JP7464299B2 - Ground improvement methods - Google Patents

Description

The present invention relates to a ground improvement method for checking the mixing status of a ground improvement body when constructing the ground improvement body in the ground.

A well-known ground improvement method is the deep mixing method, in which cement slurry is injected into the ground and mixed mechanically to create a ground improvement body in the ground. In this type of method, to ensure the quality of the ground improvement body, it is necessary for the cement to be distributed evenly throughout the ground improvement body, and it is also necessary to confirm that the cement has been distributed evenly throughout the ground improvement body.

The amount of cement used in on-site construction is determined by the results of mix tests carried out in the laboratory, but these tests must also ensure that the cement is distributed evenly.

However, when the soil and cement slurry are mixed, as described below with reference to Figure 7, both the soil and the cement slurry are the same color (almost gray) and cannot be distinguished from each other.

Therefore, even if the mixture is illuminated with a normal light source that emits visible light, such as a fluorescent lamp, and observed visually or with a camera or other device, it is extremely difficult to determine whether there is uneven mixing or whether the mixture is good or bad.

Patent Document 1 (Patent Publication No. 6944605) proposes a method for checking the condition of a ground improvement body by (1) comparing the brightness of an image taken before and after improvement of the ground, or (2) comparing it with a known image of the ground condition taken in the past.

However, because black soil and gray cement are mixed, the difference in brightness is small, making it difficult to distinguish between the two. Also, deep underground, lighting is required, making it difficult to accurately judge the state of the mixture.

Patent Document 2 (Patent Publication No. 4,886,921) discloses a method of spraying a colored hardener and checking the degree of mixing within the ground improvement body based on the distribution of the hardener.

However, when colored hardener is sprayed on such black soil, it remains almost black, as described above, and the difference in brightness is insufficient, making it difficult to distinguish between the two. Also, deep underground, lighting is required, making it difficult to accurately determine the mixed state.

Furthermore, non-patent document 1 (The Building Center of Japan, "Guidelines for Design and Quality Control of Improved Ground for Buildings, 2018 Edition") describes a method of observing an alkaline reaction (reddish purple color) by spraying a phenolphthalein solution during agitation status inspection.

The discoloration of phenolphthalein occurs under alkaline conditions of pH > 10.0, and is an indication of the mixed state of cement based on the principle that phenolphthalein changes color in areas where cement is present.

Here, confirmation using phenolphthalein is carried out by taking advantage of the phenomenon in which areas containing cement, an alkaline component, turn reddish purple.

However, in reality, the phenolphthalein solution tends to seep out or drip into the surrounding area, causing discoloration in areas that should not be discolored. As a result, the boundary between areas that contain cement and areas that do not contain cement becomes unclear, making it difficult to properly determine the mixing state.
Patent No. 6944605 Patent No. 4886921 The Building Center of Japan "2018 Edition: Design and Quality Control Guidelines for Improved Ground for Buildings"

Therefore, the present invention aims to provide a ground improvement method that can clearly distinguish between areas that contain cement slurry and areas that do not.

The ground improvement method according to the first invention is a method for constructing a ground improvement body by mixing soil with a cement slurry to which a water-soluble fluorescent dye of a predetermined concentration has been added, and includes a first step of irradiating the ground improvement body with black light from a light source, a second step of measuring the ground improvement body irradiated with black light from the light source using a measuring device, and a third step of comparing a calculated value based on data output by the measuring device with a predetermined threshold value to determine whether the cement slurry is in a mixed state.

Here, black light, which is different from visible light, is irradiated onto the ground improvement body, and a measuring instrument is used to measure the ground improvement body irradiated with black light from a light source, making it possible to clearly distinguish between areas that contain cement slurry and areas that do not. Furthermore, the mixed state of the cement slurry is judged based on a clear criterion of comparing a calculated value based on data output by the measuring instrument with a predetermined threshold value. Here, even underground, the water-soluble fluorescent dye irradiated with black light emits light smoothly, allowing the state to be correctly recognized. Furthermore, the results are not unstable due to complex processing or external disturbances.

Here, the measuring instrument may be a sensor that captures reflected light from the ground improvement body, or a camera that takes an image of the ground improvement body.

The wavelength of the black light is preferably between 365 and 405 nanometers, making it easier to secure a light source.

Preferably, the soil is soil at a construction site, and steps 1, 2 and 3 are carried out when the ground improvement body has not yet solidified.

With this configuration, it is possible to carry out ground improvement work on-site while simultaneously determining whether the cement slurry is mixed properly.

Preferably, the soil is a soil prepared in a laboratory, the first, second and third steps are performed in the laboratory, and the third step is performed for the purpose of determining an appropriate amount of cement to be added.

With this configuration, when determining the appropriate amount of cement to be added in a laboratory, it is possible to accurately determine the amount of cement to be added while clearly distinguishing between areas that contain cement slurry and areas that do not.

According to the present invention, it is possible to clearly distinguish between areas containing cement slurry and areas not containing it, and to determine whether the cement slurry is mixed or not based on clear criteria, by comparing a calculated value based on data output by a measuring instrument with a predetermined threshold value. This makes it possible to make a determination that is not adversely affected by factors such as the shooting conditions, the color of the soil, or the degree of lighting.

(Embodiment 1)
Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Fig. 1(a) is a side view of a ground improvement device in the first embodiment of the present invention, Fig. 1(b) is a partial view showing a mixing head replacement procedure, Fig. 2(a) is a side view showing the state in which the ground improvement device checks the mixing state, and Fig. 2(b) is a partially enlarged cross-sectional view of the inspection head of the ground improvement device.

Embodiment 1 relates to a case in which a cylindrical ground improvement body is constructed from soil S at a relatively deep location using a ground improvement device (column construction machine) as shown in Figure 1.

As shown in FIG. 1, this ground improvement device comprises a base machine 1 that travels on the ground G, a leader 2 that is positioned in front of the base machine 1 and stands vertically when in operation, a drive unit 10 that is supported by the leader 2 so that it can be raised and lowered freely and has an actuator such as a motor, a rotating shaft 3 that is given a rotational force by the drive unit 10 and rotates horizontally around a vertical axis in the ground, and a mixing head 4 that is attached to the lower end of the rotating shaft 3.

The mixing head 4 attached to the tip of the rotating shaft 3 is equipped with the following elements. First, at the lower end of the mixing head 4, there is a drilling blade 5 that has a claw for digging into the ground and excavates soil and sand, and this drilling blade 5 is attached to the rotating shaft 3. As shown in Figure 1 (b), it is desirable to provide a mixing blade 12 and a co-rotation prevention blade 11 above the drilling blade 5 on the mixing head 4, but these are not essential and may be omitted.

The type of cement may be selected as usual. Next, a water-soluble fluorescent dye is added to the cement slurry. Suitable water-soluble fluorescent dyes include strontium borofluoride with a small amount of europium added (SrB4O7F:Eu2+, peak wavelength 368-371 nm), barium silicide with a small amount of lead added (BaSi2O5:Pb+, peak wavelength 350-353 nm), fluorescein, and quinine sulfate.

More specifically, it is sufficient to use a commercially available fluorescent leak inspection agent (for example, Superglow fluorescent leak inspection agent DF-300 (trademark) manufactured by Marktec Co., Ltd.), and the concentration of the fluorescent dye in water should be 0.05 to 20 (%). Note that there is usually no need to change the water-soluble fluorescent dye depending on the type of cement.

Next, as shown in FIG. 1(a), the mixing head 4 of the excavation and mixing device is set to an initial position close to the ground surface G, and the drive unit 10 is started to operate, rotating the rotating shaft 3. In this way, the excavation blade 5 is brought to the initial depth H1.

Next, below the initial depth H1, the slurry is discharged from the base of the drilling blade 5, and excavation and mixing is performed by the mixing head 4. As described above, unlike normal, the slurry contains added water-soluble fluorescent dye, so the water-soluble fluorescent dye is also mixed into the ground improvement body to be constructed. This state continues until the target depth H2 (the lowest part of the ground improvement body to be constructed) is reached.

Then, the mixing head 4 is rotated and raised (pulled up) until it reaches the ground, creating a cylindrical ground improvement body in the ground using the on-site soil S.

Once the ground improvement body has been constructed, the mixing head 4 is replaced with the inspection head 14 and attached to the device while it is still wet.

2(b) is a cross-sectional view of the lower part of the inspection head 14. The lower part and the side of the inspection head 14 are partially recessed to form a storage chamber 14a. Inside the storage chamber 14a, a pair of a light source 6 and a measuring instrument 7 is stored, each facing outward on the side. The storage chamber 14a may be configured to open downward. The light source 6 may be any type of fluorescent lamp, incandescent lamp, mercury lamp, or LED that irradiates the ground improvement body with black light (wavelength: 365 to 405 nanometers) underground, but LEDs are small and easy to use. The measuring instrument 7 may be any type of sensor such as a fluorescent photometer or a camera equipped with an image sensor that measures the ground improvement body irradiated with black light by the light source 6, but in the first embodiment, it is a sensor. Details of the light emission rate will be described later with reference to FIG. 6.

Furthermore, a transparent or translucent protective cover 14b is attached to the opening of the storage chamber 14a, sealing the storage chamber 14a and protecting the light source 6 and measuring instrument 7 from the surrounding soil and slurry. The protective cover 8 can be suitably constructed of a resin plate such as acrylic or a plate of reinforced glass. Therefore, the light source 6 and measuring instrument 7 rise and fall together with the rotating shaft 3. The inspection head 14 is axially attached to the rotating shaft 3, but the rotating shaft 3 may or may not be rotated when the inspection head 14 is raised and lowered. The test attachment of Patent No. 6742633 can also be applied.

(Embodiment 2)
Figure 3 is a side view of a ground improvement device in embodiment 2 of the present invention, Figure 4(a) is a side view showing the ground improvement device inspecting the mixed state, and Figure 4(b) is an enlarged cross-sectional view of a portion of the inspection head of the ground improvement device.

Embodiment 2 relates to the case where a flat ground improvement body is constructed at a relatively shallow depth using on-site soil S using the ground improvement device (vertical construction machine) shown in Figure 2.

As shown in FIG. 3, this ground improvement device includes a main body 21 that travels on the ground G, and an operating unit 20 that rotates vertically in a vertical plane to eject the cement slurry and mix it with the soil S.

The preparation of the cement and the water-soluble fluorescent dye added to it are the same as in the first embodiment. After the ground improvement body is constructed, an inspection head similar to the inspection head 14 in the first embodiment, as shown in FIG. 4(b), is attached to the tip of the operating unit 20 to inspect the mixed state of the cement. Details of the light emission rate will be described later with reference to FIG. 6.

(Embodiment 3)
5(a) to 5(d) show the steps of a method according to a third embodiment of the present invention.

The third embodiment is carried out for the purpose of constructing a simulated ground improvement body using soil S prepared in a laboratory and determining the appropriate amount of cement to be added. The adjustment of the cement and the water-soluble fluorescent dye to be added to it are the same as in the first embodiment.

First, as shown in FIG. 5(a), the water-soluble fluorescent dye as described above is added to the cement slurry in a beaker 25, and then this is added to the soil S to obtain a mixture.

Next, as shown in FIG. 5(b), the mixture is placed in a container 27 and mixed and stirred using a mixer 28. Once thoroughly mixed, the mixed soil 30 is placed in a tray 29 having a specified volume, as shown in FIG. 5(c).

Next, as shown in FIG. 5(d), the vat 29 prepared as described above is placed in a darkroom 31. In the darkroom 31, a light source 6 that irradiates black light and a camera 7a that acts as a measuring device for photographing the mixed soil 30 in the vat 29 irradiated with black light from the light source 6 are placed.

Next, we will explain some actual photographed examples with reference to Figures 7 to 10. Figure 7 shows an example of a photograph taken in the state shown in Figure 5(d) using visible light (fluorescent lamps or sunlight may be used) without using a light source 6 that irradiates black light. This photograph may be in full color or in grayscale. A notable feature is that there is almost no difference in shading across the entire screen, making it difficult to distinguish between light and dark.

On the other hand, Figure 8 is a photograph of the exact same object as Figure 7, taken in the same way using black light (wavelength: 365 to 405 nanometers) emitted by a light source 6 rather than visible light. This photograph may be in full color or grayscale. A notable feature is that the difference in shading is more pronounced across the entire screen than in Figure 7, making it easier to distinguish between light and dark.

When the image in Figure 7 (which is assumed to be full color here) is converted to grayscale, it becomes as shown in Figure 9, and when this is further converted to black and white, it becomes as shown in Figure 10. To reduce the number of colors, any well-known method can be used, such as approximate colors, patterns, error diffusion, etc.

When using camera images, data is usually obtained on a two-dimensional plane, so it is desirable to calculate the light emission rate (%) in pixel units. That is, in the example of Figure 10, the total number of pixels A is 236672 pixels, and the number of pixels B in the white part is 1641778 pixels, so the light emission rate (%) = (A/B) * 100 = (1641778/2336672) * 100 = 70 (%).

In the third embodiment, TH=80(%) is used as the threshold value for determining whether the light emission rate (%) is good or bad. Needless to say, this value is merely an example, and it must be understood that even if a higher or lower threshold value is used, it falls within the scope of protection of the present invention. Therefore, in the above numerical example, the light emission rate is insufficient, and the mixed state is rejected. In other words, the amount of solution in the beaker 25 relative to the soil S should be increased. On the other hand, if the light emission rate is 80(%) or more, the mixed state is confirmed.

As mentioned above, the following points are common to the first to third embodiments:

In terms of the third embodiment, when constructing a ground improvement body 30 by mixing a cement slurry 26 to which a predetermined concentration of water-soluble fluorescent dye has been added with soil S, the method includes a first step of irradiating the ground improvement body 30 with black light from a light source 6, a second step of measuring the ground improvement body 30 irradiated with black light from the light source 6 using a measuring device 7a, and a third step of comparing a calculated value based on the data output by the measuring device 7a with a predetermined threshold value to determine whether the cement slurry is mixed.

The wavelength of the black light emitted by light source 6 is 365 to 405 nanometers.

In the first and second embodiments, the soil S is soil at the construction site, and the first, second and third steps are carried out when the ground improvement body has not yet solidified.

In the third embodiment, the soil S is soil prepared in a laboratory, the first, second and third steps are performed in the laboratory, and the third step is performed for the purpose of determining an appropriate amount of cement to be added.

The configuration of the information processing device in the facilities of the first to third embodiments will be described with reference to FIG. 6. FIG. 6 is a functional block diagram of the information processing device in the first to third embodiments of the present invention. First, the light source 6, measuring instrument 7, etc. are as already described.

The memory unit 40 of this device consists of storage such as a memory or hard disk for storing control programs (including well-known processes for image processing) and various data to be temporarily stored.

The control unit 41 is composed of a processor etc., and executes the control program stored in the memory unit 40 and controls the peripheral elements.

The monitor 42 is a display that shows the operating status to the user.

The interface 43 is controlled by the control unit main body 21 to turn the light source 6 on and off and input the measurement value (measurement signal) from the measuring instrument 7.

Next, we will explain the light emission rate calculated by the light emission rate calculation unit 44.

As already explained with reference to FIG. 10, in the third embodiment, when the total number of pixels is A and the number of pixels in the white portion is B,
Luminescence rate (%) = (A / B) * 100 (%) (1)
And it is sufficient.

In the first and second embodiments, the measuring device 7 moves linearly, so it is best to use distance.

If the distance the inspection head 14 moves is L and the distance at which the measuring device 7 captures the reflected light is l, then
Luminescence rate = (l / L) * 100 (%) (2)
And it is sufficient.

Of course, the above formulas are merely examples, and it goes without saying that various different formulas or equivalent formulas can be used as long as they do not change the spirit of the present invention.

(a) A side view of the ground improvement device in the first embodiment of the present invention. (b) A partial view showing a method for replacing the mixing head in the first embodiment of the present invention. (a) A side view showing a state in which the excavation and stirring device in the first embodiment of the present invention checks the mixing state. (b) An enlarged cross-sectional view of a part of the inspection head of the excavation and stirring device in the first embodiment of the present invention. FIG. 11 is a side view of a ground improvement device according to a second embodiment of the present invention. (a) A side view showing a state in which the excavation and stirring device in the second embodiment of the present invention checks the mixing state. (b) An enlarged cross-sectional view of a part of the inspection head of the excavation and stirring device in the second embodiment of the present invention. (a) An explanatory diagram of each step in the third embodiment of the present invention. (b) An explanatory diagram of each step in the third embodiment of the present invention. (c) An explanatory diagram of each step in the third embodiment of the present invention. (d) An explanatory diagram of each step in the third embodiment of the present invention. A functional block diagram of an information processing device according to first to third embodiments of the present invention. Photograph of soil surface taken under natural light in the third embodiment of the present invention Photograph of soil surface taken with black light in embodiment 3 of the present invention FIG. 9 is a grayscale image of FIG. 8. FIG. 10 is a black and white binarized image of FIG. 9 .

REFERENCE SIGNS LIST 1 Base machine 2 Reader 3 Rotating shaft 4 Mixing head 5 Excavation blade 6 Light source 7 Measuring instrument 7a Camera 10 Driving unit 11 Co-rotation prevention blade 12 Mixing blade 14 Inspection head 14a Storage chamber 14b Protective cover 20 Operating unit 21 Main body 25 Beaker 26 Solution 27 Container 28 Mixer 29 Vat 30 Mixed soil 31 Darkroom 40 Memory unit 41 Control unit 42 Monitor 43 Interface 44 Luminescence rate calculation unit G Ground S Soil H1 Initial depth H2 Target depth

Claims (6)

A ground improvement method for constructing a ground improvement body by mixing soil with a cement slurry to which a water-soluble fluorescent dye of a predetermined concentration has been added,
A first step of irradiating the ground improvement body with black light from a light source;
A second step of measuring the ground improvement body irradiated with black light by the light source using a measuring instrument;
A ground improvement method comprising a third step of comparing a calculated value based on the data output by the measuring instrument with a predetermined threshold value to determine whether the cement slurry is in a mixed state. The ground improvement method according to claim 1, wherein the measuring instrument is a sensor that captures reflected light from the ground improvement body. The ground improvement method according to claim 1, wherein the measuring instrument is a camera that takes an image of the ground improvement body. The ground improvement method according to claim 1, wherein the wavelength of the black light is 365 to 405 nanometers. The ground improvement method according to claim 1, wherein the soil is soil at a construction site, and the first, second and third steps are carried out when the ground improvement body has not yet solidified. The ground improvement method according to claim 1, wherein the soil is prepared in a laboratory, the first step, the second step, and the third step are carried out in the laboratory, and the third step is carried out for the purpose of determining an appropriate amount of cement to be added.

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