JPS61162628A - Method of forming enlarged bulb of cylinder pile with closed end - Google Patents

Abstract

PURPOSE:To reliably form an enlarged bulb made of soil cement, by a method wherein, after a concrete pile and a rotary excavating device, engaged internally of the pile, are inserted into a support ground, the excavating device is reversed, and an enlarging blade is unfolded to form an enlarged part. CONSTITUTION:As a rotary shaft 9, engaged internally of a concrete pile 8, is rotated forward in a direction P and excavation effected by means of an excavating bit 1, the pile 8 and the rotary shaft 9 are penetrated down to a support ground. When the rotary shaft 9 is reversed in a direction Q, an enlarging blade 27, attached to a collar 10 of the rotary shaft 9, is unfolded in the direction of an outer periphery thanks to resistance of soil, and an enlarged part is formed at the lower part of the pile 8. In which case, cement milk is injected through an injection nozzle to fill the enlarged part with the cement milk. Thereafter, with the rotary shaft 9 rotated forward in the direction P, the 6nlarging blade 27 is folded, and simultaneously engagement of the excavating bit 1 with the rotary shaft 9 is released, resulting in the possibility to recover the rotary shaft 9 to a ground surface.

Description

[Detailed Description of the Invention] The present invention reliably excavates and creates an enlarged root having a required ground contact area at the tip of a cylindrical pile in one step using an excavating means, and also creates a hollow base of the cylindrical pile (hereinafter referred to as a pile). With regard to the construction method of existing tax in which the open end of the section is closed with excavation equipment, this configuration allows the total area of the tax including the hollow section to be in contact with the expanded root, reducing the receiving pressure per vehicle area of the expanded root, and reducing the The main purpose of this construction method is to increase the supporting capacity of the pile tip by increasing the ground contact area of the expanded roots. The accompanying effects will be described later. At present, the pre-closed end construction method involves fixing an excavation device to the tip of the hollow part of the pile prior to construction and rotating the pile to install the pile in the ground, or the pre-closed-end construction method, in which a digging blade is attached to a steel plate and the excavation device is installed in the ground. The post-closed-end construction method is widely practiced in which the hollow part of the pile is closed off using this excavation device after the pile is installed at the required depth using this excavation device. Regarding the edge construction method, an effective and reliable construction method that creates an expanded root with the required ground contact area at the tip of the pile has not yet been developed. The difficulty in creating expanded roots may be due to other factors, such as the normal rotation coupling mechanism, the reverse rotation coupling mechanism, and the reversal coupling mechanism between the rotating shaft that rotates the excavation device in the forward and reverse directions as well as moving it up and down, and the mechanism for separating both. This is thought to be due to the fact that it has not been fully elucidated.

The present invention solves the above-mentioned mechanisms of the rotary shaft and the excavation device using mechanical means of the connecting portion, and the construction method of the present invention will be explained below with reference to the embodiments shown in the drawings. As shown in FIG. 1, the excavation device used in this example has a steel pipe 2 serving as a reinforcing member welded to the inner surface of a conical body 1 made of a drawn steel plate, with their centers aligned. A plurality of injection ports 3 are provided in the lower half of the conical body 1, a lower blade 4, a middle blade 5, and an upper blade 6 are provided protruding from the outer surface of the cone 1, and two injection holes are provided at symmetrical positions on the outer surface of the head of the steel pipe 2. A passive metal fitting 7 is integrally provided. In Figure 1, a concrete pile 8 and a rotating shaft 9 are shown as dashed lines.
However, the lower end of the rotating shaft 9 is inserted into the steel pipe 2, and a part of the inserted rotating shaft 9 has a known piston shape and is kept watertight and airtight with rubber gaskets. The fluid pressure-fed is injected from the injection port 3. Further, a collar 10 for attaching a driving metal fitting, which will be described later, is rotated on the outside of the rotating shaft 9 and comes into contact with the steel pipe 2. The reference numeral 11 is a guide piece protruding from the end plate 12 of the pile 8, and the reference numeral 13 is a thin iron plate connecting the cone 1 and the steel pipe 2. FIG. 2 shows a local part of the coupling mechanism during forward rotation in this embodiment, and a collar 10 on the rotating shaft 9 has a square-shaped main drive fitting 14 protruding from it, and a forward rotation flange 15 at the lower end of the collar 10 is shown in FIG. When connecting the rotating shaft 9 and the excavation device for normal rotation,
By entering the steel pipe 2 below the passive fitting 7 and rotating the rotating shaft 9 in the normal direction, the web 16 of the main driving fitting 14 pushes the side surface of the passive fitting 7 to cause the excavation device to rotate in the normal direction. The vertical interlocking structure with the passive metal fitting 7 allows the excavation device to move up and down. In the present invention, the direction of rotation at the time of initial movement is normal rotation, and the state in which the excavation device can be rotated in the normal direction and operated up and down by the rotating shaft 9 is called normal rotation connection. however,
In this embodiment, prior to the normal rotation connection described above, preliminary work shown in FIG. 3 is performed.

That is, a stopper (hard steel round bar) 18 is pushed into the through hole 17 provided at the end of the normal rotation flange 15, and its upper end is fixed with a pin 19. A spring 20 is built in this through hole 17 in advance, and this spring 20 is attached to the receiving bolt 2.
1, and the spring 20 is soldered to the stopper 18 and the receiving bolt 21, so even if the pin 19 is removed, it will only protrude to a predetermined height as shown by the dashed line and will not disappear. After combining the normal rotation flange 15 in the state shown in FIG. 3 into the normal rotation connection state shown in FIG. The pile 8 is made to reach the support layer by performing a conventional tunneling method. In the above-mentioned excavation process, compressed air is injected from the injection port 3, excavation is carried out by the three stages of excavation blades 4, 5, and 6, and the soil is loosened by the stirring blade 6' of the top stage, and the excavated soil containing many air particles is The earth was placed on a continuous spiral 22 attached to a rotating shaft 9 and lifted up and removed. Reference numeral 23 is a rubber check valve that covers the injection port 3, and its three corners are fastened with machine screws, so that the compressed air is ejected in three directions.

In the support layer, the rotating shaft 9 is reversed, but the reversing flange 24 of the main drive fitting 14 enters below the other passive fitting 7, and the combination mechanism for reversing is as shown in FIG. 15 escapes from below the driven metal fitting 7 on the normal rotation side, and at the same time, the stopper 18 protrudes from the upper surface of the normal rotation flange 15, as shown in FIG.

The above state is referred to as reverse connection in the present invention. On the other hand color 1
A bearing fitting 25 is provided protrudingly on the shaft 2.
6 is inserted, and the enlarged blade 27 rotates around this shaft 26.
A pair is installed.

When rotating in the normal direction, the expanding blade 27 contracts due to the normal rotation earth pressure of the excavated earth and sand, as shown by the solid line in Figure 5, and when rotating in the reverse direction, the expanding blade 27 contracts due to the action of the reverse earth pressure of the excavated earth and sand, as shown in the solid line in Figure 5. The wings are expanded to the maximum as shown by the dashed line. Code 28 is the enlarged blade 2
This is a mooring plate that maintains the maximum wing expansion of 7. Note that the small-diameter injection port 3 provided in the rotating shaft 9 and the collar 10 shown in FIG. This promotes the expansion of the wings. FIG. 4 shows a state in which the enlarging blade 27 is expanded to its maximum extent and the excavation is carried out from below upwards, and at this time cement milk is injected from the injection port 3. The excavation is expanded to the required height shown by the dotted line in Figure 4, and the rotary shaft 9 is operated up and down to create a soil cement layer in which the cement is sufficiently spread. Next, when the excavation device is lowered into the original ground at the bottom of the hole and the rotary shaft 9 is rotated in the normal direction, the enlarged blade changes from the state shown by the dashed-dotted line in Fig. 5 to the solid line due to the forward rotating earth pressure of the soil cement and the original ground. The wings are compressed to the state shown. After this state is achieved, when a pile is loaded on the pile head, the pile 8 sinks into the soil cement layer, and the center of the pile 8 and the excavation device are aligned as shown in Figure 1 by the action of the guide piece 11. I will meet you in person.

In the final step, the cement milk 8 is injected from the injection port 3 while the rotating shaft 9 is reversed with the hollow part 29 of the pile 8 completely closed. The grout pump used in the example has a discharge pressure exceeding 15 Kgf/cm2, and can apply uplift pressure of approximately 30 tons to the pile 8 with an outer diameter of 50 cm in the closed state, and the pile 8 is equipped with a Monken and a speed reducer. It was confirmed on the ground that it was ascending with other equipment loaded. In cases where the support layer is deep or large piles are used, it is desirable to further increase the discharge pressure of the grout pump. The effects obtained when the pile 8 is pushed up with the pressure of cement milk in this final step are (1) the cement milk permeates into the original ground and strengthens the original ground;

(2) Compacting the structure of the original ground using the pressure of the viscoelastic soil cement.

(3) Increase the strength of the expanded roots by dissipating the excess moisture in the cement milk into the original ground or along the outer peripheral surface of the pile.

(4) Cement milk permeates between the circumferential surface of the pile and the earth and sand on the hole wall, increasing the frictional force on the circumferential surface of the pile.The above-mentioned truly desirable effects can be obtained. When the pile 8 is pushed up to the required position, when the rotating shaft 9 is rotated in the normal direction and then pulled out, the blade tip of the normal rotating flange 15 is moved to the end slope of the passive fitting 7 due to the action of the switcher 18. Since the blade tip of the normal rotation flange 15 is in this position, the blade tip of the normal rotation flange 15 is pulled up by sliding up the slope of the passive metal fitting 7, and the rotation shaft 9 is easily recovered. If this stopper 18 were not provided, the normal rotation flange 15 and the reverse rotation flange 24 would get under the passive fitting 7 even if the rotating shaft 9 was rotated forward and backward, and it would be impossible to recover the rotating shaft 9. However, it is quite difficult. In addition, with open-end piles, special measures must be taken to prevent the pile from settling in the raw soil cement, but in this construction method, the pile 8 is open-ended, so the pile 8 is floating in the raw soil cement. Become. It should be noted that if expanded cement is used as the cement used, the degree of compression of the expanded roots 40 to the original ground and the pile can be further increased.

FIG. 6 shows an alternative in which an enlarged blade is attached to an excavation device that is welded to the end plate 12 of a pile on the ground, and the excavation blades 4 and 5 and the steel pipe 2 are omitted.

During normal rotation, a mounting iron plate 30 is connected to the side that becomes the back surface of the upper blade 6, its base is welded to the cone 1, and one bearing metal fitting 25 is protruded from this mounting iron plate 30, so that the base is connected to the lid or The enlarged blade 27 is attached to the bearing fitting by the shaft 26.
The mechanism is such that when rotating in the normal direction, the blades are compressed by being hidden behind the mounting iron plate 30 in response to the forward rotation earth pressure, and when rotating in the reverse direction, the blades are expanded to the maximum due to the reverse earth pressure. If the bearing fitting 25 is directly connected to the upper blade 6, the mounting structure of the enlarged blade 27 will be further simplified. In this case, the construction is very simple because the hollow part of the pile is not opened or closed, and the method of expanding the root and pushing up the pile can be carried out in the same manner as in the example.

The mechanism for connecting and disconnecting the rotating shaft and the excavation device is the same as in the embodiment.

FIG. 7 shows another example of the switchper. Normal rotation side web 16
An insertion hole 31 is provided in the upper part of the normal rotation flange 15, and a straight part of the curved round bar spring 33 is inserted into the insertion hole 31 and bonded with epoxy resin. The protrusion 34 protruding from the front surface of the curved bar spring 33 is connected to the tip of the curved bar spring 33 with a hoop-shaped rope 35.
3 is made into a substantially straight line and hidden in the groove 32, and the normal rotation flange 15 is inserted below the passive fitting 7, and then the rope 35 is
It is spring-loaded to remove it. Forward rotation flange 15 during reverse rotation
When the curved rod spring 3 escapes from below the passive fitting 7,
3 is raised as shown by the dashed line, and itself becomes a locking body that prevents normal rotation connection.

Next, FIG. 8 shows a normal rotation connection of a connection mechanism different from the embodiment. A pair of T-shaped passive fittings 7 are placed on the closing plate 37 of the excavation device.
A pair of arc-shaped main drive fittings 14' protruding from the tip of the rotating shaft 9 enters below the normal rotation flange 15', and the left end of the main drive fittings 14' connects the passive fitting 7'. The rotating force is applied to the web 16' by pushing the web 16', and the driving metal fitting 14' is a normal rotation coupling mechanism that rides on a pair of uneven metal fittings 36 protruding from the closing plate 37. During reverse rotation, when the left end of the main drive bracket 14' passes the right end of the uneven bracket 36, the main drive bracket 14' is lowered by the weight of the rotating shaft 9 and rests on the closing plate 37, and the drive bracket 14' is moved over the other passive bracket 7. The machine enters below the reversal flange 24' of The rotary shaft 9 can be easily removed from the excavation device as in the embodiment without entering below the forward rotation flange 15'.

In the present invention, the above-mentioned devices such as the switch bar 18, the curved bar spring 33, and the uneven fitting 36, which prevent the forward rotation connection when the rotating shaft 9 rotates from the reverse rotation connection to the normal rotation, are collectively referred to as a normal rotation connection prevention body.

The closing plate 37 shown in Fig. 8 is a currently customary closing plate with an outer diameter approximately equal to the outer diameter of the pile and a thick plate. It transmits the axial force acting on the pile directly to the supporting ground, but for large piles with a diameter of 1 meter, the hollow part is wide and the thickness of the closing plate needs to be 40 mm or more than 40 mm due to stiffness. Therefore, the excavation equipment is expensive and it is difficult to carry out closed construction. The diameter of the circular closing plate 37 shown in FIG. 9 is slightly smaller than the inner diameter of the end plate 12 of the pile, and its thickness may be within 20 mm even in the case of a large pile. A support blade 38 and a pair of support wings 39 are integrally connected to the lower surface of this closing plate 37, so that the pile 8 can be supported by both of them. After the expanded root is created, the pile 8 and the above excavation device are connected below the expanded root 40. Next, the pile 8 is pushed up using the fluid pressure of cement milk or mortar in the same manner as in the embodiment. The amount of soil cement that enters the hollow part of the pile through the slight gap between the end plate 12 and the closing plate 37 is negligible and can be ignored. If a rubber plate band is bonded to the outer surface of the closing plate, the gap between the end plate 12 and the closing plate 37 can be closed. After pushing up the pile 8 and the excavation device to the required height of the expanded root 40, during the step of recovering the rotating shaft 9 using the detachment mechanism, rotate it at a slow recovery speed,
When cement milk or mortar is injected at high pressure horizontally or obliquely from the injection hole at the tip of the rotating shaft, the hollow wall surface 41
Most of the earth and sand compressed to the hollow wall surface 41 is dissipated, and the fluid containing cement comes into direct contact with the hollow wall surface 41.

The injection in this hollow part is continued up to a height of 2 meters to 4 meters from the lower end of the pile depending on the properties of the excavated ground, and then the rotating shaft 9 is recovered to the ground. FIG. 9 is a partial vertical cross-sectional view of the pile 8 supported on the upper part of the expanded root 40 created in the supporting ground, where 42 is a soil cement layer pressed to the outer circumferential surface of the pile, and 43 is the hollow part of the pile. It is a cement plug created in In other words, part of the axial force acting on the pile is
The force is transmitted from the end plate 12 of the pile to the closing plate 37 via the supporting blade 38 and the supporting blade 39, and compensates for the lack of adhesion between the cement plug 43 and the hollow wall surface 41, which tends to vary, and the closing plate 37 is stiffened by a cement plug 43.

Therefore, the acting axial force is transmitted to the enlarged root 40 on an approximately average basis through the pile itself, the cement plug 43, and the digging device.

Note that if the tip device of the rotating shaft shown in Fig. 11 is used, the 9th
The support blade 38 and the support blade 39 of the digging device shown in the figure can be reduced in width to just 15 mm to 25 mm of internal and external contact with the lower surface of the inner edge of the end plate 12 of the pile. This tip device will be described later.

Next, the excavation device shown in FIGS. 10 and 11 and the special tip device for the rotating shaft 9 required when using this excavation device will be explained. The diameter of the circular closing plate 37 of the excavation device is slightly larger than the diameter of the hollow part of the pile, and when the closing end is closed, the upper surface of the outer edge of the closing plate 37 is in contact with the lower surface of the inner edge of the end plate 12 of the pile, and the closing plate A lower blade 4 for excavating the ground with an area approximately corresponding to the hollow part of the pile is integrally connected to the lower surface of the pile 37. The connection between the excavation device and the rotating shaft 9 is carried out in the same manner as in the case of the first
FIG. 1 shows the state when the expanding blade 27 is expanded during reverse rotation to create an expanded root. A pair of medium expansion blades 44 are installed at symmetrical positions on the collar 10 below the installation position of the expansion blade 27, but the mounting device is the same as that of the expansion blade 27. The blades are expanded to the state shown by the dashed line in the figure and FIG. 11, and the rotary shaft 9 is rotated in the normal direction to excavate the ground in an area approximately corresponding to the actual cross-sectional area of the pile 8. When the rotating shaft 9 is reversed at a required depth, the medium-expanding blades 44 are contracted to the state shown by the solid line due to the reverse earth pressure, and the expanding blades 27 are expanded as shown in FIG. 11 due to the reverse earth pressure. state. After creating the enlarged roots 40, the means for rotating the rotation shaft in the normal direction and compressing the enlarged blades 27 by the normal rotation earth pressure is the same as in the embodiment, but during this normal rotation, the medium enlarged blades 44
The forward rotating earth pressure that should act on the collar 10 is blocked by the earth pressure blocking plate 45 protruding from the collar 10, and the compressed blade state is maintained.
7 and the middle widening blade 44 are both contracted and can be accommodated in the anti-hollow portion 29. After this state, pile hollow part 2
9 with this small excavation device. in this case,
The hollow part of the pile may be closed off with a thick closing plate, but if the stiffness of the end plate 12 is insufficient and excessive force is applied to the concrete in contact with the inner edge, the tip of the hollow part 29 of the pile may be closed off as in the previous example. If a method is taken to create a cement diameter of 43, the outer diameter can be reduced to 1.
Even in the case of meter piles, the thickness of the closing plate 37 can be 20 mm or less. The manufacturing cost of this small-sized excavation device and the excavation device in which the support blade 38 and support blade 39 shown in FIG. 9 have been reduced and modified is as follows. The manufacturing cost is almost the same as that of a 45 cm diameter excavation device, and the small-sized excavation device with each size of pile is approximately the same cost as the two-stage small-diameter excavation device of a conventional large-sized excavation device, making it a particularly profitable excavation device. A device is obtained.

For large piles, when the pile is pushed up by fluid pressure, the closing plate 37
In order to reduce the deflection of the closing plate, a pair of reinforcing plates are provided protruding from the lower surface of the closing plate and combined with the lower blade 4 in a cross shape. In addition, the 9th
Approximate closure of the hollow space by the closure plate shown in the figure is also considered as closure in practice in the present invention.

Although the present invention has been described above in a wide variety of ways, the device of the present invention is not limited to the device shown in the drawings.
The design can be changed to a letter shape, etc., and the cone 1 can also be changed to a truncated cone.

Also, although the bits of the enlarged blade 27 and the middle enlarged blade 44 are omitted in the drawing, a required mounting recess is provided above or below, and the bit is installed in this recess, as shown by the solid line in Figs. 5 and 10. The structure allows the wings to be compressed. The shapes and structures of the main metal fitting, the passive metal fitting, and the normal rotation connection blocker can also be changed to a more rational structure. Further, the rotating shaft inserted into the steel pipe 2 shown in FIG. 1 can be closed with a small diameter at the tip and an injection hole can be provided in a desired direction, so when creating the cement plug 43, a rotating shaft with this structure is used. In the embodiment, compressed air was injected from the injection port 3 during the pile digging process, but this may be changed to a method in which water or viscous liquid is injected. Furthermore, the small excavation device shown in FIG. 11 is connected and detached to the tip of the expanded root creation device shown in Patent Application No. 217371 of 1982 and Patent Application No. 216912 of 1988 filed by the applicant of the present patent. The expanded root compression construction method shown in the present invention can be carried out even if it is installed in such a manner as to obtain the same.

The features of the construction method of the present invention described above are listed below.

(1) Since the original ground with an area twice as large as the total cross-sectional area of the pile, including the hollow part, is excavated using excavation means, the ground is excavated using only high-pressure injection of water or cement milk, and expanded roots are created here. Compared to other construction methods, this construction method is more reliable in expanding the ground contact area of the expanded roots, does not damage the expanded roots of previously installed piles, and can be applied even on hard, compacted ground where fluid injection is not possible.

(2) Unless special measures are taken, such as allowing time for the soil cement to become stationary and non-flowing, open-end piles will settle into the raw soil cement of the expanded roots, and in the worst case, the value of the expanded roots will increase. However, in this construction method, the piles are closed at the ends, so these closed-end piles are suspended in the raw soil cement and rarely settle, and the next step can be carried out immediately without the need for special measures. can do the work.

(3) For open-end piles, a cement plug is created in the hollow part of the pile to expand the pressure contact area with the enlarged roots, but there is a lack of a means to compensate for variations in the adhesion force between the cement plug and the wall of the hollow part. However, in this construction method, when constructing a cement plug due to the close relationship between the excavation device and the end plate of the pile, the variation in adhesion is compensated for by the excavation device, as described above.

(4) For open-end piles, simply creating a cement plug may not create enough pressure in the hollow part, and the soil surrounding the expanded roots may swell toward the hollow area, causing the value of the expanded roots to be halved or lost. In this construction method, the hollow end of the pile is closed using an excavation device, so the above-mentioned swelling of earth and sand cannot occur.

(5) In this construction method, fluid pressure such as cement milk is applied to the closed end of the pile below the expanded root, and the pile is pushed up against the total load of the pile and the pile, as well as the frictional force on the circumferential surface of the pile. As a result, the supporting ground is compressed by the reaction force, improving its supporting performance and increasing the tip bearing capacity.Furthermore, by forming a soil cement layer that rises and compresses along the outer circumferential surface of the pile, the circumferential surface of the pile is compressed. The frictional force is increased and the total bearing capacity of the pile is significantly strengthened.

As described above, the construction method of the present invention reliably achieves the above-mentioned effects that are important in terms of bearing capacity, and the usefulness of this construction method is high.

[Brief explanation of the drawing]

Fig. 1 shows a longitudinal section of the excavation device used in the embodiment of the present invention, the basic contact structure between the pile and the rotating shaft and the excavation device indicated by the dashed line, and Fig. 2 shows the relationship between the rotating shaft and the excavation device. Figure 3 is a partial front view of the connecting device showing normal rotation connection, Figure 3 is a vertical sectional view of the device with the protruding force of the switchper installed on the forward rotation flange of the main drive metal fitting being braked, and Figure 4 shows a part of the pile tip. Fig. 5 is a diagram of the opening/closing mechanism showing the expansion blade of the expanding blade, and Fig. 6 is the opening/closing mechanism diagram showing the expansion blade of the expanding blade. A schematic external view of the installed excavation device, Fig. 7 is a vertical cross-sectional view of the normal rotation flange that brakes the protrusion force of the curved round bar spring, and Fig. 8 is the normal rotation connection of the excavation device with a protruding metal fitting and the rotating shaft. Fig. 9 is a partial vertical sectional view showing the excavation device and pile support mechanism that cuts through the lower end of the pile and closes the hollow part of the pile, and Fig. 10 shows the expanded wing retraction. FIG. 11 is a diagram of the opening/closing mechanism of the winged medium-expanding blade, and is a front view when the tip device of the rotary shaft for three-stage excavation and the excavation device are connected in normal rotation. In the symbols, 1... conical body serving as the base of the excavation device, 2... steel pipe that reinforces the conical body and connects and disconnects from the rotating shaft, 3... injection port, 4,
5 and 6...Drilling blade, 7...Passive metal fitting, 8...Concrete cylindrical pile, 9...Rotating shaft, 10...Collar, 14...Main metal fitting, 15...Normal rotation flange of main driving metal fitting, 16...Web of main driving metal fitting, 18, 33 and 36...Normal rotation connection blocking body, 22...Spiral, 24...Reverse rotation flange of main drive metal fitting, 27...Enlarged blade to open and close, 29...Hollow part of pile, 37...Closing plate serving as the base of excavation device, 40 ...Enlarged root at the tip of the pile, 42...Soil cement layer crimped to the outer peripheral surface of the pile, 43...Cement plug created in the hollow part of the pile, 44...Medium enlarged blade, 45...Earth pressure shielding plate.

Claims (3)

[Claims] (1) Connect the active metal fitting protruding from the rotating shaft and the passive metal fitting installed on the excavation device in the normal rotation, perform normal rotation digging work to reach the required depth, and then reverse the rotating shaft. The two rotating shafts and the excavation device are connected in the reverse direction, and this reversal causes the expansion blades to expand, and while the expansion blades excavate the ground larger than the outside diameter of the pile, the excavation device excavates a fluid mainly made of cement. After injecting from the injection port and moving the rotating shaft up and down to create an expanded root made of soil cement at the tip of the pile, the rotating shaft is rotated forward with the hollow part of the pile closed to release the reverse connection. A method for creating an enlarged root for a closed-end cylindrical pile, characterized in that the rotary shaft is removed and recovered from an excavation device that has closed the cylindrical pile. (2) Prior to the pile installation work, the driving metal fitting protruding from the hollow rotating shaft and the passive metal fitting installed on the excavation device equipped with the excavation blade and the fluid injection port are connected in the normal rotation. In this state, the ground can be excavated in normal rotation, and when the rotation is reversed, the driving metal fitting and the passive metal fitting are connected in the reverse direction and rotate around a rotating shaft or a shaft inserted in a bearing fitting protruding from the excavation device. The expanding blades obtained (when rotating in the normal direction, the blades contract due to the forward rotation earth pressure) expand the blades due to the reverse earth pressure, maintain this expansion, excavate the ground considerably larger than the outside diameter of the pile, and rotate. The fluid pumped through the shaft can be injected from the injection port, and when the rotating shaft is rotated forward from the reverse rotation connection, the reverse rotation connection is released and the expanding blades are contracted by the forward rotation earth pressure. , the rotating shaft and the excavating device are prevented from being connected in the normal rotation by the action of a rotational connection prevention body provided in advance on the rotating shaft or the excavating device, and the rotating shaft can be easily detached and retrieved from the excavating device at an appropriate time, and the patent A combination device of a rotary shaft inserted into the hollow part of a cylindrical pile and an excavation device that closes the hollow part of the cylindrical pile, characterized in that the method for creating expanded roots described in claim (1) can be carried out reliably. . (3) Under the expanded root filled with soil cement created by the method described in claim (1), a high-pressure flow of cement-based material flows from an injection port of an excavation device with a closed end of a cylindrical pile. This is an expanded root compression construction method that is characterized by injecting a pile and using this fluid pressure to push the closed-end cylindrical pile up to the required position.