JPH01244015A - Anchor casting for foundation pile - Google Patents

Abstract

PURPOSE:To form a pile having convex stripes and to form the pile having larger shaft pressure yield strength by grouting cement milk while excavating the ground, forming a soil cement column and making grooves to the wall of a hole by means of a reamer on the upper part of a bit. CONSTITUTION:Rotation is made in the (P) direction while projecting cement milk from the tip of a bit 3 to form a soil cement layer, and at the same time, excavation is continued. After reaching a specific depth, a shaft 11 is reversed in the (Q) direction, and a reamer 12 held by 2 pieces of up and down bearing metal fittings 10 on the upper part of the bit 3 is protruded to excavate grooves. Accordingly, a pile having protruded stripes is formed, and shaft pressure yield strength and pull-out proof strength can be increased.

Description

[Detailed Description of the Invention] The present invention relates to a method of constructing a foundation, and its purpose is to provide a necessary protrusion on the outer surface of the foundation column that extends into the original ground around the pile, and to attach the pile to the original ground. The objective is to increase the axial pressure capacity and pull-out capacity of the pile.

A general view of the conventional pile construction method shows that both when creating cast-in-place piles and when installing prefabricated piles, the construction method of excavating the original ground at the installation location and creating an underground hole to house the pile, A commonly used method is to create an enlarged root or bulb at the tip of the hole to increase the support force at the tip of the pile. Originally, the bearing capacity of a pile consists of the combined force of the bearing capacity of the bearing layer against the tip of the pile and the bearing capacity of the intermediate ground against the surrounding surface of the pile. Particularly in construction sites where the bearing layer is deep and there is hard ground in the middle, the peripheral surface bearing capacity of the pile may exceed the pile tip bearing capacity.

However, despite this protrusion, no good means to strengthen the circumferential bearing capacity of piles has yet been developed using current construction methods. Multi-tiered large-diameter fences are protruded from the pile body at regular intervals, and when driving these stake piles into the ground, the gaps between the pile body and the surrounding ground between the stakes are removed. The construction method in which the piles are installed underground by repeatedly filling the pile with earth and sand is a construction method that aims to increase the supporting capacity of the surrounding surface of the pile, but the repeated work of filling with earth and sand is complicated. With long piles, the driving resistance of the pile gradually increases and it becomes impossible to drive, so it is applied as short special friction piles of about 10 meters or less, and is difficult to apply as a general construction method.

In addition, several stages of spiral blades are fixedly connected to the light end of a steel pipe pile, and this steel pipe pile is screwed into the original ground, and this steel pipe pile is made to reach the support layer, and the spiral blades are fixed to the support layer. Although some attempts have been made, in actual construction, closing the hollow end of the steel pipe pile will cause problems when screwing in the steel pipe pile, and opening the hollow end of the steel pipe pile will significantly reduce the supporting capacity of the end of the steel pipe pile, making it impractical for practical use. hard. The two bundles cited above are special construction examples for pre-fabricated piles, but cast-in-place concrete pile construction methods, such as the Benoto method, reverse circulation method, and earth drill method, include underground construction. It is not possible to find any examples of special construction in which the circumferential bearing capacity of the original ground for concrete columns is particularly strengthened. In other words, in the current construction method of cast-in-place piles, there is no action on the original ground of the hole wall of the underground hole in which the pile is built, and the surface layer of the original ground of the hole wall is tissue-destroyed by the excavation. The concrete was left in a loose state, and concrete was poured into the underground hole in this state. Therefore, the frictional force and adhesive force of the earth and sand in the original ground acting on the circumferential surface of the concrete column cannot exceed the internal frictional force and adhesive force of the surface original soil in a loose state.

Example 1 of the fixed casting method for piles of the present invention is shown in the drawings below.
Explain according to the following. The ground operating crane and upper power unit are structures that are obvious to engineers with ordinary knowledge in the field of this industry, so these are omitted and the excavation equipment that excavates the ground at the location of the pile is the first one. As shown in the figure.

An excavation device K is fixedly connected to the tip of the rotating shaft 1. Second
The drilling equipment K shown in the figure has four thick warped bits 3 integrally protruding from the circumferential surface of a central cylinder 2. A reversing section 4 is configured. A tip 5 is provided on the lower surface of the warped bit 3, and a tip bit 6 is provided protruding from the lower half of the central cylinder 2. Further, multi-stage stirring blades 7 are protruded from the rotary shaft 1, and a pressurizing rod 8 is connected to the tip thereof, and the pressurizing rod 8 is structured to press the hole wall T in sequence. Note that when excavating the ground in the intermediate layer up to the supporting layer, the water-cement ratio is 0.
Cement milk with a medium concentration of around 10% is injected from the injection port 9 at the tip of the rotary shaft 1, and this cement milk and excavated soil are repeatedly operated by the warped bit 3 and the multi-stage stirring blades 7, and are thoroughly mixed. It is mixed into soil cement.

As described above, excavation is carried out while creating a soil cement layer inside the underground hole M. The warped bit 3, which is the main moving body of the drilling equipment K, has the characteristic of compressing the hole wall T.

In other words, the excavated earth and sand excavated by the tip 5 gathers outward along the curved surface of the curved bit 3, and
Due to the rotational movement of the outer curved surface of the hole, strong pressure is applied toward the hole wall T, and in soft ground, a portion or a considerable amount of the excavated soil is forced into the surrounding original ground. Although the amount of earth and sand injected into the original ground is reduced in hard ground with poor compressibility, strong pressure from the curved surface of the warped bit 3 acts on the hole wall T.
The hole wall T, which has been loosened by the tip 5, is immediately transformed into a strongly compacted state due to the curved surface configuration of the warped surface bit 3. Therefore, the hole wall T of the underground hole H drilled by the above-mentioned drilling device K is compacted and becomes a denser structure than the original structure, and the pressurizing round bar 8 of the stirring blade protruding in multiple stages is repeated. The density is increased by the pressure action.

When the drilling equipment K reaches the hard ground of the supporting layer, the rotational resistance of the excavated soil against the outer curved surface of the warped bit 3 increases rapidly, so the power consumption of rotational power increases sharply, confirming that it has reached the supporting layer. can. At this time, high-concentration cement milk with a water-to-cement ratio of about 50% is injected to create a hardening soil cement layer with a large amount of cement at the bottom of the underground hole H.

The drilling process for creating an underground hole described above is actually a preliminary process of the fixed casting method of the present invention described below.

In other words, through the above drilling process, the pile installation position is
An underground hole H with a hole wall T compacted by the warped bit 3 and the pressurized round rod 8 is created, and semi-fluid raw soil cement that has not hardened yet is stored in the underground hole H. It will be done.

On the other hand, among the four warped bits mentioned above, the one facing directly
The pair of warped bits 3, 3 serve as a reamer base to which a reamer for carving a groove in the hole wall T is attached. Two upper and lower bearing fittings 10 are fixedly connected at a distance of 5 cm to 6 cm in a U-shaped steel consisting of the outer edge curved part of the warped bit 3 that serves as the reamer base and the inverted part 4. A reamer 12 that can be rotated by a certain angle is attached to the inserted shaft 11.

This reamer 12 is connected to the arrow P as shown by the solid line in FIG.
In the drilling process in which the rotating shaft 1 rotates in the direction, the tip of the cutting edge 13 is in pressure contact with the hole wall T and falls sideways and does not operate, and the head 15 of the reamer 12 hits the inner wall of the warped bit 3, causing the reamer to 12 is held at the position indicated by the solid line. FIG. 1 shows the front of the reamer in a sideways state.

When the drilling device K reaches a predetermined depth in the supporting ground and the work of remixing the hardening soil cement in the bottom area of the underground hole H is completed, the rotating shaft 1 is then reversed in the Q direction. Then, the pressure of the soil cement acts on the slope 14 of the cutting edge of the reamer as shown in FIG. When it penetrates into the reamer, the earth pressure of the original ground acts suddenly on the reamer 12, and the reamer 12 rotates around the shaft 11 to the position shown by the dashed line, causing the back surface of the reamer to warp into the notch of the bit 3. The reamer 12 is held at the base of the curved surface 16 at the position indicated by the dashed line. Incidentally, the curved part of the warped bit near the attachment of the reamer 12 is locally cut out. That is, at this time, the reamer 12 rises to the state shown by the one-dot chain line in FIG. 3, and enters the groove heading state. In this step, since the rotating shaft 1 rotates in the Q direction, the cutting edge 13 of the reamer 12 also moves in the Q direction of the arrow. The advancing front surface of the cutting edge 13 is thin and sharp and is configured to easily cut into the original ground, and the cutting edge slope 14 gradually becomes thicker to form a cutting edge trihedron. The upper and lower hole wall ground is subjected to the advancing pressure and the pressing force of the prismatic end face 17 of the reamer and the outer surface of the curved part of the warped bit 3, so that there is no escape into the underground hole H and the ground is in a triaxial pressure line state. The cutting edge slope 14
The forging grooves G are carved here, and the hole walls T are further compacted.

In Example 1, the rotary shaft 1 is operated by a hydraulic motor, and the number of revolutions per minute is set to 18 times during drilling, and in the forging process of the groove g, a small-capacity hydraulic pump is used, and the number of revolutions of the rotary shaft 1 per minute is set to 18. The number was reduced to six. In addition, multiple pulleys were used to limit the rate of rise of the rotating shaft 1 by the wire rope to 3 meters per minute. Accordingly, the pitch of the heading grooves g carved by one reamer 12 is 50 cm, but the pitch of the heading grooves g carved by the other reamer 12 is delayed by half a turn, so the pitch of the heading grooves g is 50 cm. The interval between the pieces is 2
It will be 5cm. FIG. 4 is a schematic cross-sectional view of the above-mentioned underground hole H, in which the hole wall T has regularly spaced forging grooves g, and the texture of the original ground of the hole wall sandwiched by the grooves g is particularly dense.

In addition, when creating the subsequent heading groove g, the heading groove g does not collapse even on the hole wall in sandy ground where it was feared that the preceding groove g would easily collapse, and the soil cement that quickly flows into this groove g will not collapse. Pile excavation experiments have demonstrated that this soil cement can harden while supporting the wall surface of a pile. When the soil cement in the underground hole H hardens, a helical protrusion D that digs deeply into the original ground of the hole wall T protrudes from the outer surface of the soil cement column. Outer diameter φ
The depth of the groove g cut into the underground hole H in which medium-sized piles up to 600 mm will be installed shall be at least 50 mm or more.

Moreover, the axis C1 of the shaft 11 to which the reamer 12 is attached is the first
As shown in the figure, it is not parallel to the axis of the rotating shaft 1, but slightly obliquely, and the end of the reamer 12 is located at the base (on the right side of the figure).
Since the tip is configured to be more upward, the leading edge of the cutting edge 13 also points upwards to some extent, and the locus of the groove g carved in the hole wall T becomes a helical shape as designed.

When the rotating shaft 1 is pulled up at a predetermined low speed while being rotated gradually as described above, two forging grooves g are formed in the hole wall T of the underground hole H as planned.

In this construction method, the main purpose is to increase the circumferential bearing capacity and tip bearing capacity of the pile, so the P
The HC pile installation work will be carried out as follows.

Be sure to use a stick pile α for the bottom pile at the bottom. A multi-stage bracket 17 is protruded from the bracket pile α at regular intervals, and the outer diameter of the upper end is the same as the outer diameter (nominal outer diameter) of the shaft between each bracket 17. 19 is the anchoring plate 1 of the upper pile β
9 is welded and connected.

Several pieces of arcuate spacers 20 are attached to the outer surface of the reinforcing band 18 of the upper pile β, and the pile is guided to the center of the underground hole H by the guiding action of the spacers 20. Fushi pillar α
An enlarged part γ having the same outer diameter as the outer diameter of the clasp 17 is formed at the lower end, and a reinforcing band 18 attached to this enlarged part γ is formed.
is equipped with an arc spacer 20, and the enlarged part γ is connected to the underground hole H.
guided to the center of The tip of the lightweight rotating shaft 1' passed through the hollow part of the pile is screwed to a threaded rod 22 protruding from the upper surface of the closing plate 21, and the closing plate 21 is placed slightly ahead of the pile.
The steel blades 23 connected to the lower surface of the underground hole H are rotated to stir the soil cement in the underground hole H, so the soil cement below the pile is always fluidized, and the pile does not rise high at the intermediate position of the underground hole H. Reference numeral 24 is a guide piece that guides the rotating shaft 1' to the center of the hollow part of the pile.

Finally, the enlarged part γ of the pile α rides on the closing plate 21, its hollow part is closed by the closing plate 21, the steel wing 23 is press-fitted into the original ground at the bottom of the hole, and the lower end surface of the enlarged part γ of the pile is is grounded to the bottom of the hole in the support layer. The special fixed pile α shown in Figure 6 can be easily manufactured by installing a simple inner mold for the shaft inside the formwork of a pile with a diameter 13 inc larger than the outer diameter of the shaft. It will be understood by industry engineers without any need for explanation. Therefore, for example, the pile β in the upper stage of PHC is a φ400 pile, but the ground contact area of the enlarged part γ of the fence pile α is φ450, and in some cases it expands to the ground contact area of a φ500 pile, and the tip of the pile is completely covered. Since the pile is in a closed state, it is a natural result that the bearing capacity at the end of the pile is much greater than that of a normal pile with an open end.

In any case, the point that the support performance of piles produced by this anchored casting method is significantly different from that of piles produced by conventional construction methods is that the support performance of piles produced by this anchored casting method is significantly different from that of piles produced by conventional construction methods. In this case, the axial load on the upper half of the pile during the loading test is extremely large compared to the axial load on the lower half of the pile. The amount of axial load on the upper half of the pile increases as the circumferential bearing capacity of the ground around the pile increases, and if this priority axial load is L1, then Since the force is a constant value L, the axial force burden on the lower half pile is inevitably the difference between the two (L-L1), which cannot be exceeded. From the above, if there is hard ground in the middle layer of the upper half, and the circumferential bearing capacity of the pile due to this ground is particularly large, no matter how large the bearing capacity of the lower pile is, the lower pile will still be used in proportion to its capacity. There may be cases where the axial force applied does not act. If the axial force L during the loading test is made four times the maximum allowable axial force (long-term) of the PHC pile reinforcement, if the axial force burden on the lower pile becomes too small, the lower pile will actually The above can be omitted. In other words, for piles installed using this anchored casting method, which has a new peripheral support structure, the friction and shear bearing capacity of the ground against the peripheral surface are particularly large, so it is not always necessary for the pile tip to reach the support layer. I come to the conclusion that no. This construction method is unique in that it is not necessarily necessary to have excessive bearing capacity for so-called PHC piles. Therefore, the following features are obtained.

(1) This construction method is the best method for installing friction piles with large bearing capacity, and enables economical design.

It is very clear that the fact that this friction pile (more precisely, shear friction pile) has an exceptionally large bearing capacity compared to friction piles made by other construction methods is due to the difference in the ground support structure between the two. be. However, for this friction pile or the lower pile of the friction pile, a stick pile α is used to connect the soil cement column and
Aim to integrate with PHC pile.

Contrary to the above, the following is a list of the ground in which the PHC pile must reach the supporting part, and the features of this method on ground that are considered to be particularly problematic are clarified.

(A) When soft ground continues up to the deep supporting layer If the ground up to the supporting layer is sandy ground with an N value of 0 to 3, or equivalent viscous ground, install piles in the supporting layer.

(B) Even if there is sandy ground with an N value of around 30 before reaching the ground support layer where liquefaction is expected, in construction sites where liquefaction is predicted to occur during an earthquake, the pile tips are installed in the support layer. do.

(C) Ground where ground subsidence is expected In areas where ground subsidence is expected, the pile tips are installed in the supporting layer, ignoring all circumferential bearing capacity of the upper ground.

In the above ground, the tip of the pile must be installed in the bearing layer, but
At this time, Fuji Pile α, which will be the lower pile, and the soil cement column and hard supporting ground have a mutual uneven structure (Fuji Pile 17).
, ridges D) to form a single composite body, the fact that its axial pressure resistance and tensile resistance are exceptionally large compared to piles with the same outer diameter installed using other construction methods is due to the fact that It will be obvious to engineers in the field that this is a natural result of differences in the ground support structures of the construction methods. Therefore, this construction method provides the following second and third features.

(2) This method is most suitable for constructing piles in ground that is likely to liquefy during an earthquake.

(3) This construction method is optimal as a pile construction method in areas with ground subsidence.

In addition, in the above-mentioned ground, it is sufficient to create a heading groove g on the hole wall below the required depth and provide a convex groove D on the foot protection soil cement column, but do not create a heading groove g on the hole wall in the upper layer. .

In Example 1, a two-step construction method using pre-boring was explained, but when constructing the above-mentioned special ground, a forging groove is not created in the upper hole wall T, so a simple casting method that installs piles in one step is implemented. can. Figures 7, 8 and 9 show Example 2 of this simple casting method, and the lower half of the lower pile shown is from the pile body (omitted for convenience of drawing) about 10
It has a large diameter of 1.5 cm, and is configured with an enlarged diameter of about 5 meters in length. A rotating shaft 1 passes through the hollow part of the pile, and a closing plate 21 is attached to the tip of the rotating shaft 1. A digging blade 25 is installed on the lower surface of the closing plate 21. During the excavation process, the active metal fitting 26 protruding from the tip of the rotary shaft 1 pushes the passive metal fitting 27 protruding from the upper surface of the closing plate 21 to turn the closing plate in the direction of arrow P, and the excavating blade 25 excavates the original ground. The excavation is carried out while enlarging the pile α1. An injection port (not shown in the drawing) is provided at the lower end of the rotating shaft 1, and low concentration cement milk or bentonite mud is injected during the excavation process.

The earth and sand excavated by the excavation blade 25 rises from around the closing plate 25 and is supplied with viscous liquid, and this earth and sand becomes soft mud by the rotational movement of the enlarged stirring blade 28 which expands when rotating in the P direction. This mud rises as the pile penetrates through the hollow part of Xu and the outer circumferential route R between the enlarged pile α1 and the hole wall T, but the mud that has entered the narrow hollow part protrudes from the rotating shaft 1 in multiple stages. Due to the rotational movement of the fixed blades 29, it becomes fluid and does not become clogged.

In the excavation process, the closing plate 21 is advanced by about 1 meter in front of the expansion shaft α1, and the excavation is carried out while creating soft mud that flows below the pile, so the pile sinks into the ground without traffic jams.

As shown in FIG. 7, two shafts 30 are fixedly protruded at symmetrical positions on the lower surface of the closing plate 21, which is the basis of the excavation work described above. This shaft 30 has a reamer 1 for carving a groove in the hole wall T.
2 is rotatably mounted, and this reamer 12 is connected to the shaft 30.
A nut 31 is attached to the lower part of the shaft 30 so that it does not come off. When the closing plate 21 rotates in the direction of arrow P, the reamer 12 falls sideways as shown by the solid line, and its tip merely comes into pressure contact with the hole wall T. Reference numeral 32 is a reamer stopper, and the reamer 12 does not turn inward from the position indicated by the solid line. On the other hand, a curved pressing steel plate 33 is integrally hung from a part of the outer periphery of the closing plate 21, and the arcuate outer surface of the pressing steel plate 33 rotates while being in contact with the hole wall T. Further, this pressed steel plate 33 is provided with a notch portion 34 for receiving the reamer 12.

Since the closing plate 21 is constructed as described above, when the closing plate 21 is turned in the direction of the arrow Q shown in FIG. The notch 34 of the pressed steel plate 33 rotates under the earth pressure.
It got stuck and stopped at the position shown by the dashed line in Figure 7.
The hole wall T is in an upright position in which a heading groove g is carved, and when the closing plate 21 is turned in the Q direction, a heading groove g is carved in the hole wall T by the reamer 12. The pressed steel plate 33 plays an important role in suppressing the protrusion of earth and sand and forcing the groove g into the hole wall T when the groove g is carved with a reamer.

FIG. 8 shows a state in which the rotary shaft 1 is rotated in the P direction and the closing plate 21 has reached the required depth of the support layer while excavating the original ground with the excavating blades 25.

In the support layer, the enlarged pile α1 is stopped at a predetermined position, and the strong rotary shaft 1 is advanced 6 meters inward and outward to excavate the support layer to a predetermined depth. During the excavation process, the closing plate 21 is always used.
Since the reamer 12 is turned in the P direction, the reamer 12 is in a prone position and is in an inoperative state.

For the above support layer, high concentration cement milk is injected. In the posture shown in FIG.
5 suppresses the upper surface of the main drive fitting 26, so that the closing plate 21 also rises along the rotating shaft 1. In this way, by injecting cement milk from the rotary shaft 1 and reciprocating several times from the bottom of the hole shown in the figure to near the bottom of the enlarged pile α1, the excavated soil and cement milk are separated from the excavation blade 25 and the enlarged stirring blade. 2
It is sufficiently kneaded by the rotational movement of 8, and the expanded stick pile α
Highly concentrated soil cement will be created below No. 1.

At the end of this soil cement creation process, the enlarged stirring blade 28
When it approaches the enlarged stake α1, the rotating shaft 1 is reversed and the closing plate 21 is rotated in the Q direction. Immediately, the reamer 12 is rotationally displaced from the prone position shown in FIG. 8 to the upright position shown in FIG. Gouged into the original ground. Further, the enlarged stirring blades 28 are also contracted around the rotating shaft 1 by the rotational action in the Q direction. Groove g formed by the reamer 12
During the forging process, the rotary shaft 1 is rotated at a low speed as in Example 1, and the descending speed of the rotary shaft 1 is limited to the required speed (
Uses a hydraulic cylinder mechanism, etc. ), but all these operations are operated by the operation of the upper mechanical load.

Therefore, in the hole wall T below the enlarged stake α1, grooves g of the desired shape are formed in a helical pattern up to a height of about 5 meters at the desired pitch intervals. When the rotating shaft is pulled up after the closing plate reaches the bottom of the hole in this way, the driving metal fitting 26 slides on the lower slope of the short hook part of the passive fitting 27 of the closing plate and rises, and the rotating shaft 1 and the closing plate I will leave 21. Further, at this time, since the enlarged stirring blades 28 are contracted to a small size, the rotating shaft 1 is easily recovered to the ground using the hollow part of the pile as a passage. After that, the pile is press-fitted so that the tip of the enlarged pile α1 comes into contact with the closure plate 21, and the pile is pushed into the original ground by at least the dimension of the excavation wing 25 by tapping or press-fitting, and the closure plate 2
1 is directly pressed against the supporting ground.

In Example 2, the outer diameter of the pile body was 50 cm, and the enlarged pile α
The outer diameter of 1 is 60 cm, the diameter of underground hole H is 70 cm, and the groove g
Since the depth of groove g was designed and constructed to be 5 cm on each side, the diameter of the groove g is 80 cm.

Therefore, a helical forging groove g with a depth of 5 cm is created in the original ground of the hole wall T in a section 5 meters upward from the depth of the predetermined supporting ground, and an enlarged fence pile α1 is installed at the bottom of this hole. After the plate-hardening soil cement external column hardens, the maximum outer diameter of the helical protrusion D becomes 80 cm. The above-mentioned enlarged fence pile α1, foot protection soil cement outer shell column, and hard supporting ground of the hole wall T constitute an integral composite body due to their mutual uneven structure. Considering the limit of the ultimate support capacity of the composite body of these three, assuming that the flange 17 and the protrusion D at the interlocking part of the concavo-convex portion of the three do not break (they can be further strengthened in shape and structure), The shear failure of the original ground sandwiched between the spiral ridges D has to be its limit. In other words, the expansion pile α1 is supported by the full force of the shear resistance of the annular part of the original ground with a height of 5 meters and a diameter of 70 to 80 cm, and a circular area of 70 cm in diameter (soil cement outer shell column). It receives the compressive resistance force of the supporting ground acting on the base area of the body (the sum of the base area of the expanded pile α1), and is supported by the supporting ground over a three-dimensional wide area. It is clear that piles that are supported by a wide range of three-dimensional support ground cannot be obtained using current low-pollution construction methods. It has become clear that it is possible to install piles underground that have an equally strong tip bearing capacity. In the second embodiment, the reamer 12 is installed on the closing plate 21, but the design of the reamer 12 can be changed to be installed at the tip of the pair of enlarged stirring blades 28. In this case, the manufacturing cost of the closing plate 21 serving as the burial device is reduced.

In addition, in the conventional construction method, an enlarged bulb is created in the support layer using open-ended piles, but as a means of compensating for the solidity of the pile, cement milk is injected into the hollow part, and a pile is placed in the upper half of the enlarged bulb. The special structure allows the tip of the pile to float and spreads the axial force acting on the pile widely from the end of the pile to the bottom of the bulb, so when a pull-out force is applied to the pile, the tip of the pile easily pulls up from the bulb. There are drawbacks.

Contrary to the above, in the pile of Example 2 installed in the support layer, the entire length of the enlarged fence pile α1 is integrally fixed in the foot hardening soil cement by the protruding installation of the fence 17, and the foot hardening soil cement is Due to the overhanging configuration of the helical protrusions, it is deeply anchored in the hard wing support layer, so the full force of the three-dimensional shear resistance of the hard support ground acts on the expanded stick pile α1, and the pull-out resistance of the pile is particularly strong. Become. Therefore, the following fourth feature is obtained.

(4) Piles installed in the support layer using this construction method are best used as foundation piles for special structures where pull-out forces are likely to occur.

In conventional construction methods, whether it is the impact method or the low-damage construction method, it is assumed that large pull-out forces do not act on the lower pile.
A type A PHC pile with low prestress was used as the lower pile, but in the special case mentioned above, it became clear that lower piles such as B or C type PHC piles should be used in this construction method. .

Xu's fixed casting method described above creates soil cement, which is a slow-hardening fluid, around a pre-formed pile, casts and fixes this soil cement in the original ground, and integrates this soil cement with a pre-formed plate. Soil cement acts as an important medium to integrate the pile and the original soil.

Embodiment 3, which will be described below, is a more active and simple construction method that does not require any medium and uses a concrete column, which is the main body of the pile, and the original ground as a single composite body. In Example 3, the fixed casting method of the present invention is applied to a reverse construction method that circulates water. FIG. 10 shows the state of the excavating device K1 when it reaches the supporting ground and then creates an enlarged hole H1 at the bottom of the hole. Suction shaft 1 sucks up water and soil. At the tip of the shaft, four angles 37 are welded to the outer surface of the conical base 36 for excavating the shaft underground hole H.
A tip 5 (only one angle is shown) is attached to this angle 37, and a suction shaft 1 passes through the center of the conical base 36. The tip is open, and a tip bit 6 is fixed to the tip. Drilling rig K. is suction shaft 1
. It excavates the ground by rotating in the Q direction.
This device K. When the suction shaft 1 reaches a predetermined depth in the support layer. Rotate in the Q direction. The opening/closing mechanism of the contracting wing expansion blades of the lower stage expanding wings 38 and the upper stage expanding wings 39, which will be described below, is a well-known means commonly used when creating bulbs for existing piles, so the details thereof will be omitted. That is, suction shaft 1. When turned in the P direction at the bottom of the hole, the lower expansion blade 38 and the upper expansion blade 39 move toward the suction shaft 1. The pin 41 inserted into the bearing fitting 40 connected to the It is in a position to excavate. The slopes of the oblique sides 42 of the lower enlarged wing 38 and the upper enlarged wing 39 are made the same,
Continuing on from the outer hole wall ground excavated by the upper stage enlarging wing 39, the lower stage enlarging wing 38 excavates even more.

Therefore, this rotating shaft 1. When it is gradually pulled up while turning in the P direction, the enlarged underground hole H is created as the excavation trajectory of both enlarged wings 38 and 39. was created, and this underground hole H. The upper end of the hole is the same as the diameter of the shaft underground hole H, and is connected to the shaft underground hole H without any difference in level. Figure 10 shows an enlarged underground hole H approximately 5 meters high in the supporting layer. Shows the state in which it has been created. The slope of the neck hole wall is made gentle to prevent the collapse of earth and sand, but during excavation, the original ground is pressed diagonally upwards, so the surface layer of the slope of the hole wall is pressed and tightened, preventing the collapse of earth and sand. be done. As described above, the underground hole H is expanded into the supporting layer. After creating the hole, scoop up the slime at the bottom of the hole and attach the suction shaft 1. The excavator is raised and recovered while being rotated in the Q direction. At this time, the upper and lower enlarged excavation blades 38 and 39 contract to a small size so that they can easily pass through the shaft underground hole H. Above underground holes H, H. The preparation work is a preliminary work for performing the fixed casting method of the present invention.

In this way underground holes H, H. After this, a public rotary table is passed through a Kerry bar with a hopper for receiving concrete at its upper end, and the required number of tremie pipes are connected to this Kerry bar, and the tips of the tremie pipes are made to reach the bottom of the hole. A large reamer 12 is attached to a pin 41 inserted into a bearing fitting 40 shown in FIG.
2. When passing through the shaft underground hole H, the blade shrinks to a small size as shown by the solid line. The drawing shows one reamer 12.

The other large reamer is connected to the tremie tube reamer 3 in a completely symmetrical position and in the same shape as shown in the diagram. This large reamer 12. A curved bit 3 (see FIG. 1) with a small reamer 12 attached thereto shown in FIG. 1 is integrally connected to the tremie tube 43 slightly above the installation position. The tremie tubes equipped with the above two types of reamers are installed in underground holes H and H.

After the concrete is inserted into the hopper, it is passed through the tremie pipe 43 to the enlarged underground hole H. Concrete will be delivered inside. When the layer thickness of the incoming concrete exceeds approximately 4 meters, first, the tremie pipe 43 is rotated at a low speed of 3 to 4 times per minute, and the large reamer 12 is rotated. Reamer 12 begins to open due to the rotational resistance of the concrete. The sharp tip of the cutting edge 13 is
Expanded underground hole H. The cutting edge 13 penetrates into the hole wall T, and eventually the large reamer 12 is formed. The blades are expanded to the maximum in the state shown by the dashed line, and this state is maintained by the supporting action of the locking fitting 45 fixed to the bearing fitting 40. When the cutting edge 13 carves a groove in the hole wall T, the local earth and sand tries to protrude into the enlarged hole, but the wide-area curved guard 44 attached to the base of the cutting edge 13 and pressing against the hole wall T prevents the earth and sand from moving. In order to prevent extrusion, this earth and sand pushes the original ground of the hole wall in the vertical direction, and a forging groove g is created here. If the tremie tube 43 is turned in the P direction and pulled up while limiting the pulling speed to about 3 meters per minute, the enlarged underground hole H will be reached. Spiral-shaped forging grooves g with a pitch interval of 40 cm to 50 cm are created on the hole wall. Expanded underground hole H. The rotational speed of the tremie tube 43 varies from 1 to
The pulling speed may be reduced to 2 times/min, and in this case, the pulling speed of the tremie tube 43 is also slowed down, and the design is such that a helical groove of a required pitch is carved. In this way, the tremie tube 43
Since the rotor speed is set to be low, the output torque of the tremie tube increases, and the depth of the forging groove can be made to a depth of about 10 cm for large piles.

Underground hole H is enlarged by continuous supply of concrete and operation of tremie pipe. After making a forging groove in the parallel hole wall T, when the tremie tube 43 is turned in the Q direction, the large reamer 12 is formed. Under the influence of earth pressure and concrete pressure, the blade shrinks to the state shown by the solid line in Figure 11, and becomes large enough to easily pass through the shaft underground hole H.

The warped bit 3 connected to the tremie tube 43 in this way is moved into the shaft underground hole H, and the tremie tube 43 is moved to the Q
As mentioned above, when rotated in the direction, the small reamer 12 receives earth pressure and becomes erect, and is in a position to create a forging groove.

The operation for creating the forging grooves after this raised state was described in detail in Example 1, so the explanation will be omitted here. However, in this case, since concrete is supplied through the tremie pipe, it is necessary to control the reamer 12 so that the operation of the reamer 12 is always carried out within the concrete while constantly checking the position of the upper end of the concrete in the shaft underground hole H. The underground hole H is enlarged by the above heading structure operation. A forging groove G is carved as planned in both the shaft part underground hole H, and concrete is stored in the underground hole.

In addition, the effect of increasing the bearing capacity of this casting method can be enhanced by using expandable cement for the concrete used in the non-casting method and applying the pressure of the concrete column to the hole wall T after the concrete has hardened. However, the details will be explained later.

By the way, if the underground hole is shallow (about 10 meters or less), inserting the prefabricated reinforcing bar cage into the concrete of the underground hole will easily scuttle and achieve the purpose, but the underground hole will become deeper and the time of concrete pouring and the reinforcing bar cage will be different. If a long period of time passes between the time of sinking and the time of settling, the thixotropic property of concrete (the property of concrete in a static state losing its fluidity and becoming immovable by some external force) becomes high, and it becomes almost impossible to set the reinforcing steel cage in a sinking position. It becomes possible. In order to reduce the thixotropic properties of concrete, it is more effective to apply a mild vibration force to the concrete than to apply enormous pressure. When a vibration force is applied to a reinforcing bar cage, the reinforcing bar cage will move at high speed, so welding between the main bars and stirrups must be done carefully. To give an example of reinforcing bar cage arrangement, a height of 20 cm is placed inside the upper end of the main reinforcing bar.
A steel plate ring inside and outside m is arranged, a main reinforcing bar is welded to the outer surface of this steel plate ring, the third or fourth dividing point of this steel plate ring is grasped with a chuck provided on the branch arm of the vibrator, and the steel plate is Vibration force is transmitted to the entire reinforcing bar cage through the ring, causing the reinforcing bar cage to sink into the concrete. In order to guide the reinforcing bar cage to the center of the underground hole H, a required number of spacers are attached to the required positions of the reinforcing bar cage. To connect the upper reinforcing bar cage to the lower reinforcing bar cage, the lower ends of all the upper reinforcing bars are placed evenly on the outside of the steel plate ring of the lower reinforcing bar cage, and all of these main bars are welded to the steel ring. The above-mentioned steel plate ring is also integrally welded to the upper end of this upper reinforcing bar cage. Therefore, when the steel plate ring of the upper reinforcing bar cage is grasped with a chuck and the vibration force of the vibrator is applied, the vibration force is transmitted to all the reinforcing bars in the upper and lower tiers, and the concrete around this reinforcing bar cage receives the vibration force and becomes fluid and soft. However, the reinforcing bar cage sinks smoothly into the concrete. In this way, the required number of reinforcing bar cages are successively connected, so even if the depth of the underground hole exceeds 50 meters, there will be no congestion due to the sinking of the reinforcing bar cages. In addition, as a means to connect the upper and lower reinforcing bar cages straight, it is possible to weld hoop reinforcing bars with accurate perpendicularity to the inside of the lower end of the main bar of the upper reinforcing bar cage at an appropriate position. During connection work, this hoop reinforcing bar rides on the lower steel plate ring, making it easy to connect straight reinforcing bar cages.

By placing the above-mentioned reinforcing bar cages, all the construction work for cast-in-place reinforced concrete piles will be completed.

Comparing conventional cast-in-place piles and cast-in-place piles created by the fixed casting method of the present invention, the biggest features of this pile are the underground hole H in the shaft and the enlarged underground hole H.

A forging groove g is carved in the hole wall T, and the original ground of the hole wall is the forging groove g.
The concrete becomes compact due to the compressive force during formation, and the concrete flows into the compacted heading groove g of the hole wall. After the concrete hardens, the outer surface of the concrete has a convex strip D that overhangs the compact original ground. This means that the concrete column and the original ground form a single composite body. In particular, in Embodiment 3, when the reinforcing bar cage is sunk, vibration force is applied to the concrete along the entire length of the underground hole through the reinforcing bar cage. The original ground of the hole wall T can be further compacted by the flow pressure of the concrete. That is, high pressure of fresh concrete corresponding to the depth of the underground hole is applied to the hole wall T.

By the way, this concrete column with protruding stripes D and
The content analysis of the bearing capacity of the composite body consisting of the surrounding original soil is the most important basic problem of the present invention.

In the conventional construction method, the supporting force acting on the peripheral surface of the pile of the needle plate is
The contact surface of the original ground in contact with the circumferential surface of the pile, expressed geometrically, from the circumferential surface of the first cylinder A (see Figure 4) with no thickness around the pile, the adhesive force and frictional force of the earth and sand. acts on the circumferential surface of the pile as a single supporting force. The circumferential area of this first cylinder A is defined as S.

On the other hand, the supporting force in this casting method is calculated from the effective circumferential area (approximately 0.8S) obtained by subtracting the basic spinning area of the spiral protrusions D from the circumferential area S of the first cylinder A, and the adhesion force and friction of the earth and sand. The force not only acts on the peripheral surface of the pile as the first supporting force, but also acts on the second cylinder B that connects the peaks of the spiral protrusions D (see Figure 4).
The shear strength τ of the shear plane of the ground along the circumferential surface of the pile acts on the ridge D integrally protruding from the pile as a second supporting force.

The diameter of the second cylinder B is usually designed to be 1.1 to 1.2 times the diameter of the first cylinder A.

Generally, shear strength τ (kg/cm2) is expressed by the following equation (1).

τ=Ptanφ+C……(1) P: Pressure acting perpendicularly to the shear plane (kg/cm2φ: Internal friction angle of soil tanφ: Coefficient of friction C: Adhesive force (kg/cm2) First, let us consider sandy ground. The strength of the frictional force f of the first cylinder A system is determined in relation to the friction coefficient μA between the concrete surface of the pile and the earth and sand, and the external pressure P against the first cylinder A. The maximum value of the friction coefficient μA is The internal friction angle of the sand, which determines the shear strength in the second cylinder B, is approximately 28 in the case of circular granular sand with a loose and uniform sand structure.
Therefore, the friction coefficient μB is 0.53, which is considered to be almost equal to μA of the first cylinder. From the above, only in the worst case where the sandy ground is loose and the sand particles form a uniform circle, the shear strength τ in the second cylinder is the same as the concrete circumference of the sand particles in the first cylinder A. However, since the adhesive force of the earth and sand is slightly added to the shear strength, the shear strength τ does not become smaller than the circumferential friction force f.

Next, let's consider the sticky ground. The cohesive force C of clayey soil is
Since it is said that the shear strength is approximately equal to the shear strength when the pressure P is zero, from the above, the minimum shear strength of cohesive soil is the adhesive strength C. To summarize the above, only when the soil condition is the worst, whether it is sandy ground or clay ground, the shear strength τ of the ground of the second cylindrical system will be equal to the concrete surrounding surface of the earth and sand of the first cylindrical system. Although it may be equal to the applied frictional force f and adhesive force C, it will never be less than these.

From the above, when the local soil is in the worst condition, the following two equations hold true.

τ≧C τ≧f In this way, if the shear strength τ, circumferential surface friction force f, and circumferential surface adhesive force C can be independently equal for each soil type, the magnitude of each supporting force is It is proportional to its area of action.

1. Supporting force action area (first cylinder) SM in conventional construction method
2 2. Bearing force action area of this method a. (Part of the first cylinder)
0.85M2 b. (Second cylinder 1.15-1.25M2 total 1.95
~2SM2 As a result of the above, the sandy soil along the circumference of the second cylinder B loosens,
In addition, the second cylindrical system has a low friction coefficient of around 0.5, the internal pressure P acting perpendicularly to the second cylinder B is low, and the shear strength of the cohesive soil is almost equal to its adhesive strength. The vertical bearing capacity of piles using this construction method under the worst-case conditions for shear strength is 1.9 to 2 times the total bearing capacity of piles using conventional construction methods.

This is an amazing increase in bearing capacity, but this construction method is unique in that the bearing capacity consists of multiple elements, and this multiple bearing capacity is received by both the peripheral surface of the pile and the ridges D of the pile. This is rather a natural result given the structure of the bearing capacity, and moreover, this magnification is the minimum comparative magnification.

Therefore, if the sandy soil in the area B of the second cylinder becomes compact, the sand particles become angular and the internal friction angle becomes large, and if measures are taken to further increase the internal pressure P, the circumferential support force in this method will further increase. It is clear that it will have a huge supporting capacity.

To express the above features simply, a cast-in-place pile a with a diameter of 1 meter installed using this construction method has the lowest circumferential bearing capacity than a cast-in-place pile with a diameter of 2 meters installed using the conventional construction method b. It is equivalent to the circumferential support force of . Moreover, the weight of a itself is
It is reduced to about 1/4 of the weight of pile b, and the effective bearing capacity (deducting its own weight from the total bearing capacity) is further increased, and the costs of creating underground holes, disposal of residual soil, concrete materials, and other miscellaneous costs are significantly reduced. The economic effect of reducing this is significant.

The above analysis is a truly noteworthy analysis showing the characteristics of this construction method, and the constituent requirements of the soil cement and the original ground in the PHC pile construction method described above are the same as those of the concrete column of the cast-in-place pile and the original ground. The circumferential surface bearing capacity of PHC piles installed using this method is the same as that of PHC piles installed using conventional methods, except for sludge-like ground where it is impossible to create heading grooves. It is twice or more than twice the supporting force. Therefore, in this construction method, we used high-concentration cement milk to strengthen the soil cement in order to increase its strength. In addition, in the pre-boring method for PHC piles, it is desirable to apply vibration force to the piles during the installation process to make the soil cement that has flowed into the ridges D denser. In addition, even if it is a cast-in-place pile, the PH
Whether it is C piles or steel pipe piles, the bearing capacity of piles installed using this construction method far exceeds the bearing capacity of piles installed using conventional construction methods, so the horizontal bearing capacity of piles that corresponds to this strong bearing capacity is However, an easy method for construction is to connect an SC pile with a diameter larger than the outside diameter of the shaft to the top of the PHC pile. In addition, if an anchor reinforcing bar is welded to the circumference of the lower end above the cast-in-place pile and an SC pile with the hollow tip closed is sunk above the cast-in-place pile, the SC pile will float due to the buoyancy of the concrete. When earth and sand or concrete is introduced into the hollow part and balanced, the SC pile can be easily connected above the cast-in-place pile without using a large-scale position maintenance device for the SC pile.

Next, the second difference between piles installed using this method and the conventional method is the difference in tip bearing capacity. In the conventional construction method, an expanded root is built in the hard ground of the supporting layer. In other words, it is a bell-shaped, expanded root with a conical tip. Therefore, although the contact area with the supporting ground becomes larger, the circumferential supporting force of the hard ground against the conical surface cannot be expected at all. In the conventional construction method, this is an enlarged underground hole H with a parallel part shown in Figure 10 in the supporting layer of hard ground.
.

However, the hole wall T loosened during excavation, and there was no way to repair it, so they ignored the supporting force of the circumferential surface and focused solely on expanding the ground contact area at the tip.

On the other hand, with this construction method, even if the tip area is expanded unnecessarily, it is impossible to compact the contact surface of the supporting ground as in the percussion construction method, and rather, the underground hole H is enlarged. The circumferential area of the parallel part of the hole is expanded, and the height of the expanded parallel part is increased, and this hole wall T is compacted and solidified using a special method when forming the forging groove, and this solidified hole wall T is Create multi-stage ridges D that overhang the ground, and apply the shear strength τ, circumferential friction force f, and circumferential adhesive force C of the hard supporting ground to the circumferential surface of the enlarged parallel part of the pile and the multi-stage ridges D. At the same time, the compressive resistance force of the enlarged ground contact area is applied to the pile tip to increase the multifaceted tip bearing capacity.

Now, from a different perspective, we will explain the comparison of the lateral contact surfaces of the piles of the two construction methods, including numerical values.

(1) If the tip structure of the conventional construction method is designed following the current example of an expanded root, assuming that the diameter of the shaft is 1.2M, the diameter of the conical base will be R = 1.2M x 1.5 = 1. 8M Therefore, the base area A is A=0.92π≒2.54M2 (2) Example of tip design of this casting method A. Shaft diameter 1.2M b. Expanded underground hole diameter 1.5M c. Expanded parallel spinning height 5.0M d. Projection height 0.1M E. Convex pitch 0.5M f. Number of ridge pitches: 9 pitches (1) From the above design conditions, the ground contact area of 1 pitch of ridges is 1.6π x 0.1 = 0.5M2 (2) The ground contact area of all ridges is 0.5 x 9 = 4. 5M2 (3) The bottom area of the expanded underground hole is 0.752π = 1.76M2 (4) The total ground contact area B is B = 4.5 + 1.76 = 6.26M2 (3) Comparison of ground contact area This method / conventional method = B /A=6.26/2.54=2.
46 According to the above calculation results, in this construction method, the axial force due to the upper load is distributed over a wide area that is 2.46 times the ground contact area of the conventional construction method. Moreover, the ground of the protrusion D has a high load-bearing capacity because it is compressed when the pressure groove is created. In other words, the deformation (amount of subsidence) of the ground due to the axial force is small. In addition, the pressure per unit area of the conventional construction method is 2.46 times the pressure per unit area of the present construction method, and the structure of this contact surface is loose, so the amount of initial settlement is likely to be particularly large. expensive. Taking the above into consideration, this construction method has a load-bearing capacity that is at least twice the tip support capacity of the conventional construction method.

Furthermore, a characteristic of the influence of axial force is that the greater the bearing capacity of the ground acting on the circumferential surface up to the support layer, the less the axial force acting on the pile tip.

Therefore, for piles manufactured by this method that have a large circumferential bearing capacity, the axial load burden of the tip bearing capacity is significantly reduced compared to the burden of the tip bearing capacity of piles of the conventional method. At the construction site, even if the creation of expanded roots is omitted with this construction method, it is expected that there will be no major difference in the bearing capacity.

Therefore, as explained in the case of prefabricated piles, the cases where it is absolutely necessary to create expanded roots are during the following construction.

(1) Construction sites where the soft layer continues up to the supporting layer (2) Construction sites where ground subsidence is expected (3) Construction sites where soil liquefaction is expected or higher use means.

Although the present construction method has been described above according to Examples 1, 2, and 3, the apparatus and operating means used in each example can be applied to other examples. In addition, the forging groove used in each example moves the reamer in the vertical direction at the same time as the reamer is rotated, so the forging groove becomes a continuous helical forging groove, and the protrusion D formed in this groove is also continuous. However, if the axial movement of the reamer is stopped for a certain period of time and the reamer is rotated, a single annular groove is created in the hole wall T. Next, the rotation of the reamer is stopped, the reamer is moved in the axial direction by a certain distance, and then the reamer is rotated.

By repeating the above operations, multi-stage annular grooves are created in the hole wall T at regular intervals. At this time, the cutting edge of the reamer is 13.
is shaped like a square pyramid so that it can move forward by pushing the earth and sand in the left and right and up and down directions. In this construction method, both the above-mentioned multi-stage groove and the above-mentioned spiral passage can be used.

As previously analyzed in detail, the circumferential bearing capacity and tip bearing capacity of the piles installed using this method are significantly greater than those of conventional piles, and small-diameter piles often outperform conventional large-diameter piles. can support the superstructure on behalf of the superstructure. Therefore,
In the case of cast-in-place piles, the amount of concrete required for the piles installed using this construction method should be at most about 1/3 of the amount of concrete used for piles using the conventional construction method, which is sufficient for design purposes. On the other hand, the concrete used must be carefully selected. Due to the requirement that this concrete must flow into the heading groove, the maximum size of the aggregate must be limited to 20 mm or less, and high-strength concrete made with the highest level of current concrete mixing technology must be used. do. Another effective method is to use high-strength mortar instead of high-strength concrete. Furthermore, the shape and dimensions of the protrusions D and the pitch and interval of the protrusions are not limited to the shapes, dimensions, pitches, etc. shown in the examples.
The design can be freely modified.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. Fig. 1 is an underground view showing the tip of the excavation device in the pre-boring method, Fig. 2 is a slope view of the warped bit, and Fig. 3 is a diagram showing the tip of the digging device in the pre-boring method. Figure 4 is a cross-sectional view of the vicinity of the reamer attached to the bit, Figure 4 is a cross-sectional view of a model of a cement column built underground, Figure 5 is a slope view of the tip of the reamer, and Figure 6 is a pre-bored underground view. Figure 7 is a bottom view of the closing plate with a reamer attached, Figure 8 is a diagram of the underground structure showing the pile in the supporting layer and the advance operation of the excavation device, Figure 9 is a diagram of the excavation equipment showing the operating status of the pile and reamer in the supporting layer;
Fig. 10 is a schematic diagram of the structure of an enlarged excavation device for creating an enlarged underground hole at the tip of a cast-in-place pile, and Fig. 11 is a diagram of the opening/closing mechanism of a large reamer attached to a tremie pipe. In the drawing, code H...underground hole, H. ...Enlarged underground hole, T...hole wall, K...drilling equipment, g...groove pressed into the hole wall, D...projection extending over the original ground, a...stick pile, 1...rotating shaft, 1. ... Suction shaft, 3... Warped surface bit, 5... Drilling tip, 6... Light end bit, 7... Stirring blade, 8... Round bar that presses the hole wall, 9...
Injection hole, 10...Bearing fitting, 11...Shaft, 12...Reamer, 1
3... Reamer cutting edge, 14... Triangular pyramidal surface of cutting edge, 17... PH
C pile frame, 18... Reinforcement band, 19... Fixing plate, 20...
Spacer, 21... Closing plate, 25... Drilling bit, 28... Stirring blade that can be opened and closed, 33... Pressed steel plate that suppresses the hole wall, 38 and 39... Expanding blade, 40... Pin holder, 41... Pin, 42
...Hytenuse bit for cutting the hole wall, 43...Tremy tube, 44...Wall guard for suppressing the hole wall, 45...Locking metal fitting.

Claims (1)

[Scope of Claims] A reamer of a rotary body, which has a reamer for creating a groove in the hole wall attached to a reamer base connected to the tip of the rotary body, is rotated in a slow-hardening fluid in an underground hole. At the same time, the axial movement of the rotating body is performed intermittently or continuously in this slow-hardening fluid, and the hole wall of the underground hole is
The reamer, which is linked to the rotating shaft, cuts a required groove, and the slow-hardening fluid is automatically flowed into the groove, and after the slow-hardening fluid has hardened, the required protruding stripes are formed in the original ground of the hole wall. A fixed casting method for foundation piles, which is characterized by creating hardened columns protruding from the outside in underground holes.