JP2000045262A - High pressure injection stirring construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve drilling efficiency and effectively cope with soil improvement of very deep area by effectively using a down-the-hole hammer of hydraulic driving. SOLUTION: An injection rod 10 constituted by continuously providing an injection head 5 having a double nozzle 4, a valve body 7 with a differential pressure regulation valve built in it and a down-the-hole hammer 9 of hydraulic driving on its head end part is prepared. Thereafter, the injection rod 10 is rotated and lowered into a foundation 30, a hole 31 is drilled by a drilling bit 8 while actuating the down-the-hole hammer 9 by supplying low hydraulic pressure in the injection rod 10 at first, thereafter, the differential pressure regulation valve in the valve body 7 is closed by changing low pressure water over to extra-high pressure water, cutting and stirring of the ground is carried out by injecting extra-high pressure water accompanied by air from the double nozzle 4, the extra-high pressure water is changed over to high pressure grout when cutting and stirring of a planned formation area is finished, the injection rod 10 is rotated and lifted up while injecting grout accompanied by air from the double nozzle 4, and a cutting and stirring layer 32 is replaced with a grout injecting layer 34.

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 high-pressure injection stirring method for forming an improved column by injecting grout (ground improvement agent) into the ground at high pressure.

[0002]

2. Description of the Related Art In a high-pressure injection stirring method, a high-pressure grout is used alone, or compressed air or ultra-high-pressure water is injected from an injection nozzle provided on the peripheral surface of the tip while rotating or lowering an injection rod into the ground. In recent years, its use has been expanding since it is possible to efficiently create large-diameter improved columns by using a method of cutting and stirring and mixing the ground using the energy of the high-pressure jet fluid. For example, JP-B-56-44206, JP-B-58-27364.
No.). Further, as this high-pressure injection stirring method, the injection rod is rotated down into the ground together with the core material tube to form an improved column, and the core material tube is left inside the improved column to form the improved column. There is also a method of reinforcing the core material so as to reinforce it (for example, JP-A-3-208986).

[0003] By the way, depending on the target ground, a hard layer may exist on the way from the ground surface to the planned improvement area.
In this case, it is not possible to smoothly penetrate the injection rod to the planned improvement region simply by rotating and lowering the injection rod. Therefore, conventionally, when the ground in which such a hard layer exists is targeted, for example, Japanese Patent Application Laid-Open No. 10-885
No. 64, a drill bit is provided at the tip of an injection rod, and the ground is mechanically drilled by the drill bit in response to the rotation of the injection rod.
(Page 4, column 6, lines 29-38) or JP-A-9-7192
Prior to the ground improvement using an injection rod, as described in Japanese Patent Publication No. 9, whether drilling was performed in advance using a dedicated drilling machine (page 4, column 5, lines 24 to 37). .

[0004]

However, according to the countermeasures for drilling by the drill bit provided at the tip of the injection rod as described above, since a simple rotating method is used, for example, a boulder or a bedrock can be removed. Drilling becomes difficult when a hard layer is included, especially in deep areas (for example, 5
0m or more), the drilling takes a long time, and the drilling bit wears out too much and must be replaced frequently. There was a problem that complaints remained. In addition, according to the countermeasures for pre-drilling with a dedicated drilling machine, a separate drilling process is required, which inevitably extends the construction period,
There was a problem that the construction cost also increased.

By the way, as a method for efficiently performing drilling, use of a down-the-hole hammer has been conventionally known. This down-the-hole hammer is generally designed so that the hammer section is actuated by air pressure to apply an impact force to the drill bit at the tip, but recently, by using water pressure in place of the above-mentioned air pressure, it is possible to further cut the hole. A down-the-hole hammer with enhanced hole capability has also been developed and is already marketed under the trade name Wassara (Sandvik).

The present inventors have paid attention to this hydraulically driven down-the-hole hammer, and if it is provided at the tip of the above-mentioned injection rod, the hydraulic pressure required for its driving can be easily secured. He was convinced that drilling could be performed efficiently on the ground, and that it would be possible to effectively cope with ground improvements at high depths.

The present invention has been made based on the above-mentioned considerations, and an object of the present invention is to improve drilling efficiency by effectively utilizing a hydraulically driven down-the-hole hammer, thereby improving the ground at high depths. Another object of the present invention is to provide a high-pressure injection stirring method that can effectively cope with the problem.

[0008]

In order to achieve the above object, a first aspect of the present invention is directed to an injection method in which a double nozzle is provided on the end of a rod body having first and second flow paths therein. A head, a valve body with a built-in differential pressure valve that closes when a fluid pressure exceeding the set pressure is applied, and a down-the-hole hammer that applies an impact load to the drill bit at the tip by operating the hammer section by water pressure An injection rod is prepared, and first, low-pressure water having a pressure equal to or lower than the set pressure is supplied to the first flow path. The injection rod is rotated down into the ground while operating the down-the-hole hammer with the low-pressure water. When the injection head reaches the upper limit of the planned improvement area, the low pressure water supplied to the first flow path is switched to ultra high pressure water sufficiently higher than the set pressure, and the differential pressure valve is closed. And at the same time Supplying compressed air to the second flow path, cutting and stirring the ground by injecting a mixed fluid of water and air from the double nozzle at a high pressure, and when the injection head reaches the lower limit of the plan improvement area, The ultrahigh-pressure water supplied to the first flow path is switched to high-pressure grout, and the air supplied to the second flow path is adjusted so that a mixed fluid of grout and air or only grout is supplied from the double nozzle. The injection rod is rotated up while high-pressure injection is performed to create an improved pillar in the planned improvement area.

The operating pressure of the hydraulically driven down-the-hole hammer is usually in the range of 10 to 18 MPa (about 100 to 180 kg / cm ² ). The low pressure water is also in this pressure range, and therefore, the set pressure is a value exceeding this upper limit of 18 MPa, for example, 20 M
Set to about Pa (200 kg / cm ² ). It is desirable that the ultrahigh-pressure water has a pressure of 35 to 45 MPa (about 350 to 450 kg / cm ² ).

In the first aspect of the present invention, the set pressure at which the differential pressure valve in the valve body is closed is set to be higher than the operating pressure of the hydraulically driven down-the-hole hammer, so that the first flow path is first opened. When the low-pressure water having a pressure equal to or lower than the set pressure is supplied, the low-pressure water is supplied to the down-the-hole hammer through the differential pressure valve, and the down-the-hole hammer is operated to drill holes with high efficiency. Then, when the low pressure water is switched to ultra high pressure water sufficiently higher than the set pressure at the stage when the injection head reaches the upper limit of the plan improvement area, the differential pressure valve closes, and the mixed fluid of water and compressed air is discharged. The grout is injected from the heavy nozzle, the ground is cut and agitated with high efficiency, and thereafter, the grout is injected into the ground efficiently by spraying grout instead of the ultra high pressure water.

Further, the second invention omits the step of cutting and stirring the ground by injecting ultra-high pressure water and compressed air from the first invention, and in this case, it is provided on the rod body of the injection rod. One flow path may be used, and the injection nozzle provided in the injection head may be a single nozzle. In the second aspect of the present invention, first, low-pressure water that is equal to or less than the set pressure is supplied to the flow path, and the injection rod is rotated down into the ground while operating the down-the-hole hammer with the low-pressure water. When the injection head reaches the upper limit of the planned improvement area, the low pressure water to be supplied to the flow path is switched to a grout having a pressure higher than the set pressure, the differential pressure valve is closed, and grouting is performed from the injection nozzle. High pressure injection to create an improved pillar in the planned improvement area,
In this case, the improved column can be created only by the downward stroke of the injection rod, and the construction efficiency is improved.

Further, the third invention is applied to a high-pressure jet stirring method for reinforcing a core material. In this case, the same injection rod as that used in the second invention is prepared, and this injection rod is used. Inserting into a core pipe with a check valve, first, supplying low pressure water below the set pressure to the flow path, while operating the down the hole hammer with this low pressure water,
When the injection rod reaches the upper limit of the planned improvement area, the low pressure water supplied to the flow path is reduced from the set pressure when the injection rod reaches the upper limit of the planned improvement area by rotating and lowering the injection rod into the ground before the core material pipe. Switching to high-pressure grout, closing the differential pressure valve, injecting high-pressure grout from the injection nozzle to create an improved column in the planned improvement area, and then withdrawing the injection rod from the core material tube and injecting instead Insert the machine into the core tube, open the check valve provided on the core tube, and inject grout around the core tube secondarily. Created.

In carrying out the second and third aspects of the present invention, when the grout is injected from the injection nozzle at a high pressure, compressed air may be injected together. In this case, the ground is combined with the compressed air. The grouting distance to the grout can be extended and a larger diameter improved column can be created.

[0014]

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

FIG. 1 to FIG. 5 show a first embodiment of the present invention. When the first embodiment is carried out, as shown in FIGS. 2 to 5, a double nozzle 4 is provided on the distal end of a rod body 3 having a double pipe structure including an outer pipe 1 and an inner pipe 2. An injection rod 10 comprising an injection head 5 provided with a valve body 7 having a differential pressure valve 6 therein, and a hydraulically driven down-the-hole hammer 9 having a drill bit 8 at its tip is prepared. The rod 10 is supported by a rotation and elevation unit of a construction machine (not shown), and a high-pressure pump and an air compressor in the construction plant are connected to the upper end of the rod 10 by a swivel (not shown). In the rod body 3, the first flow path a in the inner pipe 2 serves as a high-pressure water or grout supply path, and the annular second flow path b between the outer pipe 1 and the inner pipe 2 is compressed. In this case, the high-pressure pump in the construction plant is connected to the first flow path a, and the air compressor is connected to the second flow path b. become. The high-pressure pump in the construction plant has a function of obtaining high-pressure grout of about 35 to 45 MPa in addition to a function of obtaining low-pressure water of about 10 to 18 MPa to ultra-high-pressure water of about 35 to 45 MPa. One of these low-pressure water, ultra-high-pressure water, and high-pressure grout is selectively supplied to the first flow path a of the rod body 3.

Here, as shown in FIG. 3, the injection head 5 provided with the double nozzle 4 has an outer cylinder 11 and an inner cylinder 12.
The passage c in the inner cylinder 12 is connected to the first passage a in the rod body 3 so as to communicate with the injection hole on the core side of the double nozzle 4. As a passage, the annular passage d between the outer cylinder 11 and the inner cylinder 12 serves as a communication path that connects the second flow path b in the rod body 3 to the injection hole outside the double nozzle 4. It has become.

Also, a valve body 7 having a built-in differential pressure valve 6
Has a main body 13 screwed to the lower end of the outer cylinder 11 of the injection head 5. A stepped hole 14 communicating with the passage c in the inner cylinder 12 of the injection head 5 is formed in the main body 13, and the differential pressure valve 6 has the stepped hole 14 at an upper side in the main body 13. It is arranged to close. The differential pressure valve 6 is kept open at all times, and when the pressure of the fluid (water or grout) supplied to the first flow path a in the rod body 3 exceeds a set pressure (for example, 20 MPa). The valve is closed. Therefore, when a fluid (low-pressure water) lower than the set pressure is supplied to the first flow path a in the rod body 3, the differential pressure valve 6 maintains the open state, and the low-pressure water is When the ultrahigh-pressure water or the high-pressure grout exceeding the set pressure is supplied to the first flow path a through the stepped hole 14 in the down-the-hole hammer 9, the differential pressure valve 6 closes, The ultra high pressure water or high pressure grout is sent to the double nozzle 4 side.

On the other hand, the down-the-hole hammer 9 is connected to the connecting member 1 screwed to the main body 13 of the valve body 7.
5 and a threaded connection with the connection member 15,
And a hammer 17 disposed in the cylinder 16. More specifically, the connecting member 15 is connected to the main body 13 by screwing a frusto-conical screw protrusion 15a provided at the upper end thereof into a tapered screw hole 13a provided in the main body 13 of the valve body 7. ing. The connecting member 15 and the cylinder 16 are provided with a male screw 15b provided at a lower end of the connecting member 15 and a screw 1
It is connected by screwing to 6a. A shaft hole 18 is formed in the connecting member 15, and the low-pressure water that has passed through the differential pressure valve 6 passes through the cylinder hole 1 through the shaft hole 18.
It is supplied to the hammer part 17 in 6. Hammer part 17
Has a function of vertically moving a piston (not shown) by accumulating and releasing the low water pressure, and the piston hits the shaft portion 20 of the drill bit 8 so that the drill bit 8 Is designed to receive an impact force. The connecting member 15 and the cylinder 16 of the down-the-hole hammer 9 and the main body 13 of the valve body 7 and the outer cylinder 1 of the rod main body 3 have substantially the same outer diameter.
Therefore, the injection rod 10 has substantially the same thickness over its entire length.

As shown in FIGS. 4 and 5, the drill bit 8 is fitted to a guide tube 21 fitted and fixed to the cylinder 16 and movably fitted in the guide tube 21 so as to be movable slightly in the axial direction. A ring-shaped outer bit 22 and an inner bit 25 which is connected to the outer bit 22 by meshing the teeth 23 and 24 with each other. The impact force of the hammer 17 from the rear end of the inner bit 25 The receiving shaft portion 20 is extended. Outer bit 22
Has a large-diameter portion 22a having a diameter substantially the same as the outer diameter of the guide tube 21, and the large-diameter portion 22a protrudes from the guide tube 21. . The inner bit 25 is composed of a number of chips 26
Are positioned so that the distal end thereof slightly protrudes downward from the outer bit 22. On the other hand, on the inner surface of the outer bit 22 and the outer surface of the inner bit 25, three teeth are arranged at equal intervals in the circumferential direction (at 120 ° intervals).
Three longitudinal grooves 27 and 28 are formed in the form of notches 3 and 24 (FIG. 5).
The tooth portion 24 left between the outer bit 22 and the vertical groove 27
, The detachment from the outer bit 22 is allowed.

Such a down-the-hole hammer 9 is commercially available from Sandvik under the trade name "Wassara", and here, "Wassara" is used as it is.

A construction procedure performed by using the injection rod 10 having the above structure will be described below with reference to FIGS. At the time of construction, as described above, the injection rod 10 is supported by a rotation and elevation unit of a construction machine (not shown), and a high-pressure pump and an air compressor in the construction plant are connected to the upper end thereof. After the preparation is completed, the set pressure of the high-pressure pump 11 is adjusted to supply low-pressure water of 10 to 18 MPa to the first flow path a in the rod body 3, and as shown in FIG. Is rotated down into the ground 30. At this time, the pressure of the low-pressure water is changed to the differential pressure valve 6 in the valve body 7.
Pressure (about 20 MPa), the differential pressure valve 6 is kept open, so that most of the low-pressure water is pumped from the injection head 5 through the valve body 7 to the down-the-hole hammer 9. . As a result, the hammer portion 17 in the down-the-hole hammer 9 operates, and an impact force is applied from the hammer portion 17 to the rod 20 of the drill bit 8, and the drill bit 8 applies an impact corresponding to the impact force to the ground 30. The ground 30 is efficiently drilled as the injection rod 10 is rotated and lowered.

Here, since the outer bit 22 constituting the drill bit 8 has a larger diameter than the injection rod 10, the hole 31 formed by the above-described drilling is
It has a sufficient diameter to make 0 smoothly penetrate. Also, in the present embodiment, the first
A part of the low-pressure water supplied to the flow path a is pumped to the double nozzle 4 and is jetted therefrom at a considerable pressure around the injection rod 10. It becomes larger than the hole diameter. The low-pressure water consumed by the hammer portion 17 of the down-the-hole hammer 9 is supplied to the outer grooves 22 and the inner grooves 25 of the inner bits 25.
Since the water is discharged to the front of the drill bit 8 through 7, 28, the drill bit 8 is forcibly cooled by the discharged water,
Its wear is also reduced.

The formation of the hole 31 by the above drilling proceeds,
As shown in FIG. 1, the injection head 5 has the upper limit A of the planned improvement area.
, Adjust the set pressure of the high pressure pump 11
The low-pressure water supplied to the first flow path a is switched to ultra-high-pressure water of about 35 to 45 MPa, and at the same time, compressed air is supplied from the air compressor to the second flow path b in the rod body 3. First
The ultra-high pressure water supplied to the flow path a closes, the differential pressure valve 6 of the valve body 7 closes, and the ultra high pressure water (mixed fluid) with air is emitted from the double nozzle 4 of the injection head 5 in the radial direction. The ground 30 is strongly cut and agitated (pre-cutting) by the mixed fluid having a large injection energy. As a result, a large-diameter cutting and stirring layer 32 is formed in the ground 30,
The cutting and stirring layer 32 gradually expands downward as the injection rod 5 rotates downward. A part of the cutting slime generated at this time is discharged to the slime pit 33 (FIG. 2) on the ground through the hole 31 of the above-described drilling, and is further sent to a sludge pond by a sludge discharging means (not shown). You.

When the formation of the cutting agitation layer 32 by the above-mentioned cutting agitation reaches the lower limit B of the planned improvement area as shown in FIG. 1, the high pressure pump in the construction plant is switched to the grout source and the rod body is switched. 3 to the first flow path a
As shown in the figure, the grouting rod 10 is rotated up while supplying the high-pressure grout of about 35 to 45 MPa and continuously supplying the compressed air to the second flow path b in the rod body 3. As a result, high-pressure grout (mixed fluid) with air is ejected from the double nozzle 4 of the injection head 5 in the radial direction, and the grout is injected into the cutting and stirring layer 32 to form the grout injection layer 34. . At this time, the surplus slime in the cutting and stirring layer 32 on the grout injection layer 34 is discharged to the slime pit 33 through the hole 31 by the pressure of the grout and the air lift effect, but at this stage, since the injection of water is stopped. In addition, the induced discharge of grout is significantly suppressed, and the amount of grout in excess slime is minimized.

The injection of the high-pressure grout with the air described above gradually expands in accordance with the rotation rise of the injection rod 10, and when a quick-hard grout is used, as shown in FIG. The grout injection layer 34 partially solidifies from the stage before reaches the planned improvement region upper limit A, and the growth of the hard improved columns 35 starts. In this way, when grouting is completed up to the upper limit A of the planned improvement area, the supply of grout and compressed air to the rod body 3 is stopped,
The rotation and lifting unit of the construction machine is largely moved upward, and the injection rod 10 is pulled out of the ground 30 as shown in the figure, whereby the construction of one improved pillar 35 in the planned improvement area is completed. In the first embodiment, in particular,
Since high-pressure water, which was originally required for forming the cutting and stirring layer 32 by pre-cutting, is shared as a drive source for the down-the-hole hammer 9, the construction is extremely efficient, and the economic benefit is great.

The pre-cutting step in the first embodiment may be omitted depending on the properties of the ground. In this case, after drilling to the upper limit A of the planned improvement area using the down-the-hole hammer 9, the low-pressure water supplied to the first flow path a in the rod body 3 is converted into high-pressure grout of about 35 to 45 MPa. At the same time as switching, compressed air is supplied from the air compressor to the second flow path b in the rod body 3,
While injecting high pressure grout (mixed fluid) with air in the radial direction from the double nozzle 4 of the injection head 5, the injection rod 10 is rotated down to form a grout injection layer,
When the injection head 5 reaches the lower limit B of the plan improvement area,
The injection of grout and compressed air is stopped, and the injection rod 10 is withdrawn from the ground 30. By doing so, an improved column can be created only by the downward stroke of the injection rod 10, so that the construction efficiency is improved.

FIGS. 6 and 7 show a second embodiment of the present invention. The second embodiment is applied to a high-pressure grouting method for reinforcing a core material.
A core pipe having substantially the same injection rod 10 as that used in the first embodiment and having a plurality of check valves 40 arranged circumferentially and axially on the pipe wall. 41
Is prepared (FIG. 7). As the down-the-hole hammer 9 at the tip of the injection rod 10, a hammer bit 8 having a diameter larger than the outer diameter of the core tube 41 is selected.

Then, the injection rod 10 is inserted into the core tube 41, and the double nozzle 4 and the down-the-hole hammer 9 on the tip side thereof are positioned so that they protrude from the core tube 41. 10 to 10 in the first flow path a in the main body 3
A low-pressure water of 18 MPa is supplied, and as shown in FIG. 6, the injection rod 10 and the core tube 41 are lowered while rotating in mutually opposite directions. At this time, similarly to the first embodiment, the pressure of the low-pressure water is set to the set pressure of the differential pressure valve 6 in the valve body 7 (20
(Approximately MPa), the differential pressure valve 6 is kept open, so that most of the low-pressure water is pumped from the injection head 5 through the valve body 7 to the down-the-hole hammer 9. As a result, the down-the-hole hammer 9 is actuated to apply an impact force to the drill bit 8, and the drill bit 8 applies an impact corresponding to the impact force to the ground 30 while the injection rod 10 rotates and descends. The ground 30 is drilled with high efficiency. The diameter of the hole drilled by the down-the-hole hammer 9 is larger than the outer diameter of the core tube 41 by selecting the large-diameter drill bit 8. 41 penetrates smoothly.

When the drilling by the down-the-hole hammer 9 reaches the upper limit A of the planned improvement area, the low-pressure water supplied to the first flow path a in the rod body 3 is switched to a high-pressure grout of about 35 to 45 MPa. At the same time, compressed air is supplied from the air compressor to the second flow path b in the rod body 3. Then, as shown in FIG. 6, high-pressure grout (mixed fluid) accompanied by air is jetted from the double nozzle 4 of the injection head 5 in the radial direction, and the grout injection layer 43 is formed.
The grout injection layer 43 expands downward as the injection rod 10 rotates down. When the grout injection layer 43 is formed to the lower limit B of the planned improvement area, supply of grout and compressed air to the injection head 5 (double nozzle 4) is stopped.

Next, as shown in FIG.
Is pulled out from the core tube 41, and the core tube 41 is
The injector 44 is now inserted into it, leaving it at zero.
As the injection machine 44, for example, Japanese Unexamined Patent Publication No. 6-228940
The one described in Japanese Patent Application Laid-Open Publication No. H07-260, can be used. This device comprises a pair of upper and lower expandable members (made of rubber) 45 which can be expanded and contracted, and a driving means (not shown) for expanding and contracting the expanded members 45. By deforming, it can be fixed at an arbitrary position in the core tube 41. The grout is fed to the grinder 44 through a grove 46 extending from the ground.
After discharging between the pair of swelling bodies 45 of the injector 44, the check valve 40 is opened to squirt around the core tube 41, whereby the core tube 41 is wrapped around the core tube 41. A small-diameter grout injection layer (secondary injection layer) 46 is formed in close contact.

The formation of the secondary injection layer 46 is based on the core material tube 41.
Starting from the lower end portion of the mold, the injecting machine 44 is pulled up at a predetermined pitch, and a pair of swelling bodies 45 are swelled at each pulling position to repeat grout injection, whereby the secondary injection layer 46 gradually rises upward. Expand. When the formation of the secondary injection layer 46 is completed over the entire area of the grout injection layer (primary injection layer) 43, the injector 44 is pulled out from the core tube 41.
Wait for the hardening of each injection layer 43, 46. As a result, the core tube 4
As shown in FIG. 6, a plurality of primary improvement columns 47 in which the primary injection layer 43 is hardened and a plurality of secondary improvement columns 48 in which the secondary injection layer 46 is hardened are formed around the core material tube 41. Is buried in the strong improved pillar, and a strong improved pillar for reinforcing the core material is created.

[0032]

As described above, according to the high-pressure injection stirring method of the present invention, drilling is efficiently performed by using a hydraulically driven down-the-hole hammer, and the high pressure Injection makes it possible to effectively cope with hard ground existing in the reach to the planned improvement area, as well as ground improvement in deep areas where long distance drilling is required. I do.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an implementation process of a first embodiment of the present invention.

FIG. 2 is an enlarged schematic view showing an intermediate stage in the first embodiment.

FIG. 3 is a sectional view showing a structure of an injection rod used in the first embodiment.

FIG. 4 is a sectional view showing a structure of a drill bit of a down-the-hole hammer.

FIG. 5 is a plan view showing the structure of a drill bit of a down-the-hole hammer.

FIG. 6 is a schematic diagram showing an implementation process of a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a combined state of an injection rod and a core tube in a second embodiment.

[Explanation of symbols]

Reference Signs List 1 outer pipe, 2 inner pipe, 3 rod body 4 double nozzle, 5 injection head 6 differential pressure valve, 7 valve body 8 drilling bit, 9 down the hole hammer 10 injection rod, 30 ground 31, 42 hole by drilling, 32 cutting Stirrer layer 32 Cutting stirrer layer, 34, 43 Grout injection layer 35 Improvement column, 47 Primary improvement column, 48 Secondary improvement column 40 Check valve, 41 Core pipe, 44 Injector 46 Secondary grout injection layer

Claims (5)

[Claims] An injection head provided with a double nozzle on the peripheral surface at the tip of a rod body having first and second flow paths therein, and a differential valve for closing the valve when a fluid pressure exceeding a set pressure is applied. Prepare an injection rod consisting of a valve body with a built-in pressure valve, and a down-the-hole hammer that activates the hammer section by water pressure and applies an impact force to the drill bit at the tip. Supplying low-pressure water that is equal to or less than the set pressure, while operating the down-the-hole hammer with this low-pressure water, the injection rod is rotated down into the ground to perform drilling, and the injection head reaches the upper limit of the planned improvement area. Then, while switching the low pressure water supplied to the first flow path to ultra high pressure water sufficiently higher than the set pressure to close the differential pressure valve, and simultaneously supplying compressed air to the second flow path, The double nozzle When a mixed fluid of water and air is injected at high pressure to cut and agitate the ground, and when the injection head reaches the lower limit of the planned improvement area, the ultrahigh-pressure water supplied to the first flow path is switched to high-pressure grout, Adjusting the air to be supplied to the second flow path, while injecting only a mixed fluid of grout and air or only grout from the double nozzle at a high pressure, rotating the injection rod to raise the improved column in the planned improvement area. A high-pressure jet agitation method characterized by development. 2. The high-pressure jet stirring method according to claim 1, wherein the low-pressure water has a pressure of 10 to 18 MPa, and the ultra-high-pressure water has a pressure of 35 to 45 MPa. 3. An injection head having an injection nozzle provided on a peripheral surface at a distal end of a rod body having a flow path therein, and a valve body having a built-in differential pressure valve which closes when a fluid pressure exceeding a set pressure is applied. By preparing an injection rod formed by connecting a down-the-hole hammer that applies an impact force to a drill bit at the tip by operating a hammer unit by water pressure, first, supply low-pressure water having a pressure equal to or less than the set pressure to the flow path. Then, while operating the down-the-hole hammer with this low-pressure water,
Drill a hole by rotating and lowering the injection rod into the ground,
When the injection head reaches the upper limit of the plan improvement area, the low pressure water supplied to the flow path is switched to a grout having a pressure higher than the set pressure, the differential pressure valve is closed, and the grout is injected from the injection nozzle at a high pressure. A high-pressure jet agitation method characterized by forming improved columns in the improved area. 4. An injection head provided with an injection nozzle on a peripheral surface at a tip end of a rod body having a flow path therein, and a valve body having a built-in differential pressure valve which closes when a fluid pressure exceeding a set pressure is applied. By preparing an injection rod formed by connecting a down-the-hole hammer that applies an impact force to the drill bit at the tip by operating the hammer section by water pressure, inserting the injection rod into a core pipe with a check valve. First, the low pressure water is supplied to the flow path at a pressure lower than the set pressure, and while the down-the-hole hammer is operated by the low pressure water, the injection rod is rotated down into the ground ahead of the core tube. When the injection head reaches the upper limit of the planned improvement area, the low pressure water supplied to the flow path is switched to a grout having a higher pressure than the set pressure, the differential pressure valve is closed, and the injection nozzle is closed. An improved column is created in the planned improvement area by injecting a high-pressure out, and after that, the injection rod is pulled out from the core material pipe, and instead, an injection machine is inserted into the core material pipe, and the check provided on the core material pipe is performed. A high-pressure jet stirring method comprising opening a valve and injecting grout around the core tube. 5. The injection head of the injection head is formed of a double nozzle, and two injection nozzles are provided inside the rod body. When grout is injected from the injection nozzle, compressed air is injected together. Claim 3 or 4
High-pressure injection stirring method described in 1.