JPWO2015011777A1 - Composite pile - Google Patents

Abstract

A composite that can prevent the breakage of the boundary between the concrete part with the outer shell steel pipe and the prestressed concrete part at the time of manufacturing, and effectively obtain both the performance of the concrete pile with the outer shell steel pipe (SC pile) and the prestressed concrete pile (PC pile). It is a pile. The composite pile 1 is a hollow tube composed of an SC part 2 and a PC part 3. In the SC unit 2, there is a fixing unit 4 in the axial direction from the boundary with the PC unit 3. An annular end plate 10 is provided at both ends. A PC steel material 7 is arranged in an annular shape over the entire length in the axial direction at a substantially center of the pipe wall made of high-strength concrete 6, and a spiral bar 8 is arranged over the entire length of the PC steel material 7. ing. The steel pipe 5 of the SC part 2 is tapered such that the end of the steel pipe 5 connected to the PC part 3 is inclined from the pipe inner surface side toward the pipe outer surface side. One or more ring bars 8 are attached in the circumferential direction to the inner surface of the steel pipe near the end of the steel pipe 5 of the SC section 2 having a tapered tube thickness.

Description

  The present invention relates to a composite pile having both the performance of a concrete pile with a shell steel pipe and a prestressed concrete pile, which is suitable for construction on soft ground, construction requiring construction efficiency, and the like.

  In pile foundation construction, various types of ready-made piles are used depending on the construction purpose. The types of ready-made piles are hollow concrete piles, concrete piles with shell steel pipes (SC piles), reinforced concrete piles (RC piles), prestressed concrete piles (PC piles), prestressed reinforced concrete piles (PRC piles), prestressed high strength concrete piles (PHC piles), expanded prestressed concrete piles (ST piles), prestressed concrete piles with joints (joint piles), and the like are known.

  Of these, concrete piles with outer steel pipes (SC piles), prestressed concrete piles (PC piles), prestressed high strength concrete piles (PHC piles), expanded prestressed concrete piles (ST piles) And prestressed concrete piles with joints (joint piles).

Concrete piles with outer steel pipes (SC piles) are manufactured by injecting concrete into the hollow part of the steel pipe and centrifugally compacting it. Even if large bending deformation occurs, the concrete prevents local buckling of the steel pipe and the concrete is steel pipe. It has very large toughness because it is constrained by and is mainly used as the upper pile of pile foundation. There is no particular limitation as long as high strength concrete having a design standard strength of 50 N / mm ² or more is formed by centrifugal molding. Moreover, the yield point or proof stress of a steel pipe is generally 235 N / mm ² or more.

Prestressed concrete piles (PC piles) are a type of centrifugally formed concrete piles. After placing a rebar cage with helical bars attached to a PC steel material in a steel cylindrical formwork, the design standard strength is 50 N / mm ² or more. It is a product with a circular shape manufactured by centrifugal compaction. In the axial direction, compressive stress (prestress) is applied to the concrete by the PC steel material by a pretension method. Examples of the amount of prestress include A type (4 N / mm ² ), B type (8 N / mm ² ), and C type (10 N / mm ² ). Since compressive stress is given to the pile, it is a pile that is superior in bending characteristics to a reinforced concrete pile (RC pile) and strong against impact during driving.

Prestressed high-strength concrete piles (PHC piles) are manufactured using high-strength concrete with a design standard strength of 80 N / mm ² or more in the above-mentioned PC piles. It is difficult to use, and is used as a foundation pile for medium- and high-rise buildings and ground countermeasure buildings.

  Further, the expanded-diameter prestressed concrete pile (ST pile) is a product in which one end of the PC pile is enlarged in order to increase the supporting force. The outer diameter of the enlarged portion is 5 to 20 cm larger than the diameter of the pile body, and the length of the enlarged portion is generally twice the outer diameter of the enlarged portion. When the ST pile is used, the tip supporting force is increased, so that a large horizontal force is applied to the upper pile.

  Moreover, the prestressed concrete pile (node pile) with a node is a pile which provided the processus | protrusion to the said PC pile at the predetermined | prescribed space | interval in order to enlarge a surrounding surface friction force and a support force. A node spacing of 1 m and a node outer diameter of a pile body diameter +150 to 200 mm are generally used. If the pile is used, the peripheral frictional force and the supporting force increase, so that a large horizontal force is applied to the upper pile.

  It is also known that two types of the above-mentioned pre-made piles are connected or integrated to be used as a composite pile. For example, in pile foundation construction in a place where a large horizontal force acts on soft ground, the above concrete pile with outer shell steel pipe (SC pile) and prestressed high strength concrete pile (PHC pile), steel pipe pile and concrete pile (PC pile, PHC piles) are connected and used.

  Several patents relating to these composite piles have been filed. For example, Patent Document 1 discloses a pile in which a steel pipe pile and an SC pile are joined, and one or more stages at the lower part of the inner peripheral surface of the steel pipe constituting the SC pile. What provided the protrusion of this is disclosed.

  Further, in Patent Document 2, a concrete composite part with an outer shell steel pipe is integrally formed so as to form a concrete composite part with an outer shell steel pipe on one end side and the concrete part up to the other end. A steel pipe / reinforced concrete composite pile in which axial reinforcing bars are arranged over the entire length or a part and the entire length of the concrete part, and spiral bars are provided in the concrete part is disclosed.

Japanese Unexamined Patent Publication No. 2007-285019 Japanese Unexamined Patent Publication No. 2012-057443

  As disclosed in Patent Document 1, there is a composite pile in which two types of ready-made piles such as steel pipe piles and SC piles are connected by connecting fittings or welding, but connecting these two types of piles is troublesome to connect. Cost and high cost.

  Moreover, as disclosed in Patent Document 2, although there is a composite pile in which a concrete pile with an outer shell steel pipe (SC pile) and a reinforced concrete pile (RC pile) are integrated, it is described in paragraph 0014 of Patent Document 2. Thus, when trying to obtain an integrated pile of pre-stressed piles (PC piles) such as SC piles and PHC piles, as a manufacturing problem, the tension plate must be fixed during demolding after hardening of the concrete. When the prestress is introduced by canceling the above, there is a problem that the axial force is concentrated on the boundary portion between the SC portion and the PHC portion to cause cracks, and the boundary portion is easily damaged.

  In order to cope with this problem, in Japanese Patent Application Laid-Open No. H10-228707, the spiral bars are disposed only in the concrete part, but it is not sufficient to dispose the spiral bars only in the concrete part as described above. In addition, if the fixing portion is long, the concrete portion with the outer shell steel pipe in which the concrete and the steel pipe do not behave integrally is increased or the cost is increased.

  The present invention has been made in view of the above problems, and it is difficult for the boundary portion between the concrete portion with the outer shell steel pipe and the prestressed concrete portion to be damaged during production, and the concrete pile with the outer shell steel pipe (SC pile) and the prestressed concrete pile The main purpose is to provide a composite pile in which both performances of (PC pile) can be effectively obtained. Another object is to obtain the above composite pile having a short fixing portion.

  The present invention is a composite pile having the performance of both a concrete pile with a shell steel pipe and a prestressed concrete pile, a concrete portion with a shell steel pipe formed on one end side, and a concrete portion formed from this to the other end. PC steel and spiral bars are arranged over the entire length in the axial direction, and the pipe wall at the end of the steel pipe connected to the concrete part in the concrete part with the outer shell steel pipe is inside the pipe. It is a “composite pile characterized by being tapered from the surface side toward the pipe outer surface side and being tapered”.

  The composite pile of the present invention has a concrete part with an outer shell steel pipe (hereinafter referred to as “SC part”) formed on one end side and a concrete part (hereinafter referred to as “PC part”) formed to the other end. Is a hollow tube formed by integral molding.

  The outer diameter / inner diameter of the SC part (the outer diameter of the steel pipe, the inner diameter of the concrete pipe) and the outer diameter / inner diameter of the PC part (the outer diameter / inner diameter of the concrete pipe) may be the same or different. Moreover, the node may be provided in the PC part like a node pile. End plates are attached to both ends of the composite pile.

The SC section corresponds to a conventional concrete pile with a shell steel pipe (hereinafter referred to as “SC pile”). The steel pipe used for SC part will not be specifically limited if it is used for SC pile. In addition, the concrete pipe formed inside the steel pipe is not particularly limited as long as it is conventionally used, but high-strength concrete with a design standard strength of 50 N / mm ² or more, and further a design standard strength of 80 N / mm ² or more. Those made of high-strength concrete are preferred.

The PC section corresponds to a conventional prestressed concrete pile (hereinafter referred to as “PC pile”). Although it will not specifically limit if the concrete used for the conventional PC pile is centrifugally molded, it is preferable to use a concrete with a design standard strength of 50 N / mm ² or more as concrete, and a high strength with a design standard strength of 80 N / mm ² or more. More preferably, concrete is used. If high-strength concrete with a design standard strength of 80 N / mm ² or more is used, the PC section will be compatible with prestressed high-strength concrete piles (PHC piles), and will have both the strength of both SC and PHC piles. It becomes a durable pile.

  The PC section basically corresponds to the PC pile as described above, but is not necessarily limited to this, and may be made to correspond to the PHC pile using high-strength concrete as described above. It is a broad concept that can be provided with an enlarged diameter portion to correspond to the ST pile, or can be provided with a node to correspond to the joint pile.

  Although the outer diameter of the composite pile of this invention is not specifically limited, Preferably it is 0.3-1.5m. The length of one piece is preferably 4 to 15 m. The length of the SC part is preferably 3 m or more. The SC section is arranged near the ground and on the weak ground top, but if it is less than 3 m, the effect as the SC pile cannot be sufficiently obtained, and the reinforcement on the ground top may be weakened.

  In the composite pile of this invention, PC steel materials are arrange | positioned cyclically | annularly over the full length of the axial direction. Since prestress is applied not only to the PC part but also to the SC part, both the concrete and steel pipes of the SC part, both performance of concrete piles with outer steel pipes (SC piles) and prestressed concrete piles (PC piles) Is effectively obtained. PC steel will not be specifically limited if it is conventionally used for PC pile. Moreover, the arrangement | positioning form of PC steel materials is the same as that of the conventional PC pile.

  Moreover, in the composite pile of this invention, the helix is arrange | positioned over the full length of the axial direction. By doing in this way, the concrete in which the PC steel material arrange | positioned at SC part is thrown away does not fall apart, but the effect that prestress acts efficiently also on the concrete and steel pipe of SC part is acquired.

  The spiral muscle is a normal iron wire or a high-strength spiral muscle, for example, a wire diameter of 3 mm or more for a spiral with an outer diameter of 500 mm or less, a wire diameter of 4 mm or more for a spiral with an outer diameter of 600 mm, and a wire diameter of 5 mm or more for a spiral with an outer diameter of 700 to 1000 mm. It is preferable to do this. The pitch is preferably 110 mm or less. Outside these ranges, the effect as a spiral muscle may not be sufficiently obtained.

  Moreover, in this invention, the pipe | tube wall of the steel pipe end part by the side connected to the said PC part in the said SC part inclines toward the pipe | tube outer surface side from the pipe inner surface side, and is tapering. By doing so, the steel pipe end portion acting force at the time of demolding (when prestress is introduced) is distributed in the axial direction and the pipe inner surface direction by the taper of the steel pipe end portion. For this reason, the force acting on the concrete at the end of the steel pipe is reduced, so that the boundary portion between the SC portion and the PC portion is less likely to be damaged at the time of demolding during manufacture (when prestress is introduced).

  In addition, although the tip of the inclined steel pipe end may be pointed, it is preferable to have a flat surface of about 1 to 3 mm in consideration of safety and workability.

  As described above, the steel pipe is disposed over the entire length in the axial direction, the spiral bars are disposed over the entire length in the axial direction, and the steel pipe is connected to the PC portion in the SC portion. The main object of the present invention can be effectively achieved by forming the end of the tube wall into a tapered shape inclined from the inner surface of the tube toward the outer surface of the tube.

In the composite pile of the present invention, it is further preferable that “the concrete part with the outer shell steel pipe and the concrete of the concrete part are high-strength concrete having a design standard strength of 50 N / mm ² or more”.

By making the concrete used for the concrete part with the outer shell steel pipe and the concrete part (PC part) high-strength concrete with a design standard strength of 50 N / mm ² or more, the boundary part is less likely to be damaged. A high-strength, high-durability pile that combines the performance of both piles and PHC piles can be obtained.

  In the composite pile of the present invention, it is further preferable that “a ring streak is attached to the inner surface of the steel pipe near the end of the steel pipe whose pipe wall is tapered”.

  In general, in a composite pile consisting of an SC section corresponding to an SC pile and a PC section corresponding to a PC pile, about 1 to 1.5 times the pile diameter from the boundary toward the SC section is called a fixing section. It has been broken. This fixing portion is a portion having an effect of transmitting a prestress force at the time of demolding (when prestress is introduced) to the steel pipe by an adhesion force between the concrete and the steel pipe. If the length of the fixing portion is long, the number of SC portions where the concrete and the steel pipe do not move together increases, which is not preferable.

  In the present invention, in order to shorten the length of the fixing portion, a ring line is attached to the inner surface of the steel pipe in the vicinity of the end of the steel pipe of the SC portion having a tapered tube thickness. By doing so, in addition to the adhesion force between the concrete and the steel pipe inside the steel pipe, the prestressing force at the time of demolding (when prestress is introduced) is also transmitted to the steel pipe by the support pressure of the ring reinforcement. The length of the fixing portion can be shortened as compared with the case where it is not provided.

  The ring bars are steel bars, and the cross-sectional shape of the bars can be not only circular but also various shapes such as an ellipse diameter, a quadrangle, and a triangle. The thickness of the ring line is preferably 6 mm or more. If it is less than 6 mm, the effect of dispersing the force acting on the fixing portion may not be sufficiently obtained.

The installation position of the ring line is near the end of the steel pipe of the SC part. The ring bars are installed in the circumferential direction so that the ring is in a direction perpendicular to the axial direction of the SC portion. The number of the ring streaks is not limited to one, but two or three may be installed at intervals of 10 to 20 cm in the axial direction. The method for attaching the inner surface of the steel pipe of the ring wire is not particularly limited. For example, by fastening metal fittings such as welding and bolts.
It is preferable that the composite pile of the present invention further has “the inclination angle θ of the inclination is 30 to 50 °”.

  In the present invention, the tube wall at the end of the steel pipe connected to the PC section in the SC section is tapered from the pipe inner surface side toward the pipe outer surface side, but the inclination angle θ Is preferably 30 to 50 °. If the angle is less than 30 °, the axial force acting on the concrete at the end of the steel pipe is increased, and the boundary portion between the SC portion and the PC portion is likely to be damaged. If the angle exceeds 50 °, the end portion is easily deformed. The “inclination angle θ” referred to in the present invention is an angle formed between a perpendicular line perpendicular to the pile axis direction and an inclined surface.

  The composite pile of the present invention can be suitably used for pile construction such as construction on soft ground and construction where construction efficiency is required.

  In the composite pile comprising the SC portion and the PC portion of the present invention, the PC steel material is disposed over the entire length in the axial direction, and the spiral bars are disposed over the entire length in the axial direction. In this case, the tube wall at the end of the steel pipe connected to the PC portion is tapered so as to be inclined from the inner surface of the tube toward the outer surface of the tube. It is difficult for the boundary portion between the PC portion and the PC portion to break, and both performances of the concrete pile with outer shell steel pipe (SC pile) and the prestressed concrete pile (PC pile) can be obtained effectively.

  Moreover, in the fixing part of the SC part, a composite pile having a short fixing part length can be obtained by attaching a ring line to the inner surface of the steel pipe in the vicinity of the end part of the steel pipe in which the pipe wall is tapered.

It is a side view which shows the outline of the whole in an example of the composite pile of this invention. It is an enlarged view of the part of the boundary part of FIG. It is a figure which shows the dynamic action mechanism in case there is no ring reinforcement in the composite pile of this invention. It is a figure which shows a dynamic action mechanism in case there exists a ring reinforcement in the composite pile of this invention. It is a side view which shows the outline of the whole in the other example different from FIG. 1 of the composite pile of this invention. It is a side view which shows the outline of the whole in the other example different from FIG. 1, FIG. 5 of the composite pile of this invention. It is a side view which shows the example of attachment to the steel pipe inner surface of the ring reinforcement by a fixing metal fitting in the composite pile provided with the ring reinforcement of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below.
FIG. 1 is a side view showing an overall outline of an example of the composite pile 1 of the present invention.

  The composite pile 1 is a hollow tube composed of an SC part 2 and a PC part 3. In the SC unit 2, about 1 m in the axial direction from the boundary with the PC unit 3 is the fixing unit 4. In addition, annular end plates 10 are provided at both ends.

  In this example, the length of the composite pile 1 is 10 m, and the length ratio between the SC part 2 and the PC part 3 is approximately SC part: PC part = 2: 1. This ratio is not limited to this, and can be any ratio as long as the SC section 2 has a length of 3 m or more. If the effect as the SC pile is to be obtained more strongly in relation to the construction ground, the length ratio of the SC part 2 may be increased. The outer diameter of the tube is 100 cm and the inner diameter is 74 cm.

The composite pile 1 is made of a high-strength concrete pipe having a design standard strength of 105 N / mm ² , and the SC portion 2 is covered with a steel pipe 5 having a thickness of 6 mm.

  The steel pipe 5 is tapered such that the end of the steel pipe 5 connected to the PC portion 3 is inclined from the pipe inner surface side toward the pipe outer surface side. The inclination angle θ between the inclined surface and a perpendicular (virtual line) perpendicular to the pile axis direction is preferably 30 to 50 °. In this example, it is 45 °. By doing so, the force acting on the concrete at the end of the steel pipe is dispersed in the direction of the pile axis and the inner surface of the pipe. Therefore, at the time of demolding in manufacturing (when prestress is introduced), the SC section 2 and the PC Damage to the boundary with the part 3 is less likely to occur.

  In this example, the outer diameter / inner diameter of the SC part 2 (the outer diameter of the steel pipe, the inner diameter of the concrete pipe) and the outer diameter / inner diameter of the PC part 3 (the outer diameter / inner diameter of the concrete pipe) are the same.

  In the composite pile 1 of the present invention, a PC steel material 7 is annularly arranged over the entire length in the axial direction at the approximate center of the pipe wall made of high-strength concrete 6. The PC steel material 7 is the same as that conventionally used for PC piles, and is attached to the end plates 10 on both sides. By pre-stressing the SC part by arranging the PC steel material 7 extending not only to the PC part 3 but also to the SC part 2, a higher performance composite pile in which the SC part is reinforced is obtained.

  Moreover, as shown in the figure, a spiral wire 8 is disposed on the outer periphery of the PC steel material 7 over the entire length. In this example, the spiral muscle 8 is a reinforcing bar having a thickness of 5 mm, and the pitch of the muscle is 100 mm. By arranging the spiral bars 8 in this way, the effect that the pre-stress acts reliably on the SC portion can be obtained without being separated by the concrete in which the PC steel material 7 is manufactured.

  Moreover, as shown in the drawing, the tube wall at the end of the steel pipe 5 connected to the PC unit 3 in the SC unit 2 is tapered from the tube inner surface side toward the tube outer surface side. By doing so, the acting force (compression force) at the end of the steel pipe at the time of demolding (when prestress is introduced) is dispersed in the axial direction and the inner surface of the pipe by the taper of the end. Therefore, since the acting force acting on the concrete at the end of the steel pipe is reduced, the boundary portion between the SC portion 2 and the PC portion 3 is not easily damaged at the time of demolding in manufacturing (when prestress is introduced).

  Further, as shown in the figure, one ring bar 9 is attached to the inner surface of the steel pipe in the vicinity of the end of the steel pipe 5 of the SC section 2 having a tapered pipe wall by welding in the circumferential direction. The ring bar 9 is a reinforcing bar having a circular cross section, and its thickness is 6 mm. By providing the ring reinforcement 9, in addition to the adhesive force between the high-strength concrete 6 and the steel pipe 5, the support pressure by the ring reinforcement increases, so that the length of the fixing portion 4 is 40% that of the case where the ring reinforcement 9 is not provided. It can be shortened to about 80%. And by shortening the fixing | fixed part 4, since the SC part from which concrete and a steel pipe do not behave integrally decreases, it becomes a composite pile from which both performance of SC pile and PC pile can be obtained more effectively.

  FIG. 2 is an enlarged view of a boundary portion A in FIG. The inside of a frame is an enlarged view of the taper part of the steel pipe 5 in which the pipe | tube meat became the taper shape.

  As shown in the figure, the tube wall of the steel pipe 5 of the SC part 2 is provided with a taper 11 at the tip in the direction of the PC part 3 and is inclined at an inclination angle θ. The definition of “inclination angle θ” is as described above, and is an angle between the inclined surface (taper 11) and the virtual perpendicular line 15. The inclination angle θ is preferably 30 to 50 °. Further, a ring line 9 is fixed to the inner surface of the steel pipe 5 slightly inside the taper 11 by a welded portion 12.

  In this way, if the pipe wall of the steel pipe 5 is provided with the taper 11 and the ring reinforcement 9 is attached to the inner surface of the steel pipe 5 in the vicinity of the taper 11, the high-strength concrete 6 at the boundary portion A is not easily damaged due to cracks or the like. Since the length of the fixing portion 4 can be shortened, a high-quality and high-performance composite pile 1 can be obtained. The tip of the taper 11 is a flat surface 14 having a width of about 2 mm in consideration of safety and workability.

  FIG. 3 is a diagram showing a mechanical action mechanism when there is no ring reinforcement 9 in the composite pile 1 of the present invention. The inside of a frame is an enlarged view of the taper part of the steel pipe 5 in which the pipe | tube meat became the taper shape.

  In the SC part 2, the adhesive force F between the concrete and the steel pipe is acting in the direction of the arrow. In addition, a compressive force (P) due to prestress is exerted on the PC portion 3 by introducing prestress by the PC steel material 7 in the direction of the arrow.

  Prestress is applied to the steel pipe 5 of the SC section 2 due to the adhesive force (F) between the concrete and the steel pipe. This adhesion force (F) is obtained by multiplying the adhesion stress of the high-strength concrete 6 to the steel pipe 5 by the surface area of the fixing portion 4.

  The compressive force (P) due to the prestress is resisted by the adhesive force (F) between the concrete and the steel pipe, and mechanically, the adhesive force (F) between the concrete and the steel pipe ≦ the compressive force (P) due to the prestress.

  FIG. 4 is a diagram showing a mechanical action mechanism in the case where there is a ring bar 9 in the composite pile 1 of the present invention. The inside of a frame is an enlarged view of the taper part of the steel pipe 5 in which the pipe | tube meat became the taper shape.

  In the SC part 2, the adhesion force (F) between the concrete and the steel pipe and the support pressure (N) of the concrete by the ring reinforcement work in the direction of the arrow. In addition, a compressive force (P) due to prestress is exerted on the PC portion 3 by introducing prestress by the PC steel material 7 in the direction of the arrow.

  The adhesion force (F) is obtained by multiplying the adhesion stress of the high-strength concrete 6 to the steel pipe 5 by the surface area of the fixing portion 4, and the bearing pressure (N) by the ring reinforcement is the high-strength concrete on the axial cross-sectional area of the ring reinforcement 9. 6 multiplied by the bearing strength.

  Resist the compressive force (P) caused by the pre-stress with the adhesion force (F) between the concrete and the steel pipe and the bearing pressure (N) of the concrete with the ring reinforcement, and mechanically the adhesion force between the concrete and the steel pipe (F) + ring The concrete support pressure by the reinforcement (N) ≦ the compressive force (P) by the prestress.

As can be seen by comparing FIG. 3 and FIG. 4, when the ring reinforcement 9 is attached, the support pressure (N) of the concrete by the ring reinforcement 9 acts in addition to the adhesion force (F) between the concrete and the steel pipe. The length 13 of the fixing unit can be shortened. If the length 13 of the fixing unit is shortened, the steel pipe cost of the fixing unit 4 necessary for applying prestress to the SC unit 2 can be saved and the prestress can be reliably applied to the SC unit 2 as well.
FIG. 5 is a side view showing an outline of the whole in another example different from FIG. 1 of the composite pile 1 of the present invention.

  In this example as well, the composite pile 1 is composed of an SC portion 2 and a PC portion 3, but is different from that shown in FIG. 1 in that the PC portion 3 has an enlarged diameter portion 16 corresponding to the ST pile. The configuration and operation mechanism other than the provision of the enlarged diameter portion 16 are the same as those shown in FIG.

  In this example, as shown in the figure, a little less than half of the length of the PC portion 3 is the enlarged diameter portion 16, but this is not a limitation, and the length of the enlarged diameter portion 16 is arbitrarily provided. May be. The outer diameter of the enlarged diameter portion 16 is 10 cm larger than the pile body diameter. The length, outer diameter, and the like of the enlarged diameter portion are determined so as to resist the pile tip load acting on the enlarged diameter portion 16.

By providing the enlarged diameter portion 16 in the PC portion 3 and corresponding to the ST pile, a pile having a high horizontal support force can be obtained. Therefore, this composite pile 1 is a soft ground with a low ground strength where the ground near the ground surface is composed of soft soil rich in fine particles such as clay and silt, organic soil or peat with large gaps, loose sand, etc. Effective for pile foundation construction.
FIG. 6 is a side view showing an outline of the whole in another example different from FIGS. 1 and 5 of the composite pile 1 of the present invention.

  In this example as well, the composite pile 1 is composed of the SC portion 2 and the PC portion 3, but the PC portion 3 is different from that in FIGS. 1 and 5 in that the PC portion 3 has a node 17 corresponding to the node pile. . The configuration and operation mechanism other than the provision of the joint 17 are the same as those shown in FIG.

  In this example, as shown in the drawing, the PC section 3 is provided with two rows of nodes (annular protrusions) 17 at an interval of about 100 cm. The outer diameter of the node 17 is the pile body diameter +150 mm. The method of providing the knot 17 is not limited to this, and a knot having one row or multiple rows of three or more rows is provided, or the knot 17 has a large protrusion so that the outer diameter is the pile body diameter +200 mm. May be. The size of the nodes, the spacing between the nodes, etc. are determined by the pile tip support force.

  By providing the node 17 in the PC unit 3 to correspond to the node pile, a pile having a high peripheral friction force and horizontal support force can be obtained. Therefore, this composite pile 1 is similar to the one having the enlarged-diameter portion 16 in that the ground near the ground surface is soft soil rich in fine particles such as clay and silt, organic soil or peat having a large gap, loose sand It is effective for pile foundation construction on soft ground with low ground strength.

  FIG. 7 is a side view showing an example of attaching the ring reinforcement 9 to the inner surface of the steel pipe 5 by the fixing bracket 18 in the composite pile 1 having the ring reinforcement 9 of the present invention.

As shown in the figure, the ring reinforcement 9 is sandwiched between curved fixtures 18, bolts 19 are inserted into bolt holes that have been drilled in the steel pipe 5 in advance, and fixed with the bolts 19. Four or more fixing brackets 18 are attached in the circumferential direction. The width in the circumferential direction of the fixture 18 is not particularly limited. According to this attachment method, the ring reinforcement 9 can be reliably attached to the inner surface of the steel pipe 5.
Next, the outline of the manufacturing method of the composite pile 1 of this invention shown in FIG. 1 is shown.

  In the case where the ring reinforcement 9 is provided, the ring reinforcement 9 is welded to the steel pipe 5 in advance and attached with a fixing bracket or the like. Next, the rebar cage is manufactured by attaching the helix 8 to the PC steel 7 by the conventional method. The end of the reinforcing bar is attached to the end plate 10 installed in the steel pipe 5. After the steel pipe 5 and the reinforcing steel basket are installed in the formwork and the high-strength concrete 6 is introduced, the PC steel material 7 is tensioned in order to introduce prestress. Thereafter, centrifugal molding and curing are performed by the conventional method for producing a hollow pile. After curing, the pre-stress is introduced by demolding to cause the SC part 2 and the PC part 3 to act.

  When the ring bar 9 is not provided, the steel pipe 5 to which the ring bar 9 is not attached is used. The manufacturing method is the same as that in the case where the ring bars 9 are provided.

  DESCRIPTION OF SYMBOLS 1 ... Composite pile, 2 ... SC part, 3 ... PC part, 4 ... Fixing part, 5 ... Steel pipe, 6 ... High strength concrete, 7 ... PC steel material, 8 ... Spiral reinforcement, 9 ... Ring reinforcement, 10 ... End plate, A ... Boundary part, 11 ... Taper, 12 ... Welding part, 13 ... Fixing part length, 14 ... Plane, 15 ... Virtual perpendicular line, 16 ... Diameter enlarged part, 17 ... Node, 18 ... Fixing bracket, 19 ... Bolt, F: Adhesive force between concrete and steel pipe, P: Compressive force due to prestress, N ... Concrete bearing pressure due to ring reinforcement

Claims (8)

  This is a composite pile that combines the performance of a concrete pile with a shell steel pipe and a prestressed concrete pile, and the concrete part with a shell steel pipe formed on one end and the concrete part formed to the other end are integrated. PC steel material and spiral bars are arranged over the entire length in the axial direction, and the pipe wall of the steel pipe end connected to the concrete part in the concrete part with the outer shell steel pipe is connected to the pipe outer surface from the pipe inner surface side. A composite pile characterized by being tapered toward the side and tapered. 2. The composite pile according to claim 1, wherein the concrete portion with the outer shell steel pipe and the concrete of the concrete portion are high-strength concrete having a design standard strength of 50 N / mm ² or more.   The composite pile according to claim 2, wherein a ring bar is attached to the inner surface of the steel pipe near the end of the steel pipe whose pipe wall is tapered.   The composite pile according to claim 3, wherein the inclination angle θ of the inclination is 30 to 50 °.   The composite pile according to claim 1, wherein a ring bar is attached to the inner surface of the steel pipe near the end of the steel pipe, the pipe wall of which is tapered.   The composite pile according to claim 5, wherein the inclination angle θ of the inclination is 30 to 50 °.   The composite pile according to claim 1, wherein the inclination angle θ of the inclination is 30 to 50 °.   The composite pile according to claim 2, wherein the inclination angle θ of the inclination is 30 to 50 °.

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