JP7192963B2 - Steel pipe piles and construction methods for steel pipe piles - Google Patents

Description

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

Excavation bits attached to the ends of steel pipe piles are expected not only to have the conventional effect of excavating the ground, but also to control the movement of the excavated soil according to the rotation direction of the pile, and to suppress or promote clogging with soil inside the pipe. be. For example, in Patent Document 1, the tangential direction at the intersection of the longitudinal center axis of the drilling bit and the outer circumference of the steel pipe pile forms an angle, and this angle causes the cutting edge of the drilling bit to move toward the inside of the steel pipe pile. The technology provided is described. As a result, for example, before the pile tip reaches the bearing layer, the earth and sand are pushed out of the pile to suppress clogging of the soil inside the pipe, thereby improving excavability, and after the pile tip reaches the bearing 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 a high bearing capacity can be obtained by promoting the clogging of the soil inside the pipe.

Japanese Patent No. 5053154

However, when penetrating the tip of a steel pipe pile into the bearing layer, a large construction resistance (rotational torque and vertical press force) acts on the drill bit attached to the tip of the pile due to the high strength of the ground. It is expected to wear out. Therefore, in order to maximize the effect of the drilling bit described in Patent Document 1, for example, it is desirable to have a structure that can maintain the function of the drilling bit against wear.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a new and improved steel pipe pile and a steel pipe pile construction method capable of maintaining the function of an excavation bit against wear during excavation.

[1] A steel pipe pile comprising a steel pipe body and a plate-shaped drilling bit attached to an end surface of the steel pipe body at an angle with respect to a circumferential tangent line of the steel pipe body and protruding in the axial direction of the steel pipe body, the drilling bit a first drilling bit protruding from the end face of the steel pipe body in the axial direction of the steel pipe body by a 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. and a second drill bit projecting by .
[2] A tip surface of at least one of the first drilling bit and the second drilling bit is formed with an inclination that protrudes from the inside to the outside in the radial direction of the steel pipe body, [1] The steel pipe pile described in .
[3] According to [1] or [2], wherein at least one of the first drilling bit and the second drilling bit is formed with a tapered cross-section that becomes thicker from the radially inner side to the outer side of the steel pipe body. steel pipe piles.
[4] of [1] to [3], wherein the drill bit further includes a third drill bit that protrudes from the end face of the steel pipe body in the axial direction of the steel pipe body by a third height that is higher than the second height. The steel pipe pile according to any one of items 1 and 2.
[5] The drill bit according to any one of [1] to [4], which has a plate shape that is curved into a C-shape or an S-shape when the steel pipe pile is viewed from the tip side. Steel pipe pile.
[6] The drilling bit protrudes radially outwardly or inwardly of the steel pipe body, and the first drilling bit protrudes radially of the steel pipe body by a first distance from the pipe thickness center line of the steel pipe body. and the second drill bit protrudes from the pipe thickness center line of the steel pipe body in the radial direction of the steel pipe body by a second distance that is longer than the first distance. , having a second excavable area that is wider than the first excavable area on at least one of the radially outer side and inner side of the steel pipe body, according to any one of [1] to [5]. Steel pipe pile.
[7] The first drill bit is mounted at a first angle to the circumferential tangent of the steel pipe body, and the second drill bit is greater than the first angle to the circumferential tangent of the steel pipe body. The steel pipe pile according to [6], mounted at a second angle.
[8] The first drill bit has a first length along the mounting direction of the first drill bit and the second drill bit has a first length along the mounting direction of the second drill bit. The steel pipe pile according to [6] or [7], having a second length longer than the length of.
[9] The steel pipe pile construction method according to any one of [1] to [8], wherein 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. a step of excavating while rotating the steel pipe pile in the first direction of rotation to push it out; A steel pipe pile construction method including a step of excavating while rotating the pile.
[10] The construction method of the steel pipe pile according to [9], wherein the steel pipe pile is rotated in the second rotation direction after the tip of the steel pipe pile reaches the support layer when the steel pipe pile is stopped.
[11] During ramming, 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 ramming is performed after the tip of the steel pipe pile reaches the support layer. , The construction method of the steel pipe pile according to [9].
[12] 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 [9] to [11] Construction method of the steel pipe pile according to any one of.

According to the above configuration, it is possible to make the second drilling bit having a higher projecting height bear the working resistance, thereby suppressing the wear of the first drilling bit accordingly. Therefore, the function of the drill bit can be maintained against wear during drilling.

BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which looked at the steel pipe pile which concerns on the 1st Embodiment of this invention from the side and front end side. It is a figure which shows the modification of the steel pipe pile shown in FIG. It is a figure which shows the modification of the steel pipe pile shown in FIG. It is a figure which shows another example of the steel pipe pile which concerns on the 1st Embodiment of this invention. It is a figure which shows another example of the steel pipe pile which concerns on the 1st Embodiment of this invention. It is the figure which looked at the steel pipe pile concerning the 2nd Embodiment of this invention from the side and front end side. It is a figure which shows another example of the steel pipe pile which concerns on the 2nd Embodiment of this invention. It is a figure which shows another example of the steel pipe pile which concerns on the 2nd Embodiment of this invention. It is the figure which looked at the steel pipe pile concerning the 3rd Embodiment of this invention from the side and front end side. It is a figure which shows the modification of 1st and 2nd embodiment. It is a figure which shows the modification of 1st and 2nd embodiment. It is a figure which shows the modification of 1st and 2nd embodiment. It is a figure which shows the modification of 1st and 2nd embodiment. It is a figure which shows the modification of 1st and 2nd embodiment. 4 is a graph showing experimental results regarding mounting angles of drilling bits. FIG. 10 is a diagram for explaining an experiment for verifying the effect of suppressing wear of a drilling bit; 17 is a graph showing the results of the experiment shown in FIG. 16;

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

(First embodiment)
FIG. 1 : is the figure which looked at the steel pipe pile which concerns on the 1st Embodiment of this invention from the side and front end side. As shown in FIG. 1 , the steel pipe pile 10 includes a steel pipe body 11 and an excavation bit 12 attached to an end face 11E of the steel pipe body 11 and protruding in the axial direction of the steel pipe body 11 . Drill bit 12 includes first drill bit 121 and second drill bit 122 . In this embodiment, the first drilling bit 121 and the second drilling bit 122 are both attached at an angle θ (0<θ<90°) with respect to the circumferential tangent line of the steel pipe body 11 . _{Here ,} the _{angle ?} It is the angle formed by the tangent line L _T11 (the circumferential tangent line of the steel pipe body 11). The angle θ is hereinafter also referred to as the attachment angle of the excavation bit 12 . The mounting directions of the first drilling bit 121 and the second drilling bit 122 are directions inclined by the respective mounting angles θ1 and θ2 with respect to the circumferential tangent line of the steel pipe body 11 .

In this embodiment, since the excavation bit 12 has an attachment angle θ, for example, when excavating using the steel pipe pile 10, the steel pipe pile 10 is rotated counterclockwise as shown in FIG. 1 until the tip of the pile reaches a predetermined depth. It is possible to excavate while rotating (CCW) to push out the earth and sand to the outside of the steel pipe body 11, thereby suppressing clogging of the pipe interior with earth. In addition, until the tip of the pile reaches the slamming depth, excavate while rotating the steel pipe pile 10 clockwise (CW) shown in FIG. By doing so, high bearing capacity can be obtained. The excavation bit 12 has edges on both the radially inner side and the outer side of the steel pipe body 11, thereby enabling excavation by reversing the direction of rotation of the steel pipe body 11 as described above.

In the present embodiment, both the first drilling bit 121 and the second drilling bit 122 protrude both radially outward and inward of the steel pipe body 11, and the thickness of the steel pipe body 11 is reduced at the center in the mounting direction. It intersects the center line L _C11 . In another embodiment, as in the examples shown in FIGS. 2 and 3 , the drilling bit may protrude either radially outward or radially inward of the steel pipe body 11 .

Furthermore, in the present embodiment, the first drilling bit 121 of the drilling bits 12 protrudes from the end surface 11E of the steel pipe body 11 in the axial direction of the steel pipe body 11 by a height H1, and the _second drilling bit 122 protrudes from the steel pipe body 11 in the axial direction. end face 11E in the axial direction of the steel pipe body ₁₁ by _a height H2, and the height H2 is higher _than the height H1 ₍ H1 < _H2 ). For example, when a layer with high ground strength such as a support layer is excavated, it is assumed that the excavation bit 12 is worn out due to a large construction resistance acting on the excavation bit 12 . On the other hand, by making the projecting height H2 of the _second drilling bit 122 higher than the projecting height H1 of the _first drilling bit 121 as described above, the preceding second drilling bit in drilling 122 bears the construction resistance, and the wear of the first excavation bit 121, whose construction resistance is reduced by that amount, can be suppressed. The wear of the first drilling bit 121 becomes conspicuous after, for example, the protrusion height of the second drilling bit 122 becomes approximately the same as that of the first drilling bit 121 due to wear. There may be cases where the wear of one drilling bit 121 is not noticeable. By suppressing the wear of the first excavation bit 121 in this way, even if excavation proceeds in a layer with high ground strength, the function of suppressing or promoting clogging of the pipe interior soil by the excavation bit 12 as described above can be achieved. can be maintained.

The method of attaching the drilling bit 12 to the steel pipe body 11 may be, for example, welding or mechanical joining means such as screwing. In the example shown in FIG. 1, the end surface 11E of the steel pipe body 11 and the upper end surface of the drilling bit 12 are aligned, but the drilling bit 12 may be fitted into a groove or notch formed in the end surface 11E. , the end including the end surface 11E of the steel pipe body 11 is fitted into the groove or notch formed in the upper end surface of the drilling bit 12, and the end surface 11E and the upper end surface of the drilling bit 12 are joined together. It is also possible to form grooves or cuts in both of and to fit these grooves or cuts into each other and then join them. In this case, the end face 11E of the steel pipe body 11 and the upper end face of the drill bit 12 do not necessarily match. The same applies to 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, similar to the example described above with reference to FIG. Also, the protrusion height H2 of the _second drilling bit 122A is higher than the protrusion height H1 of the _first drilling bit 121A. In addition, in the illustrated example, the tip surfaces 121E and 122E of the first drilling bit 121A and the second drilling bit 122A, that is, the end surfaces of the steel pipe body 11 opposite to the end surface 11E, are provided with the radial direction of the steel pipe body 11. A slope is formed in which the protrusion height increases from the inside to the outside.

By forming the slopes on the tip surfaces 121E and 122E of the first drilling bit 121A and the second drilling bit 122A as described above, when the steel pipe body 11 is rotated clockwise (CW) shown in FIG. The protruding height of the first drilling bit 121A and the second drilling bit 122A is higher in the portion that comes into contact with the earth and sand ahead, and the resistance to wear of the first drilling bit 121A and the second drilling bit 122A is increased. can be improved. Note that the projecting heights H ₁ and H ₂ of the first drilling bit 121A and the second drilling bit 122A are, for example, the heights from the end surface 11E to the highest positions of the inclined tip surfaces 121E and 122E as shown in the figure. can be defined as Also, in the illustrated example, both the tip end surfaces 121E and 122E of the first drilling bit 121A and the second drilling bit 122A are inclined, but only one of the tip end faces is inclined. good too.

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, similar to the example described above with reference to FIG. Also, the protrusion height H2 of the _second drilling bit 122B is higher than the protrusion height H1 of the _first drilling bit 121 . In addition, in the illustrated example, the second drilling bit 122B is formed with a tapered cross section that becomes thicker from the radially inner side to the outer side of the steel pipe body 11 . Specifically, the second drilling bit 122B has a thickness t ₁ on the radially inner side of the steel pipe body 11 and a thickness t ₂ on the outer side, and the thickness t ₂ is greater than the thickness t ₁ (t ₁ < _t2 ).

By forming the second excavation bit 122B with a tapered cross-section as described above, when the steel pipe body 11 is rotated clockwise (CW) shown in FIG. The drill bit 122B may be thicker to improve the wear resistance of the second drill bit 122B. In the illustrated example, only the second drilling bit 122B is formed with a tapered cross section, but both the first drilling bit 121 and the second drilling bit 122B may be formed with a tapered cross section. Only one drilling bit 121 may be formed with a tapered cross-section. Further, by combining the example of FIG. 5 and the example of FIG. 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 seen from the side and tip side. As shown in FIG. 6 , the steel pipe pile 20 includes a steel pipe body 11 and an excavation bit 22 attached to the end surface 11E of the steel pipe body 11 . Drilling bits 22 include a first drilling bit 221 and a second drilling bit 222 . As in the first embodiment, the first drill bit 221 protrudes from the end face 11E of the steel pipe body 11 by a height H1, and the _second drill bit 222 protrudes from the end face 11E of the steel pipe body ₁₁ by a height H2. , the height H ₂ is higher than the height H ₁ (H ₁ <H ₂ ). Furthermore, in this embodiment, the first drilling bit 221 is attached at an angle θ1 (0<θ1<90°) with respect to the tangent line in the circumferential direction of the steel pipe body 11, and the second drilling bit 222 is attached to the circumferential direction of the steel pipe body 11. It is mounted at an angle θ2 (0<θ2<90°) with respect to the direction tangent, and the angle θ2 is greater than the angle θ1 (θ1<θ2). Here, the mounting angles θ1 and θ2 are similar to the mounting angles θ described in the first embodiment, and are the plate thickness center lines L _C221 and L of the first drilling bit 221 and the second drilling bit 222, respectively. It is the angle between _C222 and the tangent line L _T11 to the pipe thickness center line L _C11 of the steel pipe body 11 , that is, the circumferential tangent line of the steel pipe body 11 . On the other hand, in this embodiment, the length L along the mounting direction of each of the first drilling bit 121 and the second drilling bit 122 is the same. The mounting directions of the first drilling bit 221 and the second drilling bit 222 are directions inclined by the respective mounting angles θ1 and θ2 with respect to the circumferential tangent line of the steel pipe body 11 .

Since the drilling bit 22 has the mounting angles θ1 and θ2 as described above, the steel pipe pile 20 is rotated counterclockwise (CCW) and clockwise (CW) in this embodiment as in the first embodiment. ), the effect of suppressing or promoting clogging of the pipe with soil can be obtained when excavating while rotating each of the pipes.

Additionally, in this embodiment, the mounting angle θ2 of the second drilling bit 222 is greater than the mounting angle θ1 of the first drilling bit 221 . As a result, even if the length L along the installation direction of the first drilling bit 221 and the second drilling bit 222 is the same, for example, the first drilling bit 121 is located on the outside of the steel pipe body 11 at the center of the pipe thickness. The distance D2 by which the second drilling bit 122 protrudes radially of the steel pipe body 11 from the pipe thickness center line L _C11 is longer than the distance D1 by which the steel pipe body 11 protrudes radially from the line L _C11 . As a result, the excavable area R2 of the second excavating bit 222 is expanded beyond the excavable area R1 of the first excavating bit 221 outside the steel pipe body 11 . Here, the excavable areas R1 and R2 are annular areas where the first excavation bit 221 and the second excavation bit 222 respectively excavate earth and sand when the steel pipe pile 20 is rotated in the ground. For example, with respect to the outside of the steel pipe body 11, as shown in FIG. 6, when r1 is the radius of the excavable region R1 and r2 is the radius of the excavable region R2, the mounting angle is such that r2/r1=about 1.2. θ1 and θ2 may be set.

In this embodiment, both the first drilling bit 121 and the second drilling bit 122 protrude to both the outside and the inside of the steel pipe body 11, and are located at the center of the installation direction along the pipe thickness center line L of the steel pipe body 11. Since it intersects with _C11 , similarly inside the steel pipe body 11, the distance that the second drilling bit 122 protrudes is longer than the distance that the first drilling bit 121 protrudes, and excavation is possible more than the excavable region R1. Region R2 is extended. In another example, the excavable area may be expanded only on either the outside or the inside of the steel pipe body 11 .

With the above configuration, the second drilling bit 222 that drills a relatively expanded area bears the working resistance, and the wear of the first drilling bit 221 that reduces the working resistance is suppressed accordingly. be able to. Wear of the first drilling bit 221 is also suppressed by making the protrusion height H2 of the _second drilling bit 222 higher than the protrusion height H1 of the _first drilling bit 221, as described above. Therefore, in the present embodiment, the wear of the first excavation bit 221 is more effectively suppressed, and even if excavation proceeds in a layer with high ground strength, the excavation bit 22 maintains the function of suppressing or promoting clogging of the soil inside the pipe. can do.

Note that the modifications described with reference to FIGS. 4 and 5 in the first embodiment can also be applied to this embodiment. Specifically, as in the example shown in FIG. 7, at least one of the tip end surfaces 221E and 222E of the excavation bits 221A and 222A has an inclination that protrudes from the inside to the outside in the radial direction of the steel pipe body 11. may be formed. Further, as in the example shown in FIG. 8 , at least one of the drilling bits 221 and 222B may be formed with a tapered cross section that becomes thicker from the radially inner side to the outer side 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 seen from the side and tip side. As shown in FIG. 6 , the steel pipe pile 30 includes a steel pipe body 11 and an excavation bit 32 attached to the end surface 11E of the steel pipe body 11 . Drilling bits 32 include a first drilling bit 321 and a second drilling bit 322 . As in the first embodiment, the first drilling bit 321 protrudes from the end face 11E of the steel pipe body 11 by a height H1, and the _second drilling bit 322 protrudes from the end face 11E of the steel pipe body ₁₁ by a height H2. , the height H ₂ is higher than the height H ₁ (H ₁ <H ₂ ). Furthermore, in this embodiment, the length along the mounting direction of the first drilling bit 321 is L1, the length along the mounting direction of the second drilling bit 322 is L2, and the length L2 is the length longer than L1 (L1<L2). On the other hand, in the present embodiment, the first drilling bit 321 and the second drilling bit 322 are attached at the same attachment angle θ (0<θ<90°) with respect to the circumferential tangent line of the steel pipe body 11 . The mounting direction of the first drilling bit 321 and the second drilling bit 322 is a direction inclined by an installation angle θ with respect to the circumferential tangent line of the steel pipe body 11, that is, the tangent line _LT11 of the pipe thickness center line _LC11 .

Since the drilling 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 this embodiment as in the first embodiment. When excavating while rotating each, the effect of suppressing or promoting clogging of the pipe interior soil can be obtained.

In addition, in this embodiment, the length L2 along the mounting direction of the second drilling bit 322 is longer than the length L1 along the mounting direction of the first drilling bit 321 . As a result, even if the attachment angles θ of the first drilling bit 321 and the second drilling bit 322 are the same, the first drilling bit 321 is located on the pipe thickness center line _LC11 on the radially outer side of the steel pipe body 11, for example. The distance D2 by which the second drilling bit 322 protrudes in the radial direction of the steel pipe body 11 from the pipe thickness center line _LC11 is longer than the distance D1 by which the steel pipe body 11 radially protrudes from the center line LC11. As a result, the excavable area R2 of the second excavating bit 322 is expanded beyond the excavable area R1 of the first excavating bit 321 outside the steel pipe body 11 . For example, regarding the outer side of the steel pipe main body 11, as shown in FIG. L1 and L2 may be set.

In the present embodiment, both the first drilling bit 321 and the second drilling bit 322 protrude both radially outward and inward of the steel pipe body 11, and the thickness of the steel pipe body 11 is reduced at the center in the mounting direction. Since it intersects with the center line _LC11 , the distance by which the second drilling bit 322 protrudes is longer than the distance by which the first drilling bit 321 protrudes inside the steel pipe body 11 as well, and the distance by which the second drilling bit 322 protrudes is longer than the excavable region R1. Also, the excavable region R2 is expanded. In another example, the excavable area may be expanded only on either the radially outer side or the inner side of the steel pipe body 11 .

With the above configuration, the second drilling bit 322 that drills a relatively expanded area bears the working resistance, and the wear of the first drilling bit 321 that reduces the working resistance is suppressed accordingly. be able to. Wear of the first drilling bit 321 is also suppressed by making the protrusion height H2 of the _second drilling bit 322 higher than the protrusion height H1 of the _first drilling bit 321, as described above. Therefore, in this embodiment, the wear of the first excavation bit 321 is more effectively suppressed, and even if excavation proceeds in a layer with high ground strength, the excavation bit 32 maintains the function of suppressing or promoting clogging of the soil inside the pipe. can do.

It should be noted that 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 H2 of the _second drilling bit 322 higher than the protrusion height H1 of the _first drilling bit 321, the installation of some drilling 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 made larger than the other drilling bits. The excavable area may be extended by making it larger than .

Moreover, the modifications described with reference to FIGS. 4 and 5 in the first embodiment can also be applied to this embodiment. Specifically, the tip surface of at least one of the drilling bits may be formed with an inclination in which the protrusion height increases from the radially inner side to the outer side of the steel pipe body, and at least one of the drilling bits may be formed with the steel pipe. It may be formed with a tapered cross section that becomes thicker from the radially inner side to the outer side of the main body.

(Modification)
10 to 14 are diagrams showing modifications of the first to third embodiments described above. Modifications described below can be applied to each of the first to third embodiments, and to an embodiment combining the second and third embodiments. In the steel pipe pile 40 shown in each figure, the drilling bits 42 include a first drilling bit 421 and a second drilling bit 422 . Between the first drilling bit 421 and the second drilling bit 422, the projection height, mounting angle θ, or length L are different, as in the first to third embodiments described above. 10 to 14 do not necessarily show such a difference in shape between the first drilling bit and the second drilling bit. In the examples shown in the figures, each drilling bit protrudes both radially outward and inward of the steel pipe body 11 and intersects the thickness center line of the steel pipe body 11 at the center in the installation direction. As in the above embodiments, the drilling bit may protrude either radially outward or radially inward of the body 11 .

In the examples shown in FIGS. 10 and 11, the arrangement pattern of the first drilling bits 421 and the second drilling bits 422 in the circumferential direction of the steel pipe body 11 is different from the above embodiments. More specifically, while the first drilling bits and the second drilling bits are alternately arranged in each of the above-described embodiments, in the steel pipe pile 40 shown in FIG. One drilling bit 421 and a second drilling bit 422 are alternately arranged. In addition, while the same number of first excavation bits and second excavation bits are arranged in each of the above embodiments, in the steel pipe pile 40 shown in FIG. Two second drilling bits 422 are placed for every second drilling bit 422 placed, so there are more second drilling bits 422 than first drilling bits 421 .

In the example shown in FIG. 12, drilling bit 42 includes third drilling bit 423 and fourth drilling bit 424 in addition to first drilling bit 421 and second drilling bit 422 . The third drilling bit 423 has a higher protrusion height than the second drilling bit 422 (that is, it protrudes from the end face 11E of the steel pipe body 11 by a third height higher _than the height H2). Furthermore, the third drilling bit 423 protrudes by a longer distance than the second drilling bit 422 (that is, from the pipe thickness center line _LC11 of the steel pipe body 11 in the radial direction of the steel pipe body 11 by a distance D2 (Fig. 6). or project a third distance longer than (see FIG. 9, etc.) to have an excavable area expanded beyond the excavable area R2 of the second drill bit 422. The relationship between the third drilling bit 423 and the fourth drilling bit 424 is the same as the relationship between the second drilling bit 422 and the third drilling bit 423. The protruding height is higher than that of the third drilling bit 423 and the excavable area may be expanded further than that of the third drilling bit 423 . Thus, in the embodiment of the present invention, the drilling bits are not limited to two types, but may include three, four or more types of drilling bits. In this case, there are three or more types of drilling bits, such as the second drilling bit 422 and the third drilling bit 423 in the example shown in FIG. This includes an intermediate drilling bit that initially wears under control and, after the preceding drilling bit wears out, bears the installation resistance in order to control the wear of another drilling bit located later.

In the example shown in FIGS. 13 and 14, the drilling bits 42 including the first drilling bit 421 and the second drilling bit 422 are curved plate-shaped drilling bits. In the example of FIG. 13, the excavation bit 42 is curved into a C shape when the steel pipe pile 40 is viewed from the tip side. In this _case , the _{mounting angle ?} and the tangent line _LT11 to the pipe thickness center line _LC11 . Also, the length L along the mounting direction of the drilling bit 42 is the length along the tangent line _LT42 . In the example of FIG. 13, in addition to obtaining the same effects as those of the above-described embodiments, for example, the curving of the drilling bit 42 allows the steel pipe pile 40 to rotate counterclockwise (CCW). A flow F1 of earth and sand away from the main body 11 and the drilling bit 42 is easily generated, and _a flow F2 of earth and sand toward the inside of the steel pipe body ₁₁ is easily generated when the steel pipe pile 40 rotates clockwise (CW). Excavation using the steel pipe pile 40 becomes smoother due to the smooth flow of earth and sand.

On the other hand, in the example of FIG. 14, the excavation bit 42 is curved in an S shape when the steel pipe pile 40 is viewed from the tip side. In this case, the mounting angle θ of the drilling bit 42 is set so that the thickness center of both ends of the drilling bit 42 is at the position where the curved plate thickness centerline _LC42 of the drilling bit 42 intersects the pipe thickness centerline _LC11 of the steel pipe body 11. This is the angle formed by the connecting straight line _LE42 and the tangent line _LT11 to the pipe thickness center line _LC11 . Also, the length L along the mounting direction of the drilling bit 42 is the length along the straight line _LE42 . In the example of FIG. 14, in addition to being likely to generate the same earth and sand flows F ₁ and F ₂ as in the example of FIG. The sediment that is taken in tends to produce a sediment flow F3 _directed away from the excavation bit 42 . As in the example of FIG. 13 , excavation using the steel pipe pile 40 becomes smoother due to the smooth flow of earth and sand.

In the above-described first to third embodiments and modifications thereof, the drilling bit protrudes both inside and outside the steel pipe body 11, or the drilling bit protrudes only inside the steel pipe body 11. It is configurable. The directions in which the drilling bits protrude from the steel pipe body 11 may differ between the first drilling bit and the second drilling bit (and the third drilling bit and the fourth drilling bit).

(Construction method for steel pipe piles)
For example, the following construction methods can be implemented using the steel pipe piles according to the embodiments and modifications of the present invention as described above. In the following, the steel pipe pile 10 described with reference to FIG. 1 will be described as an example. It is possible.

First, until the tip of the steel pipe pile 10 (the tip of the drilling bit 12 or the end surface 11E of the steel pipe body 11) reaches a predetermined depth, the drilling bit 12 pushes out 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 counterclockwise (CCW) shown in FIG. 1 is performed. After that, until the tip of the steel pipe pile 10 reaches the ramming depth, the drill bit 12 takes the earth and sand inside the steel pipe body 11 in the second rotation direction (clockwise (CW) shown in FIG. 1). A step of excavating while rotating is performed. Here, the predetermined depth is, for example, a distance of about 1 to 5 times the diameter of the steel pipe body 11 above the stop depth. As a result, when the steel pipe pile 10 is driven down, the lower end of the steel pipe pile 10 is blocked with the sediment that has been taken in, and a high bearing capacity can be obtained.

The relationship between the 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 steel pipe pile 10 is rotated in the second rotation direction after the tip of the steel pipe pile 10 reaches the support layer during the anchoring. Alternatively, the predetermined depth may be shallower than the depth of the support layer. In this case, in the construction method, immediately before the tip of the steel pipe pile 10 reaches the support layer, excavation is performed while rotating the steel pipe pile 10 in the second rotation direction, and the tip of the steel pipe pile 10 reaches 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 while rotating the steel pipe pile 10 in the second rotation direction. Specifically, for example, when the embedding of the steel pipe pile 10 is not smooth, the steel pipe pile 10 is embedded while alternately switching the rotation direction, and finally the steel pipe pile 10 is rotated in the second rotation direction. It is conceivable to stop it by rotating it. In this case, the predetermined depth is the depth at which the steel pipe pile 10 was last rotated in the first direction of rotation, and can be, for example, the same depth as the stop depth. For example, in the above case, not only the direction of rotation of the steel pipe pile 10 but also excavation (lowering of the tip) and retreat (rising of the tip) of the steel pipe pile 10 may be performed alternately.

FIG. 15 is a graph showing experimental results regarding the mounting angle of the drilling bit. In the experiment, a steel pipe body with a cross-sectional diameter of 101.6 mm and a pipe thickness of 5.7 mm was provided with 4 drilling bits with a thickness of 6 mm, a length of 30 mm along the installation direction, and a protrusion height of 12 mm from the end face of the steel pipe body. 1, and when the mounting angle of the drilling bit is 0° (no mounting angle), 5°, 15°, 20°, and 30° The bearing capacity of the installed steel pipe piles was compared. In addition, in this experiment, the load ( Ultimate bearing capacity) is the bearing capacity. Moreover, the supporting force is expressed as an increase ratio when the case where there is no mounting angle is set to 1. As shown in the graph of FIG. 15, with a mounting angle (greater than 0°) the bearing capacity is better than without a mounting angle. In particular, when the mounting angle was in the range of 5° to 15°, a more significant improvement in the bearing capacity was observed (approximately 1.25 times or more that in the case of 0°). From these results, for example, in each of the above-described embodiments, even if the mounting angles θ, θ1, θ2 of the drill bit are set within the range of 5° or more and 15° or less (5°≦θ, θ1, θ2≦15°), good. The values of the mounting angles .theta., .theta.1, .theta.2 are not limited to the above ranges because the supporting force is improved even when the angles are outside the above ranges.

FIG. 16 is a diagram for explaining an experiment for verifying the effect of suppressing wear of a drilling bit. As shown in the figure, in the experiment, drilling bits 121 and 122 having a thickness of 3.2 mm and a length of 30 mm along the mounting direction were placed at regular intervals 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 4 of them. In Example 1, two of the drilling bits 121 have a protrusion height of 10 mm from the end face of the steel pipe body, and the remaining two drilling bits 122 have a protrusion height of 14 mm. 122 are arranged alternately in the circumferential direction of the steel pipe body 11 . The mounting angle of the drill bit is 10°. In Example 2, in addition to the protrusion height difference of Example 1, the mounting angle of the drilling bit 121 was set to 10°, and the mounting angle of the drilling bit 122 was set to 15°. Each of the drilling bits 121 and 122 protrudes to both the outside and the inside 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. Incidentally, FIG. 16 shows the conditions of the second embodiment. In the comparative example, four drilling bits were similarly attached, but all drilling bits had a protrusion height of 12 mm and an attachment angle of 10°.

FIG. 17 is a graph showing the results of the experiment shown in FIG. 16; A mortar model ground was excavated to a working depth of 500 mm using the steel pipe piles according to Example 1, Example 2 and Comparative Example as described with reference to FIG. As a result, as shown in the graph, two sets of excavation with different protrusion heights were obtained when the volume retention rate of each bit in the comparative example, in which all excavation bits had the same mounting angle and excavable area, was 1. In Example 1, in which bits were arranged, the volume retention rate of the excavation bit 121 having a low projecting 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 construction to the volume of the excavation bit before construction. Furthermore, in Example 2, in which the two sets of drilling bits have different excavable regions in addition to their projecting heights, the volume retention rate of the drilling bit 121 having a low projecting height and a small excavable region was 5.23 times that of the comparative example. there were. As a result, it is possible to maintain the function of the drilling bits against wear during drilling by having different protrusion heights among a plurality of drilling bits. It shows that the effect is improved by making them different.

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

Reference Signs List 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 (12)

A steel pipe pile comprising a steel pipe body and a plate-shaped excavation bit attached to an end face of the steel pipe body at an angle with respect to a circumferential tangent line of the steel pipe body and protruding in the axial direction of the steel pipe body,
the drilling bit
a first drilling bit protruding from an end surface of the steel pipe body by a first height in the axial direction of the steel pipe body;
a second drilling bit that protrudes from the end surface of the steel pipe body in the axial direction of the steel pipe body by a second height that is higher than the first height ;
The steel pipe pile, wherein the second excavation bit intersects the pipe thickness center line of the steel pipe body when the steel pipe pile is viewed from the tip side . 2. A tip surface of at least one of said first drilling bit and said second drilling bit is formed with an inclination in which the projecting height increases from the inner side to the outer side in the radial direction of said steel pipe body. The steel pipe pile described in . 3. The steel pipe body according to claim 1, wherein at least one of said first drilling bit and said second drilling bit is formed with a tapered cross-section that becomes thicker from the radially inner side to the outer side of said steel pipe body. steel pipe piles. 4. The drilling bit further includes a third drilling bit projecting from the end face of the steel pipe body in the axial direction of the steel pipe body by a third height higher than the second height. The steel pipe pile according to any one of 1. The steel pipe according to any one of claims 1 to 4, wherein the excavation bit has a plate shape that is curved into a C-shape or an S-shape when the steel pipe pile is viewed from the tip side. pile. The drill bit protrudes radially outward or inward from the steel pipe body,
The first drilling bit has a first drillable region by protruding a first distance in a radial direction of the steel pipe body from a pipe thickness center line of the steel pipe body,
The second drill bit protrudes from the thickness center line of the steel pipe body in the radial direction of the steel pipe body by a second distance that is longer than the first distance. The steel pipe pile according to any one of claims 1 to 5, which has a second excavable area that is wider than the first excavable area on at least one of the inner side and the second excavable area. the first drill bit is mounted at a first angle with respect to a circumferential tangent of the steel pipe body;
7. The steel pipe pile of claim 6, wherein said second drill bit is mounted at a second angle greater than said first angle with respect to a circumferential tangent of said steel pipe body. said first drilling bit having a first length along a mounting direction of said first drilling bit;
8. The steel pipe pile according to claim 6 or 7, wherein said second drilling bit has a second length that is longer than said first length along the mounting direction of said second drilling bit. A steel pipe pile construction method according to any one of claims 1 to 8,
a step of excavating while rotating the steel pipe pile in a first rotation direction in which the excavation bit pushes earth and sand out of the steel pipe body until the tip of the steel pipe pile reaches a predetermined depth;
a step of excavating while rotating the steel pipe pile in a second rotation direction in which the excavation bit takes earth and sand into the inside of the steel pipe body until the tip of the steel pipe pile reaches a slamming depth. Method. The construction method of the steel pipe pile according to claim 9, wherein, in the stopping, the tip of the steel pipe pile reaches the support layer, and then the steel pipe pile is rotated in the second rotation direction. During the driving, 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 tip of the steel pipe pile reaches the support layer. The construction method of the steel pipe pile according to claim 9, which is driven from. The step of excavating while rotating the steel pipe pile in the first direction of rotation and the step of excavating while rotating the steel pipe pile in the second direction of rotation are alternately performed. 12. The steel pipe pile construction method according to any one of 11.

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