Ground improvement device and ground improvement method

Abstract

To provide an improved ground improvement device and method. [Solution] A ground improvement device according to one embodiment includes a rod inserted into the ground, a monitor attached to the rod, a first supply path passing through the inside of the rod to send liquid to the monitor, and a second supply path passing through the inside of the rod to send powder to the monitor. The monitor further includes a mixing section that generates a hardening material by mixing the liquid sent by the first supply path and the powder sent by the second supply path, and a hardening material nozzle that injects the hardening material generated by the mixing section into the ground.

Description

[Technical field]

[0001] The present invention relates to a ground improvement device and a ground improvement method for improving the ground by constructing a ground improvement body underground. [Background technology]

[0002] There are various conventional ground improvement methods, one of which is the high-pressure jet mixing method. In the high-pressure jet mixing method, the ground is cut using a high-pressure jet, and a ground improvement body is created in the resulting space. The high-pressure jet for cutting may be the hardening material itself used to create the ground improvement body, or a liquid such as water that is separate from the hardening material may be used.

[0003] The hardening material is injected from a monitor at the tip of a rod inserted into the ground. The hardening material is generally cement milk, a mixture of cement and water, and is sent to the monitor through a channel in the rod. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-125397 A Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, in conventional ground improvement methods such as the high-pressure jet mixing method, a hardening agent such as cement milk is sent to the monitor. Therefore, it is necessary to place a plant (mixer) on the ground to generate the hardening agent.

[0006] The hardening material is highly viscous because it contains a large amount of cement particles, and this causes a large friction loss when pumped to the monitor. This reduces the injection speed of the hardening material from the nozzle on the monitor, which can lead to a decrease in cutting performance when the hardening material is used as a high-pressure jet for cutting the ground. On the other hand, in order to ensure sufficient cutting performance, the hardening material must be pumped in large quantities at high pressure, which requires a high-output pump.

[0007] In addition, when a hardening material containing many particles is sprayed at high speed, the nozzle wears out, and it becomes necessary to replace the nozzle frequently. Nozzles are generally made of expensive special alloys, and replacement is very costly. Moreover, frequent replacement significantly reduces work efficiency.

[0008] In addition to the above, conventional ground improvement methods have various problems. Therefore, one of the objects of the present invention is to provide an improved ground improvement device and ground improvement method that can improve the work efficiency and reduce the cost related to ground improvement. [Means for solving the problem]

[0009] A ground improvement device according to one embodiment includes a rod inserted into the ground, a monitor attached to the rod, a first supply path passing through the inside of the rod to send liquid to the monitor, and a second supply path passing through the inside of the rod to send powder to the monitor. The monitor further includes a mixing section that generates a hardening material by mixing the liquid sent by the first supply path and the powder sent by the second supply path, and a hardening material nozzle that injects the hardening material generated by the mixing section into the ground.

[0010] For example, the mixing section includes a mixing chamber connected to the hardener nozzle and the second supply passage, and a mixing nozzle connected to the first supply passage and spraying the liquid into the mixing chamber, and as the mixing chamber is depressurized in conjunction with the spraying of the liquid by the mixing nozzle, the powder in the second supply passage is drawn into the mixing chamber and mixed with the liquid.

[0011] The mixing section may further include a decompression chamber provided between the second supply path and the mixing chamber, and the powder in the second supply path may be drawn into the mixing chamber through the decompression chamber.

[0012] The ground improvement device may further include a third supply passage that passes through the inside of the rod and sends gas to the monitor. In this case, the hardening material nozzle may inject the gas sent by the third supply passage together with the hardening material.

[0013] The ground improvement device may further include a fourth supply passage that passes through the inside of the rod and supplies liquid to the monitor. In this case, the monitor may further include a cutting nozzle that cuts the ground by spraying the liquid supplied by the fourth supply passage.

[0014] The ground improvement device may further include a fifth supply passage that passes through the inside of the rod and supplies gas to the monitor. In this case, the cutting nozzle may inject the gas supplied by the fifth supply passage together with the liquid supplied by the fourth supply passage.

[0015] The monitor may further include an outlet located at the lower end of the rod in the extension direction, through which the liquid of the first supply path is discharged, a drilling tool provided around the outlet, and a valve portion for opening and closing a flow path from the first supply path to the outlet.

[0016] One embodiment of the ground improvement method includes inserting the rod into the ground, rotating the rod while spraying the hardening material from the hardening material nozzle, and pulling up the rod to create a ground improvement body in the ground in which the hardening material has hardened. Effect of the Invention

[0017] According to the present invention, it is possible to provide an improved ground improvement device and a ground improvement method that can improve the efficiency of ground improvement work and reduce costs. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a construction system for carrying out the ground improvement method according to the first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing the configuration of the monitor according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of a ground improvement method using the ground improvement device or construction system according to the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing the configuration of a monitor according to the second embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing the configuration of a monitor according to the third embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing the configuration of a monitor according to the fourth embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing the configuration of a monitor according to the fifth embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view showing the configuration of a monitor according to the sixth embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view showing the configuration of a monitor according to the seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Several embodiments will be described with reference to the drawings. In each embodiment, an example is disclosed in which the ground improvement method and the ground improvement device according to the present invention are applied to a high-pressure jet mixing method and a device for carrying out the method. However, the configurations disclosed in each embodiment can be modified appropriately and applied to other types of methods related to ground improvement, etc.

[0020] [First embodiment] 1 is a diagram showing an example of the configuration of a construction system for carrying out a ground improvement method according to the first embodiment. This construction system includes a ground improvement device 1, a pump 2, and a silo 3.

[0021] The ground improvement device 1 includes a rod 4 to be inserted into a hole H provided in the ground, a monitor 5 provided at the tip of the rod 4 (the lower end in the figure), and a work machine 6 that holds the rod 4. The work machine 6 includes a linear motion mechanism for moving the rod 4 up and down, and a rotation mechanism for rotating the rod 4. The work machine 6 may further include a swinging mechanism for swinging the rod 4.

[0022] A pump 2 supplies water supplied from a water supply source S, such as a water tank, to a rear end 7 of the rod 4. A silo 3 contains cement powder. This powder is supplied to the rear end 7 of the rod 4. In the example of FIG. 1, a storage section 8 for temporarily storing the powder supplied from the silo 3 is provided at the rear end 7. As another example, the powder may be supplied directly to the rear end 7 without passing through the storage section 8.

[0023] The construction system may further include a powder supplying device 9 for sending the powder in the silo 3 to the storage section 8. As the powder supplying device 9, for example, a belt conveyor can be used, but is not limited to this example.

[0024] As will be described in detail later, the water and powder supplied to the rod 4 are sent to the monitor 5 through the inside of the rod 4 and mixed inside the monitor 5. The hardening material produced by this mixing is injected at high pressure laterally from the monitor 5 underground. The hardening material injected into the ground hardens to produce a ground improvement body G.

[0025] 2 is a schematic cross-sectional view showing the configuration of the monitor 5 according to this embodiment. The monitor 5 includes a first supply path P1, a second supply path P2, a mixer 10, and a hardener nozzle 20.

[0026] The first supply path P1 and the second supply path P2 extend through the inside of the rod 4 to the rear end 7. The first supply path P1 is supplied with high-pressure water sent from the pump 2 to the rear end 7. The second supply path P2 is supplied with powder sent from the silo 3 to the storage section 8.

[0027] The mixing section 10 generates a hardening material by mixing the water sent through the first supply path P1 and the powder sent through the second supply path P2. The hardening material nozzle 20 sprays the hardening material generated by the mixing section 10.

[0028] In this embodiment, the mixing section 10 includes a mixing chamber 11 and a mixing nozzle 12. The mixing chamber 11 is connected to the hardener nozzle 20 and the second supply passage P2. The mixing nozzle 12 is connected to the first supply passage P1 and sprays the water sent through the first supply passage P1. As a result, a jet of water W is formed in the mixing chamber 11.

[0029] The jet W is mixed with the powder C supplied from the second supply passage P2 to the mixing chamber 11. Thus, the mixture of water and powder C generated in the mixing chamber 11 corresponds to the hardening material in this embodiment. Note that, in this embodiment, the mixing in the mixing section 10 does not necessarily mean that the water of the jet W and the powder C are uniformly mixed like cement milk. In other words, in the mixing section 10, it is sufficient that the powder C is added to the jet W.

[0030] The hardener nozzle 20 is provided at a position facing the mixing nozzle 12 across the mixing chamber 11. Therefore, a jet W mixed with the powder C, i.e., a jet M of the hardener, is sprayed from the hardener nozzle 20 to the side of the monitor 5. The spray direction of the jet M may be a horizontal direction perpendicular to the extension direction of the rod 4, or may be a direction inclined relative to the horizontal direction.

[0031] The jet W can be used as the power for drawing the powder C into the mixing chamber 11. That is, the jet W passes through the mixing chamber 11, and the mixing chamber 11 is put into a vacuum state. As a result, the powder C is drawn into the mixing chamber 11 from the second supply path P2. Here, the "vacuum state" means a state in which the pressure is reduced to such an extent that the powder C in the second supply path P2 is drawn into the mixing chamber 11. Note that the method of sending the powder C to the mixing chamber 11 is not limited to drawing by the jet W described here. As another example, the powder C may be sent into the mixing chamber 11 by pressure-feeding using a gas such as air.

[0032] If the water of the jet W accumulates in the mixing chamber 11, a vacuum state cannot be formed, and the powder C is not drawn into the mixing chamber 11. Therefore, it is preferable that the hardener nozzle 20 has a larger diameter than the mixing nozzle 12 so that all of the hardener, which is a mixture of the water of the jet W and the powder C, is discharged from the mixing chamber 11.

[0033] In this embodiment, the "mixing chamber" refers to a place where the water of the jet W and the powder C of the second supply path P2 are mixed, and does not necessarily have to be a space whose width in the extension direction (vertical direction in the figure) of the rod 4 or in the horizontal direction (horizontal direction in the figure) is larger than the diameter of the first supply path P1 or the second supply path P2 as shown in Fig. 2. As an example, the mixing chamber 11 may be a truncated cone-shaped space that spreads from the tip of the mixing nozzle 12 to the hardener nozzle 20.

[0034] Fig. 3 is a diagram showing an example of a ground improvement method using the ground improvement device 1 or construction system according to this embodiment. In ground improvement, a small-diameter hole H is first formed in the ground as shown in Fig. 3(a). Then, a rod 4 is inserted into the hole H. Note that, as in a seventh embodiment described later, when a cutting tool is provided at the lower end of the monitor 5, the hole H may be formed by boring using the rod 4 and the monitor 5.

[0035] Next, high-pressure water is supplied to the monitor 5 by driving the pump 2. Furthermore, the work machine 6 moves the rod 4 upward while rotating it. At this time, a jet M of hardening material is sprayed from the monitor 5, as shown in FIG. 3(b). The ground forming the wall surface of the hole H is cut by this jet M, and the hardening material is filled into the resulting space. The mud (a mixture of soil and hardening material) generated by the cutting is discharged to the ground through the gap between the rod 4 and the hole H.

[0036] After that, when the rod 4 is further pulled up, the space filled with the hardening material grows vertically as shown in Figure 3(c). As the hardening material in this space hardens, a cylindrical ground improvement body G is created.

[0037] According to the present embodiment described above, it is possible to provide an improved ground improvement device and a ground improvement method that can improve the efficiency of work related to ground improvement and reduce costs.

[0038] That is, in a conventional general construction method, a hardening agent (cement milk) is produced by mixing cement powder and water on the ground, and this hardening agent is pumped through a rod to the monitor 5. In this case, it is necessary to place a mixer and a measuring device on the ground to mix the cement powder and water.

[0039] In contrast, in this embodiment, cement powder and water are sent separately to the monitor 5 and mixed in the mixing section 10 of the monitor 5. With this configuration, there is no need to install mixers or measuring instruments on the ground, and the work efficiency and cost of ground improvement work can be significantly improved.

[0040] Moreover, in this embodiment, the powder C is supplied to the mixing chamber 11 by reducing the pressure in the mixing chamber 11 with the jet W of the mixing nozzle 12. With this configuration, a mechanism for sending the powder C to the mixing section 10 is not necessary.

[0041] In addition, it is water that needs to be pumped from the ground to the monitor 5, and the friction loss in the rod 4 is extremely small compared to pumping hardening materials such as cement milk. Therefore, it is possible to use a low-volume pump 2, and further cost reductions can be expected.

[0042] Because the mixing nozzle 12 sprays water, the mixing nozzle 12 is subject to very little wear. Therefore, the mixing nozzle 12 needs to be replaced less frequently than nozzles that spray hardening materials in conventional construction methods. As a result, the work time and cost required to replace the mixing nozzle 12 is very small compared to the overall construction work.

[0043] Furthermore, although the hardener nozzle 20 sprays a mixture of cement powder and water, the flow rate of the hardener is slower than that of the water sprayed from the mixing nozzle 12 because it passes through the mixing chamber 11. This also reduces wear on the hardener nozzle 20. As a result, the labor time and cost required to replace the hardener nozzle 20 are also reduced. In addition to those described above, various other advantageous effects can be obtained from this embodiment.

[0044] Below, second to seventh embodiments will be disclosed that are applicable to the monitor 5. Configurations and effects not specifically mentioned in each embodiment are similar to those of the first embodiment.

[0045] [Second embodiment] 4 is a schematic cross-sectional view showing the configuration of a monitor 5 according to a second embodiment. The monitor 5 according to this embodiment further includes a third supply path P3 in addition to the elements shown in FIG.

[0046] The third supply passage P3 passes through the inside of the rod 4 shown in Fig. 1 and extends to the rear end 7. High-pressure air is supplied to the third supply passage P3 from the rear end 7. A pump for generating this high-pressure air is disposed on the ground at the construction site and forms a part of the construction system according to this embodiment.

[0047] Furthermore, the third supply passage P3 is connected to the hardener nozzle 20 inside the monitor 5. In this embodiment, the hardener nozzle 20 is a double nozzle in which an annular injection port for injecting air from the third supply passage P3 is provided around an injection port for injecting the hardener.

[0048] In such a configuration, an air jet Am is formed around the hardening material jet M. This increases the reach of the jet M when excavating the ground as shown in Figs. 3(b) and (c). As a result, a large-diameter ground improvement body G can be formed. Alternatively, the capacity of the pump 2 can be reduced compared to the case where the monitor 5 according to the first embodiment is used.

[0049] [Third embodiment] 5 is a schematic cross-sectional view showing the configuration of a monitor 5 according to a third embodiment. In addition to the elements shown in FIG. 2, the monitor 5 according to this embodiment further includes a fourth supply path P4 and a cutting nozzle 30 connected to the fourth supply path P4.

[0050] The fourth supply passage P4 passes through the inside of the rod 4 shown in FIG. 1 and extends to the rear end 7. High-pressure water is supplied to the fourth supply passage P4 from the rear end 7. This water may be supplied by the pump 2 or may be supplied by a pump separate from the pump 2.

[0051] The cutting nozzle 30 is provided on the side of the monitor 5, above the hardener nozzle 20. The cutting nozzle 30 sprays water fed through the fourth supply path P4. This forms a jet E for cutting the ground. The spray direction of the jet E may be a horizontal direction perpendicular to the extension direction of the rod 4, or may be a direction inclined relative to the horizontal direction.

[0052] When the monitor 5 according to this embodiment is used, the ground is cut by the jet E when forming the ground improvement body G as shown in Figures 3(b) and (c). In other words, the hardener nozzle 20 can be used mainly for discharging the hardener, so that the design freedom of the mixing nozzle 12 and the hardener nozzle 20 is increased.

[0053] Furthermore, in the configurations according to the first and second embodiments, the ground is cut with the jet M of the hardening material, so that sludge mixed with the hardening material and soil is discharged onto the ground. In contrast, when the ground is cut with the jet E of the cutting nozzle 30 as in this embodiment, sludge mixed with mainly water and soil is discharged onto the ground. Therefore, it is possible to suppress the discharge amount of sludge mixed with the hardening material.

[0054] [Fourth embodiment] Fig. 6 is a schematic cross-sectional view showing the configuration of a monitor 5 according to a fourth embodiment. The monitor 5 according to this embodiment further includes a fifth supply path P5 in addition to the elements shown in Fig. 5 in the third embodiment.

[0055] The fifth supply passage P5 passes through the inside of the rod 4 shown in Fig. 1 and extends to the rear end 7. High-pressure air is supplied to the fifth supply passage P5 from the rear end 7. A pump for generating this high-pressure air is disposed on the ground at the construction site and forms a part of the construction system according to this embodiment.

[0056] Furthermore, the fifth supply passage P5 is connected to the cutting nozzle 30 inside the monitor 5. In this embodiment, the cutting nozzle 30 is a double nozzle in which an annular nozzle for spraying air from the fifth supply passage P5 is provided around an nozzle for spraying high-pressure water.

[0057] In such a configuration, an air jet Ae is formed around the cutting jet E. This increases the reach of the jet E when cutting the ground. As a result, a large-diameter ground improvement body G can be formed. Alternatively, compared to the case where the monitor 5 according to the third embodiment is used, the capacity of the pump for supplying high-pressure water to the fourth supply path P4 can be reduced.

[0058] [Fifth embodiment] Fig. 7 is a schematic cross-sectional view showing the configuration of a monitor 5 according to a fifth embodiment. The monitor 5 according to this embodiment further includes the third supply path P3 shown in Fig. 4 in the second embodiment, in addition to the elements shown in Fig. 6 in the fourth embodiment.

[0059] That is, in this embodiment, a jet M of hardener and a jet Am of air are sprayed from the hardener nozzle 20. Furthermore, a jet E for cutting and a jet Ae of air are sprayed from the cutting nozzle 30. With this configuration, it is possible to obtain the effects described above in the second and fourth embodiments.

[0060] [Sixth embodiment] 8 is a schematic cross-sectional view showing the configuration of a monitor 5 according to the sixth embodiment. The monitor 5 according to this embodiment has a different configuration of a mixer 10 from that shown in FIG. 2 in the first embodiment.

[0061] That is, the mixing section 10 further includes a decompression chamber 13 (preliminary decompression chamber). The decompression chamber 13 is connected to the second supply passage P2 and is connected to the mixing chamber 11 through a connection passage 14. In FIG. 8, the diameter of the connection passage 14 is smaller than the diameter of the second supply passage P2, but this is not limited to this example.

[0062] In the monitor 5 according to this embodiment, the pressure in the decompression chamber 13 is also reduced as the mixing chamber 11 is decompressed by the jet W of the mixing nozzle 12. The powder C in the second supply path P2 is first drawn into the decompression chamber 13, and then drawn into the mixing chamber 11 through the connection path 14.

[0063] For example, in a configuration in which the second supply path P2 and the mixing chamber 11 are directly connected as in each of the above-mentioned embodiments, if the fluidity of the powder C is low, the powder C may form clumps and be intermittently drawn into the mixing chamber 11. In contrast, in the configuration of this embodiment, even if the fluidity of the powder C is low, the powder C in the second supply path P2 is first drawn into the decompression chamber 13 and loosened, and then supplied to the mixing chamber 11. Therefore, the powder C can be stably supplied to the mixing chamber 11 at a constant pace.

[0064] In this embodiment, an example is given of a case in which a reduced pressure chamber 13 is provided in the monitor 5 having the configuration shown in the first embodiment, but a similar reduced pressure chamber 13 can also be provided in the monitors 5 shown in the second to fifth embodiments.

[0065] [Seventh embodiment] 9 is a schematic cross-sectional view showing the configuration of a monitor 5 according to a seventh embodiment. The monitor 5 according to this embodiment further includes a drilling fluid outlet 41, a drilling tool 40, and a valve unit 50 in addition to the elements shown in FIG.

[0066] The discharge port 41 is located at the lower end of the monitor 5, and communicates with the first supply path P1. The drilling tool 40 is, for example, a metal blade provided so as to surround the discharge port 41.

[0067] The valve unit 50 opens and closes a flow path from the first supply path P1 to the discharge port 41. In the example of Fig. 9, the valve unit 50 includes a valve seat 51 provided at the lower end of the first supply path P1, and a metal ball 52 that can be inserted into the first supply path P1.

[0068] The monitor 5 according to this embodiment can also be used to form a hole H for inserting a rod 4 into the ground. That is, the rod 4 is rotated and lowered by the work machine 6, and the drilling tool 40 excavates the ground. During this excavation, the metal balls 52 are not inserted. Therefore, water sent from the pump 2 is discharged from the discharge port 41. Using this water as a drilling fluid enables smooth drilling and soil removal.

[0069] After the hole H has been formed, a metal ball 52 is put into the first supply passage P1. When the metal ball 52 is received by the valve seat 51, the flow path from the first supply passage P1 to the discharge port 41 is blocked. In this state, as in the monitor 5 according to the first embodiment, the water in the first supply passage P1 is sprayed into the mixing chamber 11 through the mixing nozzle 12, the powder C is mixed into the jet W, and the jet M of the hardener is sprayed from the hardener nozzle 20. Therefore, by lifting the rod 4 while rotating it as shown in FIG. 3, a ground improvement body G can be formed in the ground.

[0070] In this embodiment, an example is shown in which a monitor 5 having the configuration shown in the first embodiment is provided with an outlet 41, a drilling tool 40, and a valve portion 50, but a similar configuration can be applied to the monitor 5 shown in the second to sixth embodiments.

[0071] The present invention is not limited to the configurations of the above-described first to seventh embodiments, and can be modified in various ways.

[0072] For example, in each embodiment, the powder and liquid for generating the hardening agent are cement and water, respectively. However, the powder for generating the hardening agent is not limited to cement as long as it is a material capable of solidifying or strengthening the ground. In addition, the liquid for generating the hardening agent is not limited to water as long as it does not contain solid particles that cause significant wear of the nozzle and has low viscosity (low friction loss). Furthermore, the gas for forming the jets Am and Ae disclosed in the second embodiment (FIG. 4), the fourth embodiment (FIG. 6), and the fifth embodiment (FIG. 7) is not limited to air, and various gases may be used depending on the situation.

[0073] The first supply path P1 and the fourth supply path P4 of the monitor 5 according to the third to fifth embodiments (FIGS. 5 to 7) may form a common flow path in at least a part of the interior of the rod 4 and the monitor 5. Similarly, the third supply path P3 and the fourth supply path P4 of the monitor 5 according to the fifth embodiment (FIG. 7) may form a common flow path in at least a part of the interior of the rod 4 and the monitor 5.

[0074] The monitor 5 according to each embodiment may include two or more hardener nozzles 20. In this case, the monitor 5 may include a number of mixing units 10 corresponding to each hardener nozzle 20. Similarly, in the third to fifth embodiments (FIGS. 5 to 7), the monitor 5 may include two or more cutting nozzles 30. [Explanation of symbols]

[0075] 1...ground improvement device, 2...pump, 3...silo, 4...rod, 5...monitor, 6...work machine, 10...mixing section, 11...mixing chamber, 12...mixing nozzle, 20...hardening material nozzle, 30...cutting nozzle, 40...drilling tool, 41...discharge outlet, 50...valve section, P1...first supply passage, P2...second supply passage, P3...third supply passage, P4...fourth supply passage, P5...fifth supply passage, C...powder, M...jet of hardening material, G...ground improvement body.

Claims

1. A ground improvement device for constructing a ground improvement body, A rod to be inserted into the ground; A monitor provided on the rod; A first supply passage that passes through the inside of the rod and supplies liquid to the monitor; a second supply passage passing through the inside of the rod and supplying powder to the monitor; Equipped with The monitor includes: a mixing section that generates a hardening material by mixing the liquid sent through the first supply path and the powder sent through the second supply path; A hardener nozzle that injects the hardener generated by the mixing unit into the ground; The ground improvement device is provided with:

2. The mixing section includes: a mixing chamber connected to the hardener nozzle and the second supply passage; a mixing nozzle connected to the first supply passage and configured to inject the liquid into the mixing chamber; Equipped with the mixing chamber is depressurized as the liquid is sprayed by the mixing nozzle, whereby the powder in the second supply passage is drawn into the mixing chamber and mixed with the liquid. The ground improvement device according to claim 1.

3. The mixing section further includes a decompression chamber provided between the second supply path and the mixing chamber, The powder in the second supply passage is drawn into the mixing chamber through the decompression chamber. The ground improvement device according to claim 2.

4. A third supply passage for supplying gas through the interior of the rod to the monitor, The hardener nozzle injects the gas sent by the third supply passage together with the hardener. The ground improvement device according to claim 1.

5. A fourth supply passage passing through the inside of the rod and supplying liquid to the monitor, The monitor further includes a cutting nozzle that cuts the ground by spraying the liquid delivered by the fourth supply line. The ground improvement device according to claim 1.

6. A fifth supply passage for supplying gas through the interior of the rod to the monitor, The cutting nozzle injects the gas delivered by the fifth supply passage together with the liquid delivered by the fourth supply passage. The ground improvement device according to claim 5.

7. The monitor includes: a discharge port located at a lower end of the rod in an extending direction and through which the liquid of the first supply path is discharged; A drilling tool provided around the discharge port; a valve portion that opens and closes a flow path from the first supply path to the discharge port; Further comprising: The ground improvement device according to claim 1.

8. A ground improvement method using the ground improvement device according to any one of claims 1 to 7, Inserting the rod into the ground; The rod is rotated while the hardening material is sprayed from the hardening material nozzle, and the rod is pulled up to create a ground improvement body in which the hardening material is hardened in the ground. A ground improvement method comprising the steps of:

Images