JPS63277318A - Specific inner drilling pile work closing hollow part of pile - Google Patents

Abstract

PURPOSE:To increase the bearing force of pile by a method in which the ground is excavated by a bit attached to the top of a rotary shaft piercing the hollow part of a pile, and soil is mixed with a fluid by a stirring blade and raised along the outer periphery of the pile. CONSTITUTION:A shoe 5 with an angled steel bit 7 is attached to the tip of a rotary shaft 4 piercing the hollow part 3 of a pile 1. A stirring blade 13 to be expanded or contracted according to the turning direction of the shaft 4 is attached to the upside of the shoe 5 and a shutter consisting of rubber plates 22 and 23 to prevent the inflow of soil into the hollow 3 is also provided. Mud water injected through the shaft 4 is mixed with the excavated soil to form a cement hardened layer stronger than the original ground between the pile and the pit wall.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an excavation device attached to the tip of a rotating shaft that passes through a hollow part of a pile, excavates the original ground to a size larger than the pile, supplies the required fluid to the excavated soil, This fluid and the excavated soil are kneaded with stirring blades to transform into fluidized soil with low adhesion, and the entry of this fluidized soil into the hollow part of the pile is blocked by a shutter that closes the hollow part of the pile. The purpose of this hollow pile construction method is to ensure that the material is guided to a circumferential route around the pile, to facilitate the descent of the pile, and to follow the pile into an excavation agitation device to reach the required depth. A ring-shaped fluidized sand layer that closely adheres to the circumferential surface of the pile and has a small adhesion force is created on the outer route to facilitate the penetration of the pile. Depending on the type of fluid that mixes with the earth and sand, a uniformly structured annular hardened layer is created that presses against the outer circumferential surface of the pile and the hole wall of the surrounding original ground, increasing the supporting capacity of the circumferential surface of the pile, and in some cases, increasing the internal support of the pile. The purpose is to create a ring-shaped soft layer that is easily deformed and to reduce the negative friction that acts on piles installed in subsidence zones.

In fact, when the tip of a pile is tightened with an excavator, the original soil at the tip of the pile, which has been loosened by the excavation, is compacted by the excavator using an external force applied to the pile head, thereby minimizing the amount of ultimate settlement caused by the superstructure during an earthquake. In addition, when the drilling equipment is a drill-shaped drilling equipment (rotary drilling equipment similar to a woodworking drill), it is necessary to make the hole wall in the original ground and the support ground directly under the pile dense. It can reduce the amount of soil.

Almost all of the current customary underground excavation methods involve passing a spiral order through the hollow part of the pile, rotatably excavating the original ground, raising this earth and sand in a spiral, replacing the volume with the earth and sand, and subsequently penetrating the pile. use means. When using this construction method, the original ground around the pile is left in a collapsed and loosened state, and the supporting surface of the supporting ground directly under the pile is clearly loosened by excavation. In almost all medium excavation methods, to compensate for this loosening of the supporting ground, an expanded bulb containing local earth and sand is created by operating an expanding excavation blade and injecting cement milk, or a cement milk expanding bulb is created by high-pressure injection of cement milk. However, in both cases, the loosening of the supporting ground during excavation of earth and the loosening of the original ground during the construction of expanded bulbs are left unaddressed. Furthermore, this method has the disadvantage that a large amount of soil is discharged to the ground because the excavated soil is forced to be sent in a spiral manner.

The special medium excavation method of the present invention overcomes all the above-mentioned weaknesses of the current medium excavation method, and can increase or decrease the circumferential bearing capacity of the pile according to the plan. A construction method for hollow piles that has the useful feature of increasing the total bearing capacity of the pile by making the texture of the hole wall of the original ground and the supporting ground directly under the pile denser, and also eliminating or reducing the amount of soil discharged to the ground. be.

The invention will now be described with reference to the embodiments shown in FIGS. 1, 2 and 3. FIG. The PMC pile A consists of a pile body 1 and an enlarged parallel part 2 provided at its lower end, and a conical shoe S is attached to the tip of a rotating shaft 4 that passes through a hollow part 3 of the pile A. The shoe S has an extension 6 at the upper end of the cone 5, which has approximately the same outer diameter as the enlarged parallel part 2 of the pile, and the cone 5 has two or three angle bits protruding from it. Three or four guide pieces 8 made of angle iron are provided protruding from the extension body 6. A discharge pipe 9 connected to and protruding from the upper iron plate of the shoe S passes through the center of the shoe and has a partially opened lower end, and a valve 10 is attached to the opening. A pair of passive fittings 11 are provided protruding from the upper part of the discharge pipe 9.

In addition, a pair of main shaft fittings 12 are protruded from the tip of the rotating shaft 4,
The manual fitting 12 and the passive fitting 1 are engaged and connected as shown in FIG. When the rotating shaft 4 is rotated in the clockwise normal rotation direction when viewed from above, the active metal fitting 12 is rotated to the passive metal fitting 1.
1 to rotate the shoe S, and the rotating shaft 4 and the discharge pipe 9 are airtightly connected to each other. Also, the rotating shaft 4 at the top of the shoe S
Several stages of stirring blades 13 are attached to the. The pair of short wings at the top are locking wings 14. The stirring blades 13 and the locking blades 14 are each attached to a shaft 16 that passes through a pair of bearing fittings 15 protruding from the rotating shaft 4, and as shown in FIG. 2, they assume the shape shown by the solid line during normal rotation. The wings are expanded, and this expanded state is the bearing metal fitting 1.
It is maintained by a support fitting 17 welded to 5. When the rotating shaft 4 is reversed, the stirring blade 13 and the locking blade 14 are
As shown by the dashed line in the figure, the blades are contracted so that they can pass through the hollow part 3 of the pile. Reference numeral 18 is a pressure surface provided at the tip of the stirring blade 13. Next, the upper shutter of the locking wing 14 is attached. This shutter is installed on a steel tube base 19 attached to the outer surface of the rotating shaft 4. The lower device is a working shutter, and the upper device is a precautionary device. These devices are specially constructed to prevent fluidized earth and other liquids from entering the hollow portion 3 of the pile during pile installation. The lower device has a free ring 21 that can freely rotate around the steel pipe base 19 below a retainer 20 fixedly connected to the steel pipe base 14, and a donut-shaped medium hardness cloth below the free ring 21. A thin soft rubber plate 23 is attached to the lower surface of the hard rubber plate 22, and the free ring 22 is a supporting ring fixedly protruding around the steel pipe base 19. The hard rubber plate 22 has a structure supported by a curved outer surface (dotted line in FIG. 3).
is installed in a predetermined position with strong pressure on the inner surface of the pile A, so even if the steel tube base 19 rotates, the hard rubber plate 22 will not rotate.
It does not rotate due to the frictional force with the inner surface of the pile. Therefore, the free ring 21 and the soft rubber plate 23 do not rotate according to the hard rubber plate 22. Also. As shown in Fig. 3, the soft rubber plate 2
3, the extra lengths of the outer and inner circumferences are soft-bonded along the inner wall of the pile A and the outer wall of the steel pipe base 19, so that no dirt or other fluids can enter into the pile hollow part 3 above the shutter. do not have. The upper safety device is made of soft or medium-hard rubber and has a thin crown-shaped rubber plate 26 fixed to the lower surface of a fixed disk 25 attached to the steel tube base 19 with several machine screws.

Next, a shutter having a simple structure shown in FIG. 4 will be explained. A core 27 having a circular outer surface is connected to a predetermined position of the rotating shaft 4, and its upper end is enlarged to form a head 28, and a slope is formed below. An O-ring 29 with a thick cross section is pressed into the gap between the core 27 and the inner surface of the pile A, and is brought into contact with the head 28. The O-ring 29, which has a circular cross section, deforms into an elliptical shape as shown by the dotted line on the left side of FIG. 4, and presses against the inner surface of the pile A and the outer surface of the core 27, forming a shutter. The upper precautionary device is the third one.
The structure shall be similar to the precautionary device shown in the figure.

FIG. 1 shows the state of the excavation agitator and PHC pile A, which are promoting the ground at the pile installation location. The field ground is not only excavated by rotary excavation of the angle bit 7 whose excavation diameter gradually increases from the tip to the upper end, but also is sequentially expanded and compressed outward from the lower end to the upper end of the angle bit 7. When a hole is made in a wooden board by rotating a sharp-tipped awl under pressure, the board is not only scraped by the awl's blade, but also the texture of the board around the hole becomes denser. . This compaction phenomenon is even more pronounced in the ground, which has a rougher texture than wood. In this construction method, this method of excavation is referred to as drill-shaped rotary excavation, and the compaction that the ground undergoes is called drilling hardening by drill-shaped rotary excavation. From the above, the shoe S can be changed to a triangular pyramid or a square pyramid, and in this case, each edge of the pyramid serves as a bit as it is. A drilling tip may be attached to this ridge and the angle bit 7 shown. Therefore, in soft ground, as the conical shoe S excavates, a large amount of soil is pushed out to the outside of the shoe S, and as the original ground becomes harder, the amount of compressed soil in the original ground gradually decreases, and the amount of excavated soil increases. but,
In either case, the hole wall B in the original ground undergoes work hardening due to the excavation of the shoe S.

Moreover, the fluid pumped through the rotating shaft 4 and the discharge pipe 9 is
The pressure opens the valve 10 and supplies water from below the shoe S, but water, bentonite mud, cement milk, etc.
It is not a large amount of liquid that creates a muddy water condition below the pile A, but a relatively small amount of liquid that can make the excavated earth and sand flowable. In construction sites where the ground is especially soft all the way to the supporting layer, and where the peripheral surface bearing capacity of the piles is hardly expected, it is possible to apply a small amount of bentonite mud to turn the excavated soil into fluid mud. In this construction method, the feature of this embodiment is that the hole wall B along the entire length of the field ground undergoes hardening during the drilling process due to the excavation of the sled-shaped shoe S, and is modified into a denser structure than the original structure of the original ground. It is desirable to take advantage of this feature to create a hardened cement layer with a stronger structure than the original ground on the outer circumferential route R between the pile A and the hole wall B. By the way, if cement milk with a water-cement ratio of 100% to 200% is simply applied to excavated soil, some of it will coexist with the excavated soil and remain underground, but most of the highly fluid cement milk will be absorbed into the excavated soil. It is often seen that the cement creates its own route regardless of the situation and then oozes out on the ground surface, and it is difficult to expect that a hardened cement layer with a desirable structure that continues with the outer circumferential route R will be created.

Therefore, in this construction method, the excavated earth and sand are removed in an appropriate amount by the rotational movement of several guide pieces 8 protruding from the shoe extension 6, several stages of stirring blades 13 attached to the rotating shaft 4, and a pair of locking blades 14. Cement milk mixed with bentonite or CMC is forcibly kneaded to create flowing soil cement in which cement particles are evenly distributed below the pile A.

These guide piece B stirring blades 13 and locking blades 14 are connected to the pile A.
It is a tip mixer that precedes the. According to the excavation of the foot S and the descent of the pile, most of the soil cement created by mechanical means will enter the hollow part 3 of the pile, if it is assumed that the hollow part 3 of the pile is open. Rise within 3,
Although the soil cement in the outer circumferential route R becomes depopulated, in the configuration of this construction method, the shutter is attached to the lower end of the hollow part 3 as shown in the figure, to prevent the soil cement from entering. Therefore, all the soil cement below the pile A has no choice but to rise in a dense state along the excavated and weakened outer circumferential route R. In other words, the shutter in the hollow part of the pile is
It is a powerful and reliable guiding device that guides all of the soil cement to the outer circumferential route R. On the other hand, the hole wall B has the guide piece 8
The soil cement receives compressive force from the sides of the hole and the pressurizing surface 18 of the stirring blade 13, and the cement particles in the soil cement permeate into the inside of the hole wall B in the sandy ground. The degree of integration with the hole wall B is increased.

In the support layer, high-concentration cement milk with a water-cement ratio of 50% to 60% is discharged. In the sandy support layer, this cement milk is mixed with the excavated earth and sand of the original ground through the tip mixer 8,
13 and 14, and while creating a rich mortar under the pile A, the shoe S is made to reach the required depth. When the rotating shaft 4 is now reversed, the stirring blades 13 and the locking blades 14 are compressed, the passive metal fitting 11 and the driving metal fitting 12 are disengaged, and the rotating shaft 4 is ready for recovery.

Next, when the pile A is lowered, the fixing plate 3 of the enlarged parallel part 2 of the pile
The short steel pipe 31 protruding from the bottom is correctly installed at the designed position of the shoe S by the guidance of several guide pieces 8. During the lowering process of pile A, the inner surface of the pile and the hard rubber plate of the shutter are
Frictional force due to the downward movement of the pile acts, but the hard rubber plate 2
Since the pressure of the thick layer of soil cement on the outer circumferential route R acts upward on the hard rubber plate 22, normally this hard rubber plate 22
will not fall below the position shown. At the production factory, the inner surface condition near the lower end of the lower pile is inspected and repaired.
In rare cases where a thick layance on the inner surface of the pile is overlooked, or when the supporting layer is particularly shallow and upward pressure from soil cement is insufficient, the hard rubber plate 22 may slip down and lose its ability to close the pile hollow section 3. There is. The device in the upper row is a precautionary device at this time. The outer diameter of the lower end of the crown rubber plate 26 of this device is made larger by 10 mm or more depending on the standard inner diameter of the pile, so the lower half of the crown rubber plate 26 is always in a state of soft contact with the surface of the plate A. Therefore, at the point when the shutter function of the lower stage device is lost, the shutter function of the guard device is activated, and the lower half of the crown rubber plate 26 is further pressed against the inner surface of the pile under the pressure of the rising mortar. The rise is automatically blocked. That is, in the embodiment, a two-stage structure was adopted in which the upper and lower shutters prevent the fluidized sand from entering the pile hollow part 3 and reliably guide the fluidized sand to the outer circumferential route R.

Therefore, a part of the mortar created below the pile A before the pile is lowered is accommodated in the lower part of the hollow part 3 of the pile after the pile is lowered, and most of the other mortar is stored along the outer circumferential route R. The expanded parallel portion 2 of the pile and the outer peripheral surface of the lower portion of the pile body 1 are covered with high concentration mortar.

Immediately after this, at least 500
Apply more than a pound of pressure.

At this time, the angle bit 7 of the shoe S wedges into the original ground in a wedge shape, and the entire surface of the cone 5 of the shoe S comes into pressure contact with the inverted cone-shaped original ground that has been hardened by drilling. Compact the original ground with Originally, the angle bit 7 and the guide piece 8 have the function of pushing out the ``■'' outward with their side surfaces during rotational digging, and the ``■'' that rests on the upper surface of the extension body 6 of the shoe S is small. However, there may be cases where this ■ directly faces the thick short steel pipe 31 of pile A, but the pressing force applied to ■ acts sequentially from ■, which is one step higher, which is an obstacle, so this huge concentrated pressure causes ■ to The pile is broken into pieces, and the short steel pipe 31 of the pile and the shoe S are substantially in contact with each other, and at this point, the pile hollow part 3 has an outer peripheral route R.
The pressure of the fluid inside has little effect. Therefore, the upward pressure of the mortar does not act on the hard rubber plate 22 at this time.

During the above-mentioned compaction process of the support layer and the recovery of the rotating shaft, when the rotating shaft 4 is first pulled up, the hard rubber plate 22 of the embodiment moves downward from the steel pipe base 19 due to friction with the inner surface of the pile. A katsukake rod 3 that protrudes from the rotating shaft 4 easily slides down.
2 and was recovered diagonally. In addition, several steps of protrusions 33 are provided on the outer surface of the enlarged parallel portion 2 of the pile, and the outer peripheral REIT R
Powerful integration with the inner mortar has been achieved.

According to the above construction method, the expanded shoe S of the pile comes into pressure contact with the supporting ground that has been compacted by drilling and hardening, and further compacts the supporting ground. On the other hand, on the outer circumferential route R of the support layer, a hardened layer made of high-concentration mortar that has been thoroughly kneaded and has cement particles evenly distributed is created, which increases the upward supporting force of the support ground that acts on the shoe with a wide ground contact area. Enlarged parallel part 2 with protrusions 33 and pile body 1 through a hardened cement layer
The peripheral surface supporting force of the supporting ground acting on the peripheral surface of the lower part of the pile A is combined, and the tip supporting force of the enlarged root consisting of the enlarged parallel part 2 of the pile A and the shoe S is exceptionally increased.

In addition, according to this construction method, the hole wall B in the original ground is hardened by the drilling process caused by the rotary excavation of the shoe S, and the structure of the hole wall B over the entire length becomes dense, resulting in the hardening of the hole wall B in the original ground. The bearing capacity of the ground acts on the outer circumferential surface of Pile A in the long section through the soil cement hardening layer to the supporting layer, and the circumferential bearing capacity far exceeds the circumferential bearing capacity obtained with the current cement milk construction method. It is clear that it is obtained.

When the above tip bearing capacity and circumferential bearing capacity are combined, the total bearing capacity of the pile A installed by this construction method is considerably larger than the total bearing capacity of the pile body 1 installed by the impact method. There is expected. Of course, in the percussion method, driving a pile with such an enlarged root is practically impossible because the soil around the pile body 1 becomes empty and the pile body 1 becomes a long column.

Next, examples of application of this construction method to friction piles are shown in Figures 5 and 6.
This will be explained using the tip device shown in the figure.

The same equipment as in the example is used for the excavation rig, locking blade, and shutter. The case where the tip is completely tightened with a shoe is similar to the example, but in this application example, the tip of the pile is left open. In this case, an excavation device K shown in FIG. 5 is integrally fixed to the tip of the rotating shaft 4.

The drilling rig K consists of a central base body 34 and a curved bit 35 .

The lower half of the central base 34 is divided into two front leaves 36 on the left and right that are spaced apart from each other, and two rear leaves 37 on the left and right that are spaced apart from each other. It forms an integrated structure. The curved bit 35 is attached so as to be guided around a pin 39 screwed from the rear leaf plate 37 to the front leaf plate 36, and when digging, it expands as shown in the figure, and when recovering the rotary shaft 4, it rotates around the pin 39. It turns around and droops to contract its wings.

As shown in FIG. 6, the curved bit 35 has an outer edge portion curved backward in the normal rotation direction of the arrow. In addition, a substantially fan-shaped restraint plate 40 is welded to the upper surface of the outer edge of the curved bit,
The rotational diameter of the arc portion of this restraint plate 40 is the curved bit 3
The diameter shall be equal to or slightly smaller than the rotating diameter of No. 5. A drilling tip is attached to the front plate 36 of the central base 34 and the curved bit 35, but this is a known matter and is omitted in the drawing. That is, the earth and sand excavated at the outer edge of the curved bit 35 tries to rise upward, but the restraint plate 40 prevents the earth and sand from rising upward, and this earth and sand is subjected to outward pressure by the curved surface of the curved bit 35, and this Hole wall B by excavated earth and sand
is forced to be compressed.

Further, a small amount of cement milk controlled to the required amount is discharged obliquely upward from the discharge pipe 9. This cement milk and excavated earth and sand are kneaded by several stages of stirring blades 13 and locking blades 14 shown in FIG. It is further tightened by the kneading pressing force of the pressure surface 18. Since the advance excavation of the excavation stirring device and the subsequent lowering of the pile A are performed in the same manner as in the embodiment, the soil cement is guided to the outer circumferential route R by the action of the shutter. When the excavation device K reaches the required depth, the rotating shaft 4 is reversed, the stirring blades 13 and the locking blades 14 are contracted, and the excavation device K is raised to the required height. After that, the pile A is lowered to bring the tip of the pile into contact with the excavated surface of the original ground.

During this step, the curved bit 35 is pushed by the lower end surface of the pile and compressed. Next, a pressing force is applied to the pile head to push the tip of the pile deep into the original ground. At this point, the soil cement in the outer circumferential route R is no longer in communication with the soil cement in the pile hollow part 3. Next, when the rotating shaft 4 is pulled up, the hard rubber plate 22 is caught on the hooking rod 32 and recovered together with the rotating shaft 4.

With the above construction, the hole wall B in the original ground has a curved bit of 35
Under the elastic compaction force, the tissue becomes fruit. The bearing capacity of this compacted hole wall B acts on the circumferential surface of the pile through the hardened soil cement layer with a uniform structure in the outer circumferential route R, so the circumferential bearing capacity of this pile is It is expected that this will correspond to the circumferential bearing capacity of the driven pile.

The fluid used in the present method described above is not limited to cement milk or bentonite mud. For example, when excavating a clay layer in a subsidence area, use the foot S as shown in Figure 1.
The compressed air is discharged through the discharge pipe 9. The earth and sand excavated by the angle bit 7 and this earth and sand are subjected to the kneading action of the tip mixers 8, 13, and 14, and countless air particles are dispersed and spread within the excavated earth, increasing the fluidity of the viscous earth and sand. At the same time, its adhesive strength decreases. The fluidized soil modified in this way enters the outer route R by the action of the shutter and digs through the cohesive ground in the state shown in FIG. The construction after reaching the sandy ground that does not cause consolidation is carried out in the same manner as in the example. According to the above construction method, even if the viscous ground around the pile undergoes consolidation settlement, the outer and inner layers of the soft soil layer containing countless air particles created within the outer circumferential route R will easily shift and become strained. In addition, the adhesive force to the pile is small, and the negative nub fraction acting on the pile is alleviated, so that no excessive load is applied to the pile. In this case, the influence of consolidation subsidence of the original ground is further reduced by creating an enlarged parallel part 2 at the tip of the pile and increasing the thickness of the annular soft layer of the outer circumferential route R, as in the embodiment.

Here, the function of the locking wing 14 in the expanded state shown in FIG. 1 will be explained. Although the upper device has a known structure and is not shown in the drawings,
A required weight is loaded on the pile head, and the weight is connected to the case of a power device that operates the rotating shaft 48 using a wire rope or the like. When constructing this method, the hollow part of the pile 3
Since the lower part of the shutter is closed, the buoyancy of the fluidized earth and sand in the outer circumferential route R acts on the shutter. What is directly contributing to this buoyancy is the weight of the rotating shaft 4 and the power unit, but the structure is such that the weight of the weight can act on the power case as a backup. Alternatively, a structure may be adopted in which another weight of the required weight is loaded above the power case. During excavation work, the above device can balance the buoyancy, but when the pile follows, the rotating shaft 4 also follows at the same time, so the weight of the upper device is not temporarily lost, the balance of the sword is broken, and the hollow body 3 The inner rotating shaft 4 floats up due to buoyancy. The locking blade 14 is a device that automatically controls this lifting. In other words, during subsequent work on the rotary shaft, the rotary shaft 4 rises by the design dimension, but
When the locking plate 14 comes into contact with the fixing plate 30 of the pile, the acting weight of the pile is transmitted to the rotating shaft 4, and the weight of the pile and the rotating shaft is balanced with the buoyant force. The larger the diameter of the pile, the greater the buoyant force that acts on it, so the structure of the locking wing 14 should be made stronger accordingly.If the pile is large and the supporting layer is deep, a particularly large buoyant force will act on it, so A method is used to reduce buoyancy by introducing the required amount of water into the hollow space. In addition, in order to increase the weight of the rotating shaft and reduce the weight of the rotating shaft, there is a means for installing a large-diameter rotating shaft or a conventional spiral-order rotating shaft above the special rotating shaft 4 shown in the figure. is desirable. Although various types of devices can be designed to prevent the rotating shaft from floating on the ground, since installation work is required, in this embodiment, a locking blade 14 that locks automatically is used.

The construction method of the present invention, which has a wide range of application depending on the examples and applications, has been described above, but this method uses a stirring device to knead the earth and sand excavated by an excavation device with the required delivery fluid to form a uniform structure. This is a construction method that transforms into fluidized sand and forcibly guides this fluidized sand to the outer route of the pile using a shutter that closes the hollow part of the pile, ensuring that an annular fluidized soil layer is created around the pile while subsequently penetrating the pile. If a cement-based fluid is used as the supply fluid, an annular hardened cement layer with a uniform structure can be obtained around the installed pile, and if air is used,
A ring-shaped soft soil with low cohesion and easy internal deformation that is suitable for areas with land subsidence can be obtained. With the current one-step construction methods such as the digging earth and sand method and the current water jet method, it is almost impossible to create a hardened cement layer with a uniform structure like this around the pile. thought about.

As explained above, the special hollow excavation method of the present invention reliably creates a continuous annular soil cement layer with a uniform structure on the outer circumferential root around the pile in one step, and This solves the long-standing problem of increasing surface bearing capacity all at once. In addition, this construction method is characterized by the ability to create an annular mortar layer that also adheres to the circumferential surface of the pile body 1 directly above the enlarged parallel portion 2, making it easy to construct piles with enlarged parallel portions 2. By pressing force or lightly hitting the weight, it is possible to compact the supporting ground over a wide area of the enlarged root consisting of the enlarged parallel part and the enlarged shoe, making it possible to particularly strengthen the supporting capacity at the end of the pile, and to strengthen the entire support ground. A hollow part with a large supporting capacity can be installed in one step, making it highly useful.

It should be noted that the shutters, stirring devices, drilling devices, etc. shown in the examples and application examples are not limited to the devices shown in the drawings, but can be modified in various designs, for example, as shown in FIG. Crown rubber plate 26 of the upper precautionary device shown
When using the shutter as an actual shutter, the lower hard rubber plate 22 is eliminated and a crown rubber plate 26 is attached to the lower surface of the free ring 21. The position of the machine screw for attaching the crown rubber plate 26 to the free ring 21 is at the position of the illustrated machine screw 41 attached to the fixed disc 25 or inside of this position. In the device with the above design change, the lowered outer edge of the crown rubber plate 26 is strongly pressed against the inner surface of the pile by the pressure of the fluidized earth, and due to the frictional force, even when the rotating shaft 4 rotates, this crown rubber plate 26 Board 2
6 and the free ring 21 do not rotate, and the edge of the crown rubber plate 26 does not wear out, increasing durability. Even if there is a thin laitance layer on the inner surface of the pile when lowering the pile in the final process
This crown rubber plate 26 flexibly moves and responds, and the shutter function is not lost. In addition, when recovering the rotating shaft, if a pressure difference occurs between the upper and lower hollow parts of the pile of this device, the crown rubber plate 26 outside the mounting machine screw is pushed by atmospheric pressure and hangs down, allowing the upper and lower air passages to communicate. However, this modified shutter has useful features such as no vacuum phenomenon occurring below the hollow part.

In addition, when a thick flat rubber plate (soft rubber or semi-hard rubber) with approximately the same diameter as the standard inner diameter of concrete piles and steel pipe piles is attached to the fixed disk 25 with machine screws 41 to serve as a shutter, the inner surface of the pile Due to dimensional errors and errors in roundness, some fluidized earth and sand will enter the hollow part of the pile above the shutter, but when the rotating shaft is recovered, the flat rubber plate will change the mounting position of the machine screw 41 due to the weight of the fluidized earth and sand that has entered. Since the outer part hangs down and the fluidized sand flows down, no vacuum phenomenon occurs below the hollow part, and the effect of closing the hollow part second to that of the example is obtained. Therefore, the apparatus for approximately closing the hollow part of a pile, which is designed so that a vacuum phenomenon does not occur in the hollow part of the pile when the rotating shaft is recovered, also belongs to the scope of the shutter of the present invention. The illustrated example in which the upper surface of the fixed disk 25 is formed into a slope is a shape in which the fluidized earth and sand that has entered the hollow portion can easily flow down. The reason why the above-mentioned crown rubber plate 26 and the above-mentioned flat rubber plate strongly resist pressure from below, but can flexibly deform against pressure from above is because the free circular ring 21 and the fixed disk The outside part of the rubber plate 25 holds down the area near the outer edge of the rubber plate from above, while the mounting position of the machine screw 41 is designed to be far from the outer edge of the rubber plate, which is the deciding factor for a mechanically rational design. be.

When using crown rubber plates and flat rubber plates with the above-mentioned flexible adaptability as shutters, when excavating hard ground with poor compressibility, the shutters can be placed in advance of the piles downward to direct the fluidized earth and sand into the hollow part of the piles. In the case of compressible soft ground, two types of excavation methods can be used: the shutter is retracted into the hollow part of the pile to completely close the hollow part of the pile, and the fluidized earth is guided to the outer route. Therefore, even in construction sites where the intermediate hard ground is particularly thick, the amount of fluidized soil discharged onto the ground can be reduced to zero or to a very small amount.

That is, this means is a unique means in which the pile hollow part 3 is used as a regulating tank for controlling the discharge of fluidized earth and sand to the ground.The former means for storing excavated earth and sand in the pile hollow part is a public means. The above-mentioned excavation means that uses this public means in combination also falls within the scope of the special medium excavation method of the present invention. Note that the shutter used in this construction method is not only made of rubber, but may also be replaced with a shutter made of synthetic resin such as vinyl chloride or polypropylene.

In the example, upper and lower shutters were used as a precaution, but when the pile is lowered to the shoe position in the final process, the upward pressure of the fluidized sand acting on the shutters even at a depth of 10 meters is It has been found that the hard rubber plate 22 does not slip down even if the laitance is large and has a certain thickness.

From the above, the shutters used in this construction method include the hard rubber plate 22, the crown rubber plate, the flat rubber plate, etc.
A single shutter that does not cause a vacuum phenomenon in the hollow part of the pile when the rotating shaft is recovered is sufficient, and the VIP shutter shown in the embodiment can be omitted.

Also, when the left and right curved bits 35 shown in FIGS. 5 and 6 are followed in the center, and these curved bits are attached to the lower surface of a closing iron plate that closes the lower end of the pile, and this is used as an excavation device,
The hole wall B around the pile receives compressive force from the curved bit 35, and its structure becomes dense. In the case of this excavation rig, the closing iron plate must be penetrated deeper than the excavation surface when adding the outer blade to the pile cap.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a PHC pile with an enlarged parallel section in which the hollow part of the pile is closed with a shutter, and an excavation stirring device during underground excavation, and Fig. 2 is a mechanism diagram showing the opening/closing structure of the stirring blade. , 3rd
The figure is a sectional view showing the structure of the shutter, Figure 4 is a structural diagram of another shutter, Figure 5 is a front view of another excavation rig, and Figure 6 is a cross-sectional view showing the structure of the shutter.
The figure is a bottom view of the excavation rig of FIG. 5. In the drawing, symbols A: PHC pile, B: hole wall in the original ground, S
・・Conical shoe, R・・Outer route, 1・・Pile body, 2
...Enlarged parallel part, 3.Hollow part of pile, 4.Rotation axis, 5
... Cone of shoe, 6. Extension of shoe, 7. Angle bit, 8. Guide piece, 9. Discharge pipe, 13. Stirring blade, 14. Locking blade, 19. Steel pipe. Base body, 20... Holding metal fitting, 21... Free circular ring, 22... Hard rubber plate, 23...
Soft rubber plate, 24...support ring, 25...fixing disc,
26... Crown rubber plate, 31... Short steel pipe at the lower end of the pile, 32
...Hook round bar, 33...Protrusion provided on the enlarged parallel part.

Claims (1)

[Claims] A drilling device attached to the tip of a rotating shaft that penetrates the hollow part of the pile excavates the ground larger than the pile, supplies the required fluid to the excavated soil through the rotating shaft, and mixes this fluid and the excavated soil. Agitator that can compress blades attached to a rotating shaft (Kakuhan)
The blades are expanded and kneaded to transform the excavated earth into flowing earth.The shutter, which closes the hollow part of the pile provided on the rotating shaft, prevents the flowing earth and sand from entering the hollow part of the pile. A special hollow excavation method that closes the hollow part of a pile, which is characterized by guiding fluidized earth and sand to the outer circumferential route of the pile, and then penetrating the pile into the ground following a preceding excavation agitation device.