JP2015143462A - steel pipe pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel pipe pile which can exhibit a prescribed vertical support force and a withdrawal force even if being hammered and stopped at a surface layer part of the soft soil by closely contacting with the soil of a pile peripheral face by the steel pipe pile itself by rotation intrusion construction, and by increasing peripheral face friction resistance to the surrounding soil.SOLUTION: A steel pipe pile 1 has a wing 5 which performs screw action into the ground at a tip or an external periphery of a pile main body 3. In the steel pipe pile 1, a plate body 7 having no notch for allowing the passage of sediment is fixed to the pile main body 3 in a flange shape in advance in an upper part of the wing 5 of the pile main body 3, and in a position being the ground side rather than the ground surface side in a state in which the steel pipe pile is constructed, an engagement dowel contributing to the rotation intrusion construction of a pile head part is fit to a weld bead of an internal face of the steel pipe pile 1, and the steel pipe pile is arranged and fixed to a side at which the weld bead is pressed at the rotation intrusion construction.

Description

  The present invention relates to a pile that supports a structure, and particularly to a steel pipe pile that can ensure horizontal resistance and pull-out resistance even in soft ground.

  In recent years, construction of large-scale solar power plants, so-called mega solars, has increased. Mega solar construction uses unused land with weak ground, such as landfills and landfills in port areas. Moreover, the pile foundation construction method is also employ | adopted for the foundation of the mount frame which supports a solar cell panel.

As for piles used for solar power generation stands, small diameter (approximately 50mm to 100mm inside and outside) piles are the mainstream because the superstructure is lightweight. In principle, pile foundations have their tips reach the support layer, but there are many piles with a length of 1 to 2 meters.
In general, a small-diameter pile cannot be expected to have much frictional force on the peripheral surface of the pile, and the tendency is particularly large in the surface layer portion. For this reason, in soft ground, a combination of surface soil improvement using soil cement and a rotating penetrating steel pipe pile with tip wings or spiral wings have been used to obtain bearing capacity through the resistance of the wings. The construction of the rotating penetrating steel pipe pile is to attach the engaging piece to the pile head by welding, engage the rotating cap (coupling) of the pile driving machine, rotate the steel pipe pile by the rotation of the rotating cap, and penetrate into the ground It is common.

Patent Document 1 discloses a method for improving the peripheral frictional support force of a steel pipe pile.
The steel pipe pile of patent document 1 is a hollow cylindrical steel pipe pile which connects an upper pile to a lower pile, and after constructing a lower pile, the upper pile with which the flange part was fixed to the front end side peripheral surface, The upper and lower piles are connected by being driven into the soil so as to be fitted up to a certain portion on the upper end side of the lower pile driven into.

  This driving method is to press-fit into the soil while rotating the lower pile, stop the rotation when the tip of the lower pile reaches a predetermined depth, then press-fit the lower pile further into the soil only by press-fitting, then Insert the upper pile into the lower pile and press it into the soil while rotating only the upper pile. When the tip of the upper pile reaches the specified depth, stop the rotation, and then press it into the lower pile. However, the loosened soil is consolidated by the flange of the upper pile.

  Further, in Patent Document 2, a “pile main body, a propulsion wing provided on the lower end side of the pile main body and having a spiral portion at least partially proceeding to dig the ground by rotation of the pile main body, and an upper end portion of the pile main body” A foundation pile provided with a support portion that is provided and supports a structure, and a pressure blade that is provided in a middle portion in the longitudinal direction of the pile body and compresses the ground disturbed by the propulsion blade by the propulsion force of the pile body ”( (See claim 1 of Patent Document 2).

JP 2005-171621 A Japanese Unexamined Patent Publication No. 2014-077299

Among those described above, ground improvement by soil cement has a problem that the original state of the soil cannot be restored.
In addition, the rotating penetrating steel pipe pile disturbs the soil in the range of the wing during construction, so design strength cannot be expected until a certain time has elapsed after construction, especially in soft ground, it takes a long time to recover. is there.
Furthermore, the steel pipe pile in patent document 1 constructs a lower pile first, and then constructs an upper pile so that the upper part of a lower pile may be inserted in an upper pile. Regarding the construction of the upper pile, it is constructed by rotating intrusion to a certain range, then press-fitted and finally connected to the lower pile, and there is a problem that the construction takes a lot of labor and time.

Also, the length inserted into the upper pile of the lower pile is desirably 2/3 or more of the upper pile, and there is a large overlap area between the lower pile and the upper pile, so the material cost increases significantly. There is a problem of doing.
Furthermore, the steel pipe pile in Patent Document 1 is intended to consolidate the ground with a flange attached to the lower pile that has reached the hard ground and the flange of the upper pile, and expects circumferential friction between the consolidated layer and the ground around the pile. In applications where the pile tip does not reach a hard support layer, such as the soft ground that the steel pipe pile of the present invention assumes as one of the construction grounds, it is sufficient for consolidation at the heel part attached to the lower pile Because there is no reaction force, there is a problem that it cannot be utilized.

  And although the steel pipe pile in patent document 2 has a press wing | blade similar to this invention, since rotation penetration torque increases with rotation penetration construction, a pile head may be damaged at the time of construction. There is. In this regard, the inventor conducted a construction experiment of a steel pipe pile having a pressing blade with an engagement piece generally used for the pile head. As a result, the rotational torque increased and the pile head was broken at the weld bead. As a result, the construction of the pile became impossible. FIG. 6 is a photograph of the pile head at this time, and shows a state in which an engagement piece provided inside the steel pipe is protruding outward while avoiding the pile head from being U-shaped at the bead portion.

Since the steel pipe pile in Patent Document 2 has a structure in which the pile head is reinforced by attaching the support portion to the pile head in advance, the risk of pile head destruction is small.
However, a rotating jig of a general pile driving machine cannot be used, and a dedicated jig is necessary. Moreover, when a penetration defect (high stop) arises, it will be necessary to cut a pile head and to attach a support part anew. This poor penetration is more likely to occur when the rotary penetration construction and the consolidation are performed at the same time. Therefore, there is a problem that the necessity for reattaching the support portion is high and the workability is poor.

  The present invention was made in order to solve the above problems, and by rotating and penetrating construction, the ground of the pile peripheral surface is consolidated with the steel pipe pile itself, and the peripheral friction resistance with the surrounding ground is increased. The purpose is to obtain a steel pipe pile that can exhibit a predetermined vertical support force, pull-out force, and horizontal resistance force even when it is stopped at the surface layer portion of soft ground.

(1) A steel pipe pile according to the present invention is a steel pipe pile provided with a wing having a screwing action into the ground at the tip or outer periphery of the pile main body, above the wing in the pile main body, and In a state where the steel pipe pile is constructed, a plate body without a notch through which earth and sand pass is fixed in advance in a flange shape perpendicular to the pile axis direction, at a position that becomes the ground side from the ground surface,
In the pile head, the engagement piece that contributes to the rotation penetration construction is aligned with the weld bead on the inner surface of the steel pipe pile main body, and is placed on the side where the welding bead is pressed during the rotation penetration construction, and fixed by welding. It is a feature.

(2) Moreover, in the thing as described in said (1), when it is set as the Young's modulus E of the said pile main body, the cross-sectional secondary moment I of the said pile main body, the horizontal ground reaction force coefficient kh, and the pile diameter D, the said board It is characterized in that the body mounting height is within 1 / (kh · D / (4EI)) ^0.25 from the ground surface.

(3) Further, in the above (1) or (2), the pile in the range from the wing to the plate provided on the top of the wing is compacted to form a cylinder by rotating the pile. It is characterized by forming a root of the root.

  In the present invention, a steel pipe pile provided with a wing having a screwing action into the ground on the tip or outer periphery of the pile body, and above the wing in the pile body, and the steel pipe pile is installed At the position that is in the ground side than the ground surface, by fixing the plate body without the notch through which the earth and sand pass in a flange shape perpendicular to the pile axis direction, just by performing the rotation penetration construction, Even if the soil between the wing and the plate body is consolidated to form a consolidated portion, and the surface of the soft ground is struck by the frictional resistance between the peripheral surface of the consolidated portion and the surrounding ground, a predetermined vertical Since the supporting force and the pulling force are exhibited, and especially the consolidation directly under the plate body without the notch is increased and the fixing degree of the pile body is improved, the horizontal resistance can be increased.

It is explanatory drawing of the steel pipe pile which concerns on one embodiment of this invention. It is explanatory drawing explaining the construction method of the steel pipe pile which concerns on one embodiment of this invention (the 1). It is explanatory drawing explaining the construction method of the steel pipe pile which concerns on one embodiment of this invention (the 2). It is explanatory drawing explaining the construction method of the steel pipe pile which concerns on one embodiment of this invention (the 3). It is explanatory drawing explaining the structure of the pile head part of the steel pipe pile which concerns on one embodiment of this invention. It is a photograph explaining the subject which the present invention is going to solve, and shows the state of the pile head at the time of constructing in the conventional example.

As shown in FIG. 1, a steel pipe pile according to an embodiment of the present invention is a steel pipe pile 1 in which a tip wing 5 having a screwing action into the ground is provided at the tip of a pile body 3, and the pile body 3 The plate body 7 having no notch through which earth and sand pass is formed in a flange shape on the pile body 3 at a position above the tip wing 5 and in a state where the steel pipe pile is installed and on the ground side from the ground surface. It is fixed in advance.
Hereinafter, each configuration will be described in detail.

<Pile body>
Although the cross-sectional shape of the pile main body 3 shown in FIG. 1 is circular, the cross-sectional shape of the pile main body of the steel pipe pile according to the present invention is not limited to a circular shape, and includes, for example, a polygonal cross-sectional shape.

<Tip Wing>
The tip wing 5 is provided at the tip of the pile body 3 and has a screwing action into the ground. The shape of the tip wing 5 is, for example, as shown in FIG. 1, in which two semicircular flat plates are fixed by inclining in opposite directions.
However, the shape of the tip wing 5 is not limited to that shown in FIG. 1, and any function is possible as long as it has a function that contributes to the rotation penetration construction and has a function of discharging soil above the rotation penetration. For example, the shape may be a spiral shape, or a flat plate having a notch in the radial direction and the notch being inclined.
Also, the shape of the tip wing 5 may be an arbitrary shape such as a rectangle, a polygon, or a shape obtained by processing a part of the rectangle into an arc shape.
Furthermore, in the example shown in FIG. 1, as the tip wing 5, the wing is provided at the tip of the pile body 3, but the wing of the present invention is not limited thereto, and is provided at the outer peripheral portion of the pile body 3. May be.

  The outer diameter of the tip wing 5 is preferably at least twice the pile diameter, and more preferably at least three times the pile diameter when used on soft ground. This is because the tip support force can be sufficiently secured.

<Plate>
The plate body 7 is a plate-like body having no notch through which earth and sand pass, and is fixed in advance in a flange shape perpendicular to the pile axis direction.
The fixing method may be either welding or mechanical means. In the example of FIG. 1, the shape of the plate body 7 is a disk-shaped plate. However, the shape of the plate body 7 is not limited as long as it is a closed shape that does not discharge earth and sand at the top of the rotary penetration construction. Further, it may be a curved shape or a cap shape instead of a flat plate. Furthermore, what provided the embossed process and the rib on the flat plate may be used. The plate thickness of the plate body 7 is preferably equal to or greater than the plate thickness of the pile body 3.

The outer diameter of the plate body 7 is basically the same as the outer diameter of the tip wing 5, but if the ground 9 on which the steel pipe pile 1 is constructed is extremely soft, the dimensions may be appropriately increased.
Although the ground 9 assumed in the present invention is soft ground, the outer diameter of the tip wing 5 is reduced when the embankment layer is strong only on the surface layer, or when the ground 9 is strong or the consolidation reaction force increases. It may be made smaller than the outer diameter so that the propulsive force of rotation penetration can be won. For the above reasons, the outer diameter of the plate body 7 may be in the range of 0.8 to 1.2 times the outer diameter of the tip wing 5.

The mounting position of the plate body 7 is arranged so as to be in the ground side from the ground surface in a state where the pile is constructed. More specifically, a range in which the depth from the ground surface is not more than about three times the outer diameter of the tip wing 5 is a guide. This is because if the fixing position of the plate body 7 is too close to the tip wing 5, it becomes difficult to penetrate the steel pipe pile 1.
Moreover, when the Young's modulus E of the pile body 3, the cross-sectional secondary moment I of the pile body 3, the horizontal ground reaction force coefficient kh, and the pile diameter D, the effective depth that becomes the horizontal resistance with respect to the steel pipe pile 1 is 1 / (kh · D / (4EI)) is given as ^0.25 , but the fixing position of the plate 7 is set so that the gap 15 is about this depth, and the gap 15 formed at this time is concrete. By incorporating a rigid body such as the block 17, the horizontal resistance may be increased.

<Pile head>
The pile head of the steel pipe pile 1 is engaged with a rotary cap (coupling) of a pile driving machine, and the engagement piece 20 is welded to rotate the steel pipe pile 1 by the rotation of the rotary cap and penetrate into the ground. (See FIG. 5). The mounting position is, for example, the inner surface of the pile main body 3 so that the gusset for mounting the upper mount member does not hinder the mounting after the construction when it is used as a support for the solar power generation mount. In that case, the engagement piece 20 is arrange | positioned along the weld bead 21 of the steel pipe which comprises the pile main body 3 which is rising on the inner surface. This facilitates positioning of the engaging piece 20 and ensuring of verticality. Furthermore, since the engagement piece 20 is arranged so as to be on the side where the weld bead 21 is pressed during the rotation penetration construction, the welding bead 21 which is a weak point in strength is not pulled during the rotation penetration construction, and the soundness is maintained. Can keep.

The function of the steel pipe pile 1 of this Embodiment comprised as mentioned above is demonstrated based on FIGS. 2-5 with a construction method.
By rotating the steel pipe pile 1, the tip wing 5 penetrates the ground 9 while discharging the soil on the lower surface upward, and the ground 9 is placed above the tip wing 5 by the tip wing 5 as shown in FIG. 1. The soil disturbing part 11 is formed which is disturbed and has a lower density than the surrounding ground.

  If the rotation construction of the steel pipe pile 1 is further continued, the plate body 7 reaches the ground surface, and further penetrates into the soil as shown in FIG. As the penetration amount of the steel pipe pile 1 increases, the soil discharged by the tip wing 5 increases and the depth of the soil disturbing portion 11 increases, but the plate body 7 is on the surface of the ground 9. After reaching, the distance between the tip wing 5 and the plate body 7 does not change, so that the soil is consolidated in the region sandwiched between the tip wing 5 and the plate body 7, and a cylindrical solidified portion 13 is formed.

  In this process, since the rotational penetration torque increases, the stress of the engagement piece 20 of the pile head increases, and the weld bead of the steel pipe pile may break and become unworkable. In this regard, in the present invention, the engagement piece 20 is disposed at a position to push the weld bead 21 which is a weak point in strength at the time of the rotation penetration construction, so that the weld bead portion is broken even if the construction torque increases. There is nothing.

By forming the root hardening part 13 by the said process, the surrounding surface frictional force of the pile periphery disturbed by the rotation penetration construction and the ground 9 recovers at an early stage.
At this time, as shown in FIG. 3, a gap 15 is formed above the plate 7 by the amount of consolidation.

  As described above, the horizontal resistance may be increased by incorporating a rigid body such as the concrete block 17 in the gap 15 (see FIG. 4).

The steel pipe pile 1 constructed as described above restrains the soil existing between the tip wing 5 and the plate body 7. Therefore, even if a pulling out or pushing force is applied to the steel pipe pile 1, no deviation occurs between the root hardening portion 13 (consolidation layer) and the steel pipe pile 1, and no friction force acts.
Further, the root consolidation portion 13 is more compacted than the surrounding ground by compaction and protrudes in the outer peripheral direction, so that friction between the peripheral surface of the root consolidation portion 13 and the ground 9 increases, and the outer diameter of the tip wing 5 is increased. The peripheral frictional force can be expected as the peripheral surface length.
Therefore, even if the steel pipe pile 1 of the present invention is stopped at the surface layer portion of the soft ground, it can exhibit predetermined vertical support force and pull-out force.
Furthermore, since the consolidation directly under the plate body 7 is increased, the fixing degree of the steel pipe pile 1 is improved, and an increase in horizontal resistance, that is, a pile head displacement can be suppressed.

The specific example of the steel pipe pile shown by said embodiment is shown below.
A steel pipe with a total length of 3m, an outer diameter of 101.6mm, and a plate thickness of 4.2mm is used as the pile body. At the tip of the pile, a semi-circular tip wing 5 is twice the outer diameter of the pile body as shown in Fig. 1. Are attached alternately in an elevational view. The plate thickness of the tip wing 5 was 12 mm.
In addition, the depth of embedding in the ground is 2 m, the pile head is 1 m, and it protrudes from the ground 9 so that it can be used as a support column for the superstructure.
A donut-shaped flat plate (corresponding to the plate of the present invention) having the same outer shape as the tip wing 5 was fitted at a position 1.5 m from the pile head toward the tip, and fixed by welding. The thickness of the flat plate is 4.2 mm, but it is desirable that it is equal to or greater than the thickness of the pile body.
The said dimension is suitably changed with the ground strength of a ground where a steel pipe pile is constructed, and an action external force.
As shown in FIG. 5, a rectangular parallelepiped engagement piece 20 for rotational penetration construction is arranged and fixed to the pile head along the weld bead 21 on the inner surface of the pile body 3. In this example, since it is designed to rotate in a clockwise direction in a plan view, as shown in FIG. 5, when the welding bead 21 is on the upper side in the plan view as shown in FIG. It was.

In Example 2, a more preferable example is shown about the attachment position of the flat plate (equivalent to the plate body of this invention) fixed to a pile main body.
The diameter D of the steel pipe is 48.6mm, the plate thickness t is 2.3mm, the total length L is 1.5m, the pile head protrudes from the ground surface of 500mm, and the embedding depth l is 1m. The diameter of the tip wing is 150 mm. The Young's modulus E of the steel material is 205000 N / mm ² , and the cross-sectional secondary moment I of the steel pipe is 89867 mm ⁴ .

The ground on which the steel pipe piles are constructed is sandy ground with an N value of 1.5, a unit volume weight of 1.62 kg / m ³ , and a moisture content of 14%. The ground reaction force coefficient kh is 20,000kN / m ³ , which is a value calculated in reverse by combining the displacement obtained based on the elastic bearing beam theory from the load and displacement at the displacement of 10mm in the horizontal loading test. However, this method is not limited. Here, since the effective depth as the horizontal resistance of the steel pipe pile, that is, 1 / (kh · D / (4EI)) ^0.25 was 525 mm, the mounting depth of the flat plate from the ground surface was set to 500 mm here. . In the case where the calculation is not performed in particular, the approximate value is about three times or less the outer diameter of the tip blade 5.

  When the steel pipe pile of Example 2 configured as described above is rotated and penetrated, the soil discharged to the top of the tip wing increases and the depth of the soil disturbing portion increases, but the flat plate is on the surface of the ground. After reaching, the distance between the tip wing and the flat plate does not change, so the soil is consolidated in the area sandwiched between the tip wing and the flat plate, forming a cylindrical solidified part, and the upper part of the flat plate is Only voids are formed. Here, the root consolidation part is doubled with respect to the surrounding ground. As a result, the ground around the pile disturbed by the rotation penetration construction is recovered early.

  Since the soil is constrained within the range of the tip wing and the flat plate, even if a pulling out or pushing force is applied, there will be no displacement between the root-solidified part (consolidated layer) and the pile body. do not do. The root consolidation part is more compacted than the surrounding ground by compaction and bulges in the outer circumferential direction, so the friction between the circumferential surface of the root consolidation part and the ground increases, and the outer surface has the outer diameter of the tip wing as the circumferential surface length. Frictional force can be expected. The ratio between the pile diameter D and the outer diameter of the tip wing is about 3 times, and the circumferential friction force is proportional to the circumference, so the circumferential friction force is tripled.

  The mounting position of the flat plate in the steel pipe pile shown in Example 1 is 1500 mm from the pile head. In the installed state, a cylindrical gap portion having a depth of 500 mm is formed above the flat plate. The range in which this void portion is formed is a portion that contributes to horizontal resistance. Therefore, as shown in FIG. 4, a filler such as mortar or concrete is used for the void portion and is harder than at least the surrounding ground. By doing so, the horizontal resistance is improved and the pulling force is further increased by its weight. As a filler, a method of filling cement milk by filling ballast in advance, a steel slag hydrate solidified body, or a concrete block having substantially the same diameter may be used.

DESCRIPTION OF SYMBOLS 1 Steel pipe pile 3 Pile main body 5 Tip wing 7 Plate body 9 Ground 11 Soil disturbance part 13 Root consolidation part 15 Cavity part 17 Concrete block 20 Engagement piece 21 Weld bead

Claims (3)

A steel pipe pile provided with a wing having a screwing action into the ground at the tip or outer periphery of the pile body,
A plate body not having a notch through which earth and sand pass is provided on the pile body at a position above the wings in the pile body and on the ground side with respect to the ground surface in a state where the steel pipe pile is constructed. In advance,
In the pile head, the engagement piece that contributes to the rotation penetration construction is aligned with the weld bead on the inner surface of the steel pipe pile main body, and is placed on the side where the welding bead is pressed during the rotation penetration construction, and fixed by welding. A characteristic steel pipe pile. When the Young's modulus E of the pile body, the secondary moment I of the cross section of the pile body, the horizontal ground reaction force coefficient kh, and the pile diameter D, the mounting height of the plate body is 1 / (kh · D / (4EI)) The steel pipe pile according to claim 1, wherein the range is within ^0.25 .   3. The cylinder-shaped solidified portion is formed by compacting the soil in a range from the wing to the plate provided on the upper portion of the wing by the rotational penetration construction of the pile. Steel pipe pile as described.