JP7474522B2 - How to check the mixed condition of ground improvement material - Google Patents

Description

The present invention relates to a method for checking the mixing state of a ground improvement body, which allows accurate checking of the mixing status of the ground improvement body in real time in parallel with the mixing and construction of the ground improvement body in the ground.

One known ground improvement method is the deep mixing method, in which cement slurry is pumped into the ground and mixed mechanically to create a ground improvement body in the ground. This method creates a vertical cylindrical ground improvement body in the ground by mixing and stirring the soil and cement slurry that make up the ground.

In ground improvement methods, after the construction of the ground improvement body, issues include whether the improvement material is mixed correctly (particularly the radial distribution of the cement slurry) and whether the constructed ground improvement body has the designed diameter. Because the ground improvement body exists underground, it is not easy to check its condition from above ground.

Normally, after the cement slurry has hardened in the created ground improvement body, a boring machine is used to take samples of the ground improvement body from above ground, and check boring is performed to check the condition of the ground improvement body.

However, this method requires a large number of other devices in addition to the boring machine, making the equipment large and complex. This increases the cost of the work, and it is very time-consuming and labor-intensive.

In light of this situation, Patent Document 1 (JP Patent Publication 2009-102892 A) proposes a method of checking the ground improvement body by inserting a camera-equipped rod, which is a pipe rod equipped with a camera that takes pictures of the ground, after constructing a ground improvement body in the ground and before the improvement material hardens, and displaying the image of the ground taken by the camera on a monitor on the ground, so that a worker can visually check the monitor to see whether or not the improvement material is present.

It is dark underground, and images displayed on monitors tend to be unclear, making it difficult for workers to make correct judgments.

On the other hand, Patent Document 2 (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.

This method requires comparing two or more groups of images, and the condition of the ground improvement body cannot be confirmed immediately after the images are taken. Accurate judgment can be difficult depending on the color of the soil (dark colors) and the degree of lighting. In particular, in (2), the brightness and color are likely to change depending on the comparison position, making the accuracy of the comparison an issue.

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.

However, it is difficult to spray phenolphthalein and observe the process of constructing ground improvement bodies inside the ground.

Regardless of which of the above methods is used, it is difficult to accurately check the mixing status of the ground improvement body in real time in parallel with the mixing and construction of the ground improvement body in the ground.
JP 2009-102892 A Patent No. 6944605 The Building Center of Japan "2018 Edition: Design and Quality Control Guidelines for Improved Ground for Buildings"

The present invention aims to provide a method for checking the mixing state of a ground improvement body, which allows the mixing status of the ground improvement body to be checked accurately in real time in parallel with the mixing.

The method for checking the mixed state of a ground improvement body according to the first invention comprises the steps of:
A first step of preparing a cement slurry having a water-soluble fluorescent dye added thereto;
A second step of discharging the cement slurry from the base of the excavation blade, excavating and mixing the discharged cement slurry with the surrounding soil and sand, and constructing an unhardened ground improvement body;
A third step of irradiating the unhardened ground improvement body with black light from a light source provided on the excavation wing at a depth within the unhardened ground improvement body where the excavation wing is located;
The method includes a fourth step of measuring the reflected light of the black light with a measuring device attached to the excavation wing at the depth where the excavation wing is located within the unhardened ground improvement body.

Here, with the above configuration, while the ground improvement body is still in an unhardened state, the quality of the mixed state can be determined based on the reflected light of the black light measured by the measuring device. In this case, there is no need to add large-scale equipment such as a boring machine. Furthermore, even underground, the water-soluble fluorescent dye illuminated by the black light emits light smoothly, allowing the state to be correctly recognized. Furthermore, the results do not become 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.

Furthermore, it is preferable to determine the light emission rate based on the output of the measuring instrument.

It is even more preferable to compare the light emission rate with a predetermined threshold value to determine whether the mixed state is good or bad.

The light source and the measuring instrument preferably rotate along a circular orbit about an axis of rotation that rotates the drilling blade.

In this way, the positions of the light source and measuring instrument within the rotational plane of the drilling blade are determined solely by the rotation angle of the rotating shaft, allowing for stable measurements.

According to the present invention, the ground improvement body can be constructed while accurately checking the mixing status of the unhardened ground improvement body in real time in parallel with the excavation and mixing in the ground where excavation and mixing are being performed. Therefore, the condition of the ground improvement body can be confirmed at the actual excavation position without being adversely affected by the shooting conditions, the color of the soil, the degree of lighting, etc., and this has a high practical effect.

The following describes an embodiment of the present invention with reference to the drawings. Figure 1 is a side view of a ground improvement device in one embodiment of the present invention, Figure 2(a) is a schematic block diagram of the excavation and mixing device, Figure 2(b) is a partially enlarged cross-sectional view of the excavation and mixing device, and Figure 3 is a plan view of the excavation and mixing device.

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 vertically when in operation, a drive unit 10 that is equipped with an actuator such as a motor and is instructed to move freely up and down by the leader 2, 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 attached to the lower end of the rotating shaft 3.

The control unit 20 that controls the drive unit 10 is housed within the base machine 1.

Figure 2(a) shows the portion of the ground improvement device shown in Figure 1 that corresponds to the excavation and mixing device. The control unit 20 outputs a control signal S1 to the drive unit 10 to control the operating state of the drive unit 10. The control unit 20 also inputs a measurement signal S2 that includes state quantities (e.g., rotation speed, drive current, resistance to rotation, etc.) that indicate the operation of the drive unit 10 to grasp the operating state.

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, an excavation blade 5 having a claw 5a for excavating the ground and for excavating soil and sand is provided , and this excavation blade 5 is axially attached to the rotating shaft 3. As shown in an enlarged view in Fig. 2(b), on the upper surface 5b of the excavation blade 5, at a position away from the center of the rotating shaft 3 by a radius r (see also Fig. 3), a storage chamber 5c that opens upward is opened by drilling a part of the excavation blade 5.

A pair of a light source 6 and a measuring instrument 7 is stored inside the storage chamber 5c, each facing upward. The storage chamber 5c 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 fluorophotometer or a camera equipped with an image sensor that measures the ground improvement body irradiated with black light by the light source 6. The light emission rate will be described later using Figures 5 and 6.

Furthermore, a transparent or semi-transparent protective cover 8 is attached to the opening of the storage chamber 5c, thereby sealing the storage chamber 5c and protecting the light source 6 and the measuring instrument 7 from the surrounding soil and slurry. The protective cover 8 can be suitably made of a resin plate such as acrylic or a plate of reinforced glass. Therefore, the light source 6 and the measuring instrument 7 rise and fall together with the excavation wing 5.

As shown in FIG. 2(a), it is desirable to provide the mixing blade 12 and the anti-rotation blade 11 above the drilling blade 5 on the mixing head 4, but these are not essential and may be omitted. Here, when the mixing head 4 descends (when pulled down), the drilling blade 5 precedes, followed by the mixing blade 12 and the anti-rotation blade 11. Conversely, when the mixing head 4 rises (when pulled up), the mixing blade 12 and the anti-rotation blade 11 precede, followed by the drilling blade 5.

Next, the control unit 20 will be described in detail with reference to FIG. 4. FIG. 4 is a block diagram of the control unit in one embodiment of the present invention. First, the light source 6, measuring device 7, drive unit 10, etc. have already been described.

Of the control unit 20, the memory unit 24 is made up of a control program for implementing operations in accordance with the flowchart in FIG. 7, and storage such as a memory or hard disk for saving each piece of data to be temporarily stored.

The control unit main body 21 is composed of a processor, etc., and executes the control program stored in the memory unit 24 and controls the peripheral elements.

The monitor 23 is a display that shows the operating status to the user.

The state quantity measuring unit 25 measures predetermined state quantities (depth, rotation speed, rotation angle, drive current, resistance to rotation, etc.) based on the measurement signal S2 received from the drive unit 10, and stores them in the memory unit 24.

The control signal generating unit 27 generates a control signal S1 to be output to the driving unit 10 and stores it in the memory unit 24.

The interface 22 is controlled by the control unit main body 21 to input and output the control signal S1 and the measurement signal S2 to the drive unit 10, and also turns the light source 6 on and off and inputs the measurement value (measurement signal) from the measuring instrument 7.

Next, the light emission rate calculated by the light emission rate calculation unit 26 will be explained with reference to Figures 5 and 6.

As already explained with reference to FIG. 3, the storage chamber 5c that houses the light source 6 and the measuring device 7 is located at a position away from the center of the rotation shaft 3 by a radius r, and if its width is t, the trajectory 15 of the storage chamber 5c is as shown in FIG. 6(a). In FIG. 6(a), the center O coincides with the center of the rotation shaft 3.

The light emission rate is the percentage of the area that reflects light, with the area hit by the black light irradiated by the light source 6 being 100%, and is determined based on the measurement value of the measuring device 7. In this embodiment, the light emission rate is an index that expresses the degree of mixing of the slurry and the soil. Of course, the closer the light emission rate is to 100%, the better the degree of mixing.

If the distance L (=2πr) that the container chamber 5c travels around once is taken as 1, then
Luminescence rate = (l / L) * 100 (%) (1)

If the angle at which the measuring device 7 captures the reflected light is θ (radian) relative to the angle (2π radian) of the rotation of the accommodation chamber 5c, then
Emission rate = (θ / 2π) * 100 (%) (2)

Either of the above formulas (1) and (2) may be used, or other formulas equivalent to these may also be used.

Regardless of which formula is used, if the state in Figure 6 (a) is expanded into a straight line, and the state where the measuring device 7 captures reflected light is hatched, and the state where the measuring device 7 does not capture reflected light is not hatched, then if the light emission rate is 100 (%), the entire length will be hatched, as shown in Figure 6 (b).

On the other hand, if the light emission rate is 50%, the state will be as shown in FIG. 6(c). Here, for ease of understanding, the hatched and non-hatched states are shown consecutively. However, it is generally believed that the state in which the measuring device 7 captures reflected light and the state in which the measuring device 7 does not capture reflected light alternate randomly. Therefore, it must be understood that even if the hatched and non-hatched states occur randomly in this way, this still falls within the scope of protection of the present invention.

As shown in Figure 5, if the coefficient of variation (= standard deviation/average value) of needle penetration intensity is plotted on the vertical axis and the emission rate (%) is plotted on the horizontal axis, there is a relationship in which the coefficient of variation decreases as the emission rate (%) approaches the maximum value (100 (%)).

In this 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 should be understood that even if a higher threshold value is used, it still falls within the scope of protection of the present invention.

Incidentally, if the case where the light emission rate coincides with this threshold value TH = 80 (%) is illustrated in the same manner as in Figure 6 (c), it will be as shown in Figure 6 (d). Here too, as in the above, it must be understood that even if the hatched state and the non-hatched state occur randomly, this falls within the scope of protection of the present invention.

Next, with reference to Figures 7 and 8, we will explain the operation of the excavation and mixing device in this embodiment and the method of operating and managing the device.

First, as shown in step 1 of Figure 7, prepare the cement slurry as usual. The type of cement can be selected as usual, and there are no particular restrictions here.

Next, as shown in step 2 of Figure 7, a water-soluble fluorescent dye is added to the slurry. This is different from the usual method. Suitable water-soluble fluorescent dyes include strontium fluoroborate 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, quinine sulfate, etc.

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 (%). It is usually not necessary to change the water-soluble fluorescent dye depending on the type of cement.

Next, as shown in step 3 of FIG. 7 and FIG. 8(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 operation of the drive unit 10 is started to rotate the rotating shaft 3. In this way, the excavation blade 5 is brought to the initial depth H1.

Next, as shown in step 4 of FIG. 7 and FIG. 8(b), 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 usual, 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, as shown in step 5 of Figure 7 and Figure 8 (c).

When the drilling blade 5 reaches the target depth H2, the lifting operation of the rotating shaft 3 is switched from "pulling down" to "pulling up" as shown in step 6 of FIG. 7 and FIG. 8(d).

Then, at the current position, the light source 6 is turned on and a measurement is performed by the measuring device 7. When the rotating shaft 3 has completed one revolution, the control unit 21 compares the light emission rate R (%) calculated by the light emission rate calculation unit 26 with the threshold value TH (80 (%) in this example) stored in the memory unit 24. At this time, either of the above-mentioned formulas (1) and (2) may be used, or an equivalent formula may be used.

In step 8 of FIG. 7, if the light emission rate R falls below the threshold value TH, the control unit main body 21 determines that the advancement condition is not met and maintains the current position without raising the drilling head 4. In conventional technology, such a check is not performed, and the drilling head 4 is advanced indiscriminately even when the mixing is essentially insufficient. According to the present invention, if the mixing is insufficient, the advancement is stopped and mixing is continued (this operation is rational), which contributes to improving the quality of the ground improvement body to be constructed.

In step 8 of FIG. 7, if the light emission rate R is equal to or greater than the threshold value TH, the control unit body 21 determines that the advancement condition is met and raises the drilling head 4 to advance the current position.

Of course, it should be understood that even if a comparison substitution known to those skilled in the art is made, such as when the light emission rate R is equal to or less than the threshold value TH, the control unit body 21 determines that the advancement condition is not satisfied, or when the light emission rate R exceeds the threshold value TH, the control unit body 21 determines that the advancement condition is satisfied, this still falls within the scope of protection of the present invention.

In this way, when pulling up, the fact that mixing is being performed well at the current position of the drilling head 4 can be accurately confirmed at the site itself using the luminescence rate, while constructing a ground improvement body, and it can be said that the practical effect of the present invention is great. In addition, there is no unnecessary delay in the pulling up work due to the measurement and comparison of the luminescence rate. On the other hand, with conventional technology, it must be said that it is virtually impossible to perform quality assurance of the degree of mixing in parallel with the ground improvement work.

This state continues up to the initial depth H1 (steps 9 and 10 in FIG. 7), as shown in FIG. 8(e) to FIG. 8(g), and finally, as shown in FIG. 7(step 11) and FIG. 8(h), a return to ground operation is performed.

FIG. 1 is a side view of a ground improvement device according to an embodiment of the present invention. (a) A schematic block diagram of an excavation and stirring device in one embodiment of the present invention. (b) A partially enlarged cross-sectional view of the excavation and stirring device in one embodiment of the present invention. FIG. 1 is a plan view of an excavation and stirring device according to an embodiment of the present invention; Block diagram of a control unit according to an embodiment of the present invention. Graph showing the relationship between light emission rate and coefficient of variation in one embodiment of the present invention. (a) A graph showing the trajectories of a light source and a measuring instrument in one embodiment of the present invention. (b) A development showing a light emission rate of 100% in one embodiment of the present invention. (c) A development showing a light emission rate of 50% in one embodiment of the present invention. (d) A development showing a light emission rate of 80% in one embodiment of the present invention. A flowchart showing the operation and management of the soil improvement device according to one embodiment of the present invention. (a) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention. (b) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention. (c) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention. (d) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention. (e) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention. (f) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention. (g) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention. (h) An explanatory diagram of a process using an excavation and stirring apparatus in one embodiment of the present invention.

REFERENCE SIGNS LIST 1 Base machine 2 Reader 3 Rotating shaft 4 Mixing head 5 Excavation blade 5a Claw 5b Top surface 5c Storage chamber 6 Light source 7 Measuring instrument 8 Protective cover 10 Driving unit 11 Co-rotation prevention blade 12 Mixing blade 15 Track 20 Control unit 21 Control unit main body 22 Interface 23 Monitor 24 Memory unit 25 State quantity measuring unit 26 Light emission rate calculation unit 27 Control signal generating unit G Ground surface S1 Control signal S2 Measurement signal t Width r Radius θ Angle H1 Initial depth H2 Target depth

Claims (5)

A first step of preparing a cement slurry having a water-soluble fluorescent dye added thereto;
A second step of discharging the cement slurry from the base of the excavation wing, excavating and mixing the discharged cement slurry with the surrounding soil and sand, and constructing an unhardened ground improvement body;
A third step of irradiating the ground improvement body with black light from a light source provided on the excavation wing at a depth within the unhardened ground improvement body where the excavation wing is located;
A fourth step of measuring the reflected light of the black light at a depth where the excavation wing is located within the unhardened ground improvement body using a measuring device provided on the excavation wing;
A fifth step of determining a light emission rate based on the output of the measuring device ;
A method for checking the mixed state of a ground improvement body , comprising a sixth step of comparing the light emission rate with a predetermined threshold value to determine whether the mixed state is good or bad . The method for checking the mixed state of a ground improvement body according to claim 1, wherein the measuring instrument is a sensor that captures reflected light from the ground improvement body. The method for checking the mixed state of a ground improvement body according to claim 1, wherein the measuring instrument is a camera that takes an image of the ground improvement body. A method for checking the mixed state of a ground improvement body as described in claim 1, wherein the wavelength of the black light is 365 to 405 nanometers. The method for checking the mixed state of a ground improvement body according to claim 4 , wherein the light source and the measuring instrument rotate along a circular orbit centered on a rotation axis that rotates the drilling blade.

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