JP2005232694A - Composite pile foundation and its constructing method as well as rotational press-in steel pipe pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a rotational press-in steel pipe pile foundation is easy to be displaced, while utilizing its advantages of a high lift supporting force and high constructing efficiency. <P>SOLUTION: The composite pile foundation K comprises a cylindrical pile body 51 at the front end of which the rotational press-in steel pipe pile 5 having a spiral blade 52 is composed with a cast-in-place concrete pile 10, the rotational press-in steel pipe pile 5 pressed in the ground by the rotation of the pile body 51, the cast-in-place concrete pile 10 shorter than the pile body 51 for covering the head and the outer peripheral face of the pile body 51, and a fixing member 53 provided on the outer peripheral face of the pile body 51 for integrating the pile body 51 with the cast-in-place concrete pile 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a composite pile foundation obtained by synthesizing a rotary press-fit steel pipe pile having a spiral wing at the tip of a pile body and a cast-in-place concrete pile, a construction method thereof, and a rotary press-fit steel pipe pile. In particular, the present invention relates to a technique that can be effectively used when constructing a pile foundation such as a power transmission tower in the ground.

  The foundation of a steel tower that supports overhead power transmission lines, wireless antennas, etc. has a characteristic that a large lifting force acts. For this reason, cast-in-place pile foundations that can effectively withstand this lifting force and single pile foundations using rotary press-fit steel pipe pile foundations have recently been widely used.

  As a cast-in-place pile foundation, a full-rotation all-casing pile method as shown in FIG. 1 is often used. The all-casing pile is inserted into the underground G while connecting a plurality of steel pipes 1 called casings in series as bolts as earth retaining when excavating the piles, and the earth and sand inside the steel pipe 1 is removed by a soil removal jig 2 called a grab hammer. After the soil is removed, the reinforcing bars are inserted and the casing 1 is pulled out while placing the concrete to form a pile body.

  In particular, when using the full-rotation type all-casing pile driving machine 3 shown in the figure, by attaching hard teeth (not shown) to the tip of the casing 1 and rotating the casing 1 360 degrees or more indefinitely, A general excavator having a high lifting support capacity can easily excavate even hard ground such as gravel, which is difficult to excavate, and thus a pile body with a high support capacity can be formed.

  On the other hand, as shown in FIGS. 2 and 3, the rotary press-fit steel pipe pile 5 is a pile having a spiral blade 52 having a diameter of about 1.5 times the tip of a steel pipe (pile body) 51 having a diameter of 300 to 1600 mm. It is. Since the tip is spread by the spiral blade 52, it is possible to obtain a large support force with a small pile diameter. The construction in the case of a steel pipe of 500 mm or more takes a system in which the pile is penetrated into the ground by the spiral blade 52 by applying a rotational torque while pushing it in about several tens tons using the all-rotation type all casing pile driving machine 3. .

At that time, in order to hold the steel pipe (pile main body) 51, a detachable special jig (see FIG. 4) 6 is attached to the pile driving machine 3 so that a large rotational torque can be applied to the pile. . In addition, the steel pipe pile 5 may corrode, and in particular, the head of the pile is corroded with a large amount of oxygen supply. Therefore, the steel pipe pile 5 is made to wind the pile head with concrete for corrosion prevention.
JP 2001-146744 A

  A rotary press-fit steel pipe pile foundation used as a single pile foundation is generally superior to cast-in-place piles in that it has less influence on the surroundings during construction, such as workability, vibration, and noise. However, the power transmission tower has a truss structure, and it is necessary to reduce the horizontal displacement in order to suppress the occurrence of secondary stress on the steel tower member due to the relative displacement of the foundation, and to that end it is necessary to increase the diameter of the steel pipe. is there. When the diameter of the steel pipe is increased, the material cost increases and the construction machine becomes large, so that there is a problem that the economic efficiency is deteriorated.

Here, the horizontal displacement generated in the pile is caused by the horizontal force and moment acting on the pile from the steel tower. FIG. 5 shows an example of displacement and moment generated in the pile. The ground is generally soft near the surface and deep and hard in the ground. Therefore, the horizontal displacement generated in the pile is maximum near the ground surface as shown in FIG. On the other hand, the moment generated in the pile is often maximum around several meters from the ground surface, as shown in FIG. Therefore, the horizontal displacement of the pile is determined by the magnitude of the moment of the pile part near several meters from the ground surface, the rigidity of the pile (pile diameter and amount of steel), and the rigidity of the ground. Not really.

  The subject of this invention is providing the technique which can compensate the fault that it is easy to carry out horizontal displacement, making use of the high lifting support force and favorable workability which are the advantages of a rotary press-fit steel pipe pile foundation.

In order to solve the above-mentioned problems, the present invention employs the following means.
The present invention is a composite pile foundation in which a rotary press-fit steel pipe pile having a spiral wing at the tip of a cylindrical pile body and a cast-in-place concrete pile are combined, and the press-fit is a press-fitted into the ground by rotating the pile body A steel pipe pile, a cast-in-place concrete pile that is provided so as to cover the head and outer peripheral surface of the pile body, and is provided on the outer peripheral surface of the pile body, the pile body and the cast-in-place concrete pile; And a fixing member for integrating them.

  According to the present invention, by placing a cast-in-place concrete pile covering the head and outer peripheral surface of the pile body of the rotary press-fit steel pipe pile, the ground rigidity of the front surface of the pile is increased, and the deformation rigidity of the pile is increased accordingly. Thus, the pile head displacement can be reduced. Moreover, since a pile head displacement becomes small, the diameter of a steel pipe can be made small and economical efficiency can be improved. A fixing member demonstrates the effect | action which joins a pile main body and a cast-in-place concrete pile integrally, and makes it a pile foundation of a composite structure.

  Here, when considering the depth and size of the cast-in-place concrete pile with respect to the rotary press-fit steel pipe pile, the economical effect becomes greater as the diameter becomes shallower and smaller. However, from the viewpoint of making the pile head displacement as small as possible, it is desirable to set the diameter of the cast-in-place concrete pile large. The depth depends mainly on the ground rigidity, but it is desirable to set the depth shallow from the viewpoint of economy. These are determined by the magnitude of the moment acting on the pile, the rigidity of the pile itself, the rigidity of the ground, and the like. That is, the present invention is an idea to cope with by reinforcing a pile head portion from the ground surface to a predetermined depth required by a cast-in-place concrete pile, unlike the existing idea that gives a large rigidity over the entire length of the pile. .

  The fixing member preferably extends in a spiral shape at the same pitch as the spiral blade along the outer peripheral surface of the pile body. In this way, the fixing member can be provided in advance before the rotary press-fit steel pipe pile is attached to the pile driving machine. Because, when holding the pile body part of the rotary press-fit steel pipe pile, the function of the spiral gap (spiral groove) provided in the holding jig of the pile driving machine to prevent the interference with the spiral blade is also applied to the fixing member. This is because it can be applied. Thereby, after press-fitting the steel pipe pile or while press-fitting the steel pipe pile, the work of providing the fixing member on the outer peripheral surface of the pile main body is unnecessary, and the workability can be further improved.

  The fixing member is a deformed reinforcing bar and is preferably welded to the outer peripheral surface of the pile body. In this way, the deformed reinforcing bar exhibits high fixing performance due to its good adhesion function with concrete. Furthermore, the operation | work which winds around the pile main body which consists of a steel pipe helically, and a welding operation can also be performed easily.

  The length of the cast-in-place concrete pile is preferably set within 2/3 of the length of the pile body. Although it can also be set to 2/3 or more, in that case, it often results in an undesirable result in terms of workability and economy. As for the depth of cast-in-place concrete piles, the function is low at a portion deeper than the required depth, and the cost effectiveness is significantly reduced.

  Moreover, as for the said cast-in-place concrete pile, it is desirable that the front-end | tip has reached the depth of at least 3 m from the ground surface. This is because, in general ground, the moment generated in the pile is often the maximum near a few meters from the ground surface.

  Moreover, it is desirable that the diameter of the cast-in-place concrete pile is in a range of 1.5 to 5 times the diameter of the pile body. In general ground, it is set to about 2 to 2.5 times, but in the ground having high rigidity, it works effectively even about 1.5 times. On the ground with low rigidity, it may be set to about 5 times. If it is 1.5 times or less, the thickness of the concrete layer surrounding the pile main body is not sufficiently ensured, which may cause a crack or the like. If it is 5 times or more, the amount of concrete used becomes too large, which is not preferable in terms of economy.

  On the other hand, the present invention is a rotary press-fit steel pipe pile having a spiral blade at the tip of a cylindrical pile body, and spirally at the same pitch as the spiral blade along the outer peripheral surface of the pile body. An extending fixing member for concrete is provided.

  According to the present invention, since the fixing member extending spirally at the same pitch as the spiral blade is provided on the outer peripheral surface of the pile main body, the rotary press-fit steel pipe pile can be directly mounted on the pile driving machine and rotary press-fitted. . Because, when gripping the pile body part of the rotary press-fit steel pipe pile, the function of the spiral groove provided in the gripping jig of the pile driving machine can be applied to the fixing member in order to prevent interference with the spiral blade. It is. Thereby, the work which provides a fixing member in the outer peripheral surface of a pile main body can be improved after press-fitting a steel pipe pile, or press-fitting a steel pipe pile, and workability can be improved.

  The fixing member is a deformed reinforcing bar and is preferably welded to the outer peripheral surface of the pile body. In this way, the deformed reinforcing bar exhibits high fixing performance due to its good adhesion function with concrete. Furthermore, the operation | work which winds around the pile main body which consists of a steel pipe helically, and a welding operation can also be performed easily.

  The present invention is a method for constructing a composite pile foundation in which a rotary press-fit steel pipe pile having a spiral wing and a cast-in-place concrete pile having a spiral wing at the tip of the pile body, and a cylindrical casing having a larger diameter than the rotary press-fit steel pipe pile A step of excavating the inside of the casing, a step of excavating the inside of the casing, a step of placing the rotary press-fit steel pipe pile in the center of the casing, and press-fitting the rotary press-fit steel pipe pile into the ground, While inserting the steel rod between the outer peripheral surface of the pile main body and the casing inner peripheral surface of the rotary press-fit steel pipe pile, and placing concrete between the outer peripheral surface of the pile main body and the casing inner peripheral surface, And a step of pulling out the casing.

  Further, in the present invention, before the rotary press-fit steel pipe pile is press-fitted into the ground, a fixing member for integrating with the cast-in-place concrete pile is provided on the outer peripheral surface of the pile body of the rotary press-fit steel pipe pile. It is desirable to keep it.

  Further, the fixing member is a reinforcing bar that spirally extends at the same pitch as the spiral blade along the outer peripheral surface of the rotary press-fit steel pipe pile, and the rotary press-fit steel pipe pile is mounted before the rotary press-fit steel pipe pile is attached to the pile driving machine. It is desirable to weld it.

  Further, in the step of penetrating the casing into the ground, using a full-rotation all-casing pile driver that penetrates into the ground while rotating the casing, the step of press-fitting the rotary press-fit steel pipe pile into the ground, It is desirable to hold the rotary press-fit steel pipe pile with a holding jig attached to the pile driving machine.

ADVANTAGE OF THE INVENTION According to this invention, the fault that it is easy to carry out horizontal displacement can be supplemented, making use of the high lifting support force and favorable workability which are the advantages of a rotary press-fit steel pipe pile foundation.
Further, according to the rotary press-fit steel pipe pile of the present invention, since the fixing member extending spirally at the same pitch as the spiral blade is provided on the outer peripheral surface of the pile body, the rotary press-fit steel pipe pile is directly attached to the pile driving machine. Can be press-fitted.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 6 is a partial cross-sectional view showing an embodiment in which the present invention is applied to a composite pile foundation for a steel tower. FIG. 7 is a sectional view showing the structure of the composite pile foundation. 8-14 is process drawing which shows the construction example of a synthetic pile foundation.

<Structure of composite pile foundation>
The composite pile foundation K is a composite structure of a rotary press-fit steel pipe pile 5 having a spiral blade 52 at the tip of a cylindrical pile body 51 and a cast-in-place concrete pile 10. That is, the synthetic pile foundation K is provided so as to cover the rotary press-fit steel pipe pile 5 that is press-fitted into the ground by rotating the pile body 51, and the head and outer peripheral surface of the pile body 51. The cast-in-place concrete pile 10 and a fixing member 53 that is provided on the outer peripheral surface of the pile main body 51 and integrates the pile main body 51 and the cast-in-place concrete pile 10 are provided. An upper member 7 such as a steel tower base is fixed to the pile head portion of the composite pile foundation K.

  The fixing member 53 extends spirally at the same pitch as the spiral blade 52 along the outer peripheral surface of the pile body 51. In this embodiment, as shown in FIG. 7, a deformed reinforcing bar is used for the fixing member 53. The fixing member 53 made of the deformed reinforcing bar is fixed to the outer peripheral surface of the pile main body 51 by welding. The reason for using deformed reinforcing bars is that they can exhibit high fixing performance with a good adhesion function with concrete, and the work of winding the deformed reinforcing bars spirally around the pile body 51 made of steel pipe and welding work can be easily performed. It takes into consideration what can be done.

  Therefore, as long as it is a member that exhibits the same function as the deformed reinforcing bar, not only the deformed reinforcing bar, but also, for example, a strip-shaped steel material, an anchor gibber, or the like can be used. The welding length (welded location) of the fixing member (deformed bar) 53 to the pile main body 51 is not necessarily required to be welded over the entire length, and may be welded at intervals if sufficient in strength. In that case, it is desirable to weld intermittently and evenly.

  The reason why the fixing member 53 is provided spirally at the same pitch as the spiral blade 52 along the outer peripheral surface of the pile main body 51 is that the fixing member 53 is provided in advance before the rotary press-fit steel pipe pile 5 is attached to the pile driving machine 3. It is because it can be kept. This is because the fixing member 53 has the function of the spiral groove 61 provided in the gripping jig 6 of the pile driving machine 3 in order to prevent interference with the spiral blade 52 when gripping the pile body 51 portion of the rotary press-fit steel pipe pile 5. It is also possible to apply. Thereby, the work which provides the fixing member 53 in the outer peripheral surface of the pile main body 51 becomes unnecessary after press-fitting of the steel pipe pile 5, or press-fitting the steel pipe pile 5, and workability can be improved further.

  The length Lp1 of the cast-in-place concrete pile 10 depends on the length of the pile body 51, but is set within 2/3 of the length of the pile body 51. Although it can also be set to 2/3 or more, in that case, it often results in an undesirable result in terms of workability and economy. As for the depth of cast-in-place concrete piles, the function is low at a portion deeper than the required depth, and the cost effectiveness is significantly reduced.

Moreover, about this cast-in-place concrete pile 10, the front-end | tip has reached the depth of at least 3 m from the ground surface. This is because, in general ground, the moment generated in the pile is often the maximum near a few meters from the ground surface. Therefore, as a particularly preferable length Lp1 of the cast-in-place concrete pile 10, as shown in FIG. 6, it is a length that can cover a pile head portion reaching a depth of at least 3 m from the ground surface in the pile body 51. .

  Moreover, the diameter of the cast-in-place concrete pile 10 is set in a range of 1.5 to 5 times the diameter of the pile body 51. In general ground, it is set to about 2 to 2.5 times, but in the ground having high rigidity, it works effectively even about 1.5 times. On the ground with low rigidity, it may be set to about 5 times. If it is 1.5 times or less, the thickness of the concrete layer surrounding the pile main body 51 is not sufficiently secured, which may cause a crack. If it is 5 times or more, the amount of concrete used becomes too large, which is not preferable in terms of economy.

  Next, a specific design method of a helical fixing member (hereinafter referred to as a spiral rib) 53 for integrating the rotary press-fit steel pipe pile 5 and the cast-in-place concrete pile 10 will be described below. (1) The meaning of each variable is defined as shown in Table 1 (see FIG. 7).

(2) Load a. Load direction Since the main reinforcement of cast-in-place concrete pile 10 responds to bending, the cast-in-place concrete pile 10 and steel pipe (pile body 51) are kept attached to the axial load of the pile. Do the design.
b. Load at the time of lifting The load to be considered at the time of lifting is the sum of the weight of the cast-in-place concrete pile and the friction force between the cast-in-place concrete pile and the ground.
c. Load during compression The load to be considered during compression is the sum of the frictional force between the cast-in-place concrete pile and the ground and the ground reaction force at the bottom of the cast-in-place concrete pile. However, the bottom ground reaction force of cast-in-place concrete piles is the maximum ground reaction force multiplied by the bottom area.

(3) Study on split fracture a. Concept In a structure in which reinforced concrete is wound in a cylindrical shape around a steel pipe with spiral ribs, when a load is applied in the vertical direction, the concrete splits and breaks in the axial direction. In order to prevent this, the following consideration is made at the time of lifting and compression, and the contact height Lrh of the spiral rib necessary for fixing satisfying both of the two conditions is set.
b. Examination for lifting The Lrh that satisfies the following formula shall be secured.

c. Study for compression Lrh that satisfies the following equation (Equation 2) shall be secured.

(3) Study on bearing strength of spiral rib The following formula (Formula 3) shall be satisfied.

(4) Examination of weld strength of spiral rib The spiral rib is a deformed steel rod. Welding shall be single-sided flare welding, and the required amount shall be applied intermittently over the entire length, and the following formula (Formula 4) shall be satisfied.

(5) Structural details a. Material used for spiral ribs To prevent slippage along the spiral when an axial force is applied to the steel pipe, the spiral ribs are made of deformed steel bars.
b. Spiral Rib Pitch Rib has a spiral shape and the pitch matches the pitch of the spiral blade of the rotary press-fit steel pipe pile.
c. Installation position of the spiral rib The leading position of the spiral rib is from the final concrete finish surface.
The position is deeper than (D1-D2) / 2-eh.
The deepest position of the spiral rib is from the bottom of the cast-in-place concrete pile,
(D1-D2) / 2 · tan 40 ° + the position shallower than eh.
d. Welding length of spiral rib Welding of spiral rib shall be performed to 1/3 or more of the total length of spiral rib, and shall be performed intermittently and evenly.

<Construction method>
Next, the construction method of the synthetic pile foundation K is demonstrated.
First, the casing 1 is excavated from the vicinity of the ground surface to several tens to several tens of meters as required for design. In this step, as shown in FIG. 1, a full rotation all casing pile driver 3 is used. Specifically, the casing 1 is caused to penetrate into the underground G while being rotated by the pile driving machine 3, and the earth and sand in the casing 1 is discharged by the grab hammer 2. In that case, it carries out, connecting the casing 1 as needed. After that, the upper end of the casing 1 is cut off near the ground surface G1.

  Next, as shown in FIG. 8, a scaffold 20 is formed by placing a plate or the like on the upper part of the casing 1, and a holding jig 6 for holding the rotary press-fit steel pipe pile 5 is attached to the pile driving machine 3. The gripping jig 6 has the structure shown in FIGS. 4 and 9 and includes a plurality of divided support blocks 61. A spiral gap (spiral groove) 62 is provided on the inner peripheral surface of each support block 61 so that the pile body 51 of the rotary press-fit steel pipe pile 5 can be gripped without interfering with the spiral blade 52. Yes.

  Next, after removing the scaffold 20, as shown in FIGS. 9 and 10, the rotary press-fit steel pipe pile 5 is inserted while being rotated in accordance with the spiral gap 62 of the gripping jig 6. The rotary press-fit steel pipe pile 5 is previously provided with a fixing member 53 in which a deformed reinforcing bar is welded to a necessary portion of the outer peripheral surface of the pile main body 51 at a factory or construction site.

  Next, when the rotary press-fit steel pipe pile 5 reaches the bottom of excavation in the casing 1, as shown in FIG. 11, the pile body 51 using the holding jig 6 is press-fitted while being rotated so as to screw the pile body 51. To do. Here, a spiral fixing member 53 for integration is provided at a portion that is a composite pile of the cast-in-place concrete pile 10 and the rotary press-fit steel pipe pile 5 near the ground surface. Therefore, when gripping the portion where the fixing member 53 exists with the gripping jig 6, the protrusion of the fixing member 53 is gripped so as to coincide with the gap (spiral groove) 62 of the gripping jig 6, and the steel pipe pile The fixing member 53 is prevented from being damaged during the press-fitting.

  When the tip of the rotary press-fit steel pipe pile 5 reaches a predetermined depth, as shown in FIG. 12, the rotary press-fit steel pipe pile 5 is made to reach a predetermined depth by using a barb 21. Reference numeral 22 denotes a joint between the last piece 21 and the rotary press-fit steel pipe pile 5.

  Next, as shown in FIG. 13, the gripping jig for removing the bar 21 and forming a scaffold as shown in FIG. 8 by placing a plate or the like on the upper portion of the casing 1 and gripping the rotary press-fit steel pipe pile 5. Remove 6. Further, the head 23 of the pile body 51 is covered with a lid 23 for water stop, and the casing 1 is added to the upper part so that the entire casing 1 is slowly pulled out.

  Next, as shown in FIG. 13, a reinforcing bar 24 is inserted into the casing 1 corresponding to the area of the cast-in-place concrete pile 10. Then, while placing the concrete 26 from the concrete inlet 25a using the tremy tube 25, the casing 1 is slowly lifted so that the reinforcing bar 24 does not rise together.

  At that time, the concrete 26 is placed so that the slime 27 floating on the upper surface of the concrete 26 placement surface is higher than the ground surface G1. As shown in FIG. 14, a pothole 28 is previously provided around the ground surface, and slime is removed by allowing concrete containing slime to flow to the pottery when the casing 1 is all pulled out. After the concrete 26 is hardened, a composite pile foundation K of the rotary press-fit steel pipe pile 5 and the cast-in-place concrete pile 10 is formed.

  Note that the measures shown in FIGS. 15 and 16 may be adopted so that the reinforcing bar 24 does not rise together with the casing 1. In the example shown in FIGS. 15 (a) and 15 (b), one end of the holding member 55 processed with a reinforcing bar or the like is welded to the outer peripheral surface of the rotary press-fit steel pipe pile 5, and the other end is used as the hoop or main reinforcing bar of the reinforcing bar 24. It is a method of covering or welding. Here, the welding on the steel pipe side may be either up or down.

In the example shown in FIGS. 16A and 16B, the intermediate portion of a holding member 56 such as a square pipe or a single pipe pipe is spot-welded to the top end of the rotary press-fit steel pipe pile 5, and both ends thereof are reinforced. It covers 24 hoops and the like (covers from above). Note that both ends of the holding member 56 can be spot-welded to the reinforcing bar 24. However, when removing the holding member 56 after construction, it is desirable that both ends of the holding member 56 are not spot welded to the reinforcing bar 24.

When such a composite pile foundation and its construction method were adopted, it was found that the deformation of the composite pile foundation K can be suppressed to a fraction of that of the case of a rotary press-fit steel pipe pile alone. As a result, it was found that the foundation was established even with a conventional steel pipe diameter of about ½. The detailed reason is as follows.
(1) Pile head displacement was reduced by placing cast-in-place concrete piles at the top, increasing ground rigidity on the front of the pile and increasing deformation rigidity of the pile.
(2) Since the pile head displacement is reduced, the diameter of the steel pipe can be reduced, and the economy is improved.
(3) Since the machine can be used efficiently by simultaneously performing the cast-in-place concrete pile construction and the rotary press-fit steel pipe pile construction with the full-rotation all-casing pile driving machine, the increase in construction cost is Suppressed.
(4) By integrating cast-in-place concrete piles and rotary press-fit steel pipe piles with helical ribs (fixing members) made of deformed reinforcing bars attached to the outer periphery of the steel pipe, the helical ribs are welded before construction of the steel pipe piles. The construction speed was increased and the quality control of the spiral ribs was facilitated. (5) By providing extra space in the length of the spiral rib, cast-in-place concrete piles and rotary press-fit steel pipe piles are integrated even if there are some construction errors, so they can flexibly handle construction errors. The workability was improved.
(6) Fixing by means of spiral ribs can be used not only for joining with cast-in-place concrete piles but also for joining with reinforced concrete slabs.

  It can be applied to the foundations of steel towers that support overhead power transmission lines and wireless antennas, other pile foundations, and their construction techniques.

It is the excavation construction drawing of the cast-in-place pile by a full rotation type all casing pile driver. It is an external view which shows the front-end | tip of a rotation press fit steel pipe pile. It is a conceptual diagram which shows the placement method of a rotation press fit steel pipe pile. It is an external view of the holding jig of a rotary press-fit steel pipe pile. It is explanatory drawing which shows distribution of the displacement and moment of a pile in pile head freedom. It is the schematic of the synthetic pile foundation which concerns on this invention. It is the schematic which shows the fixing member of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention. It is process drawing which shows the construction example of the synthetic pile foundation which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Grab hammer 20 Scaffolding 21 Lasting 22 Seam 23 Lid 24 Reinforcing rod 25 Tremmy pipe 25a Slot 26 Concrete 27 Slime 28 Kamiba 3 Full-rotation all-casing pile driving machine 5 Rotary press-fit steel pipe pile 51 Pile body 52 Spiral wing 53 Fixation Member (spiral rib)
55, 56 Holding member 6 Holding jig 61 Support block 62 Spiral gap (spiral groove)
7 Upper member 10 Cast-in-place concrete pile K Composite pile foundation G Underground G1 Ground surface

Claims (12)

A composite pile foundation that combines a rotary press-fit steel pipe pile with a spiral wing at the tip of the pile body and a cast-in-place concrete pile,
Rotating press-fit steel pipe pile that is pressed into the ground by rotating the pile body,
A cast-in-place concrete pile that is provided to cover the head and outer peripheral surface of the pile body, and shorter than the pile body,
A fixing member provided on the outer peripheral surface of the pile body, and integrating the pile body and the cast-in-place concrete pile;
Synthetic pile foundation with.   2. The composite pile foundation according to claim 1, wherein the fixing member extends spirally at the same pitch as the spiral blade along the outer peripheral surface of the pile body.   The composite pile foundation according to claim 2, wherein the fixing member is a deformed reinforcing bar and is welded to an outer peripheral surface of the pile body.   The composite pile foundation according to claim 1, wherein a length of the cast-in-place concrete pile is within 2/3 of a length of the pile body.   The composite pile foundation according to claim 1, wherein a tip of the cast-in-place concrete pile reaches a depth of at least 3 m from the ground surface.   The composite pile foundation according to claim 1, wherein a diameter of the cast-in-place concrete pile is in a range of 1.5 to 5 times a diameter of the pile body. A rotary press-fit steel pipe pile with a spiral wing at the tip of the pile body,
A rotary press-fit steel pipe pile in which a fixing member for concrete is provided on the outer peripheral surface of the pile body along the outer peripheral surface so as to extend spirally at the same pitch as the spiral blade.   The rotary press-fit steel pipe pile according to claim 7, wherein the fixing member is a deformed reinforcing bar and is welded to an outer peripheral surface of the pile body. It is a construction method of a composite pile foundation in which a rotary press-fit steel pipe pile having a spiral wing at the tip of the pile body and a cast-in-place concrete pile are synthesized,
A step of penetrating a cylindrical casing having a larger diameter than the rotary press-fit steel pipe pile into the ground,
Drilling in the casing;
Placing the rotary press-fit steel pipe pile in the center of the casing, press-fitting into the ground while rotating the rotary press-fit steel pipe pile;
Inserting a reinforcing bar between the outer peripheral surface of the rotary press-fit steel pipe pile and the inner peripheral surface of the casing;
A step of pulling out the casing while placing concrete between an outer peripheral surface of the rotary press-fit steel pipe pile and an inner peripheral surface of the casing;
Method of composite pile foundation including   The composite pile according to claim 9, wherein a fixing member for integrating with the cast-in-place concrete pile is provided on an outer peripheral surface of the rotary press-fit steel pipe pile before press-fitting the rotary press-fit steel pipe pile into the ground. Foundation construction method. The fixing member is a reinforcing bar that spirally extends at the same pitch as the spiral blade along the outer peripheral surface of the rotary press-fit steel pipe pile, and is welded to the rotary press-fit steel pipe pile before mounting the rotary press-fit steel pipe pile on the pile driving machine. The construction method of the synthetic pile foundation of Claim 10 to keep.   The step of penetrating the casing into the ground is performed using a full-rotation all-casing pile driving machine that penetrates into the ground while rotating the casing, and the step of pressing the rotary press-fit steel pipe pile into the ground is performed using the pile driving The construction method of the synthetic pile foundation of any one of Claims 9-11 performed by holding the said rotary press-fit steel pipe pile with the holding jig with which the machine was mounted | worn.

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