JP7382292B2 - How to measure the quality of structures - Google Patents

Description

The present invention relates to a method for measuring the quality of a structure.

Patent Document 1 discloses that the quality of a structure is managed by managing the compaction work of a structure constructed by leveling and compacting a cement-based mixture made by mixing soil, aggregate, and cement. A method is disclosed.

Japanese Patent Application Publication No. 2011-132761

The quality control method described in Patent Document 1 is performed based on compaction work on the surface of a structure, and the quality within the structure is treated as being uniform. However, when a structure is constructed with multiple thin and widely spread layers, it is difficult to make the quality of the cement mixture used to construct each layer uniform, so the quality of each layer actually varies. There is a possibility that In order to check the actual quality of each layer, it is conceivable to take a cylindrical core from the structure and measure the strength etc. of each layer after a predetermined period of time has elapsed and each layer has hardened. However, the aggregate mixed into the cement-based mixture, which is spread in layers, generally has a relatively large particle size, so some of the collected cores may collapse or the boundaries between each layer may be unclear. Therefore, it is difficult to cut the core and measure the quality such as strength of each layer.

The present invention aims to measure the quality of each layer of a structure constructed of multiple layers.

The present invention is a structure quality measurement method for measuring the quality of a structure constructed by curing a plurality of layers made of a cement-based kneaded material, in which a sample body containing a plurality of layers is removed from the structure. a step of emitting radiation to any one of the plurality of layers included in the sample body and determining the density or intensity of any one of the plurality of layers based on the amount of transmitted radiation; Equipped with

According to the present invention, it is possible to measure the quality of each layer of a structure constructed of multiple layers.

It is a longitudinal cross-sectional view of a dam. It is a front view of the dam seen from the upstream side. FIG. 2 is a sectional view showing a cross section of a structure that constitutes a dam. 1 is a schematic diagram of a measurement system for measuring the quality of a structure; FIG.

Hereinafter, a method for measuring quality of a structure according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case will be described in which the structure to be subjected to quality measurement is a structure 10 that constitutes a CSG dam 100 constructed by a CSG (Cemented Sand and Gravel) construction method.

First, the CSG dam 100 will be described with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal cross-sectional view (a cross-sectional view in the upstream and downstream direction) of the CSG dam 100, and FIG. 2 is a front view of the CSG dam 100 seen from the upstream side (a view of the CSG dam 100 seen from the left side in FIG. 1). be.

As shown in FIG. 1, the CSG dam 100 is a trapezoidal dam with a substantially trapezoidal cross section in the upstream and downstream directions, and is constructed by covering the surface of the dam body made of trapezoidal CSG with protective concrete. Ru. Further, as shown in FIG. 2, the CSG dam 100 is attached to rock masses 102 and 103 on the left and right sides, respectively. For convenience of explanation, the left-right direction shown in FIG. 1, that is, the direction in which the river flows, will be referred to as the upstream and downstream direction of the CSG dam 100.

CSG, which is the material for the dam body of CSG Dam 100, is cement that is manufactured by mixing water and cement with excavated soil material (locally generated material) made of gravel and rock blocks that can be easily obtained around the construction site. It is a system kneaded product, and contains coarse aggregate such as crushed stone and coarse gravel with a particle size of about 80 mm, which is larger than the maximum particle size (40 mm) of aggregate for general ready-mix concrete. Note that although excavated soil materials are sometimes treated to remove oversized materials or to be crushed, classification, particle size adjustment, and cleaning are generally not performed. In other words, CSG, which uses excavated soil as its main raw material, can be manufactured continuously using equipment that is simpler than equipment that manufactures concrete, and in constructing CSG Dam 100, it was possible to manufacture CSG using equipment that is simpler than equipment that manufactures concrete. Facilities such as aggregate production equipment required for construction become unnecessary. Note that cement includes Portland cement, mixed cement, special cement, etc., and for CSG and CSG construction methods, Portland cement and mixed cement (blast furnace cement, fly ash cement, etc.) are used. Particularly preferred are moderate heat Portland cement, blast furnace cement (class B), Portland cement mixed with fly ash, and moderate heat Portland cement mixed with fly ash cement.

The CSG dam 100 is constructed by stacking structures 10 for one lift, which are formed by pouring CSG (cement-based mixture), from bottom to top. The height of each structure 10, that is, the lift height h, is approximately 75 cm to 100 cm.

1 and 2, a CSG dam 100 consisting of six structures 10 is simply shown. The higher the structure 10 is formed, the shorter the length in the upstream and downstream directions. Therefore, steps on the upstream side and the downstream side of the CSG dam 100 are formed on the upstream side and the downstream side.

Next, with reference to FIG. 3, a method of constructing each structure 10 will be described. FIG. 3 shows a cross section of the structure 10 under construction.

The structure 10 is constructed by a so-called thin layer spreading method in which CSG is spread thinly and widely, and as shown in FIG. , 13 are hardened.

Specifically, first, the CSG is transported to the construction site by a transport machine such as a dump truck, a conveyor, or a crane, and is compacted by being leveled by a leveling machine such as a bulldozer. is formed.

Next, CSG is conveyed by a conveying machine onto the top surface of the leveled first layer 11, and the conveyed CSG is leveled and compacted by a leveling machine, and the second intermediate layer 12 is formed. It is formed.

Further, CSG is conveyed by a conveying machine onto the top surface of the leveled second layer 12, and the conveyed CSG is leveled by a leveling machine and compacted, thereby forming the third layer 13 as the top layer. be done. The layers 11, 12, 13 are leveled prior to the final setting time of the cement mixed with the CSG of each layer. In addition, the completion time of setting is measured according to JIS A 1147:2019 "Testing method for setting time of concrete".

After the third layer 13 is formed, as shown in FIG. Layer 12 and third layer 13 are compacted. That is, at least the uppermost layer of the three layers 11, 12, and 13 making up the structure 10 is leveled by a leveling machine and then rolled and compacted by a compaction machine. Note that, similarly to the third layer 13, the first layer 11 and the second layer 12 may be leveled by a leveling machine and then rolled and compacted by a compaction machine. Alternatively, the three layers 11, 12, 13 may be hardened by leveling with a leveling machine.

The height of each layer 11, 12, 13 formed in this way (a first height h1 which is the height of the first layer 11, a second height h2 which is the height of the second layer 12, and a third height The third height h3), which is the height of No. 13, is set to about 10 cm to 30 cm, respectively. However, the heights of the layers 11, 12, and 13 are not exactly the same, and differ depending on the leveling and compaction conditions.

The CSG dam 100 is constructed by repeating such operations and stacking the structures 10 in layers from bottom to top.

Next, with reference to FIG. 4, measurement of the quality of the structure 10 will be described. FIG. 4 is a simplified diagram of a measurement system 30 for measuring the quality of the structure 10.

As a method for measuring or estimating the quality of the structure 10 composed of layers of cement-based kneaded material as described above, CSG used when forming any of the layers 11, 12, 13 of the structure 10 is used. A method of creating a cylindrical specimen using a test machine and measuring the strength of the specimen, that is, the strength of CSG, and a method of measuring the strength of the specimen using a strength tester, and a method of using a vibrating roller 50 to roll the third layer 13, which is the top layer of the structure 10. There are ways to manage the actual work status.

However, these methods measure the quality of the structure 10 collectively and indirectly, and the quality of the structure 10 may vary among the layers 11, 12, and 13. It is not sufficient to measure quality.

To check the actual quality of each layer 11, 12, 13, after a predetermined period of time has elapsed and each layer 11, 12, 13 has hardened, take a cylindrical core (sample object) from the structure 10, and , 12, 13 may be measured. However, the excavated soil material mixed into the CSG forming each layer 11, 12, 13 includes materials with a relatively large particle size, such as crushed stone of about 80 mm. As a result, some of the cores that were collected crumble, making it difficult to measure their strength using a strength testing machine. In addition, since the boundaries between each layer 11, 12, and 13 are unclear, there is a high possibility that other layers will be included when cutting the core, making it difficult to accurately measure the quality of each layer 11, 12, and 13, such as strength. is difficult to measure.

Therefore, in this embodiment, the quality such as strength of each layer 11, 12, 13 can be measured using a measurement system 30 having the following configuration, without cutting the core (sample body) 20 including each layer 11, 12, 13. It is measured by

As shown in FIG. 4, the measurement system 30 includes an irradiation unit 31 that irradiates gamma rays (radiation) toward a core (sample body) 20 including each layer 11, 12, and 13, and a gamma ray (radiation) that has passed through the core 20. a measuring unit 32 that measures the gamma ray radiation dose), and a calculating unit 34 that calculates the attenuation rate of gamma rays based on the dose of gamma rays irradiated from the irradiation unit 31 and the transmitted dose of gamma rays measured by the measuring unit 32. It is an RI densitometer with

The calculation unit 34 includes a CPU (central processing unit) that performs calculation processing, a ROM (read-only memory) in which programs to be executed by the CPU are stored in advance, and information input from the irradiation unit 31 and the measurement unit 32. This is a computer that has a RAM (random access memory) that stores the results of calculations performed by the CPU. A display monitor (not shown) that displays the calculation results is connected to the calculation unit 34.

Further, the ROM of the calculation unit 34 contains a density calibration formula that shows the correlation between the attenuation rate of gamma rays and the density of the core 20, and an intensity calibration formula that shows the correlation between the density of the core 20 and the strength of the core 20. is saved in advance.

The density calibration formula is created, for example, based on the correlation between the density of a specimen having the same dimensions as the core 20 and the attenuation rate of gamma rays transmitted through this specimen. Specifically, a specimen having the same dimensions as the core 20 is created using CSG or a cement-based kneaded material equivalent to CSG, and the density is calculated from the volume and weight of the created specimen. Next, the measurement system 30 measures the attenuation rate of the gamma rays that have passed through the specimen. By measuring the density and the gamma ray attenuation rate for a plurality of specimens in this way, the correlation between the density and the gamma ray attenuation rate can be determined. It should be noted that at least one of the plurality of specimens is preferably formed of CSG used when forming any of the layers 11, 12, 13 of the structure 10, and the material actually used is By determining the correlation using , it is possible to improve the accuracy of density measurement by the measurement system 30. Further, when a case holding the core 20 is used when measuring the density etc. of the core 20 by the measurement system 30, the density calibration formula is created taking into account the attenuation rate of gamma rays due to the case.

The strength calibration formula is created based on the correlation between the density of the specimen obtained when creating the density calibration formula described above and the result of measuring the strength of this specimen using a strength testing machine. Therefore, the intensity can also be directly measured from the attenuation rate of gamma rays.

In this way, the calculation unit 34 calculates the attenuation rate of gamma rays, and also calculates the density and strength of the core 20 based on the attenuation rate of gamma rays. Note that, as the measurement result, both the density and the strength of the core 20 may be displayed, or only one of them may be displayed.

In addition to gamma rays, neutron beams may be irradiated from the irradiation section 31 toward the core 20. In this case, the calculation section 34 calculates the dose of the neutron beam irradiated from the irradiation section 31 and the measurement section 32. The attenuation rate of the neutron beam is calculated based on the transmitted dose of the neutron beam, and the moisture content of the core 20 is calculated based on the attenuation rate of the neutron beam.

The cylindrical core 20 is collected by a coring machine from the structure 10 after a sufficient curing period (for example, two months) has passed and strength has been developed. The length of the core 20 is set to include all the layers 11, 12, and 13 that make up the structure 10.

Next, a method for measuring the quality of the structure 10 using the measurement system 30 having the above configuration will be described.

The core 20 collected from the structure 10 is placed between an irradiation section 31 installed below and a measurement section 32 installed above so as to face the irradiation section 31, with the axial direction being horizontal. inserted into.

Then, radiation is emitted to each of the plurality of layers (first layer 11, second layer 12, third layer 13) in order from the first layer 11, and the quality of each layer is measured.

Specifically, an area that is likely to be the first layer 11, for example, an area that is 5 cm or more away from the end face of the core 20 and 5 cm or more away from the part that is presumed to be the boundary with the second layer 12. Gamma rays are emitted from the irradiation section 31, and the transmitted gamma rays are measured by the measurement section 32.

Then, based on the measurement results measured by the measurement unit 32, the calculation unit 34 calculates the attenuation rate of gamma rays, and calculates the density of the first layer 11 from the calculated attenuation rate of gamma rays using a density calibration formula. , the intensity of the first layer 11 is calculated from the calculated density of the first layer 11 using an intensity calibration formula.

The density and strength of the first layer 11 calculated in this way are displayed on the display monitor as the quality of the first layer 11. Note that in order to improve measurement accuracy, it is preferable to measure the quality of the first layer 11 at multiple points within a region that has a probability of being the first layer 11, and to display the average value as the measurement result. .

When the measurement on the first layer 11 is completed, the core 20 is moved horizontally along the axial direction, and the quality on the second layer 12 is measured.

Specifically, an area that is likely to be the second layer 12, for example, 5 cm or more away from the area that is estimated to be the boundary with the first layer 11, and from the area that is estimated to be the boundary with the third layer 13. Gamma rays are irradiated from the irradiation unit 31 to a region within a range that is 5 cm or more away, and the transmitted gamma rays are measured by the measurement unit 32.

Then, the density and intensity are calculated by the calculation unit 34 in the same manner as the first layer 11, and the calculated density and intensity of the second layer 12 are displayed on the display monitor as the quality of the second layer 12.

When the measurement on the second layer 12 is completed, the quality on the third layer 13 is measured in the same way.

By measuring the quality of each layer 11, 12, and 13 without cutting the core (sample body) 20, which may collapse in this way, the overall quality of the structure 10 composed of layers of cement-based kneaded material can be determined. can be measured.

Furthermore, by measuring the quality of each structure 10, it is also possible to measure the quality of the entire CSG dam 100 constructed by stacking a plurality of structures 10.

According to the above embodiment, the following effects are achieved.

In the method for measuring quality of a structure described above, a core 20 including a plurality of layers 11, 12, 13 is taken from a structure 10, and gamma rays are emitted to each of the plurality of layers 11, 12, 13 included in the core 20. However, the density and strength of each of the plurality of layers 11, 12, 13 are determined based on the transmitted gamma ray dose.

Since gamma rays (radiation) are used to measure the quality of each layer 11, 12, and 13 included in the core 20, it is possible to There is no need to take any special treatment even for sample bodies that are likely to collapse even after hardening, such as the core 20 to be collected. Therefore, even if the core 20 is in a state where it easily collapses, the quality such as the density and strength of each of the plurality of layers 11, 12, 13 included in the core 20 can be easily determined.

In addition, since gamma rays (radiation) are used to measure the quality of each layer 11, 12, 13 included in the core 20, the core 20 is There is no need to separate each. Therefore, even if the boundaries between the layers 11, 12, 13 are difficult to discern due to leveling and compaction, the quality, such as the density and strength, of each of the multiple layers 11, 12, 13 included in the core 20 can be accurately determined. You can ask well.

Note that the following modifications are also within the scope of the present invention, and the configuration shown in the modification may be combined with the configuration described in the above embodiment, or the configurations described in the following different modifications may be combined. is also possible.

In the above embodiment, the cement-based kneaded material is CSG manufactured by mixing water and cement with excavated soil material (locally generated material) consisting of sand and gravel, rock blocks, etc. that are readily available around the construction site. Cement-based kneaded materials are not limited to this, but can be made using coarse aggregate such as crushed stone or coarse gravel with a particle size of about 80 mm, which is larger than the maximum particle size (40 mm) of aggregate for general ready-mixed concrete. Any cement-based mix used in a construction method that constructs multi-layer structures by the so-called thin layer spreading method, in which the cement-based mix is spread thinly and widely, such as the CSG method described above. For example, it may be a cement-based kneaded material used in the RCD (Roller Compacted Dam-Concrete) construction method or the RCC (Roller Compacted Concrete) construction method. It may also be a cement-based mixture used in ground improvement work or concrete work. In addition, cement that is not standardized by JIS is generally used in dam concrete, but cement here is defined in JIS A 0203 in the broad sense of the term. It refers to mineral powder that hardens by reacting with cement, and cementitious mixture refers to construction materials that contain cement.

Further, in the embodiment described above, the structure 10 is constructed of three layers. The structure 10 only needs to be constructed of a plurality of layers, and may be constructed of two layers or four or more layers. Further, the height h of the structure 10 is not limited to the range of 75 cm to 100 cm, and may be lower or higher than this. For example, the number of layers and the height h of the structure 10 may be made different between the lower structure 10 and the upper structure 10 that constitute the CSG dam 100. Further, each layer constituting the structure 10 is preferably leveled before the final setting time of the cement mixed in the CSG, but is layered after the final setting time of the cement mixed in the CSG. It may also be leveled.

Further, in the embodiment described above, the core 20 is collected from the structure 10 after a sufficient curing period has passed and strength has been developed. Instead, a test structure was created at a test construction site using the same CSG as structure 10 and under the same leveling and compaction conditions as structure 10, and a sufficient curing period had elapsed. After the strength has been developed, the core 20 may be collected from the test structure as a sample of the structure 10.

Further, in the embodiment described above, the cores 20 are collected from all the structures 10. Instead, when measuring the quality of a building constructed by stacking a relatively large number of structures 10, such as the CSG dam 100, for example, five structures are stacked at predetermined intervals. The core 20 may be collected every time the core 10 is constructed.

Further, in the embodiment described above, the CSG dam 100 is configured by the plurality of structures 10. What is constituted by the plurality of structures 10 is not limited to this, and may be an embankment body such as an erosion control dam or a seawall.

Further, in the embodiment described above, the structure 10 constitutes the CSG dam 100. The structure 10 is not limited to one that constitutes an embankment body such as a dam, but for example, if it has a structure constructed by stacking cement-based kneaded material in layers by a thin layer spreading method, It can be made up of any kind of building.

Although the embodiments of the present invention have been described above, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. do not have.

10...Structure (structure)
11, 12, 13...layer 20...core (sample body)
30...Measurement system 31...Irradiation section 32...Measurement section 34...Calculation section 50...Vibration roller (rolling machine)
100...CSG dam

Claims (4)

A method for measuring the quality of a structure that measures the quality of a structure constructed by curing a plurality of layers made of a cement-based kneaded material, the method comprising:
Collecting a sample body including a plurality of the layers from the structure;
emitting radiation to any one of the plurality of layers included in the sample body, and determining the density or intensity of any one of the plurality of layers based on the amount of transmitted radiation. ,
How to measure the quality of structures. The plurality of layers are each constructed by leveling the cement-based kneaded material,
A method for measuring quality of a structure according to claim 1. At least the top layer of the plurality of layers is leveled and then compacted by a compaction machine.
The method for measuring quality of a structure according to claim 2. The cement-based kneaded material is CSG containing excavated soil material, cement, and water.
A method for measuring quality of a structure according to any one of claims 1 to 3.

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