JPH0415791Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a concrete pile with an enlarged portion at the bottom, which is buried underground to support structures, etc., and is particularly suitable for use in cold regions. Concerning foundation piles that do not damage the tips of the piles even when driven into the ground with a strong impact force and have a large bearing capacity even in cold regions. It is something.

[Conventional technology]

Conventionally, when burying prefabricated piles underground to support structures, etc., an expanded bulbous concrete section was formed at the bottom of the pile at the construction site to increase the supporting capacity, or an external layer was placed at the bottom of the pile. An attempt was made to increase the bearing capacity by connecting and integrating concrete piles with large diameters (Japanese Utility Model Publication No. 154501/1983).

[The problem that the idea aims to solve]

In order to form an enlarged bulb at the bottom of the pile at the construction site, it is necessary to excavate the bottom of the pile and pour concrete into the excavated area, but in cold regions, the concrete freezes and does not have enough bearing capacity. It has the disadvantage that it may not be possible to obtain the necessary conditions, or in extreme cases, it may be difficult to construct. Further, even if the concrete does not freeze, its bearing capacity is inferior to that obtained by a construction method in which the piles are driven into solid supporting ground.

In addition, as shown in Japanese Utility Model Application Publication No. 54-154501, etc., piles that are integrated by connecting a concrete pile with a large outer diameter to the lower part of the pile are suitable for use in thick peat layers, which are unique to cold regions. If a pile is driven into the ground, where the ground is firm and slopes downward, by applying a strong impact force to the top of the pile, the bottom tip of the pile will be damaged, resulting in insufficient support. We found that.

The present invention solves the drawbacks of these conventional technologies, and even if an enlarged part is formed at the bottom of the concrete pile in advance or the pile is sunk by the impact method in a cold region where the ground condition is poor, it can be used at the time of construction. To provide a concrete pile having a structure in which the enlarged tip of the lower part of the pile is less damaged, and the pressure applied to the enlarged tip from the upper part is surely transmitted to the enlarged tip to surely express a large supporting force.

[Means to solve the problem]

The concrete pile of this invention is concrete pile 5
A concrete-steel pipe composite part having a diameter larger than the outer diameter of the concrete pile 5 is provided below, and the concrete-steel pipe composite part has concrete 1 having a hollow part inside the steel pipe 2. , the concrete 1 and the steel pipe 2 are integrated by the expansion force of the expanding agent, and at least the upper and lower parts of the concrete 1 of the concrete-steel pipe composite part are protected by cross plates 3 and 4 integrated with the steel pipe 2. This is a concrete pile with a concrete steel pipe composite part, which has a concrete steel pipe composite part.

The concrete pile 5 connected to the upper part used in the present invention is a reinforced concrete pile, a prestressed concrete pile, or the like. In order to further increase the supporting strength, it is preferable to use concrete piles with a compressive strength of 800 kg/cm ² or more. Note that this concrete pile 5 is generally hollow in the center.

This concrete pile 5 is made by welding the end plate 7 of the concrete pile 5 and the steel plate 3 of the concrete steel pipe composite part to a concrete steel pipe composite part having an outer diameter larger than that of the concrete pile, for example, as shown in FIG. 8 and are integrally connected.

In addition, the concrete-steel pipe composite part has a concrete part having a hollow part in the steel pipe 2, and the concrete part 1 and the steel pipe 2 are made of expanded material such as magnesium oxide, calcium sulfur aluminate, gypsum lime, etc. They are integrated by the expansion force of the agent. Note that the thickness of the steel pipe 2 of the concrete-steel pipe composite section is sufficient as long as it can withstand deformation due to pressure from above, etc., and a steel pipe of 3 to 20 mm is used depending on its diameter. In addition, the length of the steel pipe needs to be a certain length in order to fully integrate the concrete with the steel pipe 2, but if it is too long, the amount of steel pipe used will increase, which is uneconomical. All you have to do is set it appropriately. Preferably,
It is about 40-70cm.

At least the upper and lower parts of the conacrete 1 of the concrete-steel-pipe composite section are protected by cross plates 3 and 4 that are integrated with the steel pipe 2 by, for example, welding. These steel plates 3 and 4 are used to protect one part of the concrete from external forces that are applied to the concrete steel pipe composite part from above and below. Steel plates with a thickness of 5 to 20 mm are used, and the outer diameters of the steel plates 3 and 4 are designed to protect the concrete from external forces that are applied from above and below. It is preferable that the inner diameter of the steel pipe 2 be larger than the inner diameter of the steel pipe 2 for the purpose of protecting the steel pipe 2. The outer diameter of the concrete steel pipe composite part is
In order to increase the bearing capacity, the diameter should be set appropriately so that it is larger than the outer diameter of the concrete pile. Preferably, the composite portion is approximately 5 to 10 cm larger than the concrete pile.

Further, it is preferable that the compressive strength of the concrete section 1 of the concrete-steel pipe composite section is equal to or higher than the compressive strength of the upper concrete pile 5, and therefore, it is preferable that the compressive strength is 800 Kg/cm ² or more. Such high compressive strength concrete 1
This can be achieved, for example, by autoclaving a concrete-steel pipe composite.

When manufacturing such a concrete-steel pipe composite part, concrete containing an expanding agent is formed inside a long steel pipe using a centrifugal force forming method, and the concrete is integrated with the steel pipe by the expansion action during curing. , this may be cut to an appropriate length and the upper and lower steel plates may be integrated into it.

[Effect]

In the concrete-steel-pipe composite part connected to the lower part of the pile of the present invention, there is a concrete 1 having a hollow part inside the steel pipe 2, and the concrete 1 and the steel pipe 2 are integrated by the expansion force of the expansion agent. Therefore, when a bending force greater than the yield strength of the steel pipe 2 is applied to this composite part, the composite part exhibits an effect of resisting the bending force more strongly than when concrete is present in the steel pipe at the end.

Furthermore, the concrete-steel pipe composite section of the present invention has a structure in which steel plates 3 and 4 integrated with the steel pipe 2 are present at least at the upper and lower parts of the concrete 1 of the composite section, so that the bending force of the concrete 1 is reduced. In addition, when sinking piles using the driving method to increase bearing capacity, the impact force applied to the top end of the upper pile can be applied to the concrete 1, which has a strong compressive force, without damaging the concrete 1. can be transmitted, and the concrete 1 is protected from being damaged in the ground.

In particular, when installing piles using the driving method in geological formations typical of cold regions, where a thick layer of peat is deposited with an extremely low N value, and a hard layer beneath it is often sloped, When the tip of the pile reaches the interface between the supporting layer and the stratum above it, a large shearing force and bending force are applied to the enlarged portion of the pile tip at the moment of impact. However, the concrete-steel pipe composite part connected to the lower part of the pile of the present invention having the above-mentioned structure does not break and can reliably transmit the pressure applied from the upper part of the pile to the composite part during an impact. Supporting capacity can be reliably expressed. Therefore, according to the pile of the present invention, it is possible to obtain a large bearing capacity in cold regions without using the method of pouring concrete to form a bulbous part at a construction site, where construction is often difficult in cold regions. I can do it.

In addition, when the concrete-steel pipe composite section is sunk using the pouring method, the lower part of the concrete-steel pipe composite section is sunk into the supporting ground;
A part of the upper part of this complex is often exposed in a stratum different from the supporting layer, such as a layer with a small N value, and when an earthquake occurs, sliding occurs at the boundary between strata with different properties. A large shearing force is applied to the buried pile. In this case as well, the use of the concrete-steel pipe composite section with the above-mentioned structure can provide great resistance.

〔Example〕

Example 1 A steel pipe with an outer diameter of 40 cm, a wall thickness of 4.5 mm, and a length of 5 m was placed in a formwork with end plates, and a slurry of concrete mixed with magnesium oxide was applied to the pipe under the action of centrifugal force until the diameter of the hollow part was 27 cm. After pouring and curing in an autoclave, it was cut into 50 cm lengths, and steel pipes with a wall thickness of 12 mm and an outer diameter of 40 cm were connected above and below to manufacture a concrete steel pipe composite part.

At the top of this is a type of concrete pile with an outer diameter of 30
An AHS pile manufactured by Asahi Kasei Industries, Ltd. with an inner diameter of 18 cm is placed so that their centers coincide, and the end plate 7 of the AHS palui and the steel plate 3 of the concrete steel pipe composite part are integrated by welding to form a concrete steel pipe composite part. Concrete piles were used.

This pile was sunk by hitting the top of the pile into a geological stratum in a cold region with a thick peat layer with an extremely low N value and a sloping hard layer underneath. Furthermore, the above-mentioned AHS pile is welded and added above this pile,
The top of the pile was hammered and lowered to allow the tip of the concrete-steel pipe composite section at the tip of the pile to reach the specified supporting ground.

The foundation pile of the present invention, which was sunk in this way, showed no abnormality due to damage to the lower part of the pile when it was driven and sunk while applying a blow, and a supporting capacity of more than 62 tons was secured.

Next, after measuring the bearing capacity, the pile was dug out to check the condition of the tip of the pile. As a result, no damage was observed to the concrete-steel pipe composite section at the tip of the pile.

Example 2 Using the same construction method as Example 1, the pile of Example 1 was inserted into a hole that had been drilled in advance until it reached the supporting ground, penetrating the boulder layer provided in the stratum including a boulder layer in the middle of the stratum. An attempt was made to sink the pile, but perhaps because the excavation hole had partially collapsed or bent, the pile could not be sunk under its own weight, so the pile was sunk by hitting the top of the pile. Furthermore, the above-mentioned AHS pile was welded and added to the top of this pile, and the top of the pile was sunk while being hammered, allowing the tip of the concrete-steel pipe composite section at the tip of the pile to reach the supporting ground at the planned depth. .

The foundation pile of the present invention, which was sunk in this way, showed no abnormalities due to damage to the lower part of the pile when it was driven and sunk while applying a blow, and a supporting capacity of more than 62 tons was secured.

Next, after measuring the bearing capacity, the pile was dug out to check the condition of the tip of the pile. As a result, no damage was found to the concrete composite part at the tip of the pile.

Comparative Examples 1 and 2 On the other hand, for comparison, instead of the concrete steel pipe composite part of the present invention, an AHS pile manufactured by Asahi Kasei Corporation, which is a concrete pile, was cut as a hollow concrete with almost the same size as the concrete steel pipe composite part. Then, we placed steel pipes on top and bottom of the pipes and adhered them to concrete using mortar to manufacture the enlarged tip. An ASH pile of the same size as that used in Example 1 was placed on top of this so that its center coincided with the enlarged section, and the pile was integrated to form a concrete pile with an enlarged diameter concrete section.

An attempt was made to sink this pile in the same ground as in Example 1 and in the same ground as in Example 2 using the same method as in each example, but in the ground in the cold region of Example 1, it was difficult to sink the pile into the specified ground and the ground surface above it. Damage to the pile was felt when the tip reached the position corresponding to the boundary, and in the ground of Example 2, before reaching the specified supporting ground,
It appears that the enlarged tip part was damaged during the process. In both cases, the piles were forcibly sunk to the designated supporting ground, regardless of the damage to the piles, but in each case, the bearing capacity was low.
It did not reach 10 tons.

After measuring the bearing capacity in this way, the pile was dug out to check the condition of the tip of the pile. the result,
In both of these comparative piles, the concrete composite part at the tip was damaged.

Comparative Example 3 and Comparative Example 4 The same enlarged diameter concrete part used in Comparative Example 2 and Comparative Example 3 was used as the enlarged tip part, and on top of this, an outer diameter of 30 mm, which is a type of hollow concrete steel pipe composite pile, was used.
An ACCS pile made by Asahi Kasei Industries, Ltd., which is a hollow concrete-steel pipe composite pile with concrete integrated with a thickness of 54 mm, is placed on the inside of a steel pipe with a wall thickness of 6 mm. It was made into a concrete pile with an enlarged diameter concrete section.

An attempt was made to sink this pile in the same ground as in Example 1 and in the same ground as in Example 2, using the same method as in each example, but in the ground in the cold region of Example 1, the specified Damage to the pile was felt when the tip of the pile reached the boundary between the ground and the ground surface above it, and in the ground described in Example 2, the tip of the pile was damaged on the way before reaching the specified supporting ground. It looks like the enlarged part is damaged. In both cases, the piles were forcibly sunk to the designated supporting ground, regardless of the damage to the piles, but their bearing capacity did not reach 10 tons.

After measuring the bearing capacity in this way, the pile was dug out to check the condition of the tip of the pile. the result,
In both of these comparative piles, the concrete composite part at the tip was damaged.

[Effect of idea]

By having the structure of the pile of the present invention as described above, even if a driving method that applies a high blow to the top end of the pile is used to increase the bearing capacity, the concrete and steel pipe composite section at the bottom of the pile will not be damaged. The effect is that the pressure applied to the composite part is small and that the pressure applied to the composite part is reliably transmitted from the upper part to the composite part, and a large supporting force can be reliably expressed. In particular, even in poor ground conditions where pile tips are easily damaged, such as in cold regions, where high bearing capacity could not be obtained even with the application of the driving method (impact method), it is possible to sink the pile using the hammering method, resulting in a high bearing capacity. It has excellent effects that cannot be obtained with conventional piles.

Furthermore, it exhibits great resistance even when large shearing forces are applied to the piles due to earthquakes, etc.

[Brief explanation of the drawing]

1 and 2 are half-cut front views showing an example of the concrete pile of the present invention. 1... Concrete part, 2... Steel pipe, 3, 4...
... Steel plate, 5 ... Concrete pile, 6, 8 ... Welded part, 7 ... End plate.

Claims (1)

[Scope of Claim for Utility Model Registration] A concrete steel pipe composite part having a diameter larger than the outer diameter of the concrete pile 5 is provided below the concrete pile 5, and the concrete steel pipe composite part has a hollow part inside the steel pipe 2. There is concrete 1 having A concrete pile with a concrete steel pipe composite part, which is a concrete steel pipe composite part with a structure protected by steel plates 3 and 4 integrated with the concrete steel pipe composite part.