JP2739641B2 - Ground improvement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground improvement method, and more particularly, to a ground improvement method in which a hollow core material is buried in a ground improvement body formed by a high-pressure jet stirring method to increase a supporting force.

[0002]

2. Description of the Related Art In a high-pressure injection stirring method, an injection rod is rotated and moved in a ground, and a ground improvement agent is mixed with water or air in a direction perpendicular to the injection rod from an injection nozzle at the tip thereof. High-pressure injection, a method of forming a columnar improved body by stirring and mixing the soil improver and surrounding earth and sand, is less affected by the soil quality, and can improve the ground over a wide range with a single construction. Because of their excellent adhesion to each other, they are often used for construction of earth retaining walls and water blocking walls (for example, Japanese Patent Publication No. 50-14803, Japanese Patent Publication No. 51
-8493).

On the other hand, recently, a method of burying a hollow core material in a ground improvement body formed by the high-pressure injection stirring method to increase the supporting force has been developed.
No. 088986. This method is
The injection rod inserted into the pipe is excavated into the ground ahead of the pipe while rotating, and during this excavation, the ground improvement agent is injected at high pressure from the tip of the injection rod in a direction perpendicular to this and the ground around the pipe is excavated. The pipe is reinforced so that the pipe remains in the pipe as it is, and the pipe reinforces the pipe as a core material, and the bearing capacity of the ground is remarkably increased.

[0004]

However, according to the ground improvement method described in JP-A-3-208986, when the high-pressure jet stirring method, which is the basis of the method, is performed.
Since it is necessary to use a cement milk-based filler that does not cause clogging of the injection nozzle, the filler (ground improver) injected into the ground is liable to cause breathing, and the core pipe and ground improver There was a problem that the bonding strength (adhesive strength) with the resin was insufficient, and there was another concern about the supporting force.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to improve an improved body formed by the high-pressure injection stirring method without impairing the advantages of the method and to bury the improved body. The object is to increase the bonding strength with the core material.

[0006]

In order to solve the above-mentioned problems, the present invention is directed to a method of rotating an injection rod inserted into a hollow core material from an injection nozzle at the tip of the injection rod in a direction perpendicular to the injection rod. A first step of injecting the ground improver with high pressure to penetrate the core material into the ground integrally with the injection rod, and withdrawing the injection rod from the core material, and instead inserting the injection machine into the core material While feeding the injection machine at a predetermined pitch in the axial direction of the core material, the ground improving agent is pressure-fed to the injection machine at each feed position, and the check valve provided on the core material is opened by the pressure of the ground improvement agent to open the core material. And a second step of secondary injecting a ground strengthening agent around the periphery.

[0007] In the ground improvement method constructed as described above, first, a ground improvement agent is injected at a high pressure from an injection rod in the manner of a high pressure injection stirring method to form an improved body.
A core material is wrapped with the improved material, and then a ground improving agent such as a cement mortar-type injecting agent, which is unlikely to cause breathing, is secondarily injected around the core material. Can be increased.

In the present invention, it is desirable to use a cement milk-based filler as the ground improver in the first step and a cement mortar filler as the ground improver in the second step. In the present invention, a drilling step of drilling a guide hole in the ground may be provided prior to the first step, and the first step may be performed along the guide hole. The present invention also provides a nozzle for ejecting high-pressure water or compressed air at the tip of the core material, and when executing the first step, ejects high-pressure water or compressed air from the nozzle,
It is also possible to create a flow of fluid from the front end to the rear end in the core material, and to discharge excess slime to the ground using the propulsive force of this fluid. In the present invention, the type of the core material is arbitrary, and for example, a steel pipe or a fiber-reinforced plastic tube can be used. Also,
It is desirable to provide irregularities on the outer surface of the core material.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the present invention. In carrying out the present invention, steel pipe (core material)
1 and an injection rod 3 provided with an injection nozzle 2 at the tip. As shown in FIGS. 2 and 3, the steel pipe 1 is provided with a plurality of annular projections 4 on its outer surface in advance, and a plurality of check valves 5 arranged on the pipe wall in the axial and circumferential directions. Keep it. The annular projection 4 is formed, for example, by connecting the ring-shaped member to the steel pipe 1.
And fixed by welding. As the check valve 5, for example, JP-A-6-2289
No. 40 can be used. This is composed of an annular support 6 having a locking piece 6a crossing in the radial direction, and an elastically deformable disk-shaped valve body 7 fitted in the support 6 and opened in the steel pipe 1. It is fitted into the stepped through hole 8. The check valve 5 restricts the inflow of earth and sand from the outside into the steel pipe 1 by seating the peripheral portion of the valve body 7 on a step in the through hole 8, while the valve is controlled by the internal pressure applied to the steel pipe 1. The through hole 8 is opened by elastically deforming the body 7 outward. It is desirable to provide a drill bit 9 at the tip of the injection nozzle 2.

At the time of construction, as shown in FIG. 4, the steel pipe 1 and the injection rod 3 are supported by two rotating units 12 and 13 which are mounted in advance so as to be interlocked with the leader 11 of the self-propelled excavating machine 10. . At this time, the two are positioned so that the injection nozzle 2 at the tip of the injection rod 3 inserted into the steel pipe 1 projects from the tip of the steel pipe 1, and the rear end of the steel pipe 1 is driven into the rotating unit 12 on the front side in the driving direction. The rotation unit 13 on the rear side in the direction supports the intermediate portion of the injection rod 3.
The steel pipe 1 is a guide 1 provided at the tip of the leader 11.
4 is also supported. A swivel 15 is attached to the rear end of the injection rod 3, and a hose 16 extending from a grout pump (not shown) is connected to the swivel 15.

After the above preparation is completed, the arm 1 of the excavating machine 10
The leader 11 is vertically set on the ground A by the operation of 0a, and the steel pipe 1 and the injection rod 3 are driven into the ground A integrally by rotating the steel pipes 1 and the injection rods 3 by the operation of the rotating units 12 and 13. Then, when the tip of the injection rod 3 has penetrated from the surface by a predetermined distance L ₁ as shown in FIG. 1,
A cement milk-based injection agent (ground improvement agent) is pumped into the injection rod 3 through the hose 16 and the swivel 15.
Then, the cement milk-based filler is injected from the injection nozzle 2 at the tip of the injection rod 3 as a jet stream in a direction perpendicular to the injection rod 3, and the earth and sand around the injection rod 3 is stirred and mixed with the cement milk-based filler. You. By this stirring and mixing, a columnar mixing layer 17 having a predetermined diameter D is formed around the injection rod 3, and the mixing layer 17 gradually expands downward in accordance with the penetration of the injection rod 3. The steel pipe 1 penetrates into this mixed layer 17.

Next, the mixed layer 1 over a predetermined depth L ₂
After the 7 is formed, the injection rod 3 is pulled out from the steel pipe 1 as shown in FIG. 1, and instead, the injection machine 18 is inserted into the steel pipe 1 as shown in FIG. Injector 1
As for 8, for example, those described in JP-A-6-228940 can be used. As shown in FIG. 5, this apparatus includes a pair of upper and lower expandable members (made of rubber) 19 and a driving unit (not shown) for expanding and contracting the expandable members 19. The swelling body 19 can be fixed at an arbitrary position in the steel pipe 1 by swelling deformation. A cement mortar-based injection agent (ground improvement agent) is fed to the injection machine 18 through an injection pipe 20 extending from the ground. Into the closed pressure chamber 22 formed between the swelling bodies 19 of the liquid crystal.

Next, as shown in FIG. 1, the injector 18 is pulled up at a predetermined pitch from the distal end side of the steel pipe 1, and a pair of swelling bodies 19 are swelled and deformed by a driving means at each of the pulling up positions, so that the pressure is increased. A pressure chamber 22 is formed in the pressure chamber 22.
Pump the cement mortar-based filler through. Then, the check valve 5 provided in the steel pipe 1 is opened by the pressure in the pressure chamber 22, and the mixed layer (primary mixed layer) 1 around the steel pipe 1 is opened.
The cement mortar-based injecting agent is secondarily injected into 7. As a result, as shown in FIGS. 1 and 2, a secondary mixing layer 23 is formed around the steel pipe 1 in close contact with the steel pipe 1, and the secondary mixing layer 23 gradually rises as the injector 18 is pulled up. Extend to And the length L ₂ of the primary mixed layer 17
After completing the secondary injection for the area, the injector 18 is withdrawn from the steel pipe 1 and the hardening of the mixed layers 17, 23 is awaited.

As a result, as shown in FIG. 1, around the steel pipe 1, the primary improved layers 24 and
The secondary improved body 25 in which the next mixed layer 23 is hardened is formed in multiple layers, and the steel pipe 1 is embedded in the strong improved layer. Moreover, the cement mortar-based filler used for the secondary injection does not easily cause bleeding, so that the adhesive force between the secondary improved body 25 and the steel pipe 1 is significantly increased, and the supporting force of the ground improvement layer is significantly increased. Become like Especially in the first embodiment, since the annular projection 4 is provided on the outer surface of the steel pipe 1, the adhesive force between the secondary improved body 25 and the steel pipe 1 is further increased. Moreover, since we started with the formation of primary mixed layer 17 from a position lowered from the surface by a distance L _1,
Even if the cement milk-based filler used for forming the mixed layer 17 causes bleeding, it is refilled by secondary injection from the steel pipe 1 and safety is enhanced.

Here, on the outer surface of the steel pipe 1, instead of the annular projection 4, for example, as shown in FIGS. 6 to 8, an annular groove 4a (FIG. 6), a spherical projection 4b (FIG. 7), or Various irregularities such as the spline-shaped teeth 4c (FIG. 8) can be provided. In any case, the adhesive force between the steel pipe 1 and the improved body further increases, and the supporting force of the ground improvement layer increases.

When the primary mixed layer 17 is formed, water or air may be mixed with the cement milk-based injecting agent and simultaneously spouted. In this case, the cement milk-based injecting agent is sprayed. The range is enlarged, and the primary mixed layer 17 having a larger diameter can be formed with the same injection pressure. Also, a coagulation accelerator may be mixed into the cement mortar-based injecting agent to be injected secondarily. In this case,
Since the secondary mixed layer 17 solidifies quickly, the construction period can be shortened. Further, the steel pipe 1 may be finally filled with a reinforcing material such as a steel material, so that the supporting force is further increased. Further, the steel pipe 1 and the pouring rod 3 may be extended while extending each other. In this case, the ground can be deepened.

FIG. 9 shows a second embodiment of the present invention. A feature of the second embodiment is that the steel pipe 1 and the injection rod 3 are formed while the mixed layer 17 is formed by high-pressure injection of the cement milk-based injection from the injection rod 3.
And a hole drilling process is provided prior to the process of integrally penetrating the ground A (the first process). This drilling step is shown in FIG.
As shown in (1) and (2), a step of inserting a drilling rod 27 having an eccentric extension bit 26 at the tip into the steel pipe 1 to be a pile body, and sinking the steel pipe 1 while drilling by rotating the drilling rod 27. () And a step () of pulling out the steel pipe 1 together with the drilling rod 27 after sinking the steel pipe 1 to a predetermined depth. By this drilling step, a guide hole 28 having a diameter slightly larger than the diameter of the steel pipe 1 is formed in the ground A.

In the second embodiment, thereafter, the same steps as those in the first embodiment are executed along the guide holes 28. That is, the steel pipe 1 and the injection rod 3 penetrate along the guide hole 28 to form the primary mixed layer 17 (). After the steel pipe 1 penetrates to a predetermined depth, the injection rod 3 is pulled out from the steel pipe 1 ( Then, the injector 18 is inserted into the steel pipe 1 to form the secondary mixed layer 23 around the steel pipe 1 (). In the second embodiment, since the injection rod 3 and the steel pipe 1 penetrate along the guide hole 28 formed in advance, it is extremely easy to penetrate these into the ground, and the workability of ground improvement is improved. improves. Further, since the steel pipe 1 is used as it is in the drilling step, there is no waste. The method of forming the guide hole 28 is arbitrary, and another method without using the eccentric extension bit 26 can be adopted.

As described above, when forming the primary mixed layer 17 by injecting the ground improving agent from the injection nozzle 2 at the tip of the injection rod 3 with high pressure, surplus slime is generated between the steel pipe 1 and the surrounding ground layer. It is discharged to the ground through the gap,
When the viscous ground is used or when the construction is performed diagonally or horizontally, it is difficult to discharge the surplus slime, and it may be difficult to form the primary mixed layer 17 stably.

FIGS. 10 to 13 show a third embodiment including the above-mentioned measures against excess slime. Book 3
In the embodiment of the present invention, in order to forcibly discharge the surplus slime to the ground through the inside of the steel pipe 1, a master coupling 30 described later and a mud swivel 31 are provided at the rear end of the steel pipe 1 to be cast. The extension pipes 32 are connected in order, and a piping unit 33 is disposed in the steel pipe 1. As shown in FIG. 13, the piping unit 33 includes a plurality (here, two) of fluid pipes 35 each having an upward nozzle 34 at the distal end.
, A circumscribed ring 36 and an inscribed ring 37 for fixing the position of the fluid pipe 35, and a base end (nozzle 34)
And a ring-shaped hollow header 38 connected to the side opposite to the side provided with. The inner diameter of the outer ring 36 is set to substantially the same value as the inner diameter of the steel pipe 1.
Is set to a value obtained by subtracting slightly more than twice the diameter of the fluid pipe 35 from the inner diameter of the steel pipe 1, and therefore, the fluid pipe 35 is
The pipe unit 33 is extended along the inner surface of the steel pipe 1 with the pipe unit 33 inserted into the steel pipe 1. This piping unit 33 is inserted into the steel pipe 1 until its circumscribed ring 36 abuts on the rear end of the steel pipe 1, as shown in FIG. It will be positioned upward.

On the other hand, the master coupling 30 is shown in FIG.
As well shown in FIGS. 12 and 13, an annular projection 39 is provided at an intermediate portion of the inner surface in the longitudinal direction.
9 are provided with female screw portions 40 and 41 at the front and rear portions. The master coupling 30 is integrated with the steel pipe 1 by screwing one female thread 40 into a female thread 1 a provided on the outer periphery of the rear end of the steel pipe 1. One side of the annular projection 39 of the master coupling 30 has an annular groove 42.
When the master coupling 30 is screwed into the steel pipe 1 as described above, the annular groove 4 is provided.
2, the hollow header 38 of the piping unit 33 is fitted. The master coupling 30 is provided with a communication passage 43 that communicates the annular groove 42 with the rear end.

On the other hand, the extension pipe 32 is screwed and connected to the other female thread portion 41 of the master coupling 30. The extension pipe 32 is connected to the rear end of the master coupling 30. In this state, the sludge swivel 31 is provided. The extension pipe 32 is provided with a through hole 44 facing the mud swivel 31, and a shielding plate 45 for slidably guiding the injection rod 3 and closing the upper passage from the through hole 44 is provided therein. ing. Also,
As shown in FIG. 11, the sludge swivel 31 is provided with a sludge outlet 46 communicating with the through hole 44 of the extension pipe 32 and a water or air supply port 47 communicating with the communication passage 43 of the master coupling 30. A sludge hose 48 extending from a mud reservoir is connected to the sludge outlet 46, and a pressure feeding pipe 49 extending from a high-pressure pump or an air compressor is connected to the water or air supply port 47, respectively. In addition, the rotation unit 12 for rotating the steel pipe 1 grips the extension pipe 32.

In the third embodiment, when the ground improving agent is injected at a high pressure from the injection nozzle 2 at the tip of the injection rod 3 to form the primary mixed layer 17, the feed pipe 49, the mud swivel 31, High-pressure water or compressed air is supplied to the fluid pipe 35 through the communication passage 43 of the master coupling 30. Then, the high-pressure water or the compressed air is jetted upward from the nozzle 34 at the tip of the fluid pipe 35 slightly inside the tip opening of the steel pipe 1, and the excess slime generated by the injection of the soil improver into the steel pipe 1 1 flows into the steel pipe 1 through the opening at the tip, and rises inside the steel pipe 1 by the effect of an ejector or an air lift. The excess slime that has risen inside the steel pipe 1 flows into the sludge swivel 31 from the through hole 44 of the extension pipe 32 and is discharged from the sludge outlet 46 to a sludge reservoir (not shown) via the sludge hose 48. Is done. At this time, the amount of surplus slime discharged is adjusted by controlling the pressure of high-pressure water or compressed air supplied to the nozzle 34, whereby the primary mixed layer 17 is formed stably.

After the primary mixed layer 17 is formed, the master coupling 30 is screwed so that the upper portion including the master coupling 30, the extension pipe 32 and the mud swivel 31 is removed from the steel pipe 1. These are lifted up integrally with the injection rod 3 and the piping unit 33 inside the steel pipe 1 is pulled out from the steel pipe 1. Thereafter, as in the first and second embodiments, the injector 18 is inserted into the steel pipe 1 to form a secondary mixed layer 23 around the steel pipe 1. Here, as shown in FIG. 11, by attaching a drill bit 50 having an inner and outer diameter expanding at the tip of the steel pipe 1, when the steel pipe 1 penetrates, the nozzle 3
4 can be prevented from directly hitting, and the damage can be prevented beforehand. In the third embodiment, the fluid pipe 35 including the nozzle 34 is arranged inside the steel pipe 1. However, in the present invention, the fluid pipe 35 is fixed in position along the outer surface of the steel pipe 1. It may be provided in a special way.
However, in this case, the ground A together with the steel pipe 1 is used as a consumable.
Will be left inside. Further, a larger number of the fluid pipes 35 may be provided and used separately for high-pressure water and for compressed air.

In the above three embodiments, the ground improvement around one steel pipe (core material) has been described. However, if the present method is carried out vertically and horizontally so that the ground improvement layers overlap each other, a predetermined range can be obtained. Needless to say, the ground can be improved. In addition, if this method is continuously performed in one direction while the ground improvement layers are wrapped with each other, it is possible to form a retaining wall or a water blocking wall having excellent strength. In addition, steel pipe 1 as a core material
Since it has a great resistance not only to the pushing force but also to the pulling force due to the adhesion to the surrounding improved body, it can be used as a foundation pile as it is. Further, the present invention provides
Although the steel pipe 1 in the above two embodiments may be replaced with a fiber reinforced plastic tube, in this case, the ground improvement once formed as well as having sufficient strength as a core material like the steel pipe 1 When the layer is excavated later, the excavation becomes easier.

[0027]

As described above in detail, according to the soil improvement method according to the present invention, the core material is wrapped with the improved body formed by the high-pressure injection stirring method, and the ground is injected secondarily through the core material. Since the adhesive strength between the improved body and the core material is enhanced by the agent, the effect of significantly increasing the supporting force of the improved ground is exhibited.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention in the order of steps.

FIG. 2 is a perspective view showing an example of a surface state of a steel pipe used in the present invention.

FIG. 3 is a sectional view showing an example of a check valve structure used in the present invention.

FIG. 4 is a front view showing a driving state of the steel pipe and the injection pipe in the first embodiment of the present invention.

FIG. 5 is a schematic view showing an example of the structure of an injector used in the present invention.

FIG. 6 is a perspective view showing another example of the surface state of the steel pipe used in the present invention.

FIG. 7 is a perspective view showing still another example of a surface state of a steel pipe used in the present invention.

FIG. 8 is a perspective view showing still another example of a surface state of a steel pipe used in the present invention.

FIG. 9 is a cross-sectional view showing a second embodiment of the present invention in the order of steps.

FIG. 10 is a front view showing a driving state of a steel pipe and an injection pipe according to a third embodiment of the present invention.

FIG. 11 is a cross-sectional view showing the inside and the upper structure of a steel pipe used in the third embodiment.

FIG. 12 is an enlarged sectional view showing the inside and upper structure of a steel pipe used in the third embodiment.

FIG. 13 is a perspective view showing a structure of a piping unit used in the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel pipe (core material) 2 Injection nozzle 3 Injection rod 4 Projection (irregularity) of the outer surface of a steel pipe 5 Check valve 10 Driving machine 12 Rotary unit 13 Rotary unit 17 Primary mixing layer 18 Injector 23 Secondary mixing layer 24 Primary improved body 25 Secondary improved body 26 Drilling bit 28 Guide hole 30 Master coupling 31 Sludge swivel 32 Extension pipe 33 Piping unit 34 Nozzle 35 Fluid pipe A Ground

Claims (7)

(57) [Claims] 1. While rotating an injection rod inserted into a hollow core material, a ground improvement agent is injected at a high pressure from an injection nozzle at the tip of the injection rod in a direction perpendicular to the injection rod, and is integrally formed with the injection rod. A first step of penetrating the core material into the ground, and withdrawing the injection rod from the core material, inserting an injection machine into the core material instead, and feeding the injection machine at a predetermined pitch in the axial direction of the core material. A second step of pressure-feeding the soil improver to the injection machine at each feed position, opening the check valve provided on the core material by the pressure of the soil improver, and secondary injecting the ground strengthener around the core material; A ground improvement method comprising: 2. The soil improvement method according to claim 1, wherein a cement milk-based injection agent is used as the ground improvement agent in the first step, and a cement mortar injection agent is used as the ground improvement agent in the second step. . 3. The method according to claim 1, wherein prior to the first step, a drilling step of drilling a guide hole in the ground is set, and the first step is performed along the guide hole. Ground improvement method. 4. A nozzle for jetting high-pressure water or compressed air is provided at the tip of the core material, and when the first step is performed, high-pressure water or compressed air is jetted from the nozzle and the tip is injected into the core material. 2. The ground improvement method according to claim 1, wherein a flow of a fluid is generated from the fluid to the rear end, and excess slime is discharged to the ground using the propulsive force of the fluid. 5. The ground improvement method according to claim 1, wherein a steel pipe is used as the core material. 6. The fiber-reinforced plastic tube according to claim 1, wherein the core material is a fiber-reinforced plastic tube.
Ground improvement method described in section. 7. The ground improvement method according to claim 5, wherein irregularities are provided on an outer surface of the core material.