A method for laying a submarine cable on land based on trenchless directional drilling through hard rock

Abstract

The present application relates to a kind of hard rock crossing of non-excavation directional drilling based on submarine cable landing construction method, belong to the technical field of optical cable layout, including the following steps: design from high to down and between vertical plane certain angle and the preset trajectory of through hard rock slope surface;Control directional drilling machine along the preset trajectory and drill guide hole;Control the drill rod of directional drilling machine along the preset trajectory and back drag, and finally form guide final hole by expanding the guide hole;Excavation anchoring well of construction operation and the cable trench being communicated with the anchoring well at suitable position, and install anchoring device inside anchoring well;Drag rope of armoured submarine cable is passed from guide final hole to shore.The present application avoids trenching on hard rock, reasonably reduces construction cost, avoids trestle erection on steep slope at the same time, reduces the landscape influence to rock shore reef, avoids the influence of scouring, corrosion to cable structure.

Description

Technical Field

[0001] This invention relates to a method for submarine cable landing construction based on trenchless directional drilling through hard rock, belonging to the field of optical cable laying technology. Background Technology

[0002] Submarine cables are communication cables laid on the seabed to meet the demand for large-scale international data transmission. Currently, besides satellite communication, submarine cables are the primary means of connecting the world. Since the 1960s, submarine communication cables have gradually become widespread. Submarine cable technology combines fiber optic communication technology and marine engineering technology. The cables are made of multi-layered composite materials to ensure high-quality communication even in harsh marine environments.

[0003] The main equipment required for submarine cable laying includes cable-laying vessels, tugboats, anchor boats, amphibious excavators, cable laying machines, winches, generators, and directional drilling rigs. Submarine cable laying is a relatively special construction project, and currently there is a lack of corresponding design specifications, construction specifications, and quality acceptance specifications.

[0004] Existing submarine cable laying mainly includes several steps: cable splicing, sea trial, sea sweeping, laying of the main traction steel cable, landing preparation, initial landing, construction of the burial section, and terminal landing. Based on existing submarine cable landing schemes, it is easy to see that they are mainly suitable for landing sections with relatively flat terrain and predominantly soil foundations, such as those using trenching, casing, or concrete trestle bridges. Trenchless directional drilling is also mainly used for crossing seabed soil foundations and relatively straight sections of mountains. For submarine cable landings with large elevation differences and hard rock foundations, there are significant limitations.

[0005] (1) The trenching and burial construction scheme is difficult to implement for landing sections with steep slopes, large elevation differences and hard rock layers. The construction period is long, the protection of the submarine cable landing is difficult, and there are significant safety hazards in the construction process.

[0006] (2) Casting reinforced concrete trestle bridges in hard rock layers with large elevation differences and steep slopes not only involves a huge amount of work, but also presents problems such as difficulty in trestle bridge construction, difficulty in erosion protection, changes in the appearance of the existing coastline, and potential impact on the future suitability of the coastline. In scenic areas, it may also affect the landscape.

[0007] (3) If the existing horizontal directional drilling construction is adopted, it will be constrained by the trajectory control of directional drilling and will not be able to solve the problem of large elevation difference.

[0008] (4) If exposed steel structure trestle bridges or other forms of overhead laying are used, there are disadvantages such as theft and disaster prevention. At the same time, the corrosion and erosion prevention of steel structures by the sea are prominent issues.

[0009] A method for landing submarine cables on bedrock coastlines, disclosed in Chinese invention patent CN116706818A, includes placing the submarine cable inside a steel sleeve; selecting a bedrock surface on the seabed; placing several steel sleeves containing the submarine cable on the bedrock surface, with the steel sleeves arranged side by side and connected by locking buckles; filling the outside of the steel sleeves with a quick-setting concrete layer, the quick-setting concrete layer being at least 600mm higher than the steel sleeves and sloping along both sides at a ratio of not less than 1:2; laying an asphalt coating on the surface of the quick-setting concrete layer, with a thickness of not less than 400um; the front of the steel sleeves directly connects to the submarine cable trench for direct burial in the sea area, and the rear connects to the cable trench on land; a cable trench bedding layer is arranged at the bottom of the cable trench, a cable trench cover is arranged at the top, and sandbags are filled inside the cable trench.

[0010] The above reference example is applicable to bedrock coasts, but trenching is still required for laying the foundation, and it is suitable for landing points with gentle slopes. Therefore, improvements are urgently needed. Summary of the Invention

[0011] To overcome the shortcomings of existing submarine cable landing construction methods, such as poor applicability to large elevation differences, hard rock foundations, and high construction difficulty, this invention designs a submarine cable landing construction method based on trenchless directional drilling through hard rock. This method avoids trenching and laying in hard rock, reasonably reducing construction costs. It also avoids building trestle bridges on steep slopes, reducing the impact on the landscape of rocky shores and reefs, and avoiding the impact of erosion and corrosion on cable structures.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A method for submarine cable landing construction based on trenchless directional drilling through hard rock includes the following steps:

[0014] S1: Ensure that the location of the directional drilling rig meets safety protection requirements;

[0015] S2: Design a pre-set trajectory that is at a certain angle to the vertical plane and runs through the hard rock slope from a high point downwards;

[0016] S3: Control the directional drilling rig to drill a guide hole along the preset trajectory;

[0017] S4: Control the drill rod of the directional drilling rig to pull back along the preset trajectory, enlarge the guide hole, and perform at least one enlargement operation to finally form the guide final hole;

[0018] S5: Excavate the anchoring well and the cable trench connected to the anchoring well at a suitable location, and install the anchoring device inside the anchoring well.

[0019] S6: After the armored submarine cable reaches the shore and is wound a certain number of times, the traction rope of the armored submarine cable is passed through the guide terminal hole to the shore.

[0020] S7: At low tide, lay several layers of sandbags from the outlet of the guide hole to the point where the armored submarine cable is pulled out of the seabed.

[0021] S8: Pull the traction rope of the armored submarine cable to the anchoring well, then strip the armor of the armored submarine cable and fix the cable to the anchoring device, and at the same time connect the end of the cable to the cable trench.

[0022] S9: Rocks are thrown from the top of the sandbags to form a rockfill dam, and the rockfill dam is made higher than the exit of the guide hole.

[0023] Furthermore, it also includes:

[0024] Step S10: After several high and low tides, check the changes in the surface riprap of the rockfill dam and repair any thinner sections.

[0025] Furthermore, the lower layer of the rockfill dam is a layer of small-diameter stones, and the upper layer is a layer of large-diameter stones.

[0026] Furthermore, the slope on both sides of the rockfill dam is less than 30°.

[0027] Furthermore, step S3 also includes: when multiple armored submarine cables need to be laid, multiple guide holes are drilled and the multiple guide holes are enlarged to form guide final holes.

[0028] Furthermore, the net distance between two adjacent guide holes is greater than twice the outer diameter of the guide hole.

[0029] Furthermore, step S4 needs to be performed when the seawater is at low tide.

[0030] Furthermore, the diameter of the guide hole is at least 2.5 times the outer diameter of the armored submarine cable.

[0031] Furthermore, in step S7, the sandbags are laid in 2 to 3 layers.

[0032] Furthermore, the guide hole is a circular hole.

[0033] Compared with the prior art, the present invention has the following features and beneficial effects:

[0034] 1. In this invention, trenchless directional drilling is used to penetrate hard rock and land submarine cables on reefs with large elevation differences. The directional drilling construction machinery is set up on the top of the shore. The cable channel is connected to the seabed horizontally through a certain curvature radius after the inclined hole is drilled. This avoids trenching and laying in hard rock and reasonably reduces construction costs.

[0035] 2. In this invention, after trenchless directional drilling and back-drilling, there is no need to install a protective pipe inside the hole. The rock hole with high strength is directly used as a natural protective hole for the cable, which reduces the amount of construction work, lowers the construction cost, and provides good protection.

[0036] 3. In this invention, the climbing section where the submarine cable enters the rock cavity from the seabed adopts the measures of raising the bottom with sandbags and protecting the top with riprap. This avoids problems such as vortex-induced vibration and scouring caused by the cable being suspended in the climbing section, and does not affect the current state of the reef. This achieves green and environmentally friendly construction, avoids the construction of trestle bridges on steep slopes, reduces the impact on the landscape of the rocky reef, and avoids the impact of scouring and corrosion on the cable structure.

[0037] 4. In this invention, the construction work of the suspended section is realized by making full use of the ebb tide time, thus avoiding major repairs and reconstruction of the cable climbing section trestle. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the operation of drilling the guide hole according to the present invention;

[0039] Figure 2 This is a schematic diagram of the working process of the present invention during hole enlargement;

[0040] Figure 3 This is a schematic diagram of the structure after the completion of the construction of this invention;

[0041] Figure 4 This is a schematic front view cross-sectional view of the rockfill dam of the present invention.

[0042] The attached diagram is labeled as follows: 1. Hard rock slope; 2. Directional drilling rig; 3. High tide sea surface; 4. Preset trajectory; 6. Pilot hole; 12. Pilot final hole; 14. Cable trench; 15. Anchoring device; 16. Anchoring well; 17. Armored submarine cable; 18. Sandbag; 19. Rockfill dam. Detailed Implementation

[0043] The present invention will now be described in more detail with reference to the embodiments.

[0044] It should be noted that the hard rock referred to in this invention refers to the rock strata f tk ≥60MPa.

[0045] like Figures 1 to 3 As shown in the figure, the submarine cable landing construction method based on trenchless directional drilling through hard rock in this embodiment includes the following steps:

[0046] S1: Ensure that the location of directional drilling rig 2 meets safety protection requirements;

[0047] S2: Design a pre-defined trajectory 4 that is at a certain angle to the vertical plane and runs through the hard rock slope 1 from a high point downwards;

[0048] S3: Control the directional drilling rig 2 to drill the guide hole 6 along the preset trajectory 4;

[0049] S4: Control the drill rod of the directional drilling machine 2 to pull back along the preset trajectory 4, enlarge the guide hole 6, and perform at least one enlargement operation to finally form the guide final hole 12;

[0050] S5: Excavate the anchoring well 16 and the cable trench 14 connected to the anchoring well 16 at a suitable location, and install the anchoring device 15 inside the anchoring well 16.

[0051] S6: After the armored submarine cable 17 reaches the shore and is wound a certain number of times to form an Ω shape, the towing rope of the armored submarine cable 17 is passed through the guide terminal hole 12 to the shore; the armored submarine cable 17 is wound a certain number of times to form an Ω shape to form excess cable, which facilitates dragging and prevents the cable from breaking.

[0052] S7: During low tide, several layers of sandbags 18 are laid from the outlet position of the guide hole 12 to the position of the lead-out soil of the armored submarine cable 17 on the seabed; in this embodiment, the outlet position of the guide hole 12 is set at the lower end of the sea surface 3 at high tide.

[0053] S8: Pull the traction rope of the armored submarine cable 17 to the anchoring well 16, then strip the armor of the armored submarine cable 17 and fix the cable to the anchoring device 15, and at the same time connect the end of the cable to the cable trench 14.

[0054] S9: Rocks are thrown at the top of the sandbag 18 to form a rockfill dam 19, and the rockfill dam 19 is higher than the exit of the guide hole 12.

[0055] As can be seen from the above description, the beneficial effects of the present invention are as follows: By drilling the guide hole 6 and the guide terminal hole 12 to lay the cable, it is not only unnecessary to install a protective pipe inside the hole, but the high-strength rock hole can be directly used as a natural protective hole for the cable. Moreover, it avoids trenching and laying in hard rock, thus reasonably reducing construction costs. At the same time, by raising the cable with sandbags 18 and setting up the rockfill dam 19, problems such as vortex-induced vibration and scouring caused by the cable being suspended in the climbing section are avoided, and the current state of the reef is not affected, thus achieving green and environmentally friendly construction. Finally, the corresponding construction work can be carried out by making full use of the tides, and the construction process is simple, easy to implement and manage.

[0056] Furthermore, it also includes:

[0057] Step S10: After several high and low tides, check the changes in the surface riprap of the rockfill dam 19 and repair the thinner parts. This strengthens the stability of the rockfill dam 19, extends its service life, improves its protective performance, and enhances its landscape value.

[0058] Furthermore, the lower layer of the rockfill dam 19 consists of a small-diameter stone layer, while the upper layer consists of a large-diameter stone layer. The upper large-diameter stone layer can absorb and disperse the impact force of ocean waves and swells, which helps to reduce the impact and damage of ocean waves and swells on the rockfill dam 19. The lower small-diameter stone layer can fill the gaps between the large-diameter stones, increase the overall density of the rockfill dam 19, and improve the stability of the rockfill dam 19.

[0059] Furthermore, the slopes on both sides of the rockfill dam 19 are less than 30° to improve the stability of the structure, reduce the erosion and loss of soil and rock, and increase safety.

[0060] Furthermore, step S3 also includes: when multiple armored submarine cables 17 need to be laid, multiple guide holes 6 are drilled and the multiple guide holes 6 are enlarged to form guide final holes 12, thereby improving applicability.

[0061] Furthermore, the net distance between two adjacent guide holes 12 is greater than twice the outer diameter of the guide hole 12. By maintaining a sufficient net distance, interference between adjacent guide holes 12 can be avoided.

[0062] At the same time, the net distance between adjacent guide holes 12 is large enough to avoid excessive tension and stress concentration during the laying of armored submarine cable 17, and to avoid damage to the sidewall of guide holes 12.

[0063] Furthermore, step S4 needs to be carried out when the seawater is at low tide to facilitate construction and make full use of the ebb tide time.

[0064] Furthermore, the diameter of the guide hole 12 is at least 2.5 times the outer diameter of the armored submarine cable 17 to ensure unobstructed passage, reduce the risk of stress concentration, and improve safety and reliability.

[0065] Furthermore, in step S7, the sandbags 18 are laid in 2 to 3 layers, which improves the support stability and reduces the occurrence rate of submarine cable failures.

[0066] Furthermore, the guide hole 12 is a circular hole.

[0067] The working principle of this invention is as follows: Trenchless directional drilling is used to penetrate hard rock and land submarine cables on reefs with significant elevation differences. The directional drilling equipment is installed on the shore top, and the cable is connected to the seabed via a horizontal cable channel using either an inclined borehole or a borehole with a specific radius of curvature. This avoids trenching in hard rock, thus significantly reducing construction costs. After the trenchless directional drilling is pulled back and enlarged, there is no need to install protective pipes inside the hole; the high-strength rock borehole is used directly as a natural protective hole for the cable, further reducing the amount of construction work and lowering costs. The construction is cost-effective and provides good protection. The cable's ascent section from the seabed into the rock cavity utilizes a combination of bottom sandbag padding and top rock protection. This avoids vortex-induced vibration and erosion problems caused by the cable being suspended in the ascent section, without affecting the existing reefs, achieving green and environmentally friendly construction. It also avoids the need to build trestle bridges on steep slopes, minimizing the impact on the rocky reef landscape and preventing erosion and corrosion of the cable structure. Furthermore, it fully utilizes the ebb and flow of tides to enable construction work on the suspended section, avoiding major repairs and reconstruction of the trestle bridge for the cable ascent section.

[0068] In the description of this invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0069] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0070] Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for submarine cable landing construction based on trenchless directional drilling through hard rock, characterized in that: Includes the following steps: S1: Ensure that the location of the directional drilling rig (2) meets the safety protection requirements; S2: Design a pre-defined trajectory (4) that is at a certain angle to the vertical plane and runs through the hard rock slope (1) from a high point downwards. S3: Control the directional drilling rig (2) to drill the guide hole (6) along the preset trajectory (4); S4: Control the drill rod of the directional drilling machine (2) to pull back along the preset trajectory (4), enlarge the guide hole (6), and enlarge the hole at least once to finally form the guide final hole (12). S5: Excavate the anchoring well (16) for construction work and the cable trench (14) connected to the anchoring well (16) at a suitable location, and install the anchoring device (15) inside the anchoring well (16). S6: After the armored submarine cable (17) reaches the shore and is wound a certain number of times, the traction rope of the armored submarine cable (17) is passed through the guide terminal hole (12) to the shore. S7: At low tide, lay several layers of sandbags (18) from the outlet position of the guide hole (12) to the position of the lead-out soil of the armored submarine cable (17) on the seabed. S8: Pull the traction rope of the armored submarine cable (17) to the anchoring well (16), then strip the armor of the armored submarine cable (17) and fix the cable to the anchoring device (15), and at the same time connect the end of the cable to the cable trench (14). S9: Throw stones at the top of the sandbag (18) to form a rockfill dam (19), and make the rockfill dam (19) higher than the exit of the guide hole (12); Step S4 needs to be performed when the seawater is at low tide, and the outlet position of the guide hole (12) is higher than the low tide seawater level and lower than the high tide seawater level.

2. The method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 1, characterized in that: Also includes: Step S10: After several high and low tides, check the changes in the surface riprap of the rockfill dam (19) and make supplementary repairs to the thinner parts.

3. The method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 1, characterized in that: The lower layer of the rockfill dam (19) is a small-diameter rock layer, and the upper layer is a large-diameter rock layer.

4. The method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 3, characterized in that: The slopes on both sides of the rockfill dam (19) are less than 30°.

5. The method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 1, characterized in that: Step S3 also includes: when multiple armored submarine cables (17) need to be laid, multiple guide holes (6) are drilled and the multiple guide holes (6) are enlarged to form guide final holes (12).

6. The method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 5, characterized in that: The net distance between two adjacent guide holes (12) is greater than twice the outer diameter of the guide hole (12).

7. A method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 6, characterized in that: The diameter of the guide hole (12) is at least 2.5 times the outer diameter of the armored submarine cable (17).

8. The method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 1, characterized in that: In step S7, the sandbags (18) are laid in 2 to 3 layers.

9. The method for submarine cable landing construction based on trenchless directional drilling through hard rock according to claim 1, characterized in that: The guide hole (12) is a circular hole.

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