JP2015072025A - Sea-bottom pipeline laying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laying method that can newly lay a sea-bottom pipeline while protecting an existing line directly laid on the sea bottom without needing sea-bottom work of a diver, when the sea-bottom pipeline is newly laid so as to intersect with the exist line.SOLUTION: In a sea-bottom pipeline laying method, supports are previously mounted to pipes arranged at front and back of a portion intersected with a cable and an existing pipeline directly arranged on the sea bottom; a pipeline to which the supports are mounted is delivered from a facility ship for submergence and sinking; and thereby the pipeline is supported by the supports so as to be laid above the existing line.

Description

  The present invention relates to a construction method for laying a pipeline on the seabed, and more particularly to a construction method for newly laying a pipeline across an existing submarine cable or a submarine pipeline.

  Laying the submarine pipeline is a pipe (or pipe) called stinger installed on the laid ship while welding and stretching the short pipes, which are coated with concrete for weight adjustment on the outer surface of the pipe, on the laid ship. A so-called laying ship construction method is adopted in which a ship is launched into the sea through a structure for supporting and guiding the ship, and is then landed on the seabed.

  The pipeline that is being laid from the bottom to the laying vessel by this method is not supported midway in the sea (generally to a depth of about 100 m), so a device (tensioner) that applies tension to prevent excessive deformation is laid. It is installed on the ship. For this reason, it is also called the S-shaped method because the underwater pipeline draws an S-shape.

  Here, a rotating roller (hereinafter referred to as a roller) is installed on the laying ship and the stinger in order to smoothly carry out the launching work of the pipeline.

  On the other hand, as a method for protecting a pipeline laid on the seabed, for example, in Patent Document 1, for the purpose of protecting cables and pipelines laid on the seabed 1 from dredging by the ship 101, the seabed along the laying route is mainly used. A method has been proposed in which the cable or pipeline is installed in the groove 102 excavated in 1 and backfilled, and the upper portion is covered with a grout mat 103 (see FIG. 6).

JP-A-8-269929

  On the other hand, there are cases where cables and pipelines are placed directly on the sea floor without taking such protective measures.

  When newly laying a pipeline across an existing submarine cable or pipeline (hereinafter referred to as an existing line) placed directly in this way, the following measures are usually taken to protect the existing line.

  For example, a method of constructing a mound 113 made of sand 111 and crushed stone 112 on an existing line 7 as shown in FIG. 7 and laying a new pipeline 2 thereon, or made of concrete or steel as shown in FIG. This is a method of protecting the existing line 7 by installing protective structures 121 made of products in front of and behind the intersection of the seabed 1 and laying a pipeline 2 on the seabed 1 to overcome the existing line 7. .

  However, in any of the methods, since the work is usually accompanied by divers on the sea floor, the cost is high, and there is a limit to the water depth at which the divers can work.

  The present invention has been made in order to solve the above-described problem. When a pipeline is newly laid across an existing line placed directly on the seabed, the existing line is not required to be operated by a diver. It is an object of the present invention to provide a laying method capable of newly laying a pipeline while protecting the cable.

  In order to solve the above problems, the present invention has the following features.

  [1] When laying a new submarine pipeline, a support was attached in advance to the existing pipeline directly placed on the seabed and the pipes placed before and after the crossing part of the cable, and the support was attached from the laying ship. A method of laying a submarine pipeline, characterized in that the pipeline is supported by the support so as to surpass an existing line by drawing out and bottoming out the pipeline.

  [2] The submarine pipeline laying method according to [1], wherein the support is rotatable about the pipe, and the center of gravity of the support is on the lower side of the support with respect to the axis of rotation.

  [3] The submarine pipeline according to [2], wherein the bottom end of the support is substantially the same as the height of the lower surface of the coated pipe in a state where the lower side of the support is turned upward. Laying construction method.

  [4] A submarine pipeline support used in the submarine pipeline laying method described in [1] above, wherein the lower end of the support is rotated so that the lower end of the support is turned upward, Submarine pipeline support characterized in that it is approximately the same as the height of the bottom surface and the center of gravity of the support is on the lower side of the support with respect to the center of rotation.

  In the present invention, when laying a new submarine pipeline, supports are attached in advance to the pipes before and after the portion of the seabed that intersects the existing line, and the pipeline with this support is unwound from the laying ship and settling and landing. By making it bottom, it becomes possible to efficiently lay a new submarine pipeline while protecting the existing line without requiring submarine operations by divers.

1 is an overall view of a submarine pipeline laying method according to an embodiment of the present invention. It is explanatory drawing of the cross | intersection part with the existing line which concerns on one Embodiment of this invention. It is explanatory drawing of the support which concerns on one Embodiment of this invention. It is explanatory drawing of the support which concerns on one Embodiment of this invention. It is explanatory drawing of the support which concerns on other embodiment of this invention. It is explanatory drawing of a prior art. It is explanatory drawing of a prior art. It is explanatory drawing of a prior art.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is an overall view showing a situation where a pipeline 2 is laid on the seabed 1 in an embodiment of the present invention. While the pipe 4 is welded and stretched on the laying ship 3, it is launched through a stinger 5 that supports and guides the pipeline 2 near the sea surface 9, and the pipeline 2 is moved to the seabed 1 while the laying ship 3 is gradually advanced. Lay down. On the laying ship 3 and the stinger 5, a roller 6 for smoothly feeding the pipeline 2 is provided. Supports 8 (8 a, 8 b) are attached to the pipeline 2 before and after the portion of the seabed 1 that intersects with the existing line 7, and settles together with the pipeline 2 to land on the seabed 1.

  FIG. 2 is an explanatory diagram showing a situation on the seabed 1 after the installation of the pipeline 2 is completed in one embodiment of the present invention. The pipeline 2 exceeds the existing line 7 (submarine cable or submarine pipeline). The support 8 partially lifts the pipeline 2 from the seabed 1 and places it at two locations on the front and rear sides of the existing line 7, so that the pipeline 2 is located above the existing line 7 due to the rigidity of the pipeline 2. Be laid beyond. Due to this action, the pipeline 2 does not contact the existing line 7 and does not apply any load, that is, does not affect the existing line 7.

  3A and 3B are explanatory views showing the pipeline 2 and the support 8 in more detail. FIG. 3A is a side sectional view, and FIG. 3B is a front view (a view taken along the line AA in FIG. 3A). ).

  The pipe 4 which comprises the pipeline 2 is comprised by the concrete coating 11 which covers the steel pipe 10 and its outer surface. The concrete coating 11 is intended to protect the steel pipe 10 and adjust the weight for sinking the pipeline 2 to the seabed 1.

  The support 8 is composed of a column portion 12 that supports the entire circumference of the outer surface of the steel pipe in a portion of the pipeline 2 that is not coated with concrete, and a leg portion 13 that is connected to the lower side thereof. The movement of the pipeline 2 in the axial direction is restricted.

  In this figure, the support 8 is arranged so as to cover the welded portion 14 where the pipes 4 are joined together by welding, and in this case, after the pipes 4 are joined together by welding on the laying ship 3, they are formed in half. What is necessary is just to join the support | pillar part 12 made | formed by means, such as a volt | bolt or welding. The support 8 is not necessarily arranged at the joint between the pipes 4. For example, after the support 8 is passed through the steel pipe 10 in a factory on the ground, the right and left sides of the support 8 are concrete-coated, so that the support 8 is arranged at a substantially central portion. You may let them. Further, the support 8 is not limited to being disposed on the outer surface of the steel pipe 10, for example, a thin concrete coating is applied to the entire outer periphery of the steel pipe 10, and the support 8 is disposed on the outer side. May be further coated with concrete.

  Next, the support 8 itself will be described in more detail. The support 8 is configured to be symmetrical with respect to the axial direction of the pipe as shown in FIG. 3A, and symmetrical with respect to the front as shown in FIG. 3B. A through hole 15 having an inner diameter slightly larger than the outer diameter of the steel pipe 10 is provided in the support column 12 of the support 8, and the steel pipe 10 passes through the through hole 15. That is, there is a gap between the steel pipe 10 and the through hole 15, and the support 8 is rotatable about the steel pipe 10 due to the existence of this gap. Here, it is not impeded to apply a known technique for smoothly performing the rotation to the sliding surface of the rotation in the present embodiment. That is, for example, it is possible to avoid contact between metals by attaching a resin member to a surface of the pipe 4 side or the support 8 side that comes into contact with the counterpart. However, since the number of times the support 8 rotates around the pipe 4 is extremely small as 1 to 2 at most, an extremely simple structure is often adopted as shown in the present embodiment.

  The size of the upper surface 16 of the support 8 is set so as to be substantially the same height as the upper surface 4a of the pipe 4 coated with the concrete coating 11, and the center of gravity G of the support 8 is lower than the center C of the through hole 15. In position. The material of the support 8 may be made of steel or concrete, for example. Further, a combination of these may be used, that is, the support 8 itself is selected and designed in consideration of the structural strength and durability of the support 8 itself.

  Next, the construction method will be described. FIG. 4 is an explanatory view showing the state of the pipeline 2 and the support 8 on the laid ship, FIG. 4 (a) is a side sectional view, and FIG. 4 (b) is a front view (BB arrow in FIG. 4 (a)). View). On the laying ship 3, the pipeline 2 is placed on a laying ship 3 and a roller 6 fixed on a stinger 5 installed in the laying ship 3. This is to smoothly feed the pipeline 2 from the laid ship 3 into the sea. At this time, the support 8 is installed so that its lower side (the leg 13 side) is turned upward, so that the support 8 is upside down, and the upper surface 16 of the support 8 (this In the state, it is located at the lowermost end) and is substantially the same height as the lower surface 4b of the concrete coating 11 applied to the pipe 4, so that it can pass over the roller 6 without any trouble. Here, the substantially same height is less than the radius of the roller 6 even if the difference in height between the upper surface 16 of the support 8 and the lower surface 4b of the pipe is large, preferably 50% or less of the radius of the roller 6. Indicates 15% or less of the radius of the roller 6.

  In some cases, as the support 8 passes, the roller 6 at a position where interference with the support 8 is predicted is retracted manually or automatically downward or laterally to avoid interference with the support 8. Then, when the support 8 has passed through the position of the roller 6, the roller 6 may be returned to the original position.

  In this example, the top and bottom are reversed by lifting the leg 13 of the support 8 (in this state, which is located above) with the rope 20 by a crane. Inversely, other means capable of maintaining the state are included.

  Next, the support 8 that has passed through the stinger 5 and has reached the sea or the vicinity of the sea surface 9 rotates about the pipe 4 by releasing the restraint that has reversed the top and bottom. This is due to the positional relationship between the center of gravity G of the support 8 and the center C of the through hole 15 of the support 8, and the lower part 17 of the support 8 sinks together with the pipeline 2 while facing the bottom of the sea. To bottom.

  Here, the position of the center of gravity G of the support 8 will be further described. The position of the center of gravity G is the center C on the axis Y passing through the center C of the through hole 15 formed in the support 8 and perpendicular to the bottom 17 of the support 8. Between the bottom 17. In order to ensure that the bottom 17 of the support is directed toward the seabed 1 during subsidence, the vertical position of the center of gravity G is preferably as close to the bottom 17 as possible, and the horizontal position is as far left and right as possible from the axis Y. It is better to set the position so that it does not shift.

  Note that the means for canceling the situation in which the top and bottom of the support 8 are reversed differs depending on the method of reversing the top and bottom. For example, if the rope 20 is lifted by a crane, the rope 20 may be removed, and if it is based on other temporary restraining means, the restraining means may be released. The place where the work is performed may be on the laid ship 3 or in the sea near the sea surface 9. However, even if a technique that requires diver work in the sea is used, it is limited to work near the sea surface 9 to the last. Therefore, the labor is remarkably reduced as compared with the prior art that requires diver work on the seabed 1, that is, the cost can be reduced.

  In addition, in this embodiment, by handling the pipeline 2 with the top and bottom of the support 8 reversed, the interference between the roller 6 installed on the laying ship 3 and the stinger 5 and the support 8 can be avoided. However, as another embodiment, as shown in FIG. 5A, a side cross-sectional view, and FIG. 5B, a front view (CC arrow view of FIG. 5A), The auxiliary member 21 is extended longer than the width of the roller 6 (the length in the longitudinal direction of the roller 6) on the left and right sides in the horizontal direction from the height position, and the support column 12 is provided downward from the end of the auxiliary member 21. By doing so, it is possible to avoid interference with the roller 6 without inverting the top and bottom of the support 8. In this case as well, it is preferable to provide a through hole 15 in the support 8 so that the steel pipe 10 passes through the through hole 15 so that the support 8 can rotate about the steel pipe 10 as an axis. Thereby, it is possible to absorb the influence of the twist around the axis of the pipeline 2 at the time of laying the pipeline 2 or the inclination of the place where the support 8 bottoms.

  In other words, it is sufficient to adopt the most reasonable support 8 structure in consideration of the space around the laying ship 3 and stinger 5, the structure of the roller 6 and the like. The gist of the present invention in which the underwater is settled and then settled on the seabed 1 is not limited by the specific structure of the support 8 employed.

  Thus, in the embodiment of the present invention, when a new submarine pipeline is laid, the support 8 is attached in advance to the pipes 4 before and after the portion of the seabed 1 that intersects the existing line 7, and this support 8 is attached. The newly developed submarine pipeline can be efficiently laid while the existing pipeline 7 is protected without the need for a submarine operation by divers, by drawing out the pipeline 2 from the laying ship 3 and letting it settle and settle. .

DESCRIPTION OF SYMBOLS 1 Seabed 2 Pipeline 3 Laying ship 4 Pipe 5 Stinger 6 Roller 7 Existing line 8 Support 9 Sea surface 10 Steel pipe 11 Concrete coating 12 Strut part 13 Leg part 14 Welded part 15 Through-hole 16 Upper surface 17 Bottom part 20 Rope 21 Auxiliary member 101 Ship 102 Groove 103 Grout mat 111 Sand 112 Crushed stone 113 Mound 121 Protection structure G Center of gravity C Center Y axis

Claims (4)

  When laying a new submarine pipeline, a support is attached in advance to pipes that are placed directly before and after the existing pipeline or cable that is placed directly on the seabed, and the pipeline equipped with the support is installed from the laying ship. A method for laying a submarine pipeline, wherein the pipeline is supported by the support so as to exceed the existing line by being drawn out and settled and settled.   2. The method of laying a submarine pipeline according to claim 1, wherein the support is rotatable about the pipe, and the center of gravity of the support is on the lower side of the support with respect to the axis of rotation.   3. The method of laying a submarine pipeline according to claim 2, wherein the lower end of the support is substantially the same as the height of the lower surface of the coated pipe when the support is rotated so that its lower side is upward.   A submarine pipeline support for use in the submarine pipeline laying method according to claim 1, wherein the lower end of the support is rotated so that the lower side of the support is upward, Submarine pipeline support characterized in that it is substantially the same, and the center of gravity of the support is on the lower side of the support with respect to the axis of rotation.

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