JP6793108B2 - Corrosion amount estimation device and its method - Google Patents

Description

The present invention relates to a corrosion amount estimation device for calculating the corrosion amount of a steel material buried underground and a method thereof.

Most of the infrastructure facilities were intensively constructed during the period of high economic miracle, so they will all deteriorate in the future. On the other hand, the cost for maintenance of equipment and the number of personnel involved in maintenance tend to decrease. Therefore, in the future, it will not be possible to properly maintain and manage infrastructure equipment, and it may be difficult to ensure safety and security. In order to deal with the problem of aging infrastructure equipment, in recent years, attempts have been made to predict the deterioration of the equipment and formulate an efficient maintenance plan based on the result.

There is a statistical method as a method of predicting the deterioration of infrastructure equipment. The statistical method is a method of observing and analyzing a sample that has deteriorated due to exposure to various natural environments, and deriving a prediction formula by performing statistical analysis such as regression analysis and extreme value statistics based on the data.

There is also a method of experimentally obtaining a prediction formula. An idea of burying a metal in an environment simulating the target soil and measuring the corrosion of a steel material in the soil by using an electrochemical method has been proposed (for example, Non-Patent Document 1).

Yoshikazu Miyata and one other person, "Soil Corrosion Measurement Focusing on Electrochemical Methods (Part 2)", Materials and Environment, 46, 610-619, 1997.

However, the conventional statistical method has a problem that it is difficult to collect the information necessary for statistical analysis in the first place, or it is necessary to spend a great deal of cost and time. In addition, it takes a long period of time to experimentally measure the corrosion of steel materials in soil and obtain the corrosion rate function that expresses the corrosion rate. That is, there is a problem that the method of experimentally determining the amount of corrosion also requires cost and time.

The present invention has been made in view of this problem. The time-dependent change function of the corrosion rate, which changes with time as the water content of the soil changes, is obtained, and the change function and the rainfall data are used to obtain the time-dependent change function of the steel material in the soil. It is an object of the present invention to provide a corrosion amount estimation device and a method thereof, which can easily predict the corrosion amount in a short period of time.

The corrosion amount estimation device according to one aspect of the present embodiment supplies water to the soil in which the steel material to be evaluated is buried, and the corrosion rate of the steel material with respect to the elapsed time until the water content of the soil is saturated, and the water content of the soil. The elapsed time and the corrosion rate of the steel material when the saturated state is continued, and the elapsed time after the water supply is stopped from the saturated state of the soil and the corrosion rate of the steel material are shown. From a corrosion rate measuring unit that measures multiple times, a change function calculation unit that calculates a plurality of change functions that represent each corrosion rate with respect to the elapsed time, and a plurality of rainfall data that represent the time when the amount of rainfall exceeds a predetermined value. The amount of corrosion of the steel material is calculated using the data extraction unit that extracts a plurality of rainfall interval data consisting of a combination of the rainfall time and the rainfall interval representing the interval until the next rainfall, and the rainfall interval data and the change function. The gist is to provide a corrosion amount calculation unit.

The corrosion amount estimation method according to one aspect of the present embodiment is the corrosion amount estimation method executed by the above-mentioned corrosion amount estimation device, in which water is supplied to the soil in which the steel material to be evaluated is buried, and the water content of the soil is saturated. The water supply is stopped from the state where the corrosion rate of the steel material with respect to the elapsed time, the elapsed time when the water content of the soil is saturated, the corrosion rate of the steel material, and the water content of the soil are saturated. The elapsed time after the above and the corrosion rate of the steel material are measured multiple times, and a plurality of change functions representing the respective corrosion rates with respect to the elapsed time are calculated, and the time when the amount of rainfall exceeds a predetermined value is calculated. From the plurality of rainfall data represented, a plurality of rainfall interval data consisting of a combination of the rainfall time and the rainfall interval representing the interval until the next rainfall is extracted, and the corrosion of the steel material is used by using the rainfall interval data and the change function. The gist is to calculate the quantity.

According to the present invention, since the amount of corrosion is calculated from the change function representing the change in the corrosion rate with respect to the water content of the soil and the rainfall data, the amount of corrosion of the metal in the soil can be predicted easily and in a short period of time.

It is a figure which shows the functional structure example of the corrosion amount estimation apparatus which concerns on embodiment of this invention. It is a figure which shows the operation flow of the corrosion amount estimation apparatus shown in FIG. It is a figure which shows typically the Nyquist diagram measured by the corrosion rate measuring part of the corrosion amount estimation apparatus shown in FIG. It is a figure which shows typically the relationship between the water content (moisture content) in soil, and precipitation. It is an equivalent circuit representing the impedance in soil, (a) is an equivalent circuit in the case of measuring with three electrodes, and (b) is an equivalent circuit in the case of measuring with two electrodes. It is a figure which shows typically the change of the corrosion rate of the steel material in the soil in the process of supplying water until the water content of the soil is saturated, and then draining the water. It is a figure which shows typically the example which approximated the change of the corrosion rate shown in FIG. It is a figure which shows typically another example which approximated the change of the corrosion rate shown in FIG. It is a figure which shows the change of the corrosion rate in the case of water supply (rainfall) and drainage (non-rainy weather) schematically, (a) is when water supply is completed in one day, (b) is water supply for two days. When continuing, (c) indicates a case where drainage continues for one day, and (d) indicates a case where drainage continues for two days. It is a figure which shows the example of the rainfall data. It is a figure which shows the relationship example of the daily rainfall amount and the corrosion amount. It is a figure which shows typically the corrosion amount estimated by the corrosion estimation apparatus which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same objects in a plurality of drawings, and the description is not repeated.

FIG. 1 is a diagram showing a functional configuration example of the corrosion amount estimation device according to the embodiment of the present invention. The corrosion amount estimation device 1 shown in FIG. 1 is a device that estimates the corrosion amount of a steel material in soil easily and in a short period of time.

FIG. 1 also shows the containment section 2, the soil 3, and the sensor 4. The sensor 4 contains a steel material to be evaluated and is buried in the soil 3 housed in the storage part 2. The steel material to be evaluated (hereinafter, the steel material is referred to as metal) is not particularly limited. For example, it is a metal used for steel pipe columns, support anchors, underground steel pipes, and the like.

The sensor 4 has one metal piece to be evaluated in the case of the three-electrode AC impedance method described later, and two metal pieces to be evaluated in the case of the two-electrode AC impedance method, and each metal piece retains electrical insulation. It is arranged and configured so as to.

The accommodating portion 2 is composed of a chemically stable material that does not change the ionic component contained in the accommodating soil 3. The material of the accommodating portion 2 is preferably plastic such as acrylic or vinyl chloride, glass or ceramics.

The accommodating portion 2 has a water supply function and a drainage function. The water supply function and the drainage function need only be able to supply sufficient water to the soil 3 and reduce the amount of water in the soil 3 over time. Therefore, water supply may be performed manually. Further, the drainage may be provided with an opening (not shown) in the accommodating portion 2. Further, the water supply function may be provided with a pump capable of setting the water supply time. Further, an on-off valve for controlling the on / off of drainage may be provided.

As the soil 3, a soil of the same type as the target soil is used. The soil at the site may be collected, or the soil simulating the target soil may be used. Soil classification includes, for example, classification based on the Japanese soil classification system by the Japan Pedology Society.

The corrosion amount estimation device 1 includes a corrosion rate measuring unit 10, a change function calculation unit 20, a data extraction unit 30, and a corrosion amount calculation unit 40. FIG. 2 is an operation flow showing a processing procedure of the corrosion amount estimation device 1. The operation will be described with reference to FIGS. 1 and 2.

The corrosion rate measuring unit 10 supplies water to the soil in which the sensor 4 containing the metal to be evaluated is buried, and the corrosion rate of the metal in the sensor 4 with respect to the elapsed time until the water content of the soil is saturated, and the water content of the soil 3. The elapsed time when the saturated rate is continued, the corrosion rate of the metal in the sensor 4, and the elapsed time after stopping the water supply from the saturated water content of the soil, and the corrosion of the metal in the sensor 4. Each corrosion rate of the rate is measured a plurality of times (step S1). The method of measuring the corrosion rate of the metal in the sensor 4 will be described in detail later.

The change function calculation unit 20 calculates a plurality of change functions representing the respective corrosion rates with respect to the elapsed time (step S2). Details will be described later.

The data extraction unit 30 obtains a plurality of precipitation interval data including a set of a set of a rain day and a rain day interval representing an interval until the next rain day from a plurality of rain data representing a day having a predetermined amount of rainfall or more. Extract (step S3). Here, the rainfall above a predetermined level is the amount of rainfall required for the water content of the soil 3 to be saturated.

The rainy day is the number of days when the amount of rain has fallen. If a predetermined amount of rainfall falls for one day, the rainy day is one day, and if it continues for two days, the rainy day is two days. The rainy day interval is an interval between rainy days. For example, if the sunny weather continues for 3 days after a rainy day, the interval between rainy days is 3 days. A specific example of the rainfall interval data will be described later.

The corrosion amount calculation unit 40 calculates the corrosion amount of the metal in the sensor 4 by using the rainfall interval data and the change function (step S4). A description showing a specific example of the calculation of the amount of corrosion will be omitted.

According to the corrosion amount estimation device 1 according to the present embodiment described above, the corrosion amount is calculated from the change function representing the change in the corrosion rate with respect to the water content of the soil and the rainfall data, so that the corrosion amount of the metal in the soil can be determined. It can be predicted easily and in a short period of time.

FIG. 3 is a diagram schematically showing the relationship between rainfall and the water content of soil 3. The horizontal axis of FIG. 3 is the elapsed time.

The moisture content of soil 3 is well linked to precipitation. The water content increases at the same time as the rainfall, and when the rain stops, the water content decreases at the rate peculiar to the soil 3 and repeats the cycle. From FIG. 3, it can be seen that the amount of rainfall below a predetermined amount does not affect the water content of the soil.

From the relationship shown in FIG. 3, the amount of metal corrosion in the sensor 4 can be calculated from the relationship between the change in the water content of the soil and the corrosion rate.

That is, if the relationship between the water content of the soil 3 and the corrosion rate is measured in advance for a period of, for example, about 30 days in terms of elapsed time (elapsed days), the corrosion rate corresponding to most of the rainfall data can be calculated. The amount of corrosion can be calculated by integrating the change function representing the corrosion rate at the rainfall interval extracted from a plurality of rainfall data representing the days when the amount of rainfall exceeds a predetermined value. Therefore, the amount of corrosion can be estimated by a short-term experiment.

Next, each functional component of the corrosion amount estimation device 1 will be described in detail.

(Corrosion rate measuring unit)
The corrosion rate measuring unit 10 has an AC impedance measuring function. In the AC impedance measurement, the metal in the sensor 4 is used as an electrode, and a minute voltage or current is applied between the electrodes by AC to measure the electrical response. The applied voltage or current should be kept small so that the surface of the metal in the sensor 4 does not change. For example, it is about 5 mV. The frequency is varied, for example, in the range of 0.1 Hz to 500 Hz.

A Nyquist diagram can be obtained by measuring the AC impedance. FIG. 4 schematically shows a Nyquist diagram. The horizontal axis of the Nyquist diagram is the real part, and the vertical axis is the imaginary part. Based on the Nyquist diagram, the charge transfer resistance is derived by curve fitting based on a predetermined equivalent circuit.

FIG. 5 is an example of an equivalent circuit assumed to calculate the charge transfer resistance. FIG. 5A is an equivalent circuit when the AC impedance is measured with three electrodes. FIG. 5B is an equivalent circuit when the AC impedance is measured with two electrodes.

The charge transfer resistance Rct in FIG. 5 represents the resistance of the corrosion reaction of the metal in the sensor 4 in the soil 3. The electric double layer Cdl is the capacitance present at the interface between the metal and the soil 3 in the sensor 4. The resistance components Rs1 and Rs2 represent the resistance in soil 3 and other. Volume Cs is a volume component of soil 3. The Warburg impedance Zw is the impedance due to the diffusion process. At the time of curve fitting, the electric double layer Cdl and the capacitance CS may be replaced with CPE (Constant Phase Element).

According to the equivalent circuit shown in FIG. 5, two arcs are theoretically drawn on the Nyquist diagram as shown in FIG. The arc on the high frequency side is derived from soil 3. The arc on the low frequency side is due to the corrosion reaction.

The charge transfer resistance is given by the width at which the arc on the low frequency side of the Nyquist diagram intersects the horizontal axis (real part). The charge transfer resistance when the AC impedance is measured with two electrodes is half the width.

Corrosion rate is proportional to the reciprocal of charge transfer resistance. The proportional coefficient K is calculated by deriving the Tapel gradient from the anode and cathode polarization curves (Reference: "Development of Corrosion Rate Measuring Method for Steel in Concrete (CIPE Method)", Rust, No. 148, p2-8, 2015).

By using the proportionality coefficient K, the corrosion current density (corrosion rate) can be calculated from the reciprocal of the charge transfer resistance. The weight thinning rate, the volume thinning rate, and the like can also be calculated using the corrosion current density.

The corrosion rate measuring unit 10 measures the corrosion rate a plurality of times in response to a change in the water content of the soil 3. FIG. 6 shows a measurement example of the corrosion rate. The horizontal axis is the elapsed time, and the vertical axis is the corrosion rate. FIG. 6 shows an example in which the corrosion rate was measured 5 times while the elapsed time was changed while the soil 3 was being supplied, and the corrosion rate was measured 15 times when the water was drained after the water supply was stopped. ..

The water content of the soil 3 is saturated in the water supply state, and the water supply is continued even after the saturation. Of the five corrosion rate measurements, the fourth and fifth plots are the corrosion rates with saturated moisture content.

In this way, the corrosion rate measuring unit 10 supplies water to the soil 3 in which the metal in the sensor 4 to be evaluated is buried, and the corrosion rate of the metal in the sensor 4 with respect to the elapsed time until the water content of the soil 3 is saturated. , The elapsed time when the water content of the soil 3 is kept saturated and the corrosion rate of the steel material, and the elapsed time after stopping the water supply from the saturated water content of the soil 3 and in the sensor 4. Each corrosion rate of metal corrosion rate is measured multiple times.

(Change function calculation unit)
The change function calculation unit 20 calculates a plurality of change functions from the change in the corrosion rate shown in FIG. That is, the change function calculation unit 20 calculates a plurality of change functions representing changes in the corrosion rate with respect to the elapsed time.

The change function is, for example, an arbitrary function V (t) representing the change of the corrosion rate with respect to the elapsed time shown in FIG. The function V (t) is obtained by curve fitting an arbitrary function to, for example, the change in the corrosion rate shown in FIG.

FIG. 7 schematically shows an example in which the change in the corrosion rate shown in FIG. 6 is curve-fitted by linear approximation. The function from the start of water supply until the corrosion rate increases and becomes almost a stable value is V1 (t) = at, and the function after the stable value is V2 (t) = b. Further, the function of the portion where the corrosion rate decreases after the water supply is stopped is V3 (t) = ct.

In addition to a straight line, a quadratic function or an exponential function may be used. FIG. 8 is a diagram in which V4 (t) = c × exp (dt) + b instead of V3 (t). Note that a, b, c, and d are constants.

As described above, the change function calculation unit 20 represents the change in the corrosion rate of the metal in the sensor 4 from the start of water supply to the soil 3 to the saturation of the water content of the soil 3, the first change function V1 (t). ), The second change function V2 (t) representing the change in the corrosion rate of the metal in the sensor 4 when the water content of the soil 3 is saturated, and the corrosion of the metal in the sensor 4 in the drainage process of the soil 3. The third change function V3 (t) representing the change in velocity is calculated. The amount of corrosion in a predetermined period can be calculated from these change functions.

FIG. 9 is a diagram schematically showing that the amount of corrosion can be calculated by combining the change functions. The horizontal axis of each figure of FIG. 9 is the elapsed time, and the vertical axis is the corrosion rate.

FIG. 9A shows a change in the corrosion rate when it rains in an amount that saturates the water content of the soil 3 for one day. The amount of corrosion in this case is obtained by the sum of the integrated amounts obtained by integrating each of the change functions V1 (t) and V2 (t) with the elapsed time (Qw1). In addition, in FIG. 9, continuous rain is described as continuous water supply.

FIG. 9B shows the change in the corrosion rate when the amount of rain that saturates the water content of the soil 3 continues to fall for two days. The amount of corrosion in this case is obtained by the sum of the integrated amounts obtained by integrating each of the change functions V1 (t) and V2 (t) with the elapsed time, as in FIG. 9A (Qw2). However, in this case, the elapsed time for integrating V2 (t) is 2 days, which is different from FIG. 9 (a).

FIG. 9 (c) shows the change in corrosion rate during the day after the rain stopped. The amount of corrosion in this case is a value obtained by integrating the change function V3 (t) with an elapsed time of 1 day (Qd1).

FIG. 9D shows the change in corrosion rate during the two days after the rain stopped. The amount of corrosion in this case is a value obtained by integrating the change function V3 (t) over an elapsed time of 2 days (Qd2).

In this way, the amount of corrosion can be calculated from the change function and the rainfall situation. The rainfall situation can be extracted from a plurality of precipitation data representing the days when the amount of precipitation exceeds a predetermined value. For example, the amount of corrosion can be calculated by extracting the rainfall time, which indicates the time when it rained, and the rainfall interval, which represents the interval between rainfalls, from the precipitation data released by the Japan Meteorological Agency.

(Data extraction unit)
The data extraction unit 30 extracts a plurality of precipitation interval data including a set of a set of a rainfall and a rainfall interval representing an interval until the next rainfall from a plurality of rainfall data representing a time when the amount of rainfall is equal to or more than a predetermined value.

FIG. 10 shows an example of precipitation data for 42 days. The first column is the "day" of the month and day, and the second column is the daily rainfall (daily rainfall (mm)) of each day. The unit of the rainfall time of the embodiment described below will be described in (days). Even if the unit of rainfall time is (hours), the amount of corrosion can be calculated by the method described below.

It can be seen that there was a daily rainfall of 2 mm on the ○ month × day, and then there was no rainfall for 3 days, and there was a daily rainfall of 7.5 mm on the ○ month × 4. Although omitted from this point onward, it has been shown that there was more than the prescribed amount of precipitation 16 times (Sunday) in 42 days. Here, the precipitation above a predetermined level means that the daily rainfall is 0.5 mm or more in this example.

The data extraction unit 30 extracts a plurality of precipitation interval data including a set of a rain day and a rain day interval representing an interval between the rain days and the rain days from the rainfall data shown in FIG.

From the precipitation data shown in FIG. 10, the precipitation interval data of (tw1, td3), (tw1, td2), (tw1, td8), ... Is extracted. The subscript w is wet, and the number is the number of consecutive days of continuous rainfall. The subscript d represents dry, and the number represents the number of consecutive days of continuous drainage (days when it does not rain).

(Corrosion amount calculation unit)
The corrosion amount calculation unit 40 calculates the corrosion amount of the metal in the sensor 4 by using the rainfall interval data extracted by the data extraction unit 30 and the change function.

○ Month × day is the day when there was only one day of rainfall under the condition that there was no rainfall on the previous day, which matches the condition shown in FIG. 9 (a). In this case, the corrosion amount calculation unit 40 obtains the corrosion amount of ◯ month × day by the sum of integrals of the change functions V1 (t) and V2 (t) (Qw1).

The amount of corrosion from ○ month × day +1 day to ○ month × day +3 day is obtained by integrating the change function V3 (t) with t = 3.

That is, when the magnitude of the rainfall day in the rainfall interval data is one day or less, the corrosion amount calculation unit 40 sets the corrosion amount on the first day as the first change function V1 (t) and the second change function V2 (t). ), And the amount of corrosion of the number of days in the rainfall interval data is obtained by integrating the third change function V3 (t).

The rainfall interval data from XX month x day + 16 days to XX month x day + 20 days is (tw2, td3). In this case, the corrosion amount calculation unit 40 obtains the corrosion amount of ○ month × day +16 days to ○ month × day +17 days by the sum of integrals of the change functions V1 (t) and V2 (t) (Qw2). ). In this case, the amount of corrosion Qw2 is larger than that of Qw1 because the second change function V2 (t) is integrated at t = 1 day. The amount of corrosion on XX days + 18 days to XX days + 20 days is obtained by integrating the third change function V3 (t) at t = 3 days.

That is, when the magnitude of the rainfall day in the rainfall interval data is larger than one day, the corrosion amount calculation unit 40 sets the corrosion amount on the first day by the first change function V1 (t) and the second change function V2 (t). ) Is obtained by integrating the second change function V2 (t) to obtain the corrosion amount of (rainfall day-1 day), and the corrosion amount of the number of days of the rainy day interval of the rainfall interval data is calculated by the third change function V3. It is obtained by integrating (t).

The third column of FIG. 11 shows the amount of corrosion calculated as described above. The first and second columns of FIG. 11 are the same as those of FIG.

The corrosion amount calculation unit 40 obtains the total amount of corrosion calculated as shown in FIG. This total is the amount of metal corroded in the sensor 4 for 42 days.

As described above, according to the corrosion amount estimation device 1 of the present embodiment, the corrosion amount of the metal in the sensor 4 in the soil 3 can be easily estimated in a short period of time. If the relationship between the water content of soil 3 and the corrosion rate is measured by the corrosion amount estimation device 1 for a period of, for example, about 30 days in terms of elapsed time (elapsed days), the corrosion rate corresponding to most precipitation data is calculated. be able to. That is, for example, if an experiment is conducted for a period of about 30 days to obtain a change function, the long-term corrosion amount can be estimated by inputting long-term rainfall data.

FIG. 12 is a diagram schematically showing the amount of corrosion estimated in this way. The horizontal axis is the elapsed time (for example, year), and the vertical axis is the amount of corrosion. In this way, it is possible to estimate the amount of corrosion during the period in which the rainfall data was acquired from the rainfall data.

The present invention is not limited to the above-described embodiment, and can be modified within the scope of the gist thereof. For example, the corrosion amount calculation unit 40 may add a function of correcting the calculated corrosion amount in addition to integrating the change function to calculate the corrosion amount.

In the case of a type of steel in which a film is formed on the surface of the metal in the sensor 4 and the corrosion rate decreases with time, it is known that the amount of corrosion Q follows Q = kT ⁿ . Here, k is the amount of corrosion in the initial year. T is a period and n is a constant of 0.4 to 0.6.

Therefore, the corrosion amount k for one year may be obtained by the corrosion amount estimation device 1 of the present invention, and the corrosion amount for the period one year or more ahead may be calculated by the above formula using the period T to be predicted. Moreover, to calculate the amount of corrosion based on rainfall data of the period T to be predicted may be a predictive value of the corrosion rate Q it is divided by T ^n.

Moreover, although the example of the rainfall data is shown by the daily rainfall per day, the corrosion amount may be calculated by the hourly rainfall per hour as described above. Alternatively, it may be calculated by the amount of rainfall for 10 minutes. If it is the elapsed time, the amount of corrosion can be calculated by the same method regardless of its size.

As described above, it goes without saying that the present invention includes various embodiments not described here. Therefore, the technical scope of the present invention is defined only by the matters specifying the invention relating to the reasonable claims from the above description.

1: Corrosion amount estimation device 2: Storage part 3: Soil 4: Sensor (metal in the sensor)
10: Corrosion rate measurement unit 20: Change function calculation unit 30: Data extraction unit 40: Corrosion amount calculation unit

Claims (4)

The corrosion rate of the steel material with respect to the elapsed time until the water content of the soil is saturated by supplying water to the soil in which the steel material to be evaluated is buried, the elapsed time when the water content of the soil is kept saturated, and the above. A corrosion rate measuring unit that measures the corrosion rate of the steel material, the elapsed time after the water supply is stopped from the saturated water content of the soil, and the corrosion rate of the steel material multiple times.
A change function calculation unit that calculates a plurality of change functions representing each corrosion rate with respect to the elapsed time,
A data extraction unit that extracts a plurality of rainfall interval data consisting of a combination of a rainfall time and a rainfall interval representing an interval until the next rainfall from a plurality of rainfall data representing a time when a predetermined amount of rainfall or more has occurred.
A corrosion amount estimation device including a corrosion amount calculation unit that calculates the corrosion amount of the steel material by using the rainfall interval data and the change function. In the corrosion amount estimation device according to claim 1,
The change function is
The first change function representing the change in the corrosion rate of the steel material from the start of water supply to the soil until the water content of the soil is saturated, and
A second change function representing a change in the corrosion rate of the steel material in a state where the water content of the soil is saturated, and
Including a third function of change representing the change in the corrosion rate of the steel material in the soil drainage process.
The corrosion amount calculation unit
When the magnitude of the rainfall time of the rainfall interval data is one day or less, the amount of corrosion in the first day corresponds to the first change function, the second change function, and the third change function, respectively. Calculated by the sum of the values integrated with time and rainfall interval
When the magnitude of the rainfall time in the rainfall interval data is larger than one day, the amount of corrosion in the first day is integrated by the rainfall time and the rainfall interval corresponding to the first change function and the second change function, respectively. It was calculated by the sum of the values, and the amount of corrosion (rainfall time-1 day) was calculated by the sum of the values integrated by the rainfall time corresponding to the second change function and the rainfall interval corresponding to the third change function. A corrosion amount estimation device characterized in that the total amount of corrosion is the amount of corrosion of the steel material. It is a corrosion amount estimation method performed by the corrosion amount estimation device.
The corrosion rate of the steel material with respect to the elapsed time until the water content of the soil is saturated by supplying water to the soil in which the steel material to be evaluated is buried, the elapsed time when the water content of the soil is saturated, and the above-mentioned The corrosion rate of the steel material, the elapsed time after the water supply was stopped from the saturated water content of the soil, and the corrosion rate of the steel material were measured multiple times.
A plurality of function of change representing each corrosion rate with respect to the elapsed time was calculated.
From a plurality of rainfall data representing the time when the amount of rainfall exceeds a predetermined value, a plurality of rainfall interval data consisting of a combination of the rainfall time and the rainfall interval representing the interval until the next rainfall is extracted.
A method for estimating the amount of corrosion, which comprises calculating the amount of corrosion of the steel material using the rainfall interval data and the change function. In the method for estimating the amount of corrosion according to claim 3,
The change function is
The first change function representing the change in the corrosion rate of the steel material from the start of water supply to the soil until the water content of the soil is saturated, and
A second change function representing a change in the corrosion rate of the steel material in a state where the water content of the soil is saturated, and
Including a third function of change representing the change in the corrosion rate of the steel material in the soil drainage process.
The amount of corrosion of the steel material is
When the magnitude of the rainfall time of the rainfall interval data is one day or less, the amount of corrosion in the first day corresponds to the first change function, the second change function, and the third change function, respectively. Calculated by the sum of the values integrated with time and rainfall interval
When the magnitude of the rainfall time in the rainfall interval data is larger than one day, the amount of corrosion in the first day is integrated by the precipitation time and the precipitation interval corresponding to the first change function and the second change function, respectively. It was calculated by the sum of the values, and the amount of corrosion (rainfall time-1 day) was calculated by the sum of the values integrated by the rainfall time corresponding to the second change function and the rainfall interval corresponding to the third change function. A method for estimating the amount of precipitation, which is the total amount of corrosion.

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