JP2014178281A - Method for analyzing grain size of soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce overall time for identifying the grain size of soil and equipment cost.SOLUTION: Soil is classified into a plurality of soil grain groups of which a range of grain diameter is defined, and a weight of each soil grain group is obtained. Then, based on imaging results of each soil grain group, the grain size of each soil grain group is identified. Based on the weight of each soil grain group and the grain size of each soil grain group, the grain size of the entire soil is identified.

Description

  The present invention relates to a soil particle size analysis method.

  The materials used in the construction are quality-controlled according to their use. One of the quality controls is the material particle size control. Patent Document 1 describes a technique in which a concrete aggregate is scattered and photographed on a measurement plate and the particle size distribution is measured by image analysis.

JP 2008-268051 A

  By the way, when using a soil material in construction work, a soil particle size analysis is usually performed by the “soil particle size test method” defined in JIS A 1204. However, in this “soil particle size test method”, after the sample is oven-dried for 24 hours, the test is carried out by sieving. Therefore, a test time of at least 2 days is required. Since 15 or more types of sieves having different openings are required, the test can be performed only in a well-equipped test room, and there is a problem that the equipment cost increases.

  Then, an object of this invention is to reduce the time required to specify the particle size of soil, and equipment cost.

  The present invention classifies the soil into each of a plurality of soil particle groups having a determined particle size range, and obtains the weight of each soil particle group, and the result of imaging each of the soil particle groups. Based on the partial particle size specifying step for specifying the particle size in each of the soil particle groups, the weight of each soil particle group determined by the classification step, and the particle size in each soil particle group specified by the partial particle size specifying step And a method for analyzing the particle size of soil, comprising a whole particle size specifying step of specifying the particle size of the entire soil.

  In addition, among the plurality of soil particle groups classified in the classification step, at least the soil particle group having the smallest particle size may include a drying step of drying before the partial particle size specifying step. Thereby, the possibility that the particle diameter is erroneously recognized due to the wet state can be reduced.

  Moreover, you may make it provide the display process displayed in the state which compared the particle size specified in the said whole particle size identification process, and the range of the particle size requested | required with respect to soil. This simplifies comparison with the required granularity.

  According to the present invention, it is possible to reduce the time required for specifying the grain size of the soil and the equipment cost.

It is a flowchart which shows the outline | summary of the particle size test of the soil by embodiment. It is a figure which shows the structure of a computer. It is a flowchart which shows the detailed procedure of the particle size test of the soil by an Example. It is a figure for demonstrating imaging | photography of a sample. It is a figure which shows an example of the result of a particle size test. It is a figure which shows an example of a particle size accumulation curve. It is a figure which shows an example of a histogram. It is a figure which shows the result of the particle size test by an Example, and the result of the particle size test by a comparative example. It is a figure which shows the particle size accumulation curve created based on the result of the particle size test by an Example, and the particle size accumulation curve created based on the result of the particle size test by a comparative example. It is a figure which shows the histogram created based on the result of the particle size test by an Example, and the histogram created based on the result of the particle size test by a comparative example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. First, an outline of a soil particle size test using the soil particle size analysis method according to the present embodiment will be described. FIG. 1 is a flowchart showing an outline of a soil particle size test according to the present embodiment. As shown in FIG. 1, this particle size test is roughly divided into a sampling process, a classification process, a sorting process, a drying process, a photographing process, a partial particle size specifying process, and an overall particle size specifying process.

  First, in the collection step, a wet soil is collected from the natural ground as a sample (step S1). Subsequently, in the classification step, the collected samples are classified by 2 to 4 types of sieves, and the weight of each classified sample is measured (step S2). Subsequently, in the sorting process, an amount necessary for the test is collected from each classified sample (step S3). Here, for the sample having the smallest particle size, the sample is dried using a microwave oven in the drying step (step S4). For other samples, the drying process is not performed. Subsequently, in the photographing process, each sampled part is photographed by the digital camera 20 (step S5).

  Subsequently, in the partial particle size specifying step, the particle size of each classified sample is specified by analyzing the captured image (step S6). This particle size refers to the distribution of soil particle size expressed as a percentage by weight. Subsequently, in the overall particle size specifying step, the particle sizes of the specified samples are integrated based on the weight ratio, and the particle size in the entire particle size range of the sample is specified (step S7). The partial particle size identification step and the overall particle size identification step are performed by the computer 10.

  FIG. 2 is a diagram illustrating the configuration of the computer 10. The computer 10 is a personal computer installed in a construction site office, for example. The computer 10 includes a control unit 11 having a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), a display unit 12 having a liquid crystal panel and its drive circuit, a touch panel, and operation buttons. An input unit 13 and a storage unit 14 that stores programs executed by the control unit 11 and various data used by the control unit 11 are provided. The storage unit 14 stores image analysis software for performing image analysis.

(Example)
Next, the soil particle size test according to the present embodiment will be specifically described with reference to examples. FIG. 3 is a flowchart showing a detailed procedure of the soil particle size test according to this embodiment. Here, the detailed procedure of the particle size test when a sample having a particle size distribution of 300 mm or less and a good particle size distribution is used will be described.

  First, an operator collects about 10 to 15 kg of soil from a natural ground as a sample (step S11). Subsequently, the operator classifies the sample collected in step S11 using a sieve having an aperture of 26.5 mm and a sieve having an aperture of 2 mm (step S12). Specifically, the operator first uses a sieve having an aperture of 26.5 mm, and collects the collected sample as a soil particle group having a particle size of 26.5 mm or more (hereinafter referred to as “first sample”). And a soil particle group having a particle size of less than 26.5 mm. Subsequently, the operator uses a sieve having an aperture of 2 mm, and further selects an earth particle group having passed through the sieve having an aperture of 26.5 mm, and further an earth particle group having a particle size of 2 mm or more and less than 26.5 mm (hereinafter referred to as “particle size”) , “Second sample”) and a soil particle group having a particle size of less than 2 mm (hereinafter referred to as “third sample”).

  For the first sample, the particle size test proceeds in the following procedure. First, the operator measures the total weight of the first sample with a measuring device such as a scale (step S13). Subsequently, the operator photographs the first sample with the digital camera 20 (step S14). FIG. 4 is a diagram for explaining photographing of a sample. For this photographing, in addition to the digital camera 20, a photographing stand 21 constituted by a white plate of 1 m × 1 m and a camera stand 22 that supports the digital camera 20 are used. The operator first fixes the digital camera 20 at a position where the entire photographing stand 21 can be photographed by the camera stand 22 and photographs the photographing stand 21 with the digital camera 20. Subsequently, the operator places a ruler on the photographing stand 21 and photographs the ruler with the digital camera 20. Subsequently, the operator scatters the first sample on the imaging table 21 and images this with the digital camera 20.

  Subsequently, the operator captures image data representing an image captured by the digital camera 20 into the computer 10 by connecting the digital camera 20 and the computer 10 by wire or wirelessly, for example. The control unit 11 executes the image analysis software by the operator's operation and performs the image analysis based on the image data acquired from the digital camera 20, thereby specifying the particle size of the first sample (step S15). This particle size is represented, for example, by the weight percentage of the passing material corresponding to the soil particle size of the first sample. The passing weight percentage is obtained by expressing the value obtained by dividing the weight of the soil particles having a particle size smaller than the target particle size by the total weight of the first sample, as a percentage. For example, as disclosed in Japanese Patent Application Laid-Open No. 2008-268051, the soil particle diameter is calculated by calculating the area of the photographed soil particle image after binarizing the image data. It is measured by finding the diameter of an equivalent circle with the area replaced with a perfect circle. Note that the image of the imaging table 21 and the ruler image captured in step S14 are used for calibration of image analysis (for example, correction of a threshold value for binarization processing or calibration of a reference scale).

  For the second sample, the particle size test proceeds in the following procedure. First, the operator measures the total weight of the second sample with a measuring device such as a scale (step S16). Subsequently, the worker dispenses an amount of about 100 to 200 g from the second sample by the quadrant defined by JIS (step S17). Subsequently, the operator takes an image of the collected second sample with the digital camera 20 (step S18). Here, as in step S14 described above, the second sample is imaged using the imaging table 21, the camera stand 22, and the digital camera 20 shown in FIG. However, the photographing table 21 only needs to have a size of about 15 cm in length × 20 cm in width, and may have a backlight having a transparent panel. At this time, the operator shoots the second sample by dividing it into an amount of about 10 to 20 g.

  Subsequently, the operator captures image data representing an image captured by the digital camera 20 into the computer 10 by connecting the digital camera 20 and the computer 10 by wire or wirelessly, for example. Similarly to step S15 described above, the control unit 11 executes the image analysis software by the operator's operation and performs image analysis based on the image data acquired from the digital camera 20, thereby reducing the particle size of the second sample. Specify (step S19).

  For the third sample, the particle size test proceeds in the following procedure. First, the operator measures the total weight of the third sample with a measuring device such as a scale (step S20). Subsequently, the worker dispenses an amount of about 5 to 20 g from the third sample by the quadrant defined by JIS (step S21). Subsequently, the worker heated and dried the sampled third sample with a microwave oven according to the “Method for testing the moisture content of soil using a microwave oven” defined by the Japan Geotechnical Society Standard (JGS 0122-2009). (Step 22). For example, when a 600 W microwave is used, the third sample is heated for about 10 minutes. Subsequently, the operator images the dried third sample using the imaging table 21, the camera stand 22, and the digital camera 20 shown in FIG. 4 similarly to step S18 described above (step S23). At this time, the operator performs photography by dividing the third sample for each amount of about 0.5 g.

  Subsequently, the operator captures image data representing an image captured by the digital camera 20 into the computer 10 by connecting the digital camera 20 and the computer 10 by wire or wirelessly, for example. Similarly to step S15 described above, the control unit 11 executes image analysis software by an operator's operation and performs image analysis based on image data acquired from the digital camera 20, thereby reducing the particle size of the third sample. Specify (step S24).

  Next, the control unit 11 integrates the particle size of the first sample, the particle size of the second sample, and the particle size of the third sample specified in steps S15, S19, and S24 based on the weight ratio, A particle size in the particle size range is specified (step S25). This particle size is represented, for example, by the weight percentage of the passing material corresponding to each soil particle diameter of the sample. The passing weight percentage is obtained by expressing the value obtained by dividing the weight of the soil particles having a particle diameter smaller than the target particle diameter by the total weight in percentage.

  Subsequently, the control unit 11 creates and outputs the result of the particle size test based on the particle size in the entire particle size range specified in step S25 (step S26). FIG. 5 is a diagram illustrating an example of the result of the particle size test. For example, the control unit 11 creates a particle size accumulation curve C1 based on the particle size in the entire particle size range, and causes the display unit 12 to display the created particle size accumulation curve C1 (display process). At this time, the control unit 11 causes the display unit 12 to display a reference range R, which is a range of particle sizes required for the earth material, together with the particle size accumulation curve C1. The reference range R is determined according to the use of the earth material, for example.

  For example, when the passing weight percentage corresponding to each particle size is a value as shown in FIG. 5, by taking the particle size on the logarithmic scale of the semilogarithmic graph and passing weight percentage on the arithmetic scale, FIG. A particle size accumulation curve C1 as shown is created. In the example illustrated in FIG. 6, the particle size accumulation curve C1 is within the reference range R. This means that the soil particle size meets the required particle size range for the soil material. Thus, by displaying the particle size accumulation curve C1 and the reference range R in a state of comparison, the operator can determine whether the soil particle size satisfies the particle size range required for the soil material. Can be easily determined. Further, the control unit 11 determines whether or not the particle size accumulation curve C1 is within the reference range R so that the operator can make this determination more easily, and the determination result is displayed on the display unit 12. You may let them.

  Moreover, the control part 11 calculates | requires a particle size composition from the particle size accumulation curve C1, produces a histogram based on this particle size composition, and may display the produced histogram on the display part 12. FIG. This particle size composition refers to the distribution of the soil particle size expressed by weight percentage for each particle size category determined according to the particle size, and is expressed, for example, by the weight percentage corresponding to each particle size category. This weight percentage is calculated | required by expressing the value which remove | divided the weight of the soil particle which belongs to each particle size division by the whole weight with a percentage. For example, when the weight percentage corresponding to each particle size classification is a value as shown in FIG. 5, a histogram as shown in FIG. 7 is created by taking the particle size on the horizontal axis and the weight percentage on the vertical axis. Is done.

また、曲率係数Ｕｃ’は、以下の式（２）によって求められる。

Further, the control unit 11 may calculate a value representing the characteristics of the particle size distribution from the particle size accumulation curve C1, and display the calculated value on the display unit 12. The values representing the characteristics of the particle size distribution include, for example, the maximum particle size Dmax shown in FIG. 5 and the 10% particle size D10, 30 which is the particle size when the passing weight percentage is 10%, 30%, 50% and 60%. % Particle size D30, 50% particle size D50 and 60% particle size D60, uniformity coefficient Uc, curvature coefficient Uc ′ are included. The uniformity coefficient Uc is obtained by the following equation (1).

Further, the curvature coefficient Uc ′ is obtained by the following equation (2).

  Items for quality control of embankment materials used for roads and river embankments may include maximum particle size and fine particle content (content of soil particles with a particle size of 0.075 mm or less). is there. Further, the quality control items of the ground improvement material may include a particle size range and a fine particle content (content of soil particles having a particle size of 0.075 mm or less). Therefore, by displaying information such as the particle size accumulation curve C1, the histogram, the maximum particle size Dmax and the like as described above, the operator can easily grasp information necessary for quality control.

  Next, an experiment conducted by the inventors of the present application in order to examine the accuracy of the soil particle size test according to the present embodiment will be described. In this experiment, as a comparative example, a particle size test using the “soil particle size test method” defined in JIS A 1204 was performed using the same sample as the soil particle size test according to this example. The results were compared. FIG. 8 is a diagram illustrating the result of the particle size test according to the present example and the result of the particle size test according to the comparative example. FIG. 9 is a diagram illustrating a particle size accumulation curve C1 created based on the result of the particle size test according to the present example and a particle size accumulation curve C2 created based on the result of the particle size test according to the comparative example. is there. FIG. 10 is a diagram illustrating a histogram created based on the result of the particle size test according to the present example and a histogram created based on the result of the particle size test according to the comparative example. 8 to 10, no significant difference was found between the results of the particle size test according to this example and the results of the particle size test according to the comparative example. According to this experiment, it was found that the soil particle size test according to this example had sufficient accuracy.

  As described above, in this embodiment, after classifying a sample, photographing and image analysis are performed for each classified sample. Normally, soil particles of various sizes are mixed in the soil, so even if, for example, a sample is taken without classification and image analysis is performed, the particle size range of the sample exceeds the measurable range. Therefore, there is a case where the image analysis cannot be performed or the accuracy is remarkably deteriorated even if the image analysis can be performed. However, according to the present embodiment, since the samples are classified and then shooting and image analysis are performed for each of the classified samples, the particle size of the samples having a particle size of 300 mm to 0.75 mm is determined by image analysis. Measurement can be realized.

  In addition, according to the present embodiment, for a sample having a particle size other than the smallest particle size (for example, a sample having a particle size of 26.5 mm or more and a sample having a particle size of 2 mm or more and less than 26.5 mm), the sample is dried. Since the particle size test is performed without doing so, the time required for the particle size test is shortened. Since these samples generally have a particle size that is large enough to allow water to drain naturally, there is no major problem in the particle size test even if they are not dried.

  In the present embodiment, a sample having the smallest particle size (for example, a sample having a particle size of less than 2 mm) is photographed after the soil particles are individually separated by drying the sample. When the sample with the smallest particle size is left in a wet state, a plurality of soil particles may stick together and the particle size may increase apparently, so that the particle size may be erroneously recognized in image analysis. However, according to this embodiment, since the sample with the smallest particle size is photographed after the sample is dried, the possibility that the particle size is erroneously recognized in the image analysis can be reduced.

  And since a microwave oven is used in this drying process, special equipments, such as a furnace drying apparatus, are not required, and the installation cost for performing the soil particle size test is reduced. Further, by not using such special equipment, the soil particle size test can be carried out in an office installed at a construction site, for example, instead of a well-equipped test room. In this case, since the frequency of performing the soil particle size test can be increased, the accuracy of quality control of the soil material can be increased.

(Modification)
The present invention is not limited to the above-described embodiment, and the following modifications are possible. Further, the following modifications may be combined with each other.
(Modification 1)
The size of the sieve opening described in the above-described embodiments is an example, and the size of the opening of the sieve may be selected according to the characteristics of the sample, for example.

(Modification 2)
In the above-described embodiment, the sample having the smallest particle size (for example, the sample having a particle size of less than 2 mm) is dried. However, drying of this sample is not essential. For example, depending on the particle size and moisture content of the sample, it is not necessary to dry the sample with the smallest particle size. Conversely, for a sample with a particle size other than the smallest particle size, the sample may be dried before imaging.

(Modification 3)
In the embodiment described above, information such as the particle size accumulation curve C1 shown in FIG. 6, the histogram shown in FIG. 7, the result of the soil particle size test shown in FIG. When a printer is connected to the computer, the computer 10 may print out the information on a medium by the printer and output the information.

(Modification 4)
The image analysis method is not limited to the method described in the embodiment, and other known methods can be employed.

DESCRIPTION OF SYMBOLS 10 Computer, 11 Control part, 12 Display part, 13 Input part, 14 Storage part, 20 Digital camera, 21 Shooting stand, 22 Camera stand.

Claims (3)

Classifying the soil into each of a plurality of soil particle groups having a determined particle size range, and determining the weight of each of the soil particle groups,
Based on the result of imaging each of the soil particle groups, a partial particle size specifying step for specifying the particle size in each of the soil particle groups;
A soil particle size comprising: a weight of each soil particle group determined by the classification step, and an overall particle size identification step that identifies the particle size of the entire soil based on the particle size in each soil particle group identified by the partial particle size identification step analysis method. The soil particle size according to claim 1, further comprising a drying step of drying the soil particle group having the smallest particle size among the plurality of soil particle groups classified in the classification step before the partial particle size specifying step. analysis method. The soil particle size analysis method according to claim 1, further comprising a display step of displaying the particle size specified in the overall particle size specifying step and the range of the particle size required for the soil.

Images