JP7257983B2 - High-pressure injection stirring method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high pressure injection stirring method mainly for cohesive soil.

The high-pressure jet stirring method includes a method in which compressed air is jetted together with the hardening material by using a multi-pipe rod. The primary purpose of this method of injecting compressed air is to simultaneously inject the hardening material and compressed air so that the compressed air surrounds the jet of hardening material to achieve a pseudo air injection. . In this case, since the cutting distance to the ground to be improved can be lengthened, the improvement diameter is increased.

The second purpose of using compressed air is to supply the compressed air required to obtain the air lift effect required for mud discharge.

Sludge discharge is usually a mud-like fluid that is a mixture of hardening material of cement-based solidifying slurry and soil of the ground to be improved, and must be treated as industrial waste. reduction of the amount of sludge discharged is one of the major issues for the high-pressure jet stirring method involving compressed air.

In Patent Document 1, after drilling to a predetermined depth with a triple tube rod, when the rod is pulled up (during improvement), only cutting water is jetted sideways from the upper two-way high-pressure water nozzle, and a two-way nozzle with a lower step A method of simultaneously injecting cement milk and compressed air so as to surround the cement milk from a directional nozzle is disclosed.

According to the method of the above-mentioned patent document, when discharging sludge, compressed air is not injected from the upper two-way nozzle. It is said that it is possible to speed up the processing speed of ground improvement with a reduced amount of sludge without causing excessive sludge discharge.

JP-A-2003-286717

According to the method of injecting compressed air in the sludge discharge method of Patent Document 1, since the compressed air is injected horizontally from the position of the hardening material injection hole, the compressed air is injected from the rod to the outer periphery of the improved body, and the compressed air is discharged. It can escape from within range of the improvement and erupt from unexpected locations on the surface.

In addition, since compressed air is injected in a direction perpendicular to the sludge discharge hole, the air lift effect is difficult to achieve.In order to secure the air lift effect, it is necessary to increase the amount of injected air, and a large capacity compressor must be used. There were problems such as

In addition, when the soil to be improved is highly viscous, the removal of mud is hindered by air lift alone, increasing the internal pressure in the improved area and reducing the cutting performance.

Therefore, it is an object of the present invention to provide a high-pressure injection stirring method that requires a small capacity compressor to promote sludge discharge, prevents air from escaping from the improved body to the ground, and provides an effective air lift effect. Make it an issue.

In order to achieve the above objects, the present invention is as follows.
(1) In the high-pressure injection stirring method with compressed air,
Cement milk and second compressed air surrounding the cement milk are horizontally injected from the injection port of the rod at the time of forming the improved body, and the first compressed air is injected vertically downward from the tip of the rod without injecting the cement milk . and discharging the generated sludge to the ground surface through the sludge discharge clearance formed around the rod by the first compressed air.
(2) The high-pressure jet stirring method according to (1), wherein the fluidizing agent is simultaneously jetted together with the first compressed air from the tip of the rod.
(3) The high pressure injection stirring method according to (1) or (2), characterized in that the injection pressure of the first compressed air is 0.7 to 1.5 MPa and the injection air amount is 2 to 12 ^Nm3 . .
(4) The high-pressure injection stirring construction method according to any one of (1) to (3), characterized by disposing an aerodynamic force reducing member that protects the injection port of the rod from the first compressed air. .
(5) The high pressure injection stirring method according to any one of (1) to (4), characterized in that the applied ground is cohesive soil.

In addition, "high pressure" in the present invention means a pressure of 20 MPa or higher, for example.

According to the present invention, the role of compressed air is divided into two, one of which is ejected vertically downward from the tip of the rod, and the other is ejected horizontally from the rod as in the conventional case, and at the same time surrounds the cement milk to be ejected. ing. Therefore, the horizontally injected compressed air (hereinafter sometimes referred to as "second compressed air") contributes to the formation of the improved body as before together with the cement milk.

On the other hand, the compressed air (hereinafter sometimes referred to as “first compressed air”) injected vertically downward from the tip of the rod moves the generated mud to the ground through the mud discharge clearance formed around the rod. It is made to discharge on the surface. At this time, since the compressed air is injected vertically downward, a sufficient amount of compressed air is always supplied to the sludge discharge clearance. In addition, the second compressed air that returns to the center of the rod after reaching the outer peripheral portion of the improved body together with the cement milk is also guided to the sludge discharge passage without staying in the improved body, and is immediately discharged along the sludge discharge passage. It becomes a situation where it is easy to be discharged to the ground together with the mud, and the air lift effect is easily exhibited.

As a result, a sufficient air lift effect can be secured even with a small amount of injected air, and a small compressor can exhibit a sufficient air lift effect. In addition, when the soil to be improved has a high viscosity, and even at large depths or large improvement diameters, the airlift alone does not hinder the removal of mud, and prevents the reduction in cutting ability due to the increase in internal pressure in the improvement area. be able to.

As described above, according to the present invention, a high-pressure jet stirring method is provided in which a small-capacity compressor can be used to promote sludge discharge, air is less likely to escape from the improved body to the ground, and an effective air lift effect can be obtained. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram for demonstrating the high pressure injection stirring construction method of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the high pressure injection stirring apparatus for enforcing the high pressure injection stirring construction method of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the high pressure injection stirring apparatus for enforcing the high pressure injection stirring construction method of this invention. It is a schematic block diagram for demonstrating the modification of the high-pressure injection stirring construction method of this invention.

Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram for explaining the high-pressure jet stirring method of the present invention. As for the construction stage of the high-pressure injection stirring method, it is the situation at the time of building an improved body (at the time of pulling up the rod) after cutting the ground.

In FIG. 1, in order to clearly explain the features of the present invention, descriptions of a cutting portion such as a cutting pit and a configuration prior to a swivel for sending compressed air and the like are omitted.

As shown in FIG. 1, the rod 10 used in the high-pressure jet stirring method of the present embodiment is a triple pipe, and a monitor 12 is connected to the tip of the rod body 11 . The rod 10 (that is, the rod body 11 and the monitor 12) has an inner tube, a middle tube and an outer tube (not shown), in which cement milk flows, and in which the middle tube and the outer tube are compressed. Air is circulated. The first compressed air and second compressed air described below may flow through the middle tube and the outer tube, respectively, or vice versa.

As described above, FIG. 1 shows the situation at the time of constructing the improved body (at the time of pulling up the rod) after cutting the ground with the rod 10, so the sludge discharge clearance 15 is formed around the rod 10. .

In this embodiment, the compressed air is divided into two, and one of the first compressed air is jetted vertically downward from the tip 12A of the rod 10 (monitor 12) as indicated by the arrow P in the drawing. Therefore, the first compressed air rises toward the ground surface through the sludge discharge clearance 15 formed around the rod 10 after being injected, as indicated by the arrow P in the drawing.

At this time, since the first compressed air is always sufficiently supplied to the sludge discharge clearance 15, the second compressed air returning to the center of the rod after reaching the outer peripheral portion of the improved body together with the cement milk also enters the improved body. It is guided to the sludge discharge clearance 15 without stagnation, immediately transmitted through the sludge discharge clearance 15, and the soil of the ground to be improved generated during cutting of the ground and the cement milk (cement-based solidification material slurry) hardening material. It becomes a situation that it is easy to discharge to the ground together with the mixed muddy fluid, and the air lift effect is easily exhibited. That is, as indicated by an arrow S in the figure, the air lift effect of the first compressed air causes the air to be discharged to the ground surface.

In this way, since the first compressed air is injected vertically downward, sufficient compressed air is supplied to the mud discharge clearance 15, which is the mud discharge hole, and the air lift effect is likely to be exhibited, and even a small amount of injected air is sufficient. A good air lift effect can be secured. In addition, even a small compressor can exhibit a sufficient air lift effect. Therefore, it is possible to provide a high-pressure jet agitation construction method that makes it difficult for air to escape from the improved body to the ground, and that provides an effective air lift effect.

In addition, when the soil to be improved has a high viscosity, and even at large depths or large improvement diameters, the airlift alone does not delay the removal of mud, and prevents the decrease in cutting ability due to the increase in internal pressure in the improvement area. be able to. In other words, this embodiment, that is, the present invention, is more effective when the applied ground is cohesive soil.

In addition, the second compressed air, which is the cement milk and the surrounding compressed air related to the formation of the improved body, is supplied from the injection port 12B formed on the side surface of the rod 10 (monitor 12) in the horizontal direction as indicated by the arrows R and Q in the figure. It is injected at high pressure into the air, and contributes to the creation of the improved body by simulated injection in the air.

It is known that the second compressed air that surrounds the cement milk and causes a pseudo-injection in the air must have a wind speed of 1/2 or more of the sound speed, and the amount of the compressed air is also a predetermined amount. is necessary. However, with respect to the amount of compressed air, it is necessary to consider temperature and pressure changes due to compression and release, unit weight fluctuations due to these temperature and pressure changes, and pipe pressure loss fluctuations due to these.

Considering the implementation work here, when the injection pressure of the first compressed air is injected from the tip 12A of the rod 10, it is necessary to at least exceed the earth pressure of the slurry mixed improved mud at the tip 12A of the rod 10. Considering the improvement depth of the high-pressure injection stirring method, for example, if the rod tip depth is 50m and the mud unit weight is 1.7tf/ ^m3 , the first compressed air must overcome the earth pressure of about 85tf/ ^m2 and inject. Therefore, a pressure of 1.7×50=85 tf/m ² ≈0.8 to 1.3 MPa is considered necessary considering the margin.

Therefore, considering the above-described implementation, the injection pressure of the first compressed air is preferably 0.7 to 1.5 MPa, more preferably 1.0 to 1.3 MPa. Also, from the results of test construction, the amount of injected air is preferably 2 to 12 Nm ³ , more preferably 3 to 6 Nm ³ .

Here, an additional remark is made about the amount of injected air. The amount of air for assisting the air lift determined by the present inventors from the sludge discharge situation based on the results of several test constructions is as shown in the table below at the injection depth of the first compressed air at the rod tip (at the rod tip position air volume).

However, since air is a compressible fluid, especially at deep depths, the air feed distance increases at the depth of the rod tip, and the compressed air pumped from the ground is further subjected to overburden pressure and groundwater pressure. , the compressed air may be further compressed resulting in a smaller air volume for airlift, reducing the sludge evacuation effect at the rod tip.

Therefore, in many cases, it is necessary to increase the amount of injected air on the ground by considering the above-mentioned factors, depending on the high-pressure slurry discharge amount (improved diameter) and construction depth. Therefore, as the air amount lower limit control value of the first compressed air on the ground, the lower limit value of [Table 1] 1 Nm ³ /min is assumed to be increased to 2 Nm ³ /min. It was set to 12 Nm ³ /min based on construction results.

The reason for the change in the amount of air is as follows. That is, an increase in construction depth increases the airlift distance, and an increase in the amount of high-pressure slurry increases the amount of sludge discharged.

In this embodiment, the fluidizing agent can be simultaneously injected from the tip 12A of the rod 10 together with the first compressed air. In this case, since the viscosity of the discharged mud is lowered, the air lift effect by the first compressed air and the second compressed air is increased, and the discharge of the discharged mud to the ground surface through the discharged mud discharge clearance 15 is more effective. can be done systematically.

As the fluidizing agent, general-purpose ones can be used. For example, naphthalenesulfonate-based, melaminesulfonate-based, polycarboxylate-based and aminosulfonate-based high performance AE water reducing agents, High performance water reducing agents and AE water reducing agents can be used.

FIG.2 and FIG.3 is a schematic block diagram of the high pressure injection stirring apparatus for implementing the high pressure injection stirring construction method of this invention.

FIG. 2 is a high-pressure jet stirrer equipped with two systems of compressors and flow meters for generating and blowing the first compressed air and the second compressed air, and FIG. It is a high-pressure jet agitator equipped with one system of compressors and two systems of flow meters for generating and blowing air.

The high-pressure jet stirring device shown in FIG. 2 has a first compressor 21 for generating and blowing the first compressed air and a second compressor 22 for generating and blowing the second compressed air. These compressors 21 and 22 are connected to a first flow meter 25 and a second flow meter 26 via valves 23 and 24, respectively, and the first and second compressed air flow through these flow meters 25 and 26. After measuring the pressure and air volume at , air is blown into the rod 10 via the swivel 16 . After that, as described above, the sludge is discharged by the air lift effect and the improved body is formed.

According to the apparatus as shown in FIG. 2, the first compressed air and the second compressed air can be controlled by independent system equipment, respectively, so that the high pressure injection stirring method of the present invention can be easily performed.

On the other hand, the high-pressure jet stirring device shown in FIG. ing. In this case, for example, the first flow meter 35 controls the first compressed air, and the second flow meter 36 controls the second compressed air. In this case, since there is only one compressor, its capacity must be sufficient to cover the injection pressure and the amount of air of the first compressed air and the second compressed air.

FIG. 4 is a schematic configuration diagram for explaining a modification of the high-pressure jet stirring method of the present invention. FIG. 4 shows, in relation to the rod 10 shown in FIG. The difference is that a member 41 is provided.

According to this modification, the aerodynamic force reduction member 41 functions as a cover for the injection port 12B, so the cutting energy of the cement milk and the second compressed air injected from the injection port 12B is not reduced. Therefore, it is possible to efficiently and effectively perform improved body formation and sludge discharge.

The shape of the member is not particularly limited as long as it covers the injection port 12B, but by using the aerodynamic force reduction member 41, it is possible to prevent the member from being damaged by the pressure of the first compressed air. Further, the aerodynamic force reducing member 41 may have any shape as long as it can prevent the first compressed air involved in the air lift effect from influencing the second compressed air surrounding the cement milk.

Although several embodiments of the invention have been described above, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

Reference Signs List 10 rod 11 rod body 12 monitor 12A tip of rod (monitor) 12B injection port 15 sludge discharge clearance 16 swivel 21 first compressor 22 second compressor 23, 24, 33, 34 valve 25, 35 first flow meter 26, 36 Second flow meter 31 Compressor

Claims (5)

In the high-pressure injection stirring method with compressed air,
Cement milk and second compressed air surrounding the cement milk are horizontally injected from the injection port of the rod at the time of forming the improved body, and the first compressed air is injected vertically downward from the tip of the rod without injecting the cement milk . and discharging the generated sludge to the ground surface through the sludge discharge clearance formed around the rod by the first compressed air. 2. The high-pressure jet stirring method according to claim 1, wherein the fluidizing agent is simultaneously jetted together with the first compressed air from the tip of the rod. 3. The high pressure injection stirring method according to claim 1 or 2, wherein the injection pressure of the first compressed air is 0.7 to 1.5 MPa, and the injection air amount is 2 to 12 Nm ³ . 4. The high-pressure jet stirring method according to any one of claims 1 to 3, characterized in that an aerodynamic force reducing member is provided to protect said jet port of said rod from said first compressed air. The high pressure injection stirring method according to any one of claims 1 to 4, characterized in that the applied ground is cohesive soil.

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