JP4359931B2 - Pile burying method by medium digging method - Google Patents

Description

  The present invention is a medium digging method in which a cylindrical precast concrete pile (hereinafter referred to as a PC pile) is inserted into the ground while discharging the earth and sand in the lower end by a spiral auger accommodated in the pile. The present invention relates to a pile burying method by an intermediate digging method in which the lower end of a slab is supported by an enlarged bulb having a diameter larger than its outer diameter.

  Conventionally, the digging method has been widely adopted as one of underground methods for PC piles. In this medium digging method, a spiral auger equipped with a drilling head at the tip is inserted into a hollow PC pile, and the drilling head projects below the lower end of the pile to excavate the ground under the pile hollow part. It is a method of press-fitting into the PC, and is press-fitted with the outer peripheral surface of the PC pile in close contact with the ground.

  Moreover, in the above digging method, as a method of supporting the lower end of the PC pile on the underground stable ground (support base), there is a method of creating an enlarged bulb below the lower end after inserting the PC pile to the support base. .

  In this method of creating an enlarged sphere, the excavation head is provided with an enlargement excavation blade that protrudes in the radial direction, and the excavation head is swung together with the spiral auger with the enlargement excavation blade protruding so that it is below the lower end of the pile. There is a method of forming an enlarged bulb forming portion and then injecting cement milk into the enlarged bulb forming portion from a nozzle at the tip of the excavation head to form an enlarged bulb made of concrete. This method uses an excavation head having a structure in which an enlarged excavation blade rises due to resistance with the ground by rotating the spiral auger backward and projects in the radial direction (for example, Patent Document 1), hydraulic pressure (For example, patent document 2) which uses the excavation head of the structure which makes an expansion excavation blade stand up and protrudes in radial direction.

Also, without using an enlarged digging blade, a liquid injection nozzle is provided at the shaft part of the spiral auger, and after forming an enlarged bulb forming part by injecting water at a high pressure from this nozzle, cement milk is injected. There is a method (for example, Patent Document 3) for creating an enlarged bulb.
JP 2004-285563 A JP 2005-23664 A JP 2000-965672 A

  The conventional method of creating an enlarged bulb uses a PC pile in both the method of expanding the diameter by expanding the enlarged excavating blade and the method of expanding the diameter by injecting high-pressure water under the lower end of the pile. In the middle digging method, the PC pile must have a certain thickness or more, and it must be a spiral auger and excavation head with a diameter that can be inserted into the hollow part of the center, compared with the diameter drilled by the auger. The diameter of the enlarged bulb needs to be larger than the thickness of the PC pile.

  For this reason, when using an enlarged drilling blade, in order to increase the diameter of the enlarged bulb, it is necessary to increase the protruding length in the radial direction of the enlarged drilling blade. There is a limit to the enlargement ratio in terms of strength and space.

  On the other hand, in the case of the method of forcibly standing using hydraulic pressure, the protruding length of the enlarged excavating blade can be adjusted, so the enlarged excavation rate is reduced once, and the enlarged diameter is increased gradually in several steps. However, it is necessary to equip the excavation head that is inserted into the ground with a hydraulic device, and the hydraulic flow to the rotating support shaft that reaches the ground. Since it is necessary to install a road, there is a problem that the apparatus has to be expensive, and if a failure occurs in the excavation head during the expanded excavation, this has to be destroyed.

  Furthermore, even in the diameter expansion excavation by jetting high pressure water, the tip of the nozzle was inside the outer diameter of the spiral auger, and therefore there was a problem that the ratio of the diameter of the expansion bulb to the pile diameter could not be increased.

  Further, in these conventional methods, an enlarged bulb forming part is formed by excavating an enlarged excavating blade or a combination of this and water pressure or only by water pressure, and cement milk is injected therein to form an enlarged bulb. However, when excavating the enlarged bulb formation part, it is not possible to completely prevent the surrounding natural ground from loosening, and cement milk is injected into the space formed in the loose natural ground to form an enlarged bulb. As a result, there was a loose ground around the enlarged bulb, and the bearing capacity of the pile had to be reduced accordingly.

  In view of such a conventional problem, the present invention can increase the diameter of the enlarged bulb below the lower end of the pile in the middle digging method using the PC pile, and the formed bulb can be surrounded by It was made for the purpose of providing a pile burying method by an intermediate digging method that is constructed in close contact with a stable part of a natural ground.

In order to solve the above-described conventional problems and achieve the intended purpose, the invention according to claim 1 is characterized in that a cylindrical PC pile is fixed to a hollow inside thereof and an excavation head is fixed to the tip. A spiral auger is inserted and inserted into the ground, and then the excavation head is advanced to form an enlarged bulb forming portion having an outer diameter larger than the outer diameter of the PC pile under the lower end of the PC pile, In the pile burying method by the medium digging method of filling the solidifying material in the enlarged bulb forming portion and inserting the lower end of the PC pile into the enlarged bulb forming portion,
The excavation head is housed inside the outer diameter of the spiral auger by rotating it forward, and an enlarged excavation blade that protrudes outward from the outer diameter of the spiral auger by rotating it reversely. Use a tip provided with a nozzle that injects liquid outside the outer diameter of the spiral auger,
Excavating the PC pile up to the bottom of the enlarged bulb forming position while rotating the excavating head in a state where the PC pile is inserted to the front of the enlarged bulb forming position,
After that, by rotating the excavation head in the reverse direction so that the enlarged excavating blade protrudes in the auger radial direction and the drilling water is ejected from the nozzle while being injected at a high pressure, the enlargement of the radius larger than the rotating radius of the enlarged excavating blade is performed. Create a bulb-forming part,
After the formation of the enlarged bulb forming part, the excavating head is lowered to the bottom of the enlarged bulb forming part, and the excavating head is rotated in the reverse direction so that the enlarged excavating blade protrudes in the radial direction and is raised while jetting cement milk from the nozzle. By doing so, cement milk is filled into the enlarged bulb forming portion, and the lower end of the PC pile is inserted into the enlarged bulb before the cement milk is solidified.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, after the formation of the enlarged bulb forming portion, the excavation head is lowered to the bottom of the enlarged bulb forming portion, and the excavation head is rotated in the reverse direction. When filling the enlarged bulb forming portion with the cemented milk by projecting the enlarged excavating blade in the radial direction and raising the cement milk while jetting cement milk from the nozzle, the enlarged bulb forming portion previously formed by jetting the cement milk The surrounding ground and cement milk are mixed to create an enlarged bulb having a larger diameter than the enlarged bulb forming portion.

  The feature of the invention described in claim 3 is that, in addition to the configuration of claim 1 or 2, the formation of the enlarged bulb forming portion is made downward by changing the cement milk injection pressure from the nozzle of the excavation head. The small diameter portion is formed on the upper side of the large diameter portion, and the PC pile is inserted into the large diameter portion before the cement milk is solidified.

  The invention according to claim 4 is characterized in that, in addition to the configuration of claim 1 or 3, when the PC pile is inserted into the enlarged bulb forming portion, the nozzle of the excavation head is connected to the lower end portion and the inner surface of the PC pile. By injecting cement milk toward it, it is to insert while cleaning the PC pile.

  According to a fifth aspect of the present invention, in addition to the configuration of the first to third or fourth aspects, the excavation head is excavated to the bottom of the enlarged bulb forming position while rotating forward, and thereafter, When the excavation head is rotated in the reverse direction to cause the enlarged excavation blade to protrude in the auger radial direction, water is ejected from the nozzle to reduce excavation resistance due to the enlargement excavation blade.

  In the present invention, as described in claim 1, the pile burying by a hollow digging method in which a cylindrical PC pile is inserted into the hollow by inserting a spiral auger having a drilling head fixed at the tip thereof into the ground. In the method, as an excavation head, the enlarged excavation blade is housed inside the outer diameter of the spiral auger by rotating the excavation head in the forward direction, and protrudes outward from the outer diameter of the spiral auger by rotating the excavation head. By using the tip of the blade provided with a nozzle for injecting liquid outside the outer diameter of the spiral auger, the radius is further increased by the injection of the high-pressure water from the nozzle and larger than the digging radius by the enlarged digging blade It becomes easy to excavate and form the bulb forming part, and the diameter of the enlarged bulb with respect to the PC pile diameter can be made much larger than the conventional method. That.

  Further, after forming the enlarged bulb forming portion, the excavating head is lowered to the bottom of the enlarged bulb forming portion, and the excavating head is rotated in the reverse direction so that the enlarged excavating blade protrudes in the radial direction and cement milk is sprayed from the nozzle. As it is raised, cement milk is jetted onto the inner surface of the enlarged bulb forming part excavated and formed by the previous injection of high-pressure water, so that the outer diameter of the enlarged bulb forming part is further increased and reaches the outer peripheral surface of the enlarged bulb. Until then, a high-quality cement milk solidified product is formed, and a high-quality expanded bulb is formed. At the same time, the peripheral surface frictional force of the enlarged bulb is increased, and an enlarged bulb having a large ultimate support force is formed.

  According to the second aspect of the present invention, the digging head is rotated in the reverse direction so that the enlarged digging blade protrudes in the radial direction and is raised while jetting cement milk from the nozzle at the tip of the digging blade. By filling the peripheral ground of the enlarged bulb forming part formed previously by injection of the cement milk and cement milk to form an enlarged bulb having a larger diameter than the enlarged bulb forming part, Cement milk is mixed with the surrounding ground soil and sand that was loosened at the time of excavation molding of the previous enlarged bulb formation part, and this will be solidified, and an enlarged bulb closely adhered to the stable support ground will be created. Can do.

  The present invention, as described in claim 3, when forming the enlarged bulb forming portion, by changing the cement milk injection pressure from the nozzle of the excavation head, to form a large diameter portion on the lower side and a small diameter portion on the upper side, Before solidifying the cement milk, the PC pile is inserted into the large-diameter portion until it opposes the vertical load by the large lower end surface of the large-diameter portion, and by the frictional force with the ground on the outer peripheral surface of the small-diameter portion. Will also counter the vertical load, and can exert even greater ultimate support.

  Further, according to the present invention, when the PC pile is inserted into the enlarged bulb forming portion, the cement milk is sprayed from the nozzle of the excavation head toward the lower end portion and the inner surface of the PC pile as described in claim 4. By inserting while washing the pile, it is inserted into the cement milk without mud adhering to the lower end surface and the lower end inner surface of the PC pile, so that the connection between the enlarged bulb and the PC pile becomes strong. .

  Further, the excavation head is rotated in the forward direction until the bottom of the enlarged bulb forming position is excavated, and then, when the excavation head is rotated in the reverse direction and the enlarged excavation blade is protruded in the auger radial direction, By spraying water from the nozzle to reduce the digging resistance due to the enlarged digging blade, the resistance when raising the digging blade by reversing the digging head is reduced, and the erection of the enlarged digging blade and thereafter Enlarged excavation is made without difficulty.

  Next, embodiments of the present invention will be described based on examples shown in the drawings. 1 to 6 show an example of a drilling head for use in the present invention. In this excavation head A, a joint portion 2 is integrally provided at the upper end of the central shaft 1, and a lower spiral auger 3 and an upper spiral auger 4 are provided on the outer periphery in a vertically divided manner. The lower spiral auger 3 is installed in a shape in which a pair of ribbon-shaped screw blades 3a, 3a are wound spirally with their edges fixed to the outer periphery of the lower end of the central shaft. The screw blade 3a has a helical pitch as small as about 1/2.

  The upper spiral auger 4 is spirally wound with ribbon-shaped screw blades 4a, 4a fixed to the outer periphery of the central axis, and spirals over a substantially upper half length of the central axis 1. A vertical one having a pitch as large as about 1/4 is installed.

  Between the upper and lower spiral augers 3 and 4, a pair of enlarged excavating blades 10 and 10 are installed. As shown in FIGS. 1 to 3, the enlarged excavating blade 10 is overturned by the resistance of the surrounding earth and sand when the upper and lower spiral augers 3 and 4 are rotated in the forward direction, that is, in the direction of moving forward in the ground. Thus, when the spiral augers 3 and 4 are rotated in the reverse direction, that is, in the reverse direction, they are raised by the resistance of the surrounding earth and sand, and the screw blades 3a and 4a It protrudes outside the turning radius.

  The enlarged excavation blade 10 includes an arm portion 11 that rotates about a support shaft, and an excavation bit 12 that protrudes from one end of the arm portion 11 toward one side. A pair of parallel bearing pieces 13, 13 project from the base end portion of the arm portion 11, and a support member 14 fixed to the outer periphery of the central shaft 1 is inserted between the bearing pieces 13, 13 to support them. The shaft 15 is penetrated, and the arm portion 11 is pivoted so as to rotate about the support shaft 15.

  A stopper plate 16 for restricting the stop angle position at the rising side of the rotating arm 11, that is, the protruding side position of the enlarged excavation blade 10, is fixed to one side edge of the support member 14. It is regulated so that it does not rotate beyond the maximum projection angle by the back surface coming into contact.

  The excavation bit 12 is provided at the distal end of the arm portion 11 and protrudes to the front side in the rotation direction when the excavation head A rotates in reverse, that is, when the expansion excavation blade 10 rises and expands the surroundings. A nozzle 20 for injecting water or cement milk to the distal end of the arm portion on the rear side as needed is provided in the extending direction of the distal end side of the arm portion 11.

  In FIG. 2, reference numeral 17 denotes the outer diameter of the upper and lower spiral augers 3, 4, 18 denotes the turning outer diameter when the expanded excavation blade 10 is projected, and 19 denotes the outer diameter of the PC pile to be embedded. .

  As shown in FIG. 3, a liquid supply passage 21a communicating with the nozzle 20 is formed in the arm portion 11 and the one bearing piece 13, and the support shaft 15 has a feed opening with one end opened at the end of the support shaft. A liquid passage 21b is formed, and both the liquid supply passages 21a and 21b communicate with each other via a universal joint 21c that maintains the communication state between the two liquid supply passages even when the bearing piece 13 and the support shaft 15 rotate relative to each other. Has been. The liquid supply pipe 23 is communicated with the opening of the liquid supply path 21 b communicated with the nozzle 20 through the pipe joint 22.

  On the other hand, the central shaft 1 is formed in a hollow cylindrical shape as shown in FIG. 4, and an inner cylinder 24 is inserted into the hollow portion. Separate liquid supply paths 25 and 26 are formed in the inner cylinder 24 and between the inner cylinder and the inner surface of the hollow portion of the central shaft. A liquid supply path 26 between the inner cylinder 24 and the inner surface of the central shaft is communicated with a liquid supply pipe 23 communicating with the nozzle 20 through a pipe joint 27. Further, the liquid supply path 25 in the inner cylinder 24 communicates with nozzles 28 and 29 opened at the lower end of the central shaft 1.

  In the figure, reference numeral 3b denotes a downward excavation bit protruding from the lower end of the excavation head A.

  Next, the Example of the pile burial method by the medium digging method based on this invention which uses the excavation head A mentioned above is described.

  FIG. 7 shows an outline of a pile driving device used for the construction of this construction method. In the figure, reference numeral 30 denotes a device main body which can be moved by a traveling means consisting of a crawler, and a column 31 is erected at the end thereof. ing. A slide guide 32 is fixed to the column 31 in the axial direction, and a rotation driving means 33 and a pile insertion means 34 are supported on the support 31 so as to be movable in the vertical direction. These means are not shown in detail in the drawing, but are provided with slide drive means for moving them in the vertical direction.

  The rotation drive means 33 has a rotation drive source 33a composed of an oil motor or an electric motor, and the spiral auger B for earthing is detachably connected to the drive shaft 35 rotated by the drive source 33a. ing. The drive shaft 35 can change the rotation in the forward and reverse directions by switching the rotation direction by a rotation drive source. This rotation switching may be performed by a gear mechanism for rotation switching.

  The spiral auger B has a structure in which a ribbon-shaped screw blade 36 is wound around the outer periphery of the central shaft 1 in a spiral manner with its edge fixed, and the central shaft 1 has the same structure as the excavation head A described above. It has a double cylinder structure in which an inner cylinder (not shown) is inserted, and a liquid supply path that leads to the liquid supply paths 25 and 26 formed in the central shaft 1 of the excavation head A is formed separately. By connecting the lower end of the shaft to the joint portion 2 at the upper end of the excavation head A, the liquid supply path is communicated.

  The pile insertion means 34 is provided with a pile suspension device 37 that fixes and hangs the upper end of the PC pile C at the lower end. This pile suspending device 37 suspends the PC pile C in a rotatable state.

  In this way, the PC pile C is moved in the settling direction by being moved downward by the slide driving means while the PC pile C is suspended.

  The pile driving device configured as described above is carried into the construction site, the column 31 is brought upright at a predetermined PC pile pile embedding position, and the spiral auger B and the excavation head A are connected to each other with the PC pile C inside. Insert with. Thereafter, the PC pile C and the spiral auger B are lifted by a winch, and the upper ends are fixed to the pile insertion means 34 and the rotation driving means 33, respectively, and are suspended.

  In addition, the excavation head A has such a size that the outer diameters of the upper and lower spiral augers 3 and 4 can be easily inserted into the PC pile C, and the earth and sand do not easily pass between the inner periphery of the PC pile C. In addition, the extended excavation blade 10 having a length selected so as to protrude outwardly by 60 mm or more from the outer diameter of the PC pile C is used when the expanded excavation blade 10 is in the above-described state of standing upright in the radial direction. .

  In this state, the excavation head A is pushed forward into the ground while the excavation head A is rotated forward by the rotation driving means 33, the ground is excavated ahead of the lower end of the PC pile C, and the PC pile C is discharged while being discharged by the spiral auger B. Press to insert into the ground.

  Next, the work process of the pile burying of this invention is demonstrated about FIG.

  As shown in FIG. 8A, the excavation head A and the spiral auger B are inserted into the PC pile C, and the excavation head A is inserted into the ground with the tip of the excavation head A preceding the PC pile C. . When the ground is hard, the excavation head A is rotated forward and inserted while discharging, but when the ground is soft, the excavation head A is reversed, the enlarged excavation blade 10 is projected, and the soil is pushed out to the surroundings. Insert without discharging. In this way, the PC pile C is inserted until the lower end thereof reaches the upper end position D5 of the planned enlarged bulb to be created. Further, if necessary, water is jetted from the nozzles 28 and 29 to assist excavation.

  In the figure, D0 is the lowest part of the planned enlarged bulb, D1 is a position that is higher than the lowest part of the planned enlarged bulb by the diameter of the PC pile C, D2 is also a position that is twice as high as the diameter of the PC pile C, and so on. In addition, D3, D4, and D5 indicate positions that are higher by the number multiplied by the diameter of the PC pile C.

  Next, as shown in FIG. 8 (b), the insertion of the PC pile C is stopped, and the excavation head A is rotated forward to excavate until the enlarged excavation blade 10 reaches D1, while excavating. Stop moving forward, rotate forward, and dump enough. At this time, water for assisting excavation is sprayed from the nozzles 28 and 29 as necessary.

  Then, as shown in FIG.8 (c), it rotates reversely and the expansion excavation blade 10 is opened. At this time, water is jetted from the nozzle 20 and the nozzles 28 and 29 at a high pressure in order to reduce drilling resistance during reverse rotation. After confirming that the enlarged excavating blade 10 has been raised, the excavation head A is pulled up until the position of the enlarged excavating blade 10 reaches D5 while performing reverse excavation. At this time, since the earth and sand excavated by the expansion digging are excavated from the pre-digging earth and sand, they are mixed with the sprayed water and accumulated in the enlarged bulb forming part E which has been expanded and dug.

  Next, as shown in FIG. 8 (d), the excavation head A is rotated forward or backward until it is lowered until the enlarged excavation blade 10 reaches D 0, and the forward rotation is continued at that position so that the earth and sand in the enlarged bulb forming part E Excavate.

  When sufficient earth removal is completed, as shown in FIG. 8E, the excavation head A is reversely rotated to raise the enlarged excavation blade 10, and cement milk F is injected from the nozzle 20 and the nozzles 28 and 29 at a high pressure to enlarge. While pressing against the inner surface of the bulb forming portion E and expanding the diameter, the position of the enlarged excavating blade 10 was raised to D3 as shown in FIG. 8 (f), and was loosened by the enlarged excavation in FIG. 8 (c). Cement milk is mixed into the surrounding earth and soil. As a result, the surrounding ground loosened by the previous excavation is solidified, and a stable supporting ground on the outside and an enlarged bulb closely adhered to the dense state are formed.

When reaching D3, as shown in FIG. 8 (g), the jetting pressure of the cement milk F ejected from the nozzle 20 is reduced, the degree of diameter expansion is reduced, and similarly, it is raised to the position of D5. As a result, the cement milk F is filled into an enlarged bulb shape having a two-stage diameter composed of the lower large-diameter portion d1 and the upper narrow-diameter portion d2.
After the cement milk F is injected and injected in this way, as shown in FIG. 8 (h), the PC pile C is lowered until its lower end reaches D2, and the pile is inserted into the aforementioned large diameter portion d1 from its upper end. Insert as much as the diameter. At this time, the cement milk F is sprayed from the nozzle 20, and the pile tip is lowered while being washed with the cement milk.

  Thus, after inserting the PC pile C into the large diameter part d1, the descent | fall is stopped, and as shown in FIG.8 (i), more than predetermined length in the hollow part of the PC pile C continuously. To the height, the root hardening liquid is injected from the nozzle 20 and injected, and after the injection of a predetermined amount is completed, the excavation head A is pulled out while pouring water into the pile hollow portion in order to suppress the pressure, and the construction is completed.

  It should be noted that the enlarged digging diameter and the enlarged bulb diameter can be obtained by changing the jet pressure of jet water at the time of enlarged digging in FIG. 8 (c) and the jet pressure at the time of cement milk injection at the large diameter portion in FIG. 8 (e) and (f). For example, the jet water jet pressure during expansion digging is set to 5 to 10 Mp (megapascals), and the jet pressure at the time of cement milk injection in FIGS. 8 (e) and 8 (f) is set to 15 to 25 MPa. It is said. The diameters of the enlarged bulb forming part formed by excavation and the enlarged bulb formed by solidifying cement milk are made different depending on the difference in the jet pressure and the specific gravity between the jetted water and the cement milk.

  The enlarged bulb G formed in this manner is provided with the enlarged excavating blade 10 on the excavating head A, and the nozzle capable of injecting high-pressure drilling water and cement milk toward the distal end portion of the enlarged excavating blade 10 is directed in the radial direction. Because it is provided, the reach radius of drilling water and cement milk can be made larger than before, and as shown in FIGS. 8 (c) to 8 (e), the diameter of the enlarged bulb forming portion is expanded by digging up to D0 and turning it in reverse. However, after that, cement milk was sprayed onto the inner surface of the enlarged diameter forming portion to further expand the diameter, thereby expanding the diameter of the expanded bulb to a pile diameter that was not possible with conventional PC piles by 1. It becomes possible to make it 7 or more.

  Further, as shown in FIG. 9, the enlarged bulb to be formed has a cement milk mixed soil solidified portion 41 closely adhered to a stable support ground 40 at the outermost peripheral portion, and the soil mixing ratio increases toward the center. An enlarged bulb in which a small amount of cement milk solidification part 42 is integrated is created.

It is a front view which shows an example of the excavation head used for the pile burying method which concerns on this invention. It is the sectional view on the aa line of the enlarged excavation blade part in FIG. FIG. It is the bb sectional view taken on the line in FIG. It is the longitudinal cross-sectional view which showed only the central-axis part which abbreviate | omitted the screw blade | wing etc. of the excavation head shown in FIG. It is a bottom view same as the above. It is a side view of the excavation head lower end part same as the above. It is a side view which shows the outline of the whole apparatus used for the pile burying method which concerns on this invention. (A)-(h) It is schematic-drawing sectional drawing for demonstrating the construction process in this invention method. It is a longitudinal cross-sectional view of the enlarged bulb created by the method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Center shaft 2 Joint part 3 Lower spiral auger 4 Upper spiral auger 3a Screw blade 4a Screw blade 10 Expansion excavation blade 11 Arm part 12 Excavation bit 13 Bearing piece 14 Support member 15 Support shaft 16 Stopper plate 20 Nozzle 21a Supply path 21b Liquid supply path 21c Universal joint 22 Pipe joint 23 Liquid supply pipe 24 Inner cylinders 25 and 26 Liquid supply path 27 Pipe joints 28 and 29 Nozzle 30 Device body 31 Column 32 Slide guide 33 Rotation drive means 34 Pile insertion means 33a Rotation drive source 35 Drive shaft 36 Screw blade 37 Pile suspending device 40 Support ground 41 Cement milk mixed soil solidification part 42 Cement milk solidification part A Drilling head B Spiral auger C PC pile E Expansion bulb formation part F Cement milk G Expansion bulb d1 Large diameter part d2 Small diameter Part

Claims (5)

A cylindrical precast concrete pile (hereinafter referred to as a PC pile) is inserted into the hollow interior by inserting a spiral auger with a drilling head fixed at the tip, and then the drilling head is advanced. An enlarged bulb forming portion having an outer diameter larger than the outer diameter of the PC pile is formed under the lower end of the PC pile, and a solidifying material is filled in the enlarged bulb forming portion and the lower end of the PC pile is placed in the enlarged bulb forming portion. In the pile burying method by the medium digging method to insert
The excavation head is housed inside the outer diameter of the spiral auger by rotating it forward, and an enlarged excavation blade that protrudes outward from the outer diameter of the spiral auger by rotating it reversely. Use a tip provided with a nozzle that injects liquid outside the outer diameter of the spiral auger,
Excavating the PC pile up to the bottom of the enlarged bulb forming position while rotating the excavating head in a state where the PC pile is inserted to the front of the enlarged bulb forming position,
After that, by rotating the excavation head in the reverse direction so that the enlarged excavating blade protrudes in the auger radial direction and the drilling water is ejected from the nozzle while being injected at a high pressure, the enlargement of the radius larger than the rotating radius of the enlarged excavating blade is performed. Create a bulb-forming part,
After the formation of the enlarged bulb forming part, the excavating head is lowered to the bottom of the enlarged bulb forming part, and the excavating head is rotated in the reverse direction so that the enlarged excavating blade protrudes in the radial direction and is raised while jetting cement milk from the nozzle. To make a magnified bulb by filling cement milk into the magnified bulb forming part,
A pile burying method by a medium digging method, wherein the lower end of the PC pile is inserted into the enlarged bulb before the cement milk is solidified.   After the formation of the enlarged bulb forming portion, the excavation head is lowered to the bottom of the enlarged bulb forming portion, and the excavation head is rotated in the reverse direction so that the enlarged excavation blade protrudes in the radial direction and is raised while jetting cement milk from the nozzle. When filling cement milk into the enlarged bulb forming part by mixing the cement milk with the surrounding ground of the enlarged bulb forming part previously formed by injection of the cement milk, the enlargement having a larger diameter than the enlarged bulb forming part The pile embedding method by the underground digging method of Claim 1 which builds a bulb.   The enlarged bulb forming portion is formed by changing the cement milk injection pressure from the nozzle of the excavation head to form a large diameter portion on the lower side and a small diameter portion on the upper side, and the PC pile before the cement milk is solidified. The pile burying method by the digging method according to claim 1 or 2, wherein the pile is inserted until reaching the large diameter portion.   The insertion of the PC pile while cleaning the PC pile by spraying cement milk from the nozzle of the excavation head toward the lower end portion and the inner surface of the PC pile when inserting the PC pile into the enlarged bulb forming portion. The pile burying method by the underground digging method of 2 or 3.   When the excavation head is rotated forward, the excavation head is advanced to the bottom of the enlarged bulb forming position, and then, when the excavation head is rotated in the reverse direction so that the expansion excavation blade protrudes in the auger radial direction, the nozzle The pile burying method by the medium digging method according to any one of claims 1 to 4, wherein water is injected from the digging blade to reduce digging resistance by the enlarged digging blade.