JP7432926B2 - Steel pipe connection structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a connection structure for steel pipes used for reinforcing ground in tunnel construction and the like.

For example, in tunnel construction, the NATM (New Austrian Tunneling Method) method is used, in which multiple steel pipes are driven into the peripheral wall of the tunnel at predetermined intervals using a drilling device, in order to reinforce the ground around the wall of the excavated tunnel. Are known. In this NATM construction method, after driving the steel pipe, a hardening agent is injected into the ground through the steel pipe as necessary to strengthen the soft ground. The steel pipes used in this construction method are about 3 meters long and have an outer diameter of about 10 centimeters, but the length required to reinforce the ground is longer than 3 meters, so each time a steel pipe is driven, , connect a new steel pipe to the rear end, and repeat the process of driving it in again.

Conventionally, when connecting steel pipes, one steel pipe has a male thread formed on its outer circumferential surface, and the other steel pipe has a female thread formed on its inner circumferential surface, and these male and female threads are screwed together to connect the steel pipes. The mainstream is a structure that connects the two (see Patent Document 1 and Patent Document 2). However, in this case, it is necessary to align the axes of the two steel pipes and screw in at least the other steel pipe while rotating the entirety thereof. Therefore, labor for alignment and screwing is required, which places a heavy burden on the operator.

In addition, an annular groove is formed on the outer circumferential surface of the end of one steel pipe, and an annular groove is formed on the inner circumferential surface of the end of the other steel pipe, which engages with each annular groove to prevent the steel pipes from separating from each other. A structure of a joint portion of steel pipes in which an elastic ring is interposed has been proposed (see Patent Document 3). According to this structure, it is only necessary to move the other steel pipe in the axial direction and push it in, so the work of connecting the steel pipes is relatively easy.

In the device disclosed in Patent Document 3, a rock drill for driving a steel pipe into the ground passes a rod with a drilling tool called a bit attached to the tip in the axial direction inside the steel pipe, and inserts the bit from the tip of the steel pipe. It has a structure that applies striking force and propulsion force to the rod when it is protruded. At this time, in order to advance the steel pipe together with the rod, a device is used that advances the steel pipe while pushing the rear end of the rod and the rear end of the steel pipe. Therefore, the rear steel pipe is pressed against the front steel pipe by the jackhammer, and no force in the direction of separation is applied to the joint of the steel pipe, preventing the joint of the steel pipe from coming off during driving into the ground. I'm here.

Incidentally, in recent years, as a rock drilling machine, as shown in Patent Document 2, a device in which a bit is attached near the tip of a steel pipe to drill a hole has been used. In the case of this rock drill, the second and subsequent steel pipes (intermediate pipes) advance while being pulled by the first steel pipe (leading pipe), so a force acts on the joints of the steel pipes in the direction of separating them. .

If such a device that drills holes while pulling the steel pipe is applied to the structure shown in Patent Document 3, there is a possibility that sufficient strength cannot be ensured at the joint of the steel pipe.

Japanese Patent Application Publication No. 2004-332242 JP2019-203362A Japanese Patent Application Publication No. 9-42239

An object of the embodiments of the present invention is to provide a steel pipe connection structure in which the steel pipe connection work is easy and the steel pipe connection strength is high.

The steel pipe connection structure of this embodiment is a steel pipe connection structure in which a plurality of axially adjacent steel pipes are connected by inserting one steel pipe into the other steel pipe, and the connection end of the one steel pipe an elastic ring at least partially protruding from the outer periphery of the connecting end provided on the outer periphery of the connecting end; a male threaded portion formed on the outer periphery of the connecting end; , an annular recess facing the elastic ring and a female thread formed on the inner periphery of the connection end and facing the male thread, the male thread in the one steel pipe and the female thread in the other steel pipe. The elastic ring is characterized in that the elastic ring engages with the annular recess at the end of the threaded engagement.

According to the embodiments of the present invention, it is possible to provide a steel pipe connection structure in which the work of connecting steel pipes is easy and the steel pipe connection strength is high.

1 is a cross-sectional view showing a steel pipe connection structure according to an embodiment of the present invention. It is a sectional view of the important part showing the state where steel pipes are connected in the connection structure of the same steel pipe. It is a front view showing the elastic ring in the connection structure of the same steel pipe. It is a sectional view of the important part for explaining the connection process of steel pipes in the same steel pipe connection structure. It is a graph which shows the tensile strength in the connection part of steel pipes in the same steel pipe connection structure. It is a graph which shows the tensile strength in the connection part of steel pipes in the same steel pipe connection structure.

Hereinafter, a steel pipe connection structure according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6. The steel pipe connection structure of this embodiment is used for reinforcing the ground in tunnel construction, etc., and one steel pipe (for example, the leading pipe) is inserted into the other steel pipe (for example, the middle pipe), and the shaft This method is applied when a plurality of steel pipes that are adjacent to each other in a direction are connected continuously and cast into the ground. Specifically, the plurality of steel pipes are referred to as a steel pipe with a bit attached to the tip, a leading pipe, a plurality of steel pipes connected to this leading pipe as an intermediate pipe, and a steel pipe connected to the intermediate pipe at the end as a terminal pipe. It is called.

FIG. 1 is a cross-sectional view showing connected steel pipes, FIG. 2 is a cross-sectional view of main parts showing a state in which the steel pipes are connected, and FIG. 3 is a front view showing an elastic ring. Moreover, FIG. 4 is a cross-sectional view of a main part for explaining the process of connecting steel pipes, and FIGS. 5 and 6 are graphs showing the tensile strength and bending strength at the joint between steel pipes. Note that in each figure, the same parts are given the same reference numerals, and redundant explanations will be omitted. Furthermore, for the sake of explanation, the direction in which the steel pipe advances with respect to the ground will be referred to as the leading end side, and the opposite side will be referred to as the rear end side.

As shown in FIGS. 1 to 3, the steel pipe connection structure includes a leading pipe 1 as one steel pipe and an intermediate pipe 2 as the other steel pipe that are connected to each other.

The leading pipe 1 is formed into a cylindrical shape from a general structural carbon steel pipe (STK400), and has a bit mounting part Bm on the front end side and a connecting end part 11 on the rear end side. The bit mounting portion Bm has a thread formed on its inner circumferential surface so that a bit can be mounted thereon.

The connecting end 11 is an insertion part, and the connecting end 11 is formed with a circumferentially annular mounting groove 12 on the outer circumferential surface and a male threaded part 13 as a threaded part. The male threaded portion 13 is formed on the rear end side of the connecting end portion 11, and the mounting groove 12 is formed at a position closer to the tip side at a predetermined distance from the male threaded portion 13.

The mounting groove 12 is a portion where an elastic ring 14, which will be described later, is provided, and an inclined surface 12a whose depth gradually becomes shallower toward the rear end is formed on the bottom surface of the mounting groove 12. Therefore, the elastic ring 14 is spaced apart from the male threaded portion 13 in the axial direction.

The male threaded portion 13 has one thread, and is preferably a trapezoidal thread or a square thread. In other words, the thread 13a is formed on the outer peripheral surface of the connecting end 11 so as to go around the outer peripheral surface once.

An elastic ring 14 is fitted into the mounting groove 12 . Therefore, the male threaded portion 13 is formed at the end of the leading tube 1 in the axial direction, and the elastic ring 14 is spaced apart from the male threaded portion 13 in the axial direction.

The elastic ring 14 is in the shape of a steel ring having a notch 14a in which a part of the circumference is cut out, and its axial cross-sectional shape is approximately wedge-shaped. The side circumferential surface perpendicular to the contact surface 14b is the contact surface 14b.

Further, when the elastic ring 14 is fitted into the mounting groove 12 and arranged, the outer diameter of the elastic ring 14 is larger than the outer diameter of the connecting end 11 . Therefore, a part of the outer periphery of the contact surface 14b projects from the mounting groove 12 onto the outer periphery of the connecting end 11. Note that the material of the elastic ring 14 is desirably harder than the material of the steel pipe.

Like the leading pipe 1, the intermediate pipe 2 is formed into a cylindrical shape from a general structural carbon steel pipe (STK400), and has a connecting end 21 on the front end side, and the rear end side is connected to the aforementioned leading pipe. It has the same configuration as the connection end portion 11 of No. 1. Therefore, the connection end 11' on the rear end side is formed with a mounting groove 12', a male threaded part 13', and is provided with an elastic ring 14', and a detailed explanation thereof will be omitted.

The connecting end portion 21 is a socket portion, is constituted by a separate member from the main body portion of the intermediate tube 2, and is fixed to the outer periphery of the main body portion by screwing or welding. The inner diameter of the connecting end 21 is larger than the outer diameter of the connecting end 11 of the leading pipe 1, so that the connecting end 11 of the leading pipe 1 can be inserted into the connecting end 21 of the intermediate pipe 2. . Further, the outer diameter of the connecting end portion 21 is larger than the outer diameter of the main body portion.

The connecting end portion 21 is formed with a circumferentially annular recess 22 on the inner circumferential surface and a female threaded portion 23 as a threaded portion. The annular recess 22 is formed at the distal end of the connecting end 22, and the female thread 23 is formed at a position closer to the rear end at a predetermined distance from the annular recess 22. That is, when the connecting end 11 of the leading tube 1 is inserted into the connecting end 21 of the intermediate tube 2 and the intermediate tube 2 is connected to the leading tube 1, the elastic ring 14 provided on the leading tube 1 and the intermediate tube The annular recess 22 formed in the top tube 2 faces each other, and the male threaded part 13 formed in the leading pipe 1 and the female threaded part 23 formed in the intermediate pipe 2 face each other.

The annular recess 22 is a part that the elastic ring 14 engages with, and has an inclined surface that follows the wedge-shaped shape of the elastic ring 14, and has a side peripheral surface perpendicular to the axial direction on the tip side as an abutment surface. 22a.

The female threaded portion 23 is a portion that is screwed into the male threaded portion 13 formed on the top pipe 1, and has one thread like the male threaded portion 13, and has an inner thread on the inner circumferential surface of the connection end 21. A thread 23a is formed so as to go around the circumferential surface once.

Next, the process of connecting steel pipes will be explained with reference to FIG. Fig. 4(a) shows the initial state of the steel pipe connection, Fig. 4(b) shows the intermediate state of the steel pipe connection, and Fig. 4(c) shows the same state as Fig. 2. Indicates completion status.

In FIG. 4(a), as shown with reference to FIG. 1, in order to insert the leading tube 1 into the intermediate tube 2, the connecting end 21 of the intermediate tube 2 is connected to the connecting end 11 of the leading tube 1. Align and fit so that the shaft centers are aligned in the connection direction (tip side).

Next, as shown in FIG. 4(b), the intermediate tube 2 is rotated to screw the female threaded portion 23 into the male threaded portion 13 of the top tube 1. This state is, for example, a state in which the intermediate tube 2 is rotated half a turn and screwed into the threaded portion, and depending on the screwing, the connecting end 21 of the intermediate tube 2, that is, the annular recess 22, It advances in the connecting direction with respect to the connecting end 11 of the leading pipe 1. Further, the inner circumferential surface of the tip of the connecting end 21 advances while pressing the outer circumferential surface of the elastic ring 14. In this case, since the elastic ring 14 has the notch 14 a, when it receives a pressing force from the tip of the connecting end 21 , the elastic ring 14 contracts slightly in diameter and deforms in the direction of fitting into the mounting groove 12 . Therefore, the abutment surface 14b of the elastic ring 14 comes to sink into the mounting groove 12, and when the threaded portion is further screwed together, the tip of the connecting end 21 climbs over the elastic ring 14 and advances in the connection direction. .

FIG. 4(c) shows a state in which the intermediate tube 2 is rotated once and the screwing of the threaded portions reaches the end point, and the connection is completed. At the end of the threaded engagement, the elastic ring 14 engages with the annular recess 22. In other words, the timing at which the threaded portion reaches the end point of screwing and the timing at which the elastic ring 14 engages with the annular recess 22 occur at the same time.

Specifically, the male threaded portion 13 and the female threaded portion 23 are threaded together in one thread, and by rotating the intermediate tube 2 once, the intermediate tube 2 advances and moves in the connection direction by that amount. In other words, it advances by one pitch. As this progresses, the distal end 15 of the connecting end 11 of the leading tube 1 comes into contact with the step 24 formed on the rear end side of the inner circumferential surface of the connecting end 21 of the intermediate tube 2, thereby preventing the screw connection. It is stopped and reaches the end point of screwing.

Therefore, the tip of the connecting end 21 passes over the elastic ring 14 and reaches the end point of the screw engagement, and the elastic ring 14 engages with the annular recess 22. The elastic ring 14 is released from the pressing force of the tip of the connecting end 21, expands in diameter, and returns to its original state. The contact surface 14b of the elastic ring 14 protrudes onto the outer circumferential surface of the connection end 11 and faces the contact surface 22a in the annular recess 22 of the connection end 21, so that the elastic ring 14 engages with the annular recess 22. I come to do it.

In this state where the steel pipes are connected, when the leading pipe 1 is moved in the direction of the arrow so as to pull the intermediate pipe 2, the contact surface 14b of the elastic ring 14 contacts the contact surface 22a of the annular recess 22. It becomes a contact state.

Furthermore, the mounting groove 12 is formed with an inclined surface 12a. Therefore, as the leading tube 1 moves, a force is applied in a direction that presses the elastic ring 14 against the inclined surface 12a. In this case, the elastic ring 14 moves upward (in the direction of protruding from the outer peripheral surface of the connecting end 11) along the inclined surface 12a, and the contact surface 14b of the elastic ring 14 moves from the mounting groove 12 to the outer peripheral surface of the connecting end 11. It further protrudes onto the surface, and the contact area of the annular recess 22 with the contact surface 22a increases. Therefore, the connection between the leading pipe 1 and the intermediate pipe 2 can be strengthened.

On the other hand, in the threaded portions of the male threaded portion 13 and the female threaded portion 23, the side surfaces 13f and 23f of the threads due to their meshing, that is, the respective flank surfaces of the male threaded portion 13 and the female threaded portion 23 are brought into contact.

Therefore, the engagement of the elastic ring 14 with the annular recess 22 and the abutting state of both the male threaded portion 13 and the female threaded portion 23 can simultaneously receive a tensile load, thereby dispersing the stress and connecting. It becomes possible to obtain a steel pipe connection structure with high strength.

In addition, the male threaded portion 13 and the female threaded portion 23 are threaded in a single thread, and the threaded threading is completed by rotating the intermediate tube 2 once, so the number of rotations for threading is small, making the work easier and improving productivity. can do. The number of threads on the male threaded portion 13 and the female threaded portion 23 is preferably 2 or less, and preferably in the range of 1 to 2 in order to reduce the number of rotations during screwing.

The steel pipe connection structure of this embodiment can receive tensile loads both by the engagement of the elastic ring 14 with the annular recess 22 and by the threaded engagement of the male threaded part 13 and the female threaded part 23. Even if the number of threads is reduced, it is possible to increase the tensile strength. In other words, the number of threads on the threaded portion can be reduced, the number of rotations for screwing can be reduced, and the labor of the operator can be reduced.

Next, an outline of the procedure for driving steel pipes into the ground will be explained.

First, a rock drill bit is attached to the bit attachment part Bm on the tip side of the top tube 1, a rod is inserted into the top tube 1, and the tip of the rod is connected to the bit. The rear end of the rod is connected to the drifter of the rock jackhammer, and the rod is pushed forward while applying a striking force to the rod from the drifter of the rock jackhammer. Thereby, it is possible to simultaneously drill a hole in the ground and insert the leading pipe 1 into the drilled hole.

With the leading pipe 1 substantially driven into the ground, the axis of the connecting end 21 of the intermediate pipe 2 is aligned with the connecting end 11 on the rear end side of the leading pipe 1 protruding from the ground. Then, when the intermediate tube 2 is moved in the axial direction, the connecting end 21 is fitted to the connecting end 11 of the leading tube 1, and the intermediate tube 2 is screwed, the leading tube 1 and the intermediate tube 2 are connected to each other by the threaded portion. The connection is made by the engagement of the elastic ring 14 into the annular recess 22.

Insert the rod into the intermediate pipe 2, connect it with the rod inserted into the leading pipe 1, and push the rod forward again while applying impact force to the rod with the drifter to drill into the ground and at the same time drill the intermediate pipe 2. Drive it into the inside of the drilled hole.

At this time, the intermediate tube 2 is pulled by the leading tube 1 and advances through the drilled hole, so a force is applied to the connecting portion in a direction that pulls the intermediate tube 2 apart, but the steel tube of this embodiment According to this connection structure, the tensile strength is high, so that the connection structure will not come off. By repeating this operation, the required number of steel pipes can be sequentially driven into the ground.

Next, the results of measuring the tensile strength and bending strength of the steel pipe connection structure of this embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 shows the measurement results of tensile strength, where the horizontal axis shows the data number and the vertical axis shows the tensile load. FIG. 6 shows the measurement results of bending strength, where the horizontal axis shows the data number and the vertical axis shows the bending load. Both tensile strength and bending strength were measured using an Amsler type universal material testing machine AU-500 manufactured by Tokyo Hoshiki Seisakusho Co., Ltd.

As measurement samples, we prepared a connection structure according to the present embodiment, a comparison example 1 in which the connection structure is formed by screw engagement, and a comparison example 2 in which the connection structure is formed by engagement between an elastic ring and the annular recess 22. did. Note that Comparative Example 1 is a normal threaded joint, and in order to connect it, the operator needs to manually turn the steel pipe body 14 to 15 times, which is a heavy burden.

As shown in FIG. 5, in the tensile strength measurement, results were obtained in this embodiment that the connected state could be maintained up to about 430 kN. On the other hand, in Comparative Example 1, the tensile strength was about 340 kN, and in Comparative Example 2, it was about 120 kN, which confirms that the tensile strength of this embodiment is large.

Furthermore, as shown in FIG. 6, in the measurement of bending strength, results were obtained in which the connected state could be maintained up to about 65 kN in this embodiment. On the other hand, in Comparative Example 1, the bending strength was about 48 kN, and in Comparative Example 2, it was about 25 kN, which confirms that the bending strength of this embodiment is large.

Incidentally, the reason why the connection structure according to the present embodiment has a high bending strength is mainly because the socket portion as the connection end portion 21 is made of a separate member from the main body portion of the intermediate tube 2. This is due to the fact that the outer diameter is larger than that of the main body.

As described above, according to the present embodiment, it is possible to provide a steel pipe connection structure in which the work of connecting steel pipes is easy and the steel pipe connection strength is high. Specifically, the tensile load can be simultaneously applied by both the engagement of the elastic ring 14 with the annular recess 22 and the threaded engagement of the male threaded part 13 and the female threaded part 23, thereby dispersing the stress and establishing the connection. It becomes possible to increase the strength. Furthermore, the number of threads on the threaded portion can be reduced, and the number of rotations for screwing in can be reduced, making it possible to reduce the labor of the operator.

In the above embodiment, the connection structure between the leading pipe and the intermediate pipe has been described, but the steel pipe connection structure of this embodiment can also be applied to the connection structure between intermediate pipes or between an intermediate pipe and a terminal pipe. The type of steel pipe is not particularly limited.

In addition to the method of attaching a rock drill bit near the tip of the steel pipe, the present invention can of course be applied to a method of drilling a hole while pushing the rear end of the steel pipe with a rock drill.

The present invention is not limited to the configuration of the embodiments described above, and various modifications can be made without departing from the gist of the invention. Further, the above embodiments are presented as examples, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

1...Top pipe (one steel pipe)
2...Middle pipe (other steel pipe)
11...Connection end 12...Mounting groove 13...Male thread portion 13a...Thread 14...Elastic ring 14a...Notch 14b...Abutment surface 15...Connection of top pipe Tip part 21 of the end... Connection end 22... Annular recess 22a... Contact surface 23... Female threaded part 23a... Thread 24... Connection end inner surface rear end side of intermediate pipe step part

Claims (3)

A steel pipe connection structure that connects a plurality of axially adjacent steel pipes by inserting one steel pipe into the other steel pipe,
an elastic ring provided on the outer periphery of the connecting end of the one steel pipe, at least a portion of which protrudes from the outer periphery of the connecting end, and a male threaded portion formed on the outer periphery of the connecting end;
an annular recess formed on the inner periphery of the connecting end of the other steel pipe and facing the elastic ring; and a female threaded part formed on the inner periphery of the connecting end and facing the male threaded part;
Equipped with
The connecting end of the other steel pipe is constituted by a separate member from the steel pipe main body, and its outer diameter is larger than the outer diameter of the steel pipe main body,
A steel pipe connection structure, characterized in that the elastic ring engages with the annular recess at the end point of the threaded engagement between the male threaded part of the one steel pipe and the female threaded part of the other steel pipe. The steel pipe connection structure according to claim 1, wherein the number of threads of the male thread portion and the female thread portion is in a range of one to two threads. A male threaded portion of the one steel pipe is formed at an axial end of the one steel pipe, and the elastic ring is provided at an interval from the male threaded portion in the axial direction. The steel pipe connection structure according to claim 1 or claim 2.

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