JP2021127647A - Selection method of sample preparation method, and sample preparation method - Google Patents

Abstract

To provide a selection method of sample preparation method capable of facilitating the determination of which method, tapping method or rammer method, should be used to prepare the sample according to the characteristics of the soil, and a sample preparation method.SOLUTION: The selection method of sample preparation is a selection method which of the tapping method or the rammer method should be selected as the sample preparation method. The method includes the steps of: supplying solidified soil which is a mixture of sample soil and cement-based solidifying material into a cylindrical body placed on a flow table; pulling up the cylindrical body in the vertical direction and removing the same to leave only the solidified soil on the flow table; measuring the flow value of the solidified soil using the flow test according to JIS R 5201: 2015 "Physical test method for cement"; and determining whether the flow value is greater than or equal to the specified value, whether or not. When the flow value is greater than or equal to the specified value, the tapping method is selected; and when the flow value is less than the specified value, the Rammer method is selected.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for selecting a method for producing a specimen in which soil and a cement-based solidifying material are mixed, and a method for producing a specimen.

In recent years, ground improvement works using cement-based solidifying materials have increased, and various soil quality improvements have been made. As a method for improving such soil quality, the methods described in Patent Documents 1 to 3 are known.
In the method for producing wet ground-improved soil described in Patent Document 1, when soil, a solidifying material, and water or muddy water are mixed to produce wet soil-improved soil, the sand content and water content of the soil are measured. The process of obtaining the ratio of the solidifying material to water corresponding to the desired uniaxial compressive strength by the correlation between the ratio of the solidifying material to water in the ground-improved soil and the uniaxial compressive strength, and the value of the breathing rate of the ground-improved soil. , The step of obtaining the ratio of the mixture to water corresponding to the desired breathing rate by the correlation with the ratio of the mixture of soil and the solidifying material to water, the step of obtaining the wet density of the ground-improved soil, and the results of each of the above steps. Based on this, it includes a step of determining the mixing ratio of soil, solidifying material and water or muddy water.

Further, the ground improvement method described in Patent Document 2 is a ground improvement method for increasing the strength of the current position soil by mixing and stirring with the solidifying material while excavating the current position soil, and is a mixing and stirring method attached to the tip of the arm of the backhoe. The head is penetrated into the ground for improvement. At this time, the fluidity of the treated soil immediately after the improvement treatment is positively changed according to the improvement treatment depth so that the value of the load resistivity of the mixing / stirring head is 50% or less, and the improvement treatment is performed. The index of the property is a table flow value, and the flow value for each improved processing depth is determined based on the predetermined improved processing depth-fluidity characteristic (flow value).

Further, the quality control method for fluidized soil described in Patent Document 3 is a quality control method for fluidized soil in which construction-generated soil is used as muddy soil and a solidifying material is added thereto, and the solidifying material is used. A part of the muddy soil before addition or a part of the fluidized soil after adding the solidifying material is collected, and the flow value of this soil is measured by a flow test (JHS 313-1992 cylinder method). The permissible range of flow management is within ± 30 mm, more preferably within ± 20 mm with respect to the target flow value, and the volatility is suppressed within 30%.

Japanese Unexamined Patent Publication No. 2002-180449 Japanese Unexamined Patent Publication No. 2005-98072 Japanese Unexamined Patent Publication No. 2009-148689

By the way, even if a cement-based solidifying material is used, the strength of the improved soil differs depending on the type of soil. It is necessary to confirm the strength development of the soil. For the preparation of specimens for this indoor compounding test, the Japanese Geotechnical Society standard "Method for preparing specimens without compaction of stable treated soil" (JGS0821-2009) or the Cement Association standard test method "Improved products using cement-based solidifying material". (JCAS L-01: 2006) is used. The former is also called the tapping method, in which solidified soil is packed in a mold and the mold is struck on the floor or the like to remove air bubbles. The state of the solidified soil is relatively soft and suitable for dumplings or strings. The latter is also called the Rammer method, which is a method of preparing a specimen by compacting the solidified soil by the energy generated by the fall of the Rammer. The solidified soil is relatively hard and is applied when it is difficult to prepare a specimen by the tapping method.

However, when producing a specimen by the tapping method or the Rammer method, it may be difficult to select which method is used to produce the specimen. For example, even a skilled technician decided that the tapping method was preferable and prepared the specimen, but the finished specimen varied widely, making it difficult to produce a uniform specimen, and the Rammer method was used. In some cases, a uniform specimen could be produced. And vice versa. Normally, dry addition without water (W / C = 0%) makes the solidified soil hard, so specimens are generally prepared by the Rammer method, but the tapping method may be preferable depending on the properties of the sample soil. There are many cases where even a skilled engineer has trouble making a decision. Therefore, there is a demand for a method for selecting a specimen preparation method that makes it easy to determine which method, the tapping method or the Rammer method, should be used to prepare the specimen according to the characteristics of the soil.

The present invention has been made in view of such circumstances, and is a method for producing a specimen, which makes it easy to determine which method, the tapping method or the Rammer method, should be used to prepare the specimen according to the characteristics of the soil. It is an object of the present invention to provide a method for selecting a sample and a method for preparing a specimen.

The method for selecting the specimen preparation method of the present invention is a method for selecting a specimen preparation method for selecting either the tapping method or the rammer method as the specimen preparation method, in which the sample soil and the cement-based solidifying material are mixed. The solidified soil was put into a cylinder placed on a flow table, and the cylinder was pulled up vertically to be removed, so that only the solidified soil was left on the flow table and the solidified soil was removed. The flow value is measured by a flow test according to JIS R 5201: 2015 "Physical test method for cement", it is determined whether or not the flow value is equal to or higher than a predetermined value, and the flow value is equal to or higher than the predetermined value. In this case, the tapping method is selected, and when the flow value is less than the predetermined value, the rammer method is selected.

In the present invention, since the specimen preparation method can be selected only by determining whether or not the flow value of the solidified soil in the flow test is equal to or higher than a predetermined value, the specimen preparation method can be easily performed even by a non-skilled engineer. Can be set to. Specifically, when the flow value of the solidified soil is equal to or higher than a predetermined value, it can be seen that the solidified soil is loose because the solidified soil spreads widely due to vibration. Set to the tapping method. On the other hand, when the flow value of the solidified soil is less than a predetermined value, it can be seen that the solidified soil is hard because the spread of the solidified soil is small due to vibration. In this case, the specimen preparation method is set to the Rammer method. do.

As a preferred embodiment of the method for selecting the method for producing the specimen of the present invention, the frequency of the flow table in JIS R 5201: 2015 “Physical test method for cement” is replaced with 5 times or more at a rate of once per second. It can be set within 30 times or less, and the predetermined value may be set according to the frequency.
In JIS R 5201: 2015 "Physical test method for cement", the frequency is set to 15 times at a rate of once per second. In the above aspect, the frequency can be freely set within 5 to 30 times at a rate of once per second, and a predetermined value is set according to the frequency. Therefore, for example, the target solidified soil is clear. If it is hard, it is unlikely that the solidified soil will spread even if it is not vibrated 15 times. Therefore, the method for preparing the specimen can be quickly selected by reducing the frequency. On the other hand, when the target solidified soil is clearly loose, the solidified soil can be spread more reliably by applying vibration 30 times, so that the method for preparing the specimen can be easily selected. ..

As a preferred embodiment of the method for selecting the method for producing a specimen of the present invention, when the flow test is carried out based on JIS R 5201: 2015 “Physical test method for cement”, the predetermined value is preferably 110 mm.

In the method for producing a specimen of the present invention, the specimen is produced by the production method selected by the method for selecting the method for producing a specimen.
In the present invention, as a method for producing a specimen, a specimen can be produced by a more suitable production method among the Rammer method and the tapping method.

According to the present invention, it is possible to easily determine which method, the tapping method or the Rammer method, should be used to prepare the specimen according to the characteristics of the soil, and the specimen can be prepared by an appropriate method.

It is a flowchart which shows the procedure of the selection method of the specimen manufacturing method which concerns on one Embodiment of this invention. It is a schematic diagram which shows the process of putting solidification treated soil into a cylinder in the selection method of the said embodiment. It is a schematic diagram which shows the process of removing a cylinder in the vertical direction in the selection method of the said embodiment. It is a schematic diagram which shows the process of giving vibration to solidified treated soil in the selection method of the said embodiment. It is a schematic diagram which shows the process of measuring the spread of solidified soil after vibration in the selection method of the said embodiment. It is a schematic diagram which shows the specimen manufacturing method by the tapping method selected by the selection method of the said embodiment. It is a schematic diagram which shows the specimen manufacturing method by the Rammer method selected by the selection method of the said embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

The method for selecting the specimen manufacturing method of the present embodiment (hereinafter referred to as the selection method) is executed by the procedure shown in the flowchart shown in FIG. The specimen is used for an indoor compounding test, and the specimen can be prepared by the tapping method according to the Japanese Geotechnical Society standard "Method for producing specimen without compaction of stable treated soil" (JGS0821-2009) or cement. One of the Rammer methods according to the association standard test method "Strength test method of improved body using cement-based solidifying material" (JCAS L-01: 2006) is used. The method for selecting the sample preparation method of the present embodiment is to facilitate the determination of whether to use the tapping method or the Rammer method for the solidified treated soil in which the cement-based solidifying material is mixed with the sample soil. Will be executed. Hereinafter, the method for selecting the method for producing the specimen will be described in detail.

First, the cement-based solidifying material is mixed with the sample soil to prepare the solidified soil 10 (step S11). The sample soil is the soil of the land to be subjected to the indoor compounding test, and the soil quality is generally composed of viscous soil or sandy soil. Further, as the cement-based solidifying material, for example, Youth Labyrinth 50 (manufactured by Mitsubishi Materials Corporation, Iwate Factory) is used. In the treatment of step S11, a cement-based solidifying material of 200 to 400 kg / m ^{3 is added to 1 m 3} of the sample soil, and water is added and mixed as necessary to mix the water-solidified material ratio (cement-based). The solidified soil has a ratio of water to solidifying material (W / C) of 0% or more and 100% or less.

After the solidified soil 10 is prepared by the treatment in step S11, the solidified soil 10 is put into the cylinder 20 as shown in FIG. 2 (step S12). Specifically, two layers of solidified soil 10 are placed on the cylinder 20 placed in the center on the upper surface 31 of the flow table 30 in accordance with the flow test procedure described in JIS R 5201: 2015 “Physical test method for cement”. Each layer is pierced 15 times over the entire surface so that the tip of the thrust rod with a diameter of 20 ± 1 mm and a mass of 500 ± 3 g enters to a depth of about 1/2 of each layer, and finally the shortage is supplemented as necessary. It is performed by smoothing the surface. The tubular body 20 is formed in a truncated cone shape having an upper inner diameter of 70.0 ± 0.5 mm, a lower inner diameter of 100 ± 0.5 mm, and a height of 60.0 ± 0.5 mm.

Then, when the solidified soil 10 is filled in the tubular body 20 by the process of step S12, the tubular body 20 is moved in the vertical direction and removed as shown in FIG. 3 (step S13). As a result, as shown in FIG. 4, the solidified soil 10 formed in a truncated cone shape is arranged at the center of the upper surface 31 of the flow table 30.

When the truncated cone-shaped solidified soil 10 is placed in the center of the upper surface 31 by the process of step S13, a flow device (not shown) is driven to cause a predetermined number of vibrations on the truncated cone-shaped solidified soil 10. (Step S14). This vibration imparting is performed by giving the flow table 30 a falling motion at a rate of 15 times in 15 seconds.
When the process of step S14 is executed, the portion of the truncated cone-shaped solidified soil 10 gradually collapses on the upper surface 31 side due to vibration and spreads outward in the circumferential direction. For example, the outer diameter of the solidified soil 10 is shown in FIG. The state shown by the alternate long and short dash line in FIG. 5 is expanded to the state shown by the solid line in FIG.

After the treatment in step S14, the outer diameter of the solidified treated soil 10 spread on the upper surface 31 is measured to calculate the flow value (step S15). Specifically, as shown in FIG. 5, the width w1 in the direction in which the diameter after the solidified soil 10 spreads is recognized as the maximum and the width w2 in the direction orthogonal to the width w1 are measured up to 1 mm units, and the average thereof is measured. The value is represented by an anonymous integer in millimeters (mm). This test is performed twice, and the average value is used as the flow value.
Then, it is determined whether or not the flow value is equal to or greater than a predetermined value (step S16). In the present embodiment, for example, since vibration is applied at a rate of 15 times in 15 seconds, a predetermined value is set to 110 mm.

When it is determined in the determination step S16 that the flow value is equal to or greater than a predetermined value (YES in S16), it is determined that the tapping method is desirable as the specimen preparation method (step S17). Specifically, when the spread (flow value) of the solidified soil 10 is equal to or greater than a predetermined value, it can be seen that the solidified soil 10 is loose because the solidified soil 10 spreads widely due to vibration. Therefore, the tapping method is selected as the method for preparing the specimen.
On the other hand, when it is determined that the flow value is less than a predetermined value (NO in S16), the Rammer method is selected as the method for producing the specimen (step S18). Specifically, it can be seen that the solidified soil 10 is hard because the spread of the solidified soil 10 is small due to vibration. Therefore, the Rammer method is selected as the method for preparing the specimen.
That is, in the present embodiment, the specimen preparation method can be selected only by determining whether or not the spread (flow value) of the solidified treated soil 10 in the flow test is equal to or higher than a predetermined value. End the process.

(Method for making specimens)
In the present embodiment, the specimen is produced by the production method selected by the selection method of the specimen production method described above. For example, when the tapping method is selected, the specimen is prepared based on the Japanese Geotechnical Society standard "Method for producing specimen without compaction of stable treated soil" (JGS0821-2009). Specifically, as shown in FIG. 6, the solidified soil 10 is put into the bottomed tubular container 40 in three layers, and the container 40 is driven into the concrete floor 50 or the like for each layer. , Prepared by removing air bubbles.

On the other hand, when the Rammer method is selected, a specimen is prepared based on the Cement Association standard test method "Strength test method of improved body using cement-based solidifying material" (JCAS L-01: 2006). Specifically, as shown in FIG. 7, the solidified soil 10 is divided into three layers and put into the container 40 placed on the concrete floor 50 or the like, the grip portion 63 of the rammer device 60 is gripped, and the support shaft is supported. With 61 placed in the center of the container 40, a 1.5 kg rammer 62 is tamped 12 times for each layer at a drop height of 20 cm.

In the present embodiment, the specimen preparation method can be selected only by determining whether or not the flow value of the solidified treated soil 10 in the flow test is equal to or higher than a predetermined value. Can be easily set. Specifically, when the flow value of the solidified soil 10 is equal to or higher than a predetermined value, it can be seen that the solidified soil 10 is loose because the solidified soil 10 is widely spread by vibration. The method is set to the tapping method. On the other hand, when the flow value of the solidified soil 10 is less than a predetermined value, it can be seen that the solidified soil 10 is hard because the spread of the solidified soil 10 is small due to vibration. Set to law.

Further, since a more suitable production method is selected from the Rammer method and the tapping method as the specimen production method according to the method for selecting the specimen production method of the present embodiment, the specimen production method selected by this selection method is used. Specimens can be prepared. Thereby, the specimen can be appropriately produced.

In addition, the detailed configuration is not limited to the configuration of the embodiment, and various changes can be made without departing from the gist of the present invention.
For example, in the above embodiment, in the process of step S14, the number of times (frequency) to apply vibration to the flow table 30 is set to 15 times at a rate of once per second, but the number is not limited to this. For example, in the process of step S14, instead of the frequency of JIS R 5201: 2015 “Physical test method for cement”, it may be possible to set the frequency at a rate of once per second from 5 times to 30 times. In this case, the predetermined value may be set according to the frequency. That is, the predetermined value depends on the frequency. For example, when the vibration is applied 5 times in 5 seconds, the predetermined value is set to 105 mm, and when the vibration is applied 30 times in 30 seconds. It is preferable to set a predetermined value to 120 mm.

In this modification, the frequency in the process of step S14 can be freely set within 5 to 30 times at a rate of once per second, and a predetermined value is set according to the frequency. When the solidified soil 10 is clearly hard, it is unlikely that the solidified soil 10 will spread even if it is not vibrated 15 times. Can be selected quickly. On the other hand, when the target solidified soil 10 is clearly loose, the solidified soil 10 can be expanded more reliably by applying vibration 30 times, so that the method for preparing the specimen can be easily selected. become.

Cohesive soil (Sendai City, Miyagi Prefecture, wet density 1.65 g / cm ³ , moisture content 46.1% by mass), sandy soil (Osaki City, Miyagi Prefecture, wet density 1.97 g / cm ³ , moisture content 18.8) Each of these sample soils (% by mass) was used as sample soil, and each of these sample soils was solidified using a cement-based solidifying material Youth Labyrinth 50 (US50) manufactured by Mitsubishi Materials Corporation Iwate Factory. Solidifying material amount of solidification soil, to wet soil 1 m ³ and 300 kg / ^{m 3,} by changing the water solidifying material ratios shown in Table 1 (W / C) 0 to 100% by weight Sample No. 1-No. It was used as 20 solidified soils. In addition, these sample Nos. 1-No. No. 20 was prepared by 3 pieces each.

These sample Nos. 1-No. For the solidified soil of 12, according to the standard (JIS R 5201: 2015 "Physical test method of cement", "12 flow test"), the solidified soil is subjected to 15 drop vibrations at a rate of once per second. Flow test was carried out. In addition, sample No. 13-No. For No. 16, a flow test of the solidified soil was carried out by applying falling vibrations 5 times at a rate of once per second. Furthermore, the sample No. 17-No. For 20, a flow test of the solidified soil was carried out by applying 30 times of drop vibration at a rate of once per second, and the flow value was calculated. This flow value is the average value of the flow values of each of the three samples and is shown in Table 1.
After these flow tests, the Rammer method, which is a method for preparing specimens according to the Cement Association standard test method "Strength test method for improved bodies using cement-based solidified materials" (JCAS L-01: 2006), and the Japanese Geotechnical Society standard " Specimens were prepared by each method of the tapping method, which is a method for preparing specimens according to "Method for preparing specimens without compaction of stabilized soil" (JGS0821-2009).

[Evaluation of specimen]
Then, the mold was removed from the mold at the age of 7 days, and the clogging of the specimen was visually observed. In the visual observation judgment, a uniform specimen is judged to be good "A", a case where cavities are conspicuous in a part is judged as "B", and a case where cavities are conspicuous in many places is not possible "C". It was judged.
In addition, each sample No. 1-No. The coefficient of variation (%) of 20 was calculated. This coefficient of variation is the coefficient of variation of each flow value of the three specimens, and the smaller this value is, the smaller the variation of the flow values of the three specimens is. The evaluation of these specimens is shown in Table 1.

When the drop frequency is 15 times at a rate of once per second, the sample No. 1-No. From 6, it can be seen that when the flow value is less than 110 mm, the state of the specimen is better in the Rammer method than in the tapping method, and the coefficient of variation, which is an index of variation, is small. This is sample No. 7 to No. As is clear from No. 12, the Rammer method is better when the flow value is less than 110 mm, even if the type of soil is different. In addition, sample No. Regarding No. 11, the state of the specimen is “B” also in the Rammer method, but the coefficient of variation is 22%, which is a large variation. Sample No. Looking at No. 12, since the state of the specimen is “A”, it can be seen that it is better to use the tapping method.
On the other hand, when the drop frequency is 5 times at a rate of once per second, the sample No. 13-No. In No. 16, it can be seen that when the flow value is less than 105 mm, the state of the specimen is better in the Rammer method, and when the flow value is 105 mm or more, the tapping method is better. Further, when the drop frequency is 30 times at a rate of once per second, the sample No. 17-No. At 20, it can be seen that the Rammer method is better when the flow value is less than 120 mm, and the tapping method is better when the flow value is 120 mm or more.

Based on these facts, even if the drop frequency is different from the 15 times of the JIS R 5201: 2015 "Physical test method for cement", the drop frequency is determined and the table flow and the condition of the specimen are investigated in advance. In the above embodiment, the specimen manufacturing method is selected by setting the predetermined value when the falling frequency is 5 times to 105 mm and setting the predetermined value when the falling frequency is 30 times to 120 mm. Was shown to be possible.

10 ... Solidified soil 20 ... Cylinder 30 ... Flow table 31 ... Top surface 40 ... Container 50 ... Concrete floor 60 ... Rammer device 61 ... Support shaft 62 ... Rammer 63 ... Grip

Claims (4)

This is a method for selecting a specimen preparation method for selecting either the tapping method or the rammer method as the specimen preparation method. The solidified treated soil in which the sample soil and the cement-based solidifying material are mixed is placed on the flow table. By throwing it into the cylinder and pulling it up vertically to remove it, only the solidified soil is left on the flow table, and the flow value of the solidified soil is set to JIS R 5201: 2015 "Physics of cement". It is measured by a flow test according to the "test method", it is determined whether or not the flow value is equal to or higher than a predetermined value, and when the flow value is equal to or higher than the predetermined value, a tapping method is selected and the flow value is the predetermined value or more. A method for selecting a specimen manufacturing method, which comprises selecting the Rammer method when the value is less than the predetermined value. Instead of the frequency of the flow table of JIS R 5201: 2015 "Physical test method of cement", it can be set at a rate of once per second from 5 times to 30 times, and the predetermined value is set. The method for selecting a specimen manufacturing method according to claim 1, wherein the sample is set according to the frequency. The method for selecting a specimen manufacturing method according to claim 1, wherein the predetermined value is 110 mm. A method for producing a specimen, which comprises producing the specimen by the production method selected by the method for selecting the specimen production method according to any one of claims 1 to 3.

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