JP5229247B2 - Steel pipe pile construction method and steel pipe pile foundation - Google Patents

Description

The present invention relates to construction methods and the steel pipe Kuimoto foundation of the steel pipe pile, particularly, a method and construction of the available steel pipe pile when penetrating the steel pipe pile in the ground by the rotary press fitting method, and the helical projection on the inner surface concerning the steel pipe pile having a steel pipe Kuimoto foundation that is built to penetrate the ground by the construction method.

Conventionally, steel pipe piles constructed by penetrating into the ground while rotating a steel pipe having a tip bit or a spiral blade are known (for example, see Patent Documents 1 to 4).
In the steel pipe pile described in Patent Document 1, spiral protrusions are formed on the inner peripheral surface and the outer peripheral surface of the steel pipe, respectively, and the protrusions on the outer peripheral surface are screwed into the ground to dig, and reversely swivel with the protrusions on the outer peripheral surface. By tightening the earth and sand inside the steel pipe with the projections on the inner peripheral surface formed in the above, the blocking effect of the pipe inner soil is enhanced and the tip support force is improved.
Moreover, the steel pipe pile described in Patent Document 2 is penetrated into the ground by the digging force of the blade on the outer peripheral surface of the tip, and is formed by an annular protrusion (opening rib) formed on the inner peripheral surface near the tip of the steel pipe. By closing the pipe soil and forming a support bottom at the tip of the steel pipe, the tip support force can be improved while reducing rotational torque.

On the other hand, the steel pipe pile described in Patent Document 3 is penetrated into the ground by the digging force of the blades on the outer peripheral surface of the tip, and the protrusion on the inner peripheral surface of the steel pipe formed in a spiral shape in the same turning direction as the blades By taking in the earth and sand, the straight soil is improved while preventing the soil in the pipe from being blocked and reducing the rotational torque.
Moreover, the steel pipe pile described in patent document 4 is penetrated into the ground by excavating the ground with a tip bit by rotational press-fitting. And at the time of excavation of the intermediate layer, by pushing out the soil with the tip bit to the outside, blockage of the soil in the pipe is prevented, the rotational torque is reduced, and after reaching the support layer, the soil is taken into the steel pipe by reverse rotation, The blocking effect of the soil in the pipe is enhanced to improve the tip support force.

Japanese Patent Laid-Open No. 4-85415 JP-A-8-226124 JP 2005-299192 A JP 2009-249893 A

By the way, as in the steel pipe piles described in Patent Documents 1 and 2, it is preferable to take in the soil inside the steel pipe and close it, but it is preferable in terms of improving the tip support force, but the press-fit resistance during construction increases. Inconvenience that the performance is lowered.
For such inconvenience, as in the steel pipe pile described in Patent Document 3, the protrusion on the inner peripheral surface of the steel pipe is formed in the same turning direction as the blade, and is configured to take in the soil upward inside the steel pipe. However, since the pipe soil is gradually blocked by the frictional resistance between the inner peripheral surface of the steel pipe and the pipe inner soil, the press-fitting resistance increases with penetration.
Moreover, although the amount of earth and sand which flows into the inside of a steel pipe can be adjusted by adjusting the angle of a tip bit like the steel pipe pile described in patent document 4, the amount of earth and sand which increases with penetration is constant. If the amount is exceeded, a clogging phenomenon of the soil in the pipe may occur, and it is difficult to sufficiently eliminate the above disadvantages.

An object of the present invention, it is possible to suppress an increase in the press-in resistance by adjusting the blockage in the tube soil caused by rotation press fitting, the construction method and steel Kuimoto foundation of steel pipe pile that can improve the workability It is to provide.

The present invention is intended to suppress the increase in press-fit resistance by adjusting the blockage phenomenon by paying attention to the generation mechanism of the blockage phenomenon of the pipe soil.
Specifically, as shown in FIG. 8, friction forces F <b> 1 and F <b> 2 are expressed in the earth and sand flowing into the steel pipe P and the inner peripheral surface P <b> 1 of the steel pipe at the time of construction. During construction (that is, when the steel pipe P moves downward), the pipe soil S1 receives a downward frictional force F1. This downward frictional force F1 becomes a downward compressive stress C1 on the earth and sand in the vicinity of the inner peripheral surface P1 of the steel pipe, and is transmitted downward of the pipe inner soil S1. On the other hand, in the pipe soil S2 that is positioned below the pipe soil S1 that receives the compressive stress C1, the earth pressure level rises due to the downward compressive stress C2, and the earth pressure H3 acting in the pipe increases as an action. Will be allowed to. As described above, the increase in the compressive stresses C1 and C2 and the increase in the horizontal earth pressure H3 acting on the inner peripheral surface P1 of the steel pipe are sequentially transmitted from the upper part to the lower part of the pipe inner soils S1 and S2 from the friction force F1. As a result, the frictional force F3 in the pipe is rapidly increased, and as a result, the downward compressive stress C3 in the pipe soil S2 is increased until it exceeds the fracture strength of the ground, resulting in a blockage phenomenon.

  As a result of intensive studies based on the mechanism of the blockage phenomenon as described above, the superposition phenomenon of the frictional forces F1 to F3 in the pipe that cause the blockage phenomenon and the earth pressure stresses C1 to C3 in the vertical direction is suppressed. In addition, or by promoting it, it became clear that the blockage of the pipe soils S1, S2 can be adjusted. The present invention adjusts the downward compressive stresses C1 to C3 that are increased according to the frictional forces F1 to F3, thereby adjusting the blockage of the pipe soils S1 and S2 and suppressing an increase in press-fit resistance. In order to obtain, the following configuration is provided.

  The steel pipe pile construction method of the present invention is a steel pipe pile construction method in which a steel pipe pile having a spiral projection on the inner surface is rotationally press-fitted into the ground, and the downward inclination angle formed by the spiral projection and the steel pipe shaft. And the rotation direction of the steel pipe pile is set so that the construction angle formed by the rotational displacement amount and the vertical displacement amount at the time of rotary press-fitting is in the same quadrant, and the construction angle is larger than the inclination angle of the protrusion. As such, it comprises a first rotary press-fitting step of rotary press-fitting while adjusting at least one of the rotational speed and press-fitting speed of the steel pipe pile.

According to the present invention described above, the construction angle formed by the rotational displacement amount and the vertical displacement amount at the time of rotational press-fitting is larger than the inclination angle of the spiral projection formed on the inner surface of the steel pipe and the same inclination angle. In addition, by adjusting the rotation speed and the press-fitting speed, the protrusions can push up the pipe inner soil to be closed along with the press-fitting, and the downward compressive stress generated in the pipe inner soil can be eliminated or reduced. Therefore, in the first rotary press-fitting process, the steel pipe pile is rotary press-fitted while adjusting the clogging phenomenon of the in-pipe soil, so that the increase in press-fitting resistance due to penetration can be effectively suppressed, and the increase in rotational torque is suppressed. Workability can be improved.
As a method for adjusting the rotational speed and the press-fitting speed in the first rotary press-fitting step, only the rotational speed may be adjusted, only the press-fitting speed may be adjusted, or both the rotational speed and the press-fitting speed may be adjusted. May be adjusted. Here, specifically, the rotational speed may be increased (the rotational displacement amount is increased) or the press-fit speed with respect to the combination of the rotational speed and the press-fit speed at which the inclination angle of the protrusion and the construction angle are the same. (The amount of vertical displacement can be reduced), the rotational speed can be increased and the press-fitting speed can be decreased, and the construction angle can be made larger than the inclination angle of the protrusions by any adjustment method. it can.

At this time, the method for constructing the steel pipe pile of the present invention is such that the construction angle is the same as the inclination angle of the protrusion, or the rotation at the time of rotational press-fitting so that the construction angle is smaller than the inclination angle of the protrusion. It is preferable to provide a second rotary press-fitting step of rotary press-fitting while adjusting at least one of the speed and the press-fitting speed.
Furthermore, it is preferable that the second rotary press-fitting step is performed when the tip of the steel pipe pile is penetrated into the support layer.
According to such a configuration, by performing the second rotary press-fitting process as necessary, the clogging phenomenon can be adjusted so that the soil in the pipe is clogged, for example, it penetrates into the support layer at the final stage of construction. In doing so, the tip support force can be ensured by promoting the blockage of the soil in the pipe.
In the above second rotational press-fitting process, the rotational speed and the press-fitting speed may be adjusted so that the inclination angle of the protrusion and the construction angle are the same, or conversely to the first rotational press-fitting process, For a combination with the same inclination angle and construction angle, reduce the rotational speed (decrease rotational displacement), increase the press-fit speed (increase vertical displacement), further reduce the rotational speed and press-fit By increasing the speed, the construction angle may be adjusted to be smaller than the inclination angle of the protrusion.

Moreover, in the construction method of the steel pipe pile of this invention, when stopping the said steel pipe pile, it is preferable to implement the reverse rotation process which reversely rotates the said steel pipe pile and compacts the soil inside the said steel pipe pile.
If such a reverse rotation process is carried out, the projections can push down the inner soil of the tube and compact the inner soil of the tube, thereby further promoting the blockage and improving the tip support force. Can do.

Moreover, the steel pipe pile foundation of the present invention is constructed by penetrating a steel pipe pile having a spiral protrusion on the inner surface into the ground by any one of the above construction methods.
According to such a steel pipe pile foundation, the same effect as the construction method described above can be obtained, and a pile foundation that secures a high end support force while reducing construction cost and shortening the construction period by improving workability. Can be built .

According to construction methods and the steel pipe Kuimoto foundation of the steel pipe pile of the present invention as described above, such as or to promote the reduction or closing the closure of the tube soil caused by rotation press fitting, it is possible to adjust the blockage appropriately Therefore, it is possible to improve the workability by suppressing the increase of the press-fit resistance, and it is possible to increase the tip support force by promoting the blocking as necessary.

It is sectional drawing which shows a part of steel pipe pile foundation of this invention. It is a figure explaining the effect | action of the steel pipe pile used for the said steel pipe pile foundation. It is a figure explaining the rotation press-fitting method of the said steel pipe pile. It is a figure explaining the effect | action of the protrusion of the said steel pipe pile. It is a graph which shows the experimental result using the said steel pipe pile. It is a figure explaining the other effect | action of the said protrusion. It is sectional drawing which shows the steel pipe pile which concerns on the modification of this invention. It is a figure explaining the effect | action at the time of the press fit in a general steel pipe pile.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, the steel pipe pile foundation 1 is provided with the steel pipe pile 2 penetrated into the ground G. The steel pipe pile 2 is inserted into the ground G by a rotary press-fitting method that is rotated and pressed by a pile driving machine, and a plurality of ribs 4 that are spiral protrusions are formed on the inner peripheral surface 3 thereof. It consists of a spiral steel pipe with internal ribs. The rib 4 is formed in a spiral shape clockwise in the depth direction (downward in FIG. 1), and its inclination is defined as an inclination angle θ1 formed with the steel pipe axis Z as shown in FIG.

  When the steel pipe pile 2 is rotated and penetrated, as shown in FIG. 2, the pipe inner soil S is forced to give an upward relative displacement δ in the vicinity of the inner peripheral surface 3 in the pipe inner soil S. It is possible to generate an upward stress T with respect to S and to reduce a downward compressive stress C that causes blockage of the in-pipe soil S. As shown in FIG. 3, for example, when a vertical downward load Q is applied to the steel pipe pile 2 to generate a downward displacement D1 of 10 mm, the pipe soil S also moves downward by 10 mm. When the inclination angle θ1 of 4 and the press-fit rotation angle (construction angle) θ2 at the time of construction are set appropriately, the downward displacement of the rib 4 can be made 10 mm or less (for example, 6 mm). Here, the press-fit rotation angle θ2 is defined by an angle constituted by the vertical downward displacement D1 of the steel pipe pile 2 and the rotational displacement amount D2 accompanying the load R in the rotation direction. In this way, the pipe soil S relatively receives an upward displacement of 4 mm from the rib 4, and a force to move upward acts, so that it is possible to promote a decrease in the downward compressive stress C. Become. Note that the press-fit rotation angle θ2 is a simple rotation construction state in which the steel pipe pile 2 is rotated and the vertical displacement D1 is zero, and the upper limit is 90 degrees. The range is limited.

  In order to forcibly apply upward stress T to the pipe soil S as described above, it is necessary to apply an upward relative displacement δ to the steel pipe pile 2 to the pipe soil S, particularly to the sand near the inner peripheral surface 3 of the steel pipe. is there. Therefore, as shown in FIG. 4, when attention is paid to a part of the rib 4A in the steel pipe pile 2 at the time of the rotary press-fitting, the rib 4A has a vertical downward displacement (vertical displacement amount) D1 and a rotational displacement amount D2 of the steel pipe pile 2. Along with this, the rib 4B moves downward in the right direction in FIG. 4 (path K1). On the other hand, this movement is conceptually a path K2 (the movement of earth and sand hardly occurs) that is a movement to the virtual rib 4C that is the direction along the inclination angle θ1 of the rib 4, and from this virtual rib 4C. Since it is composed of two elements, a path K3 (uplifting earth and sand) that is an upward movement toward the upper rib 4B, the earth and sand near the inner peripheral surface 3 shown in FIG. By applying an upward stress T to the pipe inner soil S in that portion, it becomes possible to release the downward compressive stress C on the lower side of the rib 4 as a result. The configuration conditions of the inclination angle θ1 and the press-fit rotation angle θ2 of the rib 4 for causing the above phenomenon are such that the tilt angle θ1 <the press-fit rotation angle θ2, and the lower limit and upper limit conditions of the press-fit rotation angle θ2 are 0 degrees. <Inclination angle θ1 <Press-fit rotation angle θ2 <90 degrees. And the construction process which rotationally press-fits the steel pipe pile 2 to the ground G based on the structural conditions of such inclination angle (theta) 1 and press-fit rotation angle (theta) 2 of a rib 4 is set as a 1st rotation press-fit process.

The experimental results verifying the above effects are shown in the graph of FIG.
In this experiment, a steel pipe was used as a model test sample, a normal steel pipe with and without an inner spiral protrusion was prepared, and this was rotationally pressed into a sand ground composed of dry sand. The steel pipe diameter is 100 mm, the inner surface spiral protrusion height is 3 mm (about 3% of the pile diameter), and the inner surface spiral is installed only in the range from the vicinity of the pile tip to the same length as the pile diameter.
Comparing the results of the steel pipe with inner spiral protrusion (shown by A in FIG. 5) and the normal steel pipe without protrusion (shown by B in FIG. 5), there is a big difference since the penetration / pile diameter exceeded 3.0 times Is seen. That is, in the normal steel pipe (B), the penetration force tends to increase even if it exceeds 3.0 times, whereas in the steel pipe with the inner spiral (A), the penetration force converges to a constant value and increases further. Is not seen.
Here, it is generally said that the blockage occurs when the penetration amount / pile diameter becomes about 3 to 5 times, but the result of the normal steel pipe reproduces this phenomenon. On the other hand, in the steel pipe with an inner surface spiral, it was confirmed that the increase of the penetration force beyond the converged value could be suppressed because the occurrence of the blockage can be suppressed as described above.
From the above results, it can be seen that the inner spiral does not need to be installed on the entire length of the pile, and it is effective to be installed only in the vicinity of the tip of the pile. As inferred from the results of this experiment and the amount of penetration that causes general blockage, it is desirable from the viewpoint of processing cost control that the spiral installation range is in the range of 1 to 5 times the pile diameter from the pile tip.

Further, following the first rotary press-fitting step as described above, when the steel pipe pile 2 is penetrated into the support layer and the steel pipe pile 2 is stopped, it is desirable to exert the tip support force. Then, the following second rotary press-fitting process is carried out so as to promote the blocking of the in-pipe soil S.
The second rotational press-fitting process corresponds to the first rotational press-fitting process by changing the press-fitting rotation angle formed by the vertical downward displacement D1 and the rotational displacement amount D2 of the steel pipe pile 2 from θ2 to θ2 ′. Specifically, as shown in FIG. 6, the configuration conditions of the inclination angle θ1 and the press-fit rotation angle θ2 ′ of the rib 4 are changed. In this case, the rib 4A moves toward the rib 4D according to the press-fitting rotation angle θ2 ′ (path K4), but this movement conceptually moves to the virtual rib 4C according to the inclination angle θ1. The path K2 (the movement of earth and sand hardly occurs) and the path K5 which is a downward movement from the virtual rib 4C to the lower rib 4D are included in the movement of the path K5. By causing the action of pushing the pipe soil S downward according to the minutes, the blockage of the pipe soil S can be promoted.

Further, when the steel pipe pile 2 is clamped after the second rotary press-fitting process or in place of the second rotary press-fitting process, the rotation direction of the steel pipe pile 2 in the first rotary press-fit process (in this embodiment, clockwise downward) ) May be reversely rotated (rotated counterclockwise downward). By performing such a reverse rotation process, the pipe soil S can be pushed downward by the ribs 4 to further promote the blockage of the pipe soil S.
Accordingly, in the first rotational press-fitting process until the tip of the steel pipe pile 2 reaches the support layer, the vertical downward displacement D1 and the rotational displacement amount D2 of the steel pipe pile 2 are set such that the inclination angle θ1 <the press-fit rotational angle θ2. The steel pipe pile 2 is rotationally press-fitted while adjusting the pressure, so that upward stress T is applied to the pipe soil S and the friction force F with the steel pipe inner peripheral surface 3 is reduced, thereby suppressing the blockage of the pipe soil S. It is possible to improve the workability by suppressing an increase in press-fit resistance.
On the other hand, when the steel pipe pile 2 is penetrated into the support layer to stop the steel pipe pile 2, the pipe inner soil S is pushed downward by performing at least one of the second rotational press-fitting process and the reverse rotational process. By promoting the blockage of the pipe soil S, the tip support force can be increased.

In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.
For example, in the previous SL embodiment, by adjusting the a vertically downward displacement D1 of the steel pipe pile 2 and the rotational displacement amount D2, was so pressed the rotation angle θ2 than the inclination angle θ1 of the rib 4 is increased, to Not limited to this, only the vertical downward displacement D1 may be adjusted, or only the rotational displacement amount D2 may be adjusted.

  Further, as a method of adjusting the vertical downward displacement D1 and the rotational displacement amount D2, the method of controlling the vertical downward load Q and the rotational load R applied to the steel pipe pile 2 from the pile driving machine has been described. As shown in FIG. 7, the vertical downward displacement D <b> 1 and the rotational displacement amount D <b> 2 may be adjusted according to the shape of the spiral blade 5 for excavation provided at the tip of the steel pipe pile 2. Specifically, the step size H2 of the spiral blade 5 is made smaller than the step size H1 (per half rotation) of the rib 4 having a predetermined inclination angle θ1 as in the above-described embodiment. The press-fitting rotation angle θ2 associated with the excavation of the spiral blade 5 becomes larger than the inclination angle θ1, and the pile driving machine can perform the first rotary press-fitting step only by applying a rotational force to the steel pipe pile 2.

In addition, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described with particular reference to certain specific embodiments, but without departing from the spirit and scope of the invention, Various modifications can be made by those skilled in the art in terms of material, quantity, and other detailed configurations.
Therefore, the description limiting the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

  DESCRIPTION OF SYMBOLS 1 ... Steel pipe pile foundation, 2 ... Steel pipe pile, 3 ... Inner peripheral surface, 4 ... Rib (protrusion), D1 ... Vertical downward displacement (vertical displacement amount), D2 ... Rotary displacement amount, S ... In-pipe soil, (theta) 1 ... Inclination angle , Θ2, θ2 ′: press-fitting rotation angle (construction angle).

Claims (5)

A steel pipe pile construction method in which a steel pipe pile having a spiral projection on the inner surface is rotationally pressed into the ground,
The rotation direction of the steel pipe pile is set so that the downward inclination angle formed by the spiral projection and the steel pipe shaft and the construction angle formed by the rotational displacement amount and the vertical displacement amount at the time of rotary press-fitting are in the same quadrant. Set,
A steel pipe pile comprising a first rotary press-fitting step of rotary press-fitting while adjusting at least one of a rotational speed and a press-fitting speed of the steel pipe pile so that the construction angle is larger than an inclination angle of the protrusion. Construction method. In the construction method of the steel pipe pile of Claim 1,
Rotational press-fitting while adjusting at least one of the rotational speed and the press-fitting speed at the time of rotational press-fitting so that the construction angle is the same as the inclination angle of the protrusion or the construction angle is smaller than the inclination angle of the protrusion. A steel pipe pile construction method comprising a second rotary press-fitting step. In the construction method of the steel pipe pile according to claim 2,
The steel pipe pile construction method, wherein the second rotary press-fitting step is performed when the tip of the steel pipe pile is penetrated into the support layer. In the construction method of the steel pipe pile in any one of Claims 1-3,
A method for constructing a steel pipe pile, comprising performing a reverse rotation step of reversely rotating the steel pipe pile to compact the soil inside the steel pipe pile when the steel pipe pile is clamped.   A steel pipe pile foundation, wherein a steel pipe pile having a spiral projection on the inner surface is constructed by penetrating into the ground by the steel pipe pile construction method according to any one of claims 1 to 4.

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