JP4789730B2 - Different diameter steel pipe pile - Google Patents

Description

  The present invention relates to a head pile having a large diameter upper portion and a small diameter lower portion in a pile foundation structure, and relates to a different diameter steel pipe pile whose outer diameter changes in the longitudinal direction.

  When constructing a structure on soft ground, a pile foundation is generally employed to support the structure. Pile is designed to support the weight of the structure during normal times. However, since many cases of pile damage have been reported in past earthquake disasters, piles and foundation structures during earthquakes have been reported. Ensuring the seismic performance is pointed out as an important issue in seismic design.

  A general method for improving the seismic performance of piles is to apply horizontal force to the pile material so that it can withstand the earthquake response generated in the pile due to forced deformation caused by horizontal force transmitted by the structure or horizontal displacement of the surrounding stratum. There are ways to increase proof stress. In Japan, a head-expanded pile has been developed and proposed as a method for increasing the horizontal strength of pile materials, and has been put to practical use in field construction piles.

  However, in the field of ready-made piles and steel pipe piles, several examples have come to be proposed as follows, but a method for rationally and economically combining pile materials with different pile diameters up to workability is still established. The current situation is not.

  For example, Japanese Patent Laid-Open No. 2000-73365 (Patent Document 1) is known as a known technique related to a conventional head pile.

  Patent Document 1 relates to a screw-type steel pipe pile having different diameters in which an upper pile material and a lower pile material are connected via a tapered steel pipe.

JP 2000-73365 A

  Patent Document 1 proposes a technique in which an upper pile material and a tapered steel pipe are welded at a factory, and a lower pile material and a tapered steel pipe are welded at a construction site. In order to abut the tapered steel pipe whose end face is inclined to the outer surface of the upper and lower pile members with straight end faces with high accuracy, a special technique is required and it is difficult to weld with high accuracy.

  An object of the present invention is to provide a different diameter steel pipe pile that can construct a head-expanded pile excellent in earthquake resistance by a rational and economical joining method.

The different diameter steel pipe pile of Claim 1 is a different diameter steel pipe pile which connects a large diameter pile material and a smaller diameter pile material, Comprising: The same diameter which can be combined with the said large diameter pile material A first straight pipe portion including a first end portion and a second end portion having the same diameter that can be coupled to the small-diameter pile material, and extending in a longitudinal center direction from each of the first end portion and the second end portion. When the second straight pipe portion is provided to have a reduced diameter portion whose diameter is reduced toward the second straight pipe portion from the first straight pipe portion, the steel pipe thickness of the second end the first end The steel pipe thickness of the reduced diameter portion is continuously changed .

  Thus, by providing straight pipe sections at both ends, it is easy to match the outer surfaces of each other in parallel when joining the upper pile material or the lower pile material and the different diameter steel pipe at the factory or construction site. In addition, the verticality and the displacement of the piles at the time of joining can be suppressed.

Further, by continuously changing the steel pipe thickness so that the steel pipe thickness is substantially inversely proportional to the outer diameter, local stress concentration of the vertical load can be prevented, and the stress can be satisfactorily transmitted from the upper part to the lower part.

Different diameter steel pipe piles according to claim 2, in different diameter steel pipe pile according to claim 1, equal to or greater than the outer diameter outer diameter of the second straight pipe portion of the reduced diameter portion, at not more than the outside diameter of the first straight pipe portion Thus, the reduction ratio is an arbitrary value of 0 or more and 1/10 or less. Thus, by making the diameter-reduced portion flexible, penetration resistance during construction can be reduced, and local stress concentration can be prevented.

  The different diameter steel pipe piles of the present invention are provided with straight pipe portions at both ends, so that when the upper pile material or the lower pile material and the different diameter steel pipes are combined in the factory or construction site, the outer surfaces of the piles are aligned in parallel. It is easy, and it is possible to suppress the verticality and the displacement of the piles when combined.

  In addition, by continuously changing the steel pipe thickness of the reduced diameter portion so as to be approximately inversely proportional to the outer diameter, local stress concentration of the vertical load can be prevented, and stress can be transmitted well from the upper part to the lower part. .

  In addition, by making the reduced diameter portion flexible, penetration resistance during construction can be reduced, and local stress concentration can be prevented.

  Hereinafter, one embodiment of a different diameter steel pipe pile concerning the present invention is described using a figure.

(Overall structure of expanded pile 1)
The structure of the expanded pile 1 using the different diameter steel pipe pile 10 is demonstrated using figures. FIG. 1 is a side view showing a configuration of a head pile 1 using a different diameter steel pipe pile 10, FIG. 2 is an enlarged side view of the different diameter steel pipe pile 10, and FIG. 3 is an enlarged sectional view of the different diameter steel pipe pile 10. It is.

  As shown in FIG. 1, the different diameter steel pipe pile 10 as a part of the expanded head pile 1 has a large-diameter upper pile material 20 arranged on the upper side and a lower-diameter lower pile material 30 arranged on the lower side. ing. The different diameter steel pipe pile 10 is interposed between the upper pile material 20 and the lower pile material 30, and is connected to the upper and lower pile materials by welding or a mechanical joint. The upper and lower pile members 20 and 30 are steel members formed of steel pipes having a predetermined length. The different diameter steel pipe pile 10 is also a steel member equivalent to the upper and lower pile members 20 and 30.

  As shown in FIG. 2, the different diameter steel pipe pile 10 includes a first end portion 11 connected to the upper pile material 20, a first straight pipe portion 12 having the same diameter regardless of the position having the first end portion 11, and It is composed of a reduced diameter portion 13 whose diameter decreases as it goes downward, a second straight pipe portion 14 having the same diameter regardless of position, and a second end portion 15 connected to the lower pile material 30. . The outer diameter D1 of the first end portion 11 is formed to have substantially the same dimension as the outer diameter of the upper pile material 20, and the outer diameter D2 of the second end portion 15 is substantially the same as the outer diameter of the lower pile material 30. It is formed to the dimension.

  As shown in FIG. 3, the steel pipe thickness t <b> 2 of the second end portion 15 is configured to be thicker than the steel pipe thickness t <b> 1 of the first end portion 11. That is, it is formed so as to satisfy the relationship of t2> t1.

  The first straight pipe portion 12 and the second straight pipe portion 14 form straight portions (for example, about 300 mm) in the axial direction from the first end portion 11 and in the axial direction from the second end portion 15. The steel pipe thickness of the straight pipe portion is substantially constant, the steel pipe thickness of the first straight pipe portion 12 is the steel pipe thickness t1, and the steel pipe thickness of the second straight pipe portion 14 is the steel pipe thickness t2.

(Detailed configuration of reduced diameter portion 13)
Next, the configuration of the reduced diameter portion 13 existing between the first straight pipe portion 12 and the second straight pipe portion 14 will be described in detail.

  The diameter-reduced portion 13 has a diameter D1 on the first straight pipe portion 12 side and a diameter D2 on the second straight pipe portion 14 side, and the diameter of the reduced diameter portion 13 decreases from the first straight pipe portion 12 toward the second straight pipe portion 14. To do.

  ((D1-D2) / 2L) shown in FIG. 3 is about 1/10 or less. The steel pipe thickness of the reduced diameter portion 13 is formed so as to continuously change from t1 to t2 so as to be substantially inversely proportional to the outer diameter from the first straight pipe portion 12 toward the second straight pipe portion 14.

(Construction procedure of head-expanded pile 1 using different diameter steel pipe pile 10)
Next, the construction procedure of the head-expansion pile using the different-diameter steel pipe pile 10 configured as described above will be described using the drawings. FIG. 4 is an explanatory view of the construction procedure of the expanded pile using the different diameter steel pipe pile 10.

  First, in a factory or the like, the upper pile member 20 and the first end portion 11 (see FIG. 2) of the different diameter steel pipe pile 10 are joined by welding or a mechanical joint. Next, as shown to Fig.4 (a), a construction machine is used and the lower pile material 30 is embed | buried. The depth at which the lower pile material 30 is buried is until the upper end portion 31 of the lower pile material 30 reaches near the ground surface E as shown in FIG.

  Next, the upper pile material 20 to which the different diameter steel pipe piles 10 are coupled is lifted by a crane or a construction machine. Then, as shown in FIG. 4C, the second end portion 15 of the different diameter steel pipe pile 10 is placed on the upper end portion 31 of the lower pile material 30. And after confirming the installation accuracy of the lower pile material 30 and the upper pile material 20, the upper end part 31 of the lower pile material 30 and the 2nd end part 15 of the different diameter steel pipe pile 10 are couple | bonded by welding or a mechanical coupling.

  After the coupling, as shown in FIG. 4D, the upper pile material 20 is buried to a predetermined depth, and the construction of the head-expanded pile 1 is completed.

[Other Embodiments]
In the above-described embodiment, the reduced diameter portion 13 of the different diameter steel pipe pile 10 is directed from the first straight pipe portion 12 to the second straight pipe portion 14 and has a constant diameter reduction ratio. It is not limited. Different diameter reduction ratios of 0 or more and 1/10 or less may be combined to form a different diameter steel pipe pile having a plurality of reduced diameter portions. A reduced diameter portion that gradually increases or gradually decreases in a range where the diameter reduction rate is 0 or more and 1/10 or less can be obtained. As shown in FIG. 5, the diameter reduction rate can be expressed as (D (z + Δz) −D (z)) / 2Δz, Δz → 0.

  The different diameter steel pipe pile 40 shown in FIG. 6 includes a first straight pipe portion 41, a first reduced diameter portion 42 having a predetermined reduced diameter ratio, and a second reduced diameter that is larger than the first reduced diameter portion 42. A portion 43, a third reduced diameter portion 44 having a smaller diameter reduction ratio than the second reduced diameter portion 43, and a second straight pipe portion 45.

  Moreover, the different diameter steel pipe pile 50 shown in FIG. 7 is comprised so that it may decrease gradually after the diameter reduction rate increases gradually with the 1st straight pipe part 51 and the upper part (with increase of Z). Therefore, compared with the case where the diameter increases linearly (in the case of a broken line (in contact with the first straight pipe portion 51 side)), the reduced diameter portion 52 having a concave shape and the second straight pipe portion 53.

  Further, the different-diameter steel pipe pile 60 shown in FIG. 8 is configured to gradually increase after the diameter reduction rate gradually decreases with the first straight pipe portion 61 and with the upper portion (with increasing Z). Therefore, the diameter-reduced portion 62 has a convex shape compared to the case where the diameter increases linearly (in the case of a broken line (in contact with the second straight pipe portion 63 side)), and the second straight pipe Part 63.

  In the above-described embodiment, an example in which the upper pile material 20 and the different-diameter steel pipe pile 10 are combined at a factory prior to construction is shown, but this may be performed at a construction site. For example, the different-diameter steel pipe pile 10 and the upper pile material 20 may be joined by welding as shown in FIG. 9 (a), or may be joined by a mechanical joint 70 as shown in FIG. 9 (b). Good.

  The present invention relates to a head pile having a large diameter in the upper part and a small diameter in the lower part of the pile foundation structure, and relates to a different diameter steel pipe pile whose outer diameter changes in the longitudinal direction, and is suitable for use in the field of construction and civil engineering.

The side view which shows the structure of the head-expansion pile using a different diameter steel pipe pile. The enlarged side view of the different diameter steel pipe pile 10. FIG. The expanded sectional view of the different diameter steel pipe pile 10. FIG. Explanatory drawing of the construction procedure of the expansion head pile using the different diameter steel pipe pile 10. FIG. Explanatory drawing of a diameter reduction rate. The side view of the different diameter steel pipe pile 40 which concerns on other embodiment. The side view of the different diameter steel pipe pile 50 which concerns on other embodiment. The side view of the different diameter steel pipe pile 60 which concerns on other embodiment. Explanatory drawing of the coupling | bonding method of the different diameter steel pipe pile 10 and the upper pile material 20 which concern on other embodiment.

  E: Ground surface, 1 ... Expanded pile, 10 ... Different diameter steel pipe pile, 11 ... First end, 12 ... First straight pipe part, 13 ... Reduced diameter part, 14 ... Second straight pipe part, 15 ... Second End part, 20 ... Upper pile material, 30 ... Lower pile material, 31 ... Upper end part, 40 ... Different diameter steel pipe pile, 41 ... First straight pipe part, 42 ... First reduced diameter part, 43 ... Second reduced diameter part 44 ... 3rd diameter reduction part, 45 ... 2nd straight pipe part, 50 ... Different diameter steel pipe pile, 51 ... 1st straight pipe part, 52 ... Reduction diameter part, 53 ... 2nd straight pipe part, 60 ... Different diameter Steel pipe pile, 61 ... first straight pipe part, 62 ... reduced diameter part, 63 ... second straight pipe part, 70 ... mechanical joint

Claims (2)

It is a different diameter steel pipe pile that connects a large diameter pile material and a smaller diameter pile material,
A first end of the same diameter that can be coupled to the large-diameter pile material, and a second end of the same diameter that can be coupled to the small-diameter pile material, the first end and the first second end of the provided first straight pipe portion and the second straight pipe portion in the longitudinal central direction is provided from each have a reduced diameter portion whose diameter is reduced toward the second straight pipe portion from the first straight pipe portion The steel pipe thickness of the said 2nd end part is thicker than the steel pipe thickness of the said 1st end part, The steel pipe thickness of the said reduced diameter part changes continuously, The different diameter steel pipe pile characterized by the above-mentioned . The reduced diameter portion has an outer diameter not less than the outer diameter of the second straight pipe portion and not more than the outer diameter of the first straight pipe portion, and the reduced diameter ratio has an arbitrary value of 0 or more and 1/10 or less. different diameter steel pipe pile according to claim 1, wherein the.