JPH0458522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to be used] The present invention relates to a pile in which a part of an existing concrete pile is reinforced and a method for forming the same, and particularly relates to a pile that can withstand large lateral forces.

[Conventional technology and problems]

In general, foundation piles installed in structures are bent by compressive force in the vertical direction, that is, in the axial direction of the pile, in order to support the weight of the structure, and by inertia force in the horizontal direction of the structure during an earthquake.

Of these, concrete itself has strong compressive strength against vertical loads, and ordinary hollow reinforced concrete piles or PC concrete piles are sufficient.
In addition, these supporting forces can be sufficiently increased by increasing the cross-sectional area, and in reality, the supporting force of the supporting ground is weaker than that of the well-known concrete pile, so there is no need to particularly increase the vertical force.

On the other hand, the horizontal bearing capacity is complicated by the connection method between the pile head and the superstructure, and the properties of the ground, so it is impossible to accurately predict which part of the pile will receive a particularly large lateral force. Curve A in the graph in Figure 6, which shows the bending moment distribution of pile _A1 when the pile cap is firmly fixed to the superstructure, shows the curve A when the pile cap is firmly fixed to the superstructure. stake
It has been confirmed both theoretically and from the results of horizontal loading tests that the bending moment distribution map of B ₁ is approximately similar to curve B.
A large lateral force acts on the R ₁ part of A ₁ , and the R ₂ part of Pile B ₁ , so each design guidance organization uses a unified formula to calculate the safety of the pile. It is said that it may be considered.

Therefore, there are two main types of so-called bending moment piles that make concrete piles able to withstand this bending moment.One of them is to increase the amount of reinforcing bars in reinforced concrete piles.
The other is a steel pipe concrete composite pile with steel pipes on the outside.

However, in the former case, when increasing the number of prestressing steel bars or ordinary reinforcing bars used as reinforcing bars, the prestressing steel bars require end plates to be fixed to the piles at both ends in order to apply prestress to them. The structure is complex, the stress introduction device requires a special jig, the stress introduction takes time, and the manufacturing cost is extremely high due to the large number of material costs and manufacturing steps.
In addition, the amount of prestress becomes very large and creep tends to occur in the concrete layer, so it is necessary to increase the amount of cement in order to increase the strength of the concrete layer. In addition, due to the large prestress, the compressive strength of the concrete layer itself decreases, making it extremely vulnerable to impact.Also, when cutting the pile head and trimming it, if there are a large number of PC steel bars, the concrete layer will be cut. It is also time-consuming, and cracks are likely to occur in the concrete layer along these PC steel bars.

Also, since it is troublesome to fix both ends of PC steel bars, so-called PRC piles with ordinary reinforcing bars have been developed, but the reinforcing bars are quite thick (20 to 40 mm).
It must be located in the center of the concrete layer for rust prevention, and the spacing between adjacent reinforcing bars becomes close, which makes the relationship with the size of coarse aggregate in the concrete unfavorable, and the distance between reinforcing bars The tensile force in the circumferential direction of the pile becomes weak, and longitudinal cracks are likely to occur when the pile is subjected to pressure from the inside, such as in the case of the pile circumferential tensile force generated during impact, and in the case of the hollow excavation method, so it is not necessary in reality. Quantity of rebar cannot be used.

There are also known steel pipe composite piles in which the outside of a hollow concrete pile is restrained by steel pipes with a thickness of 4.5 mm or more, without using reinforcing bars (for example, Japanese Patent Application Laid-Open No. 50-86108
(No.), steel pipes are extremely expensive compared to reinforcing bars at the time of this application, and increasing the wall thickness only in the necessary parts along the length of the pile will further increase processing costs and ultimately result in a higher grade. Thick steel pipe is used for the entire length, and generally steel pipes with a thickness of 4.5 mm or more are used, which wastes material. The steel pipe concrete composite pile using steel pipe of the above thickness at the time of filing of this case is not compatible with other PC concrete piles,
The price is two to four times that of ordinary reinforced concrete piles.

In addition, as piles for bridges and port structures that are subject to large lateral forces, a method of assembling double inner and outer steel pipes on site and filling the middle with cement concrete or mortar as a solidification filler was developed.
47964, the inner and outer pipes are steel pipes,
Extremely expensive, radial protrusions are buried in the inner and outer pipes to receive bending strength, and steel pipes with a smaller diameter are buried and filled with concrete to integrate the inner and outer pipes. However, the dowels provided near the inner steel pipe and the ribs are less efficient as a tensile material against bending, and the efficiency of steel material usage is poor. The compression and bending strength is obtained from steel pipes, and a large amount of steel is used.In particular, this technology would not be possible without the use of inner steel pipes, and would be extremely expensive.

In addition, with concrete mortar cast on site, there is a risk that the adhesion of both the inner and outer steel pipes will be insufficient, and the outer diameter will also tend to become too large, which not only increases the number of constituent materials but also increases the diameter of the piles. If it becomes too much, the pile construction cost will increase.

〔the purpose〕

The purpose of this invention is to reinforce existing concrete piles such as ordinary reinforced concrete piles and PC concrete piles.The manufacturing method is simple, and the product pile is a pile that can withstand large lateral forces. It is to be.

[Means to solve the problem]

This invention involves arranging a required number of 6 or more axial reinforcements of shorter length at equal angular intervals around the axis in the generatrix direction at required locations along the length of the precast concrete pile. The pile is surrounded by a jacket pipe made of a type of thin-walled steel pipe or reinforced synthetic resin pipe with a diameter sufficient to surround these shaft reinforcements, and all gaps between the prefabricated concrete pile and the jacket pipe are filled with an inflatable pipe. The problem was solved by creating an externally reinforced concrete pile characterized by forming a concrete layer filled with fresh concrete and expanded as it hardened.

Another invention provides a pre-cast concrete pile with a thin-walled steel pipe or reinforced synthetic resin pipe having a shorter length and an inner diameter that creates a gap between the outer circumferential surface of the pre-cast concrete pile and which allows the insertion of shaft reinforcement as described later. A mantle pipe made of one of the following is fitted concentrically to a required position on the outside of the precast concrete pile, and a required number of six or more axial reinforcements are installed between the prefabricated concrete pile and the mantle pipe. Arranged at equal intervals around the axes of the pile and the mantle tube, both ends of the mantle tube are closed with ring-shaped end plates, and the pipe expands into all the gaps from a partial notch in one end plate. The problem was solved by a method for forming an externally reinforced concrete pile, which is characterized by filling fresh concrete and then expanding it as the concrete hardens to form a concrete layer.

The invention will now be described on the basis of exemplary embodiments shown in the drawings.

[Description of component parts]

Reference numeral 10 indicates a ready-made concrete pile, which is not particularly limited as long as it is one of the following types: a reinforced concrete pile containing normal reinforcing bars or prestressed steel bars, a prestressed concrete pile, or a thin-walled steel pipe concrete composite pile. Although the length is not particularly limited, a long one of 10 to 15 m is preferable.

Reference numeral 11 is a jacket pipe made of a thin-walled steel pipe or a reinforced synthetic resin pipe, and its thickness is sufficient as long as it has sufficient strength to restrain the expansion of the expandable ready-mixed concrete, which will be described later, and is thick enough to withstand corrosion after pile construction. in,
In the case of thin-walled steel pipes, 2 to 6 mm, preferably 2 to 3
A seamless or axially seamed steel pipe with a thickness of about 4 to 10 mm is used, and in the case of reinforced synthetic resin, a fiber-filled material that can withstand tensile force, such as FRP, is used. The length of this mantle pipe 11 is shorter than the precast concrete pile 10, and the length is 6 to 6.
The inner diameter is preferably about 10 m, and the inner diameter is such that the shaft reinforcement 13 can be just inserted between the precast concrete pile 10 and the mantle pipe 11.

As the shaft reinforcement 13, a flat steel plate 13a is used,
The cross section used in the embodiment has a width b of 30 to 60 mm and a thickness t of 6 to 16 mm. The shape of the most axial reinforcement 13 is not limited to the above-mentioned shape, and the cross section may be circular or irregularly shaped, such as ordinary reinforcing steel, high-strength reinforcing steel, etc., which have the strength to withstand the tensile force in the axial direction due to bending of the pile.
There is no particular limitation as long as it is included in JISG-3112 (1964) and has the same strength as this.

In the illustrated example, the length of each axial muscle is the mantle tube 11.
Although the lengths are shown to be the same, they may be slightly shorter, and the invention is the same even if two or more types of long and short lengths are distributed over the entire circumference.

[Embodiments of the manufacturing method and embodiments of the product]

It is the outside of the existing concrete pile 10,
When the pile is constructed, it fits in a position that covers the part R ₁ or R ₂ where the most lateral force acts (see Figure 6),
For example, a flat steel plate 13a is placed between the existing concrete pile 10 and the mantle pipe 11, and its wide side is the mantle pipe 1.
A required number of six or more rods 13 are inserted at equal intervals in the circumferential direction of the mantle tube 11, and each axis rod 13 is brought into contact with the inner circumferential surface of the mantle tube 11, and a donut-shaped end plate 1 is inserted.
4, both ends of the mantle pipe 11 are closed, the whole is tilted, and all the gaps between the precast concrete pile 10 and the mantle pipe 11 are filled with expandable ready-mixed concrete from the notch of the lower end plate 14, The concrete is hardened and expanded by an appropriate curing method to form a concrete layer 15 between the prefabricated concrete pile 10 and the mantle pipe 11, and the mantle pipe 11 and the group of shaft reinforcements 13 are integrated on the outside of the prefabricated concrete pile 10. A pile of the present invention is manufactured which is coupled to a.

The expandable ready-mixed concrete used in the above method is one mixed with an expanding agent during mixing, or expandable cement, and the expanding agent is heated at 1600℃.
Magnesia powder, dolomide,
Calcium oxide is suitable, and hardened concrete with an expansion rate of about 1 to 5% is used.
The strength of the concrete layer 15 of this invention is 600
It is preferable to have a compressive strength of about 900 Kg/cm ² .
Therefore, the curing method is a natural curing method, a normal pressure steam curing method, an autoclave curing method, etc. depending on the expanding agent.

As shown in FIGS. 3 and 5, the inner diameter of the jacket pipe 11 is such that the shaft reinforcement 13 is exactly the same as that of the precast concrete pile 1.
In general, it is good if the outside diameter is sufficient to allow insertion between the concrete pile 10 and the pre-cast concrete pile 10, but for piles that are subject to larger bending forces, the gap between the shaft reinforcement 13 and the pre-cast concrete pile 10 is larger than the diameter or thickness of the shaft reinforcement 13. The invention of this product is the same even if it has an inner diameter that allows the diameter of the pipe (see Fig. 4).

[How to use the invention of a product]

When using the pile of this invention, a hole large enough to insert the mantle pipe 11 is formed in the precast concrete pile 10.
Either excavate the length of the part in advance and erect the pile of the present invention, or if the diameter of the precast concrete pile is large, use the hollow method to erect the pile of the present invention so that its tip is in the support layer. In the case where the upper ends of the outer pipe 11 and the pre-cast concrete pile 10 are aligned as in the embodiment shown in FIG. 13a and precast concrete pile 10
The reinforcing bars 16 of the sections are exposed together to connect them to the superstructure.

In the embodiment shown in FIG. 2, only 10 pre-cast concrete piles are subjected to the same pile cap treatment as conventionally known.

[Effects of invention of products]

In the present invention that can be constructed and used as described above, the portion R ₁ or R ₂ having a large bending moment distribution on the outside of the precast concrete pile 10 is thick and completely integrated as described above, and the boundary surface thereof Also, due to the adhesion force of the concrete layer 15 and the pressing force due to expansion, it does not slip and can sufficiently withstand lateral forces caused by earthquakes, etc. In particular, the tensile force due to the bending force applied to the pile of this invention is mainly It is received by the axial muscle 13, and the axial muscle 1
Since each of the three groups is provided in contact with the inner circumferential surface 12 of the mantle tube 11, its effective radius is large.

Therefore, the diameter of the mantle pipe 11 does not need to be so large, and the strength of the mantle pipe 11 can sufficiently restrain the expansion force of the concrete layer 15, which expands while hardening, and can withstand corrosion during the service life of the pile. Thickness is sufficient; in the case of thin-walled steel pipes, 2 to 6 mm
Preferably, a thickness of 2 to 3 mm is sufficient (corrosion thickness of steel pipes is said to be 1 mm/60 years), and even in the case of reinforced synthetic resin pipes, it may be about 3 to 10 mm.

In particular, the mantle tube 11 isolates the axial muscles 13 from the outside air and groundwater, preventing them from corroding.

In addition, in this invention, since the mantle tube 11 is a thin-walled steel pipe or a reinforced synthetic resin pipe, it is easy to cut, and even when it is necessary to cut the shaft muscles 13, by cutting the mantle tube 11, these shaft muscles 13 can be removed. Parts are exposed to the outside, making it easy to cut when necessary and easy to process the pile cap.

Since the required number of axial reinforcements is 6 or more and they are arranged at equal angular intervals, there is no directionality in bending strength.

[Effects of embodiments of invention of product]

When flat steel plates 13a are used as the axial reinforcement 13 and their wide surfaces extend in the circumferential direction of the mantle tube 11, the effective radius of the axial reinforcement 13 relative to the outer diameter of the mantle tube 11 should be maximized. I can do it.

Others using regular reinforcing bars or reinforcing bars with a circular cross section or different diameters as specified in JISG-3112 (1964) are easily available and relatively inexpensive.

The jacket tube 11 made of a thin-walled steel tube has a sturdy outer circumferential surface and is easy to handle, and the jacket tube 11 has sufficient bending strength until this part corrodes.
Since the shaft reinforcement 13 is designed to receive tensile force, even if the mantle tube 11 becomes completely corroded after a long period of time after construction, the bending strength will not immediately decrease. Of course, when the thickness is greater than the corrosion allowance, the remaining mantle tube 11 serves as an effective tensile member.

In the case where a reinforced synthetic resin tube is used as the mantle tube 11, it does not corrode even for a long period longer than the service life of the upper structure, and maintains the desired bending strength for a long period of time.

[Effects of method invention]

The method of the present invention uses a precast concrete pile 10, fits the mantle pipe 11 on the outside of the pile, inserts the shaft reinforcement 13 between them as described above, and then fills the pile with expandable ready-mixed concrete. The mantle pipe 11 serves as a kind of outer formwork when pouring the expandable ready-mixed concrete. Since this is a filling method, the concrete layer 15 expands to form concrete piles 10, mantles 11, and shaft reinforcements 13.
are completely integrated and tightly integrated, and even if the pile is subjected to lateral force, no slipping will occur on these contact surfaces, making it possible to manufacture a strong pile.

In addition, the number, material, surface shape, length, etc. of the shaft reinforcements 13 can be freely selected according to the predicted bending moment distribution, and can be manufactured to suit the ground and superstructure.

In addition, the thickness and material of the mantle tube 11 can be freely selected depending on the purpose, providing an extremely high degree of freedom in design.
Relatively inexpensive piles can be manufactured and are extremely practical.

[Effects of method embodiments]

The outer tube 11 can also be subjected to tensile force due to bending, especially when the concrete layer 15 during manufacturing
It has the effect of sufficiently restraining the expansion of.

In the method of using reinforced synthetic resin as the mantle tube 11, it is possible to manufacture a pile that can maintain strength for a long period of time, and is lightweight and easy to handle.

[Brief explanation of the drawing]

The drawings show things related to this invention,
Fig. 1 is a partially vertical front view of a typical embodiment of the invention, Fig. 2 is an external side view of another embodiment, and Figs. 3, 4, and 5 are cross-sectional plan views, respectively. , FIG. 6 is a bending moment distribution diagram. In the figure, 10... precast concrete pile, 11...
Mantle pipe, 13... shaft bar, 15... concrete layer.

Claims (1)

[Scope of Claims] 1. A required number of 6 or more axial reinforcements of shorter length than this are placed at equal angular intervals around the axis in the generatrix direction at the required locations in the length direction of the precast concrete pile. These shaft reinforcements are provided in the concrete pile, and are surrounded by a jacket pipe made of a type of thin-walled steel pipe or reinforced synthetic resin pipe with a diameter sufficient to surround these shaft reinforcements, and all gaps between the precast concrete pile and the jacket pipe are An externally reinforced concrete pile characterized by having a concrete layer filled with expandable ready-mixed concrete and expanded as it hardens. 2. The externally reinforced concrete pile according to claim 1, wherein the prefabricated concrete pile is one of a reinforced concrete pile and a steel pipe concrete composite pile. 3. The externally reinforced concrete pile according to claim 1, wherein the shaft reinforcements are made of flat steel plates, and their wide surfaces are in the circumferential direction of the mantle tube. 4. Claim 1, characterized in that the axial reinforcement has one of circular or irregular cross-sections, and is one of ordinary reinforcing bars and high-strength reinforcing bars.
Externally reinforced concrete piles as described in section. 5. The mantle tube is seamless with a wall thickness of 2 to 6 mm,
The externally reinforced concrete pile according to claim 1, which is a type of axially jointed steel pipe. 6 A type of thin-walled steel pipe or reinforced synthetic resin pipe that is shorter than this length and has an inner diameter that creates a gap between the outer circumferential surface of the precast concrete pile and which allows the insertion of shaft reinforcement, which will be described later. A mantle pipe made of the above-mentioned concrete pile is fitted concentrically to a required location on the outside of the pre-cast concrete pile, and between the pre-cast concrete pile and the mantle pipe, a required number of six or more axial reinforcements are connected to the pre-cast concrete pile. , arranged at equal intervals around these axes in the gaps between the mantle tubes, both ends of the mantle tubes are closed with ring-shaped end plates, and inflatable growth is introduced into all the gaps from a partial notch in one end plate. A method for forming an externally reinforced concrete pile, which is characterized by filling concrete and then expanding it as the concrete hardens to form a concrete layer.