JP4961448B2 - Tip member of foundation pile and foundation pile using the same - Google Patents

Description

  The present invention relates to a tip member of a foundation pile that is press-fitted into the ground while rotating, and a foundation pile using the same.

  Many foundation piles that are press-fitted into the ground while rotating are made by welding various shapes of blades such as a spiral to the tip of a cylindrical steel pipe. In order to manufacture this type of foundation pile, it is necessary to have press equipment and molds for manufacturing the blades, and the welded part between the blades and the steel pipe has a more complicated shape than the welded part between the steel pipes. For this reason, a considerable amount of labor and cost are required, such as requiring a skilled welding technique to ensure sufficient welding strength between the blade and the steel pipe. In addition, since a large force acts on the welded portion between the blade and the steel pipe when the foundation pile is pressed or removed, there is a problem that the blade is detached from the welded portion depending on the welding condition and the hardness of the ground.

For this reason, a basic pile in which a cylindrical straight pipe portion and a blade at the tip of the straight pipe portion are integrally formed by centrifugal casting, a casting mold and a manufacturing method of this pile have been proposed (for example, Patent Document 1). reference).
According to the invention of Patent Document 1, since the straight pipe portion of the foundation pile and the blade are integrally formed by casting, there are press equipment for manufacturing the blade and skilled welding technology for attaching the blade. This eliminates the need for a highly stable foundation pile. However, in the case where the straight pipe portion and the blade at the tip of the straight pipe portion are formed integrally by centrifugal casting as described above, a large centrifugal casting facility is required and the cast foundation pile There is a problem in that productivity is poor because it takes a corresponding cooling time until the mold can be removed without deformation.

Japanese Patent No. 3414629

  The problem to be solved by the present invention is that, in the tip member of the foundation pile that is press-fitted into the ground while rotating, the foundation pile body that is a steel pipe can be easily welded, and tension, compression, shearing, bending, twisting, etc. It works without any problems against the mechanical factors that occur when press-fitting or withdrawing foundation piles and when supporting superstructures as piles, and can reliably transmit the power of construction machinery, An object of the present invention is to provide a tip member of a foundation pile that can be surely exhibited and improved productivity, and a foundation pile using the same.

In order to achieve the above object, the invention according to claim 1 is a tip member of a foundation pile that is press-fitted into the ground while rotating, and a substantially cylindrical tip body that is a cast product having blades at the tip. The steel pipe having a substantially cylindrical shape and good weldability is characterized in that the pipe is cast into the tip portion main body and protrudes from the rear end of the tip portion main body.
According to a second aspect of the present invention, in the tip member of the foundation pile according to the first aspect, the connecting pipe has a concavo-convex shape in which a plurality of notches are continuously arranged in the circumferential direction on the tip side end face, One or a plurality of circumferential grooves continuous in the circumferential direction are provided on the surface, and the notch and the circumferential groove are cast into the tip body.

  Moreover, in invention of Claim 3, it is a foundation pile using the front-end | tip member of Claim 1 or 2, Comprising: The said pipe and the substantially cylindrical foundation pile main body were welded and joined. And

  According to the tip member of the foundation pile of the invention of claim 1, since the blade is integrally formed by casting on the tip body, it acts when the foundation pile is press-fitted or removed and when the upper structure is supported as a pile. The blade does not come off due to the force of Moreover, since the steel joint pipe with good weldability protrudes from the rear end of the tip portion main body, it can be easily joined to the foundation pile main body, which is a substantially cylindrical steel pipe, by welding.

  According to the tip member of the foundation pile of the invention of claim 2, when the tip body as a cast product and the steel joint with good weldability are integrally formed by casting, As the molten metal enters the notch portion of the end surface on the front end side and solidifies, the connecting pipe and the main body of the front end portion are firmly engaged and fixed in the circumferential direction. Therefore, after welding the joint pipe to the foundation pile body, when rotating the tip member together with the foundation pile body, the torque applied to the foundation pile body is distributed and received by the notches, so it has high strength against torque. Demonstrate. Similarly, the molten metal enters and solidifies in the circumferential groove on the peripheral surface of the joint pipe, so that the joint pipe and the tip body are firmly engaged and fixed in the axial direction. Since the tensile or compressive load applied in the axial direction of the foundation pile main body is received by one or a plurality of circumferential grooves, it has high strength against tensile and compressive loads. On the other hand, after welding the joint pipe to the foundation pile body, if a bending load is applied to the foundation pile and the joint between the joint pipe and the tip body warps, the circumferential groove will be caught and the tip body will come off. prevent.

  According to the foundation pile of the invention of claim 3, by adopting a configuration in which the joint pipe and the foundation pile body are welded, the tip member composed of the tip part body and the joint pipe and the foundation pile body that is a steel pipe are separately provided. Can be made into an integral foundation pile. Therefore, the manufacturing facility can be reduced to a small scale, and for example, a general small-scale facility such as a sand casting method can be used.

It is the schematic of the front-end | tip member of the foundation pile which concerns on this invention. It is the schematic of a connecting pipe. It is the schematic of a front-end | tip part main body. It is the schematic which shows the state by which the connecting pipe was cast by the front-end | tip part main body. It is an end view of the tip member concerning the present invention. It is the schematic of the foundation pile which concerns on this invention.

FIG. 1 is a schematic view of a tip member of a foundation pile according to the present invention.
As shown in the drawing, the tip member 1 includes a connecting pipe 2 and a tip portion main body 3. A blade 4 is integrally formed at the tip of the tip body 3. The connecting pipe 2 has a shape in which only the rear end (upper end) portion protrudes, and the lower portion, that is, the tip end portion of the connecting pipe 2 is cast into the tip end body 3. Since it is cast, the connecting pipe 2 and the tip body 3 are in close contact with each other without any gap, but are not welded.

  The connecting pipe 2 is made of steel having good weldability such as low carbon steel, and the tip body 3 has an elongation standard value of 10% or more and a carbon equivalent of 2.14% to 4.50%. -Cast products made of carbon alloys. Here, the standard value of elongation is set to 10% or more when the tip body 3 is pressed when seismic force or the like is applied at the time of press-fitting or removing the foundation pile and supporting the upper structure. In order to prevent brittle fracture, the carbon equivalent is in the range of 2.14% or more and 4.50% or less, thereby improving the fluidity of the molten metal and making complex shapes possible. This is because the casting can be performed at a low temperature and advantages such as low manufacturing costs can be obtained. When the carbon equivalent is less than 2.14%, the fluidity of the molten metal is deteriorated and casting defects are likely to occur. Therefore, it is necessary to increase the melting temperature and the casting temperature, and the production cost is increased. When the carbon equivalent exceeds 4.50%, there is a concern that the mechanical properties are deteriorated due to abnormal graphite. The tip body 3 is poor in weldability because of its high carbon content. However, since the steel connecting pipe 2 having good weldability protrudes from the rear end of the tip body 3, a substantially cylindrical steel pipe is provided. Can be easily joined to the foundation pile main body 11 (see FIG. 6) by welding. Therefore, the weldability with the foundation pile main body 11 is improved and the handleability is improved while securing the strength for the underground press-fitting.

FIG. 2 is a schematic view of the connecting pipe.
As described above, the connecting pipe 2 is made of steel having good weldability such as low carbon steel, and has a short, substantially cylindrical shape. A plurality of notches 6 are provided on the end face on the distal end side of the connecting pipe 2. Accordingly, the end surface on the distal end side of the connecting pipe 2 is formed with an uneven shape that is continuous in the circumferential direction. A plurality of circumferential grooves 5 are provided on the outer peripheral surface, which is the side surface of the connecting pipe 2, in the circumferential direction over the entire circumference (three circumferential grooves 5 in the figure). In addition, if the connection pipe 2 is a material with favorable weldability with the foundation pile main body 11 and sufficient intensity | strength, it will not be limited to low carbon steel.

FIG. 3 is a schematic view of the tip body.
As described above, the tip body 3 includes the blade 4 at the tip. Note that in FIG. 3, the rear end of the tip end body 3 is a double pipe because the connection pipe 2 is removed in order to describe the joint pipe 2 and the tip end body 3 separately. Although it has a structure, the actual tip portion main body 3 is a cast product formed by casting the connecting pipe 2, and the tip portion main body 3 having a double pipe structure does not exist alone. In order to improve the penetration of the foundation pile, an inclination 9 of about 45 ° is provided at the terminal end (the most advanced) of the blade 4.

FIG. 4 is a schematic view showing a state in which the connecting pipe is cast in the tip body, and FIG. 5 is an end view of the tip member according to the present invention.
The notch 6 will be described.
Over the entire circumference of the end surface on the distal end side of the connecting pipe 2, a plurality of notch portions 6 with the widths of the convex portions and the concave portions set appropriately according to the differences in the allowable stresses of the connecting pipe 2 and the distal end portion main body 3 are evenly distributed. It is provided, and the durability generated by increasing the torque generated when the foundation pile is press-fitted or withdrawn by each notch 6 is increased. If the number of notches (the number of notches 6) is small, the stress acting on the side wall surface of each notch 6 will increase, and the meshing portion of either the connecting pipe 2 or the tip body 3 will be deformed or broken. Resulting in.

  The side wall surface of the notch 6 has a C-shape in plan view along a straight line extending radially from the center of the connecting pipe to the outer peripheral side. When the side wall surface of the notch 6 is parallel, torque concentrates on the outer peripheral side and is easily deformed. That is, by making the side wall surface of the notch portion 6 into a C shape in a plan view, the torque at the time of press-fitting or withdrawing is uniformly received over the entire side wall surface, thereby improving the durability.

  The number of notches 6, the height of the notches, and the widths of the protrusions and the recesses are the bearing pressure applied to the side wall surface of the notches 6 and the shear force applied to the root surface of the protrusions 7 sandwiched between the notches 6. And shearing force applied to the tip body 3 side that meshes with the notch 6 (the surface formed by the tip body 3 among the six surfaces surrounding the notch 6 (the inner surface of the notch 6, the outer surface The allowable stress for each of the shearing force) on the side surface and the tip surface) is set to be larger than the stress generated at the yield torsional moment of the foundation pile body 11 (see FIG. 6).

When the above conditions are satisfied, the number of cutouts is as small as possible and the cutout height is set low, so that the cast-in depth can be reduced and the product weight can be reduced.
The circumferential groove 5 will be described.
In the present embodiment, three circumferential grooves 5 are provided along the circumferential direction of the outer peripheral surface of the connecting pipe 2 and are added when the foundation pile is pressed or removed and when the upper structure is supported. Durability is increased by receiving axial support pressure in a distributed manner. The depth of the circumferential groove 5 depends on the allowable tensile force of the remaining thick portion of the circumferential groove 5 (the thick portion of the connecting pipe 2 where the circumferential groove 5 is formed), and the allowable bearing pressure in the circumferential groove portion (circumferential groove). 5 is larger than the allowable tensile force of the foundation pile body 11, and the total plastic moment of the remaining thick portion of the circumferential groove 5 is the total plasticity of the foundation pile body 11. The yield torsion moment in the remaining thick portion of the circumferential groove 5 is set so as to be greater than the yield torsion moment of the foundation pile body 11.

The depth of the circumferential groove 5 is determined by the allowable shear force on the distal end body 3 side in the circumferential groove 5 (the allowable shear force of the root surface of the distal end body 3 entering the circumferential groove 5). It is set to be larger.
The distance between each circumferential groove 5 is that the allowable shearing force of the connecting pipe 2 between the circumferential grooves 5 (the allowable shearing force of the root surface of the protrusion 8 sandwiched between the circumferential grooves 5) is larger than the allowable tensile force of the foundation pile body 11. Set to be larger.

Since the depth of the circumferential groove 5 and the distance between the circumferential grooves 5 influence each other, they are set to be appropriately balanced.
The blade 4 will be described.
The tip portion main body 3 is cut out in a spiral shape over the entire circumference of the tip. An outer blade portion 4a that protrudes outside the cylindrical portion of the tip portion main body 3 and an inner blade portion 4b that protrudes inward extend in a ring shape along the notch surface, and are formed as a spiral blade 4. . Since the inner blade portion 4b projects inside the tip portion main body 3, the large bending moment acting on the base of the blade 4 and the foundation pile main body portion in the vicinity thereof is reduced, and deformation to the inner side of the foundation pile is prevented. Yes.

The width of the outer blade portion 4a is about 0.5 to 0.75 times the outer diameter of the foundation pile body 11. The width of the inner blade portion 4 b is approximately 0.25 times the outer diameter of the foundation pile body 11.
Here, the blade 4 of the present embodiment has a spiral structure that extends along the tip of the tip body 3 that is spirally cut out over substantially one round, but is not limited thereto. For example, the tip of the main body of the tip is cut into a discontinuous spiral shape or a larger number of sawtooth shapes every half circumference, and a plurality of semicircular or fan-shaped blades are formed along the tip. Also good.

  In addition, the plate | board thickness of the front-end | tip part main body 3 in the circumference | surroundings of the joint pipe 2 is the allowable tensile force of the front-end | tip part main body 3 about the inner periphery side of the joint pipe 2, the outer peripheral side, and the lower surface side, respectively. The total plastic moment of the tip body 3 is larger than the total plastic moment of the foundation pile body 11, and the yield torsion moment of the tip body 3 is set to be greater than the yield torsion moment of the foundation pile body 11.

  With the above configuration, since the joint pipe 2 is cast with the tip body 3, the molten metal enters the notch portion 6 of the joint pipe 2 and solidifies, so that the joint pipe 2 and the tip body 3 are firmly toothed. And fixed in the circumferential direction. Therefore, after welding the connecting pipe 2 to the foundation pile body 11, the torque applied to the foundation pile body 11 when the tip member 1 is rotated together with the foundation pile body 11 is dispersed and received by the plurality of notch portions 6. High strength is demonstrated. Similarly, when the molten metal enters and solidifies in the circumferential groove 5 on the peripheral surface of the joint pipe 2, the joint pipe 2 and the tip body 3 are firmly engaged and fixed in the axial direction. Since tensile and compressive loads applied in the axial direction of the foundation pile main body 11 are distributed and received by the plurality of circumferential grooves 5, it has high strength against tensile and compressive loads. On the other hand, after welding the joint pipe 2 to the foundation pile main body 11, when a bending load is applied to the foundation pile and the joint portion between the joint pipe 2 and the tip main body 3 warps, the circumferential groove 5 is caught and the tip main body 3 Prevents from falling out.

FIG. 6 is a schematic view of a foundation pile according to the present invention.
As illustrated, the foundation pile 10 is formed by welding the connecting pipe 2 of the tip member 1 and the foundation pile body 11 by welding. The foundation pile main body 11 is a carbon steel pipe for general structure, and when the pile length is insufficient, a steel pipe made of the same material can be added to the upper end surface by welding or the like. By setting it as the structure which welds such a connecting pipe 2 and the foundation pile main body 11, the front-end | tip member 1 and the foundation pile main body 11 can be manufactured separately, and it can be set as an integral foundation pile. Therefore, the manufacturing facility can be reduced to a small scale, and for example, a general small-scale facility such as a sand casting method can be used. Moreover, since the connection pipe 2 is made of steel having good weldability such as low carbon steel as described above, it can be easily welded to the foundation pile main body 11.

DESCRIPTION OF SYMBOLS 1 Tip member 2 Connecting pipe 3 Tip part main body 4 Blade | blade 4a Outer blade | wing part 4b Inner blade | wing part 5 Circumferential groove 6 Notch part 7 Protrusion part pinched by the notch part 8 Protrusion part 9 pinched by the peripheral groove Inclination 10 Foundation Pile 11 Foundation pile body

Claims (3)

A tip member of a foundation pile that is pressed into the ground while rotating,
A substantially cylindrical tip body, which is a cast product with blades at the tip;
It consists of a steel pipe with a substantially cylindrical shape and good weldability.
The connecting pipe is cast into the tip portion main body and protrudes from the rear end of the tip portion main body. The connecting pipe is provided with a concavo-convex shape in which a plurality of notches are continuously arranged in the circumferential direction on the end surface on the front end side, and has one or more circumferential grooves continuous in the circumferential direction on the circumferential surface,
The tip member of a foundation pile according to claim 1, wherein the notch and the circumferential groove are cast into the tip body. A foundation pile using the tip member according to claim 1 or 2,
The foundation pile which welded and joined the said connecting pipe and the substantially cylindrical foundation pile main body.

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