JP2021055495A - Steel pipe pile - Google Patents

Abstract

To provide a steel pipe pile capable of securing sure construction and required bearing capacity at low cost.SOLUTION: A steel pipe pile 1 has a protective projection 7 on an inner surface of a steel pipe 3, and has an excavation bit 5 projecting to an inner surface side in a pile diameter direction on one tip of the steel pipe 3, and the protective projection 7 has a height higher than an inner surface side projection amount of the excavation bit 5.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steel pipe pile to be constructed on the ground where there is an obstacle in the ground.

Since steel pipe piles having a function of supporting a structure are constructed on various grounds, there may be large obstacles such as concrete and rocks on the ground during construction. In most cases, the approximate depth and size of obstacles in the soil have been determined by prior investigation.

If the obstacle exists in a shallow position in the ground and is small in size, it is pre-bored from the ground surface in advance to remove or crush the obstacle. On the other hand, if the obstacle exists deep in the ground or its size is large, the obstacle removal work is performed in advance by the casing method. This work involves constructing the casing in the ground to protect the peripheral ground, removing the earth and sand and obstacles in the casing, backfilling the earth and sand in the casing, and then pulling out the casing. After that, the pile is constructed.

In the case of this casing method, obstacle removal and pile construction machines are often different, and the construction period and construction cost increase due to the replacement of machines, and the casing diameter needs to be larger than the pile diameter, so construction efficiency There is a problem that it gets worse.

On the other hand, as disclosed in Patent Document 1, there is a construction method in which a steel pipe pile is used instead of the casing. In this construction method, a removable and recoverable excavation bit is provided at the tip of the steel pipe, a steel pipe pile is rotationally press-fitted, an obstacle layer is punched out by the effect of the excavation bit, and then the excavation bit is recovered and the steel pipe is recovered. The pile is buried to a predetermined depth (see claim 1 of Patent Document 1).

Japanese Unexamined Patent Publication No. 10-140565

The method disclosed in Patent Document 1 incorporates a mechanism capable of recovering a high-cost excavation bit. However, a hammer grab or the like is often used for actual removal of obstacles, and if a hammer grab or the like is used, there is a high possibility that the recovery mechanism such as a wire will be damaged.
This point will be described in detail.
Obstacles removed from the inside of the steel pipe may be several meters above the surface of the earth, and in some cases more than 10 meters. The hammer grab is also lowered from the ground surface to the position of the obstacle, but if the hammer grab rolls, it may collide with the inner surface of the steel pipe. In such a case, it is possible that the steel pipe is damaged and the bearing capacity is adversely affected.

Further, when the hammer grab collects an obstacle, it does not always reach the vicinity of the center of the inner surface of the steel pipe. If the hammer grab falls near the tip of the steel pipe, not only the tip of the steel pipe but also the excavation bit may be damaged. When a steel pipe pile is used instead of the casing, the steel pipe pile is further dug to a predetermined depth after removing obstacles, but if the excavation bit is damaged, it becomes difficult to dig in the ground.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a steel pipe pile capable of ensuring reliable construction and necessary bearing capacity at low cost.

(1) The steel pipe pile according to the present invention has a protective protrusion on the inner surface of the steel pipe, and has an excavation bit protruding toward the inner surface side in the radial direction of the pile at one tip of the steel pipe, and the protective protrusion has a protective protrusion. The height thereof is larger than the amount of protrusion on the inner surface side of the excavation bit.

(2) Further, in the above (1), the outer diameter of the steel pipe is set to D, and the protective protrusion is provided in the range of D to 2D from the tip of the steel pipe. It is a thing.

(3) Further, in the above-mentioned (1) or (2), the protective protrusion is characterized in that it is provided continuously or discretely over the entire circumference of the inner peripheral surface of the steel pipe. It is a thing.

The steel pipe pile according to the present invention is a steel pipe pile having an excavation bit protruding inward in the pile radial direction at the tip of the steel pipe, and protects the inner surface of the steel pipe so as to project inward in the pile radial direction more than the excavation bit. By having protrusions, in order to remove obstacles in the steel pipe, even if a tool for removing obstacles such as a hammer grab is inserted up to the vicinity of the tip inside the steel pipe, the inner surface of the steel pipe and the excavation bit will not be damaged. It is possible to secure reliable construction and necessary bearing capacity at low cost. Further, since the protective protrusion is provided on the inner surface of the steel pipe, it does not disturb the ground on the peripheral surface of the pile and does not affect the bearing capacity of the pile.

It is sectional drawing in the pile axis direction of the steel pipe pile which concerns on Embodiment 1 of this invention. It is a figure which shows the state seen from the lower end side of the steel pipe pile shown in FIG. It is explanatory drawing of the construction method of the steel pipe pile which concerns on Embodiment 1 of this invention. It is sectional drawing in the pile axial direction of another aspect of the steel pipe pile which concerns on Embodiment 1 of this invention. It is sectional drawing in the pile axis direction of the steel pipe pile which concerns on Embodiment 2 of this invention. It is explanatory drawing of the construction method of the steel pipe pile which concerns on Embodiment 2 of this invention. It is sectional drawing in the pile axial direction of another aspect of the steel pipe pile which concerns on Embodiment 2 of this invention. It is a figure which shows the state seen from the lower end side of the steel pipe pile shown in FIG.

[Embodiment 1]
As shown in FIGS. 1 and 2, the steel pipe pile 1 according to the present embodiment has an excavation bit 5 protruding inward in the pile radial direction at the tip of the steel pipe 3 and an excavation bit 5 or more on the inner surface of the steel pipe 3. It is characterized by having a protective protrusion 7 protruding toward the inner surface side in the pile radial direction.
Hereinafter, each configuration will be described in detail.

<Steel pipe>
The steel pipe 3 has, for example, an outer diameter of 800 mm to 2000 mm and a wall thickness of about 8 mm to 25 mm, although the wall thickness is not particularly specified. As long as the steel pipe 3 can be used as a steel pipe pile, it is not necessary to specify the type in particular, and the method for manufacturing the steel pipe is not limited.

<Drilling bit>
The excavation bit 5 is attached to one tip of the steel pipe 3, that is, the tip on the side traveling into the ground by a plurality of weldings or the like at predetermined intervals in the circumferential direction. The excavation bit 5 has a function of excavating the ground and crushing obstacles existing in the ground.
The excavation bit 5 projects toward the inner surface side in the pile radial direction, and the amount of protrusion of the steel pipe toward the inner surface side is about several tens of mm, preferably about 10 to 20 mm. Here, the reason why the excavation bit 5 is projected inward in the diameter of the steel pipe is to facilitate the movement of the earth and sand generated by the excavation toward the inner surface of the steel pipe and to facilitate the removal to the outside.

If there is no reinforcing band or the like on the outer surface near the tip of the steel pipe 3, the excavation bit 5 is attached so as not to protrude outward from the outer surface of the steel pipe 3. By mounting in this way, the excavation bit 5 can prevent the ground around the pile from being disturbed, and the steel pipe pile 1 can support the surrounding ground.

<Protective protrusion>
The protective protrusion 7 is attached to the inner surface of the steel pipe 3. The protective protrusion 7 prevents the hammer grab 15 from colliding with the inner surface or the tip of the steel pipe 3 even when the hammer grab 15 sways.
Further, as shown in FIG. 1, the protective projection 7 is formed so that the cross section in the pile axis direction is a right triangle. As described above, it is preferable that the shape of the protective projection 7 has an inclined surface 9 that inclines inward from the upper part on the inner surface side toward the lower part. In this way, the protective protrusion 7 is less likely to be an obstacle to a falling object such as the hammer grab 15 from above, and damage to the protective protrusion 7 can be prevented. The protective protrusion 7 has the same effect as long as it is not only a right triangle as described above but also a triangle having no obtuse angle.

The height of the protective protrusion 7 is set to be larger than the amount of protrusion of the excavation bit 5 into the inner surface of the steel pipe. If the height of the excavation bit 5 is smaller than the amount of protrusion of the excavation bit 5 into the steel pipe inner surface, the effect of preventing the hammer grab 15 from colliding with the inner surface of the steel pipe 3 or the excavation bit 5 is not sufficiently exhibited. As an example of this height, for example, about 50 mm can be mentioned. If the height is too large, the inner diameter of the steel pipe 3 becomes small, and the collision frequency of the hammer grab 15 increases, which is counterproductive.

As will be described later, when the steel pipe pile 1 according to the present invention is constructed, the steel pipe pile 1 is further dug into the ground after removing obstacles in the ground. When the steel pipe 3 is deformed by the collision of the hammer grab 15, there are problems in construction such as the steel pipe pile 1 being unable to dig through the ground and problems such as a decrease in the strength of the steel pipe pile 1.
Further, when excavation is continuously performed while removing obstacles in the ground, if the excavation bit 5 is damaged, the obstacles cannot be crushed.
In this respect, according to the present invention, it is possible to prevent the steel pipe 3 from being deformed and the excavation bit 5 from being damaged, so that it is possible to prevent such a problem from occurring.

Further, the position of the protective protrusion 7 in the pile axis direction is within the range of L = D to 2D, where D is the outer diameter of the steel pipe 3 and L is the distance from the tip of the steel pipe 3 to the upper end of the protective protrusion 7. It is desirable to provide it. In this way, providing the protective protrusion 7 within a predetermined range from the tip of the steel pipe 3 prevents damage due to collision of the hammer grab 15 or the like used when removing the crushed obstacle 13 (see FIG. 3). (See FIG. 3). If the position of the protective protrusion 7 is too far from the tip of the steel pipe 3, the shaking of the hammer grab 15 or the like cannot be effectively suppressed. On the other hand, if the position of the protective protrusion 7 is too close to the tip of the steel pipe 3, the excavation bit 5 hinders the movement of the excavated earth and sand.

Further, as shown in FIG. 2, the protective projection 7 may be continuously provided like a ring extending over the entire inner peripheral surface of the steel pipe 3, but the position in the circumferential direction of the steel pipe is the position of the excavation bit 5. It may be provided discretely at predetermined intervals so as to match.

The material of the protective protrusion 7 is preferably steel or stainless steel. As long as it can be welded to the steel pipe 3, the material is not particularly limited. However, it is necessary that the material is not damaged or is less damaged even if the hammer grab 15 collides with it.
The length of the protective projection 7 in the pile axis direction may be appropriately set, and the number of steps in the pile axis direction is not limited to one and may be appropriately set.

The construction method of the steel pipe pile 1 of the present embodiment configured as described above will be described with reference to FIG. In FIG. 3, the protective protrusion 7 is not shown.
As shown in FIG. 3A, the steel pipe pile 1 is rotationally press-fitted from the ground surface using an all-around rotary machine 11 that grabs and rotates the body portion of the steel pipe pile 1, and excavates an obstacle 13 existing in the ground. Destroy by 5.
Then, as shown in FIG. 3B, the crushed obstacle 13 is removed from the pipe. The obstacle 13 is removed by dropping the hammer grab 15 to the vicinity of the pile tip, but in the present embodiment, since the protective protrusion 7 is provided, the inner surface of the steel pipe 3 and the excavation bit 5 are damaged. It is possible to construct without the occurrence of. The crushed obstacle 13 may be removed in parallel with the rotary press-fitting of the steel pipe pile 1.

After that, as shown in FIG. 3C, the pile is constructed by switching the construction machine as necessary and hitting or vibrating the pile head.
When the construction machine is switched from the all-around rotating machine 11 to one that grips the pile head, such as a three-point pile driver 17 as shown in FIG. 3 (c), a long pile protrudes from the ground surface. It is desirable to adjust the steel pipe length in advance so that it does not occur.
After that, the pile driving machine 17 advances the pile driving, and as shown in FIG. 3D, the construction is completed when the steel pipe pile 1 reaches a predetermined depth.

As described above, according to the present embodiment, although the excavation bit 5 is buried, the excavation bit 5 is completely covered with the protective projection 7 when the inner surface of the pile is viewed from above. Therefore, even if a hammer grab 15 or the like is inserted up to the vicinity of the tip in the steel pipe 3 in order to remove the obstacle 13 in the steel pipe 3, there is almost no possibility of damaging the excavation bit 5.

As shown in FIG. 4, the reinforcing band 19 may be wound around the outer surface near the tip of the steel pipe 3. In this case, the protrusion of the excavation bit 5 toward the outer surface of the steel pipe is formed by the reinforcing band 19. It is preferable that it does not protrude from the outer surface. The reason for this is to prevent the ground around the pile from being disturbed, as described above. The reinforcing band 19 may be ribbed.

[Embodiment 2]
The first embodiment assumes a vibro pile or a striking pile, but the steel pipe pile of the present embodiment relates to a middle digging root consolidation pile.

The present embodiment will be described with reference to FIG. In FIG. 5, the same parts as those in FIGS. 1 to 3 showing the first embodiment are designated by the same reference numerals.
The steel pipe pile 21 of the present embodiment has an inner surface protrusion 23 and an outer surface protrusion 25 on the inner and outer surfaces near the tip end for integrating with the root-consolidating bulb 29 (see FIG. 6) to exert a bearing capacity. The excavation bit 5 attached to the tip of the steel pipe 3 is set so that the protrusion to the outer surface side is 25 or less of the outer surface protrusion 25 and the protrusion to the inner surface side is about the same as that of the inner surface protrusion 23.
In such a structure, the excavation bit 5 is protected by the inner surface protrusion 23 and the outer surface protrusion 25, but the inner surface protrusion 23 may be damaged by the drop of the hammer grab 15.
Therefore, in the present embodiment, the protective protrusion 7 for protecting the inner surface protrusion 23 is provided near and above the inner surface protrusion 23.

The construction method of the steel pipe pile 21 of the present embodiment will be described with reference to FIG.
As shown in FIG. 6A from the ground surface, the steel pipe 3 is rotationally press-fitted using the all-around rotary machine 11, and the obstacle 13 existing in the intermediate layer is destroyed by the excavation bit 5. After that or in parallel with the rotary press-fitting, as shown in FIG. 6B, the hammer grab 15 is dropped into the steel pipe to remove the obstacle 13 from the pipe. At this time, due to the effect of the protective protrusion 7, even if the hammer grab 15 is dropped to the vicinity of the tip, the inner surface protrusion 23 and the excavation bit 5 can be installed without being damaged.

After that, the excavation auger 27 is inserted into the steel pipe 3, and the construction machine is switched as necessary to carry out the middle excavation pile construction while rotating the excavation auger 27 as shown in FIG. 6 (c). Depending on the construction method, there are also construction methods in which the piles are rotated at the same time.
Finally, as shown in FIG. 6D, the root-consolidating bulb 29 is constructed, and the construction is completed.
If the inner surface of the steel pipe 3, particularly the inner projection 23, is damaged, the bearing capacity may not be correctly transmitted to the steel pipe pile 21 when the root-consolidating bulb 29 is constructed, which may cause a problem in strength. According to this, the occurrence of such a problem can be prevented.

As described above, according to the present embodiment, although the excavation bit 5 is buried as in the first embodiment, the inner projection 23 and the excavation bit 5 are completely protected when the inner surface of the pile is viewed from above. It is in a state of being covered with the protrusion 7. Therefore, even if a hammer grab 15 or the like is inserted up to the vicinity of the tip in the steel pipe 3 in order to remove the obstacle 13 in the steel pipe 3, there is almost a possibility that the inner projection 23 and the excavation bit 5 are damaged. Absent.
Further, since the excavation bit 5 does not protrude more than the outer surface protrusion 25 provided on the outer surface of the steel pipe pile 21, the ground around the pile is less disturbed, and the steel pipe pile 21 can support the surrounding ground.

When inserting the excavation auger 27, it is difficult if a long pile protrudes from the ground surface. Therefore, when inserting the auger, adjust the steel pipe length in advance so that the protrusion from the ground surface is reduced. It is desirable to keep it.

When the inner surface protrusions 23 are provided in a plurality of stages, it is preferable that the protective protrusions 7 have a shape that covers all the inner surface protrusions 23, as shown in FIG. 7 (example is the case of two stages).
Further, the protective projection 7 shown in FIG. 5 continuously extends over the entire circumference of the inner surface of the steel pipe as in the first embodiment, but includes the position of the excavation bit 5 as shown in FIG. May be provided discretely.

1 Steel pipe pile (Embodiment 1)
3 Steel pipe 5 Excavation bit 7 Protective protrusion 9 Inclined surface 11 All-around rotating machine 13 Obstacle 15 Hammer grab 17 Pile driver 19 Reinforcing band 21 Steel pipe pile (Embodiment 2)
23 Inner surface protrusion 25 Outer surface protrusion 27 Excavation auger 29 Rooting bulb

Claims (3)

A steel pipe pile having a protective protrusion on the inner surface of the steel pipe.
A drilling bit protruding inward in the pile radial direction is provided at one end of the steel pipe.
The protective protrusion is a steel pipe pile whose height is larger than the amount of protrusion on the inner surface side of the excavation bit. The steel pipe pile according to claim 1, wherein the outer diameter of the steel pipe is D, and the protective protrusion is provided in the range of D to 2D from the tip of the steel pipe. The steel pipe pile according to claim 1 or 2, wherein the protective protrusion is continuously or discretely provided over the entire circumference of the inner peripheral surface of the steel pipe.

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