JP7311853B2 - Methods, programs, and systems for determining soil quality - Google Patents

Description

The present invention relates to methods, programs, and systems for determining soil quality.

When a building or the like is built on soft ground, it may subside under its own weight, resulting in uneven subsidence in which the level of the building or the like is impaired. If it is difficult to restore the horizontal level, the building will be abandoned, and even if it can be restored, a huge repair cost will be incurred. Continuing to use a building whose horizontality is impaired may damage the health of the user. Therefore, by investigating the soil properties that make up the ground, it is possible to understand the soil properties before constructing buildings, etc. on soft ground that has a high risk of uneven settlement, and then improve the ground for such soft ground. It is desirable to

For example, Patent Literature 1 discloses a method for designing a mixture of improved soil. For the method of designing the mixture of the improved soil, a soil survey is conducted using an ignition loss test. Then, it is characterized by determining whether the soil to be improved is organic soil or high organic soil based on the result of the soil investigation obtained from the ignition loss test.

JP 2005-273387 A

By the way, uneven subsidence of the ground is a problem caused by humic acid contained in the soft soil of the soft ground. Humic acid causes poor solidification of cement-based solidifying agents used for ground improvement. Therefore, when improving soft ground, it is necessary to accurately estimate the content of humic acid in the ground.
However, the ignition loss test disclosed in Patent Document 1 can measure the content of organic soil that causes poor solidification of ground improvement, but soft soil with a high risk of uneven settlement, that is, the content of humic acid in the ground The rate cannot be measured directly. As a result, the method for estimating the humic acid content of the ground by the ignition loss test has low estimation accuracy and cannot provide highly reliable estimation of the humic acid content of the ground.

The present invention was invented in view of such circumstances, and an object of the present invention is to provide a method and program for determining soil quality, which can easily and highly accurately estimate the humic acid content of the ground. , and to provide a system.

A method for estimating the humic acid content of ground according to one aspect of the present invention includes a stress applying step of applying a shear stress to a soil sample, and a first state in which the soil sample is elastically deformed by the shear stress, and is non-elasticly deformed. A yield strain acquisition step of acquiring a soil sample yield strain, which is a shear strain at the boundary between the first state and the second state when about to shift to the second state, and using the yield strain, the ground to which the soil sample belongs and a humic acid content estimation step of estimating the estimated humic acid content of.

According to this method, the humic acid content of the ground can be estimated simply and with high accuracy.

In the above method, the step of applying stress may comprise gradually increasing shear stress on the soil sample by sinusoidal vibration or unidirectional rotational motion.

According to this method, highly reproducible measurement data can be obtained.

In the above method, the stress applying step may comprise applying shear stress to the soil sample using a rheometer.

According to this method, the yield strain can be obtained using a simple device.

In the above method, in the yield strain acquisition step, when the storage modulus of the soil sample decreases from a first value, which is a constant value, to a second value due to shear stress, a shear strain corresponding to the second value is obtained. The second value may be a numerical value lower than the first value by 2% or more and 20% or less, including obtaining the yield strain.

According to this method, the yield strain can be obtained using a simple method.

In the above method, the second value may be a numerical value that is 5% lower than the first value.

According to this method, the yield strain can be obtained using a simple method.

In the above method, the humic acid content rate estimation step may include calculating an estimated humic acid content rate corresponding to the yield strain using a previously calculated correlation between the yield strain of the soil and the humic acid content rate. good.

According to this method, the humic acid content of the ground can be estimated using a simple method.

The above method may further include a correlation equation generating step of generating a correlation equation using soil samples of a plurality of modified soils, at least some of which have different humic acid contents.

According to this method, a correlation formula can be generated using a simple method.

In the above method, the step of generating the correlation equation includes obtaining the yield strain of each of the soil samples of the plurality of modified soils by the stress applying step and the yield strain obtaining step, and obtaining the yield strain of each of the soil samples of the plurality of modified soils. generating a correlation equation using the yield strain and the humic acid content of each of the soil samples in the plurality of modified soils.

According to this method, the yield strain can be used to generate the correlation equation.

In the above method, the step of generating the correlation equation may be a step performed before the step of estimating the content of humic acid.

According to this method, the estimated humic acid content can be calculated from the correlation formula.

In the above method, the correlation equation generating step may be a step performed only once.

This method simplifies the generation of the correlation equation.

A ground humic acid content estimation program according to one aspect of the present invention causes one or a plurality of computers to execute processing using the soil determination method according to any one aspect of the present invention.

According to this program, it is possible to estimate the humic acid content of the ground simply and with high accuracy.

A soil determination system according to one aspect of the present invention includes an information processing unit that executes processing related to the soil determination method according to any one aspect of the present invention.

According to this system, it is possible to estimate the humic acid content of the ground simply and with high accuracy.

According to the present invention, it is an object of the present invention to provide a method, program, and system for discriminating soil quality, which can easily and accurately estimate the humic acid content of the ground.

1 is a block diagram for explaining the configuration of a soil discrimination system according to this embodiment; FIG. 1 is a diagram for explaining the configuration of a rotational rheometer according to this embodiment; FIG. FIG. 4 is a diagram for explaining the configuration of the measuring section of the rotational rheometer according to the embodiment; FIG. 3 is a block diagram for explaining the configuration of a control unit of the rotational rheometer according to the embodiment; FIG. 4 is a storage modulus-shear strain curve generated by a rotational rheometer according to the present embodiment; It is a block diagram for explaining the configuration of a computer according to the embodiment. It is a figure which shows an example of correlation information DB which concerns on this embodiment. FIG. 4 is a diagram showing a γe-Fc plot diagram and an approximated curve corresponding to the correlation information DB according to this embodiment; FIG. 4 is a flow chart for explaining estimation of humic acid content in ground by the soil discrimination system according to the present embodiment. It is a figure for demonstrating the kind of soil sample used for the measurement of the soil discrimination|determination system which concerns on this embodiment. It is a figure for demonstrating the kind of soil sample used for the measurement of the soil discrimination|determination system which concerns on this embodiment. FIG. 4 is a diagram for explaining the accuracy of an estimated humic acid content rate by the soil discrimination system according to the present embodiment; FIG. 3 is a diagram for explaining the relationship between the estimated humic acid content rate and the humic acid content rate by the soil discrimination system according to the present embodiment;

Embodiments of the present invention are described below. In the following description of the drawings, identical or similar components are denoted by identical or similar reference numerals. The drawings are examples, and the dimensions and shapes of each part are schematic, and the technical scope of the present invention should not be construed as being limited to the embodiments.

[Embodiment]
<Soil discrimination system 1>
First, the configuration of a soil determination system 1 according to this embodiment will be described with reference to FIG. FIG. 1 is a block diagram for explaining the configuration of a soil discrimination system 1 according to this embodiment.

A soil discrimination system 1 according to this embodiment includes a rotational rheometer 2 that measures the rheological properties of a sample, and a computer 3 that executes processing such as calculation and analysis on the measurement results of the rotational rheometer 2. . The rotational rheometer 2 and computer 3 are connected via a communication cable L so as to be communicable. Note that the rotational rheometer 2 and the computer 3 may be communicably connected to each other not via the communication cable L but via a network such as a LAN or the Internet.

<Rotational rheometer 2>
Next, the configuration of the rotational rheometer 2 according to this embodiment will be described with reference to FIGS. 2 to 5. FIG. FIG. 2 is a diagram for explaining the configuration of the rotational rheometer 2 of this embodiment. 3a to 3d are diagrams for explaining the configuration of the measuring section 10 of the rotational rheometer 2 of this embodiment. FIG. 4 is a block diagram for explaining the configuration of the controller 20 of the rotational rheometer 2 according to this embodiment. FIG. 5 is a diagram showing a storage modulus-shear strain curve generated by the rotational rheometer 2 according to this embodiment.

The rotary rheometer 2 according to the present embodiment includes a measurement unit 10, a control unit 20 that controls the operation of the measurement unit 10, a drive unit 30 that drives the overall operation, and a control unit 20 that supports the measurement unit 10. and a housing 40 that accommodates the drive unit 30 .

The measuring section 10 has a movable upper measuring section 10 a and a lower measuring section 10 b fixed to the housing 40 . Further, each component of the upper measuring section 10a and the lower measuring section 10b is provided coaxially.

The upper measurement part 10a has an upper sensor 11 and a rod 13 to which the upper sensor 11 is attached. This upper sensor 11 is a disk-shaped sensor, and may be subjected to notching on the surface. Both the diameter of the upper sensor 11 and the diameter of the rod 13 are 10 mm. The rod 13 is connected to the driving portion 30 so as to transmit the driving force of the driving portion 30 to the upper sensor 11 .

The lower measuring section 10 b has a lower sensor 12 , a lower plate 14 and a fence 16 . The lower plate 14 is fixed to the housing 40, the lower sensor 12 is provided on the center side of the upper surface of the lower plate 14, and the fence 16 protrudes from the upper surface of the lower sensor 12. is located in the center of the

Further, the lower sensor 12 is a disc-shaped sensor, and the surface thereof may be notched. The lower sensor 12 is formed larger than the upper sensor 11 and has a diameter of 21 mm. The lower plate 14 is disc-shaped and has a diameter of 70 mm. In the following description, when the upper sensor 11 and the lower sensor 12 are not distinguished from each other, they may be collectively referred to as "both sensors".

The fence 16 is ring-shaped and has an outer wall surface with a diameter of 13 mm and an inner wall surface with a diameter of 11 mm. That is, the shape of the inner wall surface of the fence 16 is slightly larger than the outer shape of the upper sensor 11 . Thus, it is possible for the upper sensor 11 to go inside the fence 16 towards the lower sensor 12 . Further, when the fence 16 is attached to the lower sensor 12, the height of the fence 16 protruding from the upper surface of the lower sensor 12 (hereinafter referred to as "protrusion height of the fence 16") is 3 mm. Thus, the inner wall surface of the fence 16 and the upper surface of the lower sensor 12 form a recess 18 .

This concave portion 18 accommodates the sample and exhibits the function of the lower sensor 12 . In addition, the concave portion 18 allows a certain volume (constant thickness) to be measured for rheological properties of samples other than liquids, such as powder samples, samples composed of small grains or clumps, etc. Measurement conditions can be created for any sample. Furthermore, the diameter of the inner wall surface of the recess 18, that is, the inner wall surface of the fence 16, is about 1 mm larger than the diameter of the upper sensor 11 that passes through this inner wall surface while vibrating sinusoidally or rotating in one direction with respect to this inner wall surface. formed large. With such a configuration, it is possible to secure the degree of freedom of movement of the upper sensor 11 and improve the reproducibility of the data measured by both sensors.

The control unit 20 is an example of an information processing unit. Information is exchanged between a processor 21 configured as a CPU or GPU, a main memory 22 configured by a DRAM or the like and temporarily storing data and programs, and a user or the like. , a communication unit 24 for controlling wired or wireless communication, and a storage 25 configured by a magnetic disk, flash memory, or the like for storing data and programs.

The processor 21 loads a program stored in the storage 25 or the like into the main memory 22 and executes instructions included in the program. The input/output unit 23 includes, for example, an input device such as a keyboard and an output device such as a display.

The communication unit 24 is implemented as hardware such as a network adapter, various types of communication software, or a combination thereof. In this embodiment, the communication unit 24 communicates with an external device such as the computer 3 .

In addition, the processor 21 executes instructions included in a program stored in the storage 25 or the like, thereby executing a stress applying unit 211 that performs processing related to measurement of the rheological properties of the sample, and and a yield strain acquisition unit 212 that performs processing related to data processing.

The stress applying unit 211 measures rheological properties of the sample by applying stress to the sample. The stress applying unit 211 according to this embodiment measures the rheological properties of the soil sample by, for example, applying shear stress to the soil sample. Further, the rheological properties to be measured according to the present embodiment are change properties of the storage elastic modulus G' of the soil sample and the shear strain γ corresponding to the storage elastic modulus G' due to an increase in shear stress. In the following, unless otherwise specified, the sample will be explained as an example of a soil sample collected from the ground.

Further, the stress applying unit 211 uses the upper sensor 11 of the measuring unit 10, for example, to contact the soil sample held in the recess 18 on the lower sensor 12 side and apply shear stress. The stress applying unit 211 gradually increases the shearing stress applied to the soil sample, for example, by sinusoidal vibration in which the upper sensor 11 rotates forward and backward with respect to the lower sensor 12 at the crossings. Moreover, the stress applying unit 211 may gradually increase the shear stress applied to the soil sample by unidirectional rotational motion.

The yield strain acquiring unit 212 stores and summarizes the measurement data of the storage elastic modulus G′ of the soil sample measured by the stress applying unit 211 and the shear strain γ corresponding to the storage elastic modulus G′, thereby obtaining the storage elastic modulus - Generate a shear strain curve. Then, the yield strain obtaining unit 212 obtains the yield strain γe using the generated storage modulus-shear strain curve of the soil sample.

Here, the soil sample transitions from a first state of elastic deformation to a second state of non-elastic deformation due to an increase in applied shear stress. From the shape of the storage modulus-shear strain curve, as shown in FIG. 5, when the soil sample is elastically deformed, the shape of the storage modulus-shear strain curve forms a substantially horizontal straight line. On the other hand, when the soil sample undergoes inelastic deformation, the shape of the storage modulus-shear strain curve slopes in the direction in which the storage modulus G' decreases, forming a slip shape. In the following, the portion of the storage modulus-shear strain curve, which is an almost horizontal straight line related to the elastic deformation of the soil sample, is defined as the “storage modulus plateau region”, and a constant value related to this storage modulus plateau region A certain storage modulus G' is defined as a storage modulus Gp' in the plateau region. In addition, the second state of non-elastic deformation includes various deformation states other than elastic deformation, such as elastic-plastic deformation and plastic deformation.

The yield strain γe according to the present embodiment is defined as is the shear strain γ. That is, the yield strain γe is the elastic limit of the soil sample. In the case of FIG. 5, the left side of the storage modulus-shear strain curve of the yield strain γe shows the first state of elastic deformation, and the storage modulus-shear strain curve of the right side of the yield strain γe is , indicates a second state of inelastic deformation. In addition, the boundary according to the present embodiment is the point of change when the first state of elastic deformation changes to the second state of non-elastic deformation. It can be a region.

Moreover, the yield strain γe according to the present embodiment is located at the bending portion of the storage modulus-shear strain curve. From the relationship between the yield strain γe and the storage modulus Plato region, there are differences depending on the properties of the soil such as ordinary soil and special soil, but the yield strain γe is the storage modulus Gp ', the shear strain γ corresponding to the storage modulus G', which is the second value when the first value is decreased by about 2% or more and 20% or less. In addition, in the case of a soil sample for building an ordinary house, the yield strain γe is the shear strain γ corresponding to the second value, which is about 5% lower than the first value, the storage modulus Gp′ in the plateau region. . In other words, as shown in FIG. 5, the difference ΔG′ between the storage modulus Ge′, which is the second value corresponding to the yield strain γe, and the storage modulus Gp′ in the plateau region, which is the first value, is about the plateau region is 5% of the storage modulus Gp' of

Thus, in the rotary rheometer 2 according to this embodiment, the upper sensor 11 is sine-sine with respect to the soil sample arranged between the upper sensor 11 and the lower sensor 12 based on the control of the control unit 20 . Give wave vibration. Both sensors of the rotary rheometer 2 detect the stress (torque) and displacement occurring in the sample between the two sensors, measure the rheological properties of the soil sample, and acquire the yield strain γe.

<Computer 3>
Next, the configuration of the computer 3 according to this embodiment will be described with reference to FIGS. 6 to 8. FIG. FIG. 6 is a block diagram for explaining the configuration of the computer 3 according to this embodiment. FIG. 7 is a diagram showing an example of the correlation information DB 351 according to this embodiment. FIG. 8 is a diagram showing a γe-Fc plot diagram and an approximate curve corresponding to the correlation information DB 351 according to this embodiment.

The computer 3 is an example of an information processing unit, and includes a processor 31 configured as a CPU or GPU, a main memory 32 configured by a DRAM or the like for temporarily storing data and programs, and a user or the like. It includes an input/output unit 33 for exchanging data, a communication unit 34 for controlling wired or wireless communication, and a storage 35 configured by a magnetic disk, flash memory, or the like and storing data and programs.

The processor 31 loads a program stored in the storage 35 or the like into the main memory 32 and executes instructions included in the program.

The input/output unit 33 includes, for example, an information input device such as a keyboard, mouse, and touch panel, an audio input device such as a microphone, an image input device such as a camera, an image output device such as a display, and an audio output device such as a speaker. .

The communication unit 34 is implemented as hardware such as a network adapter, various types of communication software, or a combination thereof. In this embodiment, the communication unit 34 communicates with external devices such as the rotational rheometer 2 .

The storage 35 stores various information for predicting the humic acid content of the ground, and has, for example, a correlation information DB 351 indicating the correlation between the yield strain γe and the humic acid content Fc. Also, at least part of the correlation information DB 351 may be managed by a device other than the computer 3 .

The correlation information DB 351 is a database for generating Equation (1) for calculating the estimated humic acid content Fcr, which will be described later. As shown in FIG. Data showing the correlation between the humic acid content Fc and the yield strain γe of a soil sample (hereinafter referred to as “improved soil sample”), that is, the numerical value of each humic acid content Fc and each humic acid content Fc Measured data relating to each yield strain γe value corresponding to the value of is stored.

Here, properties of a plurality of improved soil samples, a preparation method thereof, and acquisition of yield strain γe of each of the plurality of improved soil samples will be described. Among the plurality of modified soil samples, at least some of the modified soil samples have a humic acid content Fc different from that of other modified soil samples. In addition, such modified soil samples are obtained by preparing in advance a plurality of humic acid-free modified soil samples having a humic acid content Fc of approximately 0, and then artificially adding various amounts of humic acid (humic acid (including those with an acid content of "0") into modified soil samples containing no humic acid. That is, the humic acid content Fc of each modified soil sample is obtained in advance. Preparation of such modified soil samples can be performed by various methods. For example, first, a soil sample classified as silt obtained from boring conducted in a consolidation test in a ground survey is frozen at -30 ° C., and freeze-dried at a shelf temperature of 0 ° C. to produce freeze-dried silt. do. Then, a predetermined amount of powdery humic acid is added to the freeze-dried silt, and after stirring and homogenizing, a predetermined amount of water is added and sufficiently mixed and kneaded to obtain a constant moisture content. Prepare an improved soil sample with After that, the prepared modified soil sample is stored in a refrigerator at 4° C. overnight or longer to complete the preparation of the modified soil sample. Further, the method for obtaining the yield strain γe of the modified soil sample is obtained by the rotational rheometer 2 according to the present embodiment described above, so detailed description thereof will be omitted. Note that the preparation of the plurality of modified soil samples and the acquisition of the yield strain γe of each of the plurality of modified soil samples according to the present embodiment described above need only be performed once in advance.

The processor 31 also includes a correlation equation generation unit 311 that executes processing related to generation of a mathematical formula for estimating the humic acid content of the ground by executing instructions included in a program stored in the storage 35 or the like. , and a humic acid content rate estimating unit 312 that executes processing related to calculation of the estimated humic acid content rate Fcr of the ground.

Correlation formula generator 311 generates the following formula (1).
Fcr(%)=2976.55*γe−24.81 (1)

More specifically, the correlation formula generation unit 311 first acquires the measurement data stored in the correlation information DB 351, and uses the measurement data to generate the γe-Fc plot and approximate curve as shown in FIG. to generate Then, the correlation formula generation unit 311 generates Equation (1), which is the above approximation formula, by exponential approximation of this approximation curve. Also, the coefficient of determination R2 in this case is 0.85. Unless the measurement data stored in the correlation information DB 351 is changed, the correlation formula generator 311 generates and stores the above formula (1) only once. In other words, the correlation formula generator 311 does not need to generate Equation (1) every time it calculates the estimated humic acid content Fcr. On the other hand, when the measurement data stored in the correlation information DB 351 is changed, the correlation formula generating section 311 may generate Formula (1) again based on the method for generating Formula (1) described above.

The humic acid content rate estimator 312 estimates the estimated humic acid content rate Fcr of the ground to which the soil sample belongs, using the yield strain γe of the soil sample. In this case, the humic acid content rate estimator 312 substitutes the yield strain γe of the soil sample into the above equation (1) to calculate the estimated humic acid content rate Fcr.

Thus, the computer 3 according to the present embodiment uses the yield strain γe of the soil sample to estimate the estimated humic acid content Fcr of the ground to which the soil sample belongs. In the following description, "humic acid content Fc" may be referred to as "actual humic acid content Fc" in order to distinguish from estimated humic acid content Fcr. Moreover, when the "estimated humic acid content rate Fcr" and the "humic acid content rate Fc" are not distinguished, both may be collectively referred to as the "humic acid content rate F". Furthermore, for convenience of explanation, "estimating the estimated humic acid content Fcr of the ground" is simplified as "estimating the humic acid content of the ground" or "estimating the humic acid content of the ground". Sometimes.

<Estimation process of the humic acid content rate of the ground by the soil discrimination system 1>
Subsequently, the process of estimating the humic acid content of the ground by the soil discrimination system 1 according to this embodiment will be described with reference to FIG. 9 . FIG. 9 is a flowchart for explaining the estimation of the humic acid content of the ground by the soil discrimination system 1 according to this embodiment.

Here, before explaining the estimation of the humic acid content of the ground by the soil discrimination system 1, first, the correlation between the yield strain γe and the humic acid content Fc will be explained by taking organic soil as an example. The yield strain γe is the shear strain γ at the boundary between elastic and inelastic deformation of the soil, ie the elastic limit of the soil. The humic acid content Fc is the clay content in the soil.

Soils include types such as marsh and silt. The organic soil according to this example has, for example, plant-derived clay. Humic acid is the main component of viscous substances. On the other hand, the silt according to this example is, for example, mainly composed of minerals. A shear stress is applied to each of such organic soils and silts to obtain respective storage modulus-shear strain curves. In this case, the length in the γ-axis direction of the storage modulus-shear strain curve storage modulus plateau region of the storage modulus-shear strain curve for organic soil is the storage modulus-shear strain curve storage modulus plateau region length for silt. longer than the length in the strain γ-axis direction. Therefore, the yield strain γe1 of organic soil is larger than the yield strain γe2 of silt. That is, the yield strain γe1 of organic soil with a high humic acid content Fc is larger than the yield strain γe2 of silt with a lower humic acid content Fc than organic soil. That is, the soil humic acid content Fc and the yield strain γe have a direct proportional correlation. Therefore, by measuring and obtaining the yield strain γe of the organic soil, it is possible to estimate the humic acid content (estimated humic acid content Fcr) that correlates with the yield strain γe of the organic soil.

The description will return to the process of estimating the humic acid content of the ground by the soil discrimination system 1 according to the present embodiment.
First, a soil sample is prepared (S10).

In this embodiment, a soil sample is prepared by collecting soil from the ground from which the humic acid content of the ground is to be estimated. Specifically, for example, a soil sample, which is organic soil, is collected from a test hole of an SWS tester from a sampling position where the humic acid content of the ground is to be estimated. Then, the collected soil sample is immediately sealed in a polyethylene bag and stored in a cool and dark place. Note that the depth of the soil sample sampling position changes depending on the specifications such as the weight of the building to be built on the ground. For example, when building a detached house with a weight of about 2 t/m 2 , the depth of the soil sample collection position should be in the range of about 0 m or more and 5 m or less. In other words, the position for collecting a soil sample is not limited to a position at a certain depth in the ground, but may be a shallow position in the ground, or may be the surface of the ground.

Here, the soil sample according to this embodiment will be described in detail. First, types of soil samples according to this embodiment will be described with reference to FIGS. The soil sample according to the present embodiment is organic soil (for example, humus soil) used for estimating the humic acid content of the board. Also, from the viewpoint that different types of soil have different yield strains, as shown in FIGS. 05 or more, and the yield strain γe of the silty soil related to the measurement IDs 30 to 112 is distributed in a range of approximately 0.05 or less. Therefore, the soil sample according to the present embodiment is soil having a yield strain γe of about 0.05 or more.

Next, a soil sample is installed (S11).

In this embodiment, a soil sample is placed in the measuring section 10 of the rotary rheometer 2 . Specifically, the soil sample prepared in step S10 is put on the concave portion 18 of the lower measuring portion 10b of the measuring portion 10 so as to exceed the projection height of the fence 16. As shown in FIG. Then, the surface of the soil sample placed on the concave portion 18 is lightly smoothed with a spatula, and the top surface of the soil sample is made to match the height of the projection of the fence 16. - 特許庁

Subsequently, shear stress is applied to the soil sample (S12).

In this embodiment, the soil discrimination system 1 uses the upper sensor 11 of the rotary rheometer 2 to gradually increase the shear stress acting on the soil sample placed in the recess 18 of the lower measurement part 10b in step S11. Apply so that

Specifically, the controller 20 of the rotary rheometer 2 controls the application of shear stress to the soil sample by the upper sensor 11 . For example, the control unit 20 first brings the upper sensor 11 into contact with the soil sample so that the vertical load applied by the upper sensor 11 to the soil sample is 5N. Then, the control unit 20 rotates the upper sensor 11 forward and backward with respect to the soil sample so that the shear stress applied to the soil sample by the upper sensor 11 increases linearly from 10 Pa and the frequency becomes 1 Hz. And the oscillating sine waves are made to intersect. In this case, the application of shear stress by the upper sensor 11 is stopped when the upper sensor 11 starts to slip. That is, when the soil sample transitions from the first state in which the soil sample is elastically deformed to the second state in which it is plastically deformed, the measurement of the soil sample by both sensors ends.

In addition, the soil discrimination system 1 causes the upper sensor 11 to apply shear stress to the soil sample, and uses the upper sensor 11 and the lower sensor 12 to determine the storage elastic modulus G′ of the soil sample and its storage elasticity due to the increase in shear stress. Data are measured on the change in shear strain γ as a function of modulus G′. Then, the soil discrimination system 1 uses the control unit 20 of the rotational rheometer 2 to store the measured data and generate a storage modulus-shear strain curve.

Next, the yield strain γe of the soil sample is obtained (S13).

In this embodiment, the soil determination system 1 uses the controller 20 of the rotational rheometer 2 to acquire the yield strain γe from the storage modulus-shear strain curve generated in step S12. Specifically, the control unit 20 uses the storage modulus-shear strain curve of the soil sample, for example, to correspond to a second value that is about 5% lower than the first value, the storage modulus Gp′ in the plateau region. The shear strain γ applied is obtained as the yield strain γe.

After that, the estimated humic acid content Fcr of the ground to which the soil sample belongs is estimated (S14).
In this embodiment, the soil discrimination system 1 estimates the estimated humic acid content Fcr of the ground to which the soil sample belongs, using the yield strain γe of the soil sample whose soil is to be discriminated. In this case, the computer 3 of the soil discrimination system 1 calculates the estimated humic acid content rate Fcr by Equation (1).

This completes the estimation of the estimated humic acid content Fcr of the ground to which the soil sample belongs.

In the step of estimating the humic acid content of the ground by the soil discrimination system 1 according to this embodiment, the amount of soil sample required for each estimation is about 10 cm ³ . Moreover, the time required to complete the estimation of the estimated humic acid content F _cr of the ground to which the soil sample belongs after placing the soil sample in the rotational rheometer 2 is about 10 minutes. Therefore, the estimation of the humic acid content of the ground by the soil discrimination system 1 according to this embodiment can be performed quickly and easily.

<Verification of estimation accuracy of ground humic acid content rate by soil discrimination system 1>
Next, with reference to FIGS. 12 and 13, the accuracy of estimating the humic acid content of the ground by the soil discrimination system 1 according to this embodiment will be verified.

Here, FIG. 12 is a diagram for explaining the estimation accuracy of the humic acid content rate by the soil discrimination system 1 according to this embodiment. Here, the data related to each comparison ID shown in FIG. include. “Fc (%)” includes the actual humic acid content Fc of each modified soil sample whose humic acid content Fc has been obtained in advance. "γe (%)" includes the yield strain γe of each modified soil sample (for example, the yield strain γe obtained by the rotational rheometer 2). "Fcr (%)" includes the estimated humic acid content Fcr of each improved soil sample estimated using the yield strain γe of each improved soil sample. "Fc/Fcr" includes the value of Fc/Fcr between the estimated humic acid content Fcr and the actual humic acid content Fc of each modified soil sample. Further, FIG. 13 is a plot diagram of part of the data of FIG. 12, and explains the relationship between the estimated humic acid content Fcr by the soil discrimination system 1 according to the present embodiment and the actual humic acid content Fc. It is a figure for doing. The straight line shown in FIG. 13 indicates the case where the estimated humic acid content Fcr and the actual humic acid content Fc match.

By the way, when constructing a building on the ground that is determined to be soft ground by a ground survey, it is necessary to first improve the soft ground. Ground improvement can be carried out by various methods, one of which is to use a solidifying material such as ordinary cement (hereinafter referred to as "cement") to soften the ground. It is a method of solidifying (consolidating). In this method of improving the ground using cement, the cement is poured into the soft ground to solidify the ground through the hydration reaction of the cement. Specifically, in this method, Ca2+ eluted from cement reacts with water contained in soft ground to produce hydrated minerals, which contributes to the development of strength of the solidified material and promotes solidification of the ground. enable realization.

On the other hand, when the humic acid content Fc of the soft ground exceeds a certain value, the Ca2+ eluted from the cement is dissolved in the humic acid to form calcium chloride CaCl2. Such calcium chloride CaCl2 is deposited on the surface of unhydrated cement particles. As a result, the hydration reaction of cement is hindered, resulting in poor solidification of the ground. That is, when the humic acid content Fc of the soft ground exceeds a certain value, there arises a problem of poor solidification of the ground due to poor solidification of the cement. Here, the "constant numerical value" of the humic acid content Fc varies depending on the properties of the soil of the soft ground, the solidification material used, and the like. For example, when improving soft ground composed of ordinary soil using ordinary cement (hereinafter referred to as "soil improvement with ordinary cement"), the humic acid content Fc of the soft ground is about When it is 1% or more, there is a high possibility that cement hardening failure will occur. In other words, when the humic acid content Fc of the soft ground is approximately 1% or less, it can be said that poor solidification of cement is unlikely to occur.

Therefore, if the Fc/Fcr value of the estimated humic acid content Fcr relative to the actual humic acid content Fc is about 1% or less, poor solidification of ground improvement with ordinary cement can be suppressed.

For these reasons, below, one of comparison data between the estimated humic acid content Fcr by the soil discrimination system 1 according to the present embodiment and the actual humic acid content Fc corresponding to the estimated humic acid content Fcr By analyzing whether each value of Fc/Fcr is about 1% or less, the accuracy of estimating the humic acid content of the ground by the soil discrimination system 1 is verified.

As shown in FIGS. 12 and 13, in the eight cases of comparative data, those with a Fc/Fcr value of 1% or less between the estimated humic acid content Fcr and the actual humic acid content Fc are comparative IDs 1 and 2. , 5 and 6. In addition, there are two cases with comparison IDs 3 and 7 having a Fc/Fcr value of approximately 1%. As such, 75% of the comparative data falls within a range of about 1% or less. Furthermore, among the comparison data this time, the Fc/Fcr value of comparison ID4, which has the largest Fc/Fcr value, is 1.31%, which is close to 1%. That is, the eight estimated humic acid contents Fcr predicted by the soil discrimination system 1 according to the present embodiment are generally within a practical range. Therefore, the estimation of the humic acid content rate of the ground by the soil discrimination system 1 can estimate the estimated humic acid content rate Fcr of the ground with high accuracy, and is used for soil discrimination for actually building a detached house. Is possible.

Thus, in the present embodiment, the estimated humic acid content of the ground to which the soil sample belongs can be obtained only by obtaining the yield strain γe of the soil sample by estimating the humic acid content of the ground, which has the characteristics described above. It becomes possible to calculate the rate Fcr. Therefore, in the present embodiment, it is possible to easily and quickly estimate the humic acid content of the ground.
In addition, the numerical value of Fc/Fcr in the result of estimating the humic acid content of the ground according to this embodiment is generally within a practical range. Therefore, the estimation result of the humic acid content of the ground has high accuracy and reliability. Therefore, the estimation of the humic acid content of the ground according to this embodiment can be used to predict the amount of ground subsidence for actually building a detached house.
In addition, since the soil sample necessary for estimating the humic acid content of the ground according to this embodiment is only about 10 cm3, the soil sample can be collected with a simple device such as an SWS investigation machine. , it is possible to suppress the labor and cost burden associated with preparing a dedicated sampling device and preparing a large amount of soil samples, etc., and it is possible to easily prepare for estimating the humic acid content of the ground.
In addition, since the time required for estimating the humic acid content of the ground according to the present embodiment is only about 10 minutes, the estimation result of the estimated humic acid content of the ground Fcr can be quickly obtained. Therefore, ground improvement work, building construction, etc. can be efficiently carried out based on the estimation result of the humic acid content of the ground, and it is possible to improve the economic effect and profit by estimating the humic acid content of the ground. can.
Further, since the operation for estimating the humic acid content of the ground according to the present embodiment is only to install the prepared soil sample in the rotational rheometer 2, the operation for estimating the humic acid content of the ground is simplified, it is possible to reduce the ingenuity and costs related to the estimation of the humic acid content of the ground, and it is possible to suppress the inaccuracy of the estimation results due to operational errors and the like.
Therefore, estimating the humic acid content of the ground from the yield strain γe of the soil sample according to this embodiment can obtain a simple and highly accurate estimation result.

[Modification]
The present invention is not limited to the above embodiments and can be applied in various modifications. Modifications according to the present invention will be described below.

In the above embodiment, the shear stress is applied to the soil sample by the rotary rheometer 2, but the configuration is not limited to the above. It can be anything that exists.

In the above embodiment, the computer 3 is provided outside the rotational rheometer 2. However, the computer 3 is not limited to the above configuration, and may be a device capable of measuring the shear strain γ of a soil sample. .

In the above embodiment, the method for improving soft ground is described as being performed using ordinary cement, but the configuration is not limited to the above, and various solidification materials other than ordinary cement may be employed. . For example, the improving material may be one of a special cement, a mixed hardening material of ordinary cement and gypsum, slaked lime, and a mixed hardening material of slaked lime and gypsum. Also, the mixed consolidation material may mix the components in various ratios.

In the above embodiment, when calculating the estimated humic acid content F _cr , the yield strain γ _e obtained by the rotational rheometer 2 is used as it is for calculating the estimated humic acid content F _cr , but the above method is not limited to For example, a predetermined amount of adjustment may be made to the yield strain γ _e obtained by the rotational rheometer 2 . In this case, the estimated humic acid content F _cr may be calculated using the yield strain γ _e after adjustment. Also, the yield strain γ _e may have a certain tolerance.

In the above embodiment, the storage 35 is described as having the correlation information DB 351, but the configuration is not limited to the above, and the storage 35 may have a different information DB or other information DB. For example, the storage 35 may further have an information DB regarding special soil in addition to the correlation information DB 351 .

In the above embodiment, the soil sample was explained as being collected by the SWS tester, but the configuration is not limited to the above, and it may be collected by a different method.

In the above embodiment, the fence 16 has been described as being attached to the lower sensor 12, but the configuration is not limited to the above. can have any size, shape, and mounting position. For example, fence 16 may be attached to upper sensor 11 . Moreover, fences with different dimensions may be attached to both the upper sensor 11 and the lower sensor 12 . Furthermore, the fence 16 may have a shape other than the ring shape.

The embodiments described above are for facilitating understanding of the present invention, and are not intended to limit and interpret the present invention. Each element included in the embodiment and its arrangement, materials, conditions, shape, size, etc. are not limited to those illustrated and can be changed as appropriate. Also, it is possible to partially replace or combine the configurations shown in different embodiments.

DESCRIPTION OF SYMBOLS 1... Soil discrimination measurement system, 2... Rotary rheometer, 3... Computer, 10... Measurement part, 10a... Upper measurement part, 10b... Lower measurement part, 11... Upper sensor, 12... Lower sensor, 13... Rod, 14... Lower plate 16 Fence 18 Recess 20 Control unit 211 Stress application unit 212 Yield strain acquisition unit 311 Correlation equation generation unit 312 Humic acid content rate estimation unit

Claims (12)

a stress applying step of applying shear stress to the soil sample;
Yield strain, which is the shear strain at the boundary between the first state and the second state when the soil sample is about to transition from the first state in which the soil sample elastically deforms to the second state in which the soil sample deforms inelastically due to the shear stress A yield strain acquiring step of acquiring
a humic acid content estimation step of estimating the estimated humic acid content of the ground to which the soil sample belongs using the yield strain;
including,
Soil discrimination method. 2. The soil quality determination method according to claim 1, wherein said stress applying step includes gradually increasing shear stress on the soil sample by sinusoidal vibration or unidirectional rotational motion. 3. The soil quality determination method according to claim 1, wherein the stress applying step includes applying a shear stress to the soil sample using a rheometer. The yield strain acquiring step yields a shear strain corresponding to the second value when the storage modulus of the soil sample decreases from a first value, which is a constant value, to a second value due to the shear stress. 4. The soil quality determination method according to any one of claims 1 to 3, wherein the second value is a numerical value lower than the first value by 2% or more and 20% or less. 5. The soil quality determination method according to claim 4, wherein said second value is a numerical value that is 5% lower than said first value. The humic acid content rate estimation step includes calculating the estimated humic acid content rate corresponding to the yield strain using a pre-calculated correlation equation between the yield strain of soil and the humic acid content rate. Item 6. The method for determining soil characteristics according to any one of Items 1 to 5. 7. The soil quality determination method according to claim 6, further comprising a correlation equation generation step of generating said correlation equation using a plurality of modified soil samples, at least some of which have different humic acid contents. In the step of generating a correlation equation, obtaining the yield strain of each of the plurality of modified soil samples through the step of applying stress and the step of obtaining yield strain;
generating the correlation equation using the yield strain of each of the plurality of modified soil samples and the humic acid content of each of the plurality of modified soil samples;
The soil discrimination method according to claim 7, comprising: 9. The method of discriminating soil properties according to claim 7, wherein said correlation equation generating step is a step performed before said humic acid content rate estimating step. The soil quality determination method according to any one of claims 7 to 9, wherein the correlation formula generation step is a step performed only once. causing one or more computers to perform processing using the soil discrimination method according to any one of claims 1 to 10;
A soil discrimination program for predicting the humic acid content of ground. An information processing unit that executes processing related to the soil determination method according to any one of claims 1 to 10,
Soil classification system.

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