Ground improvement method

Abstract

The present method is a ground improvement method with which a ground improvement body is constructed by mixing soil with cement slurry to which a water-soluble fluorescent dye at a predetermined concentration is added, the method comprising: 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 the black light by the light source using a measurement device; and a third step of comparing an emission rate obtained based on the data output by the measurement device with a predetermined threshold value and determining whether the mixed state of the cement slurry is acceptable.

Description

Ground improvement method

[0001] The present invention relates to a ground improvement method for checking the stirring and mixing status of a ground improvement body when constructing a ground improvement body in the ground.

[0002] Known ground improvement methods include the deep mixing method, in which cement slurry is injected into the ground and mixed mechanically to create a ground improvement body. In this method, to ensure the quality of the ground improvement body, it is necessary to ensure that the cement is evenly distributed throughout the ground improvement body, and it is also necessary to confirm that the cement has been evenly distributed throughout the ground improvement body.

[0003] 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 evenly distributed.

[0004] However, when the soil and the cement slurry are mixed, as will be described later with reference to FIG. 5, the soil and the cement slurry are both the same color (almost gray) and cannot be distinguished from each other.

[0005] 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 using a device such as a camera, it is extremely difficult to determine whether there is unevenness in the mixture or whether the mixture is good or bad.

[0006] 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 of the ground before improvement with that taken after improvement, or (2) comparing it with a known image of the ground condition taken in the past.

[0007] However, because black soil and gray cement are mixed, the difference in brightness is small, making it difficult to distinguish between them. In addition, lighting is required deep underground, making it difficult to accurately determine the state of the mixture.

[0008] Furthermore, Patent Document 2 (Japanese Patent No. 4886921) 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.

[0009] However, even if a colored hardener is sprayed on such dark soil, the soil remains almost black, and the difference in brightness is insufficient, making it difficult to distinguish between the two. Furthermore, lighting is required deep underground, making it difficult to accurately determine the mixing state.

[0010] Furthermore, Non-Patent Document 1 ("Guidelines for Design and Quality Control of Improved Ground for Buildings, 2018 Edition" by the Building Center of Japan) describes a method of observing an alkaline reaction (reddish-purple color) by spraying a phenolphthalein solution during agitation status inspection.

[0011] The discoloration of phenolphthalein occurs under alkaline conditions of pH > 10.0, and indicates the mixing state of cement based on the principle that phenolphthalein changes color in areas where cement is present.

[0012] Here, confirmation using phenolphthalein is carried out by utilizing the phenomenon in which areas containing cement, which is an alkaline component, turn reddish purple.

[0013] However, in reality, the phenolphthalein solution tends to seep out or drip into the surrounding area, discoloring areas that should not be discolored. As a result, the boundary between areas containing cement and areas without cement becomes unclear, which creates a problem of not being able to properly determine the mixing state. (Patent Publication No. 6944605, Patent Publication No. 4886921, The Building Center of Japan, "2018 Edition: Guidelines for Design and Quality Control of Improved Ground for Buildings")

[0014] Therefore, an object of the present invention is to provide a ground improvement method that can clearly distinguish between areas that contain cement slurry and areas that do not.

[0015] The ground improvement method of the first invention is a method for constructing a ground improvement body by mixing soil with cement slurry to which a predetermined concentration of water-soluble fluorescent dye 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 instrument, and a third step of comparing the luminescence rate calculated based on the data output by the measuring instrument with a predetermined threshold value to determine whether the cement slurry is mixed properly.

[0016] Here, black light, which is different from visible light, is irradiated onto the ground improvement body, and the ground improvement body illuminated with black light from a light source is measured using a measuring instrument, making it possible to clearly distinguish between areas containing cement slurry and areas that do not. Furthermore, the mixed state of the cement slurry is determined based on a clear standard: the luminescence rate calculated based on the data output by the measuring instrument is compared with a predetermined threshold. Here, even underground, the water-soluble fluorescent dye illuminated by 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.

[0017] 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.

[0018] The wavelength of the black light is preferably between 365 and 405 nanometers, which makes it easier to secure a light source.

[0019] Preferably, the soil is soil at a construction site, and steps 1, 2, and 3 are carried out using a boring core collected by boring after the soil improvement body has solidified. Alternatively, the soil is soil at a construction site, and steps 1, 2, and 3 are carried out in a vertical hole formed by boring after the soil improvement body has solidified.

[0020] According to this configuration, it is possible to determine whether the cement slurry is in a mixed state in the performed ground improvement work.

[0021] According to the present invention, it is possible to clearly distinguish between areas containing cement slurry and areas not containing cement slurry, and to determine whether the cement slurry is mixed or not based on a clear standard by comparing the luminescence rate calculated based on the data output by the measuring device with a predetermined threshold value. Therefore, it is possible to make a determination that is not adversely affected by factors such as the shooting conditions, the color of the soil, the degree of lighting, etc.

[0022] (First embodiment) An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a side view of a ground improvement device according to the first embodiment of the present invention.

[0023] The first embodiment relates to the case where a cylindrical ground improvement body is constructed from soil S at a relatively deep location using the ground improvement device (column construction machine) shown in FIG.

[0024] As shown in Figure 1, this ground improvement device comprises a base machine 1 that runs on the ground G, a leader 2 that is positioned in front of the base machine 1 and stands up vertically when in operation, a drive unit 10 that is supported on the leader 2 so that it can be raised and lowered freely and is equipped with 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 underground, and a mixing head 4 that is attached to the lower end of the rotating shaft 3.

[0025] 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 provided a digging blade 5 having claws for digging into the ground and for digging up soil and sand, and this digging blade 5 is axially attached to the rotating shaft 3.

[0026] The type of cement can be selected as usual. Next, a water-soluble fluorescent dye is added to the cement slurry. Suitable water-soluble fluorescent dyes include strontium fluoroborate with a trace amount of europium added (SrB4O7F:Eu2+, peak wavelength 368-371 nm), barium silicide with a trace amount of lead added (BaSiO5:Pb+, peak wavelength 350-353 nm), fluorescein, and quinine sulfate.

[0027] More specifically, it is sufficient to use a commercially available fluorescent leak detection agent (for example, Superglow Fluorescent Leak Detection 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.

[0028] Next, as shown in Figure 1, the mixing head 4 of the excavating and mixing device is set to an initial position close to the ground G, and the drive unit 10 is started to operate, rotating the rotary shaft 3. In this way, the excavating blade 5 is brought to the initial depth H1.

[0029] Next, below the initial depth H1, the slurry is discharged from the base of the excavation blade 5, and excavation and mixing are performed using the mixing head 4. As described above, unlike normal, the slurry contains 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.

[0030] Thereafter, the mixing head 4 is rotated and raised (pulled up) until it reaches the ground, thereby constructing a cylindrical ground improvement body underground using the soil S at the site.

[0031] (Embodiment 2) Fig. 2 is a side view of a soil improvement device according to embodiment 2 of the present invention.

[0032] The second embodiment relates to the case where a flat ground improvement body is constructed at a relatively shallow location using on-site soil S by using the ground improvement device (vertical construction machine) shown in FIG.

[0033] As shown in FIG. 2, this ground improvement device comprises a main body 21 that travels on the ground G, and an operating unit 20 that rotates vertically in a vertical plane to discharge cement slurry and mix it with the soil S.

[0034] The preparation of the cement and the water-soluble fluorescent dye to be added thereto are the same as those in the first embodiment.

[0035] In both embodiments 1 and 2, once the ground improvement body is constructed and solidified, boring cores are collected by boring.

[0036] Fig. 3 is a side view of a boring core collection device. Boring is carried out after the soil improvement body has solidified, and boring cores are collected.

[0037] Next, as shown in Fig. 4, the prepared boring core 35 is placed in a darkroom 31. A light source 6 that irradiates black light and a camera 7 that serves as a measuring device for photographing the boring core 35 irradiated with black light from the light source 6 are placed in the darkroom 31. Here, instead of the camera 7, the measuring device may be a sensor that captures reflected light from the ground improvement body.

[0038] Next, actual photographic examples will be explained with reference to Figures 5 to 8. Figure 5 is an example of a photograph taken in the state of Figure 4 using visible light (fluorescent lamps or sunlight may be used) without using the light source 6 that irradiates black light. Figure 6 is an example of a partially enlarged photograph of Figure 5. These photographs may be in full color or grayscale. A notable feature is that there is almost no difference in shade throughout the drilling core, making it difficult to distinguish between light and dark.

[0039] On the other hand, Figure 7 is a photograph of the exact same object as Figure 6, taken in the same way using black light (wavelength: 365 to 405 nanometers) emitted from 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 6, making it easier to distinguish between light and dark.

[0040] 7 is binarized to black and white, resulting in the image shown in Figure 8. To reduce the number of colors, known methods such as approximate colors, patterns, error diffusion, etc. may be used.

[0041] 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 8, the total number of pixels A is 184,886 pixels, and the number of pixels B in the white part is 166,460 pixels, so the light emission rate (%) = (A / B) * 100 = (166,460 / 184,886) * 100 = 90 (%).

[0042] TH = 80 (%) is used as the threshold value for determining whether the light emission rate (%) is acceptable or not. Needless to say, this value is merely an example, and it should be understood that even if a higher or lower threshold value is used, it still falls within the scope of protection of the present invention. Therefore, in the above numerical example, the light emission rate is satisfactory and the mixed state is confirmed. In other words, the result is that the mixture is sufficiently mixed. On the other hand, if the light emission rate is 80 (%) or less, the mixed state is confirmed.

[0043] That is, as explained with reference to FIG. 8, when the total number of pixels is A and the number of pixels in the white portion is B, the light emission rate (%)=(A / B)*100 (1) can be set.

[0044] 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.

[0045] (Embodiment 3) In this embodiment, after boring as shown in Figure 3, an inspection head 14 is inserted into the vertical hole formed by boring to perform an inspection. Figure 9(a) is a cross-sectional view of the inspection head in embodiment 3 of the present invention, and Figure 9(b) is a cross-sectional view showing the inspection process using the same inspection head. The lower and lateral portions 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 laterally. Note that the storage chamber 14a may also be configured with an opening facing downward. The light source 6 may be a fluorescent lamp, incandescent lamp, mercury lamp, or LED that irradiates the soil improvement body underground with black light (wavelength: 365 to 405 nanometers). However, LEDs are small and easy to use. The measuring instrument 7 may be a sensor such as a fluorometer or a camera equipped with an image sensor that measures the soil improvement body irradiated with black light by the light source 6. However, here, a sensor is used.

[0046] A transparent or translucent protective cover 14b is attached to the opening of the storage chamber 14a, sealing the storage chamber 14a. This protects the light source 6 and the measuring instrument 7 from surrounding soil, sand, slurry, etc. The protective cover 14b can be suitably made of a resin plate such as acrylic, a tempered glass plate, or the like.

[0047] Now, once boring is complete, a vertical hole will be formed in the soil improvement body as described above. As shown in Figure 9(b), the inspection head 14 is connected to the control computer 16 using the connection cable 15, and the inspection head 14 is inserted into the vertical hole to a predetermined depth. In this state, the light source 6 is turned on and measurements are taken using the measuring instrument 7. The processing itself, including the light emission rate, can be carried out in the same manner as described above, so further explanation will be omitted.

[0048] 1. A side view of a ground improvement device in embodiment 1 of the present invention. 2. A side view of a ground improvement device in embodiment 2 of the present invention. 3. A side view of a boring facility. 4. An explanatory diagram of each process in the present invention. 5. A photograph of a boring core taken under natural light in the present invention. 6. A diagram showing a grayscale image of a part of FIG. 5. 7. A photograph of a boring core taken under black light in an implementation of the present invention. 8. A diagram showing a black and white binarized image of FIG. 7. (a) A cross-sectional view of an inspection head in embodiment 3 of the present invention. (b) A cross-sectional view showing an inspection process using an inspection head in embodiment 3 of the present invention.

[0049] REFERENCE SIGNS LIST 1 Base machine 2 Reader 3 Rotating shaft 4 Mixing head 5 Excavation blade 6 Light source 7 Camera 10 Drive unit 14 Inspection head 14a Storage room 14b Protective cover 15 Connection cable 16 Control computer 20 Operating unit 21 Main body 31 Darkroom 35 Boring core G Ground S Soil H1 Initial depth H2 Target depth

Claims

1. A ground improvement method for constructing a ground improvement body by mixing soil with a cement slurry to which a predetermined concentration of water-soluble fluorescent dye has been added, the method comprising: 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 instrument; and a third step of comparing the luminescence rate calculated 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.

2. A ground improvement method as described in claim 1, wherein the measuring instrument is a sensor that captures reflected light from the ground improvement body.

3. A ground improvement method as described in claim 1, wherein the measuring instrument is a camera that takes images of the ground improvement body.

4. The ground improvement method according to claim 1, wherein the wavelength of the black light is 365 to 405 nanometers.

5. A ground improvement method as described in claim 1, wherein the soil is soil at a construction site, and the first, second and third steps are carried out using a boring core collected by boring while the ground improvement body is in a solidified state.

6. A ground improvement method as described in claim 1, wherein the soil is soil at a construction site, and the first, second and third steps are carried out in a vertical hole formed by boring while the ground improvement body is in a solidified state.

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