Injection apparatus for use in high-pressure injection agitation method

Abstract

To obtain an optimum upper and lower separation distance capable of obtaining the good finished shape and quality of an improved body by suppressing the mutual interference of the injection pressure of upper and lower injection nozzles and mixing inferiority in an injection device equipped with the upper and lower two stage injection nozzles.SOLUTION: This injection device 1 is used for a high pressure injection stirring construction method for creating a soil improvement body 7 in the ground by cutting the ground by injecting high pressure water 5 from an upper stage injection nozzle 3 of an upper stage, and pulling up the ground while injecting a curing material 6 from a lower stage injection nozzle 4 of a lower stage. A vertical distance Y between the upper ejection nozzle 3 and the lower ejection nozzle 4 is set to 72 to 120cm.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an injection device used in a high-pressure injection mixing method in which high-pressure water is injected from an injection device equipped with two separate injection nozzles, one above the other, to cut the ground while mixing and mixing hardening materials, thereby creating a ground improvement body underground. [Background technology]

[0002] A high-pressure jet mixing method has been known for some time, in which high-pressure water is jetted from a jetting device attached to the tip of a rod to cut the ground while mixing and stirring hardening materials, thereby creating a ground improvement body underground.

[0003] The injection methods of the high-pressure jet mixing method can be broadly classified into three types depending on the number of jetting fluids used: a single-phase flow method (single-pipe type) in which only the hardening material is injected, a two-phase flow method (double-pipe type) in which a double-pipe rod is used to inject the hardening material while entraining air, and a three-phase flow method (triple-pipe type) in which a triple-pipe rod is used to inject high-pressure water from the upper nozzle to cut the ground, while injecting hardening material and air at high pressure from the lower nozzle. Note that the three-phase flow method also includes a method in which high-pressure water is injected from the upper nozzle while entraining air to cut the ground.

[0004] In the three-phase flow method, an injection device equipped with two stages of injection nozzles spaced apart from each other is attached to the tip of a rod, and high-pressure water is injected from the upper stage injection nozzle to cut the ground, while hardener and air are injected at high pressure from the lower stage injection nozzle.The injection device is then rotated or swung while being pulled up to create a ground improvement body underground (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 57-3911 Summary of the Invention [Problem to be solved by the invention]

[0006] In the three-phase flow method described above, simultaneous injection is performed from upper and lower injection nozzles that are arranged at a distance from each other above and below, so in many cases the injection nozzles are arranged in opposite directions to prevent interference with each other, and the separation distance between the upper and lower injection nozzles is generally set to the minimum structural distance (about 40 cm) to reduce over-excavation during drilling.

[0007] However, if the distance between the upper and lower spray nozzles is short, the spray device will rotate and spray within a closed space in the ground, which is likely to cause interference in spray pressure and poor mixing due to the inclusion of cutting water from the upper stage, and this may have a negative impact on the shape and quality of the improved body.

[0008] Furthermore, the injection mechanism of the high-pressure injection mixing method can be either a full-circle injection type, which can create cylindrical improved bodies, or a swinging injection type, which can create partially shaped improved bodies, depending on the shape of the improved body to be created. The full-circle injection type has a mechanism for the upper and lower injection nozzles to spray in opposite directions, while the swinging injection type has a mechanism for the upper and lower injection nozzles to spray in the same direction. Here, in the case of the swinging injection type, the upper and lower injection nozzles are arranged facing in opposite directions, and the upper and lower tiers spray in the same direction, so compared to the full-circle injection type, the effects of the above-mentioned injection pressure interference and poor mixing due to the inclusion of cutting water in the upper tier are greater, making the improved body more likely to have poor shape or poor quality.

[0009] On the other hand, if the distance between the upper and lower jets is too great, there is a risk that the improved body will not be in good shape or of poor quality.

[0010] Therefore, the main object of the present invention is to provide an injection device for use in a high-pressure injection mixing method, which has an optimum vertical separation distance in an injection device equipped with two stages of injection nozzles spaced apart from each other, which suppresses interference between the injection pressures of the upper and lower injection nozzles and poor mixing, thereby obtaining a good finished shape and quality of the improved body. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention according to claim 1 provides an injection device used in a high-pressure injection mixing method in which high-pressure water is injected from an upper-stage injection nozzle on the upper stage to cut the ground, and a hardening material is injected from a lower-stage injection nozzle on the lower stage while being pulled up, thereby creating a ground improvement body in the ground. There is provided an injection device used in a high-pressure injection and mixing method, characterized in that the upper-stage injection nozzle and the lower-stage injection nozzle are separated by a vertical distance of 72 to 120 cm.

[0012] In the invention described in claim 1 above, in an injection device used in a high-pressure injection mixing method for creating a ground improvement body underground by injecting high-pressure water from an upper-stage injection nozzle to cut the ground and then injecting a hardening material from a lower-stage injection nozzle while pulling it up, the vertical separation distance between the upper-stage injection nozzle and the lower-stage injection nozzle is set to 72 to 120 cm. As will be described in detail later, when experiments were conducted in which ground improvement bodies were created by changing the separation distance in various ways, it was found that when the separation distance was set within the above range, interference between the injection pressures of the upper and lower injection nozzles and poor mixing could be suppressed, and the shape and quality of the improved body were good.

[0013] The present invention according to claim 2 provides an injection device used in the high-pressure injection mixing method according to claim 1, wherein the high-pressure water injected from the upper injection nozzle is an aqueous polymer solution containing a highly water-absorbent polymer.

[0014] In the invention described in claim 2 above, the high-pressure water sprayed from the upper-stage spray nozzle is a polymer aqueous solution, so compared to water spraying, the diffusion of powder particles is suppressed, and attenuation over distance is reduced, resulting in improved cutting ability. [Effects of the Invention]

[0015] As explained above in detail, according to the present invention, by optimizing the vertical separation distance between the two stages of upper and lower injection nozzles, interference between the injection pressures of the upper and lower injection nozzles and poor mixing can be suppressed, resulting in good shape and quality of the improved body. [Brief explanation of the drawings]

[0016] [Figure 1] This is an outline diagram of construction work for full-perimeter improvement. [Figure 2] This is an outline diagram of construction work for partial improvements. [Figure 3] (A) shows full-perimeter improvement, and (B) shows partial improvement. The top is a plan view of the ground improvement body, and the bottom is a side view of the injection device 1. [Figure 4] FIG. 1 is a side view of the injection device 1 used in the experiment. [Figure 5] This is a graph showing the relationship between the separation distance Y and the improved body diameter D in the case of full-circumference improvement. [Figure 6] This is a graph showing the relationship between the separation distance Y and the improved body volume V in the case of full-circumference improvement. [Figure 7] 10 is a graph showing the relationship between the separation distance Y and the amount of sludge discharged L in the case of full perimeter improvement. [Figure 8] This is a graph showing the relationship between the separation distance Y and the improved body diameters r1, r2, and D in the case of partial improvement. [Figure 9] 10 is a graph showing the relationship between the separation distance Y and the improved body volume V in the case of partial improvement. [Figure 10] 10 is a graph showing the relationship between the separation distance Y and the amount of sludge discharged L in the case of partial improvement. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0018] As shown in Figures 1 and 2, the injection device 1 (hereinafter simply referred to as "injection device 1") used in the high-pressure injection mixing method of the present invention is configured to be attachable to the tip of a concentric triple-tube rod 2 that has an internal flow path structure for pressurizing high-pressure water, hardener, and air, and has an internal concentric triple-tube flow path structure similar to the rod 2.

[0019] The injector 1 has a set of two injection nozzles (upper injection nozzle 3 and lower injection nozzle 4) on its side. The injector 1 is used for full-circumference improvement, in which a roughly cylindrical ground improvement body is formed around the entire circumference by lifting up the rod 2 while rotating it. As shown in Figs. 1 and 3(A), the injector 1 has one upper injection nozzle 3 that injects in one direction and one lower injection nozzle 4 that injects in the opposite direction. The injector 1 is used for partial improvement, in which a partial ground improvement body with a fan-shaped cross section is formed on both sides by lifting up the rod 2 while swinging it. As shown in Figs. 2 and 3(B), the injector 1 has two upper injection nozzles 3 that inject in opposite directions from each other and two lower injection nozzles 4 that inject in the same direction and are also provided at positions that are opposite in the diameter direction of the outer circumferential surface.

[0020] The upper stage jet nozzle 3 is located closer to the base end (upper side in the vertical direction, on the rod 2 side) than the lower stage jet nozzle 4, and is capable of jetting high-pressure water 5 while entraining air.

[0021] The lower stage injection nozzle 4 is provided on the tip side (bottom side in the up-down direction) of the upper stage injection nozzle 3, and is capable of injecting the hardening material.

[0022] The structure of the injection device 1 is not particularly limited as long as it can create a ground improvement body 7 in the ground by injecting high-pressure water from the upper injection nozzle 3 to cut the ground and then pulling up while injecting hardening material from the lower injection nozzle 4.

[0023] In the injection device 1 according to the present invention, the vertical separation distance Y between the upper injection nozzle 3 and the lower injection nozzle 4 is set to 72 to 120 cm, and particularly preferably 90 to 100 cm.

[0024] By setting the separation distance Y within this range, as will be shown in the experiments described later, interference between the injection pressures of the upper and lower injection nozzles and poor mixing can be suppressed, resulting in a good finished shape and quality of the ground improvement body 7. As will be described later, the effect of improving the finished shape of the improved body and reducing the amount of sludge discharge reaches its peak when the separation distance Y is 90 to 100 cm, and a range of ±20% of each value is set as the preferred range.

[0025] Typically, the separation distance Y between the upper and lower jet nozzles is generally set to 20 to 50 cm, and setting it to 72 to 120 cm as in the present invention is far beyond the range anticipated by those skilled in the art. Furthermore, by setting the separation distance Y within this range, it is possible to maximize the effects of suppressing a decrease in cutting ability due to interference between the high-pressure water 5 from the upper jet nozzle 3 and the hardening material 6 from the lower jet nozzle 4, a decrease in the quality of the improved body due to poor mixing of the hardening material, and an increase in the amount of discharged mud, effects that would not have been anticipated by those skilled in the art.

[0026] Here, the high-pressure water sprayed from the upper jet nozzle 3 may be water alone or an aqueous polymer solution containing a highly water-absorbent polymer.

[0027] The superabsorbent polymer is a hydrophilic polymer particle with a crosslinked structure, capable of absorbing approximately 10 to 500 times its own weight and characterized by its resistance to moisture release even under pressure. The water-absorbing effect of such a water-absorbent polymer is exerted by the osmotic pressure generated by the difference in ion concentration between the inside and outside of the polymer. Therefore, the electrical conductivity of the solvent mixed and stirred with the superabsorbent polymer can be adjusted by adding an electrolyte such as sodium chloride, thereby changing the mass ratio of absorbed water to the mass of the polymer particles. Water is used as the solvent, and tap water is particularly suitable for use at cutting sites.

[0028] The type of superabsorbent polymer is not particularly limited, and it is preferably considered to be at least one type selected from the group consisting of starch-based, cellulose-based, and synthetic polymer-based polymers.

[0029] Among the above-mentioned superabsorbent polymers, the synthetic polymer-based superabsorbent polymer sodium polyacrylate is particularly suitable for use because it is excellent in both performance and cost.

[0030] Sodium polyacrylate superabsorbent polymer is a gel of partially cross-linked acrylic acid polymer sodium salt with a three-dimensional network structure, lightly cross-linked by adding a cross-linking agent to sodium acrylate (CH2=CH-COONa). Conventional cross-linking agents can be used.

[0031] It is known that when the superabsorbent polymer sodium polyacrylate absorbs water, the carboxyl groups dissociate sodium ions into a gel, causing it to swell to a degree that reaches 100 to 1000 times its own weight in pure water.

[0032] Furthermore, when the amount of crosslinking agent added to the sodium polyacrylate superabsorbent polymer is increased relative to the amount of sodium acrylate, the resulting gel becomes harder and its water absorption capacity decreases, whereas when the amount of crosslinking agent added is decreased, the resulting gel becomes softer and its water absorption capacity increases.

[0033] Furthermore, as a special sodium polyacrylate superabsorbent polymer, there can be mentioned the use of a sodium polyacrylate superabsorbent polymer having a double structure of a shell and a core, in which the surface of a superabsorbent polymer polymerized with a crosslinking agent is further crosslinked.

[0034] In this sodium polyacrylate superabsorbent polymer with a dual shell-core structure, the thicker the outer shell, the harder the gel becomes and the less water it absorbs, while the thinner the shell, the softer the gel becomes and the more water it absorbs.

[0035] Although the shell and core are usually crosslinked via an ester bond, there are also sodium polyacrylate superabsorbent polymers in which the shell and core are crosslinked via an ether bond, which has excellent alkali resistance and electrolytic resistance. In the present invention, it is more preferable to use a sodium polyacrylate superabsorbent polymer in which the shell and core are crosslinked via an ether bond.

[0036] In addition to the above characteristics, the dissociation of sodium ions in the superabsorbent polymer sodium polyacrylate also depends on the conditions under which the gel is placed, such as pH and electrolyte concentration, so other superabsorbent polymers can be appropriately selected and used depending on the conditions of use.

[0037] The concentration of the aqueous polymer solution can be adjusted appropriately depending on the water absorption performance of the highly water-absorbent polymer, the ion concentration of the absorbed water, the properties of the object to be cut, and the like.

[0038] Generally, the viscosity tends to increase when a highly water-absorbent polymer is used, while the viscosity tends to decrease when a less water-absorbent polymer is used. Therefore, it is desirable to set the concentration to obtain the desired clay polymer solution, taking into account the water-absorbent properties of the highly water-absorbent polymer used. By using the polymer solution of this embodiment, the jet core region in the flow velocity distribution diagram shown in Figure 1 can be extended, improving cutting efficiency.

[0039] In addition, in order to adjust the water absorption rate of the water-absorbing polymer, an electrolyte such as sodium chloride may be added to the aqueous polymer solution.

[0040] As the hardening material, any known hardening material such as a slurry cement-based hardening material (cement milk) or a slag-based hardening material can be used without any restrictions.

[0041] To carry out ground improvement using the device configured as described above, first, a sludge discharge pit 20 is constructed on the ground surface, as shown in Figures 1 and 2, and a hole is drilled to a predetermined depth using a drilling machine. When drilling using a drilling machine, a drilling bit may be attached to the lower end of the injection device 1, and the hole may be drilled by rotating the rod 2 while discharging drilling water as needed, or a casing may be drilled, and then the rod 2 with the injection device 1 attached to its tip may be inserted into the hole, and the casing may then be pulled out, inserting the injection device 1 into the ground to a predetermined depth.

[0042] Next, in the process of pulling up the rod 2 while rotating (Fig. 1, Fig. 3(A)) or swinging (Fig. 2, Fig. 3(B)), high-pressure water 5 is sprayed from the upper jet nozzle 3, and hardening material 6 is sprayed at high pressure from the lower jet nozzle 4 while entraining air, to create a solidified body of hardening material 6 in the ground. Here, in the early stages of starting to pull up, it is desirable to spray only high-pressure water 5 while pulling up, in order to spray hardening material 6 into the cutting area by the high-pressure water 5, and then, once the lower jet nozzle 4 reaches the cutting area by the high-pressure water 5, to spray hardening material 6 from the lower jet nozzle 4 at high pressure.

[0043] Here, high-pressure water 5 is sprayed from the upper jet nozzle 3 at 20 to 60 MPa and 20 to 100 L / min, and air is sprayed from the lower jet nozzle 4 at 0.3 to 1.5 MPa and 1 to 5 m 3 It is preferable that the curing agent 6 is sprayed at 20 to 50 MPa and 50 to 250 L / min while the curing agent 6 is entrained at 20 to 50 MPa and 50 to 250 L / min.

[0044] In addition, instead of the configuration in which high-pressure water 5 is sprayed from the upper jet nozzle 3 and the hardener 6 is sprayed from the lower jet nozzle 4 while entraining air, a configuration in which high-pressure water 5 is sprayed from the upper jet nozzle 3 while entraining air, and the hardener 6 is sprayed from the lower jet nozzle 4 may be adopted, or a configuration in which high-pressure water 5 is sprayed from the upper jet nozzle 3 while entraining air, and the hardener 6 is sprayed from the lower jet nozzle 4 while entraining air may be adopted.

[0045] In this way, when the hardening material 6 is injected at high pressure from the lower jet nozzle 4 into the already loosened ground, the ground particles and the hardening material 6 are stirred and mixed, and a solidified body is created in the target ground area using the hardening material 6. At this time, because the upper jet nozzle 3 and the lower jet nozzle 4 are separated by an optimum distance in the vertical direction, interference between the jet pressures of the upper and lower jet nozzles and poor mixing can be suppressed, resulting in a good shape and quality of the improved body. [Example]

[0046] A ground improvement body 7 was created in a field test using an injection device 1 with a different separation distance Y between the upper injection nozzle 3 and the lower injection nozzle 4, and a test was conducted to confirm the effect of the separation distance Y on the finished shape and quality of the ground improvement body 7.

[0047] The tests were conducted both in the case of full-circumference improvement and in the case of partial improvement, and the diameter and volume of the head of the ground improvement body 7 were measured when the separation distance Y was changed, as well as the amount of sludge that flowed into the sludge discharge pit 20.

[0048] The test method, as shown in Figure 4, involved using three types of spraying equipment with different separation distances Y (Y = 38.8, 100, 150 cm), spraying a polymer aqueous solution containing a superabsorbent polymer as high-pressure water 5 from the upper spray nozzle 3, and spraying cement milk as a hardening agent 6 from the lower spray nozzle 4 while entraining air, to create a full-perimeter or partial improved ground body, and measuring the finished shape (diameter and volume) of the created ground improved body 7 and the amount of sludge discharged during construction. For the test, a mix test was conducted using soil collected from the site, and the improvement specifications were determined. The improvement specifications are shown in Table 1.

[0049] [Table 1]

[0050] The measurement results of the finished shape and amount of sludge discharged from the ground improvement body 7 excavated after curing (28 days) are shown in Figures 5 to 7 for the full-perimeter improvement and in Figures 8 to 10 for the partial improvement, respectively.

[0051] In the case of full-circumference improvement, the average improved body diameter D was D = 2.8 m when the separation distance Y was 38.8 cm, D = 2.25 m when the separation distance Y was 150 cm, as shown in Figure 5, while it was largest at D = 3.8 m when the separation distance Y was 100 cm, resulting in an improved diameter that was 1.3 to 1.6 times larger than the other cases, and when converted to the improved body volume shown in Figure 6, it was 1.8 to 2.8 times larger.

[0052] In addition, the amount of sludge discharged during construction, L, is as shown in Figure 7. The planned amount of sludge discharged is L0 = 5.52 m 3 Whereas, when the separation distance Y is 38.8 cm, L = 7.59 m 3 , when the separation distance Y is 150 cm, L = 7.25 m 3 The amount of sludge discharged was about 1.3 times more than the planned amount of sludge L0, but when the separation distance Y was 100 cm, L = 5.12 m 3 The result was lower than the planned sludge discharge volume L0.

[0053] In the case of full perimeter improvement, as shown in the graphs of Figures 5 to 7, if each measurement point is connected by a smooth curve and the separation distance Y at the peak value of this curve is found to be at a position of approximately 90 cm, it will be found that by setting the separation distance Y to approximately 90 cm in the case of full perimeter improvement, the finished shape and quality of the ground improvement body 7 will be optimal and the amount of sludge discharged can be minimized.

[0054] The results of the full-perimeter improvement experiment show similar trends in the partial improvement experiment shown in Figures 8-10. In the partial improvement experiment, as shown in Figures 8-10, if a smooth curve is drawn between each measurement point and the separation distance Y at the peak of this curve is calculated, it is approximately 100 cm. In other words, in partial improvement, a separation distance Y of approximately 100 cm optimizes the shape and quality of the ground improvement body 7 and minimizes the amount of sludge discharged. The optimal separation distance Y for partial improvement is larger than that for full-perimeter improvement. This is likely because, in full-perimeter improvement, the upper and lower jet nozzles 3 and 4 spray in opposite directions, whereas in partial improvement, the upper and lower jet nozzles 3 and 4 spray in the same direction. This can lead to reduced cutting performance due to jet pressure interference, and the inclusion of cutting water can lead to insufficient addition of hardener or poor mixing.

[0055] From the above test results, it can be seen that there is a correlation between the shape of the improved body and the amount of sludge discharged, and that if the shape of the improved body per the same amount of injection (cutting water, hardening material) into the ground becomes larger, the injection rate λ (injection amount / improved body volume) decreases, thereby reducing the amount of excess sludge discharged.

[0056] As mentioned above, an optimum finished shape and reduction in the amount of sludge discharged can be achieved when the separation distance Y between the upper jet nozzle 3 and the lower jet nozzle 4 is 90 to 100 cm. Furthermore, taking into consideration the measurement conditions, geological conditions, injection conditions, etc., a preferred range for the separation distance Y can be set by providing a fluctuation band of approximately ±20% for each measurement value, and the preferred range for this separation distance Y can be 72 to 120 cm, with a lower limit of 72 cm, which is -20% of 90 cm, and an upper limit of 120 cm, which is +20% of 100 cm. [Explanation of symbols]

[0057] 1...injection device, 2...rod, 3...upper injection nozzle, 4...lower injection nozzle, 5...high-pressure water, 6...hardening material, 7...ground improvement body

Claims

1. This is an injection device used in a high-pressure injection mixing method in which high-pressure water is injected from the upper-stage upper injection nozzle to cut the ground, and hardening material is injected from the lower-stage lower injection nozzle while being pulled up, thereby creating a ground improvement body underground. An injection device used in a high-pressure injection mixing method, characterized in that the upper stage injection nozzle and the lower stage injection nozzle are separated by a vertical distance of 72 to 120 cm.

2. 2. A spraying device used in a high-pressure spray mixing method according to claim 1, wherein the high-pressure water sprayed from the upper spray nozzle is an aqueous polymer solution containing a highly water-absorbent polymer.

Images