JPH09143996A - Casing pipe and method for constructing pile foundation using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorter the construction period and reduce the cost of a pile foundation by providing a threaded joint at the end of each casing pipe, and placing and drawing the casing pipes into and out of the ground while connecting them together. SOLUTION: An annular male joint member 10 and an annular female joint member 20 are welded, respectively, to the upper end of the steel pipe 1a of a casing pipe and the lower end of the casing pipe 2. An externally threaded part 15 is provided on the outside peripheral surface of the male joint member 10, and an internally threaded part 25 is provided on the inside peripheral surface 21 of the female joint member 20. The thread angles of the ridges and grooves of the externally and internally threaded parts 15, 25 are set to 25 to 40 deg.. Both of the joint members 10, 20 are made equal in bore to steel pipes 1a, 1b and have their inside peripheral surfaces formed flush with each other. The casing pipe 1 is passed through a ground drilling machine, used in drilling, and placed in the ground. Next, the casing pipe 1 is connected to the casing pipe 2 by a threaded joint A to drill the ground again, This process is repeated plural times to connect the required numbers of pipes together. The pipes are drawn out as they are disconnected from one another.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casing pipe which is connected to a plurality of piles and is laid on the ground when constructing a pile foundation, and a method for constructing a pile foundation using the casing pipe.

[0002]

2. Description of the Related Art Steel pipe piles and H
Steel piles and concrete piles are used. When constructing these various piles, first, a method of placing a casing pipe while excavating the ground by an excavator and inserting the pile inside the casing pipe is adopted. At this time, when the pile length to be built is set to be longer than the existing casing pipe, the casing pipes are driven into the ground while being connected by welding, and when the casing pipes are driven, The excavator is taken out leaving the casing pipe in the ground, the pile is inserted inside the casing pipe, and then the casing pipe is pulled out from the ground while cutting the welded portion. The extracted casing pipe will be reused when the next pile is installed.

Construction of a pile foundation using a casing pipe is generally performed when constructing a large-scale structure, and the steel pipe constituting the casing pipe has a large diameter (25 mm).
0 mm to 1000 mm) is used.

[0004]

By the way, when the casing pipes are laid in the ground during the construction of the pile foundation as described above, the casing pipes are connected by welding. There was a problem that it took time and effort to cut the welded parts during welding and drawing work.

The present invention has been made in view of the above circumstances, and improves workability in placing and withdrawing casing pipes, while suppressing work costs.
The purpose is to shorten the construction period of the pile foundation and reduce the construction cost.

[0006]

The casing pipe according to claim 1 is a structure in which a plurality of casing pipes are connected and placed in the ground when constructing a pile foundation, and the outer peripheral surface at the end of one casing pipe. A threaded joint comprising a male threaded portion provided on the inner peripheral surface of the other casing pipe connected to the one casing pipe, and a female threaded portion screwed to the male threaded portion. It is characterized by being provided.

In the casing pipe according to the first aspect, the casing pipes are connected to each other by screwing the male screw portion provided on one casing pipe and the female screw portion provided on the other casing pipe. It

According to a second aspect of the present invention, in the casing pipe, when the screw joint including the male screw portion and the female screw portion is connected, the inner peripheral surface along the axial direction is flush and the inner diameter is uniform. Are formed.

In the casing pipe according to the second aspect, since the inner peripheral surface along the axial direction is formed to be flush in the connected state, the excavator is inserted into and removed from the casing pipe, and The insertion is done smoothly.

In the casing pipe according to the third aspect, the lead angle given to the male screw portion and the female screw portion is 25 ° to.
It is characterized in that it is set between 40 °.

According to the third aspect of the present invention, the connection between the casing pipes can be easily released during the pulling-out operation while maintaining the required joint strength between the casing pipes during the placing operation.

According to a fourth aspect of the present invention, there is provided a method for constructing a pile foundation using a casing pipe, wherein an excavator is passed through the casing pipe to excavate the ground, and when the excavator descends. A plurality of casing pipes are connected to each other by the screw joint, and when the casting of the casing pipes is completed, the casing pipes are left in the ground, the excavator is taken out through the space, and the piles are inserted into the space. After that, the casing pipe is pulled out from the ground while releasing the connection by the screw joint.

In the method for constructing a pile foundation using a casing pipe according to a fourth aspect of the invention, since the casing pipes are connected to each other and the connection is released from each other by a screw joint, the workability in placing and extracting the casing pipes is improved. Further, since the excavator is inserted, taken out, and the main shaft is inserted along the inner peripheral surface of the casing pipe that is formed flush, the work in the excavator insertion, take-out work, and main pile insertion work The property is improved. In addition, the casing pipe can be easily reused.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a casing pipe and a method for constructing a pile foundation using the casing pipe according to the present invention will be described in detail with reference to FIGS.

Large diameter (about 250 mm to 1000 mm)
As shown in FIG. 1, the casing pipes 1 and 2 are connected to each other by a screw joint A formed of a male joint member 10 and a female joint member 20 provided at respective opposite ends as a connecting means.

An annular male joint member 10 is fixed to the upper end of the steel pipe 1a forming the main body of the casing pipe 1 located below, with its axis aligned with the steel pipe 1a. The inner diameter of the joint end of the male joint member 10 is equal to the inner diameter of the steel pipe 1a, and these fixed portions are firmly joined by welding.

A taper portion 12 is provided on the outer peripheral surface 11 of the male joint member 10 near the portion fixed to the steel pipe 1a so that the outer diameter of the male joint member 10 gradually increases from the lower portion to the upper portion. A step portion 13 is provided in the circumferential direction so as to reduce the outer diameter of the male joint member 10 in the portion above the taper portion 12, and the portion above the step portion 13 extends upward. Existing tubular wall 1
4 is provided, and the tubular wall portion 14 is provided with a male screw portion 15 along the circumferential direction.

An annular female joint member 20 is fixed to the lower end of the steel pipe 2a constituting the main body of the casing pipe 2 located above, with its axis aligned with the steel pipe 2a. The inner diameter of the joint end of the female joint member 20 is equal to the inner diameter of the steel pipe 2a, and these fixed portions are firmly joined by welding.

A taper portion 22 is provided on the outer peripheral surface 21 of the female joint member 20 near the portion fixed to the steel pipe 2a so that the outer diameter of the female joint member 20 gradually increases from the upper portion to the lower portion. The portion below the taper portion 22 is a tubular wall portion 23 extending downward,
A female screw portion 25 that is screwed into the male screw portion 15 is provided on the enlarged inner peripheral surface 24 of the tubular wall portion 23.

The shapes of the male screw portion 15 and the female screw portion 25 are, as shown in FIG. 2, the screw thread in the axial direction of the casing pipes 1 and 2 with respect to the screw thread height (groove depth) h. The width w of the (groove) is set wide, and the screw thread (groove)
The thread angle forming the inclined portion, that is, the lead angle θ of the male screw portion and the female screw portion is set in the range of 25 ° to 40 °.

The casing pipes 1 and 2 are connected by screwing the male screw portion 15 and the female screw portion 25, and the male joint member 1 is connected at this connecting portion.
Step portion 13 on the 0 side and annular wall portion 2 on the side of the female joint member 20
The lower end edge of 3 coincides with each other, and a bulging portion is formed between the steel pipe 1a and the steel pipe 2a by the male joint member 10 and the female joint member 20. Also, the male joint member 1
0 and the inner diameter of the female joint member 20 are steel pipes 1a, 2a.
Since the inner peripheral surface which is equal to the inner diameter of and which extends in the axial direction is formed flush, as a result, an inner space (space) S having a uniform inner diameter is formed in the connected casing pipes 1 and 2.

In the case of constructing a pile foundation using the casing pipe having the screw joint A constructed as described above, the work is carried out by the following procedure.

First, excavation is started in a state where the casing pipe 1 is inserted into the diameter-expanding bit (ground excavator). Since the diameter-expanding bit has a hole having a diameter larger than the outer diameter of the casing pipe 1, the casing pipe 1 is gradually driven into the ground as the diameter-expanding bit submerges.

When the casing pipe 1 is almost completely driven into the ground, the excavation is temporarily stopped, the rod of the diameter expansion bit is extended, the casing pipe 1 is connected to the casing pipe 2 by the screw joint A, and the excavation is performed again. To start. The above procedure is repeated, and a plurality of casing pipes are connected and extended to drive the ground into the ground for the required length.

After the casting of the casing pipe is completed, the casing pipe is left in the ground and only the diameter-expanding bit is taken out. Instead, the main pile is inserted into the internal space S of the casing pipe.

When the main pile is completely inserted, only the casing pipe is pulled out. When the connection part of the screw joint A is exposed from the ground in the process of pulling out, the connection is released from the part and the casing pipe located above is removed.

When all the casing pipes are pulled out from the ground, only the main piles remain in the ground and the placing of the pile foundation is completed. The extracted casing pipe will be reused when the next pile is installed.

When the pile foundation is constructed using the casing pipe provided with the screw joint A, the following effects can be obtained.

When the casing pipes are connected to each other at the time of placing the casing pipes, the connection is made by screwing the screw joint A, and the welding work as in the prior art is abolished. And the cost required for welding can be reduced.

When disconnecting the casing pipes during the operation of pulling out the cast casing pipes, the connecting portions are separated by releasing the screwing of the screw joint A, and the conventional welding portion is cut. Since the work is abolished, the workability of the drawing work is improved, and the cost required for cutting the welded portion can be reduced.

Since the casing pipes that have been pulled out are used again when the next pile is built, the workability of placing and pulling out the casing pipes is improved each time and the work cost is reduced. It is possible to shorten the construction period of the foundation and reduce the construction cost.

Further, by adopting the screw joint A,
Compared to the case of connecting by welding and cutting the welded part as in the past, the shape of the connected part is less likely to collapse,
The life of the connecting part is significantly longer than in the past.

With respect to the shapes of the male screw portion 15 and the female screw portion 25 in the threaded joint A, when the lead angle is set to be larger than 40 °, the screws stand up easily and come off, but the tightening strength is weak. If the lead angle is set to be smaller than 25 °, the tightening strength will be strong, but the screws will be too tight and will not come off easily. However, in this embodiment, the lead angle is 25 ° to 40 °.
Since it is set in the range of °, it is possible to easily release the connection of the casing pipes during the pulling-out work, while maintaining the required joining strength between the casing pipes during the placing work.

Since the casing pipe in the connected state has the internal space S having a uniform inner diameter formed therein, it is possible to smoothly take out the expanded diameter bit and insert the main pile.

Further, the steel pipe 1a (2a) constituting the main body of the casing pipe 1 (2) can be an existing one having a small wall thickness, so that the manufacturing cost per casing pipe can be kept low. You can

In the present embodiment, the male screw portion is directed upward and the female screw portion is directed downward, but the construction and operation have been described, but it is also possible to carry out the construction by reversing these screw portions. No problem. Also, the male (female) screw part is provided on the male (female) joint member fixed to the casing pipe.
The casing pipe itself may be provided with a screw portion.

[0037]

According to the casing pipe of the first aspect of the present invention, since the casing pipes can be connected and disconnected easily and at low cost, the workability in casting and withdrawing the casing pipes is improved. At the same time, the work cost can be reduced.

According to the casing pipe of the second aspect, the inner peripheral surface along the axial direction of the casing pipe is formed flush with each other in the connected state, so that the excavator can be inserted into and removed from the casing pipe, and the main piles can be installed. It is possible to improve workability in insertion work of.

According to the casing pipe of the third aspect, the lead angles of the male screw portion and the female screw portion are 25 ° to 4 °.
Since it is set in the range of 0 °, it is possible to easily release the connection of the casing pipes during the pulling-out work, while maintaining the required joining strength between the casing pipes during the placing work.

According to the method for constructing a pile foundation using a casing pipe according to claim 4, workability is improved in the operations of placing and extracting the casing pipe, inserting and removing the excavator, and inserting the main pile. Can be
Moreover, since the casing pipe can be easily reused, as a result, the construction period of the pile foundation and the construction cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of a casing pipe according to the present invention.

FIG. 2 is an enlarged view showing a shape of a screw part in a screw joint of a casing pipe according to the present invention.

[Explanation of symbols]

 A screw joint S internal space θ lead angle 1, 2 casing pipe 10 male joint member 11 outer peripheral surface 15 male screw portion 20 female joint member 24 inner peripheral surface 25 female screw portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Saburi 1528 Nakanishita, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture Mitsubishi Materials Corporation Gifu Works (72) Inventor, Kazuo Fujio Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture 1528, Nakashinden, Gifu Works, Mitsubishi Materials Corporation

Claims (4)

[Claims] 1. A casing pipe which is connected to a plurality of pile foundations and placed in the ground when constructing a pile foundation, wherein a male screw portion provided on an outer peripheral surface of an end portion of one casing pipe and the one casing pipe. A casing pipe provided on an inner peripheral surface at an end portion of the other casing pipe to be connected, and provided with a screw joint including the male screw portion and a female screw portion screwed together. 2. When the threaded joint including the male screw portion and the female screw portion is connected, the inner peripheral surface along the axial direction is made flush so that a space having a uniform inner diameter is formed. The casing pipe according to claim 1. 3. The casing pipe according to claim 2, wherein the lead angles given to the male screw portion and the female screw portion are set between 25 ° and 40 °. 4. The ground is excavated after the excavator is passed through the casing pipe, and a plurality of casing pipes are connected to the ground by the screw joint as the excavator descends. After placing the casing pipe, the casing pipe is left in the ground, the excavator is taken out through the space, the pile is inserted into the space, and the casing pipe is ground while disconnecting the screw joint. The method for constructing a pile foundation using a casing pipe according to claim 1, wherein the pile pipe is pulled out from the pile pipe.