JPH09113472A - Wetness distribution measuring method and apparatus - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a wetness distribution measuring method and device capable of easily and inexpensively measuring wetness distribution in a longitudinal direction or a depth direction of a long soil such as an embankment. . SOLUTION: When an optical fiber 1 which is a sensor part of a temperature measuring device which is close to a wetness measurement target 3 is heated with a predetermined amount of heat for a predetermined time, a temperature change width of temperature information obtained by the optical fiber 1 is Depends on the wetness of the measurement target. Further, since the thermal time constant of the temperature change of the optical fiber 1 also differs depending on the wettability of the measurement target, the wettability distribution can be measured by measuring the temperature change of the heater 12 arranged along the measurement target 3. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wettability measuring method and an apparatus thereof, and more particularly to a wettability distribution measuring method and apparatus for measuring a wettability distribution in a longitudinal direction of a long measuring object such as a bank. .

[0002]

2. Description of the Related Art Conventionally, when measuring the wetness of a long measuring object such as an embankment, a humidity sensor is inserted into the soil and the wetness is measured from the output of the humidity sensor.

[0003]

However, in the above-mentioned conventional method, since the humidity at only one place can be measured, for example, when it is attempted to measure the wetness distribution in the longitudinal direction of the embankment, a large number of humidities are measured. The sensor had to be installed along the bank, which was not practical in terms of laying work and laying costs.

Therefore, an object of the present invention is to solve the above problems and to measure the wetness distribution of a long soil such as an embankment in the longitudinal direction or the depth direction easily and at low cost. It is to provide a distribution measuring method and apparatus.

[0005]

To achieve the above object, the present invention provides an optical fiber which is a sensor portion of an optical fiber temperature distribution measuring device, and a heater which is connected to a heat generation amount control circuit and heats the optical fiber. It is arranged along the measurement target, measures the temperature distribution in the longitudinal direction of the optical fiber, and measures the wetness distribution of the measurement target from the temperature change width and the thermal time constant of the temperature change.

In addition to the above-mentioned structure, the present invention heats / heats a heater.
The wetness distribution may be obtained by performing stop control and using one or both of the temperature change width and the thermal time constant of the temperature change.

In addition to the above structure, the present invention divides the heater into a plurality of parts, controls heating / stopping of only the selected heater, and measures the wetness distribution of the measurement target of the part heated by the heater. Good.

In addition to the above construction, in the present invention, at least a part of the optical fibers are arranged so as to be wound on a cylindrical surface having a diameter D in the circumferential direction at an axial pitch Lz, and at this part, the optical fibers are arranged along the axis of the cylinder. Wetness distribution may be obtained.

In the present invention, in addition to the above constitution, the object of wettability measurement may be soil.

Further, according to the present invention, an optical fiber arranged along the object to be measured, a heater arranged along the optical fiber for heating the optical fiber, and a heat generation amount control circuit connected to the heater for controlling the heat generation amount. An optical fiber temperature measuring device connected to the optical fiber for measuring the temperature distribution in the longitudinal direction of the optical fiber and measuring the wetness distribution of the measurement object from the temperature change width and the thermal time constant of the temperature change Is.

When an optical fiber, which is a sensor portion of a temperature measuring device close to an object to be measured for wetness, is heated with a predetermined amount of heat for a predetermined time, a temperature change width of temperature information obtained by the optical fiber is a wetness of the object to be measured. Depends on Further, since the thermal time constant of the temperature change of the optical fiber also differs depending on the wettability of the measurement object, the wettability distribution can be measured by measuring the temperature change of the heater arranged along the measurement object.

Further, when measuring the wettability distribution in the longitudinal direction or the depth direction of the object to be measured, an optical fiber temperature distribution measuring device for measuring the temperature distribution of the optical fiber may be used and the heater may be arranged along the optical fiber. That is, the heating / stopping of the heater along the optical fiber is controlled, the change over time of the temperature distribution along the optical fiber is measured, and the temperature change width and thermal time constant are determined for each position where the temperature distribution of the optical fiber is obtained. By determining either or both of the above, it is possible to determine the wettability distribution along the optical fiber.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

First, the principle of the wetness distribution measuring method of the present invention will be described.

FIG. 4 shows an experimental system for explaining the principle of the wetness distribution measuring method of the present invention.

The experimental system shown in the figure uses a linear heater to measure the temperature in the vicinity of the heater when the heater is heated / stopped for soils having different wettability, and the temperature change width This is to evaluate how the thermal time constant changes depending on the wetness.

The heater 992 has a depth of the soil 993 of about 20c.
A thermocouple 991 is embedded near the center of the heater 992. In addition, in order to simplify the explanation,
Wiring and measuring devices are omitted.

In this state, the heater 992 is energized and heated for about 1 hour, and the temperature of the thermocouple 991 is measured during heating of the heater 992 and up to 1 hour after the heating is stopped. After measurement,
This measurement is performed by changing the wetness of the soil.

FIG. 5 is a diagram showing the experimental results by the experimental system shown in FIG. 4, in which the horizontal axis represents time and the vertical axis represents temperature. FIG. 6 shows the measurement result of the temperature change width ΔT by heating for 1 hour in the experimental system shown in FIG. 4, and FIG. 7 shows the thermal time constant obtained from the change with time in the experimental system shown in FIG. Show. In FIG. 6, the horizontal axis represents the wettability and the vertical axis represents the temperature change width. In FIG. 7, the horizontal axis represents the wettability and the vertical axis represents the thermal time constant.

As shown in FIG. 6, the range of temperature change tends to decrease as the degree of wetness increases, so that the degree of wetness of soil can be obtained by knowing the range of temperature change at a predetermined time with a predetermined amount of heat generation. Further, the lower the degree of wetness, the greater the change in the temperature change width with respect to the degree of wetness of the soil. Therefore, when the degree of wetness is low, the degree of wetness can be obtained with high accuracy.

On the other hand, as shown in FIG. 7, the thermal time constant changes less as the wettability becomes lower, but in the high wettability region, the thermal time constant tends to increase as the wettability increases. Therefore, the wettability can be obtained with high accuracy from the thermal time constant in the high wettability region.

As described above, the temperature change width of the optical fiber when the optical fiber which is close to the wettability measurement object is heated with a predetermined amount of heat for a predetermined time varies depending on the wettability of the measurement object. Since the thermal time constant also varies depending on the wettability of the measurement target, it is understood that the wettability can be measured by measuring the temperature change of the heater embedded in the wettability measurement target.

Further, when measuring the distribution of the degree of wetness in the longitudinal direction or the depth direction of the object to be measured, an optical fiber temperature distribution measuring device for measuring the temperature distribution of the optical fiber may be used and the heater may be arranged along the optical fiber. I understand.

That is, the heating / stopping of the heaters arranged along the optical fiber is controlled, the change over time of the temperature distribution along the optical fiber is measured, and the temperature at each position where the temperature distribution of the optical fiber is obtained is measured. By obtaining either one or both of the change width and the thermal time constant, the wettability distribution along the optical fiber can be obtained.

The temperature change width ΔT shown in FIG. 6 is obtained by heating until the temperature rise during heating of the heater is almost saturated, and the thermal time constant τ shown in FIG. 7 is obtained from the change with time when the heater is stopped. It is a thing. The temperature at the time of heating the heater is expressed by equation (2).
Since the temperature when the heater is stopped is expressed by equation (3), if there is temperature distribution measurement data at different times t ₁ and t ₂ , the temperature change width ΔT and the thermal time constant τ should be calculated. You can

Therefore, it is not necessary to heat the heater until the temperature rise is saturated, and the measurement time can be shortened.

T (t) = T _0L + ΔT × (1-exp (−t / τ)) (2) T (t) = T _0H −ΔT × (1-exp (−t / τ)) ... (3) T (t): temperature at time t t: time (0 when heater heating starts or when heater stops) ΔT: temperature rise width τ: thermal time constant T _0L : before heater heating starts Temperature T _0H : Temperature before the heater is stopped Further, as a result of calculation by the following equation (4), if the heat generation amount is determined, the temperature Tr becomes larger as the degree of wetness becomes higher. ) Can also be used to determine the wetness.

Tr = (T (t ₂ ) −T (t ₁ )) / Log (t ₂ / t ₁ ) ... (4) FIG. 1 shows an apparatus to which the wetness distribution measuring method of the present invention is applied as an embankment. It is a perspective view showing one embodiment at the time of laying.

The sensor optical fiber cable 1 is laid in the bank 3 in the longitudinal direction, and one end (left side in the figure) of the sensor optical fiber cable 1 is connected to the wetness distribution measuring device 2. The installation position of the sensor optical fiber cable 1 is set to be lower than the water surface 4.

The optical fiber cable for sensor 1 has a structure as shown in FIG. 2, for example. FIG. 2 is a cross-sectional view of an optical fiber cable for sensor used in the device shown in FIG.

The optical fiber for sensor shown in FIG. 2 is an optical fiber core wire which is arranged via a tension member 13 made of steel wire or FRP and a spacer 14 having a circular cross section made of polyethylene or the like on the outer periphery of the tension member 13. 11 and heaters 12a and 12b, a water-blocking layer 15 made of aluminum foil laminated on the outer periphery of the spacer 14, and a water-blocking layer 15
And a sheath 16 made of vinyl or the like provided on the outer periphery of the.

The two heaters 12a and 12b are connected at the far end to form a loop-shaped energizing circuit. The wetness distribution measuring device 2 includes an optical fiber temperature distribution measuring device, a heater control circuit, a wetness distribution calculating unit that calculates a wetness distribution from measured temperature distribution data, and a control circuit that integrally controls the entire device. It is built in.

As the optical fiber temperature distribution measuring device, a device for measuring the temperature dependence of the Raman scattered light intensity generated in the optical fiber by the OTDR method is used.
It is possible to measure the wettability distribution of the measurement target over a length of several tens of kilometers.

FIG. 3 shows a measurement example of the wetness distribution measured by the wetness distribution measuring device shown in FIG. In FIG. 3, the horizontal axis represents the distance, the left vertical axis represents the temperature change width, and the right vertical axis represents the wetness. Further, the curve L ₁ shows the temperature change width, and the curve L ₂ shows the wettability.

In this example, the wetness distribution is obtained from the temperature change width when the heaters 12a and 12b are heated. From the figure, it can be seen that the wetness is high at point A.

In the above, since the wettability distribution can be obtained by measuring the temperature change width and the thermal time constant in the longitudinal direction of the optical fiber, the location where there is a risk of a bank breakage accident or the like due to the change in wettability. Can be discovered in advance, which is very effective for the management of embankments.

FIG. 9 is an external view of a cylindrical sensor used in the wetness distribution measuring apparatus of the present invention.

In the cylindrical sensor 7, the optical fiber cable for sensor 1 is wound around the outer circumference of a cylinder 74 and the outside is covered with a protective cover 76.

When the distance resolution of the optical fiber temperature distribution measuring device is insufficient to measure the wetness distribution, the sensor optical fiber cable 1 is provided with a cylinder 74 made of metal or plastic as shown in FIG. The cylindrical sensor 7 wound around the cylinder 74 may be produced and the wetness distribution in the axial direction of the cylinder 74 may be measured. If necessary, a protective cover 76 made of a metal material having good thermal conductivity may be covered to prevent external damage and waterproof of the optical fiber cable. When the winding diameter around the cylinder 74 is D, the winding pitch is Lz, and the distance resolution of the optical fiber temperature distribution measuring device is Lr, the cylinder 7
The distance resolution Lw of the measurement of the wetness distribution in the axial direction of 4 can be represented by the mathematical expression (1), and the wetness distribution can be measured with the resolution significantly higher than the distance resolution of the optical fiber temperature distribution measuring device. it can.

Lw = Lr × (Lz / √ (Lz ² + (π × D) ² )) (1) In FIG. 9, the optical fiber cable combined with the heater is wound around the cylinder, but shown in FIG. As described above, the heater 72 may be incorporated in the cylinder 74 without incorporating the heater in the optical fiber cable 71 to be wound. By doing so, the outer diameter of the cable to be wound can be reduced, so that the winding diameter and the winding pitch can be reduced, the outer diameter of the cylindrical sensor 7 can be reduced, and the distance resolution of the wetness distribution measurement can be improved. Can be made.
Further, since the cable of the lead portion that is exposed to the outside from the cylindrical sensor is not heated, there is no unnecessary heating and the heating power can be saved.

As an optical fiber cable 71, FIG.
When an optical fiber cable in which the optical fiber core wire is arranged in the central portion as shown in 1 is used, since the optical fiber is not twisted, the distance between the optical fiber used for temperature measurement and the heater and the wettability measurement target is set. It can be kept constant in the cable and the measurement accuracy can be improved. An optical fiber cable 71 shown in the figure has an optical fiber core wire 711 at the center and has a structure using a metal tube 713 for a sheath. By using a metal tube for the sheath, good heat conductivity and waterproofness can be provided.

In order to keep the accuracy of measuring the wetness distribution in the longitudinal direction of the optical fiber constant, it is desirable that the distance between the optical fiber used for temperature measurement, the heater and the object to be wetted is always constant. In a distance range shorter than the distance resolution Lr of the optical fiber temperature distribution measuring device, even if this condition is not satisfied, there is no problem because a measurement result averaged over the distance Lr is obtained, and if such a condition is satisfied There is no problem if the optical fiber is not placed in the center of the cable.

The cylindrical sensor is capable of measuring the wettability distribution in the depth direction with high distance resolution by vertically embedding it in a wettability measuring object such as an embankment. Also,
As shown in the external perspective view of FIG. 12, a plurality of cylindrical sensors 7 are installed at different locations on the embankment, and optical fibers between them are connected in series to obtain a wetness distribution in a plurality of locations in the depth direction. A single optical fiber cable 71 and a wetness distribution measuring device 2 connected to the optical fiber cable 71.
It can be measured with.

On the other hand, the heater lead wire 73 is adapted to supply power in the heater control section 94. However, if the heaters of all the cylindrical sensors are powered on at the same time, the power consumption increases, so It is controlled so that power is supplied only to the heater of the cylindrical sensor selected by the control signal sent from the humidity distribution measuring device 2 through the fiber cable 80. Optical fiber core wire 8 for temperature distribution measurement
1, control signal transmission optical fiber 83, power supply line 82
A and 82b can be combined into one by using the optical fiber cable 80 having the structure as shown in FIG.
Note that a metal communication line may be used instead of an optical fiber for the heater control signal transmission line. Note that FIG. 13 is similar to FIG.
3 is a cross-sectional view of a cable used in the device shown in FIG.

The above-described embodiment is an example in which a plurality of cylindrical sensors are used to reduce power consumption. However, by adopting the configuration shown in FIG. 14, the wetness distribution in the longitudinal direction is obtained. Power consumption can also be reduced by measurement. Here, an optical fiber cable for a sensor 10 that is a composite of an optical fiber core wire 11 having a cross-sectional structure as shown in FIG.
0, and a power supply / control composite cable 90 and a heater control unit 94 having a sectional structure as shown in FIG. 16 is a cross-sectional view of another embodiment of the optical fiber cable used in the apparatus shown in FIG. 15, and FIG.
FIG. 6 is a cross-sectional view of another embodiment of the optical fiber cable used in the device shown in FIG.

In FIG. 16, only one heater is combined, but both ends are connected to the power supply line 92 according to a control signal in the heater control section 94 so that electricity can be generated to generate heat. In addition, 93 is an optical fiber core wire,
95 is a switch S _A (n), S _A (n + 1), S
It is a heater switching device that switches the heater to generate heat by controlling ON / OFF of (n) and S (n + 1).

The operation of the apparatus shown in FIG. 14 will be described with reference to FIG.

For example, the sensor optical fiber cable 10
When the C (n) portion of 0 is energized to measure the wetness distribution, the switch S _B (n) and the switch S _A (n + 1) are connected for a predetermined time and the heater is energized for a predetermined time. C (n) of the sensor optical fiber cable 100 of the embankment 3 based on the temperature change width of the temperature information obtained at this time and the thermal time constant.
Wetness distribution in the part can be measured. Similarly, when measuring the wetness distribution in the C (n + 1) part of the sensor optical fiber cable 100, by switching the heater switch, only the C (n + 1) part of the sensor optical fiber cable 100 is energized for a predetermined time, The wetness distribution in the C (n + 1) portion of the sensor optical fiber cable 100 of the bank 3 can be measured by the temperature change width of the obtained temperature information and the thermal time constant.

As described above, the heater switch 95 causes the switches S _A (n), S _A (n + 1), S (n), and S (n +).
By switching 1), only the required heaters can be energized as compared with the case where all the heaters are energized, so that the power consumption can be reduced.

The cylindrical sensor is not uniformly wound on the entire length in the axial direction of the cylinder, but is densely wound only on the portions (W _A , W _B , ..., W _Z ) whose wetness is to be measured as shown in FIG. The other portion may be wound only for connecting the optical fiber cable. By doing so, the length of the optical fiber used can be shortened. When a cylindrical sensor having a structure in which the heater 72 is built in the cylinder 74 as shown in FIG. 9 is used, the heater 72 is built only in the portion where the optical fiber 71 for measuring the degree of wetness is tightly wound, so that unnecessary heat is generated. It is also possible to save power consumption by not performing. Further, in the optical fiber temperature distribution measuring device, generally, the measurement accuracy decreases as the length of the optical fiber to be measured becomes longer, and therefore it is necessary to lengthen the measurement time in order to ensure the measurement accuracy. Therefore, with such a configuration, it is possible to measure the wettability of a required measurement point with high accuracy without extending the measurement time.

By applying the wetness distribution measuring method and apparatus of the present invention to the soil wetness measurement of a bank such as a river, it is possible to easily and surely find a dangerous point of the bank.

The method and apparatus for measuring the degree of wetness distribution of the present invention is not limited to the measurement of the degree of wetness distribution of soil, but can be applied to the measurement of humidity in the air.

[0053]

In summary, according to the present invention, the following excellent effects are exhibited.

The wettability distribution in the longitudinal direction and the depth direction of the object to be measured can be measured easily and at low cost, and the dike safety can be reliably controlled.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment in which a device to which the wetness distribution measuring method of the present invention is applied is laid on a bank.

FIG. 2 is a cross-sectional view of an optical fiber cable for sensor used in the device shown in FIG.

FIG. 3 is a measurement example of a wetness distribution measured by the wetness distribution measuring device shown in FIG.

FIG. 4 is an experimental system for explaining the principle of the wetness distribution measuring method of the present invention.

5 is a diagram showing an experimental result by the experimental system shown in FIG.

6 is a diagram showing a measurement result of a temperature change width ΔT by heating for 1 hour in the experimental system shown in FIG.

FIG. 7 is a diagram showing a thermal time constant obtained from a change with time when the temperature is lowered in the experimental system shown in FIG.

8 is a diagram showing the relationship between the wettability and the temperature change data according to the experimental system shown in FIG.

FIG. 9 is an external view of an embodiment of a cylindrical sensor used in the wetness distribution measuring apparatus of the present invention.

FIG. 10 is an external view of another embodiment of the cylindrical sensor used in the wetness distribution measuring apparatus of the present invention.

11 is a cross-sectional view of an optical fiber cable used in the cylindrical sensor shown in FIG.

FIG. 12 is a perspective view showing another embodiment in which a device to which the wetness distribution measuring method of the present invention is applied is laid on a bank.

13 is a cross-sectional view of a cable used in the device shown in FIG.

FIG. 14 is a perspective view showing still another embodiment in which a device to which the wetness distribution measuring method of the present invention is applied is laid on a bank.

FIG. 15 is an explanatory diagram for explaining the operation of the apparatus shown in FIG.

16 is a cross-sectional view of another embodiment of the optical fiber cable used in the device shown in FIG.

FIG. 17 is a cross-sectional view of another embodiment of the optical fiber cable used in the device shown in FIG.

FIG. 18 is a cross-sectional view of another embodiment of the cylindrical sensor shown in FIG.

[Explanation of symbols]

 1 Optical fiber cable for sensor (optical fiber) 2 Wetness distribution measuring device 3 Measurement target (bank) 4 Water surface

Claims (6)

[Claims] 1. An optical fiber which is a sensor part of an optical fiber temperature distribution measuring device, and a heater which is connected to a heat generation amount control circuit and heats the optical fiber are arranged along a measuring object, and a longitudinal direction of the optical fiber. A method for measuring a wetness distribution, which comprises measuring the temperature distribution and measuring the wetness distribution of a measurement target from the temperature change width and the thermal time constant of the temperature change. 2. The method for measuring a wetness distribution according to claim 1, wherein the heater is controlled to be heated / stopped, and the wetness distribution is obtained by using one or both of a temperature change width and a thermal time constant of the temperature change. . 3. The heater according to claim 1, wherein the heater is divided into a plurality of parts, and only the selected heater is heated / stopped to measure the wetness distribution of the object to be measured in the part heated by the heater. Wetness distribution measurement method. 4. At least a part of the optical fibers is arranged so as to be wound on a cylindrical surface having a diameter D in a circumferential direction at an axial pitch Lz, and a wettability distribution along the axis of the cylinder is obtained at this part. Item 5. The wetness distribution measuring method according to any one of Items 1 to 3. 5. The method for measuring the wetness distribution according to claim 1, wherein the object to be measured for the wetness is soil. 6. An optical fiber arranged along a measurement target, a heater arranged along the optical fiber for heating the optical fiber, and a heat generation amount control circuit connected to the heater for controlling heat generation amount, An optical fiber temperature measuring device connected to the optical fiber for measuring the temperature distribution in the longitudinal direction of the optical fiber, and measuring the wetness distribution of the measurement object from the temperature change width and the thermal time constant of the temperature change. A wetness distribution measuring device characterized by: