JP5262684B2 - Double pipe for burial and pipeline having the double pipe for burial - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an underground double-walled pipe having excellent deformation capacity, which is not buckled even by a large bending stress without causing excess increase in cost. <P>SOLUTION: The underground double-walled pipe includes a metal made outer pipe 1, a metal made inner pipe 3 inserted into the inside of the outer pipe 1, and a filling material 5 consisting of a particle and/or particulate filling a gap between the inner pipe 3 and the outer pipe 1. When load is applied to the outer pipe 1, the inner pipe 3 and the filling material 5, and the filling material 5 and the outer pipe 1 are held in contact with each other, so that the filling material 5 successively and smoothly reallocates the stress transfer between the outer pipe 1 and the inner pipe 3. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a double pipe for burying used in the ground like a gas pipeline, for example, and a pipeline using the double pipe for burying.

  For example, a large bending stress acts on the gas pipeline buried in the permafrost land zone at the permafrost boundary. Therefore, in order to realize the stable supply of natural gas from the permafrost land zone, it is necessary that the gas pipeline for transporting natural gas can withstand a large bending stress acting on the permafrost boundary.

For pipelines that may be subjected to a large bending stress, such as gas pipelines embedded in such permafrost land zones, there are two main methods to be able to withstand bending stress. Can be considered. One is a method of improving the deformation performance of the pipeline by inserting a flexible tube having a special mechanical mechanism in the middle of the pipeline (see, for example, Patent Document 1), and the other is a result of the deformation. This is to increase the strength and thickness of the steel pipe material to resist the stress level.
The former method tries to satisfy the deformation performance by a mechanical special mechanism, and the latter method tries to counter the force with a high-strength / thick material.

JP 2005-171893 A

  However, in the case of a method of inserting a flexible tube having a special mechanical mechanism, in addition to the cost of the flexible tube, it is technical standard to use it in a buried part of a pipeline that transports gas or oil at high pressure. Therefore, there is a problem that it is difficult to obtain permission and approval, and it is difficult to say that the airtightness under high pressure is sufficient, and there is a risk of gas leakage.

  In addition, in the method of increasing the strength and thickness of the steel pipe material, when using conventional materials, the range of the elastic modulus is limited, and the strength and thickness of the steel pipe material are increased against a large bending stress. There is a limit to the deformation performance that can be absorbed by fleshing. Furthermore, in the case of a normal single pipe, the fracture mode for bending deformation is local buckling due to cross-section “collapse”, so even if the cross-sectional thickness is increased, the bending rigidity and bending strength are improved. However, the fracture mode of losing resistance to bending due to local instability does not change, and it cannot be said that the material properties of the entire member can be effectively utilized.

  The present invention has been made in order to solve the problems, and an object thereof is to obtain a buried double pipe that is excellent in deformation performance without costly excessively buckling even against a large bending stress. It is said.

A pipe subjected to bending becomes difficult to maintain its cross-sectional shape due to an increase in the degree of stress accompanying deformation, and eventually the cross-section “crushed” (Brazier effect) occurs and the resistance to bending is rapidly lost.
Such a fracture mode is caused by an unstable phenomenon that occurs locally, and has a characteristic that bending strain concentrates only on a portion where the collapse occurs.

  Therefore, the inventor has a double-pipe structure for the pipe, and a filling material is filled between the outer pipe and the inner pipe, so that local concentration of bending deformation is prevented. We considered that it can be dispersed and leveled, and that the mechanical properties of the filling material have a significant effect on the performance of the entire structure.

FIG. 3 is an explanatory view for explaining the process of this study. In each of FIGS. 3A to 3C, a tube axis direction cross-sectional view and a tube axis orthogonal direction cross-section of the double tube are respectively shown. .
3A shows an example of a double pipe in which a gap between the outer pipe 1 and the inner pipe 3 is filled with mortar as the filling material 5, and FIG. 3B shows a gap between the outer pipe 1 and the inner pipe 3. 3 shows an example of a double pipe filled with sand as the filling material 5, and FIG. 3C shows an example of a double pipe filled with fluid as the filling material 5 in the gap between the outer tube 1 and the inner tube 3. ing.

If the double pipe is constructed using a material that adheres to the outer pipe 1 and the inner pipe 3 as mortar and can be regarded as a continuous elastic body, bend the both ends of the double pipe. When a moment is applied, the composite cross section of the double pipe behaves integrally with the inner and outer pipes and the filling material 5, and has a large bending rigidity (see FIG. 3A).
However, since the tensile strength of mortar is low, cracks are likely to occur in the mortar part as the deformation progresses. When cracks occur, local bending rigidity decreases, and the stress distribution concentrates the bending deformation in that part. It can be considered that buckling will occur.

  On the other hand, when fluid is filled as the filling material 5, the outer tube 1 and the inner tube 3 behave separately, and the external force basically bears the stress only in the outer tube (FIG. 3 ( c)).

  Therefore, the inventor made an attempt to fill the filling material 5 with a powder and / or a granular material having properties different from those of the continuous elastic body and fluid, as shown in FIG. The double pipe can exhibit an intermediate characteristic between the case where an elastic body is used as the filling material 5 and the case where a fluid is used, local concentration of bending deformation is prevented, and a change in curvature due to bending is applied to the entire member. The knowledge that it can be distributed and leveled was obtained. By doing so, the toughness of the steel material can be effectively and effectively utilized throughout the double pipe, and can cope with large bending deformations. As a result, the double pipe has excellent bending characteristics and is resistant to buckling. It was found that can be realized.

  In addition, the time from the deformation of the double pipe to the convergence of the deformation of the inner and outer pipes depends on the stress redistribution process of the filling material. The extent to which the effect of such delayed deformation can be expected will depend on future research, but when subjected to a relatively gentle deformation action, such as a gas pipeline buried in a permafrost zone, by ensuring appropriate plasticity, The knowledge that it may lead to the suppression of the maximum stress acting on the pipe was also obtained.

  Furthermore, when filling powder and / or granules as filling material, it is possible to meet a wide range of requirements regardless of rigidity by changing the properties (density, particle size distribution, or shape) of the powder and / or granules to be filled. We obtained knowledge that it would be possible to easily realize the performance.

  The present invention has been made based on various new findings as described above, and specifically has the following configuration.

(1) Moreover, the double pipe for embedding according to the present invention includes a metal outer pipe, a metal inner pipe inserted inside the outer pipe, and a gap between the inner pipe and the outer pipe. A filling material comprising powder and / or granules filled, and when a load is applied to the outer tube, the filling material does not resist tensile stress, Displacement occurs between the constituent particles, and the inner packing material redistributes the stress transmission between the outer tube and the inner tube continuously and smoothly, so that the curvature of the inner tube becomes the curvature of the outer tube. On the other hand, the inner tube and the inner filling material and the inner filling material and the outer tube are kept in contact with each other.

(2) Further, in the above (1), the filling material is any one of sand, ceramic particles, ceramic powder, or a mixture thereof.

(3) A pipeline according to the present invention is characterized in that the buried double pipe according to the above (1) or (2) is joined to at least a part thereof.

  The buried double pipe according to the present invention includes a metal outer pipe, a metal inner pipe inserted inside the outer pipe, and a powder filled in a gap between the inner pipe and the outer pipe. And / or an inner filling material made of granular material, and when a load is applied to the outer tube, the inner tube and the inner filling material and the contact between the inner filling material and the outer tube are maintained. The inner filling material is configured to continuously and smoothly redistribute the stress transmission between the outer tube and the inner tube, so that local concentration of bending deformation is prevented, and a change in curvature due to bending is prevented in the entire member. This makes it possible to effectively and effectively utilize the toughness of the steel material throughout the entire material, and to cope with large bending deformations. As a result, it has excellent bending characteristics and is resistant to buckling. A pipe can be realized.

[Embodiment 1]
FIG. 1 is an explanatory view of an embedded double pipe excellent in deformation performance according to an embodiment of the present invention, FIG. 1 (a) is a side view, and FIG. 1 (b) is a cross-sectional view perpendicular to the pipe axis. . The buried double pipe 10 according to the present embodiment includes an outer pipe 1 made of a steel pipe, an inner pipe 3 made of a steel pipe inserted inside the outer pipe 1, and a gap between the inner pipe 3 and the outer pipe 1. Is filled with a filling material 5 made of powder and / or granular material.

The filling material 5 has small adhesion to the inner and outer tubes and has resistance to compressive stress, but does not resist tensile stress and is not a continuous body, and has such performance. , Granular materials having an appropriate particle size, such as sand and ceramic granular materials.
Further, as an example of the gap between the outer tube 1 and the inner tube 3, for example, when the inner tube 3 is a tube of about 300 mm to 600 mm, it is about 50 mm to 100 mm.

FIG. 2 is an explanatory view for explaining the behavior when a bending moment is applied to both ends of the embedded double pipe 10 according to the present embodiment. FIG. 2 (a) is a sectional view along the pipe axis direction. (B) is a pipe axis orthogonal direction sectional view.
When a bending moment is applied to both ends of the double tube 10 for burying, the granular material or powdery material that is the filling material 5 is displaced between the particles constituting the filling material 5 without resisting tensile stress. And a smooth and continuous stress redistribution. This is shown in FIG. 2 that the curvature of the inner tube 3 is smaller than the curvature of the outer tube 1.
As a result of continuous stress redistribution as described above, there is no occurrence of local bending rigidity degradation due to cracking of the mortar as in the case of filling the mortar described above, and the double The toughness of the steel material can be effectively and effectively utilized throughout the pipe, and can cope with large bending deformation, resulting in a buried double pipe with excellent bending characteristics and strong buckling.

  Note that the buried double pipe 10 configured as described above can be used for the entire pipeline, but considering the cost, it is only at the permafrost boundary in the permafrost zone as described above. It is preferable to use it. That is, it can be set as the pipeline provided with the double pipe 10 for embedding concerning this Embodiment in at least one part of a pipeline.

Moreover, although the construction method of the double pipe 10 for embedding concerning this Embodiment is not specifically limited, For example, it is as follows.
An inner tube 3 that is slightly longer than the outer tube 1 is inserted into the outer tube 1 having a predetermined length (eg, 12 m). An insulator is installed in the inner tube 3 so that a predetermined gap can be maintained between the inner tube 3 and the inner surface of the outer tube 1. Then, the filling material 5 is filled between the outer tube 1 and the inner tube 3. A plurality of such double pipes are formed, and the ends of the outer pipe 1 and the inner pipe 3 constituting the plurality of double pipes are joined by welding, for example.
In the above description, the outer tube 1 and the inner tube 3 of a predetermined length are filled with the filling material 5 to form a double tube containing the filling material of a predetermined length, Although the example which joins the double pipes with a filling material was shown, after joining two or more double pipes which inserted the inner pipe 3 in the outer pipe 1 of predetermined length, it is filled with the inside filling material. Also good.

It is explanatory drawing of the double pipe for embedment concerning one embodiment of the present invention. It is explanatory drawing explaining the behavior of the double pipe for embedding concerning one embodiment of the present invention. It is explanatory drawing explaining the effect | action of this invention.

Explanation of symbols

1 Outer tube 3 Inner tube 5 Filling material 10 Buried double tube

Claims (3)

A metal outer tube, a metal inner tube inserted inside the outer tube, and a filling material made of powder and / or granules filled in a gap between the inner tube and the outer tube; When the load is applied to the outer tube, the filling material is displaced between the particles constituting the filling material without resisting tensile stress, and the filling material is The inner tube and the inner tube are deformed so that the curvature of the inner tube becomes smaller than the curvature of the outer tube by continuously and smoothly redistributing stress transmission between the outer tube and the inner tube. An embedding double pipe characterized in that the inner filling material and the contact between the inner filling material and the outer pipe are maintained.   2. The double pipe for embedding according to claim 1, wherein the filling material is any one of sand, ceramic particles, ceramic powder, or a mixture thereof. A pipeline comprising the double pipe for burying according to claim 1 or 2 joined to at least a part thereof.

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