchangeable bit group provided adjacent to the first interchangeable bit group, and in a side view, the first interchangeable bit group and the second interchangeable bit group are arranged such that a first arrangement line, which is a straight line passing through the tip of the first interchangeable bit group, and a second arrangement line, which passes through the tip of the second interchangeable bit group, intersect at an acute angle.

[0013] The invention according to claim 2 is a tunnel boring machine according to claim 1, characterized in that the angle at which the first alignment line and the second alignment line intersect is 60 degrees.

[0014] The invention according to claim 3 further comprises a third exchange bit group adjacent to the first exchange bit group and the second exchange bit group, The tunnel boring machine according to claim 1, characterized in that, in a side view, the third exchange bit group is arranged such that a third arrangement line, which is a straight line passing through the tip of the third exchange bit group, intersects the first arrangement line and the second arrangement line at an acute angle.

[0015] The invention according to claim 4 is a tunnel boring machine according to claim 3, characterized in that the angle at which the third arrangement line intersects the first arrangement line and the second arrangement line is 60 degrees.

Advantages of the Invention

[0016] According to the present invention, by simply rotating the replaceable bit body, the worn replaceable bit can be easily and safely replaced with a new replaceable bit, and efficient excavation can be carried out. Since the first arrangement line and the second arrangement line intersect at an acute angle, replaceable bits of the same dimensions as those of the present invention are arranged at the same intervals. However, compared with the case where the first arrangement line and the second arrangement line intersect at a right angle or an obtuse angle, the maximum diameter of the rotation orbit of the replaceable bit can be made smaller. Therefore, the replaceable bit body can be arranged adjacent to the rotation head in the radial direction thereof.

[0017] In addition, by arranging the third replaceable bit group adjacent to the first replaceable bit group and the second replaceable bit group such that the third arrangement line, which is a straight line passing through the tip of the third replaceable bit group, intersects the first arrangement line and the second arrangement line at an acute angle, the worn replaceable bit group can be replaced twice.

Brief Description of the Drawings

[0018] [Figure 1] It is a front view of a tunnel boring machine showing a first embodiment of the present invention. [Figure 2] It is a cross-sectional view of a main part of a tunnel boring machine showing a first embodiment of the present invention. [Figure 3] It is a side view of a replaceable bit body according to a first embodiment of the present invention. [Figure 4] It is a diagram for explaining the relative relationship during rotation of a plurality of replaceable bits according to a first embodiment of the present invention. [Figure 5] It is a diagram for explaining the positional relationship due to the pedestal shape of a replaceable bit body according to a first embodiment of the present invention. [Figure 6] It is a side view of a replaceable bit according to a second embodiment of the present invention.

Best Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the embodiments.

[0020] [First Embodiment] The first embodiment of the present invention will be described based on FIGS. 1 to 5.

[0021] FIG. 1 is a front view of a tunnel boring machine, FIG. 2 is a sectional view of a main part of the tunnel boring machine, FIG. 3 is a side view of a replaceable bit body, FIG. 4 is a diagram for explaining the relative relationship during rotation of a plurality of replaceable bits, and FIG. 5 is a diagram for explaining the positional relationship based on the pedestal shape of the replaceable bit body.

[0022] As shown in FIGS. 1 and 2, the tunnel boring machine of this embodiment is a shield tunneling machine 1, and has a circular rotating head 2 that rotates facing the face and a chamber 3 formed on the back side of the rotating head 2, and advances while excavating the ground by rotating the rotating head 2.

[0023] The rotating direction of the rotating head 2 can rotate in both clockwise and counterclockwise directions.

[0024] The excavated soil and sand are taken into the chamber 3 and discharged rearward through the soil discharging device 4. The rotating head 2 is provided on the front end face of the shield tunneling machine 1, and rotates around the central axis of the shield tunneling machine 1 by driving a rotating head drive unit 5 connected to the rotating head 2.

[0025] The rotating head 2 includes six cutter spokes 20 arranged radially at equal intervals from the rotation center, and a cutter ring 21 that connects the tips of the cutter spokes 20 to form the outer peripheral edge of the rotating head 2.

[0026] A leading bit 22 is arranged on the front surface 20a of the cutter spoke 20. A ring bit 23 is installed on the front of the cutter ring 21.

[0027] The cutter spokes 20 consist of the first cutter spoke 201, located directly above in Figure 1, and in a clockwise direction, the second cutter spoke 202, third cutter spoke 203, fourth cutter spoke 204, fifth cutter spoke 205, and sixth cutter spoke 206.

[0028] On each of the six cutter spokes 20 that extend radially along the rotational direction of the rotating circle of the rotating head 2, three interchangeable bit bodies 6 are arranged adjacent to each other in pairs on both sides 20b.

[0029] As shown in Figure 3, the interchangeable bit body 6 comprises an equilateral triangular base 60 and a plurality of (six in this embodiment) rectangular interchangeable bits 61 provided around the outer circumference of the base 60. The tip of each interchangeable bit 61 is provided with a hard bit tip 63. In Figure 3, the upward direction in the drawing is the face direction, and the front surface 20a of the cutter spoke 20 is shown facing upward.

[0030] The bit tips 63 are provided at the tip of each interchangeable bit 61, on both sides in the direction of rotation of the rotary head 2. Therefore, drilling can be performed with a single interchangeable bit 61 whether the rotary head 2 is rotated clockwise or counterclockwise.

[0031] The interchangeable bit bodies 6 provided on the first cutter spoke 201 and the fourth cutter spoke 204, the interchangeable bit bodies 6 provided on the second cutter spoke 202 and the fifth cutter spoke 205, and the interchangeable bit bodies 6 provided on the third cutter spoke 203 and the sixth cutter spoke 206 are arranged at different distances from the center of the rotating head 2 (Figure 1). As the rotating head 2 rotates, the interchangeable bit bodies 6 rotate in the circumferential direction, allowing the interchangeable bits 61 to excavate over the entire front surface of the rotating head 2.

[0032] Each of the interchangeable bits 61 of the interchangeable bit body 6 provided on the first cutter spoke 201 and the fourth cutter spoke 204 is at the same distance from the center of the rotating head 2, and they drill at the same location, thus forming a so-called two-pass arrangement. Similarly, each of the interchangeable bits 61 of the interchangeable bit body 6 provided on the second cutter spoke 202 and the fifth cutter spoke 205, and each of the interchangeable bits 61 of the interchangeable bit body 6 provided on the third cutter spoke 203 and the sixth cutter spoke 206, are also arranged to form two passes.

[0033] The base 60 of the interchangeable bit body 6 is a plate shaped like an equilateral triangle in side view, and is rotatably mounted on the cutter spoke 20 around a rotation axis 62 that passes through its center and is provided along the tangential direction of the rotation circle of the rotating head 2. The rotation axis 62 is provided so as to penetrate the cutter spoke 20 in the tangential direction of the rotation circle of the rotating head 2.

[0034] A pair of interchangeable bit bodies 6, provided on both sides of the cutter spoke 20, share a rotating shaft 62. The interchangeable bits 61 provided on the pair of interchangeable bit bodies 6 that share the rotating shaft 62 are each at the same distance from the center of the rotating head 2 in the direction of rotation of the rotating head 2, and thus they drill at the same position, forming a so-called two-pass arrangement. Therefore, together with the interchangeable bits 61 positioned at the same distance from the center of the rotating head 2 on the other cutter spoke 20, a four-pass arrangement is formed.

[0035] The interchangeable bit body 6 is connected to an interchangeable bit body rotation mechanism (not shown) that simultaneously rotates three interchangeable bit bodies 6 arranged along the radial direction of the cutter spoke 20, and an interchangeable bit body stopping mechanism (not shown) that stops the interchangeable bit body 6 from rotating during excavation. The interchangeable bit rotation mechanism and the interchangeable bit stopping mechanism are housed within the cutter spoke 20 and are based on known technology, so a detailed explanation of their configuration will be omitted.

[0036] Each side of the equilateral triangle of the base 60 of the interchangeable bit body 6 is provided with multiple (two in this embodiment) interchangeable bits 61. These interchangeable bits 61 provided on the same side are capable of excavating the tunnel face simultaneously and constitute an interchangeable bit group 610.

[0037] Two exchange bits 61a and 61b provided on the first side 600 of the base 60 constitute a first exchange bit group 610a, two exchange bits 61c and 61d provided on the second side 601 constitute a second exchange bit group 610b adjacent to the first exchange bit group 610a, and two exchange bits 61e and 61f provided at both ends of the third side 602 constitute a third exchange bit group 610c adjacent to the first exchange bit group 610a and the second exchange bit group 610b.

[0038] The alignment line 611, which is a straight line passing through the tip of the exchange bit group 610, is parallel to the side of the base 60 on which the exchange bit group 610 is provided, and intersects with each other at an acute angle.

[0039] Specifically, the first arrangement line 611a, which is a straight line passing through the tip of the first exchange bit group 610a, and the second arrangement line 611b, which is a straight line passing through the tip of the second exchange bit group 610b, intersect at a 60-degree angle, and the third arrangement line 611c, which is a straight line passing through the tip of the third exchange bit group 610c, intersects the first arrangement line 611a and the second arrangement line 611b at a 60-degree angle.

[0040] The base 60 is formed in the shape of an equilateral triangle so that when the exchange bit body 6 is rotated, it is positioned inside the maximum diameter of the rotational trajectory of the exchange bit 61. The equilateral triangle shape of the base 60 does not need to have sharp corners at its vertices, as these corners may be chamfered.

[0041] When rotation is restricted, the interchangeable bit body 6 is positioned on the cutter spoke 20 such that one of the first side 600 (or first alignment line 611a), second side 601 (or second alignment line 611b), or third side 602 (or third alignment line 611c) of the base 60 is parallel to the front surface 20a of the cutter spoke 20 of the rotating head 2, and one of the first interchangeable bit group 610a, second interchangeable bit group 610b, or third interchangeable bit group 610c protrudes forward from the rotating head 2. Figure 3 shows the state in which the first interchangeable bit group 610a protrudes forward from the front surface 20a of the cutter spoke 20.

[0042] All exchange bits 61 are identical rectangles and are positioned at the same location on each side of the base 60. Specifically, when the first exchange bit group 610a faces the working face, the exchange bit 61c is positioned at the same location where the exchange bit 61a is positioned, rotated to face the working face, and when the third exchange bit group 610c faces the working face, the exchange bit 61e is positioned at the same location where the exchange bit 61a is positioned, rotated to face the working face, and when the second exchange bit group 610b faces the working face, the exchange bit 61d is positioned at the same location where the first exchange bit group 610a faces the working face, rotated to face the working face, and when the third exchange bit group 610c faces the working face, the exchange bit 61f is positioned at the same location where the exchange bit 61b is positioned, rotated to face the working face.

[0043] In other words, the exchange bit 61a of the first exchange bit group 610a, the exchange bit 61c of the second exchange bit group 610b, and the exchange bit 61e of the third exchange bit group 610c are arranged to excavate the face in the same path. Also, the exchange bit 61b of the first exchange bit group 610a, the exchange bit 61d of the second exchange bit group 610b, and the exchange bit 61f of the third exchange bit group 610c are arranged to excavate the face in the same path.

[0044] During excavation by the shield tunneling machine 1, a replacement bit body stopping mechanism (not shown) is activated to restrict the rotation of the replacement bit body 6. As the rotating head 2 rotates, the replacement bit group 610, which protrudes forward from the cutter spoke 20, excavates the front surface of the tunnel face.

[0045] When the shield tunneling machine 1 performs long-distance excavation, for example, the replacement bit group 610 that excavates the ground wears down and becomes shorter. Therefore, the worn replacement bit group 610 is moved away from the position facing the tunnel face, and a new, unworn replacement bit group 610 is made to protrude forward of the cutter spoke 20.

[0046] To replace the replacement bit group 610, the shield tunneling machine 1 is stopped, then the shield tunneling machine 1 is moved back slightly to separate the replacement bit body 6 from the tunnel face.

[0047] Next, the replacement bit rotation mechanism is activated to rotate the replacement bit body 6, retracting the worn replacement bit group 610 from its position facing the cutting face, and simultaneously extending a new replacement bit group 610 to the position where the retracted replacement bit group 610 was located, that is, forward of the rotating head 2.

[0048] For example, as shown in Figure 4, three sets of interchangeable bit bodies 6 are installed on the side surface 20b of the cutter spoke 20, along the radial direction of the cutter spoke 20, so as to be rotatable at the same time. The adjacent exchange bit bodies 6 are positioned such that when the three exchange bit bodies 6 are rotated simultaneously, the rotational paths of the exchange bits 61 do not overlap.

[0049] In Figure 4, the upward direction in the drawing is the face direction, and the front surface 20a of the cutter spoke 20 is shown facing upward.

[0050] Initially, as shown in Figure 4(a), the interchangeable bit body 6 is configured such that the first interchangeable bit group 610a faces the cutting face and protrudes forward from the front surface 20a of the cutter spoke 20, while the second interchangeable bit group 610b and the third interchangeable bit group 610c are located behind the front surface of the cutter spoke 20.

[0051] Figure 4(b) shows the replacement bit body 6 rotated 30 degrees clockwise, Figure 4(c) shows the replacement bit body 6 rotated 60 degrees clockwise, and Figure 4(d) shows the replacement bit body 6 rotated 90 degrees clockwise. When the replacement bit body 6 is rotated 120 degrees, a new second replacement bit group 610b protrudes forward of the cutter spoke 20.

[0052] As shown in Figure 4, if the adjacent exchange bit bodies 6 are arranged so that the distance between their centers is greater than twice the maximum radius of the rotational trajectory of the exchange bit 61, the adjacent exchange bit bodies 6 can be rotated without interfering with each other.

[0053] In this embodiment, the exchange bit body 6 has three sets of exchange bit groups 610, allowing for two exchanges from the start.

[0054] Next, the effect of the acute intersection of the first placement line 611a passing through the tip of the first exchange bit group 610a, the second placement line 611b passing through the tip of the second exchange bit group 610b, and the third placement line 611c passing through the tip of the third exchange bit group 610c in the exchange bit body 6 will be explained with reference to Figure 5.

[0055] In Figure 5, the upward direction in the drawing is the face direction, and the front surface 20a of the cutter spoke 20 is shown facing upward.

[0056] Figure 5 shows a comparison of three exchange bit bodies with the same dimensions: one with a base 60 that is an equilateral triangle and whose arrangement line 611, which is a straight line passing through the tips of two adjacent exchange bit groups 610, intersects at an acute angle (Figure 5(a)); one with a base 60' that is a square and whose arrangement line 611', which is a straight line passing through the tips of two adjacent exchange bit groups 610', intersects at a 90-degree angle (Figure 5(b)); and one with a base 60'' that is a regular pentagon and whose arrangement line 611'', which is a straight line passing through the tips of two adjacent exchange bit groups 610'', intersects at an obtuse angle (Figure 5(c)).

[0057] In Figure 5, each of the interchangeable bits 61, 61', and 61” are of the same dimensions, and the two interchangeable bits 61, 61', and 61” in each group are positioned at the same interval. Each of the interchangeable bits 61, 61', and 61” of the interchangeable bit bodies 6, 6', and 6” located on the left side of the figure is positioned to drill the same path.

[0058] As is clear from Figure 5, even if interchangeable bits of the same dimensions and number are arranged at the same intervals, the radius of rotation increases in the order of interchangeable bit body 6, interchangeable bit body 6', and interchangeable bit body 6'', and it can be seen that the radial spacing of interchangeable bit bodies 6, 6', and 6'' located on the right side in the figure must be increased.

[0059] Therefore, a replacement bit body 6 whose alignment line 611 passing through the tip of an adjacent replacement bit group 610 intersects at an acute angle can be installed closer to the rotating head in the radial direction than replacement bit bodies 6' and 6'', allowing for a greater number of replacement bit bodies that can be installed on cutter spokes 20 of the same length, thereby suppressing an increase in the number of cutter spokes 20. This is particularly effective when multiple interchangeable bit bodies 6, arranged along the radial direction of the cutter spoke 20, are to be rotated simultaneously.

[0060] [Second Embodiment] A second embodiment of the present invention will be described with reference to Figure 6. Note that parts similar to those in the first embodiment are denoted by the same reference numerals and detailed descriptions are omitted; the following will mainly describe the parts that differ.

[0061] The second embodiment differs from the first embodiment in that the first side 600 and the second side 601 of the base 60 are provided with a first exchange bit group 610a and a second exchange bit group 610b, respectively, while the third side 602 is not provided with a third exchange bit group 610c.

[0062] In this embodiment, since the replacement bit body 6 is equipped with only two sets of replacement bit groups 610, a worn replacement bit group 610 can only be replaced once, making it suitable for situations where the number of replacements is expected to be infrequent, such as during drilling at relatively short distances.

[0063] In this embodiment, the number of times the replacement bits need to be changed is reduced compared to the first embodiment, and costs can be reduced because replacement bits are not provided.

[0064] [Other variations] The present invention is not limited to the embodiments described above. For example, the following are also included.

[0065] In this embodiment, the tunnel boring machine is a shield tunneling machine, but it is not limited to this and is not particularly limited as long as it has a rotating head. For example, it may be a tunnel boring machine such as an excavator used in the tunnel jacking method or a TBM (tunnel boring machine).

[0066] In this embodiment, six cutter spokes are provided, but the number can be increased or decreased depending on the dimensions of the rotating head, etc.

[0067] In this embodiment, three interchangeable bits are arranged on each side of the cutter spoke, but it is also possible to increase the number of interchangeable bits depending on the radius of the rotating head (length of the cutter spoke).

[0068] In this embodiment, the base is an equilateral triangle, but it is not limited to an equilateral triangle as long as the arrangement lines passing through the tips of adjacent exchange bit groups intersect at an acute angle and the shape does not protrude beyond the maximum diameter of the rotational trajectory of the exchange bit group. For example, it may be a shape in which the corners of an equilateral triangle are curved.

[0069] Furthermore, at least one of the interchangeable bit bodies, which are aligned at the same circumferential distance from the center of the rotating head (forming the same path), is made movable toward the face front. The interchangeable bit body is moved forward until the tip of the worn interchangeable bit is in the same position as the tip of the interchangeable bit before wear, excavating the face front, and then retracted to its original position. When the interchangeable bit body is rotated in this state, the interchangeable bit rotates smoothly without getting stuck in the face, even without retracting the rotating head significantly.

[0070] In this embodiment, the replacement bit in the replacement bit body was a bit used in a normal shield tunneling machine to excavate the ground, a so-called main bit (tooth bit), but it is not limited to this. For example, it may be a lead bit or a roller bit. In this case, the lead bit or roller bit can be configured to be mounted on a base.

[0071] Each technical matter in any embodiment, including variations, may be applied to other embodiments to form examples. [Explanation of Symbols]

[0072] 1. Shield tunneling machine 2 Rotating Heads 20 Cutter Spokes 21 Cutter Rings 22 Leading bits 23 Ring Bits 3 chambers 4 Earth removal equipment 5. Rotating head drive unit 6-bit exchange 60 base 600 First side 601 Second side 602 Third side 61 Replacement Bits 610 Exchange Bit Groups 610a First exchange bit group 610b Second Exchange Bit Group 610c Third Exchange Bit Group 611 Placement line 611a 1st placement line 611b 2nd placement line 611c 3rd placement line 62 Rotation axis 63-bit chip

Claims

1. A tunnel boring machine having a rotating head, The rotating head is provided with a rotation axis that is rotatable about a rotation axis provided along the tangential direction of the rotation circle of the rotating head, and a plurality of interchangeable bit bodies are arranged adjacent to each other along the radial direction of the rotation circle of the rotating head, The system comprises a group of interchangeable bits provided in the circumferential direction of the rotation axis of the interchangeable bit body, and the group of interchangeable bits being capable of simultaneously excavating the tunnel face, The aforementioned exchange bit group comprises a first exchange bit group and a second exchange bit group adjacent to the first exchange bit group. In a side view, the first exchange bit group and the second exchange bit group are arranged such that a first arrangement line, which is a straight line passing through the tip of the first exchange bit group, and a second arrangement line, which passes through the tip of the second exchange bit group, intersect at an acute angle. A tunnel boring machine characterized by the following features.

2. The angle at which the first alignment line and the second alignment line intersect is 60 degrees. The tunnel boring machine according to feature 1.

3. The exchange bit group further includes a third exchange bit group adjacent to the first exchange bit group and the second exchange bit group. In a side view, the third exchange bit group is arranged such that a third arrangement line, which is a straight line passing through the tip of the third exchange bit group, intersects the first arrangement line and the second arrangement line at an acute angle. A tunnel boring machine according to claim 1 or 2.

4. The angle at which the third arrangement line intersects the first arrangement line and the second arrangement line is 60 degrees. The tunnel boring machine according to claim 3.

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