Sensor cable laying method

Abstract

To suppress action of compression load on a sensor cable when the sensor cable is laid inside a hole.SOLUTION: A laying method of a sensor cable 2 has: a laying tube laying step: and a sensor cable laying step. The laying tube laying step has: a pully attachment step of attaching, inside a base tube 1a, a pully 20 around which a wire rope 4 is installed; a base tube insertion step of inserting the base tube 1a into a drilled hole H; a first insertion step of inserting the wire rope 4 into a coupling tube 1b coupled to the base tube 1a; and a first coupling step of inserting the coupling tube 1b, which has the wire rope 4 being inserted in the first insertion step coupled to the base tube 1a, into the drilled hole H. The sensor cable laying step has: a cable connection step of connecting the sensor cable 2 to one end side of the wire rope 4; and a pulling step of pulling the sensor cable 2 into the base tube 1a by tugging other end side of the wire rope 4, and laying the sensor cable inside a laying tube 1.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for laying a sensor cable.

Background Art

[0002] Patent Document 1 discloses a method of extruding a flexible tube in which an optical fiber is laid by a rotary extrusion device and inserting it into a hole.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A sensor cable such as an optical fiber is weaker in resistance to a compressive load than in resistance to a tensile load. For this reason, when the length of the sensor cable becomes long and the sensor cable is pushed in as in the method disclosed in Patent Document 1, the compressive load acting on the sensor cable increases, and the sensor cable may be damaged.

[0005] An object of the present invention is to suppress the action of a compressive load on a sensor cable when laying the sensor cable in a hole.

Means for Solving the Problems

[0006] The present invention relates to a method for laying a sensor cable, which includes a laying pipe laying process of laying a laying pipe into a hole and a sensor cable laying process of laying a sensor cable into the laying pipe. The laying pipe laying process includes a pulley mounting process of mounting a pulley with a wire rope installed inside a base pipe, a base pipe insertion process of inserting the base pipe into the hole, a first insertion process of inserting the wire rope through a first connecting pipe connected to the base pipe, and a first connection process of connecting the first connecting pipe through which the wire rope is inserted in the first insertion process to the base pipe and inserting it into the hole. The sensor cable laying process includes a cable connection process of connecting the sensor cable to one end side of the wire rope and a drawing-in process of pulling the other end side of the wire rope to draw the sensor cable to the base pipe and lay it in the laying pipe.

Effects of the Invention

[0007] According to the present invention, when laying the sensor cable into the hole, it is possible to suppress the action of a compressive load on the sensor cable.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] The present invention relates to a laying method for laying a laying pipe 1 and a sensor cable 2 laid in the laying pipe 1 in a bored hole H bored in the ground G.

[0011] In the laying method of the present embodiment, after laying the laying pipe 1 in the bored hole H (see FIG. 2 etc.) bored by the boring rod 3, the sensor cable 2 is laid. In the present embodiment, the boring rod 3 is removed from the bored hole H after laying the laying pipe 1 in the bored hole H. In the present embodiment, the back side of the bored hole H is referred to as "front", and the front side of the bored hole H is referred to as "back".

[0012] The sensor cable 2 is, for example, an optical fiber cable used for a linear in-situ displacement meter capable of detecting the displacement of the ground G. Since the in-situ displacement meter using the optical fiber cable has a known configuration, detailed illustration and description are omitted. For example, one or a plurality of optical fiber cables are spirally wound in the axial direction (longitudinal direction) inside the sheath material. When a plurality of optical fiber cables are used, they are spirally wound with different phases from each other.

[0013] Since the optical fiber cable generates strain in response to the strain in the ground and the loosening of the ground G, it is possible to measure the strain in the ground and the loosening of the ground G by measuring the strain of the optical fiber cable.

[0014] Specifically, the optical fiber cable has the property of slightly backscattering the incident pulsed light. By utilizing this property, it is possible to measure the strain at multiple positions in the optical fiber cable. Since the frequency of the scattered light depends on the strain of the optical fiber cable, the strain of the optical fiber cable can be measured by injecting pulsed light into the optical fiber cable and measuring the frequency of the scattered light. Also, by measuring the time from when pulsed light is injected into the optical fiber cable until the scattered light generated within the optical fiber cable returns to the incident position, it is possible to measure the position where the scattered light is generated, that is, the position where strain occurs in the optical fiber cable.

[0015] Therefore, by inserting a ground displacement meter including an optical fiber cable into the boring hole H, the displacement of the ground G can be grasped by measuring the strain generated in the optical fiber cable. In this embodiment, although the sensor cable 2 is laid within the laying pipe 1, the rigidity of the laying pipe 1 is higher than that of the sensor cable 2. Further, the sensor cable 2 is positioned on the bottom side of the laying pipe 1 due to its own weight. For this reason, when the ground G is displaced, the sensor cable 2 is displaced together with the laying pipe 1. Therefore, even with the configuration of this embodiment, the displacement of the ground G can be measured by the sensor cable 2.

[0016] The laying pipe 1 has a base pipe 1a and a plurality of connecting pipes 1b sequentially connected to the base pipe 1a. The laying pipe 1 (base pipe 1a, connecting pipe 1b) is constituted by, for example, a hollow pipe made of vinyl chloride. The base pipe 1a, the connecting pipe 1b, and the connecting pipes 1b are connected by, for example, screw connection. The base pipe 1a and the connecting pipe 1b are, for example, those having a length of about 2 m and an outer diameter of about 50 mm.

[0017] On the tip side of the base pipe 1a, a pulley 20 is attached which is disposed inside the base pipe 1a and to which a wire rope 4 described later is installed. The pulley 20 is rotatably supported by a cap member 21 attached so as to close the opening on the tip side of the base pipe 1a.

[0018] The cap member 21 is made of a metal material such as aluminum, for example, and is fixed to the opening at the tip side of the base pipe 1a by screw connection.

[0019] Next, the laying method of this embodiment will be specifically described. As a rough flow, first, the drilling hole H is drilled by the drilling rod 3. Next, the laying pipe 1 is laid in the drilled drilling hole H (drilling rod 3), and then the drilling rod 3 is removed. And finally, the sensor cable 2 is laid in the laying pipe 1. The operations will be described in more detail below.

[0020] First, with reference to FIG. 2, the method of drilling the drilling hole H will be described.

[0021] The drilling hole H is drilled horizontally by the drilling rod 3. As shown in FIG. 2, the drilling rod 3 has a base rod 3a with a bit 3c attached to its tip, and a connecting rod 3b sequentially connected to the base end (rear end) side of the base rod 3a.

[0022] The base rod 3a and the connecting rod 3b are made of, for example, a steel hollow pipe. The base rod 3a and the connecting rod 3b are formed to have a length of about 3 to 4 m, for example. A hollow pipe having an inner diameter that has a gap with the laying pipe 1 inserted therein, specifically, an inner diameter that provides a gap of at least about 5 mm or more, is used.

[0023] The drilling rod 3 is applied with a rotational force and an impact force by a driving device 30. The driving device 30 has a rotation mechanism (not shown) with a hydraulic motor (not shown) as a driving source, and a hydraulic impact piston (not shown).

[0024] The rotation mechanism applies a rotational force to the bit 3c via the drilling rod 3. The rotation mechanism is configured such that the rotation speed and the rotation direction can be controlled.

[0025] The impact piston applies an impact force to the bit 3c via the boring rod 3. The impact piston is arranged coaxially with the boring rod 3 and repeatedly collides with the proximal end side of the boring rod 3 to apply an impact force in the axial direction (front-rear direction) of the boring rod 3 to the bit 3c.

[0026] The bit further drills the borehole H drilled in the ground G deeper by the rotational force and impact force applied by the drifter.

[0027] In this embodiment, while sequentially connecting the connecting rod 3b behind the base rod 3a to extend the boring rod 3, the borehole H is drilled in the ground G. The borehole H is set to a length of, for example, about 100 m to 200 m, and the connecting rod 3b is connected until the borehole H reaches the set length, and the borehole H is drilled forward.

[0028] Next, a method of laying the laying pipe 1 in the borehole H (laying pipe laying process) will be described.

[0029] When the borehole H is drilled to the set length, the laying pipe 1 is laid in the borehole H.

[0030] First, as shown in FIG. 3, a wire rope 4 is installed on a pulley 20 supported by a cap member 21. And in this state, the cap member 21 is attached to the opening on the tip side of the base pipe 1a. This process corresponds to the "pulley attachment process" in the claims.

[0031] Next, the base pipe 1a is pushed into the borehole H from the cap member 21 side, specifically, into the boring rod 3 (see FIG. 4(A)). This process corresponds to the "base pipe insertion process" in the claims.

[0032] Once the base pipe 1a is pushed into the hole drilling rod 3 to a certain extent, a connecting pipe 1b (first communication pipe) is connected to the proximal end (rear) side of the base pipe 1a. At this time, as shown in Fig. 4(A), before connecting the connecting pipe 1b, a wire rope 4 is inserted through the connecting pipe 1b to be connected. Note that the process of inserting the wire rope 4 through the connecting pipe 1b to be connected before connecting the connecting pipe 1b corresponds to the "first insertion process" in the claims.

[0033] Then, the base pipe 1a and the connecting pipe 1b connected to the base pipe 1a are pushed into the hole drilling rod 3 (see Fig. 4(B)). Note that the process of connecting the connecting pipe 1b (first communication pipe) to the proximal end (rear) side of the base pipe 1a and pushing the base pipe 1a and the connecting pipe 1b connected to the base pipe 1a into the hole drilling rod 3 corresponds to the "first connection process" in the claims.

[0034] Next, an insertion operation (second insertion process) of inserting the wire rope 4 through the connecting pipe 1b (second connecting pipe) to be newly connected, and a connecting operation (second connection process) of connecting the connecting pipe 1b (second connecting pipe) to the connecting pipe 1b (first connecting pipe) already inserted into the hole drilling rod 3 and pushing the connecting pipe 1b (second connecting pipe) into the hole drilling rod 3 are performed. Thereafter, while repeating the same operation, the connecting pipes 1b are sequentially connected and pushed into the hole drilling rod 3. Note that the process of inserting the wire rope 4 through the (N + 1)-th connecting pipe 1b (the (N + 1)-th connecting pipe) to be newly connected into the N-th connecting pipe 1b (the N-th connecting pipe) already inserted into the hole drilling rod 3 is referred to as the "(N + 1)-th insertion process", and the process of connecting the (N + 1)-th connecting pipe 1b (the (N + 1)-th connecting pipe) to the N-th connecting pipe 1b (the N-th connecting pipe) and inserting it into the hole drilling rod 3 is referred to as the "(N + 1)-th connection process". Here, "N" is a natural number of 1 or more.

[0035] After the laying of the laying pipe 1 (base pipe 1a and connecting pipe 1b) of the set length into the hole drilling rod 3 is completed, the hole drilling rod 3 is removed. Note that the gap between the hole drilling rod 3 and the laying pipe 1 is filled with, for example, grout material.

[0036] After that, extend the laying pipe 1 to the ground surface part (Fig. 5). Specifically, while inserting the wire rope 4 into the laying pipe 1, extend the laying pipe 1 to the ground surface part and fill back the hole S provided in the ground G for the operation.

[0037] Next, a method of laying the sensor cable 2 in the laying pipe 1 (sensor cable laying process) will be described.

[0038] First, connect the end of the sensor cable 2 to one end of the wire rope 4. This process corresponds to the "cable connection process" in the claims.

[0039] Then, pull the other end of the wire rope 4 (see Fig. 6). Thereby, the sensor cable 2 is drawn into the laying pipe 1. When the sensor cable 2 is drawn into the laying pipe 1 for a predetermined length, the laying of the sensor cable 2 is completed. The process of drawing the sensor cable 2 into the laying pipe 1 corresponds to the "drawing-in process" in the claims.

[0040] The sensor cable 2 composed of an optical fiber or the like has weaker resistance to compressive load than to tensile load. For this reason, when the length of the sensor cable 2 becomes long, if the sensor cable 2 is pushed in and laid, the compressive load acting on the sensor cable 2 becomes large, and the sensor cable 2 may be damaged.

[0041] In contrast, in the laying method of this embodiment, by using the pulley 20 and pulling, it is laid in the laying pipe 1. Specifically, by connecting the end of the sensor cable 2 to one end of the wire rope 4 and pulling the other end of the wire rope 4, the sensor cable 2 is laid in the laying pipe 1. Thereby, when laying the sensor cable 2, it is possible to suppress the compressive load from acting on the sensor cable 2, so that it is possible to prevent the sensor cable 2 from being damaged due to the compressive load acting on it.

[0042] In the above-described embodiment, when laying the laying pipe 1, the case where the sensor cable 2 is pulled by the wire rope 4 inserted into the laying pipe 1 has been described, but it is not limited thereto. For example, a plurality of types of wire ropes 4 are prepared, and when laying the laying pipe 1, the thinnest wire rope 4a is inserted. Then, after laying the laying pipe 1, one end of a wire rope 4b having a higher strength than the wire rope 4a is tied to one end of the inserted wire rope 4a, and the other end of the wire rope 4a is pulled to replace it with the wire rope 4b (replacement step). Thereafter, the end of the sensor cable 2 is connected to one end of the wire rope 4b, and the other end of the wire rope 4b is pulled to lay the sensor cable 2 in the laying pipe 1. In this case, when laying the laying pipe 1, it is only necessary to insert the thin wire rope 4a into the connecting pipe 1b to be connected. Therefore, compared with the case of using a thick wire rope or a wire rope with high strength (less bending), the insertion work of the wire rope 4 can be facilitated, and the work efficiency can be improved.

[0043] Furthermore, in the above-described embodiment, the case where the wire rope 4 is a single wire rope has been described, but it is not limited thereto. For example, each time the connecting pipe 1b is connected, another wire rope 4 may be connected to the wire rope 4 to extend it (extension step). In this case, since the length of the wire rope 4 inserted into the connecting pipe 1b becomes shorter, compared with the case where a single wire rope 4 is inserted into the connecting pipe 1b, the insertion work of the wire rope 4 can be facilitated, and the work efficiency can be improved.

[0044] The embodiments of the present invention have been described above. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0045] In the above embodiment, the case where the sensor cable 2 is an optical fiber cable has been described. However, the sensor cable 2 is not limited to this, and any cable may be used as long as it can detect the state of the ground G. For example, it may be a linear body in which a plurality of sensors capable of detecting pressure and temperature are connected at equal intervals, or a metal wire such as a thermocouple. Further, the state of the ground G to be detected is not limited to the strain in the ground, and may be the temperature or pressure in the ground.

[0046] In the above embodiment, the case where the laying pipe 1 and the sensor cable 2 are laid in the ground G has been described as an example. However, the laying method of the above embodiment may be adopted, for example, when laying in a building or other structures.

Explanation of reference numerals

[0047] 1 ··· Laying pipe 1a ··· Base pipe 1b ··· Connecting pipe 2 ··· Sensor cable 3 ··· Drilling rod 3a ··· Base rod 3b ··· Connecting rod 3c ··· Bit 4 ··· Wire rope 20 ··· Pulley 21 ··· Cap member G ··· Ground H ··· Drilled hole

Claims

1. A sensor cable installation method including a pipe installation step of installing a pipe in a hole, and a sensor cable installation step of installing a sensor cable in the pipe, The pipe laying step includes: a pulley installation step of installing a pulley having a wire rope installed inside the base pipe; a base tube inserting step of inserting the base tube into the hole; a first insertion step of inserting the wire rope into a first connecting pipe connected to the base pipe; a first connecting step of connecting the first connecting pipe, through which the wire rope has been inserted in the first inserting step, to the base pipe and inserting the first connecting pipe into the hole, The sensor cable installation step includes: a cable connecting step of connecting the sensor cable to one end of the wire rope; a pulling step of pulling the other end of the wire rope to pull the sensor cable into the base pipe and lay it in the laying pipe.

2. A method for laying a sensor cable according to claim 1, comprising the steps of: The pipe laying step includes: a second insertion step of inserting the wire rope into a second connecting pipe; The sensor cable installation method further includes a second connecting step of connecting the second connecting pipe, through which the wire rope is passed, to the first connecting pipe inserted into the hole and inserting the second connecting pipe into the hole.

3. A method for laying a sensor cable according to claim 1 or 2, comprising the steps of: The sensor cable installation step includes: The sensor cable installation method further comprises a replacement step of connecting one end of the wire rope to a wire rope having strength greater than that of the wire rope, and pulling the other end of the wire rope to replace it with the stronger wire rope.

4. The method for laying a sensor cable according to claim 1, wherein: The laying pipe laying step is: When connecting the first connecting pipe, the method for laying a sensor cable further includes an extension step of connecting another wire rope to the wire rope for extension.

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