JPH01244016A - Reflux spiral foundation work - Google Patents

Abstract

PURPOSE:To form a pile into the poor subsoil by discharging a base material into a hole by a spiral in the inside of a cylinder and pushing soft soil up from the cylinder after softening excavated soil by projecting fluids while excavating the hole by means of a bit on the end of a cylinder shaft. CONSTITUTION:An underground hole larger than an outer diameter of a cylinder 1 is excavated by means of a wing-like bit 10 mounted to the end of the cylinder 1, and at the same time, bentonite muddy water is injected from an injection port 13 to soften excavated soil. When it reaches a required depth, concrete (K) is discharged by a spiral 3 in the inside of the cylinder 1, while pushing soft soil up from the outside of the cylinder 1, the cylinder 1 is drawn up to form a concrete column.

Description

[Detailed Description of the Invention] The present invention relates to a construction method for constructing an underground structure by pumping materials constituting the foundation into the ground using a feeding mechanism consisting of a cylinder and a counterflow spiral, and its main purpose is to The purpose of this method is to improve the overall strength of foundation piles by pressing the foundation piles or the main tip of the foundation piles using pumped concrete or mortar as a material while not being cast underwater.

In almost all of the current construction methods for cast-in-place concrete piles, foundation piles are created by digging up the earth and sand in the ground, filling the underground hole with muddy water or fresh water, and placing underwater concrete. Therefore, with this construction method,
Remaining slime and boiling at the bottom of the hole,
There are always inherent dangers such as loosening of the ground and unexpected collapse of underground hole walls due to underground hole excavation, and there are also problems in muddy water management and muddy water treatment.

Furthermore, in the current construction methods for prefabricated piles, whether using the play boring method or the one-step construction method, the original ground around the pile remains loosened by excavation and cannot be repaired. In addition, expanded roots are created at the tips of the piles, but almost all of them are soil cement, which is a mixture of pumped cement milk and local soil, and cannot be compared to the concrete of the cast-in-place piles. The supporting force at the tip of Xu cannot be proportional to the contact area of the enlarged root.

The present invention uses the special technology of the present invention to solve the above-mentioned important problems found in the conventional construction methods of cast-in-place piles and prefabricated piles. The present invention will be described below according to a first embodiment shown in the drawings. Figures 1, 2, and 3 show the underground conditions and the structure of the equipment during the construction of cast-in-place piles. A rotating shaft 2 passes through the inside of the steel pipe cylinder 1 used in this construction method, and a backflow spiral is provided protruding from the rotating shaft 2. During the excavation process, the cylinder 1 rotates clockwise as indicated by the arrow P when viewed from above, and the rotating shaft 2 also rotates clockwise as indicated by the arrow P. The spirals used in earth augers and the like have each spiral tilted in a direction that causes the excavated earth and sand to rise upwards, but the spirals used in this construction method, contrary to the former, tilt in a direction that causes the material stored between each spiral to descend. This is called a backflow spiral 3 because it is rotated by the flow, and its conveyance path is called a backflow spiral route. Backflow spiral 3
The lowermost stage is formed into an annular end plate 4 which is flattened by one rotation, and a part thereof is cut out to form a discharge port 5 shown in FIG. 1st
When excavating the underground hole shown in the figure, the piston rod 7 of the hydraulic cylinder 6 is extended as shown by the action of the internal spring, and the discharge port 5 of the annular end plate 4 is closed by the closing plate 8 at its upper end.

When constructing the concrete column shown in Figure 2, oil is sent by remote control and this hydraulic system is activated.
The piston rod 7 is retracted, the closing plate 8 is lowered, and the discharge port 5 of the spiral route S is opened. The opening/closing operation of the discharge port 5 can be replaced with a mechanical lever operation or an electromagnetic device such as a solenoid. Water-stopping rubber plates may be attached to the circumferential surfaces of the annular plate 4 and the closing plate 8 that are in contact with the inner surface of the cylinder 1 to prevent water from entering the cylinder 1, but during the excavation process shown in Fig. 1. , If an appropriate amount of concrete with a water-cement ratio of around 40% with setting time adjusted to about half a day is stored in the spiral route S,
This concrete layer acts as a water stop layer in practical terms, so
A water-stop rubber plate is not necessarily required.

The excavation equipment used in this construction method utilizes a warped bit, which has the property of compressing the original ground, as an example of a prior invention.

FIG. 3 is a bottom view of the warped bit, whose central base 9 is fixed to the tip of the rotating shaft 2, and wing-shaped bits 10 are integrally attached to the left and right sides thereof. Reference numeral 11 is a central bit, and chips for digging up the ground are attached to these bits 10 and 11, but these are omitted in the drawing.

As shown in FIG. 3, the outer edge half of the wing-shaped bit 10 is curved backward with respect to the rotating direction, and a substantially fan-shaped restraining iron plate 12 is connected to the upper surface thereof. Further, the hydraulic cylinder 6 is permanently connected to the central base body 9. The feature of this curved surface bit is that the ground in the outer half, which occupies most of the excavation area, is excavated with the wing-shaped bit 10, and the excavated soil tries to heave upward, but the heave is prevented by the restraining iron plate 12. , moves along the curved surface of the wing-shaped bit 10 and is subjected to strong radial pressure toward the outside of the curved surface. The hole wall T of the original ground is compressed by the reaction, and the original ground accepts part or most of the excavated soil depending on its compressibility.

Therefore, by the above-mentioned excavation, the hole wall T in the original ground becomes denser than the original structure, and the original ground is compacted to a state similar to that in the impact method.

During the process of excavating an underground hole as shown in FIG. Because of this, it is guided to the outer circumferential route R surrounding the cylinder 1.

In the embodiment, several stirring blades 14 are provided protruding from the outer surface of the lower end of the cylinder 1, and the cylinder 1 is rotated in the same direction as the rotating shaft 2 to mix the excavated earth and sand in the outer circumferential route R with the bentonite slurry. As a result, the outer circumferential route R is filled with fluid viscous mud W1 softened by bentonite, and the frictional force between the cylinder 1 and the viscous mud W1 is small regardless of the soil quality at the construction site, and the spiral route S Cylinder 1 containing
smoothly reaches the required support layer.

Figure 2 shows the state of construction of concrete columns in the supporting layer. When the complete kinihaijin tunnel rod 7 is retracted and the closing plate 8 is lowered, the discharge port of the spiral route S that flows backward opens and the rotating shaft 2 is rotated in the direction P, so that the concrete rotates. It is pushed by the slope of the spiral 3 and is forced out from the discharge port 5. Further, at this time, since the cylinder 1 is rotated in the direction of the arrow Q, the frictional force between the inner surface of the cylinder 1 and the concrete in the spiral route S promotes the extrusion force of the concrete from the discharge port 5.

At the bottom of the hole where the amount of bentonite mud has been increased, the specific gravity of the viscous mud becomes particularly small, and concrete with a high specific gravity is extruded here, so this concrete K displaces the fluid viscous mud and flows into the center of the hole bottom. , and is forcibly spread outward by the rotational movement of the winged bit 10.

The viscous mud with low specific gravity replaces the volume with the discharged concrete and floats on top of the concrete. However, the transfer pressure of the pushed up viscous mud acts on the cylinder 1 and the spiral 3, and at the same time, the viscous mud in the outer circumferential route R It also acts on the octopus soil layer W1. If the force required to push up the entire viscous mud layer W1 is larger than the force required to push up all the devices such as the cylinder 1 and the rotating shaft 2, all the devices will be moved by the jet due to the reaction force of the concrete discharge from the backflow spiral 3. It rises inside an underground hole, similar to an artificial satellite that floats up due to air currents.

In this case, the viscous mud layer W1 within the outer circumferential route R remains in its original position, and a concrete column is pressed only in the center of the underground hole. The above results are undesirable.

In Example 1, the purpose is to forge a concrete column within the entire underground hole surrounded by the hole wall T. Therefore, cylinder 1
A load body of a required weight was loaded on the cap of the cap, and the load body and the power case of the rotating shaft 2 were connected with a wire rope, so that the weight of the load body was applied to the rotating shaft 2. Therefore,
The discharge pressure of the concrete K cannot push up the entire device (including the weight of the delivered concrete in the cylinder 1), and naturally the viscous mud layer W1 in the outer circumferential route R is pushed up.

Concrete is continuously discharged by the rotation of the counterflow spiral 3, and after this concrete fills the bottom of the hole, it heads toward the outer route R in search of a place to go.
The inner viscous mud layer W1 is pushed up. As the concrete continues to be discharged, the concrete K rises within the outer circumferential route R, and accordingly, the viscous mud layer W1 is discharged to the ground, and the concrete K rises to the upper end of the outer circumferential route R. At the time of this confirmation, the load on the cylinder 1 is released, but at this time the weight of the cylinder 1 and the backflow spiral 3 system is reduced, and the reaction force of the backflow spiral 3 discharging concrete causes the entire device to shut down. It starts to shine. Figure 2 shows the initial state of concrete column heading near the support layer at this point. The outer route R is already filled with concrete K, and if the above operations are continued, the hole wall T
A solid concrete column will be pressed into the entire underground hole surrounded by. During this forging process, the hole wall T is constantly pressed by the wing-shaped bit 10, and its structure is further tightened. As described above, a predetermined concrete column is forged in an underground hole at a predetermined location, and the entire device is recovered.

In Example 1, during the excavation process, bentonite slurry was injected from the injection port 13 to fluidize and soften the excavated soil, but depending on the soil quality, fresh water or clay water may be applied, and in some cases, a large amount of air may be blown out to cool the outer circumferential route R. In this case, soil removal will be easier if the soil is filled with a layer of air/soil with low specific gravity.

Inside the concrete column A that was forged using the above construction method,
When installing welded rebar cages, assembled steel frames, or steel pipes with spacers attached, applying a strong vibration force to these reinforcements will fluidize the concrete in the middle of the reinforcement, and the reinforcements will easily be attached to the columns. It settles in a predetermined position within A, and the desired reinforced concrete foundation pile is obtained here.

The vibration force at this time acts only on the reinforcement material and concrete, not on the ground that is subject to pollution.

The construction method of cast-in-place piles in Example 1 described above is a new construction method that breaks the general concept of construction methods, and is different from the current construction method of cast-in-place piles. There is an obvious difference in the performance of the foundation piles. Its features are listed below.

(1) The concrete that is placed using this construction method is placed deep underground, without water, and this concrete retains its original properties as it was when it was manufactured, and is not affected by deterioration.

(2) When constructing the columns, the concrete is first poured into viscous mud and then placed under heavy pressure while pushing up the weight of the entire device, resulting in a dense structure. In addition, in sandy ground, it is expected that the cement particles in the concrete will penetrate into the hole walls under high pressure, increasing the degree of integrity between the columns and the hole walls.

(3) Furthermore, the outside of this concrete column is pressed with a warped bit, and is pressed against the hole wall of the compacted original ground from its original structure.

(4) In this construction method, the ground at the location where the piles will be installed is mechanically dug up, softened, and then drained in a flowing manner. In addition, the amount of soil discharged to the ground inevitably decreases due to the ground compression effect of the warped bit.

(5) Based on the special function of the warped bit that carries the discharged concrete from the center to the outer edge and the difference in specific gravity between the viscous mud and the discharged concrete, the viscous soil on the entire bottom of the hole floats on top of the discharged concrete. , it does not become slime at the bottom of the hole. Therefore, the customary slime removal work becomes unnecessary.

(6) During construction, the pressure of mud or concrete is always applied to the bottom of the hole, so no boiling or vacuum phenomenon occurs.

(7) Since the inside of the underground hole is always filled with mud or concrete, collapse of the hole wall does not occur.

(8) Bentonite mud water management or circulating water management in the current construction method will no longer be necessary. Therefore, the auxiliary equipment is not large-scale and can be easily installed anywhere.

(9) In the drilling equipment used in this example, the outer edge of the wing-shaped bit is curved backward to form a warped bit, and while it has the ability to press excavated soil into the compressible source ground, it also supports In hard, layered ground (especially ground with poor compressibility), soil injection becomes congested and the excavation speed suddenly changes and becomes slow. At this time, as a means of confirmation, if the injection of bentonite mud from the injection port is stopped, the excavated soil around the bit will not lose its fluidity, and the bit will suddenly stop digging, and this situation can be clearly recognized on the ground, and the supporting layer The arrival is confirmed. Confirmation of this bearing layer is an important matter indispensable for ensuring the bearing capacity of the pile tip.

The excellent features of the construction method of Example 1 have been listed above, and the construction method of Example shows a construction method in which a warped surface bit is also used at the base. In other words, the construction method of Example 1 is complemented by the combined use of the warped bit. However, the illustrated cambered bit is not a critical requirement of the present invention.

For example, Fig. 4 shows another excavation rig with favorable performance for this construction method. This device is a drill-shaped angle bit for woodworking, in which acute angle bits 15 made of three or four triangular iron plates are combined radially and integrally connected to the lower surface of a disc 16. A connecting pipe 17 having a female thread on the inner surface is fixed to the upper surface. This connecting pipe 17 and
It is connected by a screw to a rotating shaft 2 having a male thread at its tip.

The injection port 13 opens on the lower surface of the disc 16 and communicates with the rotating shaft 2 through a connecting pipe 17, and a large amount of air is blown out from the injection port 13. In the excavation process, the tip of the cylinder 1 is seated at the designed position on the disk 16 to close the spiral route S, and the rotating shaft 2 and cylinder 1 are rotated at the same speed in the P direction, and the excavated soil excavated with the angle bit is Inject air into. This earth and sand passes through the outside of the disk 16 and is accommodated in the outer circumferential route R.
The clay containing a large amount of air is frequently kneaded by a plurality of stirring blades 14 installed on the outer surface of the cylinder 1 at intervals of approximately 1 meter.
The cylinder 1 reaches the support layer without congestion while maintaining the flowing air-soil properties. The drill-shaped angle bit has the property of pushing and compressing the original ground outward, and the original ground undergoes drilling process hardening due to the digging of the angle bit, and the hole wall T of the original ground becomes harder than its original structure. It will be compacted.

Also, when the woodworking awl reaches the edge of the hard structure of the wood,
Just as drilling becomes congested, when the angle bit reaches the hard ground of the supporting layer, the digging speed decreases rapidly and the amount of electricity used increases rapidly, so it is confirmed on the ground that the angle bit has reached the supporting layer. Ru.

At this point, rotate the cylinder 1 in the Q direction (see Figure 2),
When the cylinder 1 is pulled up from the disk 16 at a certain distance while rotating the rotating shaft 2 in the P direction (see Figure 1), a spiral route is created due to the pressure of the thick layer of concrete filled inside the cylinder 1. S is opened and backflow spiral 3
Concrete flowing out due to the discharge pressure overflows into the outer circumferential route R filled with lightweight air soil.

In this case, since the weight of the load body is applied to the cylinder 1 and the rotating shaft 2, the concrete discharge pressure acts on the air/soil in the outer route R, and as the concrete continues to be discharged, the concrete flows in the outer route R. is raised, the upper layer of air and soil is discharged to the ground, and the concrete reaches the upper end of the predetermined outer circumferential route R.

After this confirmation, the cylinder 1 is lowered, its tip is seated at the designed position on the disk na 6, and the spiral route is closed.

Through the above operations, the outer shell of the concrete column is created within the outer circumferential route R as required. Next, concrete must be placed in the center of the column, but before this, the rotating shaft 2 is reversed and the screw connection with the angle bit is removed, and then the rotating shaft 2 is rotated in the P direction and recovered. Then, a large amount of concrete remains inside the cylinder 1. Next, apply a light blow to the cylinder 1 made of thick-walled steel pipe, or
Pressure force using the weight of an operating crane or the like is applied to the sensor cylinder 1, and the angle bit at the tip of the cylinder is embedded in the support layer and attached to the support layer. After this, the insufficient concrete is replenished into the cylinder 1, and then the cylinder 1 is pulled out while being excavated.
Since the inside and outside of the cylinder 1 are in contact with the flowing concrete, the pulling resistance is small, and even if the support layer is deep, the cylinder 1 can be recovered to the ground without any congestion.

Through the above construction, a concrete column with an angle bit attached to the supporting layer at the tip will be created inside the entire underground hole. In this case, the hole wall T along the entire length of the underground hole becomes dense due to the hardening of the hole by drilling with the angle bit, increasing the peripheral surface bearing capacity of the pile, and furthermore, due to the hardening of the end of the support layer of the angle bit and rock attachment. A concrete column with greater tip bearing capacity can be obtained than conventional cast-in-place piles with expanded roots that do not involve compaction. Bits that are effective in hardening the hole wall T during drilling include conical bits and pyramidal bits, which can be practically used as equivalent to angle bits. In the above application example, compared to Example 1, there is an economical burden in that the angle bit is destroyed, but the work is simplified, the construction time is significantly shortened, and the support capacity at the end of the pile is definitely increased. Recognizes the outstanding merits of Furthermore, in this application example, the disc 16 of the angle bit acts as an opening/closing plate for the spiral route S, so the opening/closing device shown in Embodiment I is unnecessary. However, the discharge port is not fully opened, and the discharge area is narrowed down. Insertion of reinforcing material to be placed in the concrete column is shown in Example 1.
Follow the method used in.

When manufacturing reinforcing bar cages that are subject to strong vibrational forces, care must be taken to maintain the shape by effectively using diagonal reinforcement. The cast-in-place concrete pile construction method described above has the advantage of significantly reducing the amount of soil discharged to the ground, reducing the cost of disposing of the remaining soil, and is a construction method that opens up new innovations in foundation construction methods. The reinforcing material used is a thin steel pipe with spiral ribs protruding from the outside surface, or a thin sheet steel pipe with a corrugated outside surface, which is reinforced using reinforcing rings at the construction site, instead of the conventional and time-consuming reinforcing bar cage. By forming them, they become suitable reinforcing materials for this method. Since these thin steel pipes can be transported crushed, they are suitable for mass transportation where they are taken apart during transportation.

Next, the case where this construction method is applied as a means for root hardening of existing piles will be explained according to Example 2 shown in FIGS. 5 and 6. Fig. 5 shows a rotating shaft 2 equipped with a backflow spiral 3 passed through the hollow part of a breast-rested high-temperature concrete pile (hereinafter referred to as a PHC pile) that is integrally provided with an enlarged root 18 at the tip. The ground is excavated to a size larger than the outside diameter of the expansion plate 18 using an excavator attached to the excavator, and cement milk containing bentonite is injected from the injection port 13, and the excavated earth and sand and cement milk are kneaded by the stirring blades 14 to form flowing soil cement. The situation is shown in which PHC pile B was penetrated into the ground while building W2 and reached the Shizo layer. The direction of rotation of the rotating shaft 2 during the above-mentioned excavation step is the Q direction (see FIG. 2).

The drilling equipment used at this time had one flat bit (conventional drilling equipment) fixed to the lower surface of the disc 16, and
It is connected by passing through a connecting pipe 17 that connects to the rotating shaft 2.

In addition, the stirring blade 14 shown in FIG. 5 has two upper and lower bearing fittings 2.
It is attached to the shaft 21 inserted through the
When the rotating shaft 2 is rotated, the stirring blades 14 expand as shown in the figure, and the expanded state is maintained by the support plate 22. When the rotating shaft 2 is rotated in the direction P, the stirring blades 14 contract around the rotating shaft 2. wings and loses its stirring function. The agitating blade 14 having a contracted blade has a known structure, and the details thereof will be omitted. The opening/closing mechanism of the spiral route S is the same as that in the first embodiment. In the above excavation process, the discharge port of the spiral route S is closed with the closing plate 8 and the soil cement W2 is accommodated in the outer circumferential route R around the PHC pile B.

In the support layer, the discharge port 5 of the spiral route S (see Fig. 2) is opened by hydraulic operation as in Example 1, and the rotation shaft 2 is opened.
The concrete on the backflow spiral S is discharged while rotating in the P direction.

A load body is loaded on the head of this PHC pile B, and the structure is such that the weight of this load body acts on the rotating shaft 2. For large piles with an outer diameter of 1 meter, etc., the weight of the operating crane is loaded on the load body. to act on. In addition, for the spiral route S, a thick layer of sand is applied to the required amount of concrete above the required amount of concrete.
Fill with more water. This fairly thick layer of sand acts as a spiral pressure plug that descends as the rotating shaft 2 rotates in the P direction, pushing out the preceding concrete into the underground hole.

That is, the sand layer on the backflow spiral 3, which acts as a pressurizing plug, is an important auxiliary material that functions in the same way as a piston, which acts as a pressurizing plug in a hydraulic cylinder.

In this concrete discharging process, since the rotating shaft 2 is rotated in the direction P, the stirring blades 14 are in a contracted state, and the discharged concrete K and the soil cement W2 at the bottom of the hole are not mixed together. Therefore, the discharged concrete K, which has a large specific gravity, sinks to the bottom of the hole, pushing aside the sile cement W2, which contains a large amount of cement milk and has a low specific gravity, and as concrete continues to be discharged, the discharged concrete K fills the bottom of the hole, and its volume increases. The soil cement W2 at the bottom of the matching hole is pushed out into the outer circumferential route R, and the pushed out soil cement W2 further pushes up the preceding soil cement W2 in the outer circumferential route R. When the above-mentioned discharge operation is continued, the outer peripheral route R around the enlarged root 18 of the pile is filled with the desired discharge concrete K. In this state, the upper end of the soil cement in the outer circumferential route is connected to the discharged concrete K.
This can be confirmed on the ground because it is pushed up to the extent that it corresponds to the discharge volume of
．． 5 times or more.

At the above point, the stirring blades 14 are compressed, so the PHC
Lower the pile from the state shown in Figure 5. Then, PHC pile B
The tip of the enlarged root pin 8 is correctly seated at the designed position on the disc 16 by the guiding action of several guide pieces 23 that are in contact with the disc 16. Also, at this time, the screw connection between the rotating shaft 2 and the connecting pipe 17 is released, and the tenon protruding from the tip of the rotating shaft 2 engages with the connecting pipe 17 to maintain their central positions, but this tenon is removed. , while rotating the rotating shaft 2 in the P direction. By the above operations, as shown in Figure 6, a layer of concrete K and sand is formed in the hollow part of PHC pile B.
remains, the expanded roots 18 are surrounded by discharged concrete K, and the pile body is surrounded by soil cement. In the above state, when the PHC pile B is lightly hammered by the load of the pile head or pressed by the operating crane and the excavation equipment is pushed into the original ground, the disc platen 6 comes into direct pressure contact with the original ground.

On the other hand, since several bars 25 are protruded from the outer surface of the expanded root 18, the discharged concrete K, which maintains the design strength on the ground, and the expanded root 18 are integrated, and in Example 2, expanded cement is applied to the concrete. As a result, the discharged concrete K is pressed onto the entire surface of the hole wall T of the support layer.

For example, in a PHC pile with an outer diameter of 50 cm, the outer diameter of the expanded root is 60 cm and the diameter of the underground hole is 70 cm.
The axial ground contact area of the expanded root including the discharged concrete K is:
The total area including the hollow part of the pile body is approximately twice as large, and the circumferential ground area is approximately 1.4 times.

Moreover, this discharged concrete K is pressurized when the soil cement is pushed up and hardens under the heavy pressure of the soil cement in the upper layer, so this high-pressure discharged concrete K is
Its strength is higher than that of ordinary concrete hardened under air pressure, and it can act as an expanded root 18, resulting in the formation of high-strength super-expanded roots in the supporting layer. The tip supporting force becomes particularly strong. Of course, since the supporting force of the hole wall T in the original ground acts on the circumferential surface of the expanded body through the soil cement, the circumferential supporting force of the pile body also adds to the tip supporting force of the super-expanded roots, and the PHC pile B The total bearing capacity is increased, and even when the axial force increases dramatically during an earthquake, it is expected that the maximum amount of settlement at the tip of the pile will be extremely small. Furthermore, if the drilling equipment of Example 2 is replaced with an angle bit or the like shown in Fig. 4, the hole wall along the entire length of the underground hole will be hardened by drilling with the bit, and thus a supporting force greater than that of the example will be obtained. It is clear that In addition, during construction in areas with ground subsidence, when excavating a stratum that is at risk of consolidation, measures are taken to inject bentonite slurry from the outlet 13 to reduce the peripheral surface bearing capacity of the piles in that stratum.

Here, the characteristics of the backflow spiral 3 that brought about the useful effects seen in the examples and application examples will be described. With a conventional earth auger (downward spiral), it is possible to raise earth and sand even from a depth of 50 meters or more underground, but in this case, the earth and sand on the downflow spiral are subjected to the force of gravity as they slide down the slope of the spiral. It is piled up by gravity and passively raised by the force of the rotating spiral slope beneath the earth and sand. Therefore, the sediment itself has no kinetic energy, and the spiral sediment usually rises in a sparse state.

On the other hand, in a counterflow spiral, the earth and sand on the spiral rotate in a direction that promotes the action of gravity sliding down the slope of the spiral, so the positional energy of the earth and sand is converted into the energy of the gradual downward motion. In other words, since the earth and sand itself has kinetic energy, the earth and sand between the pitches of each spiral become dense, and this active earth and sand can easily reach 100 meters deep underground. Furthermore, other forces act on this sediment that are not present in the downward spiral. This is the rotational pressure on the back side of the spiral that acts on the top surface of the dense earth and sand between each pitch. This force results in a continuous forced downward pressure that pushes each particle of earth and sand downward without exception. In other words, the potential of the earth and sand on the backflow spiral is the accumulation of the combined forces of the gravitational force and the continuous forced downward pressure, and the lower the position of the backflow spiral, the greater the potential of the earth and sand.

This method focuses on the above-mentioned characteristic of the high-level conveying ability of the backflow spiral, and utilizes this backflow spiral as the main body of a feeding device for concrete and other materials with fluidity. When the spiral route is opened and rotated, the latent discharge pressure in the concrete is suddenly revealed. Particularly when the depth of the supporting layer is deep, heavy pressure acts on the concrete at the bottom, so the hydraulic cylinder that opens and closes the discharge port handles the heavy pressure of the concrete in addition to the double-acting cylinder. In addition, in Example 2,
During the excavation process, the rotating shaft 2 is rotated in the Q direction, so the spiral becomes a jet spiral, and when concrete and sand are applied at the beginning of construction, they rise on the spiral.
Install a vertical wall plate between the upper and lower spirals at an appropriate position to act as a detent plate, or attach the rotating shaft 2 after reaching the support layer.
The method is to rotate the concrete and sand in the P direction to deliver concrete and sand.

An advantage of this method that cannot be overlooked is that the counterflow spiral, which skillfully utilizes the effect of gravity, requires significantly less power to transport the material than the forward flow spiral, which lifts the material against gravity. It is highly likely that the large-scale backflow spiral required for constructing cast-in-place concrete piles of approximately 100% can be put to practical use.

As is clear from the explanation of Examples 1 and 2 and application examples described above, in the process of excavating an underground hole, the spiral route that flows backward in the cylinder is closed, and the softened excavated soil is guided to the outer circumferential route surrounding the cylinder. A feeding device consisting of a cylinder and a counterflow spiral is made to reach the required depth, and then the spiral route inside the cylinder is opened, and the base material on the spiral route is discharged into the underground hole by the rotating downward pressure of the counterflow spiral, and this pressurized foundation is The gist of the present invention is a series of interconnected processes in which the material pushes up the previously softened soil in the outer route, replaces the volume with the previously softened soil, and feeds the pressurized foundation material into the outer route. As an extension of this, it is possible to make various modifications to the designs of the various means of foundation construction and the various attachment devices required for the present invention.

In addition, although different means and different devices were used in the excavation process and the discharging process of the basic material described in the above embodiments and application examples, it is possible to interchange the devices and operating means by making some changes in the design. It can be done.

For example, the left and right wing-shaped bits 10 of the drilling equipment of Example 1 are not fixedly connected to the central base 9, but the central base 9 and the wing-shaped bit 10 are connected with a pin, and the left and right wing-shaped bits 10 are rotated around the pin. If the structure is configured so that the blades can be compressed, as in the application example, when concrete is pushed up to the outer circumferential route R and then recovered while rotating the rotating shaft in the direction P, the excavator with the blades compressed will also be recovered at the same time, and the cylinder 1 will be recovered at the same time. A large amount of concrete remains inside, and construction methods similar to those in the applied example can be implemented.

In addition, several stirring blades were integrally protruded from the outer surface of the enlarged root 18 of the PHC pile of Example 2, and during the excavation process, the tip of the enlarged root 18 was seated on the disc 16 of the excavation equipment, and an appropriate If the design is changed so that the enlarged root 18 can also rotate in conjunction with the excavation equipment using an engaging metal tool, it is possible to excavate in the same manner as in the application example with this tip closed during the excavation process, and in addition, in the support layer, it is possible to It is possible to create a high-strength super-expanded root by pushing up concrete around the expanded root by operating exactly the same way as in the example.

When the above method is used, the stirring blade 14 and the hydraulic opening/closing devices 6, 7, and 8 provided on the rotating shaft are unnecessary, and various operations for super-expanded root creation are simplified.

Furthermore, expanded roots can be easily created using the cast-in-place pile construction method of Example 1. That is, several bearing fittings 20 are protruded in a line in the vertical direction at symmetrical positions on the front and back sides of the outer surface of the lower end of the cylinder 1, and pins 21 are inserted through the bearing fittings 20.
1, which forms a vertically long curved quadrilateral with a wide bottom side and a narrow top side.
When the pair of enlarged bits are rotatably installed and the cylinder 1 is turned in the P direction, the curved surface of the enlarged bit compresses along the circumferential surface of the cylinder 1, and when the cylinder 1 is turned in the Q direction, earth pressure is applied. However, the mechanism for contracting and expanding the blades is the same as that of the stirring blade 14 shown in FIG. 5.

The expansion root is created after cylinder 1 reaches the supporting layer.
When the rotating direction of the bit is changed to the Q direction and the bit is operated, the expanding bit begins to open due to earth pressure, and at first the outer corner of the lower side of the expanding bit gouges the hole wall T, and the expanding bit gradually expands until it reaches the maximum expanded blade. This maximum wing expansion is achieved by the support plate 22 protruding as appropriate.
The support layer is supported in pressure contact with the support layer, and an enlarged hole wall in the shape of a truncated cone with a wide base area is created in the support layer. During this process, the injection port 13
Since bentonite mud is injected from the excavated soil, it becomes soft mud with a low specific gravity.

Completion of drilling the enlarged hole wall with the enlarged bit is confirmed when the amount of electricity used has passed its peak and decreased. After this confirmation, the rotating shaft 2 is turned in the P direction, the discharge port 5 of the counterflow spiral 3 is opened, and the concrete is extruded.However, the discharged concrete with a large specific gravity is shaped into a truncated conical shape as the winged bit 10 and the enlarged bit rotate. Soft mud W with a small specific gravity spreads over the wide bottom surface of the hole and gradually fills the enlarged hole wall at the bottom of the hole.
1 is pushed up into the outer circumferential route R, and the expanded root of the desired cast-in-place concrete pile is created here. Of course, in this case, when recovering the cylinder, the cylinder 1 is pulled out while being rotated in the P direction.

The equipment used to carry out this method, which produces the useful effects described above, has a unique structure, and the material-pumping force of this equipment is a combination of mechanical force and gravity. That is, the main body of the device is a counterflow spiral pump that pumps basic materials such as concrete directly downward along the direction of gravity, and the mechanical force of the pump is applied by gravity. This pump consists of a cylinder serving as an outer shell and a rotating shaft equipped with a counterflow spiral housed within the cylinder. The special functions of the backflow spiral, which is the driving force for material pumping, its special pumping capacity, and its operation method have been previously detailed, so I will not repeat them again. , as shown in Embodiment 1, there is a case where rotational operation is required, and as shown in Embodiment 2, there is a case where rotational operation is not required. Regardless of whether or not this rotational operation of the cylinder is necessary, this counterflow spiral pump is required to have the following structure and functions in addition to the material pumping function.

(1) The spiral route of this pump has a structure that allows its tip to be opened and closed.

(2) A drilling bit attached to the tip of a rotating shaft or cylinder,
The structure is such that the original ground can be excavated to a size larger than the outside diameter of the cylinder.

(3) It must have the function of injecting the required fluid into the bottom of the underground hole through the rotating shaft.

(4) A device that mixes the earth and sand excavated with a bit and the ejected fluid is installed on a cylinder or rotating shaft.

The above conditions are required for the pump as a whole, and if the cylinder cannot satisfy the conditions, the rotating shaft may satisfy the conditions.

The upper equipment used in this construction method consists of a power unit, a pressurizing equipment, a material feeding equipment, and other attached equipment, but since these are provided with conventional machinery and equipment, these are not ordinary machinery or equipment. Since this is a matter well known to those skilled in the art, the explanation thereof will be omitted.

To summarize the above, this foundation construction method is constructed as desired by the operation of a characteristic backflow spiral pump that meets the requirements in item 4 above. Unprecedented in similar cases, this construction method allows foundation piles to be obtained that have a high degree of bearing capacity that exceeds current standards.

In Example 1, several stirring blades were attached to the outer surface of the lower end of the cylinder 1 to create a mixing device for the excavated earth and sand and the discharge fluid.
In the case of a long cylinder, the rotational power required to operate the cylinder will be excessive. The following is a discussion of how to deal with this situation. First, cylinder 1
A steel pipe collar with an inner diameter slightly larger than the outer diameter of cylinder 1 is fitted into the tip of the lower end of cylinder 1.
A large number of stirring blades 1 are mounted on the outer surface of this collar, which is 1 meter to 2 meters long, so that it can rotate freely around the collar.
4 protrudingly provided, and a pair of passive metal fittings protrudingly provided at targeted positions on the outer surface of the lower end of this collar, so that the above collars are connected to the cylinder 1.
A ring that is thinner and narrower than the plate thickness of the collar is fixedly connected to the outer surface of the tip end of the cylinder 1 to prevent it from sliding down when recovering the collar, and is further screwed into the cylinder 1 to prevent the collar from sliding upward. The color is suppressed by the bolt group. On the other hand, a pair of main drive fittings are provided projecting at symmetrical positions on the outer edge of the upper surface of the disc 16 of the excavating device shown in FIG. 4 or 5.

In the case of the above equipment, during the process of digging cast-in-place piles, the cylinder
The tip of the screw is seated on the disk 16, and the spiral root S is closed and excavated. At this time, the disk 1 rotating in the P direction
A pair of active metal fittings modified on 6 push a pair of passive metal fittings protruding from the collar to rotate the collar in the P direction.

During this excavation process, bentonite mud is injected from the injection port 13, so the earth and sand excavated by the bit and bentonite mud are accommodated in the outer circumferential route R, and are kneaded by a large number of stirring blades 14 on the rotating collar, resulting in two fluids. The soil becomes soft and muddy.

That is, the same mixing effect as when rotating a long cylinder can be obtained by the rotational movement of only the collar, eliminating the need for the power required to rotate the cylinder 1 and simplifying the entire operation.

In the above example, since the rotational power of the upper part is single,
Good results can be obtained when applied to small diameter locations.

To create an enlarged root at the tip of a cast-in-place pile, make the collar longer and attach a pair of enlargement bits (described on page 30) to it, and the desired enlarged root can be obtained in the same manner as described above.

Furthermore, the construction methods of the application examples described in the second line of page 14 to the first line of page 19 can be modified as follows. In the application example, a large number of stirring blades were installed on the cylinder, but in this modified example, the cylinder 1 was rotated in the Q direction opposite to the rotation axis 2,
This cylinder 1 is equipped with a continuous or intermittent forward flow spiral. During the excavation process, the spiral root S
Since it is closed, the excavated soil that has been softened by injecting air enters the outer route and rides in the downward spiral of the cylinder.

At the support layer, the cylinder is pulled up a little to open the spiral route and the concrete is discharged. This concrete overflows into the outer circumferential route, rides the cylindrical downward spiral, follows the preceding earth and sand, and rises within the outer circumferential route, and when it reaches a predetermined position, the concrete discharging process is completed. When the cylinder 1 is rotated at a particularly low speed, the same construction as described above can be carried out by rotating the cylinder 1 in the P direction and equipping the cylinder 1 with a continuous or intermittent spiral that flows downstream in the P direction.

Finally, on page 29, lines 8 to 20, we explained the method for creating super-expanded roots at the tips of existing piles, but here we will describe another simple method for creating super-expanded roots. FIG. 7 shows a cross section of the special press mechanism disposed on the rotating shaft 2, which cuts longitudinally near the lower end of the enlarged root 18 (stirring blades are omitted in the drawing). Although omitted in the drawing, as shown in Fig. 6, the tip of the expanded root is seated on the disc 16 of the excavation device, and a pair of driving metal fittings protruding from the outer edge of the disc 6 are used to move the expanded root. A pair of passive fittings protruding from the outer surface of the lower end are pressed, and the force of the rotating shaft 2 rotates the enlarged root 18 via the disk 16. During the excavation process, the tip of the expanded root 18 is closed with the disk 16, cement milk is injected into the earth and sand excavated with a bit, and the mixture is kneaded with a large number of stirring blades protruding from the expanded root to form the inside of the outer circumferential route R. Filling the soil cement is as shown in the previous example.

On the other hand, three arms 26 are protruded near the tip of the rotating shaft, each arranged at a center angle of 120 degrees, and a movable ring 27 is placed on the upper surface of the arms 26.

The upper part of the donut-shaped movable ring 27 has a high outer peripheral edge.
The inner peripheral edge is low, and the upper surface is concave as shown in the figure. A rubber band 28 of medium hardness is fixed to the outer surface of this movable ring 27, and this rubber band 28 is in contact with the inner wall of the pile. A fixed ring 29 whose upper and lower surfaces are convex like a Soroban bead is provided above the movable ring 27 at a distance from its permanent position, and integrally protrudes from the rotating shaft 2. , is configured to engage with the upper concave surface of the movable ring 27. The hollow part 30 of the lower pile B of the PHC pile is filled with concrete designed to have high strength in advance of the school rescue project, approximately 1.5 times the theoretically designed amount. This concrete with the maximum size of the coarse aggregate reduced to an appropriate small diameter passes through the gap between the outside of the fixed ring 29 and the inner wall of the pile B, and the gap between the inside of the movable ring 27 and the rotating shaft 2, and forms the expanded root 18. It reaches the top of the disk 16 on which is seated.

When the expanded roots 18 reach a predetermined depth in the supporting layer, the rotating shaft 2 is reversed, the rotating shaft 2 and the excavation equipment are separated, and the rotating shaft 2 is gradually pulled up, allowing the movable ring to escape from the upper surface of the applied concrete. Stop the rotating shaft at the correct position. During this process of pulling up the rotary shaft 2, the concrete in the hollow part 30 is subjected to upward movement of the upwardly inclined surface of the fixed ring 29 and the upwardly inclined surface of the movable ring 27, but the structure of the inclined surfaces of both rings 29 and 27 allows the concrete to move smoothly. The concrete does not slide up along the axis of rotation 2.

Next, the pile B is slightly pulled up and out by 5 cm to create a gap between the disc 16 and the tip of the pile, and the force of the press-fitting device using the weight of the operating crane as a reaction force is applied to the power case at the upper end of the rotating shaft 2. is applied to lower the rotating shaft 2. Then, due to the resistance of the concrete and the frictional resistance of the rubber band 28 against the inner wall of the pile, the movable ring 27 does not move along with the rotating shaft 2, but engages and presses the descending fixed ring 29 on their mutual slopes (
This is shown by the dotted line in FIG. ), and the hollow part 3 of Xu
0 is closed by the contact surface structure of the fixed ring 29 and the movable ring 27, and the concrete receives the closing pressure of the rotating shaft 2 that descends. The concrete is discharged into the outer circumferential route through the narrow gap between the tip of the pile and the disc 16 due to the above downward pressure of the rotating shaft 2. This concrete with strong discharge pressure pushes up the soil cement W2 accommodated in the outer circumferential route R and rises within the outer circumferential route R between the enlarged root 18 and the hole wall T. The downward movement of the rotating shaft 2 is stopped when the tip of the rotating shaft approaches the disk 16, and then the pile B is lowered to seat the tip of the pile on the disk 16. At this time, the expanded root The outer circumferential route R around 18 is filled with discharged concrete K, resulting in the state shown in Fig. 6, and a super-expanded root is created at the tip of the PHC pile B. When the rotary shaft 2 is recovered, the movable ring 27 returns to the arm 26, the special press mechanism is released, and no suction phenomenon occurs in the hollow portion 30.

During the above process, whether or not the closing pressure of the special press mechanism of the present invention can be applied to the concrete depends on whether the rubber band 28 attached to the movable ring 27 always behaves in unison with the movable ring 27. ing. In the embodiment, one protrusion 31 is provided at the center of the inner surface of the rubber band 28, and this protrusion 3
1 into a single concave strip provided on the outer surface of the movable ring 27, and also by gluing the contact surfaces of the rubber band 28 and the movable ring 27 together. It has been shown that the rubber band 28 behaves integrally with the movable ring 27 and remains in an unreleasable state until the outer surface of the rubber band 28 is worn out due to kinetic friction with the inner wall of the pile and is discarded. For large piles, the height of the movable ring 27 is increased,
A plurality of protrusions are provided on the inner surface of the rubber band 28, and the protrusions 3
1 is preferably fitted into a plurality of grooves provided on the outer surface of the movable ring 27. Further, instead of the above-mentioned rubber band 28, a plurality of large-diameter O-rings filled with cloth may be used. The material of these bands 28 and O-rings may be changed to urethane foam or the like. In addition, the inner diameter of the lower pile is 2 cm from the standard.
If the inner and outer diameters are small and the dimensions of the movable ring and sealing material are designed, the sealing material will not be damaged when the upper pile passes.

According to the simple construction method described above, there is no need to supply a considerable amount of sand and a large amount of water above the concrete in the pile hollow part 30, the pile installation work is done in a single layer, and the work time required for installation is reduced. will be significantly shortened. In addition, internal pressure acts on the pile when concrete is pressurized, but a corresponding external pressure in the opposite direction acts on the pile from the fluid in the outer circumferential route R, so the pressure difference between the inside and outside of the pile is small, and the pile No internal pressure breakdown occurs.

The above simple construction method can be applied to the installation of cast-in-place piles using cylinder 1. In this case, the cylinder 1 is filled with concrete and excavated, the rotary shaft 2 is moved up and down at an appropriate height in the supporting layer, and the concrete is pressurized by a special closing mechanism consisting of a fixed ring 29 and a movable ring 27. By repeating this several times, it is possible to raise the concrete to the entire length of the outer circumferential route R. Special closing mechanism 2 that descends during this construction
7 and 29, the weight of the concrete above acts as an overburden load, so even if the outside diameter of the pile exceeds 2 meters, the pressing force required of the upper device will not be as large as the one on the left. Note that there is a backflow prevention valve (
Not shown for official use. ), the concrete does not enter the rotating shaft 2 when pressurizing the concrete. The pressurizing mechanism for concrete used in the simple construction method described above is nothing but a huge concrete pump consisting of a cylinder 1, a rotating shaft 2, and special closing mechanisms 27 and 29 on the rotating shaft.

In the above embodiment, a drilling device with a bit protruding from the underside of the disc 16 was left at the tip of the pile, but since this buried drilling device would be expensive for large piles, the drilling device was recovered. The special cases obtained are explained below.

In this special example, the upper end of a short steel pipe having an inner diameter approximately 5 cm smaller than the inner diameter of the cylinder is integrally connected to the inner surface of the tip of the cylinder 1 via a flange. Furthermore, three passive pieces are provided protruding toward the center at equal intervals on the inner wall of this short steel pipe. The movable ring 27 of the rotating shaft 2 is placed on the flange of the short steel pipe configured as described above.
When the movable ring 27 is seated, the lower convex surface of the fixed ring 29 fixed to the rotating shaft 2 is engaged with the upper concave surface of the movable ring 27, and the hollow part 30 is closed. When the hollow part 30 of the cylinder 1 in this state is filled with concrete and the rotating shaft 2 is rotated, the three arms 2 protruding from the rotating shaft 2 move the three passive pieces provided on the inner surface of the short steel pipe. The cylinder 1 with a large number of protruding stirring blades is rotated. At the tip of the above-mentioned rotating shaft, a drilling bit that can be compressed during recovery is attached to dig.
The mode of excavation is as shown in the previous example.

When the support layer is reached, the rotating shaft is raised to the required height, and then the special closing mechanisms 27 and 29 are activated to press-fit the rotating shaft 2, and this reciprocating movement is repeated several times. The excavated soil in the short steel pipe below the movable ring 27 and the traveling softened soil in the outer route R are pushed up by the pressure of the concrete discharged during the press-fitting operation and are discharged to the ground, and the discharged concrete is in the outer route R. K is satisfied. In this case, since the disk 16 is not used, the above-mentioned curved enlarged bit is attached to the tip of the cylinder 1, and the tip of the cast-in-place pile is enlarged and excavated to create an enlarged root with a wide ground contact area. It is desirable to do so. After completing the above work, operate the rotating shaft connected to the drilling equipment to rotate the cylinder in the direction of shrinking the expanding bit.
and the rotating shaft 2 are recovered above ground, but a large amount of concrete inside the cylinder 1 remains in the underground hole, and a concrete column with an enlarged root is created inside the underground hole.

The special construction method can be applied to construction land where there are scattered stones or obstacles. In this case, water is first supplied into the cylinder 1 and the excavation is carried out as described above. If an obstacle is encountered during excavation, the rotary shaft 2 is removed and replaced with a shaft equipped with orange beer or diesel to clear the obstacle, and then the rotary shaft 2 is returned to the cylinder 1 to continue excavation work. .

In the supporting layer, concrete 2 is pumped into the tip of the cylinder using a regular concrete pump, and after exchanging the volume with water, special construction is carried out, such as lifting the concrete into the outer route R as described in the previous example. Can enforce the law. In this special case of the rotating shaft mechanism, if a rubber plate is fixed to the upper concave surface of the movable ring or the lower convex surface of the fixed ring, underground pressure water is prevented from entering the hollow part 30 of the cylinder 1.

The construction method of the present invention has been explained in detail using each of the above examples, but the common feature of each example is that
The purpose is to push up the discharged concrete using the kinetic pressure and fill the outer circumferential route R with this pressurized concrete.

Therefore, the hole wall T in the original ground around the outer circumferential route R is subjected to the dynamic pressure of the rising semi-fluid concrete, and the
As in the case of receiving a pulsating internal pressure of /cm2, the surface layer structure is compressed and becomes dense, and as a result, the degree of integration between the concrete in the outer route and the hole wall T is increased, and this dense compaction inevitably increases. The circumferential bearing capacity of the pile due to the shaped hole wall T is strengthened.

The pressurizing action of flowing concrete with pressure not only compresses the hole wall T mentioned above, but also causes the greatest dynamic pressurization to occur at the bottom of the underground hole, which is the turning point of the direction change of the discharged concrete. act. In other words, the original ground at the bottom of the hole acts as a reaction force and causes the discharged concrete to rise, and the original ground is always subject to this reaction. Due to this maximum dynamic pressure, the original ground at the bottom of the underground hole, including the expanded roots, is extremely compressed and its structure becomes denser, resulting in a stronger tip-bearing capacity for the cast-in-place piles produced by this construction method.

In this construction method described above, the original ground at the bottom of the hole and the original ground at the hole wall T are compacted by the dynamic pressure caused by the flow displacement of concrete, and the unique effect is to strengthen the tip bearing capacity and circumferential bearing capacity of the pile. No effect can be expected with any of the current conventional cast-in-place pile construction methods. In other words, this construction method is a new construction method that treats the entire underground hole as a pressure pipe and applies internal pressure to this pressure pipe.

In this construction method, the strength of the concrete pressure that pushes up the pre-softened soil in the outer route R is determined by the strength of the pushing-up resistance of the softened soil. It is desirable to fill the outer route R with soil and increase the discharge pressure of the concrete that pushes up this air soil, thereby increasing the pressure exerted by the concrete on the underground hole that will become the pressure pipe. This makes it easier to dispose of leftover air and soil.

Next, the basic material delivered into the cylinder 1 of this construction method is not limited to the above-mentioned concrete, but also includes high-strength mortar mainly made of cement and mortar mainly made of polymeric materials such as epoxy resin. In addition, in soft ground improvement work, sand piles or loose piles can be created using sand or sand-mixed gravel with an appropriate particle size distribution. Among these, rose pile has particularly good water permeability, so
If this is constructed in a planned manner in a soft sand layer that is prone to liquefaction,
Excess moisture in the ground is discharged to the ground during an earthquake, preventing soil liquefaction and improving the load-bearing capacity of soft ground.

[Brief explanation of the drawing]

Figures 1, 2, and 3 show Embodiment 1 of the present invention. Figure 1 is a diagram of the operation of the tip of the device during underground hole excavation, and Figure 2 is the initial operation of concrete column construction. Fig. 3 is a bottom view of the excavating rig, Fig. 4 is a slope view of another excavating rig, Figs. 5 and 6 show Embodiment 2, and Fig. Figure 6 shows the operating state of the lower end of the PHC pile and the tip of the device during the excavation process, Figure 6 is a partial longitudinal sectional view showing the lower end of the PHC pile and its surrounding structure after installation in the support layer, and Figure 7 The figure is a cross-sectional view of the lower end of the PHC pile, showing the structure of the special closing mechanism for the rotating shaft used in the simple construction method. In the drawing, code A...Concrete column, B...PHC pile, K
...discharged concrete, R...outer route, S...spiral route, T...hole wall of original ground, W1...viscous mud, W2...
Soil cement, 1... cylinder made of acid pipe, 2... rotating shaft, 3...
Backflow spiral, 4... Annular end plate, 5... Discharge port of backflow spiral, 6... Hydraulic cylinder, 7... Piston rod, 8...
Reverse flow spiral closing plate, 10... wing-shaped bit with warped surface, 12... earth and sand suppressing iron plate, 13... fluid injection port, 14
... Stirring blade, 15... Sharp bit, 16... Drilling equipment disc,
18... Expanded root of PHC pile, 25... Fence provided on expanded root,
27...Movable ring, 28...Watertight rubber band, 29...
Fixed ring.

Claims (1)

[Claims] A drilling device attached to the tip of a rotating shaft that excavates an underground hole larger than the outside diameter of the cylinder that houses the rotating shaft equipped with a backflow spiral, and injects the required fluid to soften the excavated soil and create a backflow spiral. Closing the route and guiding the softened earth and sand to a peripheral route surrounding the cylinder while allowing the cylinder to reach a required depth, and then opening the spiral route,
Applying downward pressure from a rotating counterflow spiral to the foundation material delivered into the cylinder, this pressure discharges the foundation material into the underground hole, and the previously softened earth and sand in the bottom of the hole and the outer route are pushed up by this foundation material. A counterflow spiral foundation construction method featuring: