JPH0942239A - Structure of joint for steel pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate joining of steel pipes with each other and to prevent separation therebetween by interposing resilient rings to prevent separation of a fitting shaft part and a fitting cylinder part from each other through engagement of respective annular grooves with the interior of two annular grooves superposed with each other through engagement. SOLUTION: In joining of steel pipes 1 and 2 with a joint with each other, a resilient ring 30 is fitted in the annular groove 10 of the engaging shaft part 3 of one steel pipe 1 and the fitting cylinder part 4 of the other steel pipe 2 is fitted in from the outside. In this case, since the diameter of the resilient ring 30 is gradually reduced by pressing an inclined outer surface 30a by the inner surface of the fitting cylinder part 4, the fitting cylinder part is pushed in by a force against the friction force of a contact part. This structure, since only by fitting the fitting cylinder part of one steel pipe in the fitting cylinder part of the other steel pipe, simplifies a joining work at a work site. Thus, the structure is suitable for a civil engineering site.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a joint portion of steel pipes suitable for joining steel pipes buried in the ground for reinforcement in a tunnel construction by the NATM method.

[0002]

2. Description of the Related Art In order to reinforce the peripheral wall of a tunnel excavated in soft ground, a method of burying a steel pipe in the ground and injecting a fixing agent or the like is adopted. In this construction method, a steel pipe is often embedded at the same time as drilling using a expandable / reducible bit as described in, for example, JP-A-6-294271. As shown in FIG. 6, this scalable bit B
Is capable of being expanded to a diameter larger than the outer diameter of the steel pipe P at the time of drilling and contracted to a diameter smaller than the inner diameter of the steel pipe at the time of withdrawal. Fit a steel pipe for burying in the section,
While drilling a hole H having a diameter larger than the outer diameter of the steel pipe with the rock drill D, the steel pipe is simultaneously inserted. When the hole and steel pipe having a predetermined depth have been embedded, the bit is contracted so that the bit and the drill rod are pulled out through the inside of the steel pipe, and only the steel pipe remains in the hole.

A large number of through holes communicating inside and outside are formed in the outer peripheral portion of the steel pipe. When the fixing agent is injected from the end of the steel pipe facing the outside of the hole, the fixing agent passes through the inside of the steel pipe. Is discharged through and penetrates into the hole wall portion, and fills the gap between the steel pipe and the hole wall. Thereby, the soft ground is reinforced.

[0004]

The length of the steel pipe used in the above method is almost the same as the length of the drilled rod, and usually it is several meters (actually, it is about 3 meters). )
However, since the total burial depth required for reinforcement is generally longer than this, every time one steel pipe is buried, a new steel pipe is sequentially joined to its rear end and drilling is repeated. Due to this, a plurality of steel pipes are buried together.

By the way, in the conventional steel pipes, mutual joining is performed by screwing a male screw and a female screw provided at the end of the steel pipe. However, when performing this screwing,
Since a new steel pipe must be supported concentrically at the rear end of the preceding steel pipe slightly protruding from the hole and the screw cut-out must be aligned and screwed in, the joining work is extremely difficult and a lot of labor is required. And needed a long time. Then, this invention makes it a subject to make joining of this kind of steel pipe easy.

[0006]

In order to solve the above problems, the present invention has the following constitution. That is, the structure of the joint portion of the steel pipe according to the present invention is such that the joint end portion of one steel pipe is a fitting shaft portion having a small outer diameter over a predetermined length, and the middle portion of the fitting shaft portion has an outer periphery. An annular groove is formed along the other end, and the joining end portion of the other steel pipe is a fitting cylinder portion having an inner diameter with which the fitting shaft portion fits, and the annular groove is formed on the inner surface of the middle portion of the fitting cylinder portion. An annular groove is formed at a position facing each other, and the fitting shaft portion of the one steel pipe is fitted to the fitting tubular portion of the other steel pipe, and each of the annular grooves is overlapped by the fitting. It is characterized by interposing an elastic ring which engages with the annular groove and prevents the fitting shaft portion and the fitting tubular portion from being separated from each other.

If the bottom surface of the annular groove formed on the outer peripheral portion of the fitting shaft portion is provided with an inclined bottom surface where the tip side becomes gradually shallow, the elastic ring is lifted when a force in the direction of removal is applied, Since the engagement with the fitting cylinder portion becomes strong, it is effective in preventing the joining portion from coming off. Further, as the elastic ring, it is preferable to use a steel ring which is notched at one location on the circumference.

Furthermore, the outer peripheral surface of the base of the fitting shaft is
If it is formed as a conical inclined surface with the outer diameter gradually increasing toward the back side, the hoop stress acts on the contact part when the fitting tubular part is fitted, and the frictional force becomes stronger and the steel pipe Provides resistance to free rotation and slipping out.

[0009]

Operation: The fitting shaft portion of one steel pipe to be joined to each other is pushed into the fitting tubular portion of the other steel pipe to join them. In this case, the elastic ring is fitted in advance in the annular groove of the fitting shaft portion. This ring is pressed from the outer peripheral portion by the inner surface of the tubular portion when the shaft portion and the tubular portion are fitted, and the diameter is reduced.
When the shaft portion and the tubular portion are completely fitted to each other and the two annular grooves are overlapped with each other, the shaft portion and the tubular portion are originally expanded in the annular groove and are half-fitted into the both grooves. Therefore, even if a force in the pull-out direction acts on the shaft portion and the tubular portion, the ends of both annular grooves engage with this ring and the separation of the two is prevented.

[0010]

Embodiments of the present invention will be specifically described below. In the figure, 1 and 2 represent steel pipes to be joined to each other. A fitting shaft portion 3 is formed at the rear end of one steel pipe 1, and a fitting cylinder portion 4 is formed at the front end of the other steel pipe 2.

The fitting shaft portion 3 has a diameter smaller than the outer diameter of the main body portion 1a of the steel pipe, and a step portion 5 is formed at the base portion thereof, and the front side of the step portion is the back side, that is, the step. A conical inclined surface 6 whose outer diameter gradually increases toward the portion side is formed by a distance m (m = 8 to 12 mm). Slope 6
The inclination angle α of tan α is about 1/100.

An annular groove 10 is formed in the middle of the fitting shaft portion 3 over the entire circumference. The bottom surface of the annular groove 10 is composed of a flat surface portion 10a that is parallel to the axial direction, and an inclined surface portion 10b that is located on the front side of the annular groove 10 and that is gradually shallower on the front side. The inclination angle β of the inclined surface portion is tan β = 1/4
It is a degree. Both ends of the annular groove are end faces 10 perpendicular to the axial direction.
c and 10d.

The fitting tubular portion 4 has an inner diameter larger than the inner diameter of the main body portion 2a of the steel pipe 2, and a step portion 15 is formed at the base of the fitting portion. Trumpet-like inclined surface 16 whose inner diameter on the side of the portion 15 gradually decreases
It has become. The length of the inclined surface 16 is substantially the same as the length m of the inclined surface 6 of the fitting shaft portion, and the inclination angle thereof is also the same.

An annular groove 20 is formed on the entire inner circumference of the middle portion of the fitting cylinder portion 4. The bottom surface of the annular groove 20 is formed as an inclined surface 20b whose front side, that is, the opening side, is gradually deepened. The length of the inclined surface portion is almost the same as the width of the elastic ring described later, and the inclination angle γ is tan.
γ is about 1/10. The front end of the annular groove 20 is an end face 20c that is perpendicular to the axial direction.

An elastic ring 30 is fitted in the annular groove. As shown in FIG. 5, the elastic ring 30 is a circular steel ring in which a part 31 on the circumference is cut by a length k (several mm). The width w of the elastic ring is slightly (about 1 mm) longer than the length of the flat surface portion 10a of the annular groove 10, and the cross section thereof is a substantially wedge shape in which the inner surface is flat and the outer surface is formed as the inclined surface 30a. The wall thickness of the end face portion that abuts the end face 10c is slightly smaller than the depth of the annular groove 10 (0.2 to 0.3).
mm) large.

At the time of joining the steel pipes 1 and 2 having this joining portion, the elastic ring 30 is fitted into the annular groove 10 of the fitting shaft portion 3 of one steel pipe 1 and the other steel pipe 2 is fitted from the outside thereof. The fitting tubular portion 4 is fitted (see FIG. 1). At this time, since the inclined outer surface 30a of the elastic ring 30 is pressed by the inner surface of the fitting tubular portion and the diameter gradually decreases, the fitting tubular portion can be pushed in by a force that resists the frictional force of the contact portion (FIG. 2).

FIG. 3 shows a state in which the fitting of the both is completed. The tip end surface of the fitting tubular portion 4 abuts on the step end surface 5 (the body abutting surface) of the root portion of the fitting shaft portion 3, and the fitting is completed. The end portion of the mating shaft portion 3 abuts on the step end surface 15 of the base portion of the fitting tubular portion 4. In this state, the two annular grooves 10 and 20 are overlapped with each other to form one space 25, in which the elastic ring 30 is held in an expanded state.

In this state, the inner surface of the distal end portion of the fitting tubular portion 4 rides on the inclined surface 6 of the fitting shaft portion 3, so that a strip-shaped hoop stress acts on the opening portion of the fitting tubular portion. Also, the fitting shaft 3
The tip end of is compressed from the outer peripheral portion by the inclined surface 16 of the fitting tubular portion 4, and the hoop stress also acts on this portion. For this reason, the two are in close contact with each other, and separation of the joint and mutual free rotation are prevented. However, in some cases, such inclined surfaces 6 and 16 may not be provided. Since the steel pipe on the rear side is pressed against the steel pipe on the front side by the thrust of the rock drill during the drilling, no force in the detaching direction acts on the joint.

Next, when a force (tension) in the separating direction acts on this joint portion when pulling out the drill rod, the steel pipe 2 moves away from the steel pipe 1, but at this time, the tubular portion 4 Since the end surface 20c of the annular groove hooks the elastic ring 30 and moves rearward, the elastic ring 30 rides on the inclined surface 10b of the annular groove of the shaft portion to expand its diameter, and the degree of engagement between the tubular portion 4 and the elastic ring 30. Becomes deeper, and the end of the elastic ring 30 comes into contact with the end surface 10d of the annular groove 10 (see FIG. 4). For this reason, the steel pipe cannot be further pulled out, and the joint between the steel pipes is firmly maintained.

The structure of this joint is such that, by simply fitting the fitting shaft portion of one steel pipe to the fitting tubular portion of the other steel pipe, the two are firmly joined together, so that the joining work at a work site or the like is possible. Is easy. In the above description, the fitting shaft portion 3 of the preceding steel pipe 1 is fitted into the fitting tubular portion 4 of the succeeding steel pipe 2. However, conversely, the fitting tubular portion of the preceding steel pipe is fitted. The fitting shaft portion of the subsequent steel pipe may be fitted to. Also, if a fitting shaft is formed at one end of one steel pipe and a fitting cylinder is formed at the other end, steel pipes of the same structure can be joined one after another, which is convenient. However, it is also possible to prepare a steel pipe having fitting shaft portions formed at both ends and a steel pipe having fitting tubular portions formed at both ends, and to join these alternately.

[0021]

As described above, according to the structure of the joint portion of the steel pipes according to the present invention, it is extremely easy to join the steel pipes together, and it is suitable for civil engineering sites. Needless to say, this structure can be applied to joining pipes other than the steel pipe for burying.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing the fitting process.

FIG. 3 is a vertical cross-sectional view in a joined state.

FIG. 4 is an explanatory diagram when a pulling force is applied.

FIG. 5 is an explanatory diagram of an elastic ring.

FIG. 6 is an explanatory diagram of a steel pipe burying method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel pipe 2 Steel pipe 3 Fitting shaft part 4 Fitting cylinder part 5 Step part 6 Inclined surface 10 Annular groove 20 Annular groove 30 Elastic ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshikazu Mikami 3-35-23, Kumizawa, Totsuka-ku, Yokohama-shi, Kanagawa (72) Inventor Noboru Takano 1-16-21 Hinode, Kawasaki-ku, Kawasaki-shi, Kanagawa Togane Industrial Co., Ltd. In the company

Claims (4)

[Claims] 1. A joining end portion of one of the steel pipes is used as a fitting shaft portion having a small outer diameter over a predetermined length, and an annular groove is formed along the outer periphery in the middle portion of the fitting shaft portion, The joining end portion of the steel pipe is a fitting cylinder portion having an inner diameter with which the fitting shaft portion fits, and an annular groove is formed on the inner surface of the intermediate portion of the fitting cylinder portion at a position facing the annular groove. Then, the fitting shaft portion of one of the steel pipes is fitted into the fitting tubular portion of the other steel pipe, and the fitting is performed by engaging the respective annular grooves inside the annular grooves overlapped by the fitting. A structure of a joint portion of a steel pipe, characterized in that an elastic ring for preventing the shaft portion and the fitting tubular portion from being separated is interposed. 2. The structure of the joint portion of the steel pipe according to claim 1, wherein the annular groove formed on the outer peripheral portion of the fitting shaft portion has an inclined bottom surface where the tip side becomes gradually shallower. 3. The structure of the joint portion of the steel pipe according to claim 1 or 2, wherein the elastic ring is a steel ring in which one portion on the circumference is cut out. 4. The outer peripheral surface of the base portion of the fitting shaft portion is formed as a conical inclined surface whose outer diameter gradually increases toward the rear side, and the inner peripheral surface of the tip end portion of the fitting tubular portion is a tip end. The structure of the joint portion of the steel pipe according to any one of claims 1, 2, and 3, which is formed as a funnel-shaped inclined surface whose inner diameter gradually increases toward the side.