Pile head caps and building foundations

Abstract

To provide a pile head cap and a building foundation which facilitate fitting the pile head cap to a pile head of a steel pipe pile even when the pile head of the steel pipe pile is somewhat deformed.SOLUTION: A pile head cap 1 comprises an iron plate portion 11, a plurality of protrusions 12 protruding downward from a lower surface side of the iron plate portion 11 in a state of covering a pile head 51 of a steel pipe pile 5 and facing the inner peripheral surface of an upper edge side of the pile head 51. Horizontal width of a tip portion 12a of the protrusion 12 in the state of covering the pile head 51 is narrower than horizontal width of a non-tip portion 12b of the protrusion 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a pile head cap attached to the pile head of a steel pipe pile driven into the ground and a building foundation using this pile head cap.

Background Art

[0002] Conventionally, in order to prevent differential settlement of buildings on soft ground, a pile ground reinforcement method of driving cylindrical steel pipe piles into the ground has been performed. In this pile ground reinforcement method, after driving the steel pipe piles, a work of attaching a pile head cap to the pile head of the steel pipe pile by welding and then backfilling is performed. Thereafter, the foundation contractor excavates the soil at the backfilled location and performs foundation work.

[0003] On the other hand, Patent Document 1 discloses a pile head cap that can be used simply by covering the pile head of a steel pipe pile and can eliminate the need for operations such as welding a steel plate to the pile head at the site.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, as shown in Fig. 3(B), in the case where a deformed portion 501a has occurred on the pile head 501 of the steel pipe pile, in the operation of covering the pile head cap on the pile head 501, the protruding portion 120 of the pile head cap hits the deformed portion 501a of the pile head 501, and it may take time to fit the pile head cap onto the pile head 501.

[0006] In view of the above circumstances, an object of this invention is to provide a pile head cap and a building foundation that facilitate fitting the pile head cap onto the pile head of a steel pipe pile even when there is some deformation in the pile head of the steel pipe pile. [Means for solving the problem]

[0007] The pile head cap of this invention, in order to solve the above problems, comprises a plate-shaped portion and a projection that protrudes downward from the lower surface of the plate-shaped portion when placed over the pile head of a steel pipe pile and faces the inner circumferential surface on the upper edge side of the pile head, characterized in that the horizontal width of the tip of the projection when placed over the pile head is narrower than the horizontal width of the non-tip portion of the projection.

[0008] With the above configuration, the horizontal width of the tip of the protruding portion when it is placed over the pile head is narrower than the horizontal width of the non-tip portion of the protruding portion, thus reducing the rate at which the protruding portion comes into contact with any deformation in the pile head. As a result, even if there is some deformation in the pile head of the steel pipe pile, it becomes easier to fit the pile head cap onto the pile head, improving the efficiency of the pile head cap fitting process.

[0009] With the pile head cap placed over the pile head, the tip of the protruding portion may make line contact with the inner circumferential surface along a single vertical line. This reduces the rate at which the protruding portion contacts the deformed portion of the pile head compared to when the tip portion faces the inner circumferential surface across a surface.

[0010] The horizontal cross-sectional shape of the tip of the protruding portion when the pile head cap is placed over the pile head may be arc-shaped. This makes it less likely for chipping or other damage to occur at the tip compared to when the cross-sectional shape of the tip is triangular.

[0011] The lower part of the protruding portion may have an inclined lower surface that slopes downward toward the center of the steel pipe pile when the pile head cap is placed over the pile head. This allows the inclined lower surface to act as a starting point for fitting the pile head cap onto the pile head, even if there is some deformation in the pile head of the steel pipe pile, thereby improving the workability of fitting the pile head cap. Even when the pile head cap is hammered onto the pile head, the presence of this starting point makes it easier to fit.

[0012] The horizontal width of the inclined lower surface when the pile head cap is placed over the pile head may be narrower than the horizontal width of the non-tip portion. This reduces the rate at which the inclined lower surface comes into contact with the deformed portion of the pile head when it initiates the insertion of the pile head cap, thereby improving the workability of inserting the pile head cap.

[0013] The horizontal cross-sectional shape of the inclined underside when the pile head cap is placed over the pile head may be arc-shaped. This makes it less likely for chipping or other damage to occur on the inclined underside compared to, for example, when the cross-sectional shape of the inclined underside is triangular.

[0014] In these pile head caps, When the pile head cap tilts from a state in which the tip of a portion of the above-mentioned protrusion is in contact with the inner circumferential surface of the upper edge of the pile head, with the point where the plate-shaped portion contacts the upper end surface of the pile head as the pivot point, The lower end portion of the tip of the protruding part located below the plate-shaped portion that rises in this incline, the portion closest to the inner circumferential surface in a vertical plane parallel to the vertical plane passing through the fulcrum and the center of the pile head cap, may come into contact with the inner circumferential surface before it reaches the uppermost position on the upper edge side of the pile head in the incline.

[0015] Here, as described above, if the horizontal width of the tip of the protruding portion when it is placed over the pile head is narrower than the horizontal width of the non-tip portion of the protruding portion, the pile head cap will be more likely to come off the pile head when the pile head cap tilts from a state where some of the tip portions of the protruding portion are in contact with the inner circumferential surface on the upper edge side of the pile head. If the lower end portion of the part closest to the inner circumferential surface comes into contact with the inner circumferential surface before the tilt reaches the uppermost position on the upper edge side of the pile head, it is possible to prevent the cap from coming off.

[0016] Moreover, the building foundation of this invention is a building foundation comprising steel pipe piles and a foundation, characterized in that the footing portion of the foundation is located directly on any one of the pile caps provided on the pile heads or via disposable concrete.

Advantages of the Invention

[0017] In the present invention, even when there is some deformation in the pile head of the steel pipe pile, it is easy to fit the pile cap onto the pile head of the steel pipe pile, which has the effect described above.

Brief Description of the Drawings

[0018] [Figure 1] It is a perspective view showing the pile cap and the steel pipe pile according to an embodiment of the present invention. [Figure 2] Figure (A) of this figure is a perspective view of the pile cap of Figure 1 seen from above, and Figure (B) of this figure is a perspective view of the pile cap of Figure 1 seen from the lower surface side. [Figure 3] Figure (A) of this figure is an explanatory plan view showing the tip portion of the protruding portion of the pile cap of Figure 1 and the deformed portion of the pile head, and Figure (B) of this figure is an explanatory plan view showing the protruding portion without a tip portion and the deformed portion of the pile head for comparison. [Figure 4] It is an explanatory side view showing the tip portion of the protruding portion of the pile cap of Figure 1, the inclined lower surface, and the upper end of the pile head. [Figure 5] It is an explanatory view of the pile cap of Figure 1 when tilted on the pile head. [Figure 6] It is an explanatory view showing the building foundation according to an embodiment of the present invention. [Figure 7] It is a plan view of the building foundation of Figure 4. [Figure 8] It is a perspective view showing the pile cap and the steel pipe pile according to another embodiment of the present invention. [Figure 9] It is a perspective view of the pile cap of Figure 8 seen from below. [Figure 10] Figure (A) of this figure is a perspective view of the state where the pile cap of Figure 8 is attached to the steel pipe pile, and Figure (B) of this figure is the same perspective side view.

Mode for Carrying Out the Invention

[0019] (Embodiment 1) Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. As shown in FIGS. 1, 2(A) and 2(B), the pile head cap 1 according to this embodiment includes, for example, a circular iron plate portion 11 having a flat upper surface which is a plate-like portion, and a protruding portion 12 protruding downward from the lower surface side of the iron plate portion 11, and is attached to the pile head 51 so as to close the upper end opening of the cylindrical steel pipe pile 5 embedded in the ground. This pile head cap 1 is, for example, manufactured by casting.

[0020] The iron plate portion 11 has an outer dimension (for example, diameter) larger than the outer dimension (for example, outer diameter) of the steel pipe pile 5. Further, a circular thin-walled region 11a is formed at a location on the lower surface (bottom surface) of the iron plate portion 11 that is not easily affected by the load, so as to achieve weight reduction. Further, a positioning concave portion 11b is formed at the center position of the upper surface (surface) of the iron plate portion 11. The concave portion 11b has, for example, an inverted conical shape.

[0021] Further, the protruding portion 12 is located inside the pipe of the pile head 51 in a state of covering the pile head 51 of the steel pipe pile 5 and faces the inner peripheral surface on the upper end side of the pile head 51. In this embodiment, four protruding portions 12 are arranged at intervals of 90 degrees in the circumferential direction around the center of the circular iron plate portion 11, outside the thin-walled region 11a. Further, a rib portion 13 connected to the protruding portion 12 is provided on the lower surface of the iron plate portion 11 to improve the rigidity and strength of the iron plate portion 11. The rib portion 13 has a height lower than that of the protruding portion 12 and is formed so as to pass through the thin-walled region 11a. Although the amount of the material for manufacturing the pile head cap 1 increases, the height of the rib portion 13 may be made the same as that of the protruding portion 12, or the shape may be such that the thin-walled region 11a is not formed.

[0022] Furthermore, the rib portion 13 connects two opposing protrusions 12 and is formed in a cross shape passing through the center of the iron plate portion 11. Of course, the number of protrusions 12 is not limited to four; three may be arranged at 120-degree intervals in the circumferential direction to form the rib portion 13 in a three-pronged shape, or two may be arranged at 180-degree intervals in the circumferential direction to form the rib portion 13 in a straight line. Alternatively, the number of protrusions 12 may be five or more.

[0023] When the pile head cap 1 is placed over the pile head 51 of the steel pipe pile 5, the horizontal width W1 of the tip portion 12a of the protruding portion 12 is narrower than the horizontal width W2 of the non-tip portion 12b of the protruding portion 12, as shown in Figure 3(A). In this form where the horizontal width W1 is narrowest, the tip portion 12a of the protruding portion 12 can make line contact with the inner circumferential surface with a single vertical line. The horizontal cross-sectional shape of the tip portion 12a that makes this line contact can be a sharp triangular shape, etc. In this embodiment, the horizontal cross-sectional shape of the tip portion 12a of the protruding portion 12 when the pile head cap 1 is placed over the pile head 51 is an arc shape. The curvature of this arc is smaller than the radius of curvature of the inner circumferential surface of the pile head 51.

[0024] Furthermore, as shown in Figure 4, the pile head cap 1 has an inclined lower surface 12c at the lower side of the tip portion 12a of the protruding portion 12, which slopes downward in a straight line or concave curve toward the center of the steel pipe pile 5 when the pile head cap 1 is placed over the pile head 51. The horizontal width W3 of this inclined lower surface 12c is narrower than the horizontal width W2 of the non-tip portion 12b. The horizontal width W3 is, for example, equal to the horizontal width W1. In this embodiment, when the pile head cap is placed over the pile head 51, the horizontal cross-sectional shape of the inclined lower surface 12c is arc-shaped.

[0025] With the pile head cap 1 configured as described above, it can be attached to the pile head 51 of the steel pipe pile 5 simply by placing the pile head cap 1 over it from above, thus eliminating the need for welding work on site. Furthermore, even if an upward lifting force acts on the steel plate portion 11 and the pile head cap 1 detaches from the pile head 51, since it is not welded, it can be reattached simply by placing the pile head cap 1 over the pile head 51 from above. On the other hand, when a lateral force is applied to the steel plate portion 11, the protruding portion 12 contacts the upper edge surface of the pile head 51, making it difficult for the pile head cap 1 to detach from the pile head 51 and also making it difficult for it to shift position.

[0026] Furthermore, the horizontal width W1 of the tip portion 12a of the projection 12 facing the inner circumferential surface is narrower than the horizontal width W2 of the non-tip portion 12b of the projection 12. As shown in Figure 3(A), the rate at which the projection 12 comes into contact with the deformed portion 51a of the pile head 51 of the steel pipe pile 5 is reduced. This makes it easier to fit the pile head cap 1 onto the pile head 51 even if there is some deformation in the pile head 51 of the steel pipe pile 5, improving the efficiency of the pile head cap fitting work.

[0027] When the pile head cap 1 is placed over the pile head 51, if the tip portion 12a of the protrusion 12 makes line contact with the inner circumferential surface along a single vertical line, the rate at which the protrusion 12 contacts the deformed portion 51a of the pile head 51 is reduced compared to when the tip portion 12a faces the inner circumferential surface across a surface.

[0028] When the pile head cap 1 is placed over the pile head 51, if the horizontal cross-sectional shape of the tip portion 12a of the protruding portion 12 is arc-shaped, chipping or other damage to the tip portion 12a is less likely to occur compared to when the cross-sectional shape of the tip portion 12a is triangular.

[0029] If the pile head cap 1 has an inclined lower surface 12c on the lower side of the tip portion 12a of the protruding portion 12 that slopes downward toward the center of the steel pipe pile 5 when the pile head cap 1 is placed over the pile head 51, then even if there is some deformation in the pile head 51 of the steel pipe pile 5, the inclined lower surface 12c will act as a starting point for fitting the pile head cap 1 onto the pile head 51, improving the workability of fitting the pile head cap 1.

[0030] When the pile head cap 1 is placed over the pile head 51, if the horizontal width W3 of the inclined lower surface 12c is narrower than the horizontal width W2 of the part above the inclined lower surface 12c, the rate at which the inclined lower surface 12c comes into contact with the deformed area 51a of the pile head 51 when the inclined lower surface 12c creates a starting point for fitting the pile head cap 1 is reduced, thereby improving the workability of fitting the pile head cap 1.

[0031] When the pile head cap 1 is placed over the pile head 51, if the horizontal cross-sectional shape of the inclined lower surface 12c is arc-shaped, chipping or other damage to the inclined lower surface 12c is less likely to occur compared to when the cross-sectional shape of the inclined lower surface 12c is triangular.

[0032] Here, if the height (length) of the protrusion 12 and the gap between the protrusion 12 and the inner surface of the pile head 51 are set so that when a force is applied to the outer edge of the steel plate portion 11 in an oblique upward direction, causing the steel plate portion 11 to tilt, the lower end of the protrusion 12 contacts the upper edge surface of the pile head 51, then the pile head cap 1 will be less likely to come off the pile head 51 due to forces in directions other than directly upward.

[0033] However, as described above, the horizontal width W1 of the tip portion 12a of the projection 12 facing the inner circumferential surface is narrower than the horizontal width W2 of the non-tip portion 12b of the projection 12. Therefore, depending on the inclination conditions, the pile head cap 1 may easily detach from the pile head 51. For this reason, the height of the projection 12 is increased to make it more difficult for the steel plate portion 11 to detach from the pile head 51.

[0034] For example, as shown in Figure 5, in the pile head cap 1, when the tip portions 12a of some (two adjacent) protrusions 12 are in contact with the inner circumferential surface on the upper edge side of the pile head 51 (let's call this contact point Y), and the steel plate portion 11 tilts with the point where it hits the upper end surface of the pile head 51 as the pivot point, the pile head cap 1 is most likely to come off the pile head 51.

[0035] Therefore, the lower end portion P of the tip portion 12a of the other protruding portion 12 located below the portion of the steel plate 11 that rises due to the above-mentioned inclination, at the point closest to the inner circumferential surface in a vertical plane parallel to the vertical plane S passing through the fulcrum and the center of the pile head cap 1, is brought into contact with the inner circumferential surface before the inclination reaches the uppermost position on the upper edge side of the pile head 51, thereby preventing the pile head cap 1 from coming off.

[0036] In this embodiment, the steel pipe interference position I is defined as the position where a vertical plane parallel to the vertical plane S and passing through the lower end position P touches the inner circumferential surface of the pile head 51. The horizontal distance between IY in the vertical plane parallel to the vertical plane S and passing through the steel pipe interference position I and the contact point Y is defined as C. The distance between the lower end position P and the contact point Y is defined as B > C. In this embodiment, the condition for preventing the pile head cap 1 from coming off due to the inclination is defined as B > C.

[0037] Figures 6 and 7 show the building foundation 100 of this embodiment using the pile head cap 1. In this building foundation 100, the pile head 51 of the steel pipe pile 5 is located in a place excavated below ground level GL, and the pile head cap 1 is attached to this pile head 51. The footing portion 61 of the strip foundation 6 is then supported by the pile head cap 1 via lean concrete 62. Alternatively, the footing portion 61 of the strip foundation 6 may be directly supported on the pile head cap 1 without the use of lean concrete 62. Note that this is not limited to a strip foundation; a raft foundation may also be used.

[0038] (Embodiment 2) Next, other embodiments of this invention will be described based on the accompanying drawings. As shown in Figures 8, 9, 10(A), and 10(B), the pile head cap 2 according to this embodiment comprises a circular steel plate portion (plate-shaped portion) 21 having an outer dimension larger than the outer dimension of the steel pipe pile 5, a projection 22 that protrudes downward from the lower surface of the steel plate portion 21 and faces the inner circumferential surface on the upper edge side of the pile head 51 when it is placed over the pile head 51 of the steel pipe pile 5, and a ring-shaped portion 23 that faces the outer circumferential surface. In addition, a positioning recess 21a is formed at the center of the upper surface of the steel plate portion 21.

[0039] There are four of the above-mentioned protrusions 22, which are scattered at 90-degree intervals in the circumferential direction with respect to the center of the circular steel plate portion 21. On the other hand, the above-mentioned ring-shaped portion 23 is formed in a continuous wall-like manner. The distance between the above-mentioned protrusions 22 and the above-mentioned ring-shaped portion 23 is made wider than the thickness of the pile head 51. However, by making the distance between the above-mentioned protrusions 22 and the ring-shaped portion 23 as narrow as possible, and by making the protruding lengths of the above-mentioned protrusions 22 and the ring-shaped portion 23 longer, when the steel plate portion 21 is tilted, the lower ends of the above-mentioned protrusions 22 and the ring-shaped portion 23 will come into contact with the upper edge circumferential surface of the pile head 51, making it difficult for the pile head cap 2 to come off the pile head 51.

[0040] Furthermore, in this embodiment of the pile head cap 2, similar to the pile head cap 1, the horizontal width of the tip portion 22a of the projection 22 facing the inner circumferential surface of the pile head 51 when the pile head cap 2 is placed over the pile head 51 of the steel pipe pile 5 is narrower than the horizontal width of the non-tip portion 22b of the projection 22.

[0041] Furthermore, the outer shape (for example, the outer diameter) of the ring-shaped portion 23 is not the same at the top and bottom, but has a slanted shape that becomes smaller towards the bottom. In other words, the outer surface 23a of the ring-shaped portion 23 is not vertical, but is inclined so that it approaches the center of the iron plate portion 21 towards the bottom.

[0042] With the above configuration, since the ring-shaped portion 23 is formed in a wall-like shape, even without the rib portion connecting the protruding portion 22, the strength of the pile head cap 2 is improved, cracking and damage can be reduced, the rigidity of the pile head cap 2 is also improved, deformation of the pile head cap 2 becomes less likely, and the building load can be transmitted to the steel pipe pile 5 in a nearly uniform manner.

[0043] Furthermore, if the outer shape of the ring-shaped portion 23 is oblique, becoming smaller towards the bottom, then when the pile head cap 2 is placed over the pile head 51 of the steel pipe pile 5, the outer surface 23a of the ring-shaped portion 23 will be closer to the outer surface of the steel pipe pile 5 towards the bottom. This minimizes the amount of horizontal protrusion from the outer surface of the steel pipe pile 5 at the lower end surface of the ring-shaped portion 23, thereby preventing the claws of the heavy machinery bucket from getting caught on the pile head cap 2 when excavating the soil around the steel pipe pile 5.

[0044] Furthermore, since the horizontal width of the tip portion 22a of the projection 22 facing the inner circumferential surface of the pile head 51 is narrower than the horizontal width of the non-tip portion 22b of the projection 22, the rate at which the projection 22 comes into contact with the deformed portion of the pile head 51 of the steel pipe pile 5 is reduced. As a result, even if there is some deformation in the pile head 51 of the steel pipe pile 5, it becomes easier to fit the pile head cap 2 onto the pile head 51, improving work efficiency. In addition, since the pile head cap 2 has a ring-shaped portion 23, the pile head cap 2 does not come off easily even if the height of the projection 22 is not made too high.

[0045] In this embodiment, the tip portion 22a of the pile head cap 2 does not have the inclined lower surface 12c that the pile head cap 1 of the previous embodiment has, but it may have an inclined lower surface similar to that of the pile head cap 1.

[0046] Although embodiments of this invention have been described above with reference to the drawings, this invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiments within the same scope as this invention, or within the equivalent scope. [Explanation of Symbols]

[0047] 1: Pile head cap 2: Pile head cap 5: Steel pipe pile 6: Strip foundation 11: Iron plate section (plate-shaped section) 11a: Thin area 11b: recess 12:Protrusion 12a: Tip 12b: Non-tip portion 12c: Sloped bottom surface 13: Rib section 21: Iron plate section (plate-shaped section) 21a: recess 22:Protrusion 22a: Tip 22b: Non-tip portion 23: Ring-shaped part 23a: Outer surface 51:Pile head 51a: Deformed area 61: Footing section 62: Lean concrete 100: Building foundation GL: Ground Level I: Interference position of steel pipe S: Vertical surface P:Lower end part W1: Horizontal width W2 :Horizontal width W3 :Horizontal width Y: Contact point

Claims

1. A pile head cap to be attached to the pile head of a steel pipe pile driven into the ground, Plate-shaped part and With the above steel pipe pile placed over the pile head, the plate-like portion protrudes downward from the lower surface side with a substantially constant thickness, and the protruding portion faces the inner circumferential surface on the upper edge side of the pile head, It is equipped with, In the state in which it is placed over the pile head, the horizontal width of the tip of the protruding portion is narrower than the horizontal width of the non-tip portion, which is the thickness of the protruding portion. When the pile head cap tilts from a state in which the tip of a portion of the above-mentioned protrusion is in contact with the inner circumferential surface of the upper edge of the pile head, with the point where the plate-shaped portion contacts the upper end surface of the pile head as the pivot point, A pile head cap characterized in that, with respect to the tip of the protruding portion located below the plate-shaped portion which rises due to this inclination, the lower end portion P of the point closest to the inner circumferential surface in a vertical plane parallel to the vertical plane passing through the fulcrum and the center of the pile head cap contacts the inner circumferential surface before the inclination reaches the uppermost position on the upper edge side of the pile head.

2. In the pile head cap according to claim 1, A pile head cap characterized in that, when the tip of the above-mentioned part of the protrusion is in contact with the inner circumferential surface on the upper edge side of the pile head, the contact point Y is defined as the position of contact when the vertical plane passing through the support point and the center of the pile head cap, and passing through the lower end position P, is in contact with the inner circumferential surface of the pile head, the horizontal distance between I and Y in the vertical plane passing through the steel pipe interference position I and the contact point Y is defined as C, and the distance between the lower end position P and the contact point Y is defined as B > C.

3. A pile head cap according to claim 1 or claim 2, characterized in that when the pile head cap is placed over the pile head, the tip of the protruding portion makes line contact with the inner circumferential surface in a single vertical line.

4. A pile head cap according to claim 3, characterized in that the horizontal cross-sectional shape of the tip of the protruding portion when the pile head cap is placed over the pile head is arc-shaped.

5. A pile head cap according to any one of claims 1 to 4, characterized in that the lower part of the tip of the protruding portion has an inclined lower surface that slopes downward toward the center of the steel pipe pile when the pile head cap is placed over the pile head.

6. A pile head cap according to claim 5, characterized in that the horizontal width of the inclined lower surface when the pile head cap is placed over the pile head is narrower than the horizontal width of the non-tip portion.

7. A pile head cap according to claim 6, characterized in that the horizontal cross-sectional shape of the inclined lower surface when the pile head cap is placed over the pile head is arc-shaped.

8. A building foundation comprising steel pipe piles and a foundation, characterized in that the footing portion of the foundation is located directly on a pile head cap provided on the pile head according to any one of claims 1 to 7, or via lean concrete.

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