Distance detection device and distance detection method

Abstract

To provide a distance detection device and a distance detection method capable of highly accurately detecting a distance to an excavator with a simple configuration.SOLUTION: The depth detection device includes a rod-shaped member provided to protrude from a partition wall installed on an arrival side of the excavator, a conductive material provided in the rod-shaped member or to protrude from one end of the rod-shaped member, and notification means connected to the conductive material and notifying that a conductive state is switched to a non-conductive state or the non-conductive state is switched to the conductive state due to contact of the excavator with the conductive material.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for detecting distance to an excavator. [Background technology]

[0002] When constructing a sewer tunnel or a trailing tunnel by using a shield machine or other excavator to excavate a shaft or a leading tunnel, it is necessary to check whether the excavator has reached the intended position.

[0003] One known method for confirming whether the intended position has been reached is to measure the position of the tip of a drilling pipe that has penetrated the wall of the shaft using a borehole position measuring device, and then use a sensor at the tip of the drilling pipe to detect the positions of multiple transmitting coils attached to the cutter disk of the shield machine, thereby measuring the relative position of the shaft and the shield machine (see, for example, Patent Document 1).

[0004] Another known method is to attach a detection sheet to the retaining wall of a shaft or the outer surface of a segment of a preceding tunnel, and confirm that the excavator has reached the shaft or preceding tunnel by having a detection rod attached to the excavator or the tip of the excavator come into contact with the detection sheet (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-246483 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-118124 Summary of the Invention [Problem to be solved by the invention]

[0006] When the excavator reached the target, it had to be placed inside the bulkhead installed in the arrival shaft (arrival shaft), but if it pressed the bulkhead and the back anchor supporting it at the same time, the bulkhead could be deformed or damaged, which could lead to water and soil flowing into the arrival shaft. For this reason, it was important to stop the excavator at a predetermined position before pushing the bulkhead, and it was also necessary to check from the arrival shaft that the excavator was in the predetermined position.

[0007] The method described in Patent Document 1 above requires installing a sensor at the tip of the boring pipe and attaching multiple transmitting coils to the cutter disc, and since the measurement is performed without contact, it is not possible to detect the distance to the drilling machine with high accuracy using a simple configuration.

[0008] Furthermore, the method described in Patent Document 2 above also requires attaching a detection sheet to the outer side of the retaining wall of the arrival shaft, extending a detection rod from the shield machine, and measuring the distance to the shield machine until it reaches the destination, and this simple configuration does not allow for highly accurate detection of the distance to the excavator. [Means for solving the problem]

[0009] The present invention has been made in consideration of the above-mentioned problems, and is a device for detecting a distance to an excavator, a rod-shaped member provided so as to protrude from a partition wall installed on the reach side of the excavator; a conductive material provided within the rod-shaped member or protruding from one end of the rod-shaped member; a notification means connected to the conductive material and notifying that the conductive material has been switched from a conducting state to a non-conducting state or from a non-conducting state to a conducting state due to contact of the excavator with the conductive material; A distance sensing device is provided, comprising: [Effects of the Invention]

[0010] According to the present invention, the distance to the excavator can be detected with high accuracy using a simple configuration. [Brief explanation of the drawings]

[0011] [Figure 1] A diagram showing the tunnel being constructed by a boring machine digging from the departure shaft to the arrival shaft. [Figure 2] A diagram showing an example of the configuration of a shield machine as an excavator. [Figure 3] A diagram showing the excavator reaching the arrival shaft. [Figure 4] FIG. 1 is a diagram showing a first example of the configuration of a device for detecting the distance from the arrival side to an excavator. [Figure 5] FIG. 5 is a diagram showing a detailed configuration of the device shown in FIG. 4. [Figure 6] A diagram showing the appearance of the device shown in Figure 4 and how it is attached to a bulkhead. [Figure 7] FIG. 10 is a diagram showing a second example of the configuration of a device for detecting the distance from the reach side to the excavator. [Figure 8] A diagram showing the appearance of the device shown in Figure 7 and how it is attached to a bulkhead. [Figure 9] FIG. 10 is a diagram showing the installation status of notification means. [Figure 10] FIG. 10 is a diagram showing an example of a position where a distance detection device is attached to a bulkhead. [Figure 11] 10 is a flowchart showing an example of an operation for detecting the distance to the shield machine using a distance detection device. [Figure 12] 10 is a flowchart showing another example of the operation of detecting the distance to the shield machine using a distance detection device. [Figure 13] FIG. 10 is a diagram showing a third example configuration of a device for detecting the distance from the reach side to the excavator. [Figure 14] FIG. 10 is a diagram illustrating a method for installing an arrival detection sensor. [Figure 15] 10A and 10B are diagrams illustrating a method for detecting the arrival position of an excavator using an arrival detection sensor. [Figure 16] FIG. 10 is a diagram illustrating a display panel as a notification means. DETAILED DESCRIPTION OF THE INVENTION

[0012] Underground, there are buried objects such as water pipes, sewer pipes, gas pipes, and communication cables, as well as road tunnels and subway tunnels. When installing new underground objects, the ground can be opened and the object can be buried in the cut-out. When building new underground road tunnels, the tunnel can be constructed by digging into the ground with an excavator.

[0013] However, in urban areas where many buried objects have already been laid, road tunnels have been built, and many buildings have been constructed above ground, there is no space to cut open the ground or dig down into it.

[0014] Therefore, a vertical hole called a shaft is formed, a boring machine is installed inside the shaft to excavate a horizontal hole, and the horizontal hole is excavated using the boring machine, thereby allowing the construction of a sewer tunnel, subway tunnel, etc.

[0015] Figure 1 shows how a tunnel is constructed by having an excavator excavate from a starting shaft to a destination shaft. Two shafts are formed in the ground, and an excavator is installed in one of the shafts, which then creates a lateral tunnel toward the other shaft, constructing the desired tunnel. The shaft where the excavator is installed is the starting shaft 10, and the other shaft that the excavator excavates and reaches is the destination shaft 11.

[0016] Shafts can be constructed using a vibrating hammer, which reduces the frictional resistance of the ground by vibrating an exciter and drives the sheet piles into the ground, a hydraulic pressing and pulling machine, which uses a hydraulic jack to push the steel sheet piles into the ground and then pulls them out, and a shaft drill, which erects steel casings.

[0017] The shaft can be protected from the collapse of the surrounding ground by a retaining wall. The retaining wall can be made of steel sheet piles, but is not limited to this. It can also be a continuous underground wall constructed around the entire shaft by continuously pouring soil and cement slurry while mixing it in situ using the SMW (Soil Mixing Wall) method. The material used to construct the continuous underground wall is not limited to soil and cement slurry, but can also be concrete, a stabilizing liquid containing bentonite, etc.

[0018] The excavator penetrates the retaining wall to form a horizontal hole. To prevent the ground from collapsing while the excavator is excavating, a predetermined area of ​​the ground outside the retaining wall can be improved using chemicals, cement, freezing agents, etc. The area to be improved can be determined based on the strength of the ground, etc.

[0019] The excavator may be, but is not limited to, a shield machine 12. In the following description, the excavator will be described as a shield machine 12.

[0020] After constructing the departure shaft 10, the entrance (entrance) 13 of the horizontal tunnel is formed using steel material, rubber gasket, etc., and a reaction force receiver 14 is installed on the side of the departure shaft 10 facing the entrance 13 to allow the shield machine 12 to move forward. A support 15 to support the shield machine 12 is installed between the entrance 13 and the reaction force receiver 14 at the bottom of the departure shaft 10. The shield machine 12 is then disassembled and transported into the departure shaft 10 by a crane, etc., assembled at the bottom of the departure shaft 10, and installed on the support 15. Once assembly of the shield machine 12 is complete, it departs toward the arrival shaft 11. The shield machine 12 reaches the arrival shaft 11 via the route shown by the dashed line.

[0021] FIG. 2 is a diagram showing an example of the configuration of a shield machine 12. The shield machine 12 includes a hollow cylindrical skin plate 20 that resists soil and water pressure, and a rotatable cutting part for cutting the ground at one end of the skin plate 20, which is the leading edge in the excavation direction. The cutting part is, for example, a cutter head 21. The cutter head 21 may be structured in either a spoke type or a face plate type. A spoke type has a structure in which an axle and a ring are connected radially by rod-shaped members, while a face plate type has a structure in which one side is a circular plate with holes in various places. The cutter head 21 comes into contact with the ground to cut it, and is equipped with a bit as a cutting member that stirs and fluidizes the cut soil as it rotates.

[0022] The shield machine 12 is provided with a partition wall 22 that separates the tunnel face side, which is the excavation direction when excavating a tunnel, from the tunnel mouth side, which is the opposite direction. In the example shown in FIG. 1, the tunnel mouth is the entrance 13 in the departure shaft 10. The partition wall 22 is installed closer to the tunnel mouth than the cutter head 21 and spaced apart from the cutter head 21. The space between the cutter head 21 and the partition wall 22 is called a chamber 23.

[0023] A drive unit 24 for rotating the cutter head 21 is provided in the partition 22, and a discharge device for discharging the cut earth is connected to it. The drive unit 24 is a drive motor that rotates a rotary shaft connected to the center of the cutter head 21. The discharge device is a screw conveyor 25 equipped with a screw having a shaft within a pipe and spiral blades arranged spirally around the shaft. The cutter head 21 takes in the cut earth into the chamber 23 through gaps between radial rod-shaped members in the case of a spoke type, or through holes in a circular plate in the case of a face plate type.

[0024] The screw conveyor 25 transports the cuttings in the chamber 23 to the mine mouth by rotating the internal screw. The cuttings transported by the screw conveyor 25 are sent to the departure shaft 10 by a belt conveyor or the like, and then carried out to the outside of the mine.

[0025] The shield machine 12 is equipped with jacks 26 for moving the cutter head 21 forward while rotating it. The shield machine 12 also has an assembly device (erector) 28 that assembles lining materials (segments) 27 that cover the inner wall surface of the tunnel into a ring shape to prevent the excavated tunnel from collapsing. The jacks 26 are placed between the ring-shaped assembled segments 27 and the partition wall sections 22, and move the cutter head 21 forward by moving the partition wall sections 22 based on the fixed segments 27. The shield machine 12 is equipped with a backfill injection device 29 that injects mortar or the like into the backs of the segments 27 to prevent the surrounding ground from loosening.

[0026] The shield machine 12 is equipped with a total station as a surveying device, which calculates the coordinates of the total station from known point coordinates. Based on the calculated coordinates, the position of the tip of the bit of the shield machine 12, etc., can be calculated as the position of the shield machine 12 (underground surveying). The total station is a device that simultaneously measures angle and distance. It irradiates a target with known point coordinates with a laser beam, measures the distance using the reflected light, and measures the horizontal and vertical angles at which the laser beam is irradiated. The total station calculates the position coordinates of the total station from the measured angle and distance. The total station then irradiates a predetermined position on the shield machine 12 with a laser beam, measures the distance using the reflected light, and measures the horizontal and vertical angles at which the laser beam is irradiated. This calculates the coordinates of the predetermined position of the shield machine 12. Furthermore, since the positions from the predetermined position to the tip of the bit of the cutter head 21, etc., are predetermined, the coordinates of each position, such as the tip of the bit, can be calculated from the calculated coordinates of the predetermined position. In this way, excavation can be carried out while surveying the shield machine 12 and detecting the current position of the shield machine 12. Note that the surveying device is not limited to a total station, as long as it is capable of surveying the position of the shield machine 12.

[0027] The shield machine 12 is provided with a partition section 22 behind the face, which is the excavation surface, and separates it from the inside of the tunnel. Excavation can be carried out using any of the following construction methods: a mud shield in which mud is supplied into a chamber 23 separated by the partition section 22 and the chamber 23 is pressurized with the mud to perform excavation; a mud shield in which mud is supplied into the chamber 23 and the chamber 23 is pressurized with the mud to perform excavation; or an air bubble shield in which excavation is carried out while injecting air bubbles made from a special foaming material into the face or chamber 23.

[0028] Figure 3 shows the state when the excavator has reached the arrival shaft 11. A bulkhead 31 is installed adjacent to the retaining wall 30 of the arrival shaft 11. As with the departure shaft 10, the arrival shaft 11 may also have an entrance installed using steel material and rubber packing.

[0029] The bulkhead 31 is composed of a cylindrical body 32 into which the shield machine 12 can be inserted, and a lid 33 that closes the opening of the cylindrical body 32 on the arrival shaft 11 side. The cylindrical body 32 and lid 33 are made of steel, and a filling material is filled into the cylindrical body 32 using a filling device. The filling material is liquefied treated soil or the like made by mixing construction waste soil or the like with water and cement. A gasket or water-expanding rubber or the like is provided between the cylindrical body 32 and the lid 33 as a sealing material to maintain airtightness and liquid tightness, and the cylindrical body 32 and the lid 33 are connected using bolts and nuts. A back anchor 34 is attached to the lid 33 of the bulkhead 31 as a support member that supports the lid 33 against the pressure of the filling material.

[0030] The shield machine 12 penetrates the retaining wall 30, enters the cylindrical body 32 of the bulkhead 31, and advances within the cylindrical body 32. A gasket 35 is provided inside the cylindrical body 32 as a ring-shaped closing member, and the gasket 35 prevents water and earth and sand from entering the arrival shaft 11 from outside. At this stage, the shield tunnel constructed by assembling the segments 27 into a ring has not yet reached the arrival shaft 11. Therefore, an additional cylindrical body can be connected to extend the cylindrical body, extending the shield tunnel all the way into the arrival shaft 11 and constructing a tunnel connecting the departure shaft 10 and the arrival shaft 11. To connect the additional cylindrical body, the cover 33 must be removed, but the gasket 35 must remain in place to prevent water and earth and sand from entering when the cover 33 is removed.

[0031] On the other hand, it is desirable that the amount of filler that flows into the arrival shaft 11 when the lid 33 is removed be small, and to achieve this, it is desirable that the cutter head 21 of the shield machine 12 be as close to the lid 33 as possible.

[0032] If the cutter head 21 is brought close to the lid 33, it will push against the lid 33, causing deformation and damage to the cylindrical body 32 connected to the lid 33 and the back anchor 34 supporting the lid 33, which may result in the packing 35 no longer being able to prevent the inflow of water and earth and sand, which may lead to the inflow of water and earth and sand into the arrival shaft 11. For this reason, it is important to stop the shield machine 12 at a predetermined position close to the lid 33.

[0033] The position of the shield machine 12 can be determined by underground surveying, and it is possible to stop it at a predetermined position. However, underground surveying alone carries the risk of pushing on the bulkhead 31 or back anchor 34 due to surveying errors. Therefore, a means is needed to confirm from the arrival shaft 11 side that the shield machine 12 is in the predetermined position.

[0034] In order to confirm from the arrival shaft 11 side whether the shield machine 12 is in the specified position, it is necessary to know the distance from the arrival shaft 11 side to the shield machine 12. Below, a device and method for detecting the distance from the arrival shaft 11 side to the shield machine 12 with high accuracy will be described in detail.

[0035] 4 shows a first example of the configuration of a device that detects the distance from the arrival side to the excavator. The distance detection device is a device for checking consistency with underground surveying, and is attached to the cover 33 of the bulkhead 31 to detect the distance to the shield machine 12.

[0036] The distance detection device includes a rod-shaped member, a conductive material, and a notification means. The rod-shaped member is arranged to protrude from the cover 33 of the bulkhead 31 installed in the arrival shaft 11 of the shield machine 12. The rod-shaped member is a plastic pipe 40 of a predetermined length made of plastic resin such as polyvinyl chloride. The plastic resin may be acrylonitrile butadiene styrene (ABS) resin, polyethylene, polypropylene, or the like. The rod-shaped member is not limited to the plastic pipe 40 as long as it is made of an insulating material and has a predetermined strength. The length of the plastic pipe 40 is, for example, 0.7 m, 1.0 m, 3.0 m, etc., but is not limited to these. Caps, also made of plastic resin such as polyvinyl chloride, are attached to both ends of the plastic pipe 40 to close the interior of the plastic pipe 40 to prevent water, soil, and the like from entering the interior.

[0037] The conductive member is a rod-shaped member made of a conductive material, and is provided so as to pass through the plastic pipe 40 and protrude from one end of the plastic pipe 40. The conductive member may be any rod-shaped member having conductivity, and examples thereof include a fully threaded member made of iron, copper, silver, gold, or an alloy thereof.

[0038] The conductive material is composed of, for example, two rod-shaped members, one of which (first conductive material 41) protrudes from one end and is supported at the center of the cross section of plastic pipe 40 so as to be movable in the longitudinal direction of plastic pipe 40 by a first cap 42 attached to that end, an inner tube 43 inserted inside plastic pipe 40 and closed at both ends with caps, and a cylindrical member 44 also inserted inside plastic pipe 40. Inner tube 43 and cylindrical member 44 close the inside of plastic pipe 40 and prevent the movement of water or sediment that may flow in through the hole in first cap 42 through which first conductive material 41 protrudes. The other of the two rod-shaped members (second conductive material 45) has a portion protruding from the other end and is supported at the center of the cross section of plastic pipe 40 by a second cap 46 attached to the other end.

[0039] The first conductive material 41 and the second conductive material 45 are disposed at a distance from each other and are each electrically connected to a notification means. When the first conductive material 41 protruding from one end of the plastic tube 40 is pushed into the plastic tube 40, it comes into contact with the second conductive material 45, and the current flowing from the notification means to the first conductive material 41 flows to the second conductive material 45 in contact with the first conductive material 41 and returns to the notification means. This completes an electrical circuit. The distance detection device shown in FIG. 4 is called a push-type sensor because it detects the electrical connection between the first conductive material 41 and the second conductive material 45 by being pushed into the plastic tube 40.

[0040] The notification means is connected to the first conductive material 41 and the second conductive material 45 via two signal lines 47 and 48. When the shield machine 12 contacts the first conductive material 41 protruding from one end of the plastic pipe 40, the first conductive material 41 is pushed into the plastic pipe 40 and contacts the second conductive material 45, forming an electrical circuit and notifying the operator that the state has switched from a non-energized state to a conductive state. The notification method used by the notification means may be any method capable of notifying the operator, but may be, for example, by lighting a rotating light. The notification method may be by sound output, or by both sound output and lighting the rotating light. An example of a notification method using both sound output and lighting the rotating light is a rotating light 49 that lights up a rotating light and sounds a buzzer. The rotating light 49 has a power source for supplying current to the signal lines 47 and 48.

[0041] For example, suppose the distance between the separated first conductive material 41 and second conductive material 45 is 0.05 m, and the distance from the lid 33 to the tip of the first conductive material 41 is 2.05 m. As the shield machine 12 advances, the bit 36 ​​of the cutter head 21 at the front of the shield machine 12 comes into contact with the first conductive material 41 protruding from one end of the plastic pipe 40, and pushes the protruding first conductive material 41 into the plastic pipe 40. As a result, the first conductive material 41 comes into contact with the second conductive material 45, an electrical circuit is formed, the rotating light 49 lights up, and the buzzer sounds.

[0042] When the rotating light 49 lights up and the buzzer sounds, the distance between the first conductive material 41 and the second conductive material 45 becomes 0, so the distance from the lid 33 to the tip of the first conductive material 41 is 2.05-0.05=2 m, and it can be detected that the tip of the bit 36 ​​of the cutter head 21 is located 2 m from the lid 33.

[0043] When the plastic pipe 40 is retracted into the arrival shaft 11 and the length protruding toward the shield machine 12 is 1.05 m, the rotating light 49 lights up, and the buzzer sounds, it can be detected that the distance from the lid 33 to the tip of the bit 36 ​​of the cutter head 21 is 1 m. Note that these distances are just examples, and the distance between the separated first conductive material 41 and second conductive material 45, and the distance from the lid 33 to the tip of the first conductive material 41 can be set arbitrarily.

[0044] 5, the distance detection device shown in Fig. 4 has a first extension 50 at the portion of the first conductive material 41 that protrudes from one end of the plastic pipe 40, and the first extension 50 is connected to a rotating light 49 by a signal line 47. The first conductive material 41 has a second extension 51 on the other end side of the plastic pipe 40 (the arrival shaft 11 side) than the first extension 50, and the second extension 51 has a diameter larger than the diameter of the hole formed in the first cap 42. For this reason, the second extension 51 does not move beyond the hole in the first cap 42 toward one end side of the plastic pipe 40 (the shield machine 12 side).

[0045] The first conductive material 41 has a third expansion section 52 and a fourth expansion section 53 on the arrival shaft 11 side of the second expansion section 51. An inner pipe 43, whose inner diameter is approximately the same as that of the main portion of the first conductive material 41 other than the expansion sections and whose outer diameter is smaller than the inner diameter of the plastic pipe 40, is inserted between the third expansion section 52 and the fourth expansion section 53, and a third cap 54 and a fourth cap 55 are attached to both ends of the inner pipe 43. The third cap 54 and the fourth cap 55 also have holes with approximately the same diameter as the main portion of the first conductive material 41, and their outer diameters are approximately the same as the inner diameter of the plastic pipe 40. This prevents water or sediment that has flowed into the plastic pipe 40 through the holes in the first cap 42 from moving toward the other end of the plastic pipe 40. The first conductive material 41 has a fifth extension portion closer to the arrival shaft 11 than the fourth extension portion 53, and the ring-shaped water-stopping member 56 is fixed by the fifth extension portion to prevent it from moving toward one end.

[0046] The second conductive material 45 has a sixth extension portion on the shield machine 12 side, and a ring-shaped water-stopping member 57 is fixed by the sixth extension portion to prevent movement toward the other end. The second conductive material 45 also has a seventh extension portion 58 on the other end side of the sixth extension portion. The seventh extension portion 58 is provided outside the plastic pipe 40, not inside the plastic pipe 40 that is closed by the second cap 46.

[0047] Between the water-stopping member 56 of the first conductive material 41 and the water-stopping member 57 of the second conductive material 45, a terminal end portion of the first conductive material 41 extending from the fifth extension portion toward the second conductive material 45 and a terminal end portion of the second conductive material 45 extending from the sixth extension portion toward the first conductive material 41 are inserted, and a first coil spring 59 is arranged so as to straddle the separated first conductive material 41 and second conductive material 45. A second coil spring 60 is arranged between the sixth extension portion and the second cap 46.

[0048] The first coil spring 59 contracts when the first conductive material 41 protruding from one end of the plastic pipe 40 comes into contact with the bit 36 ​​of the cutter head 21 at the front of the shield machine 12 and the first conductive material 41 is pushed into the plastic pipe 40. The contraction of the first coil spring 59 causes the end of the first conductive material 41 and the tip of the second conductive material 45 to come into contact inside the plastic pipe 40.

[0049] The first extension 50 of the first conductive material 41 is connected to the rotating light 49 by a signal line 47, and the seventh extension 58 of the second conductive material 45 is connected to the rotating light 49 by a signal line 48. When the first conductive material 41 and the second conductive material 45 come into contact with each other, an electrical circuit is formed, the rotating light 49 lights up, and a buzzer sounds to notify the user that the distance from the arrival shaft 11 is a predetermined distance.

[0050] Furthermore, even if the shield machine 12 is stopped immediately upon detecting that the rotating light 49 has turned on and the buzzer has sounded, it does not stop immediately. For this reason, the shield machine 12 continues to excavate during this time, with the first conductive material 41 continuing to push the second conductive material 45. However, the second conductive material 45 is able to move toward the arrival shaft 11 due to the contraction of the second coil spring 60, which prevents the first conductive material 41, the second conductive material 45, or both, from bending and breaking along the way.

[0051] The buzzer may continue to ring while the rotating light is on, may ring only once for a certain period of time and then stop, or may ring at certain intervals.

[0052] For example, suppose the distance between the separated first conductive material 41 and second conductive material 45 is 0.05 m, and the distance from the lid 33 to the tip of the first conductive material 41 is 2.05 m. Then, when the first conductive material 41 comes into contact with the second conductive material 45 and is pushed in, the distance from the lid 33 to the tip of the first conductive material 41 becomes 2.05-0.05=2 m, and even if the second coil spring 60 subsequently contracts, it is only a small distance, so it can be detected that the distance from the lid 33 to the tip of the bit 36 ​​of the cutter head 21 after being pushed in is approximately 2 m.

[0053] Incidentally, when the cutter head 21 of the shield machine 12 is moved away from the first conductive material 41, the first coil spring 59 and the second coil spring 60 extend, the first conductive material 41 and the second conductive material 45 are separated, the electrical connection is released, the rotating light 49 goes out, and the buzzer stops.

[0054] The speed at which the cutter head 21 moves in the excavation direction is several millimeters to several centimeters per minute, so when the plastic pipe 40 comes into contact with the bit 36 ​​of the cutter head 21, it will not be cut or broken by the bit 36 ​​of the cutter head 21.

[0055] 6A and 6B are diagrams showing the external appearance of a portion of the distance detection device and how it is attached to the bulkhead 31. As shown in Fig. 6A, the distance detection device has a plastic pipe 40 as a rod-shaped member, a first cap 42 and a second cap 46 attached to both ends of the plastic pipe 40, a first conductive member 41 provided to pass through the first cap 42, and a second conductive member 45 provided to pass through the second cap 46.

[0056] As shown in Figure 6(b), the distance detection device is attached to the cover 33 of the bulkhead 31 by inserting it into a hole in a valve 37 provided in the cover 33. Although the plastic pipe 40 has a certain degree of strength, it is difficult to insert and install it in hard ground. Therefore, a core drill or other core extraction machine is used to drill a hole of a diameter that allows the plastic pipe 40 to be inserted, and the plastic pipe 40 is then inserted into the hole for installation. Therefore, the plastic pipe 40 used for distance detection can be removed from the cover 33 by pulling it out through the hole in the valve 37. After the plastic pipe 40 is removed, the valve 37 is closed to prevent soil and sand on the shield machine 12 side of the cover 33 from flowing into the arrival shaft 11.

[0057] Fig. 7 is a diagram showing a second example of the configuration of a device for detecting the distance from the reach side to the excavator. Similar to the configuration shown in Fig. 3, the distance detection device includes a rod-shaped member, a conductive material, and a notification means. The rod-shaped member is similar to the rod-shaped member shown in Fig. 3, and is, for example, a plastic tube 40. Both ends of the plastic tube 40 are closed by a first cap 42 and a second cap 46.

[0058] Conductive materials are wires (conductors) made from conductive materials such as iron, copper, silver, gold, or alloys of these. The wires are covered with an insulator such as polyethylene, polyvinyl chloride, or silicone to prevent short circuits, electric shock, or fire.

[0059] The conductive material is installed as a conductor (signal wire 70) coated with an insulator, passing through the second cap 46 from the arrival shaft 11 side, passing through the inside of the plastic pipe 40, passing through the first cap 42, turning back after emerging from the first cap 42, passing through the first cap 42 again, passing through the inside of the plastic pipe 40, and passing through the second cap 46. Therefore, the first cap 42 and the second cap 46 are provided with at least two holes through which the signal wire 70 can be inserted, and only the folded-back portion of the signal wire 70 protrudes slightly from the first cap 42 of the plastic pipe 40. The at least two holes provided in the first cap 42 have approximately the same diameter as the signal wire 70.

[0060] The signal line 70 passing through the second cap 46 is electrically connected to the rotating light 49 .

[0061] Current flows through the signal line 70 and the rotating light 49 remains lit until the bit 36 ​​of the cutter head 21 comes into contact with the folded portion of the signal line 70 protruding from one end of the plastic tube 40. During this time, the buzzer may continue to sound, or may sound once for a fixed period of time and then stop, or may sound at fixed intervals.

[0062] Meanwhile, as the shield machine 12 excavates, when the bit 36 ​​of the cutterhead 21 comes into contact with the folded portion of the signal line 70 protruding from one end of the plastic pipe 40, the bit 36 ​​of the cutterhead 21 cuts the signal line 70 at that folded portion, and the rotating light 49 goes out. Therefore, when the rotating light 49 switches from on to off, it can be determined that the bit 36 ​​of the cutterhead 21 has reached one end of the plastic pipe 40. At this time, it can be seen that the distance from the lid 33 to the tip of the bit 36 ​​of the cutterhead 21 is equal to the length of the plastic pipe 40 protruding from the lid 33. The distance detection device shown in Figure 7 is called a cutting sensor because it detects distance when the push-back portion of the signal line 70 protruding from the plastic pipe 40 is cut and the light switches from on to off.

[0063] 8 is a diagram showing the external appearance of a portion of the distance detection device shown in FIG. 7 and how it is attached to bulkhead 31. As shown in FIG. 8(a), a first cap 42 is attached to one end of plastic tube 40, and first cap 42 has two holes. Signal line 70 is temporarily taken out from inside plastic tube 40 through one hole and then returned to the inside through the other hole, forming a folded-back portion of signal line 70 on the outside of first cap 42.

[0064] As shown in Figure 8(b), the distance detection device is attached to the lid 33 by inserting it into a hole in a valve 37 provided in the lid 33. Although the plastic pipe 40 has a certain degree of strength, it is difficult to insert and install it in hard ground. Therefore, a core drill or other core extraction machine is used to drill a hole of a diameter that allows the plastic pipe 40 to be inserted, and the plastic pipe 40 is then inserted into the hole for installation.

[0065] 9 is a diagram showing the installation of notification means. A plurality of plastic pipes 40 are installed on the lid 33. The same number of rotating lights 49 as the number of plastic pipes 40 are installed on the lid 33. Each plastic pipe 40 is connected to each rotating light 49 by a signal line 70.

[0066] In the example shown in Fig. 9, three yellow rotating lights 49a and one red rotating light 49d are installed as rotating lights 49. Yellow rotating lights 49a to 49c are connected to the cutting sensor shown in Fig. 7 by signal line 70. Red rotating light 49d is connected to the push-type sensor shown in Fig. 4 by signal lines 47 and 48. The cutting sensors connected to the three yellow rotating lights 49a to 49c have plastic pipes 40 with lengths of 0.7 m, 1.0 m, and 3.0 m. The push-type sensor connected to red rotating light 49d has a plastic pipe 40 with a length of 1.0 m.

[0067] In the example shown in Figure 9, the bit 36 ​​of the cutter head 21 from the lid 33 cuts the signal line 70 of the 1.0 m cutting sensor, the 1.0 m yellow rotating light 49b goes out, the first conductive material 41 of the 1.0 m push-type sensor is pushed in, and the 1.0 m red rotating light 49d goes on.

[0068] FIG. 10 is a diagram showing an example of the positions at which distance detection devices are attached to bulkhead 31. Lid 33 is a substantially circular lid with a predetermined thickness, and distance detection devices are installed in, for example, five locations. The distance detection device may use only the push-type sensor shown in FIG. 4, or only the cutting sensor shown in FIG. 7, or may use both the push-type sensor and the cutting sensor. In the example shown in FIG. 10, push-type sensors 80 and 81 and cutting sensors 82 to 84 are used in combination.

[0069] The push type sensors 80 and 81 use plastic pipes 40 with a length of 1.0 m, and the cutting sensors 82 to 84 use plastic pipes with lengths of 0.7 m, 1.0, and 3.0 m.

[0070] Figure 10 shows the cover 33 when viewed from inside the arrival shaft 11 toward the shield machine 12, with a 0.7 m cutting sensor 82 installed on the left side of the center of the top end of the cover 33, 1.0 m push-type sensors 80 and 81 installed on the left and right sides of the center of the cover 33, a 3.0 m cutting sensor 84 installed at the lower left end of the center of the cover 33, and a 1.0 m cutting sensor 83 installed at the lower right end of the cover.

[0071] In this configuration, the 3.0 m cutting sensor 84 first detects that the distance between the tip of the bit 36 ​​of the cutter head 21 and the lid 33 is, for example, 2 m. While 2 m is used as an example here, the distance is not limited to 2 m. After detecting a distance of 2 m, the length of protrusion from the lid 33 may be changed to detect a distance of 1.5 m, for example. The 3.0 m cutting sensor 84 is then pulled out, and the 1.0 m push-type sensors 80, 81 and 1.0 m cutting sensor 83 detect that the distance between the tip of the bit 36 ​​of the cutter head 21 and the lid 33 is, for example, 0.5 m. If the 1.0 m push-type sensors 80, 81 and cutting sensor 83 detect contact at approximately the same time, it is determined that the surface of the cutter head 21 and the surface of the lid 33 are approximately parallel.

[0072] The 1.0 m push-type sensors 80, 81 and cutting sensor 83 are pulled out, the shield machine 12 is moved forward, and the 0.7 m cutting sensor 82 detects that the distance between the tip of the bit 36 ​​of the cutter head 21 and the lid 33 is, for example, 0.1 m. This allows the shield machine 12 to be stopped at a predetermined position 0.1 m from the lid 33. After the sensors are pulled out, the valve 37 is closed to prevent the inflow of water and earth and sand.

[0073] 10, the distance is checked in three stages, but this is not limited to this and the distance may be checked in one stage, two stages, or four or more stages. The positions at which the distance is checked are not limited to the above five locations and may be one to four locations, or six or more locations.

[0074] FIG. 11 is a flowchart showing an example of a process for detecting the distance to the shield machine 12 using a distance detection device. This process detects the distance using the push-type sensor shown in FIG. 3. The process starts at step 100 when the distance detection device is attached to the cover 33 and powered on. In step 101, the rotating light 49 sends a current to the first conductive material 41 via the signal line 47. In step 102, the bit 36 ​​of the cutter head 21 contacts the first conductive material 41 and pushes the first conductive material 41 into the plastic pipe 40. In step 103, the first conductive material 41 contacts the second conductive material 45 inside the plastic pipe 40. In step 104, a current flows from the first conductive material 41 to the second conductive material 45. The current flowing to the second conductive material 45 returns to the rotating light 49 via the signal line 48. In step 105, rotating light 49 detects the electrical connection between first conductive material 41 and second conductive material 45, lights up, and sounds a buzzer, and the process ends in step 106. As a result, the distance from lid 33 to the tip of first conductive material 41 is detected as the distance to shield machine 12.

[0075] FIG. 12 is a flowchart showing another example of a process for detecting the distance to the shield machine 12 using a distance detection device. This process detects the distance using the cutting sensor shown in FIG. 7. The process starts at step 200 by attaching the distance detection device to the cover 33 and turning on the power. In step 201, the rotating light 49 passes current through the signal line 70, turning on the rotating light. At this time, a buzzer may also be sounded. In step 202, the bit 36 ​​of the cutter head 21 contacts and cuts the signal line 70. As a result of the cutting of the signal line 70, in step 203, the rotating light 49 detects the release of the electrical connection between the first conductive material 41 and the second conductive material 45, turns off the rotating light, and in step 204, the process ends. As a result, a distance equal to the length of the plastic pipe 40 protruding from the cover 33 is detected as the distance to the shield machine 12.

[0076] A test was conducted using two cutting sensors to confirm the accuracy of distance detection. The results are shown below. For the first cutting sensor, a 3.0 m cutting sensor was used, and the planned jack stroke was set to 3000 mm. The cutter head 21 was rotated, the jack 26 was activated, and the cutter head 21 was advanced. If everything went as planned, the signal line 70 would be cut at a position 3000 mm away from the lid 33, and the rotating light 49 would switch from on to off. However, the rotating light 49 switched from on to off when the jack stroke was 3025 mm.

[0077] For the second line, a 1.0 m cutting sensor was used, and with a planned jack stroke of 544 mm, cutter head 21 was rotated, jack 26 was activated, and cutter head 21 was advanced. If everything went as planned, signal line 70 would have been cut at a position 544 mm away from lid 33, and rotating light 49 would have switched from on to off, but in fact, rotating light 49 switched from on to off when the jack stroke was 581 mm.

[0078] From these results, it was found that the error, which is the difference between the planned jack stroke and the distance from the cover 33 where the signal line 70 was actually cut, was 25 mm for the first line and 37 mm for the second line, and that this was sufficiently effective since the stopping position of the shield machine 12 was planned with the distance from the bit of the cutter head 21 to the cover 33 being 100 mm.

[0079] In this way, it is possible to confirm whether the shield machine 12 has reached the intended position, which prevents the shield machine 12 from pushing against the bulkhead 31 or back anchor 34, which would cause the bulkhead 31 or back anchor 34 to deform or break, and prevents water and earth and sand from flowing into the arrival shaft.

[0080] Incidentally, in the cutting sensor illustrated in Figure 7, multiple plastic tubes 40 of different lengths are prepared to detect the distance from the bit of the cutter head 21 to the lid 33, but this requires a large number of cutting sensors.

[0081] Therefore, an example of the configuration of a distance detection device that uses the same cutting sensor but can detect multiple arrival positions with a single sensor is shown in Figure 13. Figure 13(a) is a diagram showing the overall configuration of arrival detection sensor 90 as a distance detection device, and Figure 13(b) is a diagram showing the internal configuration of arrival detection sensor 90.

[0082] As shown in Fig. 13(a), the arrival detection sensor 90 includes a hollow cylindrical first case 91 and a second case 92 corresponding to the plastic pipe 40, and a substrate 93. A portion of the first case 91 is inserted into the second case 92, and the substrate 93 is housed within the first case 91. The first case 91 and the second case 92 may be plastic pipes or may be anodized aluminum cases, etc., as long as they are insulating cases.

[0083] As shown in FIG. 13(b), the substrate 93 is provided with a plurality of detection wires 94 and one common return wire 95. Each detection wire 94 extends along the longitudinal direction of the first case 91, with its tip bent at approximately 90 degrees at each predetermined position in the longitudinal direction and connected to the single common return wire 95. Positions in the longitudinal direction of the first case 91 corresponding to the tip of each detection wire 94 bent at approximately 90 degrees at each predetermined position on the first case 91 are indicated by dashed lines as separators 96, indicating that the detection wire 94 is cut at that position. In FIG. 13(b), seven detection wires 94 numbered "1" to "7" and a common return wire 95 labeled "COM" are shown, which are connected to a cord 97 leading to the rotating light 49. The predetermined positions may be spaced apart at regular intervals, for example, 50 mm apart from the lid 33, or may be spaced apart from the lid 33 at different intervals. 13(b), the spacing is narrower on the side closer to the lid 33, and the spacing becomes wider toward the tip of the arrival detection sensor 90, which is farther from the lid 33. This makes it possible to detect the stopping position of the excavator close to the lid 33 with higher accuracy.

[0084] 13(a), in the arrival detection sensor 90, each detection line 94 and the common return line are connected to a cord 97 within a second case 92, and this portion serves as a wiring section 98. Meanwhile, the first case 91 is the portion that is cut by the bit 36 ​​and wears away, and therefore serves as a wear section 99. A waterproof rubber gasket is provided between the wiring section 98 and the wear section 99 as a waterproof member to prevent water that has flowed into the first case 91 from entering the second case 92. A cap is provided on the second case 92 to close the side where the cord 97 is inserted, and a rubber cord gasket is provided between the second case 92 and the cap as a waterproof member to prevent water from entering from the cap side.

[0085] The arrival detection sensor 90 is installed so that the wear section 99 side protrudes from the cover 33 towards the advancing shield machine 12, and the wiring section 98 is positioned inside the arrival shaft 11. While the bit 36 ​​of the cutter head 21 of the shield machine 12 has not yet reached the arrival detection sensor 90, current flows from each detection wire 94 to the common return wire 95, and all of the rotating lights 49 connected to each detection wire 94 via cords 97 are turned on.

[0086] When the bit 36 ​​of the cutter head 21 of the shield machine 12 reaches the arrival detection sensor 90, the bit 36 ​​cuts the base plate 93, and the wear portion 99 wears away, the detection wires 94 farthest from the cover 33 become exposed, and the exposed detection wires 94 are cut by the bit 36. Current no longer flows from the cut detection wires 94 to the common return wire 95, so the rotating lights 49 go out one by one.

[0087] Since the distance from the lid 33 to the position where the tip of each detection wire 94 is located is known, it is possible to identify the detection wire 94 that was electrically connected to the rotating light 49 that was just turned off, and detect the distance from the lid 33 to the identified detection wire 94 as the distance from the lid 33 to the bit 36 ​​of the cutter head 21. The space within the first case 91 may be filled with a filler such as cement that is worn away by the bit 36 ​​together with the first case 91 and the substrate 93.

[0088] 14 is a diagram illustrating a method for installing the arrival detection sensor 90 on the lid 33. The arrival detection sensor 90 is placed on a sensor holder 100 and fixed in place with a hemp string 101 as a string-like member. The sensor holder 100 has a flat surface on which the arrival detection sensor 90 can be placed, and is made of a material that will be worn away by the bit 36 ​​of the cutter head 21 of the shield machine 12, just like the wear part 99 of the arrival detection sensor 90. The sensor holder 100 can be a plate-like member that is rectangular in cross section and long on one side, made of a resin such as polyurethane or polystyrene, for example.

[0089] The arrival detection sensor 90 fixed to the sensor receiving base 100 is attached to the lid 33, and therefore a sensor base 102 is attached to the lid 33. The sensor base 102 is adjacent to a part of the sensor receiving base 100 and is composed of a support member 103 that supports the sensor receiving base 100, and an inclined member 104 that connects the support member 103 and the surface of the lid 33 at an angle.

[0090] The arrival detection sensor 90 is attached to a lid 33 installed on the arrival shaft 11 side of the cylindrical body 32 using a sensor support 100 and a sensor mount 102. The end of the cylindrical body 32 on the shield machine 12 side is set as the underground joint position with the shield tunnel constructed by the shield machine 12, and the stopping position of the shield machine 12 is set as a position 100 mm before the tip of the bit 36 ​​of the cutter head 21 reaches the underground joint position, for example.

[0091] Fig. 15 is a diagram illustrating a method for detecting the arrival position of the shield machine 12 using the arrival detection sensor 90. Fig. 18(a) is a diagram showing the state before the bit 36 ​​of the cutter head 21 of the shield machine 12 comes into contact with the arrival detection sensor 90. Fig. 18(b) is a diagram showing the state when the bit 36 ​​of the cutter head 21 comes into contact with the arrival detection sensor 90, the arrival detection sensor 90 wears, and the shield machine 12 reaches the stop position.

[0092] The shield machine 12 moves toward the location where the cylindrical body 32 of the arrival shaft 11 is installed. The arrival detection sensor 90 may detect the distance from the cover 33 to the tip of the bit 36, or may detect the distance from the underground joint position to the tip of the bit 36. In the example shown in Figure 15, the underground joint position is set as the reference position, and the sensor is configured to detect the distance from the reference position to the tip of the bit 36.

[0093] As the shield machine 12 advances in the excavation direction, it comes into contact with the tip of the sensor receptacle 100 that protrudes most toward the shield machine 12, scrapes away the sensor receptacle 100, and then comes into contact with the tip of the arrival detection sensor 90. The shield machine 12 continues to advance, scraping away from the tip of the arrival detection sensor 90, and reaches the first separator 96. The shield machine 12 uses the bit 36 ​​of the rotating cutter head 21 to cut the detection line 94 that is located at the position of the first separator 96. The rotating light 49 connected to that detection line 94 then goes out. As a result, the distance from the underground joint position to the first detection line 94 is taken as the distance to the current bit 36 ​​of the cutter head 21, and the current position of the shield machine 12 can be detected.

[0094] As the shield machine 12 advances, it reaches the next separator 96, cuts the detection line 94 in the same way, and the rotating light 49 connected to that detection line 94 goes out. This is repeated, cutting the arrival detection sensor 90 and sensor holder 100, and when it detects that it has reached a stopping position 100 mm before the underground joint position, the shield machine 12 stops excavating.

[0095] The arrival detection sensor 90 may be attached to only one location on the lid 33, but it is preferable to attach it to two or more locations to improve detection accuracy. The location where the sensor is attached to the lid 33 may be anywhere, but if two or more locations are attached, it is preferable to attach them as far apart as possible.

[0096] Up to this point, we have used a rotating light as the notification means, but distance can also be notified using a display panel 110 as display means as shown in Figure 16. The display panel 110 can display the position where the arrival detection sensor 90 is attached and the status of the sensor, and can display the remaining cutting amount as a distance (mm) with the stop position being 0 mm. Therefore, the position when the distance becomes 0 mm becomes the stop position. The position where the arrival detection sensor 90 is attached is the vertical position of the lid 33, such as the top, center, or bottom, and the status indicates the state of the sensor, such as whether it is detecting or waiting.

[0097] When the display panel 110 is used as the notification means, a resistor is added to each detection line 94, the current value due to the combined resistance when connected in parallel is measured, and the distance is detected from the measured current value and displayed on the display panel 110. For this reason, it is possible to separately provide each resistor connected to each detection line 94, a current measuring means for measuring the current value due to the combined resistance, and a conversion means for converting the measured current value into distance.

[0098] The display panel 110 is configured so that the area indicating the distance range emits light so that the current distance range can be seen at a glance. In the example shown in Fig. 16, the current distance is 900 mm, so the area indicating the range of 900-250 mm emits light. This allows the user to check both the displayed distance and the illuminated area indicating the distance range.

[0099] The display panel 110 shown in Figure 16 is configured to display not only distance but also position, status, current value, and distance range, but is not limited to this and may display only distance, or a combination of distance and at least one of these, or a combination of distance and other information, or a combination of distance, at least one of these, and other information.

[0100] The distance detection device and distance detection method of the present invention have been described in detail above with reference to the embodiments shown in the drawings, but the present invention is not limited to the above-described embodiments and can be modified within the scope of what a person skilled in the art can conceive, such as other embodiments, additions, modifications, deletions, etc., and any aspect is within the scope of the present invention as long as it achieves the functions and effects of the present invention. [Explanation of symbols]

[0101] 10...Departure shaft 11…Achievement shaft 12...Shield machine 13...Entrance 14...Reaction receiver 15...Cradle 20...Skin plate 21...Cutter head 22...Partition wall part 23...Chamber 24...Drive unit 25...Screw conveyor 26...Jack 27...segments 28...Erector 29…Backfill injection device 30...Earth retaining wall 31...Bulkhead 32...Cylindrical body 33…Lid 34...Back anchor 35...Gasket 36...bit 37...Valve 40...Plastic pipe 41...First conductive material 42...First Cap 43…Inner pipe 44...Cylindrical member 45...Second conductive material 46...Second Cap 47, 48...Signal wire 49...Revolving light 50...First extension 51...Second extension 52...Third extension 53...Fourth extension 54...Third Cap 55...Fourth Cap 56, 57...Water-stopping member 58...7th extension 59...First coil spring 60...Second coil spring 70...Signal line 80, 81...Push-type sensors 82~84...Cutting sensor 90... Arrival detection sensor 91...First case 92...Second Case 93... Circuit board 94...Detection line 95...Common return 96...Separator 97…Code 98…Wiring section 99...Wear area 100...Sensor holder 101...Hemp string 102...Sensor stand 103...Support member 104...Diagonal member

Claims

1. A device for detecting the distance to an excavator, a rod-shaped member provided so as to protrude from a partition wall installed on the reach side of the excavator; a conductive material provided within the rod-shaped member or protruding from one end of the rod-shaped member; a notification means connected to the conductive material and notifying that the conductive material has been switched from a conducting state to a non-conducting state or from a non-conducting state to a conducting state due to contact of the excavator with the conductive material; A distance detection device comprising:

2. the conductive material includes a first conductive material, a portion of which protrudes from one end of the rod-shaped member, and a second conductive material, which is disposed spaced apart from the first conductive material, and the first conductive material and the second conductive material are each electrically connected to the notification means; 2. The distance detection device of claim 1, wherein the notification means detects an electrical connection between the first conductive material and the second conductive material when the excavator comes into contact with the first conductive material protruding from one end of the rod-shaped member and pushes the first conductive material into the rod-shaped member, and notifies that a non-conductive state has been switched to a conductive state.

3. a coil spring that connects the first conductive material and the second conductive material in a spaced-apart state; the excavator comes into contact with the first conductive material and pushes the first conductive material into the rod-shaped member, causing the coil spring to contract and the first conductive material to come into contact with the second conductive material; 3. The distance detection device according to claim 2, wherein the coil spring expands when the excavator moves away from the first conductive material, and the first conductive material moves away from the second conductive material.

4. the conductive material is a conductor, The conductive wire has a central folded portion protruding from one end of the rod-shaped member, and both ends electrically connected to the notification means, 2. The distance detection device according to claim 1, wherein the notification means detects that the excavator has come into contact with the folded portion and the conductor has been cut, and notifies that the state has switched from a conducting state to a non-conducting state.

5. the conductive material includes a plurality of detection lines electrically connected to the notification means and one common return line; Within the rod-shaped member, the plurality of detection lines and the common return line extend along the longitudinal direction of the rod-shaped member, and a tip of each detection line is bent at a predetermined position in the longitudinal direction and connected to the common return line, The distance detection device described in claim 1, wherein the notification means detects that the detection line it has come into contact with has been cut when the excavator cuts from one end of the rod-shaped member and contacts the tip of each detection line in turn, and notifies that the state has changed from an energized state to a de-energized state to indicate that the excavator has reached the position where the tip of the detection line is located.

6. The distance detection device according to any one of claims 1 to 5, wherein the notification means notifies that a power state has been switched from a non-powered state to a powered state by turning on the light, and notifies that a power state has been switched from a powered state to a non-powered state by turning off the light.

7. 1. A method for detecting distance to an excavator, comprising: a step of installing a rod-shaped member so as to protrude from a partition wall installed on the reach side of the excavator, the rod-shaped member having a conductive material protruding from one end thereof; a step in which a notification means connected to the conductive material notifies that the conductive material has been switched from a conductive state to a non-conductive state or from a non-conductive state to a conductive state due to contact of the excavator with the conductive material; A distance detection method comprising:

8. the conductive material includes a first conductive material, a portion of which protrudes from one end of the rod-shaped member, and a second conductive material, which is disposed at a distance from the first conductive material, and the first conductive material and the second conductive material are each electrically connected to the notification means; 8. The distance detection method of claim 7, wherein in the notifying step, the notifying means detects an electrical connection between the first conductive material and the second conductive material by the excavator coming into contact with the first conductive material protruding from one end of the rod-shaped member and pushing the first conductive material into the rod-shaped member, and notifies that a non-conductive state has been switched to a conductive state.

9. the conductive material includes a plurality of detection lines electrically connected to the notification means and one common return line; Within the rod-shaped member, the plurality of detection lines and the common return line extend along the longitudinal direction of the rod-shaped member, and a tip of each detection line is bent at a predetermined position in the longitudinal direction and connected to the common return line, The distance detection method described in claim 7, wherein in the notifying step, the notifying means detects that the detection line it has come into contact with has been cut as the excavator cuts from one end of the rod-shaped member and contacts the tip of each detection line in turn, and notifies that the state has switched from a powered state to a non-powered state to indicate that the excavator has reached the position where the tip of the detection line is located.

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