Compaction control method for crushed bentonite stone

Abstract

To provide a compaction control method for crushed bentonite stone which is capable of controlling a degree of compaction of crushed bentonite stone more efficiently and accurately than conventional methods.SOLUTION: A compaction control method for crushed bentonite stone comprises at least the steps of: placing a scattering type RI meter 1 on a compacted surface of a crushed bentonite stone to detect an amount of gamma rays; measuring the clearance between a bottom surface of the scattering type RI meter 1 and the compacted surface of the crushed bentonite stone; correcting a count rate ratio calculated from a gamma ray count rate of the scattering type RI meter 1 in accordance with the clearance to calculate a corrected count rate ratio; converting the corrected count rate ratio to a degree of compaction based on a calibration curve; and excluding the degree of compaction when the clearance is equal to or greater than a predetermined threshold value.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a method for controlling the compaction of crushed bentonite stone, which is capable of controlling the degree of compaction of crushed bentonite stone. [Background technology]

[0002] Conventionally, water-proofing works have been constructed at waste disposal sites to prevent the diffusion of pollutants, and in recent years, crushed bentonite stone has been used as a supplementary water-proofing material to further enhance the water-proofing function. Because the construction layer thickness of the crushed bentonite stone is thin, at 50 to 150 mm, it is not possible to use on-site density tests or transmission-type RI measuring devices, and compaction management using Caspol (a simple bearing capacity measuring device) is generally carried out.

[0003] The above-mentioned CASPOL (simple bearing capacity measuring device) has a proven track record and is useful as a simple test method, but it is limited to point measurements. Under these circumstances, Patent Document 1 also discloses a method of density management using a scattering type RI meter for bentonite mixed soil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-128372 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional management method using CASPOL (a simple bearing capacity measuring device), it is necessary to level the equipment each time it is installed, and it takes about two minutes to measure.In addition, the measurement requires manual labor, which makes it difficult to further improve the productivity of quality control.

[0006] Furthermore, when the method of density control using a scattering type RI meter for bentonite mixed soil disclosed in the above Patent Document 1 is simply applied to crushed bentonite stone, various problems arise. Specifically, there is a problem that the measurement accuracy deteriorates due to the unevenness of the measurement ground. In other words, the shape of the unevenness of the bentonite crushed stone is random, and the distance between the scattering type RI meter and the measurement ground is not uniform, so the measurement accuracy deteriorates when a scattering type RI meter is used.

[0007] In view of the above-mentioned problems, the present invention aims to provide a method for managing the compaction of bentonite crushed stone, which makes it possible to manage the degree of compaction of bentonite crushed stone more efficiently and accurately than conventional methods. [Means for solving the problem]

[0008] The invention related to (1) is a method for managing the compaction of bentonite crushed stone, characterized by having at least the steps of: placing a scattering-type RI meter on the compacted surface of the bentonite crushed stone to detect the amount of gamma rays; measuring the clearance between the bottom surface of the scattering-type RI meter and the compacted surface of the bentonite crushed stone; correcting the count rate ratio calculated from the gamma ray count rate of the scattering-type RI meter in accordance with the clearance to calculate a corrected count rate ratio; converting the corrected count rate ratio into a degree of compaction based on a calibration curve; and excluding the degree of compaction when the clearance is equal to or greater than a predetermined threshold value.

[0009] According to the invention related to the above (1), by having at least the steps of calculating a corrected count rate ratio according to the clearance from the count rate ratio calculated from the gamma ray count rate of the scattering type RI meter, calculating the compaction degree by correcting the detected gamma ray dose by the corrected count rate ratio, and excluding the corresponding compaction degree when the clearance is equal to or greater than a predetermined threshold, it is possible to obtain a compaction degree management accuracy comparable to that of the conventional method, CASPOL (simple bearing capacity measuring instrument), in a high efficiency and short time. In addition, in such a compaction management method for crushed bentonite stone, if the scattering type RI meter is mounted on a stand and made to move on its own, it is possible to reduce the number of management personnel, and it is possible to significantly reduce the management effort compared to the conventional method.

[0010] The invention related to (2) is a method for compaction management of bentonite crushed stone described in (1) above, in which the clearance is the average value of measurement values ​​measured by distance measuring means arranged on all four sides of the bottom surface of the scattering type RI meter.

[0011] According to the invention related to (2) above, it becomes possible to measure the clearance between the bottom surface of the scattering-type RI meter and the compacted surface of the bentonite crushed stone with greater accuracy, and the count rate ratio calculated from the gamma ray count rate of the scattering-type RI meter can be accurately corrected according to the clearance to calculate a corrected count rate ratio.

[0012] The invention related to (3) is the method for managing compaction of crushed bentonite stone described in (1) or (2) above, in which the predetermined threshold value of the clearance is 0.8 mm.

[0013] According to the invention related to (3) above, a threshold clearance of 0.8 mm is set, and if the measured clearance is equal to or greater than the threshold clearance, the degree of compaction at the corresponding measurement point is excluded, thereby enabling more accurate compaction management of bentonite crushed stone.

[0014] The invention related to (4) is a method for managing compaction of bentonite crushed stone described in any one of (1) to (3) above, in which the measurement time from the step of detecting the dose of gamma rays to the step of calculating the degree of compaction is 5 to 120 seconds.

[0015] According to the invention related to (4) above, by setting the measurement time from the step of detecting the gamma ray dose to the step of calculating the degree of compaction to 5 to 120 seconds, it is possible to significantly reduce the time and effort required for conventional measurements while maintaining the same level of management accuracy as conventional Caspol. [Brief description of the drawings]

[0016] [Figure 1] 1A and 1B are schematic diagrams of a scattering-type RI meter 1 according to one embodiment of the present invention, in which (a) is a side perspective view of the scattering-type RI meter 1, and (b) is a top perspective view of the scattering-type RI meter 1. FIG. [Diagram 2] FIG. 2 is a plan view of a bentonite crushed stone ground created in a verification experiment of the present invention. [Diagram 3] 1 is a table showing each measurement value measured in a verification experiment of the present invention. [Figure 4] This is a graph showing the relationship between the count rate ratio calculated from the gamma ray count rate, which is the measurement value of the scattering type RI meter 1, and the measured degree of compaction for an unsmoothed section and a soil tank section of a bentonite crushed ground in a verification experiment of the present invention. [Diagram 5] 1 is a graph showing the relationship between clearance and coefficient rate ratio. [Figure 6] 1 is a graph showing the relationship between the corrected count rate ratio and the measured degree of compaction in a verification experiment of the present invention. [Figure 7] 1 is a graph showing the relationship between the corrected count rate ratio after suitability determination and the measured degree of compaction in a verification experiment of the present invention. [Figure 8] 1 is a graph showing the relationship between the Ia value measured by Caspol and the degree of compaction measured in a verification experiment of the present invention. [Figure 9] 1 is a graph showing the relationship between the Caspol equivalent compaction degree and the actually measured compaction degree in a verification experiment of the present invention. [Figure 10] 1 is a graph showing the relationship between the RI density meter converted compaction degree and the actually measured compaction degree in a verification experiment of the present invention. [Figure 11] 1 is a graph showing the relationship between the judgment correction RI density meter converted compaction degree and the actually measured compaction degree in a verification experiment of the present invention. [Figure 12] 1 is a graph showing the relationship between the judgment-corrected RI density meter converted compaction degree and the actually measured compaction degree for each measurement time of the scattering-type RI meter 1 in a verification experiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, one embodiment of the method for managing compaction of bentonite crushed stone of the present invention will be described with reference to the drawings.

[0018] FIG. 1 shows a schematic diagram of a scattering-type RI meter 1 in one embodiment of the present invention, in which FIG. 1(a) shows a side perspective view of the scattering-type RI meter 1, and FIG. 1(b) shows a top perspective view of the scattering-type RI meter 1.

[0019] As shown in the figure, the scattering type RI meter 1 of this embodiment is equipped with a density measurement unit 11 capable of detecting at least gamma rays and measuring wet density, and the measurement data output from the density measurement unit 11 is transmitted to a management / control unit 2 that records, analyzes, calculates, and outputs the measurement data. The management / control unit 2 may be provided integrally with the scattering type RI meter 1, or may be provided separately and configured to output the data to the outside.

[0020] In addition, the scattering-type RI meter 1 is provided with a clearance measurement means 12 capable of measuring the clearance (distance) between the bottom surface 14 of the scattering-type RI meter 1 and the compacted surface of the bentonite crushed stone.

[0021] That is, in this embodiment, laser measuring instruments are provided as clearance measurement means 12 on all four sides of density measurement unit 11, and laser light can be received and emitted through measurement windows 13 provided on bottom surface 14 of scattering-type RI meter 1. The system is configured to calculate the average value of clearances measured by the four clearance measurement means 12.

[0022] The compaction management method for bentonite crushed stone of this embodiment using the above-mentioned scattering type RI meter 1 is a compaction management method that is at least composed of the steps of placing the above-mentioned scattering type RI meter 1 on the compacted surface of the bentonite crushed stone to detect the dose of gamma rays, measuring the clearance between the bottom surface 14 of the scattering type RI meter 1 and the compacted surface of the bentonite crushed stone, correcting the count rate ratio calculated from the gamma ray count rate of the scattering type RI meter 1 in accordance with the above-mentioned clearance to calculate a corrected count rate ratio, converting the above-mentioned corrected count rate ratio into a degree of compaction based on a calibration curve, and excluding the above-mentioned degree of compaction if the above-mentioned clearance is equal to or greater than a predetermined threshold value.

[0023] The measurement and processing configuration described above makes it possible to achieve compaction control accuracy comparable to that of the conventional method, CASPOLL (a simple bearing capacity measuring device), in a highly efficient and short time.

[0024] In addition, when calculating the degree of compaction using the scattering type RI meter 1, there are two methods: (1) calculating the dry density from the relationship between the gamma ray corrected count rate ratio and the dry density, and converting it to the degree of compaction; and (2) calculating the wet density from the relationship between the gamma ray corrected count rate ratio and the wet density, and then calculating the moisture content from the relationship between the neutron ray corrected count rate ratio and the moisture content. Then, based on the wet density and the moisture content, the dry density is calculated and converted to the degree of compaction. The degree of compaction can be calculated by either of the above methods (1) and (2). In particular, since bentonite crushed stone is a single material and has a constant moisture content, the degree of compaction can be calculated with high accuracy by the above method (1), but the degree of compaction can be calculated more accurately by the method (2).

[0025] (Verification experiment) The results of a verification experiment conducted on the compaction management method for crushed bentonite based on the above-mentioned processing configuration are described below. In the verification process, the quality of the compacted bentonite crushed ground on a full-scale basis was evaluated by actual measurements using samples and by the conventional method of CASPOL. In addition, the unevenness of the compacted surface of the crushed bentonite was also evaluated using the clearance measurement means 12.

[0026] In addition, in the compaction management method of this embodiment, in order to improve measurement accuracy, (A) "smoothing" is performed to eliminate unevenness in the bentonite crushed stone ground, (B) "clearance correction" is performed to correct the measurement value using the measured clearance, and (C) "suitability judgment" is performed to determine whether the bentonite crushed stone ground is suitable as a measurement surface. While confirming the effects of these, the accuracy of the conventional method of Caspol and the compaction management method of bentonite crushed stone of the present invention is finally verified.

[0027] · Bentonite crushed stone ground construction In the verification experiment, bentonite crushed stone with a maximum particle size of 26.5 mm or less was used. As shown in the plan view of Figure 2, the bentonite crushed stone with its natural moisture content was spread evenly and compacted with a hand guided roller to a layer thickness of 100 mm and a compaction degree of 90% or more.

[0028] In addition, 18 smoothing areas, nine per lane, were created within the compacted bentonite crushed stone ground, and a plate attached to the blade of a backhoe was grounded to eliminate unevenness.

[0029] Adjacent to the smoothed areas, there are 9 non-smoothed areas, 18 in total, with 1 lane each. In addition to the bentonite crushed stone ground created in Figure 2, three soil tank areas were created, filled with bentonite crushed stone with a natural water content, and compacted with a ram to achieve a compaction degree of 80%, 85%, and 90%, respectively, to make the surface smooth.

[0030] Test conditions and measurement items In the verification experiment, (A) sampling was performed using cores with a diameter of 50 mm and a height of 100 mm for each of the 18 unsmoothed areas, 18 smoothed areas, and 3 soil tank areas, and the degree of compaction (hereinafter, "measured degree of compaction") and water content were measured, (B) impact value (hereinafter, "Ia value") was measured using Caspol, and (C) gamma ray count rate was measured using a scattering type RI meter 1. When measuring with the scattering type RI meter 1, clearance was measured using the clearance measurement means 12 arranged on all four sides as described above.

[0031] Verification result 1 (quality of bentonite crushed stone ground) The results of each of the measurement items mentioned above are shown in Figure 3. Looking at the unsmoothed area, the measured degree of compaction was much higher than the typical actual control standard values ​​of 85% or 90%, and it can be seen that the soil was sufficiently compacted.

[0032] Furthermore, even after construction, the moisture content remains close to the natural moisture content, with little variation. Similarly, the Ia value measured by Caspol also shows little variation. The average clearance is 0.8mm, with a standard deviation of 0.4mm, indicating that there is some unevenness in the bentonite crushed stone ground surface. Although not shown in the table, the maximum clearance was approximately 1.6mm.

[0033] Verification result 2 (measurement accuracy using scattering type RI instrument 1) Figure 4 shows the relationship between the count rate ratio calculated from the gamma ray count rate, which is the measurement value of the scattering type RI meter 1, and the measured compaction degree for the unsmoothed area and the soil tank area. As shown in the figure, the coefficient of determination R 2 Since the correlation coefficient is 0.74, it can be seen that the correlation between the two is good.

[0034] In addition, the scattering type RI meter 1 is greatly affected by unevenness, but as mentioned above, the unevenness of the bentonite crushed stone ground has a maximum clearance of about 1.6 mm, and it was found that the accuracy does not deteriorate significantly with this level of unevenness. This suggests the usefulness of the scattering type RI meter 1 for compaction degree management.

[0035] Test result 3 (smoothing effect) From the results of each measurement item shown in Figure 3, the effect of smoothing on the quality of the bentonite crushed ground can be confirmed. The measured compaction degree, water content, average Ia value, and standard deviation of the smoothed area are all about the same as those of the unsmoothed area. From this, it can be concluded that the effect of smoothing on the quality of the bentonite crushed ground can be ignored.

[0036] In addition, when we look at the clearance, we can see that the smoothed area has less unevenness than the unsmoothed area. Furthermore, from Figure 4, the coefficient of determination R 2 is the coefficient of determination R for the unsmoothed area 2 This shows that the measurement accuracy of the scattering-type RI instrument 1 is slightly improved.

[0037] Verification result 4 (Effect of clearance correction and suitability judgment) The relationship between the clearance and the count rate ratio obtained from a separate experiment is shown in Figure 5. In other words, there is a correlation between the clearance and the count rate ratio, and by understanding this relationship, it is possible to correct the count rate ratio of a measurement surface with clearance to the count rate ratio when the clearance is 0 mm.

[0038] The relationship between the count rate ratio corrected in the above manner (hereinafter, "corrected count rate ratio") and the measured compaction degree is shown in Figure 6. As shown in the figure, the coefficient of determination R 2 are 0.77 and 0.79, respectively, which is an improvement in correlation compared to before correction.

[0039] Next, we will examine the effect of the suitability judgment. Figure 7 shows the relationship between the corrected count rate ratio and the measured compaction degree after excluding the data for the measurement surface with a clearance of 0.8 mm or more (suitability judgment). As shown in the figure, the coefficient of determination R 2are 0.86 and 0.85, respectively, which shows that the correlation is better than when no suitability judgment is made (see Figure 6).

[0040] In other words, it can be seen that by performing the suitability judgment, the measurement accuracy by the scattering-type RI instrument 1 for the unsmoothed section and the smoothed section becomes about the same. Therefore, by performing the above-mentioned clearance correction and suitability judgment, it is possible to improve the measurement accuracy without smoothing the crushed bentonite ground. In other words, although smoothing is very labor-intensive as it requires the use of heavy machinery, the above-mentioned clearance correction and suitability judgment can be performed simply and simultaneously with the measurement by the scattering-type RI instrument 1, it becomes possible to manage the compaction of the crushed bentonite stone more efficiently and with higher accuracy than before.

[0041] Verification result 5 (Comparison of management accuracy with conventional Caspol) Next, a comparison result between the conventional method, CASPOLL, and the management method according to this embodiment will be described.

[0042] Figure 8 shows the relationship between the Ia value obtained by the conventional method, Caspol, and the degree of compaction measured by sampling. As shown in the figure, the coefficient of determination of the approximation curve, R 2 It can be seen that there is an extremely good correlation between the degree of compaction, which is 0.92. Comparing the relationship between the degree of compaction converted from the above Ia value (hereinafter referred to as "Caspol converted compaction degree") and the actually measured degree of compaction, as shown in Figure 9, the variation in the difference between the Caspol converted compaction degree and the actually measured degree of compaction is ±5.2% at the 95% confidence interval (2σ), which shows that compaction degree management using Caspol is highly accurate.

[0043] Therefore, when comparing the relationship between the degree of compaction converted from the calibration curve of the scattering type RI instrument 1 (hereinafter, "RI density meter converted compaction degree") without performing the clearance correction and suitability judgment of this embodiment and the actual measured compaction degree by sampling, as shown in Figure 10, the 95% confidence interval (2σ) is ±6.8, which results in inferior control accuracy compared to Caspol.

[0044] On the other hand, when the clearance correction and suitability judgment of the present embodiment described above are performed, as can be seen from the relationship between the degree of compaction converted from the calibration curve after clearance correction and suitability judgment (hereinafter, "judgment-corrected RI density meter converted compaction degree") shown in Figure 11 and the actual measured compaction degree by sampling, the 95% confidence interval (2σ) is ±5.1%, making it possible to improve the management accuracy to the same level as that of the conventional method of Caspol described above.

[0045] Verification result 6 (reduction of measurement time) Fig. 12 shows the relationship between the RI density meter converted compaction degree and the actual compaction degree measured by sampling when the clearance correction and suitability judgment of this embodiment are performed. As shown in the figure, it can be seen that the longer the measurement time, the more accurate the compaction degree management becomes.

[0046] Furthermore, while the conventional method of measuring using Caspol requires about 2 minutes (120 seconds), the method of managing the compaction degree according to the present embodiment deteriorates the accuracy to ±9.46% at 95% confidence interval (2σ) at a measurement time of 2 seconds, but maintains high accuracy of the compaction degree management accuracy to ±5.21% and 6.30% at 95% confidence interval (2σ) at measurement times of 60 seconds and 5 seconds, respectively. Therefore, according to the method of managing the compaction degree according to the present embodiment, it is possible to set the measurement time to 5 to 120 seconds, which is shorter than that of the conventional Caspol, and it is possible to significantly reduce the effort required for measurement.

[0047] Although one embodiment of the present invention has been described above, the scope of the present invention is indicated by the claims rather than the description of each embodiment above, and further includes all modifications within the meaning and scope of the claims. In addition, the specific materials, dimensions, shapes, etc. described in the above embodiment can be modified within the scope of solving the problems of the present invention. [Explanation of symbols]

[0048] 1. Scattering type RI instrument 11 Density measurement section 12 Clearance measurement methods 13 Measurement window 14 Bottom 2 Management / Control Unit

Claims

1. A step of arranging a scattering type RI meter on a rolling surface of the bentonite crushed stone to detect a dose of gamma rays; A step of measuring a clearance between a bottom surface of the scattering type RI meter and a rolling surface of the bentonite crushed stone; A step of calculating a corrected count rate ratio by correcting a count rate ratio calculated from the gamma ray count rate of the scattering type RI instrument in accordance with the clearance; Converting the corrected count rate ratio into a degree of compaction based on a calibration curve; and excluding the compaction degree if the clearance is equal to or greater than a predetermined threshold. A method for controlling compaction of bentonite crushed stone.

2. The clearance is an average value of the measurement values ​​measured by distance measuring means arranged on the bottom surface of the scattering type RI instrument in all four directions. The method for controlling compaction of bentonite crushed stone according to claim 1.

3. The predetermined threshold value of the clearance is 0.8 mm. A method for controlling compaction of bentonite crushed stone according to claim 1 or 2.

4. The measurement time from the step of detecting the dose of gamma rays to the step of calculating the degree of compaction is 5 to 120 seconds. A method for controlling compaction of bentonite crushed stone according to any one of claims 1 to 3.

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