JP2017009371A - Moisture estimation method of concrete structure and moisture estimation system of concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a distribution of moisture in a concrete structure which is an estimation object.SOLUTION: When a neutron emitted from a neutron beam source 104 with a content of the chemical element density composition of the concrete and bound water as a condition based on a relation between the position of a neutron beam source 104 and the position of a neutron beam detector 106 is measured in the neutron detector 106 via a concrete structure 200, the response is modeled and analyzed by a radiation transportation calculation code including the Monte Carlo method and the SN method, and when the neutron emitted from the neutron beam source 104 is measured in the neutron detector 106 via the concrete structure 200, the response is actually measured, and the existence of the moisture in the concrete structure 200 is estimated using the actually measured response and the analyzed response.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a moisture estimation method for a concrete structure and a moisture estimation system for a concrete structure.

  There is a possibility that a defect such as a jumper or a crack may occur in the concrete structure, and there is a possibility that water accumulates there and corrodes or weakens the reinforcing bars and the structural material constituting the concrete structure. Therefore, realization of a technique capable of estimating the moisture distribution in the concrete structure is desired.

  For example, a neutron beam source and a panel-type high-sensitivity neutron detector are arranged so as to sandwich the concrete structure, and the concrete structure is detected by detecting the neutron emitted from the neutron beam source through the concrete structure. A technique for detecting a deficiency in a cell is disclosed (Patent Document 1).

  Also, injecting cement containing a hardener as a hardener and adding tracers such as boron compounds into the back of the cement, irradiating the neutron from the cement surface, measuring the number of thermal neutrons rescued by the tracer, and injecting the cement A technique for detecting the degree is disclosed (Patent Document 2).

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

  By the way, there are two types of neutron sources that generate neutrons to be irradiated: a method using a nuclear reactor and a method using an accelerator. In transmission-type neutron beam detection, it is necessary to place an object to be measured between a neutron source and a sensor. When a concrete structure existing mainly outdoors is used as a measurement object, movement of the neutron source or sensor is not possible. It may be impossible or difficult, and depending on the shape and thickness of the measurement object, it may be impossible to place the object on the back side. In addition, the system becomes larger in principle in relation to the arrangement of the neutron source and the detector. Recently, some research institutions have developed mobile accelerators that can be used outdoors.

  In addition, a technique using a boron compound or the like as a tracer cannot be applied in principle to an existing concrete structure to which no tracer is added.

  The present invention provides a moisture estimation method for a concrete structure and a moisture estimation system for a concrete structure that detect moisture accumulated in junkers, cracks, and the like in the concrete structure.

  The method for estimating the moisture content of a concrete structure using neutrons according to claim 1 of the present invention is based on the relationship between the position of a neutron source and the position of a measurement point on condition that the element density composition of concrete and the content of bound water are the conditions. Radiation including the Monte Carlo method and SN method by modeling the response when neutrons radiated from the radiation source are measured at the measurement point through the concrete structure which is the object of investigation composed of the concrete A first step of analyzing by a transport calculation code; a second step of actually measuring a response when the neutron emitted from the radiation source is measured at the measurement point through the concrete structure to be investigated; First, the presence of moisture in the concrete structure to be investigated is estimated using the measured response and the analyzed response. Characterized in that it comprises of the steps.

  Here, the third step is a database in which the analyzed response is analyzed for each type of concrete which is a combination of a plurality of the element density compositions and the combined water content in the first step. The presence of moisture in the concrete structure being investigated using the measured response and the analyzed response to the type of concrete comprising the concrete structure being investigated Is preferably estimated.

（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。 In the first step, an inspection target region and a peripheral region are respectively set and modeled on the concrete structure to be investigated, and the inspection target region is divided into m divided target regions k (m is 2 or more). The mesh is divided into integers, k = 1,..., M), and a plurality of the source positions i (i is an integer of 2 or more) and a plurality of measurement point positions j (j is an integer of 2 or more). The contributions r _{i, j, k} from each of the division target regions k for each combination are obtained, and the measurement points are obtained through the concrete structure that is the object of investigation by neutrons emitted from the position i of the radiation source. The analyzed response R _{i, j} when measured at position j of

(However, Ar _{i, j} is a response from the surrounding region when neutrons radiated 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 (contribution).

（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 exists in the division target region k at a volume ratio of 100% _{, j, k} and a contribution rw _{i, j, k} when the water is present in the division target region k at a volume ratio of 100% are obtained, and the second step includes the position i of the radiation source and the measurement For each combination of point positions j, a response D _{i, j} when neutrons radiated from the radiation source are measured at the measurement point via the concrete structure to be investigated is measured, The third step is

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

In addition, it is preferable to estimate the water volume ratio ω _k in the division target region k that minimizes the error in the mathematical formula (2).

  Moreover, it is preferable to provide the 4th step which visualizes the presence of the water | moisture content in the concrete structure which is the said investigation object estimated in the said 3rd step.

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

  In the second step, it is preferable that the measured response is measured by sequentially moving the radiation source and the measurement point on the surface of the concrete structure to be investigated.

  A concrete structure moisture estimation system using neutrons according to claim 9 of the present invention is a relationship between the position of a neutron source and the position of a measurement point on condition that the element density composition of concrete and the content of bound water are the conditions. The result of modeling and analyzing the response when neutrons radiated from the radiation source are measured at the measurement point through the concrete structure to be investigated constituted by the concrete is stored as a database. Storage means; actual response measurement means for actually measuring a 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 a moisture estimation means for estimating the presence of moisture in the concrete structure that is the object of investigation using the measured response. To.

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

  According to the method for estimating the moisture content of a concrete structure using neutrons according to claim 1 of the present invention, the position of the neutron source and the position of the measurement point are obtained on condition that the element density composition of concrete and the content of bound water. Based on the relationship, the response when the neutron radiated from the radiation source is measured at the measurement point through the concrete structure to be investigated constituted by the concrete is modeled, and the Monte Carlo method and the SN method are performed. A first step of analyzing by a radiation transport calculation code including a second step of measuring a response when neutrons radiated from the radiation source are measured at the measurement point via 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 is possible to estimate the presence of moisture from one direction of the concrete structure, and no tracer is required, and application to an existing concrete structure is possible.

  In the third step, the database storing the analyzed response analyzed for each type of concrete, which is a combination of the plurality of element density compositions and the combined water content in the first step. Referring to the measured response and the analyzed response to the type of concrete that constitutes the concrete structure that is the investigation target, the presence of moisture in the concrete structure that is the investigation target. By estimating, it is possible to estimate the presence of moisture in the concrete structure corresponding to the actually measured response based on the analyzed response registered in advance as the database.

In the first step, an inspection target region and a peripheral region are respectively set and modeled on the concrete structure to be investigated, and the inspection target region is divided into m divided target regions k (m is 2 or more). The mesh is divided into integers, k = 1,..., M), and a plurality of the source positions i (i is an integer of 2 or more) and a plurality of measurement point positions j (j is an integer of 2 or more). The contributions r _{i, j, k} from each of the division target regions k for each combination are obtained, and the measurement points are obtained through the concrete structure that is the object of investigation by neutrons emitted from the position i of the radiation source. By determining the analyzed response R _{i, j} when measured at the position j of the following equation (1), the volume ratio of moisture in the division target region k obtained by dividing the concrete structure can be obtained. .

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 exists in the division target region k at a volume ratio of 100% _{, j, k} and a contribution rw _{i, j, k} when the water is present in the division target region k at a volume ratio of 100% are obtained, and the second step includes the position i of the radiation source and the measurement point For each of the combinations of positions j, a response D _{i, j} when neutrons radiated from the radiation source are measured at the measurement point via the concrete structure to be investigated is measured, and the third The step of estimating the volume ratio ω _k of the moisture in the division target region k using the relationship of the formula (2), to the contribution rc _{i, j, k} and the contribution rw _{i, j, k} 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 the moisture in the division target region k that minimizes the error of the mathematical formula (2), the above-mentioned simultaneous equations derived from the mathematical formula (2) are not solved, and Based on the contribution rc _{i, j, k} and the contribution rw _{i, j, k} , the volume ratio ω _k of water in the division target region k can be estimated.

  Moreover, it is easy to grasp | ascertain the estimated moisture distribution by a user's vision by providing the 4th step which visualizes the presence of the water | moisture content in the concrete structure which is the investigation object estimated in the said 3rd step. It can be displayed in a manner.

  Moreover, the said radiation source used in the said 2nd step has a structure which covered the area | region other than the area | region which faces the said concrete structure to be investigated with a neutron shielding means, From the neutron radiation source to the said concrete structure It is possible to reduce neutrons that reach the neutron detector 106 without being incident / scattered.

  In the second step, it is preferable that the measured response is measured by sequentially moving the radiation source and the measurement point on the surface of the concrete structure to be investigated.

  A concrete structure moisture estimation system using neutrons according to claim 9 of the present invention is a relationship between the position of a neutron source and the position of a measurement point on condition that the element density composition of concrete and the content of bound water are the conditions. The result of modeling and analyzing the response when neutrons radiated from the radiation source are measured at the measurement point through the concrete structure to be investigated constituted by the concrete is stored as a database. Storage means; actual response measurement means for actually measuring a 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 a moisture estimation means for estimating the presence of moisture in the concrete structure to be investigated using the response thus obtained. , The distribution of moisture in the evaluation in the concrete structure is the object can be estimated accurately. In addition, it is possible to estimate the presence of moisture from one direction of the concrete structure, and no tracer is required, and application to an existing concrete structure is possible.

  Here, by further comprising display means for visualizing and displaying the presence of moisture in the concrete structure that is the investigation object estimated by the moisture estimation means, the estimated moisture distribution is grasped by the user's vision. Can be displayed in an easy-to-use manner.

It is a figure which shows the structure of the moisture estimation system in embodiment of this invention. It is a figure which shows the structure of the moisture 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 neutron scattering model 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.

  A concrete structure moisture estimation system 100 using neutrons according to an embodiment of the present invention includes a moisture estimation device 102, a neutron source 104, and a neutron detector 106 as shown in FIG. 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.

  As shown in FIG. 2, the moisture estimation apparatus 102 includes a processing unit 10, a storage unit 12, an input unit 14, an output unit 16, and an interface unit 18 that are basic configurations of a general computer.

  The processing unit 10 includes a calculation unit such as a CPU, and realizes a moisture estimation process in the concrete structure 200 performed in the moisture estimation device 102 by executing a moisture estimation program stored in the storage unit 12. The storage unit 12 includes a storage device such as a semiconductor memory or a hard disk connected 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 includes an input device such as a keyboard and a mouse. The input unit 14 is used to input various parameters used by the moisture estimation device 102. The output unit 16 includes 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 in the moisture estimation device 102. The output unit 16 presents information related to processing in the moisture estimation apparatus 102 to the user. The interface unit 18 includes an analog / digital converter and the like. The interface unit 18 is used to import data indicating the dose of the neutron beam detected by the neutron detector 106 into the moisture estimation device 102.

The neutron beam source 104 is configured to include a neutron generation source such as a neutron generation tube or an RI beam source such as ²⁵² Cf. The neutron 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 direction other than the direction facing the concrete structure 200 that is the object to be investigated, that is, the area other than the area facing the concrete structure 200. By shielding the neutron generation source 20, when the neutron beam source 104 is installed on the surface of the concrete structure 200 to be investigated, neutrons and γ rays do not enter and scatter into the concrete structure 200, and a neutron detector Direct arrival of neutrons and γ rays at 106 can be suppressed.

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

  The neutron detector 106 detects neutrons emitted from the neutron 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 detecting the neutron, the neutron detector 106 outputs the detected neutron to the moisture estimation apparatus 102 via the interface unit 18. When receiving the detection signal from the neutron detector 106, the processing unit 10 of the moisture estimation apparatus 102 counts the number of detected neutrons per unit time. Thereby, the dose rate (count rate) of a neutron beam is measured.

  In the moisture estimation system 100 according to the present embodiment, as shown in FIG. 4, neutrons emitted from the neutron source 104 are incident from one surface side of the concrete structure 200 and reflected from the concrete structure 200. Is detected by a neutron detector 106 provided on the same surface side to evaluate the moisture distribution in the concrete structure 200. For this reason, it becomes possible to evaluate the moisture distribution from the same surface side of the concrete structure 200, that is, from one direction. Fast neutrons generated from the neutron source 104 are reflected or scattered by the concrete structure 200, the jumper X or the like, and reach the neutron detector 106. At this time, if there is a “puddle” in which water is accumulated in the jumper X or the like, neutrons are decelerated by hydrogen in the water, and thermal neutrons are more easily formed than in the case where there is no “puddle”. The distribution of moisture in the concrete structure 200 is evaluated by paying attention to the difference in the nuclear reaction. According to the moisture estimation system 100, it is possible to estimate the moisture distribution from the surface of the concrete structure 200 to a depth of about the number average free path of neutrons.

  In the moisture estimation system 100, as shown in FIG. 5, the concrete structure 200 to be evaluated is divided into an inspection target region 202 and its peripheral region 204, and the moisture distribution in the inspection target region 202 is evaluated. At this time, the inspection target region 202 is divided into a plurality of (m: m is an integer of 2 or more) division target regions k (k is a region number: k = 1,..., M). The distribution of moisture in the concrete structure 200 is evaluated by estimating the moisture in the interior.

  In the example of FIG. 5, one surface (XY plane) of the concrete structure 200 is used as a measurement surface, and the inspection target region 202 of the measurement surface is divided into six regions, and 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 near the measurement surface is divided into division target regions k (7 ≦ k ≦ 12). . Of course, the number of divisions of the inspection target region 202 is not limited to this, and the number of divisions in the surface may be other than 6, and the number of layers in the depth direction may be other than 2.

In the moisture estimation system 100, the neutron 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 moisture distribution corresponding to the actually measured response is determined as the moisture distribution. Analysis is performed by the estimation device 102. That is, the actual response D _{i, j} and the analyzed response R _{i for} each combination of the position i of the division target region k where the neutron source 104 is arranged and the position j of the division target region k where the neutron detector 106 is arranged. _{, J} matches the moisture distribution.

For example, in the inspection target region 202 of FIG. 5, the neutron source 104 is arranged in the division target region of region number 7 and the neutron detectors 106 are sequentially arranged in the division target regions of region numbers 10, 11, and 12, respectively. The actual responses D _7,10 , D _7,11 , D _{7,12 of the case} are measured. Further, the actual response D _8,10 when the neutron radiation source 104 is arranged in the division target area of the area number 8 and the neutron detectors 106 are arranged in order in the division target areas of the area numbers 10, 11, 12 respectively. , D _8,11 , D _8,12 are measured. In addition, the neutron radiation source 104 is arranged in the division target area of the area number 9, and the actual responses D _9,10 when the neutron detectors 106 are arranged in order in the division target areas of the area numbers 10, 11, 12 respectively. , D _9,11 , D _9,12 are measured. Further, the actual response is measured by switching the position of the neutron source 104 and the position of the neutron detector 106. That is, the actual response D _10,7 when the neutron source 104 is arranged in the division target area of the area number 10 and the neutron detectors 106 are arranged in order in the division target areas of the area numbers _{7,8,9. , D} 10,8, to measure the _{D 10,9.} Further, the actual response D _11,7 when the neutron source 104 is arranged in the division target area of the area number 11 and the neutron detectors 106 are sequentially arranged in the division target areas of the area numbers 7, 8, 9 respectively. , D _11,8 and D _11,9 are measured. Further, the actual response D _12,7 when the neutron radiation source 104 is arranged in the division target region of the region number 12 and the neutron detectors 106 are sequentially arranged in the division target regions of the region numbers 7, 8, 9 respectively. _{, D} 12,8, to measure the _{D 12,9.}

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

  On the other hand, the moisture estimation apparatus 102 performs analysis based on the radiation transport calculation code. The moisture estimation apparatus 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 the Monte Carlo method or TORT based on the SN method.

  For example, it is assumed that one neutron is generated every second from the position i of the neutron source 104, and the response (count rate and dose rate) obtained at the position j of the neutron detector 106 is from each region of the division target region k. The contribution needs to be evaluated for each region. In addition, it is necessary to consider the influence from the peripheral region 204.

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} when the position i of the neutron beam source 104 and the position j of the neutron detector 106 are set is expressed by Equation (3).

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

  As shown in FIG. 6, the behavior of neutrons incident on the concrete structure 200 is caused by non-collision transmission and collision of fast neutron attenuation from the neutron source 104 to the reflection point A and scattering at the reflection point A. It is expressed by scattering.

The non-collisional 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 the neutron, S is the initial intensity of the neutron, P1 is the distance from the neutron source 104 to the reflection point A, and σ _T (E) is the total cross-sectional area of the neutron of energy E.

The initial 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 the energy changes from the incident energy E to the reflected energy E ′ and changes from the incident angle θ1 to the reflected angle θ2.

The flux Φ _B (E ′) in the neutron detector 106 can be expressed by Equation (6). Here, B (E ′) is a build-up coefficient indicating the contribution of scattering components in a path from a neutron having energy E ′ to the neutron detector 106 from the reflection point A, and P2 is a distance from the reflection point A to the neutron detector 106. The distance, σ _T (E ′), is the total cross section of the neutron with energy E ′.

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

Here, the total cross-sectional areas σ _T (E) and σ _T (E ′) in the formulas (4) and (6) are determined based on the element density composition of the concrete constituting the concrete structure 200. Further, the differential scattering cross section σ _S (E, E ′, θ1, θ2) at the reflection point A is determined based on the atomic density of water accumulated in the junkers and the like in addition to the element density composition of the concrete structure 200. . Approximately, the differential scattering cross section and the water differential scattering cross section of the concrete constituting the concrete structure 200 can be determined from the volume ratio (volume ratio) at each reflection point A. That is, the differential scattering cross section of the target region containing a considerable amount of water other than the concrete constituting the concrete structure 200 is the differential scattering cross section of the concrete constituting the concrete structure 200 and the differential scattering cross section of water. Is multiplied by the respective volume ratios and added.

Therefore, assuming that the reflection point A is the concrete constituting the concrete structure 200 (concrete volume ratio 100%), the differential scattering cross section σ _SC at the reflection point A determined based on the element density composition of the concrete structure 200 The contribution r _{i, j, k} when (E, E ′, θ1, θ2) is applied is determined as the contribution rc _{i, j, k} . Further, assuming that the reflection point A is water (water volume ratio 100%), the contribution r _i, when applying the differential scattering cross section σ _SW (E, E ′, θ1, θ2) at the reflection point A of water _. Find _{j, k} as contributions rw _{i, j, k} . Then, when the volume ratio ω _k of the water contained in the division target region k is the amount of water, the response measured by the neutron detector 106 is expressed by Expression (7).

When Formula (7) is expanded, Formula (8) is obtained.

By moving the neutron beam source 104 and the neutron detector 106 sequentially to the position i and the position j in the concrete structure 200 to be evaluated and substituting the measured responses D _{i, j} into the equation (8), the unknowns are obtained. A simultaneous equation with a water volume ratio ω _k is obtained. Therefore, by solving this simultaneous equation, the water volume ratio ω _k in the division target region k, that is, the moisture distribution in each of the division target regions k obtained by dividing the inspection target region 202 of the concrete structure 200 can be obtained.

However, the calculation for calculating the contribution rc _{i, j, k} , the contribution rw _{i, j, k} and the contribution Ar _{i, j} from the peripheral region 204 includes a calculation error, and the measured response D _{i, j} Also includes uncertainties such as statistical errors. Therefore, the mathematical formula (8) does not hold strictly. Therefore, if the volume ratio ω _{k of} water that minimizes the error in Expression (8) is obtained, the amount of water in the division target region k of the concrete structure 200 can be estimated.

For example, the distribution of moisture in the concrete structure 200 can be estimated by applying the least square method. With respect to Equation (8), the left side constant term C _{i, j} and the residual R of the calculated value on the right side are defined as Equation (9) as an objective function based on the least square method.

The steepest descent method is applied to minimize this objective function. As a constraint condition, a condition that the volume ratio ω _k of water is 0 or more is set. In general, it is impossible to solve the problem given by Equation (9) by a closed-type operation, and it is necessary to perform some kind of repeated calculation. Therefore, an algorithm is used to obtain a vector sequence ω _k ⁽⁰⁾ , ω _k ⁽¹⁾ ,..., Ω _k ⁽ⁿ⁾ such that the numerical formula (10) is converged to the minimum value of the objective function. .

This algorithm generally consists of the following three steps.
(1) An appropriate initial point ω _k ⁽⁰⁾ of a volume ratio ω _k of water is given, and a parameter n representing the number of repetitions is set to 0.
(2) It is determined whether or not the volume ratio ω _k ^{(n) of} water obtained for the current parameter n is a solution of Equation (9). If the water volume ratio ω _k ⁽ⁿ⁾ satisfies the determination condition, the calculation is terminated and the water volume ratio ω _k ⁽ⁿ⁾ is taken as a solution. If the conditions are not met, proceed to the next step.
(3) A new water volume ratio ω _k ^{(n + 1)} that reduces the objective function f (ω) is obtained based on the calculation result for the parameter n. 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 iteration, 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 can be obtained by Expression (11).

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

In this manner, 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 Formula (8) is obtained by applying the least square method. Thereby, the volume ratio ω _k of water in each of the division target regions k obtained by dividing the concrete structure 200 can be estimated.

The moisture estimation device 102 outputs the water volume ratio ω _k obtained by the above method to the output unit 16. At this time, it is preferable that the inspection target area 202 of the concrete structure 200 to be investigated is divided into the division target areas k and displayed, and the volume ratio ω _k of each water in the division target area _k is visualized and displayed. 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 apparatus 102 estimates the moisture of the concrete structure along the flowchart shown in FIG. 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 source 104 and the position j of the neutron detector 106 are set using the parameters when each division target region k is the reflection point A and the volume ratio of the concrete in the division target region k is 100%. The contribution rc _{i, j, k} is calculated for each combination. At this time, 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 source 104 and the position j of the neutron detector 106 are set using parameters when each division target region k is a reflection point A and the volume ratio of water in the division target region k is 100%. The contribution rw _{i, j, k} is calculated for each combination. In step S16, the response D _{i, j} is measured for each combination of the position i of the neutron 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 rw _{i, j, k} analyzed in steps S12 and S14 and the response D _{i, j} measured in step S16 are changed. Based on this, the water volume ratio ω _k in each of the division target regions _k is estimated by the least square method. In step S20, the water volume ratio ω _k obtained in step S18 is visualized and displayed.

The concrete type (concrete element density composition), shape and size of the concrete structure 200, and the water volume ratio ω _k of the division target region k obtained by dividing the inspection target region 202 of the concrete structure 200 in advance are set. It is also preferable to analyze the responses D _{i, j} and create a database. The database may be stored in the storage unit 12 of the moisture estimation apparatus 102. Thus, actually neutron source 104 and the neutron detector 106 installed to the measured responses D _{i, j} and the response D _i database is analyzed is registered _by comparing the _j, concrete structure The distribution of moisture in 200 can be estimated.

  In constructing the database, the element density composition and the content of bound water of the concrete structure 200 to be inspected are preliminarily investigated and compiled into a database, and the element density composition and the content of bound water of a plurality of concrete structures are determined in advance. It is possible to search and create a database, and to predict the element density composition and the content of bound water from a concrete structure design document and create a database.

  Further, as is clear from the above description, in the moisture estimation method in the present embodiment, the moisture distribution in the concrete structure 200 can be estimated without using a tracer. Therefore, it can be applied to an existing concrete structure to which no tracer is added. Moreover, in this Embodiment, although the neutron beam source 104 and the neutron detector 106 showed the example arrange | positioned on the same surface side of the concrete structure 200 which is investigation object, from one direction of a concrete structure As long as it is possible to estimate the presence of water, they may not be on the same surface side. 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.

  DESCRIPTION OF SYMBOLS 10 Processing part, 12 Storage part, 14 Input part, 16 Output part, 18 Interface part, 20 Neutron generation source, 22, 24, 26 Shielding wall, 100 Moisture estimation system, 102 Moisture estimation apparatus, 104 Neutron source, 106 Neutron Detector, 200 concrete structure, 202 inspection object area, 204 peripheral area.

Claims (10)

Subject to the element density composition of concrete and the content of bound water, the neutron emitted from the source based on the relationship between the position of the neutron source and the position of the measurement point A first step of modeling a response when measured at the measurement point through a concrete structure and analyzing with a radiation transport calculation code including a Monte Carlo method and an SN method;
A second step of actually measuring a response when neutrons radiated from the radiation source are measured at the measurement point through the concrete structure to be investigated;
A concrete step using neutrons, comprising: a third step of estimating the presence of moisture in the concrete structure to be investigated using the measured response and the analyzed response. Moisture estimation method. It is the moisture estimation method of the concrete structure using the neutron of Claim 1, Comprising:
The third step refers to a database storing the analyzed responses analyzed for each type of concrete which is a combination of a plurality of the element density compositions and the combined water content in the first step. Then, using the measured response and the analyzed response for the type of concrete constituting the concrete structure to be investigated, the presence of moisture in the concrete structure to be examined is estimated. A method for estimating moisture in a concrete structure using neutrons. A method for estimating the moisture content of a concrete structure using neutrons according to claim 1 or 2,
The first step includes
Each of the concrete structures to be investigated is modeled by setting a region to be inspected and a surrounding region,
The inspection target area is mesh-divided into m division target areas k (m is an integer of 2 or more, k = 1,..., M), and a plurality of positions i of the radiation sources (i is an integer of 2 or more) And a contribution r _{i, j, k} from each of the division target areas k for each of a plurality of combinations of the positions j of the measurement points (j is an integer of 2 or more),
The analyzed response R _{i, j} when neutrons radiated 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

(However, Ar _{i, j} is a response from the surrounding region when neutrons radiated 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)
A method for estimating the moisture content of a concrete structure, characterized by: It is the moisture estimation method of the concrete structure of Claim 3, Comprising:
The first step includes
For each combination of the position i of the radiation source and the position j of the measurement point, the contribution rc _{i, j, k} when the concrete exists in the division target area k at a volume ratio of 100%, and the division target area a contribution rw _{i, j, k} when the water is present at a volume ratio of 100% is determined in _k ,
The second step includes
Response D when each of the combinations of the position i of the radiation source and the position j of the measurement point is measured at the measurement point by the neutron emitted from the radiation source through the concrete structure to be investigated Measure _{i and j} ,
The third step includes

(Where S is the intensity of the radiation source)
A moisture estimation method for a concrete structure, wherein the moisture volume ratio ω _k in the division target region _k is estimated using the relationship. It is the moisture estimation method of the concrete structure of Claim 4, Comprising:
A method for estimating moisture content of a concrete structure, wherein the moisture volume ratio ω _k in the division target region k that minimizes the error of the mathematical formula (2) is estimated. It is the moisture estimation method of the concrete structure of any one of Claims 1-5,
A method for estimating the moisture content of a concrete structure, comprising a fourth step of visualizing the presence of moisture in the concrete structure that is the object of investigation estimated in the third step. It is the moisture estimation method of the concrete structure of any one of Claims 1-6,
The method for estimating moisture of a concrete structure, wherein 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 neutron shielding means. It is the moisture estimation method of the concrete structure of any one of Claims 1-7,
The second step comprises measuring the measured response by sequentially moving the radiation source and the measurement point on the surface of the concrete structure to be investigated, and estimating the moisture content of the concrete structure Method. Subject to the element density composition of concrete and the content of bound water, the neutron emitted from the source based on the relationship between the position of the neutron source and the position of the measurement point Storage means for storing a result of modeling and analyzing a response when measured at the measurement point via a concrete structure as a database;
An actual response measuring means for actually measuring a response when the neutron emitted from the radiation source is measured at the measurement point via the concrete structure to be investigated;
A moisture estimation means for estimating the presence of moisture in the concrete structure to be investigated using the measured response and the analyzed response; Moisture estimation system. A moisture estimation system for a concrete structure according to claim 9,
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 investigated estimated by the moisture estimation means.

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