JPH09329469A - Slope abnormality observing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slope abnormality observing system secured with good economy, which can sense any abnormal phenomenon at the stage of forerunning, such as landslide, rock fall, likely at a mountain flank or the side slope of a road. SOLUTION: Strain gauges 4 including optical fiber 4a accommodated in metal pipe are laid on a guard net 1 stretched over a slope of a place of ovservation, and thereby an abnormality observation sensor part 3 is formed. The optical fibers 4a of these sensors 4 are tied together in series and connected with a strain sensing device 7 in a monitor center through a signal transmitting optical fiber 8. An elongative strain is generated in optical fiber(s) owing to dislocation of a rock or the like in the netting 1. The generated strain is sensed through utilization of the trait that the generation frequency of Brillouin dispersion light shifts with change in the elongative strain, and thereby abnormality can be known at the stage of forerunning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention predicts anomalous phenomena such as landslides on a mountain slope cut for road construction and rockfall from an upper slope along a road. The present invention relates to a strain anomaly observation system for observing a strain and a strain sensor having improved suitability as a sensor for the system.

[0002]

2. Description of the Related Art Conventionally, when detecting a landslide on a slope or a rock fall from a slope, a point type sensor, a detection linear sensor of a type that detects it after an abnormality occurs, or a monitoring camera is used. Was used.

[0003]

Conventionally used detection line type sensors and surveillance cameras are used for driving transducers and data transmission devices and other devices at observation points (sites) in order to collect observation information. Since it is necessary to specially provide a power source and a transmission line, the construction cost of the monitoring system increases. Moreover, there is a problem that system maintenance and management are difficult.

Further, the detection linear sensor and the surveillance camera are not suitable for predicting an abnormality because they cannot be detected until an abnormality has occurred.

Further, the point type sensor is not suitable for wide area observation. Landslides and rockfalls cannot be detected reliably with a point-type sensor because it is not known at which position on the slope.

If the number of sensors is increased in order to compensate for the drawback and a method of distributing the sensors at a high density at the observation site is adopted, the cost for constructing the system increases and the effort for constructing the system increases, which is not practical.

The present invention is a slope abnormality observing system that solves both the problems when using a detection line type sensor or a surveillance camera and the problems when using a point type sensor,
It is an object to provide a strain sensor suitable for use in this system.

[0008]

In order to solve the above problems, in the present invention, a slope anomaly observation system has a strain sensor having an optical fiber as a detector, and the strain sensor is installed on the slope of an observation site. Anomaly observation sensor section that can be stretched, the strain detection device that detects the magnitude of the strain generated in the optical fiber of the strain sensor by utilizing the characteristic that the generation frequency of the Brillouin scattered light moves due to the variation of the stretch strain, The optical fiber for signal transmission connects the above-mentioned abnormality observation sensor unit and the strain detection device.

It is preferable that the abnormality observing sensor section has a plurality of strain sensors distributed evenly on the protective net and the optical fibers of the strain sensors are connected in series. In addition, the strain sensor used here is an optical fiber with a metal tube that is made by integrating a metal tube and an optical fiber passing through the metal tube with a filling material packed in the metal tube. Further, it is preferable that a reinforcing wire is added to the outside of the double-folded fiber, and the reinforcing wire and the double-folded fiber are integrally covered with a flexible molding material.

[0010]

In the slope anomaly observation system of the present invention, light is sent from the strain detection position to the optical fiber of the strain sensor via the optical fiber for signal transmission. If the slope position is displaced, the strain sensor is stretched by receiving lateral pressure, and the expansion causes the generation frequency of Brillouin scattered light generated at the position of the optical fiber of the sensor to move. Therefore, by observing this frequency shift, the magnitude of elongation strain generated in the optical fiber of the strain sensor is obtained, and from the magnitude of the elongation strain, anomalies that have occurred on the observation slope and precursor phenomena of anomalies (landslides within the protective net and Rock misalignment) is detected. Therefore, a power source and a data transmission device are not required on the site, the system can be simplified, and the maintenance is easy.

Further, when the strain sensor is laid on the protective net stretched on the slope, the displacement of the slope at the position where the sensor is not present is also transmitted to the strain sensor through the protective net. Therefore, even if the number of sensors is not extremely increased, surface monitoring can be performed and reliability can be improved.

The strain sensor may be directly attached to the slope without the net. Also in this case, by installing several long strain sensors at appropriate intervals so that they cross the slope,
Since it is possible to cover almost the entire slope on average with a small number of sensors, it is advantageous in terms of reliability and economy as compared with the case of using a point type sensor.

A strain sensor having a structure in which an optical fiber containing a metal tube is folded in two, a reinforcing wire is added thereto, and these are covered and integrated with a molding material, has a wide pressure receiving surface area and is suitable for detecting surface displacement. . Further, since the optical fiber length is doubled, the detection sensitivity is also excellent. Furthermore, since it contains a reinforcing wire, it has high strength and is particularly suitable for abnormal observation of slopes that are expected to be subjected to strong lateral pressure. In addition,
This strain sensor can also be effectively used for detecting surface displacements other than slopes.

[0014]

FIG. 1 shows an embodiment of the slope anomaly observation system of the present invention. This figure is a conceptual diagram of the entire system.

Reference numeral 1 in FIG. 1 is a protective net stretched on the observation slope to prevent rockfall, and 2 is a net fixing portion. On this net 1, a plurality of strain sensors 4 are laid in parallel at predetermined intervals to form an abnormality observation sensor unit 3.

Each strain sensor 4 is closely attached to the protective net 1 and both ends thereof are fixed to the fixture 5. This strain sensor 4
Includes a metal tube-containing optical fiber 4a acting as a detector, and the metal tube-containing optical fiber 4a of each strain sensor.
Are connected in series via the fusion-bonding part 6, and observation areas A to G are created.

Reference numeral 7 denotes a strain detecting device for detecting the magnitude of the elongation strain generated in the optical fiber by utilizing the characteristic that the generation frequency of the Brillouin scattered light moves due to the variation of the elongation strain. , And a display device 7b.

Reference numeral 8 is an optical fiber for signal transmission that connects between the anomaly observation sensor unit 3 provided on the slope of the observation site and the strain detection device 7 provided at a remote monitoring center.

The strain sensor 4 has a structure as shown in FIGS. That is, as shown in the figure, the optical fiber 4a containing a metal tube (for example, a stainless tube) is attached to the fixture 5 on one side.
It is turned along the sheave 4b supported by and is folded in two to fix the ends near both ends to the fixture 5 on the other side. In addition, one piece (two pieces in total) of reinforcing steel strands 4c is added to the outer side of the bifold fiber, and these are covered and integrated with a rubber molding material 4d. In the strain sensor 4 shown in the figure, only the optical fiber 4a containing the metal tube folded in two is first molded with rubber, then the steel strand 4c is attached, and the outer side is covered with a laminated rubber sheet. It may be constructed.

The observation system of FIG. 1 configured as described above sends light from the monitoring center to the abnormality observation sensor section 3 via the optical fiber 8 to constantly monitor the degree of strain of each strain sensor 4. When the earth and sand and rocks inside the protective net 1 are displaced, the net is pushed and the strain sensor 4 (optical fiber 4
Elongation strain is added to a), and the magnitude of the strain is displayed on the display device 7b as a waveform as shown in FIG. 4, for example. In this example, distortion occurs in each region of the observation regions A to G except B in FIG. This strain is initially zero, and gradually increases, so it is possible to predict in advance an abnormal phenomenon such as a rock fall from the change in strain magnitude over time.

[0021]

As described above, according to the present invention,
Since the precursor of the abnormal phenomenon on the slope can be detected using the optical fiber, it is not necessary to install an information transmission device or power source at the observation point, and it is possible to construct an economical slope maintenance system that is easy to maintain. Become.

In the future, many optical fiber cables will be laid on roads as an information communication network. By using this optical fiber cable as a transmission path for measurement signals and installing anomaly observation sensor parts at required points, and collecting the information from that part to a monitoring center for observation, it is possible to realize a very economical multipoint observation monitoring system. It is useful for road disaster prevention and accident prevention due to abnormal slope phenomenon.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an embodiment of a slope anomaly observation system of the present invention.

FIG. 2 is a sectional plan view of a strain sensor using an optical fiber.

FIG. 3 is a longitudinal cross-sectional view of the strain sensor of FIG.

FIG. 4 is a diagram showing an example of detected distortion by the system of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protective net 2 Net fixing part 3 Abnormality observation sensor part 4 Strain sensor 4a Optical fiber with metal tube 4b Sheave 4c Reinforcing steel strand 4d Rubber molding material 5 Fixing part 6 Fusing part 7 Strain detecting device 7a Processing device 7b Display device 8 Optical fiber for signal transmission A to G observation area

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Daigo Sato 1-3-12 Moto-Akasaka, Minato-ku, Tokyo Sumitomo Electric Industries, Ltd. Tokyo headquarters (72) Inventor Yuji Nakura 1-chome, Shimaya, Konohana-ku, Osaka No. 1-3 Sumitomo Electric Industries, Ltd. Osaka Works

Claims (3)

[Claims] 1. An abnormality observation sensor section having a strain sensor having an optical fiber as a detector, the strain sensor being stretched around a slope of an observation site, and the magnitude of strain generated in the optical fiber of the strain sensor. A slope composed of a strain detecting device for detecting the occurrence frequency of the Brillouin scattered light by the variation of the elongation strain and a signal transmission optical fiber connecting the abnormality detecting sensor part and the strain detecting device. Anomaly observation system. 2. The slope anomaly observation system according to claim 1, wherein the strain sensor is installed on a protective net stretched over the slope of the observation site to constitute the anomaly observation sensor unit. 3. An optical fiber with a metal tube, in which a metal tube and an optical fiber passed through the metal tube are integrated by a filling material packed in the metal tube, is turned along a sheave on one side to be a double-folded fiber, and further, A strain sensor in which a reinforcing wire is added to the outside of the double-folded fiber, and the reinforcing wire and the double-folded fiber are integrally covered with a flexible molding material.