WO2020184282A1

WO2020184282A1 - Steel pipe pile and method for installing steel pipe pile

Info

Publication number: WO2020184282A1
Application number: PCT/JP2020/008862
Authority: WO
Inventors: 和秀戸田; 妙中　真治; 吉郎石濱; 悦孝柳; 裕貴日下; 将一田邊; 正道澤石; 智之東海林
Original assignee: 日本製鉄株式会社
Priority date: 2019-03-08
Filing date: 2020-03-03
Publication date: 2020-09-17
Also published as: JPWO2020184282A1; JP7192963B2

Abstract

A steel pipe pile (10) that is provided with a steel pipe body (11), and plate-shaped drilling bits (12) attached to an end surface (11E) of the steel pipe body (11) at an angle (θ) with respect to a tangent to the circumferential direction of the steel pipe body and projecting in the axial direction of the steel pipe body (11), wherein the drilling bits (12) include: first drilling bits (121) that project from the end surface (11E) of the steel pipe body (11) in the axial direction of the steel pipe body (11) by an amount corresponding to a first height (H1), and second drilling bits (122) that project from the end surface (11E) of the steel pipe body (11) in the axial direction of the steel pipe body (11) by an amount corresponding to a second height (H2) greater than the first height (H1).

Description

Construction method of steel pipe pile and steel pipe pile

The present invention relates to a steel pipe pile and a method for constructing a steel pipe pile.

The excavation bit attached to the tip of the steel pipe pile is expected to have the effect of controlling the movement of the excavated soil according to the rotation direction of the pile and suppressing or promoting the blockage of the soil inside the pipe, in addition to the conventional effect of excavating the ground. To. For example, in Patent Document 1, the central axis in the longitudinal direction of the excavation bit and the tangential direction at the intersection of the outer periphery of the steel pipe pile have an angle, and the cutting edge of the excavation bit is directed toward the inside of the steel pipe pile by this angle. The technology to be provided is described. As a result, for example, before the pile tip reaches the support layer, the earth and sand are pushed out to the outside of the pile to suppress the blockage of the soil in the pipe, thereby improving the excavability, and after the pile tip reaches the support layer, the pile. By reversing the direction of rotation of the pile, the earth and sand are taken into the inside of the pile, and high bearing capacity can be obtained by promoting the blockage of the soil inside the pipe.

Japanese Patent No. 5053154

However, when the tip of the steel pipe pile is penetrated into the support layer, a large construction resistance (rotational torque or vertical pressure input) acts on the excavation bit attached to the tip of the pile due to the high ground strength, resulting in the excavation bit. It is expected to wear. Therefore, in order to maximize the effect of the excavation bit as described in Patent Document 1, for example, it is desirable to have a structure capable of maintaining the function of the excavation bit against wear.

Therefore, an object of the present invention is to provide a new and improved method for constructing steel pipe piles and steel pipe piles, which can maintain the function of the excavation bit against wear during excavation.

[1] A steel pipe pile provided with a steel pipe body and a plate-shaped excavation bit that is attached to the end surface of the steel pipe body at an angle with respect to the circumferential tangent line of the steel pipe body and projects in the axial direction of the steel pipe body. However, a first excavation bit projecting from the end face of the steel pipe body in the axial direction of the steel pipe body by the first height, and a second height higher than the first height in the axial direction of the steel pipe body from the end face of the steel pipe body. A steel pipe pile including a second drilling bit that protrudes so much.
[2] An inclination is formed on the tip surface of at least one of the first excavation bit and the second excavation bit so that the protrusion height increases from the inside to the outside in the radial direction of the steel pipe body [1]. Steel pipe pile described in.
[3] According to [1] or [2], at least one of the first excavation bit and the second excavation bit is formed with a tapered cross section that becomes thicker from the inside to the outside in the radial direction of the steel pipe body. Steel pipe pile.
[4] Of [1] to [3], the excavation bit further includes a third excavation bit protruding from the end face of the steel pipe body by a third height higher than the second height in the axial direction of the steel pipe body. The steel pipe pile according to any one item.
[5] The item according to any one of [1] to [4], wherein the excavation bit has a plate shape curved so as to have a C-shape or an S-shape when the steel pipe pile is viewed from the tip side. Steel pipe pile.
[6] The excavation bit protrudes at least either outside or inside in the radial direction of the steel pipe body, and the first excavation bit protrudes by the first distance in the radial direction of the steel pipe body from the pipe thickness center line of the steel pipe body. By doing so, the first excavable region is provided, and the second excavation bit projects from the pipe thickness center line of the steel pipe body by a second distance longer than the first distance in the radial direction of the steel pipe body. The item according to any one of [1] to [5], which has a second excavable area extended from the first excavable area at least either outside or inside the steel pipe body in the radial direction. Steel pipe pile.
[7] The first drilling bit is attached at a first angle with respect to the circumferential tangent of the steel pipe body, and the second drilling bit is larger than the first angle with respect to the circumferential tangent of the steel pipe body. The steel pipe pile according to [6], which is attached at a second angle.
[8] The first excavation bit has a first length along the attachment direction of the first excavation bit, and the second excavation bit is the first along the attachment direction of the second excavation bit. The steel pipe pile according to [6] or [7], which has a second length longer than the length of.
[9] The method for constructing a steel pipe pile according to any one of [1] to [8], in which the excavation bit removes earth and sand from the outside of the steel pipe body until the tip of the steel pipe pile reaches a predetermined depth. The process of excavating while rotating the steel pipe pile in the first rotation direction, and the steel pipe in the second rotation direction in which the excavation bit takes in the earth and sand inside the steel pipe body until the tip of the steel pipe pile reaches the stopping depth. Construction method of steel pipe pile including the process of excavating while rotating the pile.
[10] The method for constructing a steel pipe pile according to [9], wherein the tip of the steel pipe pile reaches the support layer at the time of stopping, and then the steel pipe pile is rotated in the second rotation direction.
[11] At the time of stopping, excavation is performed while rotating the steel pipe pile in the second rotation direction immediately before the tip of the steel pipe pile reaches the support layer, and the steel pipe pile is stopped after reaching the support layer. , [9]. The method for constructing a steel pipe pile.
[12] The steps of excavating while rotating the steel pipe pile in the first rotation direction and the step of excavating while rotating the steel pipe pile in the second rotation direction are alternately carried out [9] to [11]. The method for constructing a steel pipe pile according to any one of the above items.

According to the above configuration, the construction resistance is borne by the second excavation bit having a higher protrusion height, and the wear of the first excavation bit can be suppressed by that amount. Therefore, the function of the excavation bit can be maintained against the wear during excavation.

It is a figure which looked at the steel pipe pile which concerns on 1st Embodiment of this invention from the side and the tip side. It is a figure which shows the deformation example of the steel pipe pile shown in FIG. It is a figure which shows the deformation example of the steel pipe pile shown in FIG. It is a figure which shows another example of the steel pipe pile which concerns on 1st Embodiment of this invention. It is a figure which shows still another example of the steel pipe pile which concerns on 1st Embodiment of this invention. It is a figure which looked at the steel pipe pile which concerns on 2nd Embodiment of this invention from the side and the tip side. It is a figure which shows another example of the steel pipe pile which concerns on 2nd Embodiment of this invention. It is a figure which shows still another example of the steel pipe pile which concerns on 2nd Embodiment of this invention. It is a figure which looked at the steel pipe pile which concerns on 3rd Embodiment of this invention from the side and the tip side. It is a figure which shows the modification of the 1st and 2nd Embodiment. It is a figure which shows the modification of the 1st and 2nd Embodiment. It is a figure which shows the modification of the 1st and 2nd Embodiment. It is a figure which shows the modification of the 1st and 2nd Embodiment. It is a figure which shows the modification of the 1st and 2nd Embodiment. It is a graph which shows the experimental result about the mounting angle of the excavation bit. It is a figure for demonstrating the experiment for verifying the wear suppression effect of the excavation bit. It is a graph which shows the result of the experiment shown in FIG.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

(First Embodiment)
FIG. 1 is a view of a steel pipe pile according to a first embodiment of the present invention as viewed from the side and the tip side. As shown in FIG. 1, the steel pipe pile 10 includes a steel pipe main body 11 and a drilling bit 12 attached to an end surface 11E of the steel pipe main body 11 and protruding in the axial direction of the steel pipe main body 11. The excavation bit 12 includes a first excavation bit 121 and a second excavation bit 122. In the present embodiment, both the first excavation bit 121 and the second excavation bit 122 are attached at an angle θ (0 <θ <90 °) with respect to the circumferential tangent of the steel pipe body 11. Here, the angle theta, the thickness center line _{L C12} plate-like drill bit 12 is at a position intersecting the wall thickness center line _{L C11} steel pipe body 11, the thickness center line _{L C12} and the pipe thickness center line _{L C11} This is the angle formed by the tangent line _LT11 (the circumferential tangent line of the steel pipe body 11). Hereinafter, the angle θ is also referred to as the mounting angle of the excavation bit 12. The attachment directions of the first excavation bit 121 and the second excavation bit 122 are directions tilted by the respective attachment angles θ1 and θ2 with respect to the circumferential tangent of the steel pipe main body 11.

In the present embodiment, since the excavation bit 12 has the attachment angle θ, the steel pipe pile 10 is rotated counterclockwise as shown in FIG. 1 until the tip of the pile reaches a predetermined depth, for example, during excavation using the steel pipe pile 10. It is possible to excavate while rotating to (CCW) and push the earth and sand to the outside of the steel pipe main body 11 to suppress the blockage of the soil inside the pipe. Further, the steel pipe pile 10 is excavated while rotating clockwise (CW) shown in FIG. 1 until the tip of the pile reaches the stopping depth, and the earth and sand are taken into the inside of the steel pipe main body 11 to promote the blockage of the soil inside the pipe. By doing so, high support can be obtained. The excavation bit 12 has edges both inside and outside in the radial direction of the steel pipe body 11, which enables excavation by reversing the rotation direction of the steel pipe body 11 as described above.

In the present embodiment, both the first excavation bit 121 and the second excavation bit 122 project to both the outside and the inside of the steel pipe body 11 in the radial direction, and the pipe thickness of the steel pipe body 11 is centered in the mounting direction. _{Crosses the} center line _LC11 . In another embodiment, as in the example shown in FIGS. 2 and 3, the excavation bit may protrude only to either the outside or the inside in the radial direction of the steel pipe body 11.

Further, in the present embodiment, the first drill bit 121 by a height _{H 1} protrudes from the end surface 11E of the steel pipe body 11 in the axial direction of the steel pipe body 11 of the drill bit 12, the second drill bit 122 steel body 11 The height H ₂ protrudes from the end surface 11E of the steel pipe body 11 in the axial direction by the height H _2, and the height H ₂ is higher than the height H ₁ (H ₁ <H ₂ ). For example, when excavating a layer having high ground strength such as a support layer, it is assumed that the excavation bit 12 is worn due to a large construction resistance acting on the excavation bit 12. On the other hand, by making the protrusion height H ₂ of the _second excavation bit 122 higher than the protrusion height H ₁ of the first excavation bit 121 as described above, the second excavation bit that precedes in the excavation It is possible to make the 122 bear the construction resistance and suppress the wear of the first excavation bit 121 whose construction resistance is reduced by that amount. The wear of the first excavation bit 121 becomes remarkable, for example, after the protruding height of the second excavation bit 122 becomes about the same as that of the first excavation bit 121 due to the wear. In some cases, the wear of the excavation bit 121 of 1 is not remarkable. By suppressing the wear of the first excavation bit 121 in this way, even if excavation is carried out in a layer having high ground strength, the function of suppressing or promoting the blockage of the in-pipe soil by the excavation bit 12 as described above can be achieved. Can be maintained.

The method of attaching the excavation bit 12 to the steel pipe body 11 may be, for example, welding or mechanical joining means such as screwing. Further, in the example shown in FIG. 1, the end surface 11E of the steel pipe body 11 and the upper end surface of the excavation bit 12 coincide with each other, but the excavation bit 12 is fitted into, for example, a groove or a notch formed in the end surface 11E. It can be joined above, or it can be joined after fitting the end of the steel pipe body 11 including the end face 11E into the groove or notch formed in the upper end surface of the excavation bit 12, or the end face 11E and the upper end surface of the excavation bit 12. It is possible to form grooves or notches in both of them so that these grooves or notches fit together and then join. In this case, the end surface 11E of the steel pipe body 11 and the upper end surface of the excavation bit 12 do not always match. The same applies to the other examples described below.

FIG. 4 is a diagram showing another example of the steel pipe pile according to the first embodiment of the present invention. In the example shown in FIG. 4, the first excavation bit 121A and the second excavation bit 122A included in the excavation bit 12 have a mounting angle θ as in the example described with reference to FIG. 1 above. Further, the protrusion height H ₂ of the _second excavation bit 122A is higher than the protrusion height H _{1 of} the first excavation bit 121A. In addition, in the illustrated example, the tip surfaces 121E and 122E of the first excavation bit 121A and the second excavation bit 122A, that is, the end surface of the steel pipe body 11 opposite to the end surface 11E, in the radial direction of the steel pipe body 11. A slope is formed in which the protruding height increases from the inside to the outside of the pipe.

When the steel pipe body 11 is rotated clockwise (CW) shown in FIG. 4 by forming an inclination on the tip surfaces 121E and 122E of the first excavation bit 121A and the second excavation bit 122A as described above. The protrusion height of the first excavation bit 121A and the second excavation bit 122A becomes higher in the portion that comes into contact with the earth and sand in advance, and the resistance to wear of the first excavation bit 121A and the second excavation bit 122A is increased. Can be improved. The protruding heights H ₁ and H ₂ of the first excavation bit 121A and the second excavation bit 122A are, for example, the heights from the end surface 11E to the highest position of the inclined tip surfaces 121E and 122E as shown in the figure. Can be defined as. Further, in the illustrated example, both the tip surfaces 121E and 122E of the first excavation bit 121A and the second excavation bit 122A are inclined, but only one of the tip surfaces is inclined. May be good.

FIG. 5 is a diagram showing still another example of the steel pipe pile according to the first embodiment of the present invention. In the example shown in FIG. 5, the first excavation bit 121 and the second excavation bit 122B included in the excavation bit 12 have a mounting angle θ as in the example described with reference to FIG. 1 above. Further, the protrusion height H ₂ of the _second excavation bit 122B is higher than the protrusion height H _{1 of} the first excavation bit 121. In addition, in the illustrated example, the second excavation bit 122B is formed with a tapered cross section that becomes thicker from the inside to the outside in the radial direction of the steel pipe body 11. Specifically, the second excavation bit 122B has a thickness t ₁ inside the steel pipe body 11 in the radial direction and a thickness t ₂ outside, and the thickness t ₂ is larger than the thickness t ₁ (t ₁ <. t ₂ ).

By forming the second excavation bit 122B with a tapered cross section as described above, the second portion that comes into contact with the earth and sand in advance when the steel pipe body 11 is rotated clockwise (CW) shown in FIG. The excavation bit 122B becomes thicker, and the resistance to wear of the second excavation bit 122B can be improved. In the illustrated example, only the second excavation bit 122B is formed with a tapered cross section, but both the first excavation bit 121 and the second excavation bit 122B may be formed with a tapered cross section. Only the excavation bit 121 of 1 may be formed with a tapered cross section. Further, by combining the example of FIG. 5 and the example of FIG. 4, an inclination is formed on the tip surface of the first excavation bit 121 or the second excavation bit 122, and the first excavation bit 121 or the second excavation bit 122 is formed. 122 may be formed with a tapered cross section.

(Second Embodiment)
FIG. 6 is a view of the steel pipe pile according to the second embodiment of the present invention as viewed from the side and the tip side. As shown in FIG. 6, the steel pipe pile 20 includes a steel pipe main body 11 and a drilling bit 22 attached to an end surface 11E of the steel pipe main body 11. The excavation bit 22 includes a first excavation bit 221 and a second excavation bit 222. Like the first embodiment, the first drill bit 221 by a height _{H 1} protrudes from the end surface 11E of the steel pipe body 11, second drill bit 222 by a height _{H 2} protrudes from the end surface 11E of the steel pipe body 11 , Height H ₂ is higher than height H ₁ (H ₁ <H ₂ ). Further, in the present embodiment, the first excavation bit 221 is attached at an angle θ1 (0 <θ1 <90 °) with respect to the circumferential tangent of the steel pipe body 11, and the second excavation bit 222 is the circumference of the steel pipe body 11. It is attached with an angle θ2 (0 <θ2 <90 °) with respect to the directional tangent, and the angle θ2 is larger than the angle θ1 (θ1 <θ2). Here, the mounting angles θ1 and θ2 are the plate thickness center lines _LC221 and L of the first drilling bit 221 and the second drilling bit 222, respectively, similarly to the mounting angles θ described in the first embodiment. _C222 and the tangent _{L T11} of pipe thickness center line _{L C11} steel pipe body 11, that is, the angle between the circumferential tangent of the steel pipe body 11. On the other hand, in the present embodiment, the length L of the first excavation bit 121 and the second excavation bit 122 along the attachment directions is the same. The attachment directions of the first excavation bit 221 and the second excavation bit 222 are directions tilted by the respective attachment angles θ1 and θ2 with respect to the circumferential tangent of the steel pipe main body 11.

Since the excavation bit 22 has the mounting angles θ1 and θ2 as described above, the steel pipe pile 20 is rotated counterclockwise (CCW) and clockwise (CW) shown in FIG. 6 in the present embodiment as in the first embodiment. ), The effect of suppressing or promoting the blockage of the soil inside the pipe can be obtained when excavating while rotating each of them.

In addition, in the present embodiment, the attachment angle θ2 of the second excavation bit 222 is larger than the attachment angle θ1 of the first excavation bit 221. As a result, even if the length L of the first drilling bit 221 and the second drilling bit 222 along the mounting direction is the same, for example, the first drilling bit 121 is centered on the pipe thickness on the outside of the steel pipe body 11. Write a distance D2 where the second drill bit 122 protrudes from the wall thickness center line _{L C11} in the radial direction of the steel pipe body 11 is longer than the distance D1 which projects from the line _{L C11} in the radial direction of the steel pipe body 11. As a result, on the outside of the steel pipe body 11, the excavable region R2 of the second excavation bit 222 is expanded more than the excavable region R1 of the first excavation bit 221. Here, the excavable areas R1 and R2 are annular areas in which each of the first excavation bit 221 and the second excavation bit 222 excavates earth and sand when the steel pipe pile 20 is rotated in the ground. For example, regarding the outside of the steel pipe body 11, when the radius of the excavable region R1 is r1 and the radius of the excavable region R2 is r2 as shown in FIG. 6, the mounting angle is such that r2 / r1 = 1.2. θ1 and θ2 may be set.

In the present embodiment, both the first excavation bit 121 and the second excavation bit 122 project to both the outside and the inside of the steel pipe body 11, and the pipe thickness center line L of the steel pipe body 11 is centered in the mounting direction. _Since it intersects with _C11 , the distance from which the second excavation bit 122 protrudes is longer than the distance from which the first excavation bit 121 protrudes inside the steel pipe body 11, and excavation is possible than the excavable area R1. Region R2 is expanded. In another example, the excavable area may be extended only on the outside or the inside of the steel pipe body 11.

With the above configuration, the construction resistance is borne by the second excavation bit 222 that excavates the relatively expanded area, and the wear of the first excavation bit 221 whose construction resistance is reduced by that amount is suppressed. be able to. As described above, the wear of the first excavation bit 221 is also suppressed by making the protrusion height H ₂ of the _second excavation bit 222 higher than the protrusion height H _{1 of} the first excavation bit 221. Therefore, in the present embodiment, the wear of the first excavation bit 221 is suppressed more effectively, and the function of suppressing or promoting the blockage of the in-pipe soil by the excavation bit 22 is maintained even if the excavation is advanced in the layer having high ground strength. can do.

Note that the modified examples as described with reference to FIGS. 4 and 5 in the first embodiment described above can also be applied to the present embodiment. Specifically, as shown in the example shown in FIG. 7, an inclination in which the protruding height of the steel pipe body 11 increases from the inside to the outside in the radial direction on at least one of the tip surfaces 221E and 222E of the

excavation bits

221A and 222A. May be formed. Further, as in the example shown in FIG. 8, at least one of the

excavation bits

221 and 222B may be formed with a tapered cross section that becomes thicker from the inside to the outside in the radial direction of the steel pipe body 11.

(Third Embodiment)
FIG. 9 is a view of the steel pipe pile according to the third embodiment of the present invention as viewed from the side and the tip side. As shown in FIG. 6, the steel pipe pile 30 includes a steel pipe main body 11 and a drilling bit 32 attached to an end surface 11E of the steel pipe main body 11. The excavation bit 32 includes a first excavation bit 321 and a second excavation bit 322. Like the first embodiment, by a height _{H 1} protrudes from the end surface 11E of the first drill bit 321 steel body 11, second drill bit 322 by a height _{H 2} protrudes from the end surface 11E of the steel pipe body 11 , Height H ₂ is higher than height H ₁ (H ₁ <H ₂ ). Further, in the present embodiment, the length along the attachment direction of the first excavation bit 321 is L1, the length along the attachment direction of the second excavation bit 322 is L2, and the length L2 is the length. Is longer than L1 (L1 <L2). On the other hand, in the present embodiment, the first excavation bit 321 and the second excavation bit 322 are attached at the same attachment angle θ (0 <θ <90 °) with respect to the circumferential tangent of the steel pipe main body 11. Mounting direction of the first drilling bit 321 and the second drill bit 322, the circumferential tangent of the steel pipe body 11, that is, a direction inclined by fitting angle θ to a tangent _{L T11} of pipe thickness center line _{L C11.}

Since the excavation bit 32 has the mounting angle θ as described above, the steel pipe pile 30 is rotated counterclockwise (CCW) and clockwise (CW) shown in FIG. 9 in the present embodiment as in the first embodiment. When excavating while rotating each of them, the effect of suppressing or promoting the blockage of the soil inside the pipe can be obtained.

In addition, in the present embodiment, the length L2 along the attachment direction of the second excavation bit 322 is longer than the length L1 along the attachment direction of the first excavation bit 321. Thus, even the mounting angle θ of the first drill bit 321 and the second drill bit 322 is the same, for example, the radially outer steel body 11, a first drill bit 321 is the pipe thickness center line L _C11 than the distance D1 which projects in the radial direction of the steel pipe body 11 from Trip distance D2 where the second drill bit 322 protrudes from the wall thickness center line L _C11 in the radial direction of the steel pipe body 11 becomes longer. As a result, on the outside of the steel pipe main body 11, the excavable region R2 of the second excavation bit 322 is expanded more than the excavable region R1 of the first excavation bit 321. For example, regarding the outside of the steel pipe main body 11, when the radius of the excavable region R1 is r1 and the radius of the excavable region R2 is r2 as shown in FIG. 6, the length is about r2 / r1 = 1.2. L1 and L2 may be set.

In the present embodiment, both the first excavation bit 321 and the second excavation bit 322 project to both the outside and the inside of the steel pipe body 11 in the radial direction, and the pipe thickness of the steel pipe body 11 is at the center of the mounting direction. Since it intersects the center line _LC11 , the distance that the second excavation bit 322 protrudes is longer than the distance that the first excavation bit 321 protrudes inside the steel pipe main body 11, and the distance that the second excavation bit 322 protrudes is longer than the excavable area R1. The excavable area R2 is also expanded. In another example, the excavable area may be extended only on either the outside or the inside of the steel pipe body 11 in the radial direction.

With the above configuration, the construction resistance is borne by the second excavation bit 322 that excavates the relatively expanded area, and the wear of the first excavation bit 321 whose construction resistance is reduced by that amount is suppressed. be able to. As described above, the wear of the first excavation bit 321 is also suppressed by making the protrusion height H ₂ of the _second excavation bit 322 higher than the protrusion height H _{1 of} the first excavation bit 321. Therefore, in the present embodiment, the wear of the first excavation bit 321 is more effectively suppressed, and the function of suppressing or promoting the blockage of the in-pipe soil by the excavation bit 32 is maintained even when excavation is carried out in a layer having high ground strength. can do.

The second and third embodiments of the present invention described above can be combined with each other. That is, in the embodiment of the present invention, in addition to making the protrusion height H ₂ of the _second excavation bit 322 higher than the protrusion height H ₁ of the first excavation bit 321, the attachment of some excavation bits. The excavable area may be extended by making either the angle θ or the length L along the mounting direction larger than the other drilling bits, or both the mounting angle θ and the length L may be the other drilling bits. The excavable area may be expanded by making it larger than.

Further, the modified example as described with reference to FIGS. 4 and 5 in the first embodiment described above is also applicable to the present embodiment. Specifically, the tip surface of at least one of the excavation bits may be inclined so that the protruding height increases from the inside to the outside in the radial direction of the steel pipe body, or at least one of the excavation bits is a steel pipe. It may be formed with a tapered cross section that becomes thicker from the inside to the outside in the radial direction of the main body.

(Modification)
10 to 14 are views showing modified examples of the first to third embodiments described above. The modifications described below are applicable to each of the first to third embodiments, and to the embodiment in which the second embodiment and the third embodiment are combined. In the steel pipe pile 40 shown in each figure, the excavation bit 42 includes a first excavation bit 421 and a second excavation bit 422. The protrusion height, the mounting angle θ, or the length L are different between the first excavation bit 421 and the second excavation bit 422 as in the first to third embodiments described above. In each of the drawings of FIGS. 10 to 14, such a difference in shape between the first excavation bit and the second excavation bit is not necessarily shown. Further, in the example shown in each figure, each drilling bit protrudes both outward and inside in the radial direction of the steel pipe body 11 and intersects the pipe thickness center line of the steel pipe body 11 at the center in the mounting direction. Similar to each of the above-described embodiments, the excavation bit may protrude only on either the outer side or the inner side in the radial direction of the main body 11.

In the examples shown in FIGS. 10 and 11, the arrangement pattern of the first excavation bit 421 and the second excavation bit 422 in the circumferential direction of the steel pipe main body 11 is different from each of the above embodiments. More specifically, in each of the above embodiments, the first excavation bit and the second excavation bit are alternately arranged alternately, whereas in the steel pipe pile 40 shown in FIG. 10, the first excavation bit and the second excavation bit are arranged alternately. The first excavation bit 421 and the second excavation bit 422 are alternately arranged every two. Further, in each of the above embodiments, the same number of the first excavation bit and the second excavation bit are arranged, whereas in the steel pipe pile 40 shown in FIG. 11, the first excavation bit 421 is set to 1. Two second excavation bits 422 are arranged for each arrangement, and therefore the number of second excavation bits 422 is greater than the number of first excavation bits 421.

In the example shown in FIG. 12, the drilling bit 42 includes a third drilling bit 423 and a fourth drilling bit 424 in addition to the first drilling bit 421 and the second drilling bit 422. The third drill bit 423 (only protrudes higher third height than the height H ₂ from the other words, the end surface 11E of the steel pipe main body 11) further protruding height greater than the second drill bit 422. Further, a third drill bit 423, the distance to further protrude from the second drill bit 422 is long (i.e., the distance from the wall thickness center line _{L C11} in the radial direction of the steel pipe body 11 of the steel pipe body 11 D2 (FIG. 6 Alternatively, it may have an excavable area extended beyond the excavable area R2 of the second excavation bit 422) by projecting by a third distance longer than (see FIG. 9 and the like). The relationship between the third excavation bit 423 and the fourth excavation bit 424 is the same as the relationship between the second excavation bit 422 and the third excavation bit 423, and the fourth excavation bit 424 is, for example, the first. It may have an excavable area that is even higher than the excavation bit 423 of 3 and further expanded than the excavation bit 423 of the third excavation bit 423. As described above, in the embodiment of the present invention, the excavation bit is not limited to the two types of excavation bits, and may include three types or four or more types of excavation bits. In this case, as for the three or more types of excavation bits, there are excavation bits that bear the construction resistance in advance, such as the second excavation bit 422 and the third excavation bit 423 in the example shown in FIG. This includes an intermediate excavation bit that initially suppresses wear and then bears construction resistance to suppress wear of another excavation bit located later after the preceding excavation bit wears.

In the example shown in FIGS. 13 and 14, the excavation bit 42 including the first excavation bit 421 and the second excavation bit 422 is a curved plate-shaped excavation bit. In the example of FIG. 13, the excavation bit 42 is curved so as to have a C shape when the steel pipe pile 40 is viewed from the tip side. In this case, the mounting angle θ of the drill bit 42, at a position intersecting the wall thickness center line _{L C11} curved thickness center line _{L C42} steel pipe body 11 of the drill bit 42, the tangent of the thickness center line _{L C42} _{L T42} that the angle between the tangential line _{L T11} of pipe thickness center line _{L C11.} Further, the length L along the attachment direction of the excavation bit 42 is the length in the direction along the tangent line _LT42 . In the example of FIG. 13, for example, in addition to obtaining the same effect as in each of the above embodiments, the curved excavation bit 42 causes the steel pipe when the steel pipe pile 40 rotates counterclockwise (CCW). easily create flow F ₁ of the sediment away from the main body 11 and the drill bit 42, also steel pipe pile 40 tends produces a flow F ₂ of sediment towards the inside of the steel pipe body 11 when rotating clockwise (CW). By smoothing the flow of earth and sand, excavation using the steel pipe pile 40 becomes smoother.

On the other hand, in the example of FIG. 14, the excavation bit 42 is curved so as to have an S shape when the steel pipe pile 40 is viewed from the tip side. In this case, the mounting angle θ of the drill bit 42, at a position where the curved thickness center line L _C42 of the drill bit 42 intersects the wall thickness center line L _C11 steel pipe body 11, the thickness center of the opposite ends of the drill bit 42 it is an angle formed by the tangent line _{L T11} linear _{L E42} and pipe thickness center line _{L C11} connecting the. Further, the length L along the attachment direction of the excavation bit 42 is the length in the direction along the straight line _{LE 42} . In the example of FIG. 14, in addition to becoming tends produced examples and similar of sediment flow F _1, F ₂ in FIG. 13, the inside of the steel pipe body 11 when the steel pipe pile 40 is rotated clockwise (CW) captured sediment is likely produced the sediment flow F ₃ direction away from the drill bit 42. Similar to the example of FIG. 13, the smooth flow of earth and sand makes excavation using the steel pipe pile 40 smoother.

In the first to third embodiments described above and their modifications, the excavation bit protrudes both inside and outside the steel pipe body 11, or the excavation bit projects only inside the steel pipe body 11. It can be configured. The direction in which the excavation bit protrudes from the steel pipe body 11 may be different between the first excavation bit and the second excavation bit (and the third excavation bit and the fourth excavation bit).

(Construction method of steel pipe pile)
Using the steel pipe piles according to the embodiments and modifications of the present invention as described above, for example, the following construction methods can be implemented. In the following, the steel pipe pile 10 described with reference to FIG. 1 will be described as an example, but the same construction method can be applied to the steel pipe piles 20, 30, and 40 according to the second and third embodiments and the modified examples. It is feasible.

First, until the tip of the steel pipe pile 10 (the tip of the drilling bit 12 or the end face 11E of the steel pipe body 11) reaches a predetermined depth, the drilling bit 12 pushes the earth and sand to the outside of the steel pipe body 11 in the first rotation direction ( The step of excavating while rotating the steel pipe pile 10 in the counterclockwise direction (CCW) shown in FIG. 1 is carried out. After that, the steel pipe pile 10 is placed in the second rotation direction (clockwise (CW) shown in FIG. 1) in which the excavation bit 12 takes in the earth and sand inside the steel pipe main body 11 until the tip of the steel pipe pile 10 reaches the stopping depth. The process of excavating while rotating is carried out. Here, the predetermined depth is, for example, upward by a distance of about 1 to 5 times the diameter of the steel pipe main body 11 with respect to the stopping depth. As a result, when the steel pipe pile 10 is stopped, the lower end of the steel pipe pile 10 can be closed with the captured earth and sand to obtain a high bearing capacity.

The relationship between the above-mentioned predetermined depth and the depth of the support layer in the ground is arbitrary. That is, the predetermined depth may be deeper than the depth of the support layer. In this case, in the construction method, the tip of the steel pipe pile 10 reaches the support layer at the time of stopping, and then the steel pipe pile 10 is rotated in the second rotation direction. Alternatively, the predetermined depth may be shallower than the depth of the support layer. In this case, in the construction method, at the time of stopping, the steel pipe pile 10 is excavated while rotating in the second rotation direction immediately before the tip of the steel pipe pile 10 reaches the support layer, and the tip of the steel pipe pile 10 is the support layer. Will be stopped after reaching.

Further, in the construction method, the step of excavating while rotating the steel pipe pile 10 in the first rotation direction and the step of excavating while rotating the steel pipe pile 10 in the second rotation direction may be alternately performed. .. That is, even before the tip of the steel pipe pile 10 reaches a predetermined depth, it is possible to excavate the steel pipe pile 10 while rotating it in the second rotation direction. Specifically, for example, when the rooting of the steel pipe pile 10 is not smooth, the steel pipe pile 10 is rooted while alternately switching the rotation direction, and finally the steel pipe pile 10 is set to the second rotation direction. It is conceivable to rotate and stop. In this case, the predetermined depth is the depth at which the steel pipe pile 10 is finally rotated in the first rotation direction, and may be, for example, a depth similar to the stopping depth. For example, in the above case, excavation (lowering of the tip) and retreat (rising of the tip) of the steel pipe pile 10 may be alternately performed as well as the rotation direction of the steel pipe pile 10.

FIG. 15 is a graph showing the experimental results regarding the mounting angle of the excavation bit. In the experiment, excavation bits having a thickness of 6 mm, a length of 30 mm along the mounting direction, and a protrusion height of 12 mm from the end face of the steel pipe body were placed at equal intervals on a steel pipe body having a cross-sectional diameter of 101.6 mm and a pipe thickness of 5.7 mm. When the mounting angle of the excavation bit is 0 ° (no mounting angle), 5 °, 15 °, 20 ° and 30 °, hit the simulated ground using Iitoyo silica sand No. 7 to the same depth. The bearing capacity of the installed steel pipe piles was compared. In this experiment, the load when the amount of sinking of the pile head (steel pipe head) is 10% of the pile diameter (cross-sectional diameter) is based on the "Road Bridge Specification / Explanation (IV Substructure)". (Ultimate bearing capacity) is the bearing capacity. Further, the bearing capacity is expressed by an increase rate when 1 is set when there is no mounting angle. As shown in the graph of FIG. 15, when there is a mounting angle (greater than 0 °), the bearing capacity is improved as compared with the case where there is no mounting angle. In particular, when the mounting angle was in the range of 5 ° to 15 °, a more remarkable improvement in bearing capacity was observed (about 1.25 times or more in the case of 0 °). From this result, for example, in each of the above-described embodiments, even if the mounting angles θ, θ1, θ2 of the excavation bit are set in the range of 5 ° or more and 15 ° or less (5 ° ≦ θ, θ1, θ2 ≦ 15 °). Good. Since the bearing capacity is improved even outside the above range, the values of the mounting angles θ, θ1 and θ2 are not limited to the above range.

FIG. 16 is a diagram for explaining an experiment for verifying the wear suppressing effect of the excavation bit. As shown in the experiment, in the experiment,

excavation bits

121 and 122 having a thickness of 3.2 mm and a length of 30 mm along the mounting direction were equally spaced on a steel pipe body 11 having a cross-sectional diameter of 101.6 mm and a pipe thickness of 5.7 mm. I installed four. In the first embodiment, two of the excavation bits 121 have a protrusion height of 10 mm from the end face of the steel pipe body, and the remaining two excavation bits 122 have a protrusion height of 14 mm, and the excavation bit 121 and the

excavation bit

122 and 122 were alternately arranged in the circumferential direction of the steel pipe main body 11. The mounting angle of the excavation bit is 10 °. In the second embodiment, in addition to the difference in the protrusion height of the first embodiment, the mounting angle of the excavation bit 121 is set to 10 °, and the mounting angle of the excavation bit 122 is set to 15 °. The

excavation bits

121 and 122 both project to both the outside and the inside of the steel pipe body 11 and intersect the pipe thickness center line of the steel pipe body 11 at the center in the mounting direction. Note that FIG. 16 shows the conditions of the second embodiment. In the comparative example, four excavation bits were similarly attached, but the protrusion height was 12 mm and the attachment angle was 10 ° for all the excavation bits.

FIG. 17 is a graph showing the results of the experiment shown in FIG. A mortar-shaped model ground was excavated at a construction depth of 500 mm with the steel pipe piles according to Examples 1, 2 and Comparative Examples as described with reference to FIG. As a result, as shown in the graph, when the volume residual ratio of each bit in the comparative example in which the mounting angle and the excavable area are the same for all the excavation bits is 1, two sets of excavations having different protrusion heights are excavated. In Example 1 in which the bits were arranged, the volume residual ratio of the excavation bit 121 having a low protrusion height was 4.85 times that of the comparative example. Here, the volume residual ratio is the ratio of the volume of the excavation bit remaining after the construction to the volume of the excavation bit before the construction. Further, in Example 2 in which the excavable area is different in addition to the protruding heights of the two sets of excavating bits, the volume residual ratio of the excavating bits 121 having a low protruding height and a small excavable area is 5.23 times that of the comparative example. there were. The result is that the function of the excavation bit can be maintained against wear during excavation by making the projecting height different among multiple excavation bits, and the size of the excavable area in addition to the projecting height. It is shown that the effect is improved by making them different.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. It is naturally understood that these also belong to the technical scope of the present invention.

10, 20, 30, 40 ... Steel pipe pile, 11 ... Steel pipe body, 11E ... End face, 12, 22, 32, 42 ... Excavation bit, 121, 121A, 221,221A, 321, 421 ... First excavation bit, 121E , 221E ... Tip surface, 122, 122A, 122B, 222, 222A, 222B, 322, 422 ... Second drilling bit, 122E, 222E ... Tip surface, 423 ... Third drilling bit, 424 ... Fourth drilling bit ..

Claims

A steel pipe pile provided with a steel pipe body and a plate-shaped excavation bit that is attached to the end surface of the steel pipe body at an angle with respect to the circumferential tangent of the steel pipe body and projects in the axial direction of the steel pipe body.
The excavation bit
A first excavation bit protruding from the end face of the steel pipe body by a first height in the axial direction of the steel pipe body,
A steel pipe pile including a second excavation bit that protrudes from the end face of the steel pipe body by a second height higher than the first height in the axial direction of the steel pipe body.
Claim 1 in which the tip surface of at least one of the first excavation bit or the second excavation bit is formed with an inclination in which the protruding height increases from the inside to the outside in the radial direction of the steel pipe body. Steel pipe pile described in.
The first or second excavation bit, wherein at least one of the first excavation bit or the second excavation bit is formed in a tapered cross section that becomes thicker from the inside to the outside in the radial direction of the steel pipe body. Steel pipe pile.
Claims 1 to 3 further include a third excavation bit in which the excavation bit protrudes from the end surface of the steel pipe body by a third height higher than the second height in the axial direction of the steel pipe body. The steel pipe pile according to any one of the above.
The steel pipe according to any one of claims 1 to 4, wherein the excavation bit has a plate shape curved so as to have a C-shape or an S-shape when the steel pipe pile is viewed from the tip side. Pile.
The excavation bit protrudes at least either outward or inside in the radial direction of the steel pipe body.
The first excavation bit has a first excavable region by projecting from the pipe thickness center line of the steel pipe body by a first distance in the radial direction of the steel pipe body.
The second excavation bit protrudes from the pipe thickness center line of the steel pipe body by a second distance longer than the first distance in the radial direction of the steel pipe body, thereby extending the outside of the steel pipe body in the radial direction. The steel pipe pile according to any one of claims 1 to 5, which has a second excavable area that is expanded from the first excavable area at least on the inner side.
The first excavation bit is attached at a first angle with respect to the circumferential tangent of the steel pipe body.
The steel pipe pile according to claim 6, wherein the second excavation bit is attached at a second angle larger than the first angle with respect to the circumferential tangent of the steel pipe body.
The first excavation bit has a first length along the mounting direction of the first excavation bit.
The steel pipe pile according to claim 6 or 7, wherein the second excavation bit has a second length longer than the first length along the attachment direction of the second excavation bit.
The method for constructing a steel pipe pile according to any one of claims 1 to 8.
A step of excavating while rotating the steel pipe pile in the first rotation direction in which the excavation bit pushes earth and sand to the outside of the steel pipe body until the tip of the steel pipe pile reaches a predetermined depth.
Construction of a steel pipe pile including a step of excavating the steel pipe pile while rotating the steel pipe pile in a second rotation direction in which the excavation bit takes in earth and sand inside the steel pipe body until the tip of the steel pipe pile reaches the stopping depth. Method.
The method for constructing a steel pipe pile according to claim 9, wherein the tip of the steel pipe pile reaches the support layer at the time of stopping, and then the steel pipe pile is rotated in the second rotation direction.
At the time of the stop, immediately before the tip of the steel pipe pile reaches the support layer, the steel pipe pile is excavated while rotating in the second rotation direction, and the tip of the steel pipe pile reaches the support layer. The method for constructing a steel pipe pile according to claim 9, which is stopped from.
9 to claims, wherein the step of excavating while rotating the steel pipe pile in the first rotation direction and the step of excavating while rotating the steel pipe pile in the second rotation direction are alternately performed. The method for constructing a steel pipe pile according to any one of 11.