A buried submarine cable protection method suitable for sea areas with frequent erosion and siltation of the seabed

Abstract

The present application discloses a buried submarine cable protection method suitable for sea areas with frequent erosion and siltation of the seabed, and relates to the field of cable laying. The specific implementation scheme is: according to the width of the tidal ditch and the outer diameter of the submarine cable, the protection value of the upper covering soil of the submarine cable is calculated; according to the protection value, the submarine cable is buried; M geological sampling is carried out in the sea area near the laying of the submarine cable, and the geological sediment particle size gradation of M sampling points is obtained, M is an integer greater than or equal to 20; according to the geological sediment particle size gradation, the average characteristic sediment particle size value of the submarine cable route is calculated; according to the average characteristic sediment particle size value, the grid size of the geotextile is determined, and the geotextile is covered on the upper covering soil; according to the specific state of the sea area where the submarine cable is located, a protective structure is set above the geotextile. The present application realizes an anti-scouring protection structure for shallow burial of submarine cables under the terrain of frequent swinging tidal ditch, which has important guiding significance for the safety protection of submarine cables.

Description

Technical Field

[0001] The present application relates to the field of cable laying, and in particular to a buried submarine cable protection method suitable for sea areas where the seabed is frequently eroded and silted. Background Art

[0002] The underwater topography and landforms in sea areas where tidal creeks frequently swing often evolve extremely drastically. There are not only significant long-term landform evolutions, but also short-term and even drastic landform evolutions shorter than a tidal cycle. Due to the significant changes in the underwater topography in such sea areas, the scouring and silting intensity of the bed surface at the location where the tidal creek swings can often reach more than 5 to 10 meters. Therefore, although submarine cables are often laid at a depth of about 2 meters below the bed surface, when the tidal creek swings to the position of the submarine cable, it is inevitable that the submarine cable is completely exposed above the bed surface, forming a suspended simply supported state. This puts higher requirements on the protection of submarine cables. Summary of the invention

[0003] The present application provides a buried submarine cable protection method suitable for sea areas where the seabed is frequently eroded and silted.

[0004] According to one aspect of the present application, there is provided a method for burying submarine cables suitable for sea areas where the seabed is frequently eroded and silted, comprising:

[0005] The protection value of the upper covering soil of the submarine cable is calculated according to the width of the tidal ditch and the outer diameter of the submarine cable;

[0006] burying the submarine cable according to the protection value;

[0007] Conducting M geological sampling in the sea area near the laying of the submarine cable to obtain the geological sediment particle size distribution of the M sampling points, where M is an integer greater than or equal to 20;

[0008] According to the geological sediment particle size gradation of the M collection points, the average characteristic sediment particle size value of the submarine cable route is calculated;

[0009] Determining the mesh size of the geotextile according to the average characteristic sediment particle size value, and covering the geotextile above the upper covering soil;

[0010] According to the specific state of the sea area where the submarine cable is located, a protective structure is arranged above the geotextile.

[0011] According to the technical solution of the present application, the protection value of the upper covering soil of the submarine cable ensures that the upper covering soil can provide stable protection for the submarine cable below, prevents the submarine tide from changing the position of the submarine cable, ensures that the submarine cable is not affected by changes in the underwater topography of the seabed, and prevents the submarine cable from being exposed above the seabed. The grid size of the geotextile is determined by determining the average characteristic sediment particle size value, and the geotextile is covered on the upper covering soil to achieve the protection operation of the upper covering soil of the submarine cable, prevent the upper covering soil of the submarine cable from loosening and loss, and further increase the protection of the submarine cable. Finally, by setting a protection structure, the geotextile is further fixed, the protection effect of the submarine cable is increased, and protective measures are applied to the submarine cable, the path is optimized, and the wiring of the easily suspended section is avoided. A more suitable submarine cable can be selected, and there is no need to consider more expensive submarine cables for the sake of firmness, thereby reducing unnecessary investment, reducing engineering costs, and effectively avoiding failures.

[0012] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present application.

[0014] Figure 1 A flow chart of a method for burying submarine cables suitable for sea areas with frequent erosion and siltation of the seabed provided in an embodiment of the present application.

[0015] Figure 2 A flow chart of another method for burying submarine cables suitable for sea areas with frequent erosion and siltation of the seabed provided in an embodiment of the present application.

[0016] Figure 3 A flow chart for calculating the average characteristic sediment particle size value provided in an embodiment of the present application. DETAILED DESCRIPTION

[0017] The following is a description of exemplary embodiments of the present application in conjunction with the accompanying drawings, including various details of the embodiments of the present application to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, the description of well-known functions and structures is omitted in the following description.

[0018] The following describes, with reference to the accompanying drawings, a method for burying submarine cables applicable to sea areas with frequent erosion and siltation of the seabed according to an embodiment of the present application.

[0019] It should be noted that the underwater topography and landforms in sea areas where tidal creeks frequently swing often evolve extremely drastically. There are not only significant long-term landform evolutions, but also short-term and even drastic landform evolutions shorter than a tidal cycle. Due to the significant changes in the underwater topography in such sea areas, the scouring and silting intensity of the bed surface at the location where the tidal creek swings can often reach more than 5 to 10 meters. Therefore, although submarine cables are often laid at a depth of about 2 meters below the bed surface, when the tidal creek swings to the position of the submarine cable, it is inevitable that the submarine cable is completely exposed above the bed surface, forming a suspended simply supported state.

[0020] In order to solve the above technical problems, the present application provides a method for burying submarine cables suitable for sea areas where the seabed is frequently eroded and silted. The present application implements the protection operation for the submarine cables by adding covering soil, geotextiles, stones and hook-and-loop bodies above the submarine cables. Specifically, the method for burying submarine cables suitable for sea areas where the seabed is frequently eroded and silted according to the embodiments of the present application is described below with reference to the accompanying drawings.

[0021] Figure 1 A flowchart of a method for burying submarine cables suitable for sea areas with frequent seabed erosion and siltation is provided in an embodiment of the present application, such as Figure 1 The buried protection method for submarine cables in sea areas with frequent erosion and siltation of the seabed includes the following steps:

[0022] Step 101, calculating the protection value of the upper covering soil of the submarine cable according to the tidal ditch width value and the outer diameter length of the submarine cable.

[0023] Among them, the protection value of the upper covering soil refers to the protection width value and protection thickness value of the upper covering soil; the protection width value refers to the width data of the covering soil above the submarine cable. When the width of the covering soil above the submarine cable is greater than or equal to the protection width value, it can provide sufficient protection for the submarine cable below; the protection thickness value refers to the thickness data of the covering soil above the submarine cable. When the thickness of the covering soil above the submarine cable is greater than or equal to the protection thickness value, it can provide sufficient protection for the submarine cable below.

[0024] It should be noted that the protection width of the upper covering soil of the submarine cable can be calculated according to the following steps:

[0025] Obtain the width values ​​of the tidal gullies, and arrange the width values ​​of the tidal gullies in order from small to large, classify the width values ​​of the tidal gullies with the target length as the interval length, and calculate the number of tidal gullies in each classification;

[0026] As an example, the target length is set to 0.5 meters. The width values ​​of the tidal gullies are arranged in order from small to large to obtain a data set of tidal gully width values, where the maximum and minimum values ​​of the tidal gully width values ​​are located at both ends of the data set, and the data set is graded, with the target length of each level being 0.5 meters, and the number of tidal gullies in each level is calculated.

[0027] The frequency of the tidal channel width value is calculated according to the first formula, where the first formula is expressed as follows:

[0028]

[0029] Where m is the serial number of the tidal gully width classification, P m is the frequency corresponding to the mth tidal gully width classification, unit: %; i is the serial number of the tidal gully; n i is the number of tidal gullies corresponding to the i-th tidal gully width classification; N is the total number of tidal gullies.

[0030] In one implementation, a rectangular coordinate system is established with the frequency of the tidal ditch width value as the horizontal coordinate and the tidal ditch width as the vertical coordinate. The frequencies corresponding to the width values ​​of each tidal ditch are marked in the rectangular coordinate system, and the marked results are connected with a smooth curve to obtain a smooth curve.

[0031] The tidal ditch width value corresponding to the preset frequency is found on the smooth curve, and the tidal ditch width value corresponding to the preset frequency is multiplied by the first preset value.

[0032] The outer diameter of the submarine cable is multiplied by a second preset value, and the tidal ditch width multiplied by the first preset value and the outer diameter of the submarine cable multiplied by the second preset value are summed to obtain the protection width value of the upper covering soil of the submarine cable.

[0033] The second preset value is greater than or equal to 8 and less than or equal to 13.

[0034] As an example, the preset frequency is set to 85%, the first preset value is set to 1.2, and the second preset value is set to 10. With the frequency of the tidal ditch width value as the horizontal coordinate and the tidal ditch width as the vertical coordinate, a rectangular coordinate system is established, and the frequencies corresponding to the width values ​​of each tidal ditch are marked in the rectangular coordinate system, and the marked results are connected with a smooth curve to obtain a smooth curve. Find the tidal ditch width value corresponding to the frequency of 85% on the smooth curve, and multiply the tidal ditch width value corresponding to the frequency of 85% by 1.2 times, and add the tidal ditch width value corresponding to the frequency of 85% after multiplication by 1.2 times to 10 times the outer diameter of the submarine cable to obtain the protective width value of the upper covering soil of the submarine cable.

[0035] It should be noted that the protective thickness of the upper covering soil of the submarine cable can be calculated according to the following steps:

[0036] The route of the submarine cable is divided into sections, where the length of each section is determined according to the terrain variation characteristics of the submarine cable laying area, and can usually be set between 100 and 1000 meters from a construction perspective.

[0037] Underwater topographic mapping data within 500m on both sides of each submarine cable section are obtained, and a DEM (Digital Elevation Model) file is formed according to the principle that the resolution is not greater than 5m. According to the DEM file of the submarine area where each submarine cable section is routed, the average bed bottom elevation in the laying area of ​​each submarine cable section is calculated. Among them, the average bed bottom elevation in the laying area of ​​each submarine cable section is the protection thickness value in the laying area of ​​each submarine cable section.

[0038] It should be noted that there are many methods for calculating the average value of the bottom elevation of the bed, such as the direct evaluation method or the cardinality evaluation method; it should be noted that there are many methods for calculating the average value of the bottom elevation of the bed, and two methods for calculating the average value of the bottom elevation of the bed will be compared and described below:

[0039] As an example, the direct evaluation method needs to extract all the bed bottom elevations in the area, and sum up all the bed bottom elevations. After calculating the total number of extracted bed bottom elevations, the average value of the bed bottom elevation can be calculated according to the formula: the sum of all bed bottom elevations ÷ the number of extracted bed bottom elevations = average.

[0040] As another example, the cardinality evaluation method requires selecting the smallest of all bed bottom elevations as the cardinality. The average bed bottom elevation can be calculated according to the formula: cardinality + the difference between each bed bottom elevation and the cardinality ÷ the number of extracted bed bottom elevations = average.

[0041] As an example, according to the terrain change characteristics of the submarine cable laying area, the route of the submarine cable is divided into 20 segments, each with a length of about 500 meters, and the underwater topographic mapping data within 500m on both sides of each section of the submarine cable is obtained to form a DEM file. The average bed bottom elevation of each section of the submarine cable route is calculated based on the DEM data of each section of the submarine cable route, and the protection thickness value of each section of the submarine cable route can be obtained.

[0042] Step 102: bury the submarine cable according to the protection value.

[0043] It should be noted that there are many ways to bury submarine cables, for example, the knife-plow burying plow construction method or the flushing burying plow construction method. It can be understood that there are many ways to bury submarine cables. The following are two examples that can describe the specific methods of burying submarine cables:

[0044] As an example, the knife-plow type burying plow construction method is that when the submarine cable construction ship is laying the submarine cable, it relies on its strong traction to drag the burying plow, so that the knife-plow installed at the tail of the burying plow digs a groove on the seabed, and then buries the submarine cable in it. The burying depth is determined by the plow blade, and the burying depth can be changed by adjusting the plow blade.

[0045] As another example, the flushing burying plow construction method is to use a nozzle installed in the burying plow to spray high-pressure water to make the seabed sand flow and form a groove while carrying out the submarine cable burying operation. The submarine cable can be buried at the bottom of the groove. It can also bury the submarine cable while laying the cable, and can also bury the cable that has been laid on the seabed.

[0046] It should be noted that the above-mentioned buried submarine cable protection method applicable to sea areas with frequent scouring and silting of the seabed is only for the convenience of technical personnel in this field to understand how to lay and install submarine cables, and cannot be used as a specific limitation of the present application. That is to say, the present application can also adopt other means to bury the submarine cable from the buried submarine cable protection method applicable to sea areas with frequent scouring and silting of the seabed to the buried submarine cable protection method applicable to sea areas with frequent scouring and silting of the seabed, which will not be repeated here.

[0047] Step 103, performing M geological samplings in the sea area near the laying of the submarine cable to obtain the geological sediment particle size gradation of the M sampling points, where M is an integer greater than or equal to 20.

[0048] Among them, geological sediment particle size grading refers to the distribution of each level of particle size in sediment particles, and the geological sediment particle size grading can reflect the properties of the parent rock of the sediment, reflect the strength and transport characteristics of the water flow sorting, and is the basic data for sediment research and riverbed evolution calculation.

[0049] It should be noted that seabed geological sampling is different from geological collection on land. Seabed collection requires the use of mud samplers, sampling tubes and box samplers to complete the collection work. Among them, mud samplers are used to collect seabed surface sediment samples. Sampling tubes are mainly of two types: gravity sampling tubes and piston sampling tubes, which are used to collect columnar (core) samples. Box samplers are used to collect undisturbed sediments and their overlying bottom seawater.

[0050] Step 104, based on the geological sediment particle size gradation of the M collection points, the average characteristic sediment particle size value of the submarine cable route is calculated.

[0051] Step 105, determining the mesh size of the geotextile according to the average characteristic sediment particle size value, and covering the geotextile on the upper covering soil.

[0052] It should be noted that the fabric mesh size of the geotextile needs to meet the condition of being less than or equal to the average characteristic sediment particle size value to prevent sediment particles from seeping out of the fabric mesh of the geotextile, thereby causing the protection measures for the submarine cables to fail.

[0053] Among them, geotextile, also known as geotextile, is a permeable geosynthetics made of synthetic fibers by needle punching or weaving.

[0054] Step 106, setting a protective structure above the geotextile according to the specific state of the sea area where the submarine cable is located.

[0055] In one implementation, the size of the stones is determined according to the maximum velocity of the current during high tide in the sea area where the submarine cable is located and the average water depth of the submarine cable routing area; and the stones are laid on top of the geotextile.

[0056] It should be noted that the upper layer of the geotextile needs to be covered with 2 to 3 layers of stones, and the shape of the stones must meet the requirement of having no sharp corners.

[0057] The size of the stones must meet the following conditions:

[0058]

[0059] Where, d is the isochoric particle size of the stone, unit is m; u max is the maximum measured flow velocity during a typical high tide in the engineering sea area, in m / s; h is the average water depth of the submarine cable routing area, in m.

[0060] In one implementation, a plurality of hooking bodies are laid on top of the stone, and the hooking bodies are interlaced with each other to achieve a stable connection.

[0061] It should be noted that 3 to 8 layers of hook-connectors need to be laid on the upper layer of the stones, and the automatic interlacing and interlocking effect of the hook-connectors can be utilized to make the laid hook-connectors automatically connect and interlace with each other to form a strip-like body along the route of the submarine cable.

[0062] By setting up stones and hooks, it is possible to prevent the scouring of the upper covering soil of the submarine cable under the action of hydrodynamic forces such as tides, and to utilize the weight of the stones and the characteristics of the interconnected connection of the strip-like hooks to curb the tendency of the tidal ditch to swing toward the submarine cable routing area.

[0063] According to the buried protection method for submarine cables applicable to sea areas with frequent erosion and siltation of the seabed according to the embodiment of the present application, by calculating the protection value of the upper covering soil of the submarine cable, it is ensured that the upper covering soil can provide stable protection for the submarine cable below, and prevent the submarine tide from changing the position of the submarine cable, and ensure that the submarine cable is not affected by changes in the underwater topography of the seabed, and prevent the submarine cable from being exposed above the seabed surface. By determining the average characteristic sediment particle size value, the grid size of the geotextile is determined, and the geotextile is covered on the upper covering soil to implement the protection operation of the upper covering soil of the submarine cable, prevent the upper covering soil of the submarine cable from loosening and loss, and further increase the protection of the submarine cable. Finally, by setting a protection structure, the geotextile is further fixed, and the protection effect of the submarine cable is increased.

[0064] Figure 2 A flowchart of another method for burying submarine cables suitable for sea areas with frequent erosion and siltation of the seabed provided in the embodiment of the present application. Figure 2 As shown, the buried protection method for submarine cables applicable to sea areas with frequent seabed erosion and siltation may include:

[0065] Step 201, obtaining an underwater terrain contour map of a submarine cable routing area.

[0066] It should be noted that according to the underwater topography of the submarine cable routing area, the underwater topography contour map of the submarine cable routing area is drawn by relevant software (such as CAD computer-aided design, GIS geographic information system, etc.), among which the submarine cable routing area includes the area more than 1 km on both sides of the submarine cable routing.

[0067] Step 202, determining the discrimination conditions of tidal creeks, and identifying tidal creeks that meet the discrimination conditions from the underwater terrain contour map.

[0068] It should be noted that the criteria for determining tidal channels vary according to different actual conditions. Factors that may affect the criteria for determining tidal channels include: the outer diameter of the submarine cable, the length of the submarine cable, the tidal conditions in the sea area where the submarine cable is located, etc.

[0069] For example, the tidal ditch identification conditions are set as tidal ditch width of more than 1m and tidal ditch depth of more than 2m. The entire underwater terrain area is searched according to the contour map of the submarine cable routing area, and all tidal ditches that meet the identification conditions in the submarine cable routing area are identified.

[0070] Step 203, determining the tidal creek width value of the identified tidal creek.

[0071] For example, the criteria for distinguishing tidal gullies are set as tidal gully width of more than 1m and tidal gully depth of more than 2m. The entire underwater terrain area is searched according to the contour map of the submarine cable routing area, and all tidal gullies that meet the criteria in the submarine cable routing area are identified, so as to count the number of identified tidal gullies and the width of each tidal gully.

[0072] Step 204, calculating the protection value of the upper covering soil of the submarine cable according to the tidal ditch width value and the outer diameter length of the submarine cable.

[0073] In the embodiments of the present application, step 204 may be implemented in any of the embodiments of the present application, and the embodiments of the present application do not limit this and will not be described in detail.

[0074] Step 205: bury the submarine cable according to the protection value.

[0075] In the embodiments of the present application, step 205 can be implemented in any of the embodiments of the present application, and the embodiments of the present application do not limit this and will not be described in detail.

[0076] Step 206, conduct M geological samplings in the sea area near the laying of the submarine cable to obtain the geological sediment particle size distribution of the M sampling points, where M is an integer greater than or equal to 20.

[0077] In the embodiments of the present application, step 206 may be implemented in any of the embodiments of the present application, and the embodiments of the present application do not limit this and will not be described in detail.

[0078] Step 207, based on the geological sediment particle size gradation, calculate the average characteristic sediment particle size value of the submarine cable route.

[0079] In the embodiments of the present application, step 207 may be implemented in any of the embodiments of the present application, and the embodiments of the present application do not limit this and will not be described in detail.

[0080] Step 208, determining the mesh size of the geotextile according to the average characteristic sediment particle size value, and covering the geotextile on the upper covering soil.

[0081] In the embodiments of the present application, step 208 may be implemented in any of the embodiments of the present application, and the embodiments of the present application do not limit this and will not be described in detail.

[0082] Step 209, according to the specific state of the sea area where the submarine cable is located, a protective structure is set above the geotextile.

[0083] In the embodiments of the present application, step 209 may be implemented in any of the embodiments of the present application, and the embodiments of the present application do not limit this and will not be described in detail.

[0084] According to the buried submarine cable protection method applicable to sea areas with frequent scouring and silting of the seabed according to the embodiment of the present application, by obtaining the contour map of the submarine cable routing area, it is convenient to obtain the tidal ditch conditions in the submarine cable routing area, and ensure that the data of the acquired tidal ditch width value is true and valid, which provides data guarantee for the subsequent burial of the submarine cable and ensures the accuracy of the data of the upper covering soil obtained by subsequent calculation; by determining the tidal ditch width value of the tidal ditch, feedback on the actual situation of the seabed is achieved, which provides a prerequisite for the subsequent burial of the upper covering soil of the submarine cable, ensures the smooth progress of the subsequent process, and ensures the protection effect of the submarine cable.

[0085] It should be noted that, in order to further ensure the protection effect of the submarine cable, optionally, Figure 3 As shown, Figure 3 A flow chart for calculating the average characteristic sediment particle size value provided in an embodiment of the present application.

[0086] Step 301, a particle distribution curve is drawn according to the geological sediment particle size distribution of M collection points.

[0087] The particle distribution curve reflects the relative content of each particle group in the measured object. It is a geometric figure that intuitively reflects the particle size distribution composition of sediment. It is also an important basis for calculating relevant characteristic values ​​and data compilation. The slope of the particle distribution curve can be used to roughly judge the uniformity of the soil or whether the grading is good.

[0088] Step 302, divide the submarine cable routing area into regions, calculate the characteristic sediment particle size value of each regional center point based on the regional division result of the submarine cable routing area and the particle distribution curve, and calculate the average characteristic sediment particle size value of the submarine cable routing based on the characteristic sediment particle size value of each regional center point.

[0089] Among them, in the embodiments of the present application, the characteristic sediment particle size value refers to the diameter of the sediment particles at the center point of each area in the submarine cable routing area.

[0090] In the embodiments of the present application, the average characteristic sediment particle size value refers to the average diameter of all sediment particles in the submarine cable routing area.

[0091] It should be noted that the characteristic sediment particle size value of each regional center point is calculated by the second formula, which is expressed as follows:

[0092]

[0093]

[0094]

[0095] Where i is the serial number of each sampling point, L i is the distance from the i-th sampling point to the j-th region center point; x i ,y i is the coordinate of the i-th sampling point; j is the serial number of each area, x j ,y j is the horizontal and vertical coordinates of the center point of the jth region; n is the total number of sampling points; ω i is the weight parameter; d j is the characteristic sediment particle size value of the center point of the jth region.

[0096] It should be noted that the average characteristic sediment particle size value of the entire submarine cable route is calculated by the third formula, which is expressed as follows:

[0097]

[0098] In the formula, l k is the length of the k-th region segment; l t is the length of the t-th regional segment; m is the number of submarine cable routing segments or the number of submarine cable routing zones; d k is the characteristic sediment particle size value of the center point of the kth area; D is the average characteristic sediment particle size value of the submarine cable route.

[0099] According to the buried protection method for submarine cables applicable to sea areas with frequent erosion and siltation of the seabed according to the embodiment of the present application, by dividing the particle distribution curve into regions and obtaining the characteristic sediment particle size value of the center point of each region, it is ensured that the actual situation of the sea area near the submarine cable can be reflected more accurately, and the average characteristic sediment particle size value of the entire submarine cable route is calculated according to the characteristic sediment particle size value of the center point of each region, so as to ensure that the geotextile can provide stable protection for the submarine cable and prevent sediment particles from penetrating from the fabric grid of the geotextile.

[0100] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this application can be executed in parallel, sequentially or in different orders, as long as the expected results of the technical solution disclosed in this application can be achieved, and this document is not limited here.

[0101] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A buried submarine cable protection method suitable for sea areas with frequent erosion and siltation of the seabed, characterized in that: include: The protection value of the upper covering soil of the submarine cable is calculated according to the width of the tidal ditch and the outer diameter of the submarine cable; The protection value of the upper layer of soil covering the submarine cable refers to the protection width value and the protection thickness value of the upper layer of soil covering the submarine cable; burying the submarine cable according to the protection value; Conducting M geological sampling in the sea area near the laying of the submarine cable to obtain the geological sediment particle size distribution of the M sampling points, where M is an integer greater than or equal to 20; According to the geological sediment particle size gradation of the M collection points, the average characteristic sediment particle size value of the submarine cable route is calculated; Determining the mesh size of the geotextile according to the average characteristic sediment particle size value, and covering the geotextile above the upper covering soil; According to the specific state of the sea area where the submarine cable is located, a protective structure is arranged above the geotextile; The protection value of the upper covering soil of the submarine cable is calculated based on the tidal ditch width and the outer diameter of the submarine cable, including: Arrange the width values ​​of the tidal gullies in order from small to large, classify the width values ​​of the tidal gullies with a target length of meters as an interval length, and calculate the number of tidal gullies in each classification; The frequency of the tidal gully width value is calculated according to the first formula; Calculating the protection value of the upper covering soil of the submarine cable according to the frequency of the tidal gully width value and the outer diameter length of the submarine cable; The first formula is expressed as follows: Where m is the serial number of the tidal gully width classification, P m is the frequency corresponding to the mth tidal gully width classification, unit: %; i is the serial number of the tidal gully; n i is the number of tidal channels corresponding to the i-th tidal channel width classification; N is the total number of tidal channels; The calculation of the protection value of the upper covering soil of the submarine cable according to the frequency of the tidal gully width value and the outer diameter length of the submarine cable comprises: A rectangular coordinate system is established with the frequency of the tidal ditch width value as the abscissa and the tidal ditch width value as the ordinate, the frequencies corresponding to the graded width values ​​of each tidal ditch are marked in the rectangular coordinate system, and the marked results are connected with a smooth curve to obtain a smooth curve; Finding the tidal ditch width value corresponding to the preset frequency on the smooth curve, and multiplying the tidal ditch width value corresponding to the preset frequency by the first preset value; The outer diameter of the submarine cable is multiplied by a second preset value, and the tidal ditch width value multiplied by the first preset value and the outer diameter of the submarine cable multiplied by the second preset value are summed to obtain the protection value of the upper covering soil of the submarine cable.

2. The method according to claim 1, characterized in that Also includes: Obtaining an underwater topographic contour map of the submarine cable routing area; Determining the discrimination conditions of tidal creeks, and identifying the tidal creeks satisfying the discrimination conditions from the underwater terrain contour map; A tidal channel width value of the identified tidal channel is determined.

3. The method according to claim 1, characterized in that The average characteristic sediment particle size value of the submarine cable route is calculated based on the geological sediment particle size gradation of the M collection points, including: Draw a particle distribution curve diagram according to the geological sediment particle size distribution of the M collection points; Give the characteristic particle size of bottom sediment corresponding to a certain collection point; The submarine cable routing area is divided into regions, and the characteristic sediment particle size value of the center point of each region is calculated based on the regional division result of the submarine cable routing area and the particle distribution curve diagram; the average characteristic sediment particle size value of the submarine cable routing is calculated based on the characteristic sediment particle size value of the center point of each region.

4. The method according to claim 3, characterized in that The characteristic sediment particle size value of each area center point is calculated by the second formula, and the second formula is expressed as follows: Where i is the serial number of each sampling point, L i is the distance from the i-th sampling point to the j-th region center point; x i ,y i is the coordinate of the i-th sampling point; j is the serial number of each area, x j ,y j is the horizontal and vertical coordinates of the center point of the jth region; n is the total number of sampling points; ω i is the weight parameter; d j is the characteristic sediment particle size value of the center point of the jth region.

5. The method according to claim 3, characterized in that: The average characteristic sediment particle size value of the entire submarine cable route is calculated by the third formula, and the third formula is expressed as follows: In the formula, l k is the length of the k-th region segment; l t is the length of the t-th regional segment; m is the number of submarine cable routing segments or the number of submarine cable routing zones; d k is the characteristic sediment particle size value of the center point of the kth area; D is the average characteristic sediment particle size value of the submarine cable route.

6. The method according to claim 1, characterized in that According to the specific state of the sea area where the submarine cable is located, a protective structure is arranged above the geotextile, including: Determining the size of the stone according to the maximum velocity of the current during the high tide in the sea area where the submarine cable is located and the average water depth of the submarine cable routing area; The stones are laid on top of the geotextile.

7. The method according to claim 6, characterized in that The size of the stones must meet the following conditions: Where, d is the isochoric particle size of the stone, unit is m; u max is the maximum measured flow velocity during a typical high tide in the engineering sea area, in m / s; h is the average water depth of the submarine cable routing area, in m.

8. The method according to claim 6, characterized in that Also includes: A plurality of hooking bodies are laid on the stones, and the hooking bodies are interlaced with each other to be stably connected.

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