JP2002070015A - Net body for civil engineering work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a net body for a civil engineering work reinforcing a banking or the like while being able to predict the danger of the collapse of the banking or the like. SOLUTION: In the net body N in which the warps 1 and the weft 2 made of a synthetic resin are crossed alternately and each intersection section is fixed, the net body N for civil engineering works are constituted by installing an optical fiber sensor 5 to at least one warp 1a. Pulse light is projected to the optical fiber sensor 5 for the net body N for engineering works buried into the banking or the like for reinforcement, the back scattered light of brilliant scattered light is detected, and the danger of the collapse of the banking or the like can be predicted when the distortion distribution and distortion quantity of the sensor 5 are measured from the frequency shift distribution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a civil engineering net which is buried to reinforce an embankment or the like, and more particularly to a civil engineering net which can predict a collapse of an embankment or the like and take preventive measures. .

[0002]

2. Description of the Related Art Hitherto, a high-strength civil engineering net has been buried in soil in order to reinforce an embankment or a laid ground to prevent collapse. As such a reinforcing net, a net having a large tensile strength, in which warp yarns and weft yarns made of synthetic resin are crossed to each other and fixed at intersections, and which are not easily collapsed is preferably used.

[0003]

However, when the state of the embankment or the like changes due to rainfall or the like, or when a force larger than expected is applied to the civil engineering net or the civil engineering net deteriorates, the embankment is filled. Are in an unstable state, and there is a risk of collapse.

[0004] Even in the case where the danger of collapse occurs, there has been no means for predicting the collapse of the embankment or the like, so that preventive measures cannot be taken immediately, and unfortunately, landslides may occur. In many cases, evacuation was delayed.

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned problems. It is an object of the present invention not only to reinforce an embankment or the like, but also to prevent the collapse of the embankment or the like and take preventive measures. The object is to provide a net.

[0006]

According to a first aspect of the present invention, there is provided a mesh net for civil engineering in which a warp and a weft made of synthetic resin are crossed with each other and their intersections are fixed. A body, characterized in that at least one warp is provided with an optical fiber sensor.

When such a civil engineering net is buried in an embankment or the like such that one end of a warp is exposed on a slope, the embankment or the like is reinforced by the civil engineering net, preventing side slip and sinking of the soil. The risk of collapse of the embankment or the like can be predicted by the optical fiber sensor. In other words, when the state of the embankment changes and the danger of collapse occurs, a large tensile stress is partially generated in the warp and the weft of the civil engineering net, and an elongation strain is generated. Distortion will occur. When stretching distortion occurs in the optical fiber sensor in this way, the frequency shift of the back Brillouin scattered light of the optical fiber sensor increases depending on the magnitude of the stretching distortion. Therefore, pulse light is incident from the exposed end of the optical fiber sensor, the backscattered light of Brillouin scattered light generated in the optical fiber sensor is detected, and the strain distribution and amount of strain of the optical fiber sensor are measured from the frequency shift distribution, and collapse is performed. You can foresee the danger of this. In addition, when the optical fiber sensor undergoes elongation distortion, the light intensity of the Rayleigh scattered light changes accordingly.Therefore, the amount of strain of the optical fiber sensor is measured from the light intensity of the Rayleigh scattered light to predict the risk of collapse. You can also.

Next, a net for civil engineering according to a second aspect of the present invention is the net of the first aspect, wherein the warp and the weft are around the core tape made of a uniaxially stretched olefin-based resin or both upper and lower sides. Is coated with a thermoplastic resin coating film, wherein the optical fiber sensor is provided inside at least one warp coating film.

Such a civil engineering net has a large tensile strength because the warp and weft core tapes are uniaxially drawn olefin resin tapes, and the coating film of the warp and weft is made of a thermoplastic resin. In the film, the intersections are firmly welded by various heating means, so that no collapse occurs. Since the optical fiber sensor is provided inside the thermoplastic resin coating film, the optical fiber sensor is protected by the coating film, and there is no fear of being damaged or cut.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view of a civil engineering net according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a warp and a weft of the net, and FIG. 3 is a warp provided with an optical fiber sensor of the net. FIG. 4 is an enlarged sectional view of a warp of another embodiment provided with an optical fiber sensor, and FIG. 5 is an explanatory view of one example of use of a civil engineering net.

In this civil engineering net N, the warp yarns 1 and the weft yarns 2 intersect at right angles at a predetermined interval so as to form a vertically long rectangular mesh, and the warp yarns 1 at the intersections like plain weave.
And the weft 2 are alternately reversed in the vertical direction and overlapped with each other, and the respective intersections are heat-welded. Even if the warp 1 and the weft 2 do not alternately reverse the vertical relationship at the intersection as described above, the warp 1 and the weft 2 may be overlapped and heat-sealed so that the warp 1 is located above or below the weft 2 at all the intersections. Good.

As shown in FIG. 2, the warp yarns 1 and the weft yarns 2 constituting the civil engineering net N are covered with a thermoplastic resin coating film 4 around a core tape 3 made of a uniaxially stretched olefin resin. It is made of a coated tape.

As a preferred core tape 3, polypropylene or ultra-high-molecular-weight polyethylene is melt-extruded into a belt shape.
This is monoaxially stretched 5 to 20 times (preferably 7 to 10 times) in a temperature range of 90 to 140 degrees, and has a thickness of 0.2 to 0.2.
A stretched tape having a width of 1.0 mm and a width of 5 to 20 mm is used. A core tape having a draw ratio of less than 5 times has insufficient tensile strength due to insufficient molecular orientation by stretching, while a core tape having a draw ratio of more than 20 times has a large decrease in strength due to fibrillation. Are not preferred. In addition, even when the stretching ratio is 5 to 20 times, a core tape having a thickness of less than 0.2 mm and a width of less than 5 mm tends to have an insufficient absolute strength, and a thickness of more than 1 mm and A core tape having a width larger than 20 mm is not preferable because it has high rigidity and the winding property and the handling property tend to decrease.

The coating film 4 for covering the core tape 3 can be formed by using various conventionally known thermoplastic resins. Among them, a coating film formed of a vinyl chloride resin having a high dielectric constant or an ethylene-vinyl acetate copolymer resin is used. The coated film 4 is particularly suitable.
This is because such a coating film 4 has good high-frequency welding properties, and thus can be subjected to high-frequency welding under mild conditions without damaging the core tape 3 to firmly fix the intersection of the warp 1 and the weft 2. The coating film 4 is made of a thermoplastic resin having a low dielectric constant.
Is formed, the intersection of the warp 1 and the weft 2 may be thermally welded by ultrasonic welding or other heating means.

The thickness of the coating film 4 is 0.1 mm or more, preferably about 0.5 to 0.8 mm. When the thickness is smaller than 0.1 mm, the welding strength at the intersection of the warp 1 and the weft 2 is reduced. Because of the shortage, when a large hooking force is applied to the net N, the intersections are peeled off and the collapse is likely to occur. Also, it is preferable to form uneven wrinkles 4a on the surface of the coating film 4 to prevent longitudinal tearing of the tape and to improve the weldability.

The major feature of the civil engineering net N is that an optical fiber sensor 5 is provided over the entire length of at least one (two in FIG. 1) warp 1a. As shown in FIG. 3, the warp yarn 1a provided with the optical fiber sensor 5 has a structure in which the optical fiber sensor 5 is attached to the side of the core tape 3 and the periphery is covered with a coating film 4 of a thermoplastic resin. , An optical fiber sensor 5 is incorporated inside the coating film 4. The way of incorporating the optical fiber sensor 5 is not limited to the above. For example, the core tape 3 is vertically divided into two parts like the warp thread 1a shown in FIG. The periphery may be covered with the coating film 4.

The optical fiber sensor 5 includes a warp 1
May be provided outside the thermoplastic resin coating film 4, but if provided inside the coating film 4 as described above, the optical fiber sensor 5 is protected by the coating film 4 and is damaged or cut. It is preferable because there is no worry about it.

Warp 1 incorporating optical fiber sensor 5
a is sufficient if at least one is in the net N, but is preferably 1
It is desirable to provide a plurality of these at intervals of about 3 m (preferably about 2 m). Thus, the warp 1a is
When a plurality of civil engineering nets N are buried in an embankment or the like at intervals of about m, changes in the state of the embankment or the like can be finely investigated at an interval of 1 to 3 m, so that the accuracy is improved.

The thickness of the optical fiber sensor 5 is not particularly limited, but a diameter of about 0.5 to 2 mm is preferably used.

In the civil engineering net N constructed as described above, a connector 6 for connecting a measuring instrument is attached to one end of a warp 1a provided with an optical fiber sensor. For example, as shown in FIG. It is used by being buried in the upper and lower several layers inside the embankment 7 while being exposed on the surface 7a. When the netting N for civil engineering is buried in this way, the embankment 7 is reinforced and the embankment 7 is reinforced.
Side slip and settlement are suppressed.

When the state of the embankment 7 changes due to heavy rain or the like and the risk of collapse increases, as described above, the civil engineering net N and the optical fiber sensor 5 are stretched and strained. Then, the measuring device 8 is connected to the connector 7 and pulsed light is incident from one end of the optical fiber sensor, backscattered light of Brillouin scattered light generated in the optical fiber sensor is detected, and the strain distribution of the optical fiber sensor is determined from the frequency shift distribution. And the amount of strain, the change in the state of the embankment 7 can be accurately grasped, and the collapse can be sufficiently predicted.

While the civil engineering net of the present invention has been described with reference to the typical embodiment, the present invention is not limited to this embodiment only. The covering tape coated with the covering film 4 of the thermoplastic resin constitutes a mesh body as the warp 1 and the weft 2, or the covering tape in which two or more core tapes 3 are overlapped and the periphery thereof is covered with the covering film 4 is a warp. 1 and weft 2 constitute a net,
Various changes can be tolerated.

[0024]

The civil engineering net of the present invention not only reinforces the embankment and the like, but also has a remarkable effect that it can grasp the change in the state of the soil and predict the danger of collapse. It is possible to take measures and safely evacuate.

[Brief description of the drawings]

FIG. 1 is a plan view of a civil engineering net according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a warp and a weft of the same net.

FIG. 3 is an enlarged sectional view of a warp provided with the optical fiber sensor of the same net.

FIG. 4 is an enlarged sectional view of a warp of another embodiment provided with an optical fiber sensor.

FIG. 5 is an explanatory diagram of one usage example of a civil engineering net.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Warp 1a Warp provided with optical fiber sensor 2 Weft 3 Core tape 4 Coating film 4a Uneven wrinkle 5 Optical fiber sensor 6 Connector 7 Embankment 7a Slope 8 Measuring instrument

Continuation of front page (72) Inventor Shinzo Matsuyama 2-3-13 Azuchicho, Chuo-ku, Osaka-shi F-term in Takiron Co., Ltd. 2D044 CA04 2F065 AA65 CC00 FF00 LL03

Claims (2)

[Claims] 1. A mesh body in which a warp and a weft made of synthetic resin cross each other and their intersections are fixed, wherein at least one warp is provided with an optical fiber sensor. Net. 2. A warp and a weft are coated tapes in which a core tape made of a uniaxially stretched olefin resin is coated on the periphery or both upper and lower surfaces with a coating film of a thermoplastic resin, and the optical fiber sensor has at least one warp. The civil engineering net according to claim 1, wherein the net is provided inside the coating film.