JP2004316411A - Assembling type steel pipe pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive steel pipe pile which is divided into two sections of a distal-end part for enlarging a diameter of a pile and a supplementary part, so that a damage in a blade is avoided and a long-term bearing capacity in the distal-end part is improved. <P>SOLUTION: The steel pipe pile 21A is divided into the distal-end part composed of an excavating edge 23 and a blade 24 for enlarging the diameter and the supplementary part of an extension steel pipe 25. The distal-end part for enlarging the diameter and the supplementary part are connected with a suitable means when needed, which fulfills manufacturing, storage and transportation or the like at a low cost and that improves a practical bearing capacity by providing a range in choosing a diameter of the steel pipe to be used for both parts. The range of choice in the steel pipe diameters can be widened by utilizing a steel pipe of a different diameter 22 at the distal-end part for enlarging the diameter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a steel pipe pile buried in soil to strengthen the ground.

The ground supports the load from structures such as buildings and civil engineering structures installed on land. Therefore, when the weight of the structure exceeds the bearing capacity of the ground, anomalies usually begin to appear in the form of differential settlement, and after a short or long period of time, the slope becomes large and becomes unusable. Therefore, when constructing a structure having a certain weight, a boring geological test of the installation location is performed in advance to confirm the ground bearing capacity.

When the support capacity is insufficient and the ground needs to be strengthened, the most suitable means is selected according to the structure.
For example, in the case of a building, a pile made of concrete or steel pipe molded to strengthen the supporting force is used. The piles are driven into the ground by using the friction between the pile surface and the stratum, or buried in the stratum having the necessary bearing capacity. The type of pile used depends on the height and weight of the building and the depth to the bearing stratum.

In order to bury concrete or steel pipe piles, a method of driving a pile using a vibrator or a hammer, a method of solidifying and inserting holes drilled with screws, a steel pipe 2 of a pile 1 as shown in FIG. There is a construction method in which a pile with an excavating blade 3 and a blade 4 attached to the tip is regarded as a screw and rotated and penetrated. In the rotary penetration method, a steel pipe having an outer diameter of 114.3 to 247.4 mm is used, and a blade having a diameter 2 to 3 times the diameter of the steel pipe is attached to the outside thereof. As the blade diameter increases, the effective area of the pile tip increases, and the long-term tip supporting force for the N value increases.

According to the catalog published by the Japan Building Center (performance evaluation method for rotary penetrating steel pipe piles),
The relationship between the body diameter of the foundation pile (outer diameter of the steel pipe pile) and the maximum construction depth is described as 114.3 mm / 14.9 m, 247.4 mm / 34.8 m. The steel pipe is selected from a length of 3 to 6 m, and the steel pipe is added as needed. This method has the advantages of low noise, no soil removal when piles are buried, and no contamination since water is not used.
Catalog of Japan Architecture Center, 2002 edition

The rotating penetrating steel pipe pile supports the load with the lowermost face of the pile and the blades. Therefore, even with steel pipes of the same diameter, increasing the blades increases the supporting force and reduces the number of piles required. On the other hand, rotating penetrating steel pipe piles penetrate through the stratum where viscous, sandy, conglomerate, etc. are mixed during embedding to obtain propulsion from the spiral blades, and reach the final hard support layer and harder than the pile diameter During the process, there is a problem that the blade is subjected to an unexpectedly high force and is easily damaged. Of course, this damage is not visible.

If a thick plate is used, a strong large-diameter blade can be made.However, since the blade is connected to the steel pipe by welding, if there is a difference in the plate thickness between the blade and the steel pipe, the strength of the steel pipe base material in the welded part will be insufficient, There is also a problem that the strength of the pile decreases. Therefore, the choice of the diameter and thickness of the steel pipe is limited unless it is a special steel pipe having a large wall thickness. In order to increase the blade strength, it is necessary to select a steel pipe having a large outer diameter, which causes a problem in cost.

Also, considering that the role of the pile is to surely transmit the load from the structure to the support layer, the upper part excluding the lowermost periphery can withstand the rotating force (torsion) when buried, and the allowable range when supporting the load It is sufficient if the steel pipe has a strength that can be accommodated in the bending (bending). Therefore, there is a problem that the diameter of the steel pipe on the ground surface side is too large for the load due to the piles, which is uneconomic. An object of the present invention is to provide an assembling steel pipe pile provided with cutting blades and blades that solves the above-mentioned problems.

The present invention relates to a steel pipe pile having a cutting edge and a blade attached to a tip thereof,
The pile is divided into a steel pipe and a supplementary part with a steel pipe connected above the same part as the tip part to be expanded consisting of a drilling blade and blades, and the steel pipe of both the tip and the supplementary part can be selected arbitrarily.
It is a prefabricated steel pipe pile where both are connected by appropriate means.

The following effects were obtained from the assembled steel pipe pile of the present invention.
Since the pile was divided into a tip portion consisting of a drilled blade and an expanded steel pipe with blades and a supplementary part consisting of a reinforced steel pipe, costs required for procurement, storage and transportation were reduced. In addition, by dividing the pile into two parts, the selection range of the steel pipe of the supplementary part is expanded, and each connection means by welding or flange can be selected for assembling, and it can be supplied according to the progress of work because it is assembled at the site Delivery time management such as assembly, transportation and storage has become easier.

Since the blades are reinforced with reinforcing plates and struts, the chance of damaging the blades has been drastically reduced. When a different diameter steel pipe or a thick steel pipe is used, the blade diameter can be increased by using a thick plate without the influence of the steel pipe of the supplementary portion, and the effective area of the pile tip can be increased. When the blade diameter is constant, the pressure receiving area does not change even if the diameter of the steel pipe at the tip portion is changed and the blade width is increased or decreased. Therefore, the reduction of the blade width enhances the economical effect on the material and the implementation, and also helps prevent the blade from being damaged. Accordingly, options for the blade diameter and the diameter of the steel pipe at the tip end for securing the supporting force are expanded, and the application to the ground having relatively low strength is sufficiently enabled.

When the pile is rotated and the tip of the soil is scraped with a drilling blade and discharged upward with the outer blade, the pile with a difference between the inner diameter of the tip and the inner diameter of the supplementary part, even if the inside of the pipe at the tip is open, Due to the effect of reducing the inner diameter of the different diameter steel pipes, the soil inside the pipes is compacted and closed, and the same bearing capacity as when the pile tip is closed is obtained. Also, different diameter steel pipes and thick steel pipes used for prefabricated steel pipe piles can be used as off-the-shelf products, which contributes to cost reduction.

The present invention divides the pile into a steel pipe, an excavation blade and a blade, and a supplementary part connected upward from the part, with the aim of increasing the supporting force of the rotary penetrating steel pipe pile, and connecting the two at any time. It is a prefabricated steel pipe pile that was made possible. In other words, reinforcement of blades to prevent damage during embedding, which is likely to occur on large-diameter blades, and making the difference between the steel pipe diameters of both the tip and the supplemental parts, expanding the choice of supplementary part steel pipes, supporting A structure that can easily increase the force was achieved.

The structure to prevent damage to the blades is located at the top of the steel tube at the tip end consisting of a steel pipe, a cutting blade, and a blade.
Reinforcement plates were attached within the range not exceeding the blade diameter, and struts were lowered from at least three places of the reinforcement plate to the blades and fixed therethrough in order to prevent damage to the blades that might occur during excavation. In addition, a structure in which a steel pipe of a supplementary portion is connected upward using a reinforcing plate is adopted. In addition, when the inner diameter of the reinforcing plate is reduced, it is easier to use a thin steel pipe for the supplemental part with respect to the steel pipe at the tip part.

At the tip part consisting of a steel pipe, a drilling blade and a blade, use different diameter steel pipes with different diameters at both ends, attach the drilling blade and the blade with the expanded side facing down, and supplement the steel pipe on the smaller diameter side. Are connected. As the different-diameter pipe, a pre-made pipe different-diameter joint or a tapered pipe may be used, or an arbitrary curved surface or a taper may be newly selected and formed between the entrance and the exit.

Instead of using different diameter steel pipes, use a steel pipe thicker than the supplemental steel pipe at the tip consisting of the steel pipe, excavating blade and blades, attach a reinforcing plate to the upper surface of the thick steel pipe, and attach It is good also as a structure which connects a steel pipe. The connection between the tip and the supplemental part utilizes welding or flanges and bolts and nuts. Incidentally, the tip portion may be integrated by casting. In this case, the connecting means may be provided with a flange on the casting side and the steel pipe side and connected with bolts and nuts, or may be replaced with a female screw on the casting side with a female thread on the casting side instead of the flange. And fix them by screw connection.

Prefabricated steel pipe piles, which are divided into two parts, the tip and the supplemental part, can easily cope with shallow support layers. In addition, when the pile rotates and the excavating blade at the tip cuts the earth and discharges it upward with the blades, the movement of part of the soil to enter the inside of the pile is caused by the shape of the different diameter part whose diameter decreases from the tip of the pile. Compress and densify the earth and sand to prevent it. Therefore, in the steel pipe pile having an enlarged diameter according to the present invention, the same supporting force can be obtained as when the pile tip is closed or when a plate for closing is used on the inner surface of the pipe near the tip.

Steel of the steel pipe and complementary portion of the tip portion of FIG. 3, both ends of the different diameter steel pipe of FIG. 5, steel of the steel tube and complementary portion of the tip portion of FIG. 8, the ratio of the diameter D ₂ and D ₃ shown in each 1. It is selected from the range of 2 to 2.5, preferably 1.5 to 2.5, more preferably 1.5 to 2.0. This figure can be made smaller when long piles from the surface to the support layer must be used long, and large for short and short piles.

FIGS. 2A and 2B are a side view and a bottom view of the pile 11. Two excavating blades 13 are attached to the tip of a steel pipe 12 having an outer diameter D ₂ (see FIG. 3) constituting a pile, and a helical blade 14 having an outer diameter D ₁ with a required angle is attached thereon. When the pile rotates, it goes underground with the help of excavating blades and blades. A reinforcing plate 15 was fixed above the blade so that the blade was not damaged when the pile was buried, and a column 16 was lowered onto the blade from a position obtained by dividing the circumference of the plate into four parts, and penetrated and reinforced. The struts are determined in consideration of the thickness and size of the blade, and the number is not limited to four.

FIG. 3 is a side view with a partial cross section when FIG. 2A is viewed from the right arrow a direction. Steel tube of the distal end portion of the pile 11 12 is indicated by the length L _1, including the thickness of the reinforcing plate 15. The reinforcing plate also serves as a reinforcing surface of the blade and a connection surface with the steel pipe 18 of the supplementary portion. The excavating blade 13 is fixed to the tip of the steel pipe and the column 16. Therefore, the position of the column may change depending on the number of drilling blades and the mounting position.

And the length L ₁ of the tip portion to the length L ₂ replenishing the steel pipe 18 of the supplemental portion of the outer diameter D ₃ finish pile 11 of length L. The steel pipe of the tip part and the supplementary part consisting of the steel pipe 12, the excavating blade 13 and the blade 14 may be connected and assembled as needed. The diameter of the steel pipe at both the tip and the supplement does not necessarily have to be the same, and the diameter can be freely selected in consideration of conditions such as the ground. The piles are mainly connected by welding, but may be connected by welding or bolts using a flange 19 (virtual line) between the steel pipe and the reinforcing plate of the supplementary portion.

FIG. 4 is a cross-sectional view of the ground showing a comparison between the steel pipe pile 1 of FIG. 1 described in the [Background Art] section and the assembling steel pipe pile 11 in which the diameter of the steel pipe is changed at both the tip and the supplement of the present invention. To support the load W in the former pile, it is necessary length to reach the firm support layer N ₂ of the required thickness. However, since the formation of different strength and thickness exists between extending the rigid support layer and expanding the tip effective area as the latter pile, the desired thickness even near weak supporting layer N ₁ on the ground any Can be used effectively.

Pile for use in a weak supporting layer N ₁ and the rigid support layer N _2, the length and diameter are different when the same load. The blade diameter and the pipe diameter (D, D ₂ ) are determined by the support layer, the pipe diameter (D, D ₃ ) is determined by the load, and the length (L) is determined by the depth to the support layer. Therefore, the pile 1 having the same overall length D is long, and the cost including labor for burying is high. Pile 11 of the present invention is thicker L ₁ and shorter D ₂ tip portion, since it corresponds to thin the short D ₃ supplementary moiety L _2, the total length of the pile is kept low costs, including short buried effort.

FIGS. 5A and 5B are a side view and a bottom view of the flange-connected pile 21. Connecting the digging edge 23 and the blade 24 on the large diameter side using different diameter steel pipe 22 to the tip portion of the length L _1. And replenishing the steel pipe 25 of length L ₂ of the supplementary part to the small-diameter side finish pile length L. The different diameter steel pipe may be formed by processing such as drawing while setting the required diameter of the steel pipe, but it is also possible to select and use appropriate dimensions from different diameter joints for piping.

Since the thickness of the different diameter steel pipe 22 is increased in addition to the area on the ground side (large diameter side), the outer diameter can be increased by using a thick plate for the blade 24, and the pile supporting force can be increased. Therefore, even with a pile having a thin steel pipe in the supplementary portion, the same effect as that obtained by adding a large blade to a single steel pipe and increasing the supporting force can be obtained. Even if the inside of a pile using a different diameter steel pipe at the tip is hollow, the excavated sediment pushed up from the pile bottom to the inside of the pile when the pile is buried is compacted and blocked at the reduced part of the different diameter steel pipe, and the pile tip is closed. In this case, the same supporting force can be obtained as when the closing plate is used on the inner surface of the pipe near the distal end.

FIGS. 6A and 6B are a side view and a bottom view of a pile 21A having a length L in which a steel pipe 25 of a supplementary portion is directly added to the small diameter side of the different diameter steel pipe 22. As the different-diameter steel pipe, one having both ends connected by a gentle curved surface as shown in FIG. 7A or a tapered pipe 29 as shown in FIG. 7B is used. In the case of using a different diameter steel tube off the shelf, use conditions are limited because there is a limit to the magnitude aperture ratio D _{2 /} D ₃ and length L _1. In the case of the flange connection, when the tip portion is made of a cast product, the processing time is greatly reduced, and good results are obtained in terms of cost.

FIG. 8 is a side view with a partial cross section of a pile 31 of length L. The effect of dividing into both the tip and supplemental portions is the same as in the first embodiment. The reinforcing plate 36 fixed to the upper end of the digging edge 33 and a length connecting the blade 34 L ₁ thickness T ₁ of the front end portion of the thick steel pipe 32, connect the steel pipes 35 supplemental portion of the length L ₂ thickness T ₂ I do. The use of a thick steel pipe allows the blades to be made thicker, so that the supporting force can be increased by expanding the diameter. The presence of the reinforcing plate is convenient for connection when a thin steel pipe is used for the supplementary part. In addition, when the tip portion is a cast product, the processing time is greatly reduced and good results are obtained in terms of cost, but a connecting flange is required on the steel pipe side of the supplement portion.

It is a side view and a bottom view of a rotary penetration pile. (Conventional example) (A, B) shows the side and bottom views of the pile. (Example 1) It is the side view with a partial cross section which looked at FIG. 2 (A) from the a direction of right arrow. A cross-sectional view of the ground shows a comparison between the pile shown in Fig. 1 and the pile with different steel pipe diameters at the tip and supplementary parts shown in Fig. 2. (A, B) shows the side and bottom views of the pile. (Example 2) (A, B) shows a side view and a bottom view of a pile of another embodiment. (A, B) is a side view of a different diameter pipe. It is a side view with a partial cross section of a pile. (Example 3)

Explanation of reference numerals

11, 21, 21A, 31 Piles 12, 32 Steel pipe (tip)
13,23,33 Excavating blades 14,24,34 Blades 15,36 Reinforcement plates 16 Posts 18,25,35 Steel pipe (supplementary part)
22 Different diameter steel pipe (tip)

Claims (6)

In a steel pipe pile with a drilling blade and blade attached to the tip,
Piles (11, 21, 21A, 31) are connected to steel pipes (12, 22, 32) and drilling blades (13, 23,
33) and the blades (14, 24, 34) are divided into supplemental portions by steel pipes (18, 25, 35) that are connected to the upper end of the enlarged tip portion composed of the blades (14, 24, 34).
An assembling steel pipe pile with a structure in which the steel pipe of the tip and the supplemental part can be arbitrarily selected and connected by appropriate means. In the tip part consisting of a steel pipe (12), a cutting blade (13) and a blade (14),
A reinforcing plate (15) is attached above the blade so as not to exceed the blade diameter, and a support (16) is lowered from at least three places of the reinforcing plate to the blade and fixed therethrough. The assembly type steel pipe pile according to claim 1, wherein (18) is connected. In the tip part consisting of a steel pipe (22), a cutting blade (23) and a blade (24),
2. The prefabricated steel pipe according to claim 1, wherein different diameter steel pipes having different diameters at both ends are used, and the excavating blade and the blade are attached with the enlarged diameter side facing downward, and the supplementary steel pipe (25) is connected to the smaller diameter side. Pile. In the tip part consisting of a steel pipe (32), a cutting blade (33) and a blade (34),
A steel pipe (32) thicker than the steel pipe (35) of the supplementary part, a reinforcing plate (36) is attached to an upper end of the thick steel pipe, and the steel pipe (35) of the supplementary part is connected to the reinforcing plate. 2. The assembled steel pipe pile according to 1. 5. The assembled steel pipe pile according to claim 1, wherein the appropriate connection means between the tip and the supplemental portion is a weld or a flange. The assembled steel pipe pile according to any one of claims 1 to 5, wherein the diameter ratio of the steel pipe used for both the tip and the supplemental part or the diameter ratio of the different diameter steel pipe is selected from a range of 1.2 to 2.5.