Submarine cable burial depth protection method at outlet of directional drilling pipeline for submarine cable penetration

Abstract

The invention discloses a submarine cable burial depth protection method at an outlet of a directional drilling pipeline for submarine cable crossing, which comprises the following steps of: detachably connecting a burial depth protection pipe on the directional drilling pipeline as a tail section pipeline, and in the construction process of dragging back the underwater directional drilling pipeline, enabling the burial depth protection pipe part of the tail section pipeline to protrude out of the mud surface of a seabed; a working groove is excavated in a seabed to expose the connecting position of the deep-buried protection pipe and the directional drilling pipeline, an outer sleeve of the deep-buried protection pipe is dismantled and removed from the submarine cable, a flexible lining type inner pipe of the deep-buried protection pipe is reserved, and after plugging is conducted, the deep-buried protection pipe and the directional drilling pipeline are sealed. A submarine cable which is located above the seabed mud surface and sleeved with a flexible lining type inner pipe is bent and horizontally laid on the seabed mud surface; and flushing and burying the submarine cable. The flexible lining type inner pipe is used as the outlet of the submarine cable, the problem that the submarine cable generates a suspended section at the outlet of the seabed mud surface can be avoided, the tiling quality of the submarine cable at the outlet of the tail section pipeline is improved, and the protection effect on the submarine cable is improved.

Description

Technical Field

[0001] The invention relates to the technical field of marine engineering, and in particular to a method for protecting the buried depth of a submarine cable at an outlet of a directional drilling pipeline for submarine cable crossing. Background Art

[0002] At present, due to the limitation of directional drilling technology, the outlet of the directional drilling pipeline on the sea side usually protrudes at a certain angle and is exposed above the seabed mud surface to facilitate the construction of the submarine cable. The directional drilling pipeline is usually a metal pipe, please refer to Figure 1 After the submarine cable threading operation is completed, due to the outlet angle of the directional drilling pipeline 1 exposed above the seabed mud surface 2, a small section of the submarine cable 3 will be suspended and cannot be laid in line with the seabed mud surface 2, which poses a great safety hazard. The directional drilling pipeline 1 and the submarine cable 3 exposed above the seabed mud surface are generally protected by covering and burying them deep into the seabed by stacking or throwing cement mortar bags. The disadvantage is that the cement mortar is located above the seabed mud surface, and the cement mortar is washed away by the seawater tide, resulting in the re-exposure of the suspended section of the submarine cable 3 at the outlet of the directional drilling pipeline. Under the action of the tidal force, it is repeatedly bent at the outlet of the directional drilling pipeline and is easily damaged, which poses a safety hazard. For this reason, regular inspections are required to re-cover and bury the submarine cables at the re-exposed directional drilling pipeline outlet and its position to eliminate safety hazards. This method not only has cumbersome construction processes, but also adds a lot of construction and maintenance costs. Summary of the invention

[0003] The purpose of the present invention is to provide a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing, so as to solve the potential safety hazard that the suspended section of the submarine cable at the outlet of the directional drilling pipeline is easily washed away by seawater tides when it is shielded and buried deeply by cement mortar bags, resulting in the suspended section of the submarine cable being exposed again and being easily damaged, as well as the problems of complicated process, high maintenance cost and high maintenance frequency of the method.

[0004] In order to solve the above technical problems, the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing, comprising:

[0005] A buried depth protection pipe is detachably connected to a directional drilling pipeline as a terminal pipeline, the buried depth protection pipe comprises a detachably connected outer casing and a flexible sleeve-type inner pipe installed in the outer casing, one end of the flexible sleeve-type inner pipe and the outer casing both have flanges matching the flange on the directional drilling pipeline, the flange of the flexible sleeve-type inner pipe is located outside the flange of the outer casing, and the buried depth protection pipe is detachably connected to the directional drilling pipeline by bolts penetrating the flange of the outer casing, the flange of the flexible sleeve-type inner pipe and the flange of the directional drilling pipeline;

[0006] During the construction of underwater directional drilling pipeline towing back, the directional drilling pipeline of the last section of the pipeline is completely buried below the seabed mud surface, and the buried depth protection pipe of the last section of the pipeline is partially buried below the seabed mud surface and partially protruded above the seabed mud surface;

[0007] The submarine cable is laid inside the directional drilling pipeline and extended above the seabed mud surface through the buried protection pipe;

[0008] Divers dig a working trench underwater for the buried depth of the last section of the pipeline below the seabed mud surface to expose the connection between the buried depth protection pipe of the last section of the pipeline and the directional drilling pipe. At the working trench, the outer sleeve of the buried depth protection pipe connected to the directional drilling pipe is removed and separated from the submarine cable, and the flexible sleeve-type inner pipe of the buried depth protection pipe connected to the directional drilling pipe is retained;

[0009] The outlet of the flexible sleeve-type inner tube is plugged to seal the gap between the flexible sleeve-type inner tube and the submarine cable, and the submarine cable, which is located above the seabed mud surface and is sleeved with the flexible sleeve-type inner tube, is bent and laid horizontally on the seabed mud surface;

[0010] The submarine cable sheathed with a flexible bushing type inner tube exposed on the seabed mud surface is flushed and buried by submarine cable burying equipment, so that the submarine cable sheathed with a flexible bushing type inner tube exposed above the seabed mud surface is completely buried below the seabed mud surface.

[0011] Furthermore, the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing. The submarine cable is dragged through the entire directional drilling pipeline by a tensioning device at the land end, and after the tension applied to the submarine cable by the tensioning device is removed, the submarine cable lies horizontally on the seabed.

[0012] Furthermore, the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing, in which a diver digs a working groove underwater using a mud flushing and suction device.

[0013] Furthermore, the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing, wherein the method for removing the outer sleeve of the buried depth protection pipe connected to the directional drilling pipeline and separating it from the submarine cable comprises:

[0014] The outer sleeve of the buried depth protection pipe connected to the directional drilling pipeline is removed, the outer sleeve is pulled out from the seabed mud surface, and the outer sleeve is removed from the submarine cable.

[0015] Furthermore, the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing, wherein the outer casing comprises two Haff tubes, and side plates are provided at both ends of the arc-shaped end of each Haff tube. After the two Haff tubes are spliced ​​together, they are detachably connected by evenly distributed bolts penetrating the side plates.

[0016] Furthermore, the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing, wherein the method for removing the outer sleeve of a buried depth protection pipe connected to the directional drilling pipeline and separating it from the submarine cable, and retaining the flexible sleeve-type inner pipe of the buried depth protection pipe connected to the directional drilling pipeline comprises: removing the outer sleeve of the buried depth protection pipe connected to the directional drilling pipeline by removing the bolts at the flange, reconnecting the bolts to the flange of the directional drilling pipeline and the flange of the flexible sleeve-type inner pipe of the buried depth protection pipe, and retaining the flexible sleeve-type inner pipe of the buried depth protection pipe connected to the directional drilling pipeline;

[0017] Pull the outer casing out from the seabed mud surface to above the seabed mud surface;

[0018] Under water above the mud surface of the seabed, remove the bolts connecting the two pieces of Hough tubes on the side plates, remove the two pieces of Hough tubes from the submarine cable respectively, so as to remove the outer sleeve from the submarine cable.

[0019] Furthermore, the present invention provides a method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing. In the buried depth protection pipe, the flexible sleeve-type inner pipe is a pipe body with a variable cross-section from large to small along the flange end to the outlet end.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing. The method comprises the following steps: a buried depth protection pipe composed of an outer sleeve and a flexible sleeve-type inner pipe connected thereto is detachably connected to the directional drilling pipeline as the last section of the pipeline. The directional drilling pipeline of the last section of the pipeline is completely buried below the seabed mud surface. The buried depth protection pipe of the last section of the pipeline is partially buried below the seabed mud surface and partially protrudes above the seabed mud surface. After the submarine cable is passed through the directional drilling pipeline, the submarine cable protrudes through the outlet end of the buried depth protection pipe of the last section of the directional drilling pipeline. The connection between the buried depth protection pipe of the last section of the pipeline and the directional drilling pipeline is exposed by digging a working trench, the outer sleeve connected to the directional drilling pipeline is removed and separated from the submarine cable, and the flexible sleeve inner pipe connected to the directional drilling pipeline is retained. Then, the submarine cable with the flexible sleeve inner pipe above the seabed mud surface can be bent and lie flat on the seabed mud surface, thus avoiding the problem that when the conventional directional drilling pipeline is used as the last section of the pipeline in the traditional process, the directional drilling pipeline protrudes above the seabed mud surface and cannot be bent, causing the submarine cable to lie flat on the seabed mud surface. The problem of a small section of suspension between the outlet of the directional drilling pipeline and the seabed mud surface is improved, and the laying quality of the submarine cable at the outlet of the last section of the pipeline is improved; the submarine cable with a flexible bushing type inner tube exposed on the seabed mud surface is flushed and covered by the submarine cable burying depth equipment, thereby improving the burial depth quality and service life of the submarine cable at the outlet of the last section of the pipeline. Since the flexible bushing type inner tube can bend with the submarine cable and has no suspended section, the problem of the suspended section of the submarine cable at the outlet of the traditional directional drilling pipeline being filled with cement mortar bags and being washed away by seawater tides, resulting in the suspended section of the submarine cable being exposed again and being vulnerable to damage, is avoided, and the protection effect of the submarine cable at the outlet of the last section of the directional drilling pipeline is improved, and the problem of shaping maintenance at the outlet of the last section of the directional drilling pipeline is avoided; under extreme scouring conditions, when a certain thickness of the seabed mud surface is cut off to cause the submarine cable lying flat to be exposed again, the scouring time is extended and the maintenance frequency is reduced. The method has the effects of simple process, no maintenance or low maintenance cost and low maintenance frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the suspended section at the outlet of the directional drilling pipeline in the traditional process after the submarine cable is installed;

[0023] Figure 2 It is a structural schematic diagram showing that the directional drilling pipeline of the last section of the pipeline of the present invention and the buried depth protection pipe are in a connected state;

[0024] Figure 3 It is a schematic diagram of a partial cross-sectional structure of the connection between the directional drilling pipeline and the buried depth protection pipe of the last section of the pipeline of the present invention;

[0025] Figure 4It is a structural schematic diagram of the last section of the pipeline after the directional drilling and support process is completed in the present invention;

[0026] Figure 5 It is a schematic diagram of the structure of the submarine cable of the present invention at the outlet of the last section of the pipeline after the entire directional drilling pipeline is completed;

[0027] Figure 6 It is a structural schematic diagram of the present invention in which a working groove is dug at the connection between the directional drilling pipeline and the buried deep protection pipe of the last section of the pipeline;

[0028] Figure 7 It is a structural schematic diagram of removing the outer casing connected to the directional drilling pipeline on the last section of the pipeline according to the present invention;

[0029] Figure 8 It is a schematic diagram of the structure of removing the outer sleeve on the submarine cable of the present invention;

[0030] Fig. 9 It is a schematic structural diagram of the flexible sleeve-type inner tube of the present invention located on the mud surface of the seabed, bending along with the submarine cable and lying flat on the mud surface of the seabed;

[0031] Fig.10 It is a schematic diagram of the structure of the submarine cable exposed on the seabed mud surface and sheathed with a flexible bushing type inner tube after being buried by flushing in the present invention;

[0032] As shown in the figure:

[0033] 1. Directional drilling pipeline, 2. Seabed mud surface, 3. Submarine cable, 4. Buried depth protection pipe, 5. Outer sleeve, 6. Haff pipe, 7. Flexible bushing inner pipe, 8. Flange, 9. Side plate, 10. Bolts, 11. Diver, 12. Working tank. DETAILED DESCRIPTION

[0034] The present invention is described in detail below in conjunction with the accompanying drawings: The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0035] Please refer to Figures 2 to 10 The embodiment of the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing, comprising:

[0036] Step S101, please refer to Figures 2 to 3A buried depth protection pipe 4 is detachably connected to the directional drilling pipeline 1 as the last section of the directional drilling process. The buried depth protection pipe 4 includes a detachably connected outer sleeve 5 and a flexible sleeve-type inner pipe 7 installed in the outer sleeve 5. One end of the flexible sleeve-type inner pipe 7 and the outer sleeve 5 both have a flange 8 that matches the flange on the directional drilling pipeline 1. The flange 8 of the flexible sleeve-type inner pipe 7 is located on the outside of the flange 8 of the outer sleeve 5. The buried depth protection pipe 4 and the directional drilling pipeline 1 are detachably connected by bolts 10 that penetrate the flange 8 of the outer sleeve 5, the flange 8 of the flexible sleeve-type inner pipe 7, and the flange 8 of the directional drilling pipeline 1.

[0037] Step S102, please refer to Figure 4 In the process of pulling back the underwater directional drilling pipeline 1, the directional drilling pipeline 1 of the last section of the pipeline is completely buried below the seabed mud surface 2, and the buried depth protection pipe 4 of the last section of the pipeline is partially buried below the seabed mud surface 2 and partially protrudes above the seabed mud surface 2. The buried depth protection pipe 4 is composed of a sleeved outer sleeve 5 and a flexible sleeve-type inner pipe 7. Since the outer sleeve 5 is a hard pipe, it can pass through the seabed mud surface 2, avoiding the problem that the flexible sleeve-type inner pipe 7 cannot pass through the seabed mud surface 2 directly. The back-up refers to the pipeline back-up in the directional drilling process. That is to say, the buried depth storage pipe 4 of the terminal pipeline is used as the outlet end protruding from the seabed mud surface 2.

[0038] Step S103, please refer to Figure 5 The submarine cable 3 is inserted into the directional drilling pipeline 1 and extends above the seabed mud surface 2 through the buried depth protection pipe 4. The submarine cable 3 needs to penetrate the entire directional drilling pipeline including the last section of the pipeline.

[0039] Step S104, please refer to Figures 6 to 8 , the diver 11 digs a working groove 12 underwater for the buried depth of the last section of the pipeline below the seabed mud surface 2, that is, excavates the seabed to form the working groove 12 to expose the connection between the buried depth protection pipe 4 of the last section of the pipeline and the directional drilling pipeline 1, removes the outer sleeve 5 of the buried depth protection pipe 4 connected to the directional drilling pipeline 1 at the working groove 12 and separates it from the submarine cable 3, and retains the flexible sleeve type inner pipe 7 of the buried depth protection pipe 4 connected to the directional drilling pipeline 1. In step S104, in order to improve the excavation efficiency of the working groove 12, the diver 11 can dig the working groove 12 underwater by flushing and sucking mud equipment. In step S104, in order to facilitate the separation and removal of the outer sleeve 5 from the submarine cable 3, the outer sleeve 5 of the buried depth protection pipe 4 connected to the directional drilling pipeline 1 can be first removed, and the outer sleeve 5 can be pulled out from the seabed mud surface 2, and the outer sleeve 5 can be removed from the submarine cable 3 underwater on the seabed mud surface 2.

[0040] Step S105, please refer to Fig. 9, the outlet of the flexible sleeve inner tube 7 is blocked to seal the gap between the flexible sleeve inner tube 7 and the submarine cable 3, and the submarine cable 3, which is located above the seabed mud surface 2 and is sleeved with the flexible sleeve inner tube 7, is bent and laid horizontally on the seabed mud surface 2. At this time, the submarine cable 3 does not have a suspended section at the outlet of the flexible sleeve inner tube 7. In step S105, in order to ensure that the submarine cable 3 can be stably and reliably laid horizontally on the seabed mud surface 2, the submarine cable 3 can be dragged through the entire directional drilling pipeline 1 by pre-buried steel wire ropes and other tensioning equipment at the land end, and after removing the tension applied to the submarine cable 3 by the tensioning equipment, the submarine cable 3 is laid horizontally on the seabed surface. Avoid the submarine cable 3 from retracting from the entire directional drilling pipeline 1.

[0041] Step S106, please refer to Fig.10 , the submarine cable 3 with flexible sleeve inner tube 7 exposed on the seabed mud surface 2 is flushed and buried by the submarine cable burying equipment, so that the submarine cable 3 with flexible sleeve inner tube 7 exposed above the seabed mud surface 2 is completely buried below the seabed mud surface 2. At this time, the directional drilling pipeline 1, the flexible sleeve inner tube 7, and the submarine cable 3 are all buried below the seabed mud surface 2. The submarine cable burying equipment can adopt the method of backfilling or dumping. Backfilling is to use engineering ships such as open bottom mud barges to directly dump mud around the submarine cable 3 with flexible sleeve inner tube 7 exposed above the seabed mud surface 2 to cover and bury it. There are also dredgers who grab the mud and pour it on it. Dumping is to slowly put down the cement mortar bag to cover the submarine cable 3 with flexible sleeve inner tube 7 exposed above the seabed mud surface 2 for pressure burying.

[0042] The embodiment of the present invention provides a method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing. A buried depth protection pipe 4 composed of an outer sleeve 5 and a flexible sleeve-type inner pipe 7 sleeved therein is detachably connected to a directional drilling pipeline 1 as an end-section pipeline. The directional drilling pipeline 1 of the end-section pipeline is completely buried below the seabed mud surface 2, and the buried depth protection pipe 4 of the end-section pipeline is partially buried below the seabed mud surface 2 and partially protrudes above the seabed mud surface 2. After a submarine cable 3 is passed through the directional drilling pipeline 1, the submarine cable 3 passes through the outlet of the buried depth protection pipe 4 of the end-section pipeline of the directional drilling pipeline 1. The mouth end protrudes above the seabed mud surface 2, and the connection between the buried depth protection pipe 4 of the last section of the pipeline and the directional drilling pipeline 1 is exposed by digging a working groove 12. The outer sleeve 5 connected to the directional drilling pipeline 1 is removed and separated from the submarine cable 3, and the flexible sleeve type inner pipe 7 connected to the directional drilling pipeline 1 is retained. Then, the submarine cable 3 located above the seabed mud surface 2 and provided with the flexible sleeve type inner pipe 7 can be bent and lie flat on the seabed mud surface 2, thereby avoiding the problem that when the conventional directional drilling pipeline 1 is used as the last section of the pipeline in the traditional process, the directional drilling pipeline 1 protrudes above the seabed mud surface 2 and cannot be bent, causing the submarine cable 3 to lie flat. The problem that a small section of the directional drilling pipeline 1 is suspended between the outlet of the directional drilling pipeline 1 and the seabed mud surface 2 when the directional drilling pipeline 1 is flat on the seabed mud surface 2 is improved, thereby improving the laying quality of the submarine cable 3 at the outlet of the last section of the pipeline; the submarine cable 3 exposed on the seabed mud surface 2 and provided with a flexible bushing type inner tube 7 is buried and covered by the submarine cable burying depth equipment, thereby improving the burying depth quality and service life of the submarine cable 3 at the outlet of the last section of the pipeline, because the flexible bushing type inner tube 7 can bend with the submarine cable 3 without a suspended section, thereby avoiding the problem that the submarine cable 3 at the outlet of the traditional directional drilling pipeline 1 has a suspended section. After the cement mortar bag is filled, it is affected by the scouring of seawater tides, causing the cement mortar bag to be washed away, resulting in the re-exposure of the suspended section of the submarine cable 3, which is vulnerable to damage. The protection effect of the submarine cable 3 at the outlet of the last section of the directional drilling pipeline is improved, and the problem of final maintenance at the outlet of the last section of the directional drilling pipeline is avoided; under extreme scouring conditions, the seabed mud surface 2 is shaved off to a certain thickness, causing the submarine cable 3 lying flat to be re-exposed, thereby extending the scouring time and reducing the maintenance frequency. The method has the effects of simple process, no maintenance or low maintenance cost, and low maintenance frequency.

[0043] Please refer to Figure 3 and Figure 8In order to facilitate the removal of the outer sleeve 5 from the submarine cable 3, the embodiment of the present invention provides a method for protecting the buried depth of the submarine cable at the outlet of the directional drilling pipeline for the submarine cable to cross. The outer sleeve 5 includes two pieces of half tubes 6. Both ends of the arc-shaped end of each of the half tubes 6 are provided with side panels 9. After the two pieces of the half tubes 6 are assembled, they are detachably connected by evenly distributed bolts 10 penetrating the side panels 9. At this time, the outer sleeve 5 is detachably connected, so after removing the bolts 10 on the side panels 9, the two pieces of half tubes 5 can be easily removed from the submarine cable 3. The removal of the two pieces of half tubes 5 is the removal of the outer sleeve 5 from the submarine cable 3. After adopting the detachably connected outer sleeve 5 of this structure, the outer sleeve 5 of the buried depth protection tube 4 connected to the directional drilling pipeline 1 is removed and separated from the submarine cable 3, and the method of retaining the flexible bushing type inner tube 7 of the buried depth protection tube 4 connected to the directional drilling pipeline 1 includes:

[0044] Step S201, dismantle the outer sleeve 5 of the buried depth protection pipe 4 connected to the directional drilling pipe 1 by removing the bolts 10 at the flange 8, reconnect the bolts 10 to the flange 8 of the directional drilling pipe 1 and the flange 8 of the flexible sleeve-type inner pipe 7 of the buried depth protection pipe 4, and retain the flexible sleeve-type inner pipe 7 of the buried depth protection pipe 4 connected to the directional drilling pipe 1.

[0045] Step S202 , pulling the outer sleeve 5 out from the seabed mud surface 2 to above the seabed mud surface 2 .

[0046] Step S203 , remove the bolts 10 connecting the two Hough tubes 6 on the side plates 9 underwater above the seabed mud surface 2 , and remove the two Hough tubes 6 from the submarine cable 3 respectively, so as to remove the outer sleeve 5 from the submarine cable 3 .

[0047] Please refer to Figure 3 , Figures 7 to 10 In the embodiment of the present invention, the submarine cable burial depth protection method at the outlet of the directional drilling pipeline for submarine cable crossing is provided. In the burial depth protection pipe 4, the flexible sleeve-type inner pipe 7 is a variable cross-section pipe body from large to small along the flange 8 end to the outlet end. The flexible sleeve-type inner pipe 7 is a variable cross-section pipe body that can increase the fit of the submarine cable 3 therein, reduce the difficulty of plugging, and reduce the resistance during flushing and burial.

[0048] The method for protecting the buried depth of a submarine cable at the outlet of a directional drilling pipeline for submarine cable crossing provided by an embodiment of the present invention is to detachably connect a buried depth protection pipe 4 to a directional drilling pipeline 1 as the last section of the directional point pipeline, so that the outlet of the directional drilling pipeline 1 at the sea end of the underwater directional drilling pipeline can be below the seabed mud surface 2 after the backhaul is completed and will not be blocked, and the buried depth protection pipe 4 connected thereto acts as a new outlet end protruding above the seabed mud surface 2, becoming the entrance and exit of the submarine cable 3 crossing the pipeline. After the pipeline threading construction of the submarine cable 3 is completed, In order to separate and disassemble the extended section of the directional drilling pipeline 1 and the outer sleeve 5 of the buried depth protection pipe 4 from the directional drilling pipeline 1 connected thereto, the flexible sleeve inner pipe 7 of the buried depth protection pipe 4 is kept connected to the directional drilling pipeline 1, so that the outlet of the directional drilling pipeline 1 can be below the seabed mud surface 2 and can be properly sealed, and at the same time can conform to the bending of the submarine cable 3, and will not hinder the submarine cable 3 at the outlet of the flexible sleeve inner pipe 7 from lying flat on the seabed mud surface 2, and will not form a suspended section, which is beneficial to the subsequent burial protection construction.

[0049] The present invention is not limited to the above-mentioned specific implementation modes. Obviously, the above-mentioned embodiments are only some embodiments of the embodiments of the present invention, but not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention. Those skilled in the art can make other levels of modifications and changes to the present invention. In this way, if these modifications and changes of the present invention fall within the scope of the claims of the present invention, the present invention is also intended to include these changes and changes.

Claims

1. A method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing, characterized in that: include: A buried depth protection pipe is detachably connected to a directional drilling pipeline as a terminal pipeline, the buried depth protection pipe comprises a detachably connected outer casing and a flexible sleeve-type inner pipe installed in the outer casing, one end of the flexible sleeve-type inner pipe and the outer casing both have flanges matching the flange on the directional drilling pipeline, the flange of the flexible sleeve-type inner pipe is located outside the flange of the outer casing, and the buried depth protection pipe is detachably connected to the directional drilling pipeline by bolts penetrating the flange of the outer casing, the flange of the flexible sleeve-type inner pipe and the flange of the directional drilling pipeline; During the construction of underwater directional drilling pipeline towing back, the directional drilling pipeline of the last section of the pipeline is completely buried below the seabed mud surface, and the buried depth protection pipe of the last section of the pipeline is partially buried below the seabed mud surface and partially protruded above the seabed mud surface; The submarine cable is laid inside the directional drilling pipeline and extended above the seabed mud surface through the buried protection pipe; Divers dig a working trench underwater for the buried depth of the last section of the pipeline below the seabed mud surface to expose the connection between the buried depth protection pipe of the last section of the pipeline and the directional drilling pipe. At the working trench, the outer sleeve of the buried depth protection pipe connected to the directional drilling pipe is removed and separated from the submarine cable, and the flexible sleeve-type inner pipe of the buried depth protection pipe connected to the directional drilling pipe is retained; The outlet of the flexible sleeve-type inner tube is plugged to seal the gap between the flexible sleeve-type inner tube and the submarine cable, and the submarine cable, which is located above the seabed mud surface and is sleeved with the flexible sleeve-type inner tube, is bent and laid horizontally on the seabed mud surface; The submarine cable sheathed with a flexible bushing type inner tube exposed on the seabed mud surface is flushed and buried by submarine cable burying equipment, so that the submarine cable sheathed with a flexible bushing type inner tube exposed above the seabed mud surface is completely buried below the seabed mud surface.

2. The method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing according to claim 1 is characterized in that: At the land end, the submarine cable is dragged through the entire directional drilling pipeline by tensioning equipment. After the tension applied to the submarine cable by the tensioning equipment is removed, the submarine cable lies horizontally on the seabed.

3. The method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing according to claim 1 is characterized in that: Divers dig working trenches underwater using mud flushing and suction equipment.

4. The method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing according to claim 1 is characterized in that: The method for removing the outer sleeve of the buried depth protection pipe connected to the directional drilling pipeline and separating and removing it from the submarine cable comprises: Remove the outer sleeve of the buried depth protection pipe connected to the directional drilling pipeline, pull the outer sleeve out of the seabed mud surface, and remove the outer sleeve from the submarine cable.

5. The method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing according to claim 1 is characterized in that: The outer sleeve comprises two Haff tubes, and both ends of the arc-shaped end of each Haff tube are provided with side panels. After the two Haff tubes are butted together, they are detachably connected by evenly distributed bolts penetrating the side panels.

6. The method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing according to claim 5 is characterized in that: The method for removing the outer sleeve of the buried depth protection pipe connected to the directional drilling pipeline and separating it from the submarine cable to retain the flexible sleeve type inner pipe of the buried depth protection pipe connected to the directional drilling pipeline comprises: removing the outer sleeve of the buried depth protection pipe connected to the directional drilling pipeline by removing the bolts at the flange, reconnecting the bolts to the flange of the directional drilling pipeline and the flange of the flexible sleeve type inner pipe of the buried depth protection pipe, and retaining the flexible sleeve type inner pipe of the buried depth protection pipe connected to the directional drilling pipeline; Pull the outer casing out from the seabed mud surface to above the seabed mud surface; Under water above the mud surface of the seabed, remove the bolts connecting the two pieces of Hough tubes on the side plates, remove the two pieces of Hough tubes from the submarine cable respectively, so as to remove the outer sleeve from the submarine cable.

7. The method for protecting the buried depth of submarine cables at the outlet of a directional drilling pipeline for submarine cable crossing according to claim 1 is characterized in that: In the buried deep protection pipe, the flexible sleeve-type inner pipe is a pipe body with a variable cross-section from large to small along the flange end to the outlet end.

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