JP6518939B2 - Method of estimating moisture of concrete structure and system of estimating moisture of concrete structure - Google Patents

Description

  The present invention relates to a method of estimating moisture of a concrete structure and a system of estimating moisture of a concrete structure.

  In concrete structures, defects such as junk and cracks may occur, and water may be accumulated therein to corrode or weaken reinforcing bars and structural materials that constitute the concrete structure. Therefore, it is desirable to realize a technology that can estimate the distribution of water in a concrete structure.

  For example, a neutron beam source and a panel type high sensitivity neutron detector are disposed so as to sandwich the concrete structure, and the concrete structure is transmitted by the concrete structure and the neutron emitted from the neutron beam source is detected by the detector. Patent Document 1 discloses a technique for detecting a defect of

  Also, inject the cement into the back side of the cement with an injection agent added with a tracer such as a boron compound as a hardening material, irradiate neutrons from the cement surface side, measure the number of thermal neutrons rescued by the tracer, and inject cement. A technique for detecting the degree is disclosed (Patent Document 2).

JP 2002-82073 A JP-A-8-94552

  By the way, as a neutron source for generating neutrons to be irradiated, there are a method using a nuclear reactor and a method using an accelerator. In the transmission type neutron beam detection, it is necessary to arrange the object to be measured between the neutron beam source and the sensor, and when using a concrete structure existing mainly outdoors as the object to be measured, movement of the neutron beam source or sensor is required. It is impossible or difficult, and depending on the shape and thickness of the object to be measured, placement on the back side may not be possible. In addition, in principle, the size of the system is increased due to the arrangement of the neutron source and the detector. Recently, some research institutes are developing mobile accelerators that can be used outdoors, but they are still developing.

  Moreover, it is impossible in principle to apply the technique which makes a boron compound etc. a tracer to the existing concrete structure to which the tracer is not added.

  The present invention provides a method for estimating the moisture of a concrete structure and a system for estimating the moisture of the concrete structure, which detect moisture accumulated in junka, cracks, etc. in the concrete structure.

  In the method of estimating moisture of a concrete structure using neutrons according to claim 1 of the present invention, the relationship between the position of the radiation source of neutrons and the position of the measurement point, on the condition of the element density composition of concrete and the content of bound water Modeling the response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure composed of the concrete on the basis of the radiation including the Monte Carlo method and the SN method A first step of analyzing by a transport calculation code, and a second step of measuring a response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure to be investigated Estimating the presence of water in the concrete structure to be investigated using the measured response and the analyzed response Characterized in that it comprises of the steps.

  Here, the third step is a database storing the analyzed response analyzed for each type of concrete, which is a combination of a plurality of the element density compositions and the content of the binding water in the first step. The presence of moisture in the concrete structure to be investigated using the measured response and the analyzed response to the type of concrete constituting the concrete structure to be investigated. It is preferable to estimate

（ただし、Ａｒ_ｉ，ｊは、前記線源の位置ｉから放射された中性子が前記調査対象であるコンクリート構造物を介して前記計測点の位置ｊにおいて計測されるときの前記周辺領域からの応答の寄与）により求めることが好適である。 Further, in the first step, the inspection target area and the peripheral area are respectively set and modeled in the concrete structure to be investigated, and the inspection target area is divided into m division target areas k (m is 2 or more). The mesh is divided into integers, k = 1,..., M), and the positions i (i is an integer of 2 or more) of the plurality of radiation sources and the positions j (j The contribution ri _{, j, k} from each of the division target regions k for each of the combinations is determined, and the neutrons emitted from the position i of the radiation source are measured via the concrete structure to be investigated The analyzed response R _{i, j} when measured at position j of

(Where Ar _{i, j} is the response from the surrounding area when neutrons emitted from the position i of the radiation source are measured at the position j of the measurement point through the concrete structure to be investigated) It is preferable to obtain by

（ただし、Ｓは、前記線源の強度）
の関係を用いて前記分割対象領域ｋにおける水分の体積率ω_ｋを推定することが好適である。 In the first step, for each combination of the position i of the radiation source and the position j of the measurement point, contribution rc _i when the concrete is present at a volume ratio of 100% in the division target area k _{j, k} , and a contribution r _{w i, j, k} when the water is present at a volume ratio of 100% in the division target area _k , and the second step determines the position i of the radiation source and the measurement For each combination of point positions j, the response D _{i, j} is measured when neutrons emitted from the radiation source are measured at the measurement point via the concrete structure to be investigated, Step 3 is

(Where S is the intensity of the radiation source)
It is preferable to estimate the volume fraction ω _k of water in the division target region k using the relationship of

Further, it is preferable to estimate the volume fraction ω _k of water in the division target region k which minimizes the error of the equation (2).

  In addition, it is preferable to include a fourth step of visualizing the presence of water in the concrete structure to be investigated, which is estimated in the third step.

  Further, it is preferable that the radiation source used in the second step has a structure in which a region other than a region facing the concrete structure to be investigated is covered with a neutron shielding means.

  In the second step, it is preferable to move the radiation source and the measurement point sequentially on the surface of the concrete structure to be examined to measure the actually measured response.

  According to the ninth aspect of the present invention, there is provided a system for estimating the moisture content of a concrete structure using neutrons, wherein the relationship between the position of the radiation source of neutrons and the position of the measurement point is conditional on the element density composition of concrete and the content of bound water. And store the results of modeling and analyzing the response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure formed by the concrete based on the above. Storage means, actual response measurement means for measuring the response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure to be investigated, the measured response, and the analysis Water estimation means for estimating the presence of water in the concrete structure to be investigated using the determined response To.

  Here, it is preferable to further include display means for visualizing and displaying the presence of the water in the concrete structure to be surveyed estimated by the water estimation means.

  According to the method of estimating the moisture content of a concrete structure using neutrons according to claim 1 of the present invention, the position of the radiation source of the neutron and the position of the measurement point, on the condition of the element density composition of the concrete and the content of the bound water Modeling the response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure to be surveyed composed of the concrete based on the relationship between the Monte Carlo method and the SN method And a second step of measuring a response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure to be investigated. Estimating the presence of moisture in the concrete structure to be investigated using the step, the measured response and the analyzed response Third by providing the steps of the distribution of moisture in the evaluation concrete structure which is the subject can be estimated accurately that. In addition, it becomes possible to estimate the presence of water from one direction of the concrete structure, and it becomes possible to apply the present invention to an existing concrete structure without requiring a tracer.

  In the third step, a database storing the analyzed response analyzed for each type of concrete, which is a combination of a plurality of the element density compositions and the content of the binding water in the first step Referring to the measured response and the analyzed response to the type of concrete constituting the concrete structure to be surveyed, the presence of water in the concrete structure to be surveyed is determined. By estimating, the presence of water in the concrete structure corresponding to the measured response can be estimated based on the analyzed response registered in advance as the database.

Further, in the first step, the inspection target area and the peripheral area are respectively set and modeled in the concrete structure to be investigated, and the inspection target area is divided into m division target areas k (m is 2 or more). The mesh is divided into integers, k = 1,..., M), and the positions i (i is an integer of 2 or more) of the plurality of radiation sources and the positions j (j The contribution ri _{, j, k} from each of the division target regions k for each of the combinations is determined, and the neutrons emitted from the position i of the radiation source are measured via the concrete structure to be investigated The volume ratio of water in the division target area k obtained by dividing the concrete structure can be determined by determining the analyzed response R _{i, j} when measured at the position j of .

In the first step, for each combination of the position i of the radiation source and the position j of the measurement point, contribution rc _i when the concrete is present at a volume ratio of 100% in the division target area k _{j, k} and contributions r _{w i, j, k} when the water is present at a volume ratio of 100% in the division target area k are obtained, and in the second step, the position i of the radiation source and the measurement point The response D _{i, j} when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure to be examined is measured for each of the combinations of the position j of In the step of, by estimating the volume ratio ω _k of the water in the division target area k using the relationship of the equation (2), the contribution rc _{i, j, k} and the contribution r _{w i, j, k} can be _obtained . On the basis of It is possible to estimate the volume fraction omega _k of the moisture in the serial division target region k.

Further, by estimating the volume ratio ω _k of water in the division target region k which minimizes the error of the equation (2), the solution of the simultaneous equations derived from the equation (2) is not solved. Based on the contribution rc _{i, j, k} and the contribution r _{w i, j, k} , it is possible to estimate the volume fraction ω _k of water in the division target area k.

  Further, by providing a fourth step of visualizing the presence of water in the concrete structure to be surveyed estimated in the third step, the distribution of the estimated water can be easily grasped by the user's vision It can be displayed in an aspect.

  Further, the radiation source used in the second step has a structure in which the neutron shielding means covers a region other than the region facing the concrete structure to be investigated, so that the concrete structure from the neutron beam source Neutrons that directly reach the neutron detector 106 without being incident and scattered therein can be reduced.

  In the second step, it is preferable to move the radiation source and the measurement point sequentially on the surface of the concrete structure to be examined to measure the actually measured response.

  According to the ninth aspect of the present invention, there is provided a system for estimating the moisture content of a concrete structure using neutrons, wherein the relationship between the position of the radiation source of neutrons and the position of the measurement point is conditional on the element density composition of concrete and the content of bound water. And store the results of modeling and analyzing the response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure formed by the concrete based on the above. Storage means, actual response measurement means for measuring the response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure to be investigated, the measured response, and the analysis And means for estimating the presence of moisture in the concrete structure to be investigated using the determined response. , The distribution of moisture in the evaluation in the concrete structure is the object can be estimated accurately. In addition, it becomes possible to estimate the presence of water from one direction of the concrete structure, and it becomes possible to apply the present invention to an existing concrete structure without requiring a tracer.

  Here, by further comprising display means for visualizing and displaying the presence of the water in the concrete structure to be investigated estimated by the water estimation means, the distribution of the estimated water can be grasped by the user's vision It can be displayed in an easy manner.

It is a figure which shows the structure of the water | moisture content estimation system in embodiment of this invention. It is a figure which shows the structure of the water | moisture content estimation apparatus in embodiment of this invention. It is a schematic diagram which shows the structure of the neutron beam source in embodiment of this invention. It is a figure which shows the scattering model of the neutron in embodiment of this invention. It is a figure which shows the example of a setting of the division | segmentation object area | region of the concrete structure in embodiment of this invention. It is a figure which shows the scattering model when analyzing the response of the neutron in embodiment of this invention. It is a flowchart of the water | moisture-content estimation method in embodiment of this invention.

  The water estimation system 100 for concrete structures using neutrons according to the embodiment of the present invention includes a water estimation device 102, a neutron beam source 104, and a neutron detector 106, as shown in FIG. The neutron beam source 104 and the neutron detector 106 are disposed on the same surface side of the concrete structure 200 to be investigated.

  The water | moisture-content estimation apparatus 102 is comprised including the process part 10 which is the basic composition of a common computer, the memory | storage part 12, the input part 14, the output part 16, and the interface part 18 as shown in FIG.

  The processing unit 10 includes computing means such as a CPU, and implements the moisture estimation process in the concrete structure 200 performed in the moisture estimation device 102 by executing the moisture estimation program stored in the storage unit 12. The storage unit 12 is configured to include storage devices such as a semiconductor memory and a hard disk that are connected so as to be accessible from the processing unit 10. The storage unit 12 stores a moisture estimation program, various parameters, measurement data, and the like. The input unit 14 is configured to include an input device such as a keyboard and a mouse. The input unit 14 is used to input various parameters and the like used by the moisture estimation device 102. The output unit 16 is configured to include an output device such as a display or a printer. The output unit 16 functions as a display unit that visualizes and displays the processing result obtained by the water estimation device 102. The output unit 16 presents, to the user, information related to the processing in the moisture estimation device 102. The interface unit 18 includes an analog / digital converter and the like. The interface unit 18 is used to load data indicating the dose of neutrons detected by the neutron detector 106 into the moisture estimation device 102.

The neutron source 104 includes a neutron source such as a neutron generator tube or an RI source such as ²⁵² Cf. The neutron beam source 104 is preferably shielded around the neutron source 20, as shown in the cross-sectional view of FIG. The shielding is provided so as to cover the area other than the direction toward the concrete structure 200 which is the investigation target, that is, the area other than the area facing the concrete structure 200. By shielding the neutron source 20, when the neutron beam source 104 is installed on the surface of the concrete structure 200 to be investigated, neutrons and gamma rays do not enter and scatter in the concrete structure 200, and a neutron detector Direct arrival of neutrons or gamma rays at 106 can be suppressed.

  For example, it is preferable to provide multiple types of shielding walls 22, 24, 26. The shielding wall 22 is provided to heat fast neutrons. The shielding wall 22 is made of, for example, a material containing paraffin. The shielding wall 24 is provided to absorb the thermalized neutrons. The shielding wall 24 is made of a material containing cadmium. The shielding wall 26 is provided to absorb gamma rays. The shielding wall 26 is made of, for example, a material containing lead. The shielding walls 22 to 26 may have thicknesses of, for example, 25 cm, 1 mm, and 5 cm, respectively.

  The neutron detector 106 detects neutrons emitted from the neutron beam source 104 and reflected or scattered by the concrete structure 200. The neutron detector 106 can be a He-3 counter, a BF3 detector, or the like. When the neutron detector 106 detects neutrons, the neutron detector 106 outputs the neutrons to the water estimation device 102 through the interface unit 18. When receiving the detection signal of the neutron detector 106, the processing unit 10 of the moisture estimation device 102 counts the number of detected neutrons per unit time. Thereby, the dose rate (counting rate) of the neutron beam is measured.

  In the water estimation system 100 according to the present embodiment, as shown in FIG. 4, neutrons emitted from the neutron source 104 are made incident from one surface side of the concrete structure 200 and neutrons reflected from the concrete structure 200 are reflected. The distribution of water in the concrete structure 200 is evaluated by detecting the neutrons with a neutron detector 106 provided on the same surface side. For this reason, it becomes possible to evaluate the distribution of water from the same surface side of the concrete structure 200, that is, in one direction. The fast neutrons generated from the neutron source 104 are reflected or scattered by the concrete structure 200 or the junka X or the like to reach the neutron detector 106. At this time, if there is a "water pool" in which water is collected in the Janka X, etc., the neutrons are decelerated by hydrogen in the water, and it becomes easier to be converted into thermal neutrons than in the case where there is no "water pool". The distribution of water in the concrete structure 200 is evaluated by focusing attention on the difference in nuclear reaction. According to the moisture estimation system 100, it is possible to estimate the distribution of moisture from the surface of the concrete structure 200 to a depth about the number average free path of neutrons.

  In the water | moisture-content estimation system 100, as shown in FIG. 5, the concrete structure 200 which is evaluation object is divided into the test object area | region 202 and its periphery area | region 204, and distribution of the water | moisture content in the test object area | region 202 is evaluated. At this time, the inspection target area 202 is divided into a plurality of (m: m is an integer of 2 or more) division target areas k (k is an area number: k = 1,..., M). The distribution of water in the concrete structure 200 is evaluated by estimating the water in the container.

  In the example of FIG. 5, with one surface (X-Y plane) of the concrete structure 200 as a measurement surface, the inspection target region 202 of the measurement surface is divided into six regions and meshed further in the depth direction (Z direction) It is divided into two layers. That is, the layer far from the measurement surface of the inspection target region 202 is divided into division target regions k (1 ≦ k ≦ 6), and the layer close to the measurement surface is divided into division target regions k (7 ≦ k ≦ 12) . Of course, the number of divisions of the inspection target area 202 is not limited to this, the number of divisions in the surface may be other than six, and the number of layers in the depth direction may also be other than two.

In the water estimation system 100, the neutron beam source 104 and the neutron detector 106 are arranged in the division target region k on the measurement surface side of the concrete structure 200, the response is measured, and the distribution of water corresponding to the measured response is Analysis is performed by the estimation device 102. That is, for each combination of the position i of the division target region k where the neutron beam source 104 is arranged and the position j of the division target region k where the neutron detector 106 is arranged _, the response R _i analyzed as the actual response D _{i, j , J} is determined to match the distribution of water.

For example, in the inspection target area 202 of FIG. 5, the neutron beam source 104 is disposed in the division target area of area number 7, and the neutron detectors 106 are sequentially disposed in the division target areas of area numbers 10, 11 and 12, respectively. The actual response D _7,10 , D ₇ , ₁₁ , D ₇ , _{12 of the case} is measured. The actual response D _{8, 10} in the case where the neutron beam source 104 is disposed in the division target area of the area number 8 and the neutron detectors 106 are sequentially disposed in the division target areas of the area numbers 10, 11, 12 respectively. , D ₈ , ₁₁ , D ₈ , ₁₂ are measured. In addition, actual response D _{9, 10} when neutron beam source 104 is arranged in the division target area of area number 9, and neutron detectors 106 are arranged in order in the division target areas of area numbers 10, 11 and 12, respectively. , D ₉ , ₁₁ and D ₉ , ₁₂ are measured. Furthermore, the position of the neutron beam source 104 and the position of the neutron detector 106 are interchanged to measure the actual response. That is, actual response D _10, 7 when neutron beam source 104 is arranged in the division target area of area number 10 and neutron detectors 106 are arranged in order in the division target areas of area numbers 7, 8, 9 respectively , D 10, ₈ and D ₁₀ , ₉ are measured. The actual response D _{11, 7} in the case where the neutron beam source 104 is disposed in the division target area of the area number 11 and the neutron detectors 106 are sequentially disposed in the division target areas of the area numbers 7, 8, and 9 respectively. , D ₁₁ , ₈ and D ₁₁ , ₉ are measured. The actual response D _12,7 when the neutron beam source 104 is arranged in the division target area of the area number 12 and the neutron detectors 106 are sequentially arranged in the division target areas of the area numbers 7, 8, 9 respectively , D ₁₂ , ₈ and D ₁₂ , ₉ are measured.

  At the time of measurement, it is preferable to perform the measurement in such a measurement time that the statistical error of the measurement data is sufficiently reduced.

  On the other hand, the water estimation device 102 performs analysis based on the radiation transport calculation code. The moisture estimation device 102 analyzes the division target region k of the concrete structure 200 using a radiation transport calculation code that can handle a three-dimensional shape, for example, a general-purpose code such as MCNP based on Monte Carlo method or TERT based on SN method.

  For example, it is assumed that one neutron is generated per second from the position i of the neutron beam source 104, and the response (counting rate and dose rate) obtained at the position j of the neutron detector 106 Contributions need to be assessed region by region. In addition, the influence from the peripheral area 204 also needs to be considered.

ここで、ｒ_{ｉ，ｊ，ｋ}は中性子線源１０４の位置ｉ及び中性子検出器１０６の位置ｊとした場合の分割対象領域ｋからの寄与、Ａｒ_ｉ，ｊは周辺領域２０４からの寄与を示す。 That is, the response R _{i, j} in the case where the position i of the neutron beam source 104 and the position j of the neutron detector 106 are represented by Formula (3).

Here, r _{i, j, k} represents the contribution from the division target area k when the position i of the neutron beam source 104 and the position j of the neutron detector 106 are taken, and Ar _{i, j} represents the contribution from the peripheral area 204 .

  The behavior of neutrons incident on the concrete structure 200 is, as shown in FIG. 6, the attenuation of fast neutrons from the neutron source 104 to the reflection point A and the scattering at the reflection point A by noncollision transmission and collision. Expressed by scattering.

The non-collision flux Φ _A (E) of the neutron beam at the reflection point A can be expressed by Equation (4). Here, E is the initial energy of neutrons, S is the initial intensity of neutrons, P1 is the distance from neutron source 104 to reflection point A, σ _T (E) is the total cross section of neutrons of energy E.

The first-time scattered radiation source FS (E ′) at the reflection point A can be expressed by Equation (5). Here, σ _S (E, E ′, θ1, θ2) is a differential scattering cross section when energy changes from incident energy E to reflected energy E ′ and angle changes from incident angle θ1 to reflection angle θ2.

The flux Φ _B (E ′) in the neutron detector 106 can be expressed by equation (6). Here, B (E ′) is a buildup coefficient indicating the contribution of the scattered component in the path from the reflection point A to the neutron detector 106 by neutrons having the energy E ′, and P 2 is from the reflection point A to the neutron detector 106 The distance, σ _T (E ′), is the total cross section of the neutron of energy E ′.

Neutrons of energy E are emitted from the position i of the neutron source 104, and each divided target area k is scattered as a reflection point A, and contribution of neutrons detected as neutrons of energy E 'at the position j of the neutron detector 106 r _{i, j, k} can be calculated by setting the initial intensity S of neutrons to 1 in the flux Φ _B (E ′) of equation (6). That is, from the relationship between the shape and size of the concrete structure 200 and the position i of the neutron beam source 104 and the position j of the neutron detector 106, the distance P1 from the neutron beam source 104 to the reflection point A (each divided target area k) Since the distance P2 from the reflection point A to the neutron detector 106 and the incident angle θ1 and the reflection angle θ2 with respect to the reflection point A are geometrically determined, the flux Φ _B () can be obtained by substituting these values into equation (6). E ′) can be determined as the neutron contribution r _{i, j, k} .

Here, the total cross-sectional areas σ _T (E) and σ _T (E ′) in Equation (4) and Equation (6) are determined based on the element density composition of the concrete that constitutes the concrete structure 200. In addition to the element density composition of the concrete structure 200, the differential scattering cross section σ _S (E, E ′, θ1, θ2) at the reflection point A is determined based on the atomic number density of water collected in a junka or the like. . Approximately, the differential scattering cross section of the concrete constituting the concrete structure 200 and the differential scattering cross section of water can be determined from the volume ratio (volume ratio) at each reflection point A. That is, the differential scattering cross-sectional area of the target region containing a considerable amount of water other than the concrete constituting the concrete structure 200 is the differential scattering cross-sectional area of the concrete constituting the concrete structure 200 and the differential scattering cross-sectional area of water Can be multiplied by each volume ratio and added.

Therefore, the differential scattering cross section σ _SC at the reflection point A determined based on the element density composition of the concrete structure 200 as the reflection point A being concrete that constitutes the concrete structure 200 (100% by volume of concrete) The contribution r _{i, j, k} when (E, E ′, θ 1, θ 2) is applied is obtained as the contribution r c _{i, j, k} . In addition, contribution r _i, when the differential scattering cross section σ _SW (E, E ′, θ1, θ2) at the reflection point A of water is applied as the reflection point A is water (100% volume ratio of water) Find _{j, k} as contributions r _{w i, j, k} . Then, assuming that the volume ratio ω _k of water contained in the division target region k is the water content, the response measured by the neutron detector 106 is expressed by Equation (7).

Equation (8) is obtained by expanding Equation (7).

By substituting the measured response _{Di, j} into the equation (8) by sequentially moving the neutron beam source 104 and the neutron detector 106 to the position i and the position j respectively in the concrete structure 200 to be evaluated, A simultaneous equation with the volume ratio of water ω _k is obtained. Therefore, the volume ratio omega _k of the water in the divided region of interest k by solving the simultaneous _equations, that is, to determine the distribution of the water in each of the divided target area k obtained by dividing the inspection area 202 of the concrete structure 200.

However, the contribution _{rc i, j, k,} contributing _{rw i, j,} the contribution _{Ar i} from _k and the peripheral region _204, the simulation of calculating the _j includes such calculation error, measured responses _{D i, j} Also include uncertainty such as statistical error. Therefore, Equation (8) does not hold strictly. Then, if the volume ratio ω _{k of} water such that the error of Expression (8) is minimized is obtained, the water content of the division target area k of the concrete structure 200 can be estimated.

For example, the least squares method can be applied to estimate the distribution of water in the concrete structure 200. The residual R of the constant term C _{i, j} on the left side and the calculated value on the right side of Expression (8) is defined as Expression (9) as an objective function based on the least squares method.

The steepest descent method is applied to minimize this objective function. As a constraint condition, a condition that water volume ratio ω _k is 0 or more is set. In general, it is impossible to solve the problem given by Equation (9) in a closed-form operation, and it is necessary to perform some repetitive calculations. Then, using an algorithm for obtaining a vector sequence ω _k ⁽⁰⁾ , ω _k ⁽¹⁾ ,..., Ω _k ⁽ⁿ⁾ such that equation (10) is obtained and this number sequence converges to the minimum value of the objective function .

This algorithm generally consists of the following three steps:
(1) An initial point ω _k ⁽⁰⁾ of a suitable volume ratio of water ω _k is given, and a parameter n representing the number of repetitions is 0.
(2) It is determined whether the volume ratio ω _k ^{(n) of} water obtained with respect to the current parameter n is a solution of equation (9). If the volume ratio of water ω _k ⁽ⁿ⁾ satisfies the determination condition, the calculation is ended and the volume ratio of water ω _k ⁽ⁿ⁾ is solved. If the condition is not satisfied, the process proceeds to the next step.
(3) Based on the calculation result for the parameter n, the volume ratio ω _k ^{(n + 1)} of new water for reducing the objective function f (ω) is _obtained . The parameter n is incremented by 1 and the process returns to step (2).

In order to determine the next water volume ratio ω _k ⁽ⁿ⁾ in the n-th repeated calculation, it is necessary to determine the search direction from the current water volume ratio ω _k ^(n-1) and the step width along that direction There is. As a result, the volume ratio ω _k ^{(n + 1)} of the ^{(n + 1) th} water is obtained by the equation (11).

Here, p _k ⁽ⁿ⁾ is a unit vector representing a direction, and α _k ⁽ⁿ⁾ is a positive scalar value representing a step width. The search direction p _k ⁽ⁿ⁾ is obtained by the steepest descent method using Expression (12).

As described above, the least squares method is applied to determine the volume ratio ω _{k of} water that minimizes the difference (error) between the left side and the right side of the simultaneous equations of Equation (8). By this, it is possible to estimate the volume ratio ω _k of water in each of the division target regions k obtained by dividing the concrete structure 200.

The water estimation device 102 outputs the volume ratio ω _{k of} water obtained by the above method to the output unit 16. At this time, it is preferable to divide and display the inspection target area 202 of the concrete structure 200 to be investigated into the division target area _k and visualize and display the volume ratio ω _k of each water of the division target area k. It is. For example, the volume ratio omega _k of water or the like to be displayed by changing the color in the range of 0% to 100%, preferably by the user is displayed in a manner easily grasp the volume ratio omega _k of water from the visual It is.

Specifically, the moisture estimation device 102 estimates the moisture of the concrete structure according to the flowchart shown in FIG. 7. In step S10, the inspection target area 202 and the peripheral area 204 are set in the concrete structure 200, and the inspection target area 202 is divided to set a division target area k. In step S12, the position i of the neutron beam source 104 and the position j of the neutron detector 106 are determined using parameters in the case where the volume ratio of concrete in the division target area k is 100%, with each division target area k as the reflection point A. The contribution rci _{, j, k} is calculated for each combination of At this time, the parameters used for the calculation are determined based on the element density composition of the concrete constituting the concrete structure 200 to be evaluated. In step S14, the position i of the neutron beam source 104 and the position j of the neutron detector 106 are determined using parameters in the case where the volume ratio of water in the division target area k is 100%, with each division target area k as the reflection point A. The contribution r _{w i, j, k} is calculated for each combination of In step S16, the response D _{i, j} is measured for each combination of the position i of the neutron beam source 104 and the position j of the neutron detector 106. In step S18, the simultaneous equations of equation (8) represented by the contribution rc _{i, j, k} and the contribution r _{w i, j, k} analyzed in steps S12 and S14 and the response D _{i, j} measured in step S16 are used. Based on the above, the volume ratio ω _k of water in each of the division target regions _k is estimated by the least squares method. In step S20, the volume ratio ω _{k of} water obtained in step S18 is visualized and displayed.

In addition, the type (concrete elemental density composition), shape and size of concrete structure 200 and the volume ratio ω _k of water of division target area k obtained by dividing inspection target area 202 of concrete structure 200 in advance are set. It is also preferable to analyze the response D _{i, j} at the time of making a database. The database may be stored in the storage unit 12 of the water estimation device 102. Thus, the concrete structure can be obtained by comparing the actually measured response _{Di, j} with the installed neutron beam source 104 and neutron detector 106 and the analyzed response _{Di, j} registered in the database. The distribution of water within 200 can be estimated.

  In constructing the database, the element density composition of the concrete structure 200 to be inspected and the content of the bound water are previously investigated and made into a database, and the element density composition of the plurality of concrete structures and the content of the bound water are previously It is possible to investigate and create a database, and to predict and store elemental density composition and content of bound water from a design document of a concrete structure.

  Further, as is clear from the above description, in the water estimation method in the present embodiment, the distribution of water in the concrete structure 200 can be estimated without using a tracer. For this reason, it is possible to apply to the existing concrete structure to which the tracer is not added. In the present embodiment, the neutron beam source 104 and the neutron detector 106 are arranged on the same surface side of the concrete structure 200 to be investigated, but from one direction of the concrete structure It is not necessary to be on the same surface side as far as it is possible to estimate the presence of water. In addition, the one direction of the concrete structure 200 means from one side when the space around the concrete structure 200 is divided into two or more.

  Reference Signs List 10 processing unit, 12 storage unit, 14 input unit, 16 output unit, 18 interface unit, 20 neutron source, 22, 24, 26 shielding wall, 100 moisture estimation system, 102 moisture estimation device, 104 neutron beam source, 106 neutron Detector, 200 concrete structure, 202 inspection area, 204 peripheral area.

Claims (10)

Under the condition of the element density composition of the concrete and the content of bound water, the neutron emitted from the radiation source based on the relationship between the position of the neutron radiation source and the position of the measurement point is the survey target composed of the concrete A first step of modeling a response measured at the measurement point through a concrete structure and analyzing it by a radiation transport calculation code including a Monte Carlo method and an SN method;
A second step of measuring a response when neutrons emitted from the radiation source are measured at the measurement point through the concrete structure to be investigated;
A concrete structure using neutrons, comprising: a third step of estimating the presence of water in the concrete structure to be investigated using the measured response and the analyzed response. Moisture estimation method. A method of estimating water content of a concrete structure using neutrons according to claim 1, wherein
The third step refers to a database storing the analyzed response analyzed for each type of concrete, which is a combination of a plurality of the element density compositions and the content of the binding water in the first step. Estimate the presence of moisture in the concrete structure to be investigated using the measured response and the analyzed response to the type of concrete constituting the concrete structure to be investigated Method of estimating moisture of concrete structure using neutrons characterized by A method of estimating water content of a concrete structure using neutrons according to claim 1 or 2,
The first step is
Each of the concrete structures to be surveyed is modeled by setting the inspection target area and the surrounding area,
The inspection target area is divided into m division target areas k (m is an integer of 2 or more, k = 1,..., M), and the positions i of the plurality of radiation sources (i is an integer of 2 or more) And a contribution ri _{, j, k} from each of the division target regions k for each combination of positions j (j is an integer of 2 or more) of the plurality of measurement points,
The analyzed response R _{i, j} when neutrons emitted from the position i of the radiation source are measured at the position j of the measurement point through the concrete structure to be investigated

(Where Ar _{i, j} is the response from the surrounding area when neutrons emitted from the position i of the radiation source are measured at the position j of the measurement point through the concrete structure to be investigated) Contribution of
The moisture estimation method of the concrete structure characterized by calculating by The method of estimating moisture of a concrete structure according to claim 3, wherein
The first step is
For each combination of position i of the radiation source and position j of the measurement point, contributions rc _{i, j, k} when the concrete is present at a volume ratio of 100% in the division target area _k, and the division target area The contribution r _{w i, j, k} when the water exists at a volume ratio of 100% is obtained in _k ,
The second step is
For each combination of position i of the source and position j of the measurement point, the response D when neutrons emitted from the source are measured at the measurement point via the concrete structure to be investigated Measure _{i, j} ,
The third step is

(Where S is the intensity of the radiation source)
A method of estimating water content in a concrete structure, comprising: estimating a volume ratio ω _k of water in the division target area k using the relationship of A method of estimating moisture of a concrete structure according to claim 4, wherein
A moisture estimation method for a concrete structure, comprising: estimating a volume fraction ω _k of moisture in the division target region k which minimizes the error of the equation (2). It is the moisture estimation method of the concrete structure of any one of Claims 1-5, Comprising:
A method of estimating moisture of a concrete structure, comprising the fourth step of visualizing the presence of moisture in the concrete structure to be surveyed estimated in the third step. It is a moisture estimation method of the concrete structure according to any one of claims 1 to 6,
The method of estimating moisture of a concrete structure according to claim 1, wherein the radiation source used in the second step has a structure in which a neutron shielding means covers a region other than a region facing the concrete structure to be investigated. It is a moisture estimation method of the concrete structure according to any one of claims 1 to 7,
In the second step, the water source and the measurement point are sequentially moved on the surface of the concrete structure to be surveyed to measure the measured response, and the water structure of the concrete structure is estimated. Method. Under the condition of the element density composition of the concrete and the content of bound water, the neutron emitted from the radiation source based on the relationship between the position of the neutron radiation source and the position of the measurement point is the survey target composed of the concrete Storage means for storing, as a database, the results of modeling and analyzing responses when measured at the measurement points via a concrete structure;
An actual response measurement means for measuring a response when neutrons emitted from the radiation source are measured at the measurement point via a concrete structure to be investigated;
A concrete structure using neutrons, comprising: water estimation means for estimating the presence of water in the concrete structure to be investigated using the measured response and the analyzed response. Moisture estimation system. It is a moisture estimation system of the concrete structure according to claim 9, which is
A moisture estimation system for a concrete structure, further comprising display means for visualizing and displaying the presence of moisture in the concrete structure to be surveyed estimated by the moisture estimation means.

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