JP4988068B2 - Steel pipe pile and its construction method - Google Patents

Description

The present invention relates to a steel pipe pile used in the field of civil engineering and architecture, such as a harbor structure or a bridge foundation or a building foundation, and a construction method thereof.
This application claims priority on July 05, 2010 based on Japanese Patent Application No. 2010-153290 for which it applied to Japan, and uses the content for it here.

Conventionally, as a friction pile, in order to increase the peripheral frictional force of the pile, the outer peripheral surface of the tip of the pile is a tapered outer peripheral surface, or the outer peripheral surface of the entire length of the pile is a tapered outer peripheral surface, and the tip of the pile It is known that a reinforcing bar is spirally wound over the entire length of a constant diameter portion having a constant outer diameter from the taper portion (see, for example, Patent Document 1). Such a friction pile is expected to have a frictional force on the outer peripheral surface of the pile.
In addition, a plurality of spiral wings are provided on the outer peripheral surface of the intermediate portion in the length direction of the pile at intervals in the pile axis direction, and the same pitch as the blade pitch (propulsion pitch) in the spiral wings is provided at the cone portion at the tip of the pile. It is also known that a steel strip is fixed to the cone portion spirally at the same propulsion pitch by welding or the like (see, for example, Patent Document 2).

When penetrating a pile into the ground, if the planar projected area of the tapered outer peripheral surface portion is large, the pile will exhibit a supporting force after completion of the pile penetration. On the other hand, at the time of pile construction, especially when it is necessary to punch an intermediate layer of rock such as soft rock, medium hard rock and hard rock whose uniaxial compressive strength exceeds 3 N / mm ² , or the support layer is rock. When a pile is penetrated there, the tapered outer peripheral surface portion becomes a large penetration resistance.

  In order to embed cast-in-place reinforced concrete piles and precast concrete piles, it is also known to use a casing having a tapered outer peripheral surface and a tapered inner peripheral surface on the tip side (see, for example, Patent Document 3).

Japanese Unexamined Patent Publication No. 2003-3465 Japanese Unexamined Patent Publication No. 8-284160 Japanese Unexamined Patent Publication No. 2005-248439

When a pile is penetrated into the ground by rotary press-fitting, the resistance of the closed soil in the pipe increases as the depth of penetration increases, so a high indentation force and rotational force are required. Here, the pushing force refers to the force applied to push the pile down in the penetration direction. Moreover, rotational force refers to the force applied in order to turn a pile.
A reaction force is required to secure the pushing force to rotationally press the pile, and it is necessary to install a counterweight or an anchor on the rotational press-fitting machine to ensure the reaction force. It becomes. These transportation costs, work costs, material costs, etc. are required, and the construction cost of piles will increase. In addition, in order to secure the pushing force, the rotary press-fitting construction machine is also increased in capacity and increased in size, so that the pile construction cost is further increased.
Furthermore, in order to acquire the propulsive force of the pile, if a jig such as a spiral wing or blade for propulsion is attached to the pile, processing costs, mounting costs and material costs are incurred. Furthermore, in the construction of soft ground, Conversely, the construction speed is limited by the spacing between the spiral blades or blades, leading to a reduction in construction speed.
Moreover, after penetrating an existing pile into a support layer, in order to acquire a higher support force, there exists a construction method which obstruct | occludes the tip of an existing pile reliably. In this method, it is necessary to completely remove the soil at the tip of the pile and then cast concrete or to inject a cement milk into the tip of the pile to create a solidified portion.

In addition, in an open end pile with a bit having an open end and a drilling bit at the end of the pile, soil flows into the pipe and accumulates as the open end pile penetrates into the ground during rotary press-fitting. Thereby, the obstruction | occlusion degree of the front-end | tip part of a pile increases and becomes a cause of the resistance at the time of pile press-fit. The blockage of the tip of the pile is caused by friction between the material (soil) constituting the ground such as sand, clay, and stone that has flowed into the pipe and the inner peripheral surface of the inside of the pile.
In particular, a problem in the pile rotary press-in construction is the pushing force for pushing the pile in the penetration direction into the ground. This is because the reaction force is usually obtained by the weight of the weight or the construction machine itself at the time of pile press-fitting construction, and in order to increase the reaction force, many weights are required, which is uneconomical. The force in the rotation direction can be obtained by applying the reaction force to another heavy machine with a rod-shaped jig or the like for obtaining the reaction force.

  In the case of a pile with a spiral protrusion on a constant diameter part with a constant outer diameter, when the pile is rotated and pressed, the spiral protrusion provided on the constant diameter part is Disturb the surrounding ground of the face part. Thereby, there exists a possibility that the pile peripheral surface frictional resistance of the surrounding surface of a steel pipe pile and surrounding ground may reduce. Therefore, even if the pile belongs to the support pile, both the pile tip support force and the peripheral frictional resistance of the constant diameter part are expected by not disturbing the ground on the outer peripheral surface side of the constant diameter part as much as possible. can do.

Moreover, in the case of a pile having a tapered outer peripheral surface in the entire length in the pile axis direction, the manufacturing cost of the pile becomes high, and the pile construction device becomes special, and the construction becomes complicated.
In addition, when the spiral projections are provided so as to form a propulsion pitch over several turns spirally in the circumferential direction of the tapered outer peripheral surface of the construction pile, the vicinity of the tapered outer peripheral surface at the time of pile press-fitting The soil flows as guided by the spiral protrusions. Since the soil is not actively sheared and destroyed by the spiral protrusions, it is difficult to reduce the adhesion between the tapered outer peripheral surface and the soil.
In this case, as the planar projection area of the tapered outer peripheral surface portion increases, the pushing force increases, and the resistance due to adhesion of soil to the tapered outer peripheral surface portion also increases.

Steel pipe piles with a tapered outer peripheral surface and a tapered inner peripheral surface only at the tip of the pile as a technology to eliminate the disadvantages of the tapered pile with a tapered outer peripheral surface over the entire pile length as described above The present invention has been filed by the present applicant.
Thus, by providing a tapered portion having a tapered outer peripheral surface and a tapered inner peripheral surface at the tip of the steel pipe pile, resistance due to friction between the pipe inner soil and the pile inner peripheral surface is reduced. Thereby, the resistance generated by friction between the earth and sand that has entered the pipe and the inside of the steel pipe, that is, the so-called blockage resistance in the pipe can be reduced. In addition, since the projected area of the bottom surface of the pile is increased by the tapered portion and resists the ground, a high supporting force can be easily obtained. Especially in the deep support layer and the hard rock layer where the confining pressure of the ground is high, a high compressive load can be borne in the area of the projected area of the bottom surface of the tapered part. Moreover, higher support force can be exhibited than the normal straight steel pipe pile which the front-end | tip is opening.
However, in a steel pipe pile having a tip tapered portion, the tip tapered portion makes a high load on the tapered portion because the tip tapered portion comes into direct contact with the ground at the time of pile construction. By rotating a steel pipe pile with a tip tapered portion protrusion while a high load is generated, the steel plate thickness of the tip tapered portion may be reduced by wear or may be deformed. Moreover, since a large resistance is generated in the load at the tip tapered portion, it is desired to further reduce the resistance in order to further reduce the capacity of the construction machine and enable the construction.
When constructing a pile by rotational press-fit construction, if the pushing force for pushing the pile in the underground penetration direction can be reduced, the construction cost per pile can be reduced. Accordingly, since a large number of piles are rotationally press-fitted into the ground, it is important to reduce the construction cost per pile in order to significantly reduce the total construction cost.
An object of this invention is to provide the steel pipe pile which can reduce the pushing force of a pile, and its construction method.

The present invention employs the following means in order to solve the above problems and achieve the object.
That is,
(1) A steel pipe pile according to one aspect of the present invention is a steel pipe pile that is open and hollow at the front end in the excavation direction, and has a constant diameter portion having a constant outer diameter, and toward the front end. A tip portion having an inner shape dimension and an outer shape dimension that gradually decrease; extending partially or entirely on the outer peripheral surface of the tip portion from the front end toward the rear end, and radially outward of the tip portion And a ratio of the height dimension in the length direction of the tip portion to the outer dimension of the constant diameter portion is 0.3 to 5.5 .

(2) In the steel pipe pile according to (1), it is preferable that a plurality of the protrusions are provided at intervals in the circumferential direction of the outer peripheral surface of the tip portion.
(3) In the steel pipe pile according to (1) or (2), the protrusion is inclined so that the rear end side of the protrusion is behind the constant diameter portion and the tip end in the rotation direction. It is preferable.
(4) In the steel pipe pile according to any one of (1) to (3) , the protrusion is disposed to be inclined in the circumferential direction with respect to the central axis of the tip, and is perpendicular to the central axis. The angle formed by the surface and the central axis in the extending direction of the protrusion is preferably 20 ° to 70 °.
(5) In the steel pipe pile according to any one of (1) to (4) , the protrusion is positioned on the inner side of the distal end portion in the radial direction with respect to the outer dimension of the constant diameter portion. Further, it is preferable that the height of the protrusion is defined.

(6) In the steel pipe pile according to any one of (1) to (5), it is preferable that a plurality of excavation bits are provided at intervals in the circumferential direction of the front end.
(7) In the steel pipe pile according to any one of (1) to (6), it is preferable that a lower end of the protrusion is positioned immediately above an upper surface of the excavation bit.
(8) In the steel pipe pile according to any one of (1) to (7) , the excavation bit is disposed on the inner side in the radial direction of the tip portion than the outer dimension of the constant diameter portion. It is preferable .
( 9 ) In the steel pipe pile according to any one of (1) to (8), the ratio of the outer diameter dimension of the front end to the outer diameter dimension of the constant diameter portion is 0.60 to 0.95. Preferably there is.
( 10 ) In the steel pipe pile according to any one of (1) to (9), it is preferable that the tip portion is provided with a pointed portion protruding from the front end and sharpened in the excavation direction. .

( 11 ) A method for constructing a steel pipe pile using the steel pipe pile according to any one of (1) to (10 ) above, wherein the ground is formed by a rotary press-fitting method for applying a rotational force and an indentation force to the steel pipe pile. When press-fitting into the steel pipe, it is preferable to press-fit the steel pipe pile while shearing and destroying the ground with the protrusion.
( 12 ) In the steel pipe pile construction method described in ( 11 ) above, it is preferable to rotationally press-fit the steel pipe pile into the ground including the hard ground.
( 13 ) In the construction method of the steel pipe pile according to the above ( 11 ), in the middle of the construction, the steel pipe pile is rotated up and down while rotating, or without rotating, or combining them. It is preferable to lower the height of the soil in the steel pipe pile.
( 14 ) In the construction method of the steel pipe pile according to ( 11 ), the steel pipe pile is reversely rotated when the tip portion of the steel pipe pile is finally stopped in the support layer, and the protrusion is used to It is preferable to push the soil near the outer peripheral surface of the tip portion downward.

First, steel pipe piles include a closed-end pile whose front end is closed and an open-end pile whose front end is open, and the present invention belongs to an open-end pile whose front end is open.
In addition, the steel pile pile is supported by the friction pile that is expected to provide the support force by mainly exerting the frictional force on the peripheral surface without being driven into the support layer, and the support force at the tip portion is driven mainly by being driven into the support layer. There is a support pile that expects a force, and the present invention belongs to a support pile that expects a support force by driving a steel pipe pile into a support layer to exhibit a support force at the tip.

According to the steel pipe pile described in (1) above, the pile is installed in the ground by the projection with a simple configuration in which the projection is simply provided at the tapered tip portion where the inner and outer dimensions are gradually reduced. When doing, wear and deformation of the tip can be suppressed.
Moreover, it becomes possible to reduce the construction load at the time of construction of a steel pipe pile, and the capability of a construction machine can be suppressed. Depending on the case, it is possible to obtain an effect that the construction machine can be downsized and the steel pipe pile can be made at a low construction cost.
Moreover, since the front-end | tip part is a taper shape, this steel pipe pile can reduce the resistance by the friction of an internal peripheral surface, and can aim at the improvement of workability. In addition, the tapered tip increases the projected area of the bottom surface of the pile and resists the ground, so a high supporting force can be easily obtained. In addition, in the ground where the confining pressure is high, the support layer is deep, or the rock layer is hard, a high compression load can be borne at the tapered tip (bottom projected area). The steel pipe pile (the steel pipe pile having only the constant-diameter portion) having a higher supporting force can be exhibited.
Usually, it is necessary to block the front end of the pile in order to exert a supporting force at the front end of the pile, such as a driven pile. For example, in the case of a driven pile whose tip is open, in order to close the pile tip, it is necessary to penetrate the pile into the support layer more than a certain amount. However, since this steel pipe pile has a taper-shaped front-end | tip part, the supporting force of the front end of a pile can be improved. As a result, it is not necessary to close the front end face of the pile in order to develop the support force at the front end of the pile, and it is possible to acquire the support force even with a small amount of penetration, and to shorten the construction time. Etc. are obtained.
Furthermore, since the ratio of the height dimension in the length direction of the tip portion to the outer dimension of the constant diameter portion is 0.3 to 5.5, a straight steel pipe pile (a steel pipe having only a constant diameter portion is used in soft ground. Compared with a pile), the resistance by the friction of the inner peripheral surface of a steel pipe pile can be reduced and workability can be improved. Furthermore, in the support layer, an effect that a high support force can be exhibited with a small amount of penetration is obtained.

According to the steel pipe pile described in the above (2), a plurality of the protrusions are provided at intervals in the circumferential direction of the tip end portion, so that the taper tip end portion is formed by the protrusion provided at intervals. Effects such as further suppression of wear and deformation can be obtained.
According to the steel pipe pile described in the above (3), since the protrusion is inclined such that the rear end side of the protrusion is behind the constant diameter portion and the distal end in the rotation direction, the excavated tapered shape The drilling soil (shear) that flows upward on the outer peripheral surface side of the tip, or the soil that is sheared and destroyed by the protrusions can be smoothly guided and flowed along the direction in which the protrusions are inclined. It is done.

According to the steel pipe pile described in (4) above, the angle formed by the surface perpendicular to the central axis of the tip and the central axis in the extending direction of the protrusion is 20 ° to 70 °. It is possible to obtain an effect such as being able to exert an appropriate shear breaking action or guiding action of the soil.
According to the steel pipe pile described in the above (5), since the height of the protrusion is defined so that the protrusion is positioned on the inner side in the radial direction of the distal end portion than the outer dimension of the constant diameter portion, This reduces the range of soil disturbance. Therefore, effects such as reduction in friction on the outer peripheral surface can be obtained.
According to the steel pipe pile described in (6) above, since a plurality of excavation bits are provided at the front end of the tip, even if the ground is hard ground, it can be easily excavated and rotated to penetrate into the ground. The effect that it can do is acquired.

According to the steel pipe pile described in (7) above, since the lower end of the protrusion is located immediately above the upper surface of the excavation bit, the excavation bit was excavated along the outer peripheral surface side of the tapered tip portion. The effect of being able to reliably guide the soil (sliding) by the protrusions is obtained.
According to the steel pipe pile described in the above (8), the excavation bit is arranged on the inner side in the radial direction of the tip part rather than the outer dimension of the constant diameter part. Since the planar outer diameter of the steel pipe pile to be reduced is reduced, the size can be reduced. Furthermore, since the excavation outer diameter is reduced, the excavation amount is small, and the effect of improving workability can be obtained.

According to the steel pipe pile described in ( 9 ) above , the ratio of the outer diameter dimension of the front end to the outer diameter dimension of the constant diameter portion, that is, the diameter reduction rate of the steel pipe pile is in the range of 0.60 to 0.95. Therefore, compared with the case where a straight steel pipe pile is constructed, the counterweight in the rotary press fitting machine can be reduced. In addition, it is possible to reduce the size of the pile construction machine and improve the workability in the intermediate layer. Furthermore, the effect that it can be set as the steel pipe pile which can aim at the increase in supporting force, aiming at reduction of the penetration amount in a support layer is acquired.
According to the steel pipe pile described in the above ( 10 ), since the tip portion is provided with the pointed portion protruding from the front end and sharpened in the excavation direction, the steel pipe pile capable of being efficiently constructed while excavating the ground and The effect which can be done is acquired.

According to the construction method of the steel pipe pile described in the above ( 11 ), the rotary press-in method for applying the rotational force and the pushing force to the steel pipe pile is applied to the steel pipe pile having the tapered tip portion of the above (1) to (10). Since it is press-fitted into the ground, the construction cost can be reduced. In addition, compared to straight steel pipe piles (steel pipe piles with a constant diameter only), even if the amount of penetration into the support layer is small, it is possible to construct foundation piles with high supportability with good workability and low cost. Is obtained. Furthermore, for example, a steel pipe pile can be constructed more efficiently by using a steel pipe pile having a drill bit.
According to the construction method of the steel pipe pile described in the above ( 12 ), the steel pipe pile having the tapered tip of the above (1) to (10) is rotationally press-fitted into the ground including the hard ground. Even ground that contains it can be constructed at low cost. Moreover, when penetrating into the support layer of the hard ground, an effect such as being able to construct a foundation pile having a high support force can be obtained even if the amount of penetration into the support layer is small compared to a straight pile. .

According to the construction method of the steel pipe pile described in the above ( 13 ), the height of the soil in the steel pipe pile is lowered by moving the steel pipe pile up and down in the ground during the construction. The effect that it can construct efficiently, reducing the friction of a surface is acquired.
According to the construction method of the steel pipe pile described in the above ( 14 ), when the front end portion of the steel pipe pile is finally stopped in the support layer, the steel pipe pile is reversely rotated, and the protrusion near the tapered outer peripheral surface is formed. Push the soil (slipping including crushed stone) downward. Thereby, the effect of being able to support the steel pipe pile by pushing the soil near the outer peripheral surface of the tapered tip portion downward by the protrusions to make the support layer on the pile lower surface side dense.

It is a front view which shows the steel pipe pile which has protrusion in the front-end | tip part of 1st Embodiment of this invention. It is a longitudinal front view of the steel pipe pile. It is sectional drawing in the aa arrow of FIG. 1B. It is a bb arrow line view of FIG. 1B. It is a perspective view which shows the steel pipe pile which has protrusion in the front-end | tip part of 2nd Embodiment of this invention. It is a front view of the steel pipe pile. It is a front view which shows the steel pipe pile which has protrusion in the front-end | tip part of 3rd Embodiment of this invention. It is a longitudinal front view of the steel pipe pile. It is sectional drawing in the cc arrow line of FIG. 3B. It is a dd arrow line view of Drawing 3B. It is a perspective view which shows the steel pipe pile which has a processus | protrusion in the front-end | tip part of 4th Embodiment of this invention. It is a front view of the steel pipe pile. It is a front view which shows the steel pipe pile which has a processus | protrusion in the front-end | tip part of 5th Embodiment of this invention. It is a front view which shows the steel pipe pile which has a processus | protrusion in the front-end | tip part of 6th Embodiment of this invention. It is a longitudinal front view of the steel pipe pile. It is sectional drawing in the ee arrow of FIG. 6B. It is the ff arrow line view of FIG. 6B. It is a side view which shows the shape and attachment range of the protrusion provided in the steel pipe pile of 7th Embodiment of this invention. It is sectional drawing which shows the shape and attachment range of the protrusion provided in the steel pipe pile of 7th Embodiment of this invention. It is explanatory drawing which shows a comparative example. It is explanatory drawing which shows a comparative example. It is a front view which shows the state which is carrying out the rotation press-fit of the steel pipe pile to the ground with the rotation press-fitting construction machine. It is a graph which shows the relationship between the construction load of the steel pipe pile of this invention which has a processus | protrusion in a taper-shaped front-end | tip part, and the steel pipe pile of a comparative example which is not equipped with a processus | protrusion in a taper-shaped front end part, penetration amount, and pressure input. . It is the figure which compared the average amount of wear of the tip part at the time of constructing the case of the steel pipe pile which has a projection in the tapered tip part of the present invention, and the steel pipe pile which does not have the projection in the tapered tip part. . It is the figure which compared the average deformation amount of the front-end | tip part at the time of constructing the case of the steel pipe pile which has a processus | protrusion in the taper-shaped front-end | tip part of this invention, and the steel pipe pile which does not have a processus | protrusion in a taper-shaped front-end | tip part. . It is a figure which shows the rotation direction in the case of carrying out rotation press-fit in the ground using the steel pipe pile of this invention. It is sectional drawing of FIG. 13A, and is explanatory drawing which shows the flow of soil. It is a longitudinal front view which shows the state which carried out the press-fit of the steel pipe pile to the support layer. It is explanatory drawing which shows the flow of the soil in the case of carrying out rotation press-fit in the ground using the steel pipe pile. It is a longitudinal front view which shows the relationship between the press-fit depth at the time of press-fitting the steel pipe pile to a support layer, the height of pipe | tube soil, and the dimension of the front-end | tip part vicinity. It is a graph which shows the relationship between the pushing force per block | closed cross-sectional area of a pile, and the ratio of the penetration amount with respect to a pile diameter about the steel pipe pile and the straight pile as a comparative example. It is a graph which shows the relationship between the ratio of the tip settlement amount with respect to a pile diameter, and the tip load degree of a pile about the steel pipe pile and the straight pile as a comparative example. It is a graph which shows the relationship between the ratio of the length of the front-end | tip part with respect to the outer diameter of the steel pipe pile, the required pushing force of the steel pipe pile, and the required pushing force ratio which is a ratio of the required pushing force of a straight pile. It is a graph which shows the relationship between the diameter reduction rate (D2 / D1) of a front-end | tip part, and required pushing force ratio. It is a figure which shows the resistance of the front-end | tip part side of a steel pipe pile, Comprising: It is a vertical front view which shows the case of the straight pile of a comparative example. It is a vertical front view which shows the case of the steel pipe pile of a taper-shaped front-end | tip part. It is a front view which shows the steel pipe pile as a comparative example. FIG. 22B is a longitudinal front view of FIG. 22A. It is sectional drawing in the gg arrow of FIG. 22B.

    Next, the present invention will be described in detail based on the illustrated embodiment.

  1A to 1D show a steel pipe pile (hereinafter also referred to as a steel pipe pile 1A with a tapered tip protrusion) 1 according to a first embodiment of the present invention.

1 A of steel pipe piles with a front-end | tip taper part protrusion of this invention are laid by the rotary press-fit method. As shown in FIG. 1A, the steel pipe pile 1 </ b> A is open at the front end (front end) 4 a in the excavation direction A <b> 1 and is hollow, and includes a constant diameter portion 9 and a tapered portion (tip end portion) 4.
The constant diameter portion 9 has a constant outer diameter. The tapered portion 4 is tapered, and the tapered portion 4 is provided with a protrusion 16a. The inner peripheral surface 3 of the taper portion 4 has a tapered shape in which the inner dimension gradually decreases in the length direction toward the tip 4a. Moreover, the outer peripheral surface 2 of the taper part 4 is a taper shape from which an external dimension gradually reduces in the length direction toward the front-end | tip 4a.
A plurality of excavation bits 6 are provided at the front end 4a of the taper portion 4 at equal angular intervals in the circumferential direction. When a plurality of even-numbered excavation bits 6 are provided, they are arranged symmetrically with respect to the plane including the central axis C of the steel pipe pile 1A, and when a plurality of odd-numbered excavation bits 6 are provided, they are provided at equiangular intervals. The excavation bit 6 is fixed to the tip 4a of the steel pipe pile 1A through a holder part (not shown) as appropriate.

Thus, by providing the excavation bit 6 at the tip of the steel pipe pile 1A with the tip tapered protrusion, it is possible to penetrate the steel pipe pile 1A while excavating the ground in the rotary press-fitting method even if the ground is hard. it can. In particular, as shown in FIG. 14, the steel pipe pile 1 </ b> A can be penetrated into the support layer 8 made of the hard ground 15 while rotating and excavating in the arrow X direction and the arrow Y direction. In this case, a rotary press-fitting construction machine 7 as shown in FIG. 9 or a pile construction machine equipped with a leader for pile driving is used.
In the steel pipe pile 1A of the present embodiment, a form in which the excavation bit 6 is provided at the front end 4a of the tapered portion 4 is preferable, but a form in which the excavation bit 6 is not provided may be employed.

  In the form shown in FIG. 1A, the excavation bit 6 is provided at the tip 4 a of the taper portion 4, and the excavation bit 6 at the tip 4 a of the steel pipe pile 1 A has a radius of the taper portion 4 rather than the outer dimension D 1 of the constant diameter portion 9. Arranged inside the direction. Thereby, compared with the case where the excavation bit 6 is provided in the taper part 4 of the straight steel pipe pile (steel pipe pile of only a fixed diameter part) 10 as shown to FIG. 22A-FIG. 22C, the plane of the steel pipe pile 1A with an excavation bit is shown. The outer diameter can be reduced. As a result, when the plurality of steel pipe piles 1A are loaded in a plurality of stages and transported by truck, the excavation bit 6 does not interfere with the adjacent steel pipe piles. Therefore, a plurality of steel pipe piles 1A can be loaded in a stable state without interposing a spacer or the like. Further, when the excavation bit 6 is provided in the tapered portion 4 of the straight steel pipe pile 10 as shown in FIGS. The possibility of greatly disturbing the ground can be eliminated.

In addition, a protrusion 16 a is provided on the outer peripheral surface 2 of the tapered portion 4. As shown in FIGS. 1A and 1B, the protrusion 16 a extends partly or entirely from the front end 4 a toward the rear end 9 a and protrudes outward in the radial direction of the tapered portion 4. The protrusion 16 a of this embodiment is provided on a part of the outer peripheral surface 2 of the tapered portion 4. Further, a plurality of protrusions 16 a are provided at intervals in the circumferential direction of the outer peripheral surface 2 of the tapered portion 4.
The protrusion 16a is inclined such that the upper portion in the direction of the central axis C of the steel pipe pile 1A is rearward in the pile rotation direction when rotating and penetrating. Specifically, the protrusion 16a is inclined so that the rear end 9a side of the protrusion 16a is behind the constant diameter portion 9 and the tapered portion 4 in the rotation direction. In this way, the upper portion of the protrusion 16a in the central axis C direction is inclined so as to be rearward in the rotational direction of the steel pipe pile 1A with respect to the lower side, so that the excavation bit is indicated by an arrow B1 in FIG. 1A. It is possible to guide excavated soil (shear) flowing upward on the outer peripheral surface 2 side excavated by 6 or earth and sand sheared and destroyed by the projection 16a in a direction in which the projection is inclined. As a result, the excavated soil and earth and sand can be smoothly flowed backward in the excavation direction A1.
Further, the protrusion 16 a is arranged to be inclined in the circumferential direction with respect to the central axis C of the tapered portion 4. The central axis C2 of the protrusion 16a is inclined with respect to the front surface 4a of the tapered portion 4 at an angle δ. That is, the angle formed by the central axis C2 of the protrusion 16a and the front surface 4a may be 90 °, but in the present embodiment, the angle δ is less than 90 °. Details of the angle δ will be described later.

  By providing the tapered portion 4 at the tip 4a of the steel pipe pile 1A, an effect of greatly reducing the ground resistance due to the blockage in the steel pipe pile 1A can be expected. However, since the tapered portion 4 receives a large resistance, Wear and deformation occur. Therefore, in the present embodiment, a plurality of protrusions 16a are provided on the outer peripheral portion 2 of the tapered portion 4, which is the portion that receives the most resistance when the steel pipe pile 1A is penetrated.

  As a form for providing the protrusion 16a, a form in which the protrusion 16a is fixed to the outer peripheral surface 2 of the taper portion 4 by welding a rod-shaped steel material such as a reinforcing bar or a flat steel is not shown, but the outer peripheral surface of the taper portion 4 is omitted. 2 may be subjected to overlay welding to form protrusions, and when the tapered portion 4 is formed, a protrusion by rolling may be provided. As a form of the protrusion by rolling, for example, a fan-shaped steel sheet with a single-sided protrusion is arranged so that the protruding part is outside the pile and is inclined in the central axis direction of the pile, and is bent into a truncated cone shape. The end is closed by welding to form a truncated cone. By fixing the end portion on the large diameter side of the truncated conical body to the lower end portion of the steel pipe by welding, a steel pipe pile 1A having a tapered portion 4 is obtained. By providing an excavation bit in the tapered portion 4 of the truncated conical body, the steel pipe pile 1A having the tapered portion 4 of the present embodiment can be obtained.

  1A, the protrusion 16a is linear from the front end 4a to the rear end 9a of the steel pipe pile 1A, and the protrusion 16a is also linear in the circumferential direction. May be. As shown in FIG. 1A, the width dimension in the central axis C direction of the steel pipe pile 1A is constant as the width dimension of the protrusion 16a in the pile circumferential direction, but the upper side (rear end 9a side) of the protrusion 16a is narrowed. It may be provided as follows. In this configuration, the width dimension of the protrusion 16a in the circumferential direction of the steel pipe pile 1A is such that when the soil is guided along the protrusion 16a to the upper portion of the outer peripheral surface 2 of the tapered portion 4, the upper end from the upper end of the protrusion 16a. At the moment of separation, the width dimension portion in the pile circumferential direction of the protrusion 16a becomes a space. Thereby, earth and sand etc. can be poured smoothly.

  As a form of providing the projection 16a, as shown in FIG. 1A, a lower end portion of the projection 16a may be provided so as to be connected to the upper mounting portion of the excavation bit 6. Thus, if it provides so that it may connect with the excavation bit 6, the soil can be efficiently guided and flowed along the outer peripheral surface 2 of the taper part 4 by the excavation bit 6 and the protrusion 16a connected to this.

Next, the steel pipe pile 1B of 2nd Embodiment is demonstrated.
As shown in FIGS. 2A and 2B, the protrusion 16b may be provided in a state of being spaced apart from the excavation bit 6 in the circumferential direction of the steel pipe pile 1B. Specifically, the protrusion extends from the excavation bit 6 to the rear side of the rotation direction of the steel pipe pile 1 (forward rotation direction) in the range of about the width dimension of the excavation bit 6 in the circumferential direction of the pile. It is provided at a position separated in the rear or pile axis direction. Even in this case, similarly to the first embodiment, as indicated by an arrow B1 in FIG. 2B, the excavation soil (slave) flowing upward on the outer peripheral surface 2 side excavated by the excavation bit 6 or the protrusion 16b. The earth and sand to be sheared can be guided in the direction in which the protrusions are inclined. As a result, the excavated soil and earth and sand can be smoothly flowed backward in the excavation direction A1.

Next, the steel pipe pile 1C of 3rd Embodiment is demonstrated.
In 1st, 2nd embodiment mentioned above, although protrusion 16a, 16b demonstrated the structure which continued to at least one of the central axis C direction and the circumferential direction of 1 C of steel pipe piles, as shown to FIG. 3A-FIG. 3D In addition, the protrusions 16c may be intermittently disposed. That is, as shown in FIGS. 3A and 3B, the two protrusions 16c may be arranged at an interval in the excavation direction A1. As described above, when a plurality of protrusions 16c are provided intermittently in the excavation direction A1, three or more protrusions 16c may be intermittently arranged in series at intervals.

Next, steel pipe pile 1D of 4th Embodiment is demonstrated.
In each said embodiment, although the processus | protrusion 16a-16c showed the structure inclined with respect to the central axis C, it does not need to incline.
As shown in FIG. 4A, the protrusion 16d extends along the central axis C of the steel pipe pile 1D. Further, the lower end 16e of the protrusion 16d is positioned immediately above the upper surface 6a of the excavation bit 6, as shown in FIG. 4B. In such a case, the soil is guided by the protrusion 16d so as to flow along the outer peripheral surface 2 of the tapered tip end portion 4 in the direction of the central axis C of the steel pipe pile 1D. Although the protrusion 16d of such a form may be sufficient, when considering rotating construction of the steel pipe pile 1D, like the protrusions 16a to 16c shown in the above embodiments, the steel pipe piles 1A to 1C in the positive rotation direction. When the protrusions 16a to 16c are inclined rearward, the soil flow along the outer peripheral surface 2 of the tapered portion 4 becomes smooth.
As described above, when the excavation bit 6 and the projection 16d are connected, the soil excavated by the excavation bit 6 and the soil (shear) sheared by the projection 16d are efficiently flowed upward along the tapered portion 4. Can do.

Next, the steel pipe pile 1E of 5th Embodiment is demonstrated.
As shown in FIG. 5, the taper part 4 of the steel pipe pile 1E is provided with a pointed part 5 protruding from the tip 4a and sharpened in the excavation direction A1. A concave portion 5 a is provided at the tip 4 a of the tapered portion 4. The recess 5a is not necessarily formed.
In the present embodiment, since no excavation bit is provided, the protrusion 16e extends from the front end 4a toward the rear end 9a over the entire outer peripheral surface 2 of the tapered portion 4.

Next, the steel pipe pile 1F of 6th Embodiment is demonstrated.
As shown in FIGS. 6A to 6D, a sharpened portion 5b sharpened in the excavation direction A1 may be provided at the tip 4a of the tapered portion 4 between the excavation bits 6 shown in FIG. 1A. Compared with the sharp portion 5 shown in FIG. 5, the tip of the sharp portion 5b is flat. In the present embodiment, the tip may be sharpened similarly to the fifth embodiment, and the tip of the sharpened portion 5 of the fifth embodiment may be flattened.

Next, the steel pipe pile 1G of 7th Embodiment is demonstrated.
FIG. 7A and FIG. 7B are explanatory views showing the shape and attachment range of protrusions provided on the steel pipe pile 1G.
The length of the protrusion 16g in the direction from the front end 4a to the rear end 9a may be provided over substantially the entire outer peripheral surface 2 of the tapered portion 4. In this case, the height of the protrusion 16g may be set in order to suppress the reduction in the peripheral friction of the steel pipe pile 1G as much as possible.
For example, as shown in FIG. 7B, the height H2 of the protrusion 16g is defined so that the protrusion 16g is located on the inner side in the radial direction of the tapered portion 4 with respect to the outer dimension of the constant diameter portion 9. In other words, the height of the protrusion 16g and the extension of the protrusion 16g are such that the protrusion 16g is located on the inner side in the radial direction of the steel pipe pile 1G with respect to the outer shape extension line 18 of the constant diameter portion 9 extending toward the tapered portion 4 side. The position of the upper end portion of the center axis C2 in the current direction is restricted. Thus, if the protrusion 16g is provided, the range which disturbs soil with the protrusion 16g decreases, and the reduction of the peripheral surface friction of the steel pipe pile 1G can be suppressed. The length of the protrusion 16g in the extending direction may be shorter than that in the above-described embodiment in a range that is inside the outer shape extension line 18 of the constant diameter portion 9.

Next, the inclination angle of the protrusion 16g will be described with reference to FIGS. 7A and 7B.
When the steel pipe pile 1G is viewed from the direction perpendicular to the excavation direction A1, the angle formed by the horizontal line D (front surface 4a) perpendicular to the central axis C and the central axis C2 in the extending direction of the projection 16g (projection with respect to the horizontal line D) The inclination angle δ) at which the central axis C2 of 16 g intersects is in the range of 20 ° to 90 °, preferably 20 ° to 70 °, more preferably 30 ° to 50 in accordance with the internal friction angle φ of the normal ground. If it is set within the range of °, shear fracture can be efficiently performed.
When the inclination angle δ of the protrusion 16g is 90 °, the soil can be efficiently sheared and broken by the shortest protrusion 16g when the steel pipe pile rotates. However, since the guide action of the soil accompanying the forward rotation of the steel pipe pile is small, the action of efficiently flowing the excavated soil (shear) from the tapered portion 4 to the upper side is reduced.
If the inclination angle δ of the protrusion 16g is less than 20 °, the length range in which the protrusion 16g is provided in the circumferential direction of the steel pipe pile becomes longer, which is not economical, and the shear fracture efficiency of the soil decreases. In this embodiment, the lower limit of the inclination angle δ of the protrusion 16g is set to 20 °. Further, when the inclination angle δ of the protrusion 16g is about 20 ° to 70 °, the burden per unit length of the protrusion when the soil is sheared is significantly reduced as compared with the case of 90 °. Furthermore, the guide action of the excavated soil can be reliably exhibited. Moreover, when the inclination angle δ of the protrusion 16g exceeds 90 °, the shear broken by the protrusion 16g is pushed downward with respect to the construction in the forward rotation direction of the steel pipe pile. Further, the shear fracture efficiency due to the protrusions 16g is also lowered. Thus, as described above, the best range is set to a range of 30 ° to 50 ° in consideration of the internal friction angle φ of the soil.
The range of the inclination angle δ is the same in the above embodiments.

Next, the height dimension of the protrusion 16g will be described with reference to FIG. 7B.
The height dimension H2 in the radial direction of the steel pipe pile 1G of the protrusion 16g is set to a length dimension of 0.6% to 3.0% of the outer diameter dimension D1 of the constant diameter portion 9 having a constant outer diameter. That is, the height dimension H2 = 0.006D1 to 0.03D1 is set.
Usually, since the outer diameter of the steel pipe pile is about 400 mm to 2500 mm, the height dimension H2 of the protrusion 16g in the pile radial direction is about 12 mm at the maximum in the steel pipe pile having the outer diameter of 400 mm, and the steel pipe pile having the outer diameter of 2500 mm. Then, it is about 15 mm to 75 mm.
The height dimension H2 of this protrusion is the same in the above embodiments.

  The protrusion interval between the protrusions 16g adjacent in the circumferential direction of the steel pipe pile is not particularly specified. For example, the protrusion interval between the protrusions 6g adjacent in the peripheral direction of the steel pipe pile is provided at the same angular interval. Alternatively, it may be provided in the same phase as the excavation bit 6 or may be provided in the vicinity of the excavation bit 6 at the same equiangular interval or at different arrangement intervals. Further, the position of the lower end portion of the protrusion 16g may be provided so as to be connected to the upper end portion of the excavation bit 6. When the excavation bit 6 and the projection 16g are connected to the outer peripheral surface 2 side of the tapered portion 4 at the time of forward rotation construction of the steel pipe pile, the soil excavated by the excavation bit 6 and the soil sheared by the projection 16g (shear) ) Can be efficiently flowed to the upper portion along the tapered portion.

Next, the results of testing the effect of reducing the construction load and the like depending on the presence or absence of the protrusion 16g provided on the tapered portion 4 will be described with reference to FIGS. 7A to 8B, FIG. 11, and FIG.
The form of the taper part of the steel pipe pile used for the test is a steel pipe pile 1G having a protrusion 16g on the taper part 4 of the seventh embodiment shown in FIGS. 7A and 7B, and a taper part shown in FIGS. 8A and 8B as a comparative example. A test was conducted on a steel pipe pile 17 having a shape in which no protrusions were provided in FIG. The steel pipe piles 1G and 17 of both test bodies used for the test are provided with four excavation bits 6 at equal angular intervals in the taper portion 4.
As for the main dimensions of the steel pipe piles 1G and 17 of both test bodies used in the test, the outer diameter dimension D1 of the constant diameter portion 9 having a constant outer diameter in each of the steel pipe piles 1G and 17 is 1000 mm. The length H1 of the steel pipe piles 1G and 17 of the tapered portion 4 in the direction of the central axis C is H1 = 0.5D1, and the relationship between the outer diameter D2 of the tapered portion 4 and the outer dimension D1 of the constant diameter portion 9 D2 = 0.9D1. Moreover, in the steel pipe pile 1G of this embodiment which provided the processus | protrusion 16g in the taper part 4, it arrange | positions so that a 16 mm diameter rebar may be connected to the upper end part of the excavation bit 6 as a procession | protrusion 16g, and it fixes by welding. The height H2 of the protrusion 16g is H2 = 0.016D1, and the protrusion 16g is a reinforcing bar. The protrusion 16g was fixed to the taper portion 4 by welding from the position immediately above the excavation bit 6 to the upper end of the taper portion 4 so as to be connected to the excavation bit 6 to be a steel pipe pile 1G.

The ground is soft rock (mudstone) having a uniaxial compressive strength of 5 N / mm ² , and is rotationally press-fitted from this ground to a depth that is three times the outer diameter D1 of each steel pipe pile 1G, 17. At the time of construction, the construction load per unit area of the pile head (pressure input: kN / m ² ) of the constant diameter portion 9 of the constant diameter portion 9 (pile head side) and the penetration to the outside diameter D1 The amount (penetration ratio) was measured, and the relationship between these construction loads and the penetration amount (penetration ratio) was shown in a graph in FIG.
As shown in FIG. 10, in the case of the steel pipe pile 17 not provided with the protrusion 16g in the tapered portion 4, the pressure input is a maximum of 645 kN / m ² , whereas the embodiment having the protrusion 16g in the tapered portion 4 is shown. In the case of the steel pipe pile 1G, the maximum pressure input was 363 kN / m ² . That is, it can be seen that a construction load of about 30% or more can be reduced.
Thereby, in the case of the steel pipe pile 1G which has the protrusion 16g in the taper part 4 of this invention, since a construction load can be reduced, a counterweight can be decreased. In addition, if the construction load can be reduced by about 30% or more, the capacity of the construction machine can be reduced. With existing construction machines, for example, construction can be performed using a small construction machine one rank below. Cost can be significantly reduced.

Moreover, about the steel pipe pile 1G and 17 of each said test body, the graph of the result of having measured about the average abrasion amount (%) of the center axis C direction of the steel pipe pile 1G and 17 in the outer peripheral surface of the taper part 4 is shown in FIG. . The measurement position of the wear amount is shown in the lower diagram of FIG. 11 as a result of measurement at three locations A, B, and C indicated by arrows in the upper diagram of FIG.
From FIG. 11, in the steel pipe pile 1G which provided the protrusion 16g in the taper part 4, compared with the steel pipe pile 17 which is not provided with the protrusion 16g in the taper part 4, the front end 4a (position 0 of a graph) of the taper part 4 and the front-end | tip At the upper end of the portion 4 (the position of 0.5D1 in the graph) and the center thereof (the position of 0.25D1), the average wear amount is significantly reduced to half or less. Furthermore, in the position of the front-end | tip 4a (position of the graph 0) of the taper part 4, and the upper end (position of 0.5D1) of the taper part 4, the steel pipe pile 1G is hardly worn, On the other hand, In the steel pipe pile 17 of the form which is not provided, it turns out that the average wear amount of a little over 2% is produced in the front end 4a of the taper part 4, and a little over 3% is produced in the upper end of the taper part 4. FIG.
The average wear amount (%) is a value (ratio) when the original plate thickness of the tapered portion 4 is 1. The average wear amount (%) is a value obtained by averaging the wear amounts of a plurality of specimens.

Further, the average deformation amount (%) in the radial direction with respect to the radial position (original shape) on the outer peripheral surface 2 of the tapered portion 4 in the steel pipe piles 1G and 17 of each test body is shown in the upper diagram of FIG. , F is a graph showing the result of measurement at the position indicated by F. The measurement point of the tapered portion 4 having the protrusion 16g of the present invention was measured along the protrusion 16g. When the steel pipe pile is deformed so as to be curved and dent in the center side (inside) in the radial direction of the steel pipe pile 1G, it is defined as + (plus) deformation, and the steel pipe pile 1G, 17 is curved to bulge outward in the radial direction. The case of deformation is displayed as-(minus) deformation.
From FIG. 12, in the steel pipe pile 17 in which the taper portion 4 is not provided with the protrusion, the taper portion 4 is deformed by being dented toward the central axis C on the distal end side in the axial direction, and the proximal end side in the axial direction (large diameter On the side), it begins to swell. In the steel pipe pile 1G of the present invention, the tapered portion 4 has a minute bulge in the pile axial direction, whereas the deformation form of the tapered portion 4 is reversed in the axial direction (swells after being dented). It turns out that it is only.
From the graphs of FIG. 11 and FIG. 12, in the case of the steel pipe pile 1G of the present invention having the protrusions 16g on the taper portion 4, the taper portion 4 has a taper portion 4 that is not provided with the protrusions 16g. It can be seen that the amount of wear and the amount of deformation are greatly improved.
When the protrusion 16g is provided on the taper portion 4, the plate thickness of the portion provided with the protrusion 16g is naturally increased, the rigidity is increased, and the rigidity of the entire taper portion 4 is improved.

In the steel pipe pile 1G in which the protrusion 16g is provided on the outer peripheral surface 2 of the tapered portion 4 as described above, the following effects (1) to (4) can be expected.
(1) At the time of pile press-fitting construction, the ground (soil) in the vicinity of the outer peripheral surface 2 of the tapered portion 4 can be efficiently and actively destroyed (sheared) by the protrusions 16g to facilitate the rotary insertion of the pile. it can.
(2) The wear and deformation of the taper portion 4 which is an important member for exerting the pile bearing capacity performance by the protrusion 16g portion taking on the wear and deformation caused by the resistance of the ground at the taper portion 4 originally. It can suppress, and the soundness (safety) of a pile body can be improved significantly.
(3) By providing the projection 16g by connecting to the top surface of the excavation bit 6, the earth and sand excavated by the excavation bit 6 flows upward along the projection 16g, so that the resistance of the pile construction is reduced.
(4) The protrusion 16g is provided with an attachment angle δ so as to intersect the axis in the direction of the central axis C of the steel pipe pile 1G, so that when the pile is rotated, the protrusion 16g is sheared by the protrusion 16g. An effect of causing the broken soil to flow upward by the protrusions 16g can be exhibited. Furthermore, the ground resistance when constructing the pile can be reduced.
In this test, although demonstrated using the steel pipe pile 1G of 7th Embodiment, even if it uses the steel pipe pile 1A-1F of other embodiment, the same effect can be acquired.

  In the present invention, the hard ground means a rock, and the rock is divided into a soft rock mass (uniaxial compressive strength to less than 20 MPa) and a hard rock mass (uniaxial compressive strength: 20 MPa or more). Steel pipe pile 1A-1G with a taper part protrusion is applicable to any rock mass in the form provided with the excavation bit 6. FIG.

  As the cross-sectional form in the longitudinal direction of the pile on the outer peripheral surface 2 of the tapered portion 4 and the inner peripheral surface 3 of the tapered portion 4, the outer side and the inner side are as shown in FIG. It may be linear, and although not shown, it may be curved. As a cross-sectional configuration in the length direction of the pile on the outer peripheral surface 2 of the taper portion 4 and the inner peripheral surface 3 of the taper portion 4, it protrudes outward in the radial direction from the top of the pile central axis (concave inward in the radial direction). However, it may be convex toward the inside in the radial direction from the top of the pile center axis (concave toward the outside in the radial direction). When the protrusions 16a to 16e and 16g are provided, they are directly installed on the outer peripheral surface 2 of the tapered portion 4.

Next, the dimension and effect | action of the taper part 4 of this invention are demonstrated. Here, FIGS. 13A and 13B are views in which the protrusions a to 16e and 16g are omitted.
As described above, by providing the tapered portion 4 whose diameter is reduced at the tip 4a side of the steel pipe piles 1A to 1G, as shown by the arrow C1 in FIG. 13B and the arrow C1 in FIG. It is possible to reduce the soil flowing into the pipe. Further, by reducing the opening area of the tapered portion 4, as shown by the arrow C1 in FIG. 13B and the arrow C1 in FIG. 15, the soil flowing into the pipe can be reduced and diffused in the radial direction. By these, the pile front-end | tip part suppresses generation | occurrence | production of the obstruction | occlusion by pipe soil, reduces the friction with pipe inner soil and the internal peripheral surface 3 of pile 1A-1G, and makes it possible to aim at reduction of pile pushing force.

  By providing the taper part 4 at the tip of the pile, the resistance of the soil acting on the inner peripheral surface 3 of the taper part 4 increases, but by adopting a method of rotary press-fitting construction, the friction on the pile peripheral surface is increased. It also takes advantage of the fact that it can be suppressed. Furthermore, by providing the protrusions 16a to 16e and 16g, the soil acting on the inner peripheral surface 3 of the tapered portion 4 can be promoted to move upward from the inner peripheral surface 3, and the resistance of the soil is reduced.

  The diameter reduction ratio, which is the ratio between the outer diameter D2 of the tip 4a of the tapered portion 4 and the outer diameter D1 of the constant diameter portion where the outer diameter of the steel pipe pile is constant, is small, and the pile longitudinal direction (axial direction) of the tapered portion 4 If the ratio (H1 / D1) between the length H1 of the taper and the outer diameter dimension D1 of the constant diameter portion having a constant outer diameter becomes too small (in other words, the taper angle θ (°) of the tapered portion 4 becomes too large). And), the resistance due to the surface pressure acting on the tapered portion 4 is increased during the rotary press-fitting. As a result, construction failure may occur. Therefore, in the embodiment, by restricting these ratios within a predetermined range, it is possible to achieve good rotational press fitting workability. In the present invention, the length H1 of the tapered portion 4 in the pile length direction (same as the direction of the central axis C of the steel pipe pile), the outer diameter D2 at the tip of the tapered portion 4, and the constant diameter is constant. There is a relationship of tan θ = (D1−D2) / 2H1 between the outer diameter D1 of the portion and the taper angle θ. Further, at the time of construction, the taper portion 4 has a pile penetration direction and a taper angle θ in addition to the movement in which the rotation direction and the penetration direction vertical are combined with the ground. As a result, the effect of spreading the ground sideways while simultaneously applying the shearing force and the compressive force to the ground is exhibited. Therefore, the ground can be disturbed efficiently, and the resistance during construction of the tapered portion 4 is reduced.

Providing the tapered portion 4 increases the projected area of the bottom surface of the pile, so that when the taper portion 4 penetrates into the support layer, a reliable support force can be obtained by the tapered portion 4. In order to secure the supporting force with the open-ended pile having the open end 4a, a reliable supporting force can be exhibited even if the blockage in the pipe is insufficient. Since a high compressive load can be borne at the bottom projected area of the tapered portion 4, the steel pipe piles 1 </ b> A to 1 </ b> G exhibit a higher supporting force than when a normal straight open-ended pile is inserted by rotational press-fitting. Can do.
Furthermore, in the hard ground where the restraining pressure of the ground is sufficient, the steel pipe piles 1 </ b> A to 1 </ b> G surely exhibit a high supporting force. Therefore, a higher supporting force can be expected than when a straight steel pipe pile with a closed end 4a is inserted by rotary press-fitting.
When the steel pipe piles 1A to 1G are rotary press-fitted, during the construction, the steel pipe piles 1A to 1G are repeatedly moved up and down alternately in the ground, so that the soil in the pipe moves below the pipe during the up movement. It falls and the soil that falls when moving down is pushed out of the pipe. As a result, as shown in FIGS. 15 and 16, the height of the soil in the pipe can be lowered, and the contact surface between the inner peripheral surface 12 of the constant diameter portion 9 and the pipe inner soil 14 can be reduced. As a result, since the friction between the inner peripheral surface 12 and the pipe soil 14 is reduced, the construction load can be further reduced.

In the present invention, the ratio (H1 / D1) between the length H1 of the tapered portion 4 in the pile longitudinal direction and the outer diameter D1 of the constant diameter portion 9 having a constant outer diameter is set to 0.3 to 5.5. The That is, H1 / D1 is set to 0.3 to 5.5.
Further, the diameter reduction ratio (D2 / D1), which is the ratio (D2 / D1) between the outer diameter dimension D2 of the tip of the tapered portion and the outer diameter dimension D1 of the constant diameter portion 9 having a constant outer diameter of the steel pipe pile, is 0. The outer diameter D2 is set to be smaller than the outer diameter D1 so as to be in the range of .60 to 0.95.

The reason why H1 / D1 is set to 0.3 to 5.5 as described above and the reason why the outer diameter D2 of the steel pipe piles 1A to 1G is set will be described with reference to FIGS. Here, since the shape of the taper part 4 is the same in all the steel pipe piles 1A to 1G, description will be given with reference to the steel pipe pile 1A.
First, with reference to FIG. 19, when the diameter reduction ratio (D2 / D1) is 0.9, the length H1 of the taper portion 4 in the direction of the central axis C and the constant diameter with a constant outer diameter. The ratio (H1 / D1) with the outer diameter D1 of the portion 9 and the necessary pushing force ratio (the ratio between the necessary pushing force of the steel pipe pile 1A having the tapered portion 4 and the necessary pushing force of the straight steel pipe pile 10) It is the graph which investigated this relationship by experiment.
The steel pipe pile 1A used in the experiment has an outer diameter dimension (D1) of the constant diameter portion 9 of 100 mm, a thickness (t) of the steel pipe portion of 4.2 mm, and an outer diameter dimension of the tip 4a of the tapered portion 4 ( D2) is 90 mm. Further, the outer diameter dimension (D1) of the straight steel pipe pile 10 having a constant outer diameter dimension (D1) over the entire length and the thickness (t) of the steel pipe portion are the same as those of the steel pipe pile 1A.

From FIG. 19, when H1 / D1 is 0.3, the necessary pushing force ratio is 0.9, and when H1 / D1 is 0.4, the necessary pushing force ratio is 0.6. It can be seen that when H1 / D1 is 1.35, the required pushing force ratio is 0.6, and when H1 / D1 is 5.5, the necessary pushing force ratio is 0.90. From this, when the ratio (H1 / D1) between the length H1 of the tapered portion 4 in the direction of the central axis C and the outer diameter D1 of the constant diameter portion 9 having a constant outer diameter is 0.3 to 5.5. That is, when H1 / D1 is 0.3 to 5.5, the necessary pushing force ratio is 0.9 or less, and the steel pipe pile 1A is at least 10% compared to the straight steel pipe pile 10 shown in FIG. 22A. It can be seen that the necessary pushing force can be reduced.
In addition, when H1 / D1 is 0.40 to 1.35, the required pushing force ratio is 0.6 or less, and the steel pipe pile 1A reduces the necessary pushing force by 40% compared to the straight steel pipe pile 10. You can see that you can.

  FIG. 20 shows a curve obtained by plotting experimental values. This figure shows a reduction ratio (D2) which is a ratio of the outer diameter D2 of the tip 4a and the outer diameter D1 of the constant diameter portion 9. / D1) is a graph in which the required indentation force ratio is examined and compared for steel pipe piles 1A with various diameter reduction ratios on the horizontal axis.

As shown in FIG. 20, when the diameter reduction ratio (D2 / D1) is 0.60, the necessary pushing force ratio is 0.9, and when the diameter reduction ratio (D2 / D1) is 0.75, the necessary pushing force is obtained. When the force ratio is 0.6 and the diameter reduction ratio (D2 / D1) is 0.92, the necessary pushing force ratio is 0.60, and when the diameter reduction ratio (D2 / D1) is 0.95, It can be seen that the necessary pushing force ratio is 0.90.
From these downwardly convex graphs shown in FIG. 19 and FIG. 20, the necessary pushing force ratio is reduced to 0.90 or less when the diameter reduction ratio (D2 / D1) is in the range of 0.60 to 0.95. The pushing force can be reduced by at least 10%. Further, it can be seen that when the diameter reduction ratio (D2 / D1) is in the range of 0.75 to 0.92, the necessary pushing force ratio becomes 0.60 or less, and the necessary pushing force can be reduced by 40%.
Therefore, it is preferable that H1 / D1 is set to 0.3 to 5.5 and the diameter reduction ratio (D2 / D1) is set to 0.60 to 0.95, and more preferably, H1 / D1 is set to 0.3 to 5. And the diameter reduction ratio (D2 / D1) is preferably in the range of 0.75 to 0.92.

When the pushing force ratio falls below 0.9, the counterweight (weight) can be greatly reduced. For example, in the case of a rotary press-in construction facility having a required push-in force of 86 t (tons), a reaction force weight of 66 t (tons), and a rotary press-in construction machine weight of 20 t (tons), the required push-in force can be reduced by 10% to 8.6 t (tons). The counter weight can be reduced by 13%.
Further, as shown in FIG. 19, if H1 / D1 is 0.40 to 1.35, the necessary pushing force ratio can be reduced to 0.6 or less, and it can be seen that the counter weight can be further reduced. Thus, when the required pushing force ratio is set to 0.6 or less, it is particularly desirable because the rotary press-fitting machine can be rotary press-fitted with a small rotary press-fitting machine one step below.

A resistance reduction mechanism when the steel pipe pile 1A is rotationally press-fitted into the ground will be described with reference to FIGS. 21A and 21B. In FIG. 21B, the figure which abbreviate | omitted the protrusion 16a and the excavation bit 6 which are provided in the steel pipe pile 1A is shown.
In the straight steel pipe pile 10 of FIG. 21A and the steel pipe pile 1A of FIG. 21B, a and a ′ are resistances at the tip closing part, b is resistance at the tip outer peripheral surface, b ′ is resistance by the taper part 4, and c and c ′. Is a resistance due to friction of the outer peripheral surface 2 of the tapered portion 4, and τ is a resistance due to the soil in the pipe.
In such a case, since a = τ in FIG. 21A, if H1 / D1 is reduced (in other words, the taper angle (θ) of the taper portion 4 is increased) as shown in FIG. The resistance b ′ increases. Further, in FIG. 21B, when the diameter reduction rate of the tapered portion 4 is increased, the resistance a ′ at the tip closing portion is decreased, and the resistance b ′ by the tapered portion 4 is increased, as shown in FIGS. 21A and 21B. As shown, the horizontal portion (in the range of about 70% to 80% in terms of diameter reduction ratio) is a range that is balanced by the effect of the increase or decrease in these resistances.

  The tapered portion 4 of the steel pipe pile 1A of the present invention has the above-described action, and further, the tapered portion 4 is provided with the protrusion 16a, so that the resistance due to the contact between the tapered portion 4 and the ground contacts the tapered portion 4. The soil can be actively sheared and reduced. Moreover, it can be efficiently crushed by adjusting the inclination angle δ of the protrusion 16a to 30 ° to 50 ° and the internal friction angle φ of the normal ground.

The sharp portion 5 sharpened toward the excavation direction A1 may be the sharp portion 5 sharpened toward the excavation direction A1. In the above case, a portion sharpened in the circumferential direction of the pile may be provided.
As in these forms, if the tip 4a of the tapered portion 4 is provided with a sharp portion 5 sharpened in the excavation direction A1, even if the ground is hard, the excavation bit 6 and the sharp portion 5 or The sharpened portion 5 also serving as the excavating bit 6 of the tapered portion 4 allows the steel pipe pile to penetrate into the ground while destroying or excavating the tip portion ground at the time of pile driving construction.

When constructing the steel pipe piles 1A to 1G of the present invention as described above or the steel pipe pile 17 that does not have a protrusion, as in the conventional case, it is applied to the ground by a rotary press-fitting method that applies rotational force and pushing force to the steel pipe pile. Just press fit. When the rotary press-fitting construction machine 7 as shown in FIG. 9 grips the peripheral side surface of the steel pipe pile 17 or the like with the tip tapered portion, and the rotary press-fitting construction is performed, the outer diameter dimension of the conventional steel pipe pile 10, that is, the steel pipe pile. Compared to the case of constructing a straight steel pipe pile 10 having the same D1 and its thickness t, the steel pipe piles 1A to 1G of the present invention have an intrusion amount per pushing force shown in FIG. 17 and a tip load degree shown in FIG. It can be seen that it is excellent in terms of (kN / m ² ).

More specifically, FIG. 17 shows a pressing force per closed cross-sectional area of the pile, which is a construction load at the time of construction using a pile having an outer diameter D1 and an outer diameter D2 at the tip of the tapered portion 4 as shown in FIG. The relationship of (kN / m ² ) −penetration / pile diameter (H2 / D1) is shown. It can be seen that the penetration amount of the steel pipe piles 1A to 1G of the present invention is larger than that of a straight steel pipe pile (shown as a straight pile in FIG. 17) as shown in FIG. 22A.
Further, FIG. 18 shows a tip load degree (kN / m ² ) when a static load is applied after rotating and press-fitting a steel pipe in a hard ground for a length three times the outer diameter D1. -The relationship of tip settlement / pile diameter (D1) is shown. As can be seen from FIG. 18, the steel pipe piles 1 </ b> A to 1 </ b> G according to the present invention have a large tip load degree and a high supporting force as compared with the straight pile.

  When constructing the steel pipe piles 1A to 1G of the present invention or the steel pipe pile 17 not provided with the protrusions, the steel pipe piles 1A to 1G may be penetrated to the support layer under the soft ground or may be rotationally pressed into the ground including the hard ground.

When constructing the steel pipe piles 1A to 1G of the present invention, when the steel pipe piles 1A to 1G are moved up and down in the ground during the construction, the height of the soil (inner pipe soil) in the steel pipe pile is lowered. 15 and 16, the adhesion area between the pipe soil and the inner peripheral surface 12 in the steel pipe piles 1A to 1G is reduced. Thereby, since the adhesion area is reduced, the resistance is reduced, the burden on the construction machine is reduced, and the construction can be performed efficiently.
As a means for moving the steel pipe piles 1A to 1G up and down, a telescopic jack such as a hydraulic type in the rotary press fitting machine 7 with the rotary pipe fitting machine 7 holding the steel pipe piles 1A to 1G with the tapered end projections. 13 is expanded and contracted. Thereby, steel pipe pile 1A-1G can be moved up and down easily.
Moreover, in the construction method of the steel pipe piles 1A to 1G, when the tapered portion 4 of the steel pipe piles 1A to 1G is finally stopped in the support layer, the steel pipe piles 1A to 1G are reversely rotated, and the protrusions 16a to 16e, The soil (shear including crushed stone) near the tapered outer peripheral surface is pushed downward by 16 g. As a result, the protrusions 16a to 16e and 16g can push the soil near the tapered outer peripheral surface (slipping including crushed stone and the like) downward, and the support layer on the lower surface side of the pile can be made dense to support the pile.

  As an example of the manufacturing method of the steel pipe main body portions such as the steel pipe piles 1A to 1G of the present invention, the taper portion of one steel pipe pile may be manufactured by cold bending. Moreover, you may manufacture so that a taper part may be formed by cold press molding. Alternatively, the belt-shaped steel plate is formed into a fan shape, and the fan-shaped steel plate with protrusions is processed into a taper shape by cold bending, and both side edges are joined by welding. Then, a tapered short pipe having the same outer diameter as the steel pipe to which the outer diameter portion is to be connected is manufactured, and the upper end portion of the tapered short pipe is fixed to the tapered portion of one steel pipe by welding. A steel pipe pile body may be manufactured. Moreover, you may manufacture the steel pipe pile main body which has a taper part by plastically processing the taper part of one steel pipe. A steel pipe pile with a tip tapered portion protrusion may be manufactured by fixing a holder having a drilling bit to such various types of tapered portions and providing a protrusion by welding or the like. The strip-shaped steel plate with a single-sided projection is made into a fan-shaped steel plate with a projection, and a tapered short tube is manufactured, and the upper end of the tapered short tube is fixed to the tapered portion of one steel pipe by welding. You may make it manufacture the steel pipe pile etc. with a taper part protrusion.

A1 Excavation direction C Center axis C2 Center axis D1 in the extending direction of the projection D1 Outer dimension D2 of the constant diameter portion External dimensions 1A, 1B, 1C, 1D, 1E, 1F, 1G Steel pipe pile 2 Outer surface 3 Inner surface 4 Taper (tip)
4a Tip (front end)
5,5b Pointed portion 6 Drilling bit 8 Support layer 9 Constant diameter portion 15 Ground 16a to 16e, 16g Protrusion 16e Lower end of the protrusion

Claims (14)

A steel pipe pile that is open and hollow at the front end in the excavation direction,
A constant diameter portion having a constant outer diameter, and a tip portion in which the inner shape and the outer size gradually decrease toward the front end;
Protrusions that extend partially or entirely from the front end toward the rear end and project outward in the radial direction of the tip end portion are provided on the outer peripheral surface of the tip end portion ;
The ratio of the height dimension of the tip portion in the length direction to the outer dimension of the constant diameter portion is 0.3 to 5.5;
A steel pipe pile characterized by that. The steel pipe pile according to claim 1, wherein a plurality of the protrusions are provided at intervals in the circumferential direction of the outer peripheral surface of the tip portion. 3. The steel pipe pile according to claim 1, wherein the protrusion is inclined such that the rear end side of the protrusion is behind the constant diameter portion and the tip end in the rotation direction. The protrusion is disposed to be inclined in the circumferential direction with respect to the central axis of the tip;
Angle between the center axis of the extending direction of the projections with a plane normal to the central axis, according to any one of claims 1 to 3, characterized in that it is 20 ° to 70 ° Steel pipe pile. Said projection than said outside dimension of the constant diameter portion, so as to be located inside the radial direction of the tip, according to claim 1 to claim, characterized in that the height of the protrusions is defined The steel pipe pile as described in any one of 4 . The steel pipe pile according to any one of claims 1 to 5, wherein a plurality of excavation bits are provided at intervals in the circumferential direction of the front end. The steel pipe pile according to any one of claims 1 to 6 , wherein a lower end of the protrusion is located immediately above an upper surface of the excavation bit. The steel pipe according to any one of claims 1 to 7, wherein the excavation bit is arranged on the inner side in the radial direction of the tip portion than an outer dimension of the constant diameter portion. Pile. The ratio of the outer diameter dimension of the said front end with respect to the outer diameter dimension of the said constant diameter part is 0.60-0.95, The steel pipe pile as described in any one of Claim 1 thru | or 8 characterized by the above-mentioned. . The steel pipe pile according to any one of claims 1 to 9 , wherein a pointed portion protruding from the front end and sharpened in the excavation direction is provided at the tip portion. A steel pipe pile construction method using the steel pipe pile according to any one of claims 1 to 10 ,
A method for constructing a steel pipe pile, wherein the steel pipe pile is press-fitted while the ground is sheared and destroyed by the protrusion when the steel pipe pile is press-fitted into the ground by a rotary press-fitting method that applies a rotational force and an indentation force to the steel pipe pile. The steel pipe pile construction method according to claim 11 , wherein the steel pipe pile is rotationally press-fitted into the ground including the hard ground. During construction, the height of the soil in the steel pipe pile is lowered by rotating the steel pipe pile in the ground, moving it up or down without adding rotation or combining them. The construction method of the steel pipe pile of Claim 11 . When the tip portion of the steel pipe pile is finally stopped in a support layer, the steel pipe pile is reversely rotated, and the protrusion near the outer peripheral surface of the tip portion is pushed downward. The construction method of the steel pipe pile of Claim 11 .

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