JPH0125848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides hollow piles such as steel pipe piles having at least their tips made of steel pipes, especially hollow piles in which a bulbous part for hardening the roots is made of a hardening agent such as mortar or cement milk at the tips of the piles. Regarding the piles that are used in the construction, the protrusions for bearing pressure are placed on the inner and outer peripheries of the pile tips, shifted in position in the direction of the pile axis, to increase the adhesion strength of the root hardening bulb, and to prevent the destruction of mortar, etc. This is designed to prevent peeling and increase and stabilize the pile tip bearing capacity.

Conventionally, for example, when driving steel pipe piles as foundation piles for structures using vibration-free and noise-free construction methods, in any construction method, the tip portion 11 of the pile 10 has a first
As shown in the figure, the pile is solidified by injecting cement milk, etc. for root hardening, or it is solidified together with the ground soil to develop and stabilize the pile tip bearing capacity. In this case, the pile tip bearing capacity is the bearing pressure at the pile tip surface of the hardening bulb part a of concrete or mortar after solidification of injected cement milk, etc., and the adhesion strength between the pile wall surface and the bulb part a of the mortar etc. depends on.

In recent years, in the above-mentioned method of constructing piles without vibration or noise, in order to increase the supporting capacity of the tip of the pile 10, cement milk, mortar, or other solidifying agent is injected into the tip of the pile to harden the bulb. Part a
As shown in Figure 2, the diameter of the pile is enlarged by mechanical digging or high-pressure injection of cement milk. This is the pile circumferential support force F due to the frictional resistance f1 against the lateral pressure of the pile outer circumference in the upper part of the mortar etc.
The structure load W is supported by the pile tip support force P due to the resistance p of the tip ground at the pile tip and the frictional resistance f2 against the lateral pressure of the outer periphery of the root hardening bulb part a.

In other words, in a foundation pile whose tip is filled with a hardening agent such as cement milk or mortar and hardened,
When a load is applied to the superstructure, part of the load is supported by the frictional force around the pile, but part of it is transferred to the tip of the pile.

Therefore, the transmission of load from the pile body such as a steel pipe pile to the root hardening bulb part a such as mortar is an important factor, and especially in the case of steel pipe piles, it is important to ensure that the load is well transmitted from the pile body to the bulb part a. Otherwise, sufficient tip support force cannot be obtained.

However, in the case of steel pipe piles for which no measures have been taken at the pile tip, the load is transferred from the pile body to the bulb by bearing pressure at the pile tip and adhesion of mortar, etc. to the pipe wall. However, in general, if the compressive strength of materials such as concrete and mortar is K, then the bearing strength when a compressive force is applied with the surroundings restrained is a compressive strength of 1.5 to 2.0.
In addition, the bond strength with the steel pipe pile is less than K/100, and since the bond strength with the steel pipe wall is extremely weak, the bond is easily broken during load transfer.
Moreover, since the wall thickness of the steel pipe pile is thin, the bearing area at the tip surface is insufficient, and the steel pipe pile cannot support the load transmitted only by the mortar at the tip of the pile, and the steel pipe pile is It sinks into the mortar a1, etc., and shear failure occurs in the mortar a1 (the shear surface strength is about K/10), making it impossible to obtain a large supporting force.

It is extremely uneconomical to fill a large amount of mortar etc. to prevent this, and even if the amount of mortar filled is increased, the mortar a2 on the outer periphery of the pile is thinner than the mortar a3 inside the pile. Therefore, the amount of strain during load transmission between the pile and internal mortar a3 is different (Young's modulus is different), and as a result,
Peeling occurs from the outer wall of the steel pipe or the adhesion breaks, causing shear failure in the mortar a1 from the pile tip, and as a result, the pile sinks, leaving mortar a2 behind, and sufficient tip support is not obtained in the same way as above. do not have.

In addition, as previously proposed by the applicant, a ring-shaped blocking plate is provided on the inner periphery of the tip of the steel pipe pile, and the blocking plate increases the bearing surface and shear strength (increases the shear length of the internal mortar). Even if the load transmission to the mortar is improved, the load transmission to the mortar on the outer wall of the steel pipe is not as good as described above, and sufficient tip supporting force cannot be obtained.

Therefore, in the case of foundation piles in which the tips of hollow piles such as steel pipe piles are hardened with mortar, etc., in order to properly transmit the load at the tips of the piles and obtain safe and strong bearing capacity. The structure must be such that the load can be transmitted not by the adhesive force, which is weak in strength, as described above, but by the bearing surface, which is strong in strength.

In view of the above, it is an object of the present invention to provide a pile in which the load is sufficiently transmitted from the pile wall to the mortar, etc. on both the inner and outer surfaces, and there is no risk of peeling or destruction of the mortar, etc. in the enlarged diameter part of the root protection bulb. This is what I did.

That is, the present invention provides a hollow pile 10, such as a steel pipe pile, whose at least the tip portion is made of a steel pipe, and this tip portion is hardened with a hardening agent such as cement milk, and wherein the tip portion 11 made of the steel pipe has internal and external parts. A plurality of substantially ring-shaped protrusions 1 for supporting pressure are provided on the circumference.
2 and 13 are arranged by welding so that the inner and outer parts are shifted from each other in the direction of the pile axis.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 and FIG. 4 show examples using steel pipe piles, and as protrusions 12 and 13 for bearing pressure inside and outside,
This figure shows a case in which a plurality of ring-shaped plates or ring band-shaped plates are integrally welded to the inner and outer circumferential surfaces of the pile tip 11 at a required interval in the direction of the pile axis.
2 and 13 are ring-shaped with no irregularities on the outer periphery.

The embodiment shown in FIG. 5 is a further improvement of the above embodiment, in which a ring-shaped protrusion 1 for bearing pressure inside and outside
Relief grooves 14 and 15 are provided at required locations for pile press-fitting, such as muddy water and cement milk. It is also possible to provide the relief groove 15 only on one of the protrusions, for example, on the outer protrusion 13.

The embodiment shown in FIG. 6 has protrusions 12 for bearing pressure inside and outside,
13 shows a case in which arc-shaped divided protrusions 12' and 13', which are obtained by dividing a ring into a plurality of parts, are welded to the inner and outer circumferential surfaces of the pile tip 11 in an intermittent ring shape, and each divided protrusion 12', 13 13' and between 13' and 13' to release muddy water, cement milk, etc. during pile press-fitting 1
4,15. In this case as well, only one of the inside and outside can be configured as described above. It is also possible to combine the embodiment shown in FIG. 5 and the embodiment shown in FIG.
4 and 15 can be provided vertically shifted from each other in the circumferential direction as shown in the figure.

When the relief grooves 14 and 15 are provided as described above,
When the pile is press-fitted, muddy water, cement milk, etc. are released into the escape groove 14,
15, the press-fitting resistance is small and the press-fitting becomes easy, and the cement milk sufficiently spreads to various places.

In any of the above embodiments, the protrusions 12 and 13 for internal and external bearing pressure are arranged in multiple stages at required intervals in the axial direction of the pile, as shown in the figure, in accordance with the filling length of mortar, etc. during pile driving. In particular, in order to avoid stress concentration due to convex welding, the inside and outside are shifted in position from each other in the axial direction of the pile, for example, the inside and outside are arranged alternately. These multi-stage protrusions 12, 13
The protrusion size from the pile wall can be made different for each stage.

In addition, the present invention applies not only to the case where the pile 10 is a steel pipe pile, but also to the case where the pile 10 is a hollow concrete pile formed by connecting a steel pipe of a required length to the tip end 11 as shown in FIG. This can be achieved by welding protrusions 12' and 13' for supporting pressure, similar to those in the above-described embodiments, on the inner and outer circumferential surfaces of the tip portion 11, respectively. The steel pipe at the tip 11 is connected to a yoke plate 17 welded to the reinforcing bar 16 of the concrete pile body 10'.
are welded and connected. In this case, if the diameter of the tip 11 made of steel pipe is made larger than the diameter of the concrete pile main body 10' (Fig. 8), the end area of the ready-made pile body will be increased, the supporting force will be more stable, and the tip The pile circumferential area also becomes larger, and load transmission to the bulb for root hardening, such as mortar, becomes even better.

The piles such as steel pipe piles according to the present invention have the above-mentioned configuration, and when the piles are driven using vibration-free and noise-free construction methods, the tips of the piles are filled with cement milk, mortar, etc. for foot hardening. Either by injecting a solidifying material and solidifying it, or by solidifying it together with the ground earth and sand, a bulbous part a for foot hardening is created using expanded mortar or the like, and the pile tip supporting force is obtained.

Therefore, in the present invention, a plurality of protrusions 1 for bearing pressure are provided on the inner and outer circumferences of the tip portion 11 of the pile 10, respectively.
2 and 13 are provided, so when the pile receives a structural load, the lower surfaces of the inner and outer protrusions 12 and 13 act as bearing surfaces, and the load is distributed to the bulb part a for foot protection such as mortar. This prevents the load W of the structure from being concentrated on the tip of the pile, and also increases the adhesion of mortar, etc. to the pile wall.

Therefore, the load transfer from the pile tip 11 to the root-hardening bulb part a, such as mortar, is carried out smoothly and extremely well both inside and outside the pile wall, and there is no risk of shear failure of the foot-hardening bulb part a, and sufficient strength is maintained. You can expect it. Among them, the bulb part a for root hardening of mortar etc.
This is particularly effective when expanding the diameter of the pile to be larger than the diameter of the pile as shown in Fig. 3, and prevents peeling and destruction of the mortar a1 in the enlarged diameter portion surrounding the outer periphery of the pile wall at the tip 11. A large supporting force corresponding to a can be fully expected.

In addition, since the load transmission, that is, the transmission of the supporting force, is not carried out only by the adhesion force of mortar etc. to the inner and outer surfaces of the pile wall, but is distributed by the bearing pressure surfaces of the respective protrusions 12 and 13 as described above, By reducing the amount of solidifying materials such as injected cement milk compared to conventional methods,
Alternatively, it can be replaced with a compound that is weak in strength, which is economical.

Furthermore, as mentioned above, in order to transmit the load at the bearing pressure protrusions 12 and 13 on the inner and outer peripheries of the pile tip, if the root hardening bulb part a such as mortar is sheared, the shear surface is , occurs not below the tip of the pile, but below the tip of each of the plurality of protrusions 12, 13. Therefore, the shear length is longer than in the case where the shear plane does not have the protrusions and the shear surface is below the tip of the pile. As a result, the shear resistance at the time of load transmission increases and shear failure does not occur, and the load can be transmitted favorably and safely due to the bearing pressure at the convex portion as described above.

In particular, in the case of the present invention, since the plurality of inner and outer protrusions are arranged at different levels in the direction of the pile axis, the welding distortion and residual stress due to welding of the welded parts of the protrusions to the steel pipe are small. There is no risk of the strength of the welded part at the base of this protrusion decreasing, and a large load can be transmitted, and the load is transmitted to the root hardening bulb such as mortar at different locations inside and outside by this protrusion. , stress concentration does not occur during load transmission, there is no risk of damage to the steel pipe wall, and the amount of mortar distortion is small, so that load transmission is performed well. This, together with the effect of increasing the bearing area due to the protrusions and increasing the shear length of the bulbous part of the mortar due to the arrangement of the protrusions in multiple stages, reduces the adhesion between the steel pipe wall and the mortar. It is even more excellent in preventing peeling, and it is possible to obtain an extremely good and strong tip supporting force.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the construction state using a conventional steel pipe pile, Fig. 2 is an enlarged cross-sectional view of a part of the bulb for root hardening using mortar, etc., and Fig. 3 is a pile according to the present invention (steel pipe pile). Figures 4 to 6 are partial half-sectional perspective views showing different forms of bearing pressure protrusions, and Figures 7 and 8 are cross-sectional views showing the construction state of the pile. It is a partial vertical cross-sectional view showing an example of a concrete pile made of. 10...Pile, 10'...Concrete pile body,
11... tip, 12, 13, 12', 13'...
Protrusions for bearing pressure, 14, 15... Relief groove, a... Bulb part for root hardening such as mortar, a2... Portion of mortar etc. with expanded diameter on the outside of the pile wall.

Claims (1)

[Scope of Claims] 1. A hollow pile with at least a tip made of a steel pipe, the tip of which is hardened with a hardening agent such as cement milk, wherein a plurality of piles are provided on the inner and outer peripheries of the tip made of the steel pipe, respectively. A pile, such as a steel pipe pile, characterized in that approximately ring-shaped protrusions for bearing pressure are arranged by welding with the inner and outer positions shifted in the direction of the pile axis. 2. Claim 1, wherein the hollow pile is a concrete pile formed by connecting a steel pipe of a required length to its tip, and in which protrusions for bearing pressure are arranged by welding on the inner and outer surfaces of the steel tube at the tip. Piles such as steel pipe piles as described in Section 1.