JP3974937B2 - Ground improvement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The soil improvement method and construction machine according to the present invention relate to improvement of soft ground.
[0002]
[Prior art]
Conventional methods for improving soft ground include a method of jetting and stirring an injection material at ultra-high pressure and a method of mechanically jetting and stirring using a large machine.
[0003]
The conventional ground improvement method mainly consists of an agitation agitation method using an ultra-high pressure injection and an auger agitation method using a large machine. In the ultra-high pressure injection method, a high pressure of 20 to 40 MPa is applied to cement milk when constructing an agitation pile. In addition, since it is a method of making a pile by pressure by injecting from the tip of the nozzle, there is a disadvantage that a lot of mud is discharged, and the mechanical stirring method by a large machine is a very large machine, so the construction site is restricted, etc. was there.
[0004]
The ultra-high pressure jet agitation method allows construction with a relatively compact machine, but a large amount of mud (discharged slime) is generated, which is undesirable from the environment, and it is expensive to treat this mud. There is a problem that it takes.
[0005]
On the other hand, in the mechanical agitation method using a large machine, the construction machine is large and the place where it can be constructed is limited, and a large plant must be transported and installed for construction. There is a problem that the cost is high.
[Problems to be solved by the invention]
[0006]
The ultra-high pressure jet agitation method is effective for strengthening soft ground, but it has already been mentioned that the generated waste mud causes environmental problems and cost problems for treatment. Furthermore, it is difficult for the conventional construction method to obtain a homogeneous underground pile in humus soil, hard clay, sticky viscous soil, a layer containing an organic substance, a shell layer, and the like. As a promising technology to solve environmental problems, Japanese Laid-Open Patent Publication No. 2001-159130 discloses “Mechanical Stirring Air Cement Milk Mixing Pressure Feeding Method and Device”, and air is pumped by a compressor and blown from the tip of a cutting bit. The technology of digging the ground with a cutting bit while pumping the cement milk with a grout pump after completion of the drilling and stirring the soil and cement milk excavated with the cutting bit is described. . Further, an improvement of the above-described technique is disclosed in Japanese Patent Application Laid-Open No. 2002-97629 as “Mechanical stirring air cement milk mixing pressure feeding method and apparatus”, which is effective for a drilling tool having spiral blades. Describes that stirring is performed. According to these technologies, the cut soil and cement milk are completely agitated to form underground piles, so that waste mud is not discharged to the ground, causing environmental problems, and inexpensive and simple. Reinforcement work can be performed. The present invention relates to these inventions, and further develops the invention to provide a underground pit that is homogeneous even in humus soil, hard clay, sticky viscous soil, layers containing organic substances, shell layers, etc. It aims at providing the soil improvement construction method and apparatus which can be formed.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the ground improvement method of the present invention has a rotary blade having a maximum turning radius of 150 mm or more and 1000 mm or less provided in multiple stages around the front conduit, the shaft body, and the shaft body, The soil excavation tool provided with claws on the upper and lower surfaces of the rotating blades was rotated, and the soil was excavated while jetting compressed air or water or a mixture of water and compressed air from the leading conduit, and reached a predetermined depth. Later, the soil excavation tool is reversely rotated at a rotation speed of 30 to 60 revolutions per minute to inject the ground reinforcement from the rotating blades while stirring the soil, and the soil and ground reinforcement are mixed to improve the soil. A ground improvement method for creating a body, and after reaching a predetermined depth, an operation of rotating the soil excavation tool in a reverse direction while maintaining a constant depth, and an operation of pulling up the soil excavation tool by a predetermined interval in a short time repeated alternately Than it is. Here, the rotary blades provided in multiple stages may be those in which a plurality of disks or polygonal plates are provided in parallel along the shaft body, or may be provided in a spiral shape around the shaft body. In the case of a spiral blade, it is possible to have a shape in which the radius is large at the center portion and the radius is small at both ends in the length direction of the shaft body .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing an example of a soil excavation tool used in the present invention. The soil excavation tool 1 of this example has a spiral blade around the shaft. A tip conduit 2 is provided at the tip, and a cutting tip 3 is provided. While cutting the ground with the cutting tip 3, the leading conduit 2 enters the ground. A shaft body 4 is provided following the leading conduit 2, and a spiral blade 5 is provided around the shaft body 4. Thus, in the present invention, the rotary blades provided in multiple stages include helical blades. Although the shaft body 4 is hollow, the portion where the spiral blades 5 are provided is configured such that the central portion is thick and the both end portions are narrow along the axial direction. Here, as shown in FIG. 1, the shape is such that a cone is connected to both sides of the cylinder, and the diameter increases from both ends toward the center. And even if it sees with the whole shape containing the helical blade | wing 5, the diameter becomes large as a whole toward both ends from the center part. The maximum diameter of the spiral blade 5 is preferably 300 mm or more (radius 150 mm or more), particularly 1000 mm or more (radius 500 mm or more) in order to construct a large diameter without generating mud. Is preferred. Moreover, in order to obtain a uniform improved body without enlarging the scale of the facility, the diameter is preferably 2000 mm or less (radius 1000 mm or less). In this example, the maximum diameter of the spiral blade 5 is 1000 mm. In addition, the length of the shaft body 4 is about 800 mm, the center portion has a constant thickness of about 160 mm, and the shaft diameter changes at a constant rate from about 140 mm to about 400 mm in the upper and lower ranges of about 320 mm. The taper angle is about 22 °. The taper angle of the shaft body 4 has a useful function for smoothly sending earth and sand backward when the spiral blade 5 travels in the ground, but in order to fully exhibit such a function, the taper angle is set to about 22 °. Is preferred. The spiral blade 5 has a pitch that makes one turn every time it travels 160 mm in the axial direction, and makes five turns along the length of the shaft body 4. In the range where the shaft body 4 is tapered, the outer diameter of the spiral blade 5 increases at a constant rate toward the center. On the other hand, in the range where the thickness of the shaft body 4 is constant, the outer diameter of the spiral blade 5 is also constant. In this example, the spiral blade 5 makes a full circle with the maximum outer diameter, and when viewed from the bottom view, the outer shape forms a perfect circle, so the shaft will shake when digging. Without going straight.
[0011]
Although the shaft body 4 is hollow, an inner pipe is provided inside, and the inner pipe is connected to the drawing material discharge nozzle 7. The drawing material discharge nozzle 7 is provided outward at a position where the diameter of the shaft body 4 is the largest. In this example, two drawing material discharge nozzles 7 are provided, but three or more drawing material discharge nozzles 7 may be provided. In addition to providing the shaft body 4 completely perpendicularly, it may be tilted to some extent. A gap between the shaft body and the inner tube serves as a passage for compressed air, and compressed air can be ejected from the tip of the front conduit 2.
[0012]
A plurality of rectangular plate-like claws 6 are attached to the upper and lower surfaces of the spiral blade 6. The claw 6 is provided in a direction in contact with the circumference centered on the shaft body 4, that is, so that the thickness direction of the claw 6 is a radial direction. By attaching in this direction, generation of waste mud is less likely to occur. As shown in FIG. 3, one corner of the rectangular shape of the claw 6 is chamfered. In this chamfering, the corners may be cut off with a straight line or rounded. This chamfered corner is directed in accordance with the direction of rotation of the spiral blade 5. In this example, when digging proceeds, it rotates in the right direction in FIG. 1, but the claw 6 provided on the upper surface of the spiral blade 5 is attached with the chamfered corner facing the direction facing the rotation direction. Conversely, when the soil excavation tool 1 is pulled up, it rotates counterclockwise, but the claw 6 provided on the lower surface of the spiral blade 5 is attached with the chamfered corner directed to the side facing this counterclockwise direction. . By directing in this way, when digging, the claw 6 provided on the lower surface of the spiral blade 5 stirs the soil effectively while sharply impregnating the soil, while the claw 6 provided on the upper surface cuts and agitates. The soil is smoothly fed backwards, making it difficult to bite even if stones of the size of a fist are mixed. Conversely, when pulling up, the claws 6 provided on the upper surface of the spiral blade 5 effectively cut and agitate the soil, and the nails 6 provided on the lower surface smoothly feed the soil backward. As the claw 6, in addition to such a rectangular plate shape, various shapes such as a cylindrical shape, a polygonal column shape such as a quadrangular column and a pentagonal column, and a conical shape can be used, and these can be used in combination. Good.
[0013]
Another example of the soil excavation tool used in the present invention is shown in FIG. In the present example, the rotary blade 6 is configured by arranging a plurality of flat blades in parallel along the length direction of the shaft body 4. As the shape of the flat blade, a disk shape is preferable so as not to discharge mud, but a triangular plate shape such as a triangular shape or a quadrangular shape may be substituted. In order to smoothly carry out the digging and pulling up, the maximum turning radius of each plate-like material is large in the vicinity of the center along the length direction of the shaft body 4 as shown in FIG. Are preferably arranged so as to be small. The maximum rotation radius of the rotary blade 6 is preferably 150 mm or more and 1000 mm or less.
[0014]
FIG. 4 shows an example of a construction machine according to the present invention. The work carriage 23 is self-propelled with an endless track 24 and can easily move the entire apparatus at a construction site. A leader 26 is attached to the work carriage 23 via an arm 25 that can move up and down. The leader 26 is a sliding attachment device that attaches the chuck 27 so as to be movable up and down. When the work carriage 23 is moved to the construction site, the angle of the arm 25 is adjusted and the leader 26 is set up vertically. The uppermost intermediate rod is passed through the chuck 27, and the intermediate rod is grasped by the chuck 27. A swivel 9 is connected to the uppermost intermediate rod, and the soil excavation tool 1 is connected to the lowermost intermediate rod. The chuck 27 can rotate the intermediate rod 22 in both forward and reverse directions by hydraulic drive. That is, the intermediate rod 22 functions as a drive shaft that transmits the rotation of the chuck 27 to the soil excavation tool 1 at the tip. A drawing material hose 28 and an air hose 29 are connected to the swivel 9, and each hose is connected to a grout pump and a compressor (not shown) of the plant. The swivel 9, the intermediate rod 22 and the soil excavation tool 1 each have a double-pipe structure, but are connected so that the passages for the air and the drawing material are connected.
[0015]
When digging with the soil excavation tool 1, air is sent by a compressor and ejected from the tip of the soil excavation tool 1, and the spiral blades of the soil excavation tool 1 are rotated so as to advance downward. There are (1) a method of sending air, (2) a method of sending water, and (3) a method of sending air and water. In places where there are roads etc., using air and water will reduce water usage and will not flood the road, but in places where water does not pose a problem, drill only with water. May be. When drilling holes with air and water, a compressor and a water supply pipe are connected to the ejector, and water and air are mixed and then pumped through the air hose 29. After digging to some extent, the intermediate rod 22 is added to dig deeper. In order to feed the cut earth and sand smoothly backward, the rotary blade has a shape that increases in diameter from the tip toward the center and decreases in diameter toward the top. Since the claw 6 is provided in the rotary blade 5, earth and sand are effectively loosened.
[0016]
When digging to the final depth, the soil excavation tool 1 is pulled up while rotating the rotating blades 6 so that the rotation direction of the chuck 27 is reversed. At this time, the drawing material is fed from the drawing material hose 28, and the drawing material is injected into the ground from the drawing material discharge nozzle of the soil excavation tool 1. Here, the rotational speed of the rotary blade 6 is important. If the rotation speed is not sufficient, the earth and sand and the ground reinforcement such as cement milk and water glass are not sufficiently agitated. For humus soil, hard clay, sticky viscous soil, layers containing organic substances, shell layers, etc., FIG. As shown in Fig. 1, cement milk spreads only in the form of dumplings, and it is impossible to create a homogeneous underground pile. In the present invention, the rotating blades are rotated at a speed of 30 to 60 rotations / minute, and it is particularly preferable to rotate at 35 to 40 rotations / minute. By using the rotation speed within this range, a homogeneous and good underground pile can be formed even in soil in which it is difficult to form a homogeneous underground pile by the conventional method. Moreover, construction time can also be shortened by stirring at high speed rotation. Since the nail | claw is provided also in the upper surface of the rotary blade 5, earth and sand and cement milk are stirred effectively. And in the construction machine and construction method according to the present invention, the mechanical stirring of the earth and sand and the stirring of the earth and sand by the ejection of the drawing material is performed at the same time, the cut earth and sand and the drawing material are efficiently mixed, The cut earth and sand are not discharged to the ground as waste mud. Here, as a method of lifting the soil excavation tool while rotating it in reverse, the operation of rotating the soil excavation tool while keeping the soil excavation tool at a constant depth and the operation of pulling up the soil excavation tool within a short time are alternately repeated. It is preferable to prevent the generation of mud more effectively. For example, in this example, reverse rotation and injection of the injection material were performed at the same depth for 4.5 seconds, and the height was raised by 2.5 cm. That is, it is lifted 40 times in steps of 2.5 cm at a depth of 1 m, and rises over 3 minutes. The time required for pulling up is shorter than the time staying at the same depth. When pulling up, the work proceeds while removing the intermediate rods sequentially, contrary to when digging. If it raises to predetermined | prescribed height, injection | pouring of a drawing material will be stopped and the soil excavation tool 1 will be pulled up. When the construction of one hole is completed in this way, the work carriage 23 is moved to the next position and the same construction is repeated.
[0017]
An example of a construction machine drive device used in the present invention is shown in FIG. In the soil improvement method according to the present embodiment, since the rotating radius is 150 to 1000 mm and a large rotating blade is included and the earth and sand are stirred by rotating at a high speed of 30 to 60 revolutions per minute, the driving device to be used is also powerful. It needs to be something. On the other hand, this drive device must be compact enough to be mounted on the work carriage 23. Therefore, as shown in FIG. 7, the oil motor 31 is used as a driving source, a planetary speed reducer 32 having a reduction ratio of about 1/6 is connected to the shaft of the oil motor 31, and the first side is connected to the output side of the planetary speed reducer 32. The pulley 33 is provided. The second pulley is connected to the first pulley 33 through the intermediate transmission device 34 such as an intermediate pulley or a belt so that the reduction ratio becomes 1/6. The output shaft 36 connected to the second pulley rotates the intermediate rod through the chuck 27 and the like to rotate the soil excavation tool 1. By adopting such a configuration, a sufficient output can be obtained, and a compact drive device that can rotate at a higher speed than a drive device mounted on a conventional civil engineering work cart is obtained.
[0018]
Next, another embodiment of the present invention will be described. In this embodiment, powder cement is directly fed into the ground instead of cement milk as an injection material. FIG. 7 shows an example of a swivel used in this embodiment. The upper part of the swivel 9 is a non-rotating part 10 and does not rotate. The non-rotating portion 10 is provided with a drawing material inlet 11 and an air inlet 12 on the side surfaces. A rotating shaft 14 is attached via a bearing 13 so as to be rotatable with respect to the non-rotating portion 10. The rotating shaft 14 has a double tube structure including an inner tube 15 and an outer tube 16. The inner tube 15 is hollow, and this hollow portion constitutes the drawing material passage 17. The drawing material passage 17 is connected so that the drawing material introduced from the drawing material introduction port 11 can pass through. A gap is also provided between the inner pipe 15 and the outer pipe 16, and this gap constitutes an air passage 18. The air passage 18 is connected so that the air introduced from the air inlet 12 can pass through. This structure is almost the same as that used in the above-described embodiment of injecting cement milk, but in this embodiment, a thick inner tube is used to send powdered cement through the inner tube 15. FIG. 8 shows an example of the intermediate rod used in this embodiment. The intermediate rod also has a double tube structure, but a thick tube of about 3 inches is used for the inner tube, similar to the swivel.
[0019]
FIG. 9 shows an example of a construction machine used in this embodiment. The swivel and the intermediate rod have the aforementioned thick inner tube. An injection material hose 28 is connected to the upper part of the swivel, and the injection material hose 28 is connected to an ejector 41. A hopper 43 is provided above the ejector 41 to supply powder cement 44 to the ejector. The other end side of the ejector is connected to the compressor 42 and supplied with compressed air. The powdered cement is taken into the ejector 41 by the compressed air, and the powdered cement is fed by the compressed air through the injecting material hose 28, the swivel and the intermediate rod to the injecting material discharge nozzle 7 in the rotary blade portion of the soil excavation tool. It is supposed to be sent.
[0020]
In the ground improvement method using a construction machine, the work is carried out in substantially the same manner as in the above-described embodiment, but powder cement is injected into the ground from the injection material discharge nozzle 7 while rotating the soil excavating tool 1 in the reverse direction. To do. The cement injected into the ground is stirred together with the earth and sand by the rotary blade 5 provided with the claws 6 to form underground piles. The strength of underground piles is high because powder cement is injected instead of cement milk. On the other hand, in the method of injecting cement milk, the strength of the underground pile is slightly lowered, but there is an advantage that the underground pile having a diameter larger than the rotation radius of the rotary blade can be created, which is excellent in economic efficiency.
[0021]
【Example】
It is an example in which the present invention is applied to ground improvement work. Here, high concentration cement milk is used as the drawing material. The cement milk used in this construction method should have a higher cement ratio than the conventional construction method (for example, about 760 kg of cement in 1 m ³ of the drawn material). Is preferred. Here, if the amount of cement is increased, the specific gravity of the drawn material increases and the pumpability of the pump tends to deteriorate, so a water reducing agent (for example, an aromatic sulfone and specially modified lignin as a main component) may be blended. preferable. The blending of the water reducing agent facilitates the flow of cement milk and facilitates feeding by the pump, and increases the strength of the improved body. In this example, the product name Sunflow SW-2000S (Nippon Paper Industries Co., Ltd.) containing aromatic sulfone and specially modified lignin as main components is used as a water reducing agent, and 1000 kg of cement is used in 1 m ³ of the drawn material. 5 kg of Sunflow SW-2000S was blended to obtain an improved compression strength of 1 MPa (design standard strength). There are a method of jetting cement milk mixed with air at a low pressure of 0.6 to 2.5 MPa and a method of jetting cement milk at an ultrahigh pressure of 18.0 to 29.0 MPa. In the case of the latter ultra-high pressure jet agitation, air and cement milk are sent separately without mixing, and air is drawn downward from the tip of the leading conduit when digging, and cement milk is drawn next to the spiral blade when pulling up. It ejects from the material discharge port 7 in the lateral direction. In both methods, the cut earth and sand are mixed with cement milk and constitute an underground pile as an improved body, so that they are not discharged as waste mud on the ground. When pulling up, the spiral blades rotate clockwise in FIG. 3, drawing the earth and sand from above and pressing the agitated and mixed earth and cement downward with the blades, so that a strong underground pile can be formed, Strongly suppresses the generation of mud. For this reason, it does not cause environmental problems due to waste mud, and it does not incur a large amount of cost for the treatment of waste mud. Therefore, it is an environment-friendly construction method with excellent workability, economy and safety. ing.
[0022]
In the case of ultra-high pressure jet agitation, cement milk is injected in a horizontal direction at a high pressure, so that it is possible to create an improved body in a wider range than the diameter of the spiral blade, which shortens the construction period and improves the economy. In addition to being able to be realized, close construction and mutual construction are possible, and the overall construction can be integrated. In this example, a spiral blade having a diameter of 1 m was used, and stirring was performed at a high speed of 35 to 40 rotations per minute. The drawing material discharge pressure was 18 to 22 MPa, the air discharge amount was 1.5 to 3.0 m ³ / min, and the air discharge pressure was 0.6 to 0.7 MPa. It is necessary to pay attention to the injection amount per unit time, and if the excessive injection is performed, the effect of the present invention that no mud is generated may not be exhibited. In order to make sure prevention of waste mud, it is preferable to inject at about 70% after grasping in advance the injection amount per unit time at the limit where no waste mud is generated. In this example, it was 70 liters / min. The pulling speed (expressed in terms of time required for pulling up 1 m below) is 3.0 min / m, 0.01 N / mm ² ≦ C ≦ 0 for clay soil with C <0.01 N / mm ² (= MPa). It was set to 5.0 min / m for the soil of 03 N / mm ² (5 ≦ N ≦ 10), and 6.0 min / m for the sand of 10 ≦ N ≦ 15.
[0023]
On the other hand, in the case of low pressure ejection, the inside diameter of the drawing material injection nozzle 7 is 8 to 12 mm, the rotational speed of the spiral blade is 30 rotations per minute, the drawing material discharge pressure is 0.6 to 2.5 MPa, and the injection speed. Was 50 liters / min.
[0024]
By the construction method of the present embodiment, a homogeneous improved body can be created even in soil that is difficult to construct by conventional construction methods such as humus soil. Moreover, even in the soil that has been the subject of conventional construction methods, it is possible to easily create a more homogeneous improved body without discharging mud.
[0025]
【The invention's effect】
In the present invention, there is an effect that a homogeneous underground pit can be formed even in humus soil, hard clay, sticky viscous soil, a layer containing an organic substance, a shell layer, and the like, and without draining mud. Sediment can be excavated and agitated, and the environment around the construction site can be protected.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a soil excavation tool used in the present invention.
FIG. 2 is a cross-sectional view showing another example of a soil excavation tool used in the present invention.
FIG. 3 is a perspective view showing a shape of a nail.
FIG. 4 is a front view showing a construction machine according to the present invention.
FIG. 5 is a cross-sectional view showing an underground pile by a conventional construction method.
FIG. 6 is a front view showing a drive device used in the construction machine according to the present invention.
FIG. 7 is a cross-sectional view showing a swivel.
FIG. 8 is a cross-sectional view showing an intermediate rod.
FIG. 9 is a front view showing a construction machine according to the present invention.
[Explanation of symbols]
1. Soil excavation tool2. Tip conduit3. Cutting tip 4. 4. Shaft body 5. Spiral blade Nails 7. 7. Drawing material discharge nozzle Air outlet 9 Sibel 10 Non-rotating part 11. Drawing material inlet 12. Air inlet 13. Bearing 14. Rotating shaft 15. Inner tube 16. Outer tube 17. Drawing material passage 18. Air passage 19. Male coupling 20. Female coupling 21. Bolt 22. Intermediate rod 23. Work carriage 24. Endless track 25. Arm 26. Leader 27. Chuck 28. Drawing material hose 29. Air hose 31. Oil motor 32. Planetary speed reducer 33. First pulley 34. Intermediate transmission device 35. Second pulley 41. Ejector 42. Compressor 43. Hopper 44. Powder cement

Claims (3)

Rotating a soil excavation tool having rotating blades having a maximum turning radius of 150 mm to 1000 mm provided in multiple stages around the front conduit, the shaft body, and the shaft body, and having claws on the upper and lower surfaces of the rotating blade And excavating the soil while jetting compressed air or water or a mixture of water and compressed air from the leading conduit, and after reaching a predetermined depth, the soil excavation tool is rotated at a rotational speed of 30 to 60 revolutions per minute reverse rotation is allowed by injecting ground reinforcement from rotating vane portions while stirring the soil by mixing the soil and ground reinforcing material, a ground improvement method to construct a improved body soil, reaches a predetermined depth After that, the ground improvement method that alternately repeats the work of rotating the soil excavation tool in a reverse direction while keeping the soil excavation tool at a constant depth and the work of lifting the soil excavation tool by a predetermined interval in a short time. The ground improvement method according to claim 1, wherein a spiral blade having a shape in which a radius is large at a central portion and a radius is small at both ends in the length direction of the shaft body is used as the rotating blade. The ground improvement construction method according to claim 1 or 2 , wherein an injection speed of the ground reinforcement is about 70 liters per minute, and the soil excavation tool is pulled up at a speed of 3 to 6 minutes per meter.

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