Submarine cable anti-scouring modified oyster shell nanofiber high-strength solidified soil and preparation method thereof

Abstract

The invention discloses submarine cable anti-scouring modified oyster shell nanofiber high-strength solidified soil and a preparation method thereof, and is applied to the fields of ocean engineering and civil engineering. The formula is mainly composed of fly ash and a curing agent, the water content of the fly ash is controlled to be 0.9-0.7%, and the formula comprises the following components in percentage by mass: 30-40% of cement; 20-40% of fly ash; 20-40% of slag powder; 0.5-3% of cellulose; 0.4-0.5% of a phenolic aldehyde amine curing agent; 8 to 12% of modified oyster shell nanofiber; 0.5%-1.5% of a bio-based anti-dispersing agent; 3-5% of nano silicon dioxide; and 1-2% of an auxiliary reinforcing agent. In order to reduce the influence caused by seawater scouring, an interval laying method is adopted in the construction process, and the scouring influence of water flow on the solidified soil can be effectively reduced. The method has the beneficial effects that (1) the coal ash and the curing agent are mixed to prepare the solidified soil, the coal ash is wide in source, meanwhile, natural resources such as gravel are saved, and the protection cost is low; (2) seaside attached oyster shells or catering industry waste oyster shells are recycled and reused to prepare high-strength fibers for solidifying soil to enhance the strength; (3) the generated solidified soil is applied to ocean submarine cable protection, underwater solidification is fast, the strength is high, underwater dispersion is avoided in the construction process, the anti-scouring effect is good, and through combination of solidified geotechnical cloth, the construction efficiency is greatly improved; and a rigid and soft protection system can be realized at the seabed.

Description

Technical Field

[0001] The invention relates to a submarine cable scour-resistant modified oyster shell nanofiber high-strength solidified soil, which is applied to the fields of marine engineering and civil engineering. Background Art

[0002] At present, submarine cables are widely used in my country, such as offshore photovoltaic power generation and offshore wind power. However, the submarine cables are laid deep in the seabed mud. Under the influence of complex waves and currents, the scouring phenomenon is becoming increasingly serious, posing a hidden danger to the safe operation of the submarine cables.

[0003] Currently, the main forms of anti-scour protection include physical protection methods such as riprap, sandbags, sand quilts, and bionic aquatic plants. First, the construction costs of these measures are high and they do not change the nature of the covering soil at the source. Second, riprap piles will produce a dam effect, which will sink under the scouring and hollowing effect of the water flow, easily causing unevenness on the seabed, further increasing the probability of scour. Although grouting underwater concrete is strong, it consumes a large amount of resources such as cement, sand and gravel, and is very expensive. In summary, it is particularly important to develop a low-cost, high-strength solidified soil for submarine cable anti-scour. Summary of the Invention

[0004] In response to the above problems, the present invention discloses a high-strength solidified soil made of modified oyster shell nanofibers for anti-scour of submarine cables and a preparation method thereof. The soil is prepared by mixing modified oyster shell nanofibers with fly ash and the like, and adding additives such as anti-bleeding, anti-dispersion, micro-expansion, and anti-segregation. After adding seawater and stirring, the soil has excellent properties such as high fluidity, little water bleeding, no shrinkage, and no pollution to water quality and the surrounding environment. It can not only meet construction requirements, but also reduce economic costs and improve construction efficiency. At the same time, a preparation method and a construction method thereof are provided, which utilize modified oyster shell nanofibers to provide a spatial network structure and CSH adhesives to enhance the overall solidified soil strength, while enhancing the performance of fly ash, thereby more effectively solving the problems of submarine cable protection and scouring.

[0005] The technical solution adopted in the present invention is:

[0006] A high-strength stabilized soil made of oyster shell nanofibers with erosion resistance for submarine cables, wherein the fly ash moisture content is controlled at 0.9% to 0.7%. The mass percentages of the components are as follows:

[0007] Cement 30-40%; fly ash 20-40%; slag powder 20-40%; cellulose 0.5-3%; silane coupling agent 0.4-0.5%; modified oyster shell nanofiber 8-12%; bio-based dispersant 0.5-1.5%; nano-silica 3-5%; auxiliary reinforcing agent 1-2%

[0008] The present invention also has the following additional technical features:

[0009] Preferably, the cement is 42.5 ordinary Portland cement.

[0010] Preferably, the fly ash is Class I fly ash with a specific surface area of ​​≥400m 2 / kg.

[0011] Preferably, the slag powder is S95 grade ultrafine mineral powder with a specific surface area of ​​≥3000m 2 / kg.

[0012] Preferably, the cellulose is hydroxypropyl methylcellulose.

[0013] Preferably, the main component of the silane coupling agent is γ-aminopropyltriethoxysilane.

[0014] Preferably, the main component of the bio-based dispersant is a sulfonated polysaccharide derivative.

[0015] Preferably, the main component of the auxiliary enhancer is a specific complex of sodium gluconate and triethanolamine.

[0016] Preferably, the modified oyster shell nanofiber has the following characteristics:

[0017] Modified oyster shell nanofibers offer numerous advantages, including high interfacial bonding strength, low cost, and low carbon footprint. The nanogrooves on the oyster shell surface mechanically anchor the cement hydration products, resulting in high modulus and toughness. During the formation process, the oyster shell possesses a helical structure of biogenic calcium carbonate, resulting in a flexural strength three times greater than that of synthetic calcium carbonate. The natural organic matrix also enhances toughness. Modification can regulate CSH gel nucleation, resulting in a 55% increase in 28-day flexural strength compared to concrete.

[0018] A method for preparing scour-resistant high-strength solidified soil for submarine cables comprises the following steps: first, cement, fly ash, slag powder, and cellulose are weighed in a predetermined mass ratio and added sequentially into a mixing bucket, and stirred thoroughly and evenly; then, a mixture of a phenolic amine curing agent and modified oyster shell nanofibers is added into another mixing bucket in a predetermined ratio; then, an appropriate amount of seawater is slowly added and stirred for 300 seconds until the components become viscous; then, nano-silica, an auxiliary reinforcing agent, and distilled water are slowly added into the mixing bucket in a proportioned manner, stirring while adding until the final state becomes roughly viscous; finally, the first two groups of mixtures are added into a new mixing bucket, slowly stirred until evenly stirred, and then poured into a mold, cooled, and allowed to stand to obtain solidified soil.

[0019] The present invention also provides a construction process for submarine cable protection, comprising the following steps:

[0020] (1) Construction survey: The construction vessel arrives at the construction site and scans and inspects the relevant areas;

[0021] (2) Material arrival: transport the raw materials purchased from nearby manufacturers to the construction site according to the construction requirements, and analyze the components of various raw materials;

[0022] (3) In situ preparation of self-healing high-strength solidified soil: cement, fly ash, slag powder, cellulose, silane coupling agent, modified oyster shell nanofiber, bio-based dispersant, nano-silica, auxiliary reinforcing agent and seawater are mixed, and the mixing should be carried out according to the above-mentioned preparation method;

[0023] (4) Among them, in (3), it is considered that the addition of high-performance composite reinforcement materials will cause secondary erosion of the boundary with the original soil layer on the seabed. Therefore, during the laying of the submarine cable, the oyster shell nanofiber high-strength solidified soil is filled into the fiber geotextile. After filling, the geotextile is covered on the top of the submarine cable to form a rigid-flexible protection system. The flexibility of the geotextile and the rigidity of the solidified soil avoid the secondary erosion of the soil around the solidified soil, and make the submarine cable play a protective and anti-smashing effect; the method of laying the geotextile in sections saves construction costs and reduces the flow rate of seawater around the submarine cable.

[0024] (5) Post-quality inspection: Scan the solidified soil under underwater maintenance and regularly check the scouring of the solidified soil.

[0025] The beneficial effects of the present invention are:

[0026] Currently, the main forms of scour protection include physical methods such as riprap, sandbags, sand blankets, and flexible pads. First, these measures are expensive to construct and do not fundamentally change the properties of the covering soil. Second, riprap creates a dam effect, further increasing the probability of scour in the surrounding soil. While underwater grouting offers high strength, it consumes large amounts of cement, sand, and other resources, resulting in high costs. A high-strength, scour-proof, modified oyster shell nanofiber-cured soil for submarine cables is a controllable composite material whose mechanical properties, performance, and durability can be specifically improved through formula adjustments, and it is relatively inexpensive.

[0027] Compared with silt solidified soil, our submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil is prepared by mixing modified oyster shell nanofiber with cement, fly ash, etc., and adding admixtures such as anti-bleeding, anti-dispersion, micro-expansion, and anti-segregation. After adding seawater and stirring, it has excellent properties such as high fluidity, less water bleeding, no shrinkage, and no pollution to water quality and the surrounding environment. It can not only meet construction requirements, but also reduce economic costs and improve construction efficiency. The generated solidified soil is used in marine cable protection. It solidifies quickly underwater and has high strength. It does not disperse underwater during construction and has good anti-scour effect. The solidified soil can achieve self-leveling on the seabed. However, silt solidified soil has too little applicability and needs to be customized from a specific manufacturer. The transportation cost is high and the quality may not be guaranteed. The silt on the seabed has completely different properties due to the influence of regionality. Therefore, it cannot be used in submarine cable protection applications.

[0028] The addition of modified oyster shell nanofibers to our solidified soil offers numerous advantages, including high interfacial bonding strength, low cost, and low carbon footprint. The surface nanogrooves of the oyster shell mechanically anchor the cement hydration products, resulting in high modulus and toughness. During the formation process, the oyster shells possess a helical arrangement of biogenic calcium carbonate, resulting in a flexural strength three times greater than that of synthetic calcium carbonate. The natural organic matrix also enhances toughness. Modification modifies the nucleation of the CSH gel, resulting in a 55% increase in 28-day flexural strength compared to concrete.

[0029] Compared to cement without silane coupling agents, adding silane coupling agents can reduce production costs, improve durability and crack resistance, and produce a lightweight, high-strength mixture with good water stability, easy construction, and strong adaptability. Furthermore, silane coupling agents can reduce cement's carbon emissions, making it more environmentally friendly.

[0030] In response to the above requirements, after a large number of experiments to optimize the proportions, the optimal proportion of high-strength solidified soil was obtained. Its extremely low water permeability can well ensure the safety and durability of the structure. The outstanding feature of the present invention is first of all the use of seawater to prepare high-strength solidified soil. Because seawater resources are abundant and easy to obtain for seaside construction, the cost of high-performance composite reinforcement materials can be significantly reduced, which has significant economic and environmental benefits. Secondly, oyster shells are wasted in large quantities at the seaside and in the catering industry. Based on the principle of waste recycling, they are modified and reinforced to make nano-scale fibers for use in solidified soil to enhance the strength and toughness of the soil; thirdly, fly ash is the largest single source of industrial solid waste pollution in my country. It is easy to obtain locally and is low in price. It can not only protect the environment and realize the recycling of solid waste, but also significantly reduce manufacturing costs. The construction process adopts the integrated construction of submarine cable solidified soil, which greatly speeds up the construction process. At the same time, an interval laying method is adopted to reduce the impact of excessive underwater flow rate on its scouring.

[0031] In summary, the present invention has the following advantages:

[0032] High strength, good stability, and strong scour resistance: This composite material achieves high strength and scour resistance, and through improved construction techniques, a rigid and flexible scour prevention system is formed. For submarine cables already in service, construction can be continued via pump-and-blow fill, with the material simply covering the soil above.

[0033] High environmental value: The heavy metal content of the materials used in this solidified soil meets the requirements of the "Marine Environmental Protection Law of the People's Republic of China," promulgated on October 25, 2023. Furthermore, the heavy metal ions in the materials are not easily lost to the ocean due to the action of the solidifying agent. Fly ash has a good adsorption effect on heavy metal ions such as As3+, Hg2+, Pb2+, Cu2+, Ni2+, and Zn2+, with a metal ion removal rate of 40% to 90%. Compared with other materials, fly ash has a significant advantage in this respect.

[0034] The construction is convenient and the construction period is short: firstly, the raw materials of seawater, oyster shells and fly ash are easy to obtain and do not need to be transported over long distances like silt, which greatly shortens the construction period; secondly, the high fluidity of these materials is utilized and they are pumped into the geotextile by means of pumping and blowing, and then transported to the top of the submarine cable covering, which greatly reduces the construction period.

[0035] Low cost and high economic benefit: The present invention provides a submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil, which is made of cement, fly ash, slag powder, and modified oyster shell nanofiber as main materials, with other added mixed proportions. Fly ash is easy to purchase locally, and a certain amount of seawater is added at the construction site. It can be used after stirring evenly, with a short construction period and high economic benefit. The lower material cost is specifically reflected in the fact that the current market price of Class I fly ash is maintained at 140-160 yuan / ton, the current market price of oyster shells is 70-100 yuan / ton, the current market price of dry mortar is generally 260-285 yuan / ton, and the market price of the slag powder S95 we use is 360-400 yuan / ton. The cost of other anti-scour materials made of cement, lime, mineral powder and other materials is also higher than fly ash, and the market price of lime is currently between 550-700 yuan / ton. Regarding the use of silt as a material, the market price of silt is indeed much lower than what we use, at around 80-100 yuan per ton. However, its transportation cost is high and is greatly affected by regional characteristics. The mechanical properties of silt materials vary greatly from region to region, which can easily affect the mechanical properties of the materials used. Therefore, in comparison, fly ash has a higher cost-effectiveness than other materials such as silt. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1 This is the experimental device mentioned in Example 6 of the present invention. Specific embodiment 1

[0039] The invention discloses a high-strength scour-resistant modified oyster shell nanofiber solidified soil for submarine cables, which is mainly composed of cement, fly ash and modified oyster shell nanofiber. The mass percentages of the solidifying agent components are as follows: 30% cement, 20% fly ash, 32% slag powder, 2% cellulose, 0.5% silane coupling agent, 8% modified oyster shell nanofiber, 1% bio-based dispersant, 5% nano-silica and 1.5% auxiliary reinforcing agent.

[0040] According to this mix ratio, solidified soil was prepared by adding 100g of coupling agent per cubic meter of fly ash at a moisture content of 0.9%. After proper stirring, the average fluidity reached 20.8cm within half an hour, making it pumpable and preventing dispersion during underwater grouting. After grouting to the bottom of the water, the solidified soil was not displaced by the water flow at a velocity of 0.015m / s. The solidified soil was molded into a 70*70*70mm test mold. After demolding for two days and then underwater curing, its compressive strength was measured to be 157kPa after 7 days, 225kPa after 14 days, and 374kPa after 28 days.

[0041] The cohesion C detection method is: use a direct shear apparatus to measure the shear strength of the ring knife specimen, draw a shear strength straight line, and the intercept of the straight line with the y-axis is the cohesion C.

[0042] The method for testing the loss of self-healing, high-strength solidified soil is as follows: Place a 1500mL container at the bottom of a bucket and fill the bucket with water to a height of 500mm. Mix 2kg of solidified soil and pour it freely from the water surface into the container, ensuring that it completely enters the container without spilling. Let it sit for 5 minutes. Lift the container from the water, drain any water remaining on top of the solidified soil, and weigh it.

[0043] The suspended matter content test method is as follows: Add 800mL of water to a 1000mL beaker, then divide 500g of solidified soil into 10 equal portions. Use a hand shovel to slowly drop each portion of solidified soil onto the water surface within 10 to 20 seconds. Let the beaker stand for 3 minutes. Use a pipette to gently draw 600mL of water from the beaker within 1 minute, being careful not to inhale the solidified soil that was poured in. The drawn-out water serves as the test sample and is promptly tested.

[0044] The detection of indicators is as follows, the same below:

[0045] Table 1 Performance indicators of high-strength solidified soil prepared

[0046]

[0047] Example 1 is a demonstration of the working performance of the self-healing high-strength solidified soil under water; Specific embodiment 2

[0049] The high-strength solidified soil of this embodiment includes the following raw materials in percentage by mass: cement: 37.5%, fly ash: 25%, mineral powder: 35%, bio-based dispersant: 1%, silane coupling agent: 0.5%, and auxiliary reinforcing agent: 1%.

[0050] Table 2 Performance indicators of high-strength solidified soil prepared

[0051]

[0052] Example 2 shows the performance indicators without adding modified oyster shell nanofibers and nano-silica. Specific embodiment 3

[0054] The high-performance composite reinforcement material of this embodiment includes the following raw materials in percentage by mass: cement: 30%, fly ash: 25%, mineral powder: 34%, modified oyster shell nanofiber: 8.5%, bio-based dispersant: 1%, silane coupling agent: 0.5%, and auxiliary reinforcement 1%.

[0055] Table 3 Performance indicators of high-strength solidified soil prepared

[0056]

[0057] Example 3 adds modified oyster shell nanofibers based on Example 2, which slightly improves the cohesion of the high-strength solidified soil and reduces the loss ratio of the high-strength solidified soil, thereby achieving a certain water exudation capacity and reducing loss. Specific embodiment 4

[0059] The invention discloses a scour-resistant solidifying soil for submarine cables, which is composed of fly ash and a curing agent. The curing agent comprises the following components by weight: 30% cement, 22% fly ash, 38% slag powder, 0.5% thickener, 2% cellulose, 0.5% phenolic amine curing agent, 5% polyethylene glycol, 1% anti-dispersant, and 1% water reducer.

[0060] ① When the modified oyster shell nanofiber content was 30% by weight of cement (cement content of 350kg / m³), a 70*70*70mm test mold was formed into the solidified soil. After two days of demolding and underwater curing, the compressive strength was measured to be 157kPa at 7 days, 225kPa at 14 days, and 374kPa at 28 days. The flexural strength was 4.2MPa at 7 days, 4.8MPa at 14 days, and 8.1MPa at 28 days.

[0061] When the modified oyster shell nanofiber content was 40% of the cement weight (cement content was 350 kg / m³), a 70 x 70 x 70 mm test mold was formed from the solidified soil. After two days of demolding and underwater curing, the compressive strength was measured to be 160 kPa at 7 days, 228 kPa at 14 days, and 380 kPa at 28 days. The flexural strength was 4.2 MPa at 7 days, 4.8 MPa at 14 days, and 8.1 MPa at 28 days.

[0062] ③ When the modified oyster shell nanofiber content was 50% by weight of cement (cement content of 350 kg / m³), a 70*70*70 mm test mold was formed into the solidified soil. After two days of demolding and underwater curing, the compressive strength was measured to be 154 kPa at 7 days, 226 kPa at 14 days, and 372 kPa at 28 days. The flexural strength was 4.8 MPa at 7 days, 5.5 MPa at 14 days, and 8.8 MPa at 28 days. Specific embodiment 5

[0064] A scour-resistant cementing soil for submarine cables is composed of fly ash and a curing agent. The mass percentages of the curing agent are: 30% cement, 30% fly ash, 38.5% slag powder, 0.5% thickener, and 1% water reducer. This composition is used to consolidate seabed silt with a moisture content of 90%. 120g of this composition is added to every kilogram of silt and stirred evenly. The resulting silt-based cementing soil exhibits an average fluidity of 22cm within half an hour, making it pumpable and resistant to dispersion during underwater grouting. After grouting to the bottom, the cementing soil exhibits no movement at a flow rate of 0.015m / s. The cementing soil was molded into a 70*70*70mm test mold, removed from the mold after two days, and then cured underwater. The compressive strength was measured to be 87kPa after 7 days, 108kPa after 14 days, and 120kPa after 28 days. This compressive strength is significantly lower than that of modified oyster shell nanofiber-based cementing soil. Specific embodiment 6

[0066] The scouring test of the present invention is carried out in the laboratory using a scaled model. The high-strength solidified soil is poured into the scouring test box using a pipe. One end of the box is connected to the water inlet of the water pump and the other end is connected to the water reservoir. The connection between the water inlet and the pipe adopts a fan-shaped design to ensure that the high-strength solidified soil is fully scoured during water scouring. The experimental device is as follows: Figure 1 We conducted comparative tests on interval-thickened wave-type soil paving and normal soil paving. The high-strength stabilized soil used in the test was the same as the mix ratio in Example 1.

[0067] Three groups of samples were prepared for each group and three experiments were carried out in sequence. The water flow rate was controlled by a water pump. In the first group, when the water flow rate exceeded 3.56m / s, the shear stress on the surface of the self-healing high-strength solidified soil of the normal paving of Example 1 was greater than the starting shear stress, resulting in slight sediment start-up on the surface of the solidified soil; when the water flow rate exceeded 4.12m / s, the shear stress on the surface of the high-strength solidified soil of the interval paving of Example 1 was greater than the starting shear stress, resulting in slight sediment start-up on the surface of the solidified soil; in the second group, when the water flow rate exceeded 3.69m / s, the shear stress on the surface of the high-strength solidified soil of the normal full-length paving of Example 1 was greater than the starting shear stress. , resulting in slight sediment start-up on the surface of the solidified soil; when the water flow rate exceeds 4.07m / s, the shear stress on the surface of the high-strength solidified soil of Example 1 with interval paving is greater than the starting shear stress, resulting in slight sediment start-up on the surface of the solidified soil; the third group, when the water flow rate exceeds 3.63m / s, the shear stress on the surface of the high-strength solidified soil of Example 1 with normal paving is greater than the starting shear stress, resulting in slight sediment start-up on the surface of the solidified soil; when the water flow rate exceeds 4.11m / s, the shear stress on the surface of the high-strength solidified soil of Example 1 with interval paving is greater than the starting shear stress, resulting in slight sediment start-up on the surface of the solidified soil. The test shows that the present invention has the ability to resist the scouring of water flow of about 4.1m / s without a large amount of soil loss, and has good anti-scouring performance. Taking all factors into consideration, the anti-scouring effect of interval paving is obviously better than that of normal full-length paving. Specific embodiment 7

[0069] This embodiment is mainly used for comparison to illustrate the selection of the optimal ratio and the optimal material.

[0070] The first group: modified oyster shell nanofiber high-strength solidified soil includes the following raw materials in percentage by mass: cement: 30%, fly ash: 20%, mineral powder: 30%, cellulose: 1%, bio-based dispersant: 1%, modified oyster shell nanofiber: 10%, nano-silica: 6%, silane coupling agent: 0.5%, auxiliary reinforcing agent: 1.5%.

[0071] The second group: modified oyster shell nanofiber high-strength solidified soil includes the following raw materials in percentage by mass: cement: 35%, fly ash: 23%, mineral powder: 28%, cellulose: 1%, bio-based dispersant: 0.5%, modified oyster shell nanofiber: 8%, nano-silica: 3%, silane coupling agent: 0.5%, auxiliary reinforcing agent: 1%.

[0072] The third group: The composite materials currently used in engineering projects include the following raw materials in percentage by mass: cement: 71.35%, mineral powder: 27.65%, anti-dispersant: 0.5%, water reducing agent: 0.5%.

[0073] Table 4 Performance indicators of the self-healing high-strength solidified soil prepared in the first group

[0074]

[0075] Table 5 Performance indicators of the self-healing high-strength solidified soil prepared in the second group

[0076]

[0077] Table 6 Performance indicators of the self-healing high-strength solidified soil prepared in the third group

[0078]

[0079] This example demonstrates that the self-healing, high-strength solidified soil of the present invention, which utilizes cement and fly ash as binders, exhibits significantly greater strength, durability, and cohesion than cement alone, while also being more economical and environmentally friendly at a lower cost than cement-only binders. Furthermore, the present invention can be agitated with seawater, eliminating the need for fresh water and still meeting engineering requirements. The nanogrooves on the surface of the oyster shells within the solidified soil mechanically anchor the cement hydration products, resulting in high modulus and toughness, allowing for excellent adhesion to the overburden, preventing separation of the bonding layer from the solidified soil. Furthermore, the shells themselves provide a three-dimensional network structure, ensuring the required strength in the later stages.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the principle and scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. A submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil, characterized by: The moisture content of fly ash is controlled at 0.7% to 0.9%. The mass percentage of each component in the formula is: Cement 30-40%; Fly ash 20-40%; Slag powder 20-40%; Cellulose 0.5-3%; Silane coupling agent 0.4-0.5%; Modified oyster shell nanofibers 8-12%; Bio-based dispersant 0.5-1.5%; Nano silicon dioxide 3-5%; Auxiliary enhancer 1-2% The preparation method of the modified oyster shell nanofiber is: a. The collected discarded oyster shells were soaked in a 3% hydrogen peroxide solution for 24 hours at a solid-liquid ratio of approximately 1:5 to remove organic residues contained in the oyster shells; b. Then use ultrasonic cleaning with an ultrasonic frequency of 40kHz and a cleaning time of 30 minutes; c. After the oyster shells are dried naturally to remove moisture, the shells are placed in a crusher and broken into 1-3 cm fragments, and then placed in a ball mill and crushed to 100-200 mesh; d. The crushed oyster shells were treated with 0.5 M hydrochloric acid solution at a solid-liquid ratio of 1:10 and shaken in a 60 ° C water bath for 4 hours; e. Then put it into 5% sodium hydroxide solution, solid-liquid ratio 1:8, reflux at 90 ° C for 2 hours to remove residual protein, and then wash until neutral; f. Re-disperse in an ethanol solution containing 1% silane coupling agent and stir at 50°C for 40 minutes; g. Modified oyster shell nanofibers obtained by vacuum drying; The method for preparing the anti-scour self-healing high-strength solidified soil for submarine cables is characterized by: Preparation of the first component: First, cement, fly ash, slag powder, and cellulose are weighed in a predetermined mass ratio and added to a mixing barrel in sequence, and stirred thoroughly to obtain the first component; Preparation of the second component: Add the phenolic amine curing agent and modified oyster shell nanofiber mixture according to a predetermined ratio to another stirring bucket, slowly add an appropriate amount of seawater, and stir for 300 seconds until the component becomes viscous. This is to obtain the second component; Preparation of the first mixture: Slowly add nano-silica, auxiliary reinforcing agent and distilled water to the second component according to the proportion, stirring while adding, and finally the mixture is roughly viscous. At this time, the first mixture is obtained; Preparation of high-strength modified oyster shell nanofiber solidified soil: Add the first mixture and the first component into a mixing bucket, slowly stir until evenly mixed, pour into a mold, cool and let stand to obtain solidified soil.

2. The modified oyster shell nanofiber according to claim 1, characterized in that: The fiber diameter is controlled between 50-200nm and the length is 5-20um.

3. The high-strength solidified soil according to claim 1, characterized in that: The diameter of the modified oyster shell nanofibers is controlled between 50-200nm, matching the nanoscale of the cement hydration product CSH gel, forming a three-dimensional network structure. A single fiber can bridge multiple hydration product crystals, improving early strength. The residual CaCO3 in the fiber undergoes dynamic dissolution and precipitation in an alkaline environment: Provide heterogeneous nucleation sites for CSH gel; The hydrophilic groups on the fiber surface form a directional water molecule layer, which changes the contact angle from the original 65° to 35°, thereby accelerating the early hydration reaction of cement particles and significantly improving the early strength.

4. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1 is characterized by: The cement is 42.5 ordinary Portland cement.

5. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1 is characterized by: The fly ash is Grade I fly ash, with a specific surface area of ​​≥400m 2 / kg.

6. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1 is characterized by: The slag powder is S95 grade ultrafine mineral powder, and its specific surface area is ≥3000m2 / kg.

7. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1 is characterized by: The cellulose is hydroxypropyl methylcellulose.

8. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1 is characterized by: The main component of the silane coupling agent is gamma-aminopropyltriethoxysilane.

9. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1, characterized in that: The main component of the bio-based dispersant is a sulfonated polysaccharide derivative.

10. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1, characterized in that: The auxiliary enhancer is mainly composed of a specific complex of sodium gluconate and triethanolamine.

11. The submarine cable anti-scour modified oyster shell nanofiber high-strength solidified soil according to claim 1, characterized in that: The preparation method of the modified oyster shell nanofiber is: a. The collected discarded oyster shells were soaked in a 3% hydrogen peroxide solution for 24 hours at a solid-liquid ratio of approximately 1:5 to remove organic residues contained in the oyster shells; b. Then use ultrasonic cleaning with an ultrasonic frequency of 40kHz and a cleaning time of 30 minutes; c. After the oyster shells are dried naturally to remove moisture, the shells are placed in a crusher and broken into 1-3 cm fragments, and then placed in a ball mill and crushed to 100-200 mesh; d. The crushed oyster shells were treated with 0.5 M hydrochloric acid solution at a solid-liquid ratio of 1:10 and shaken in a 60 ° C water bath for 4 hours; e. Then put it into 5% sodium hydroxide solution, solid-liquid ratio 1:8, reflux at 90 ° C for 2 hours to remove residual protein, and then wash until neutral; f. Re-disperse in an ethanol solution containing 1% silane coupling agent and stir at 50°C for 40 minutes; g. Modified oyster shell nanofibers were obtained by vacuum drying.

12. A method for preparing the high-strength stabilized soil made of oyster shell nanofibers with anti-scour properties for submarine cables according to any one of claims 1 to 10, characterized in that: Preparation of the first component: First, cement, fly ash, slag powder, and cellulose are weighed in a predetermined mass ratio and added to a mixing barrel in sequence, and stirred thoroughly to obtain the first component; Preparation of the second component: Add the phenolic amine curing agent and modified oyster shell nanofiber mixture according to a predetermined ratio to another stirring bucket, slowly add an appropriate amount of seawater, and stir for 300 seconds until the component becomes viscous. This is to obtain the second component; Preparation of the first mixture: Slowly add nano-silica, auxiliary reinforcing agent and distilled water to the second component according to the proportion, stirring while adding, and finally the mixture is roughly viscous. At this time, the first mixture is obtained; Preparation of high-strength modified oyster shell nanofiber solidified soil: Add the first mixture and the first component into a mixing bucket, slowly stir until evenly mixed, pour into a mold, cool and let stand to obtain solidified soil. Note that the temperature and time must be strictly controlled during the alkali treatment stage to avoid unclean protein treatment that may lead to a decrease in fiber strength. The fiber surface must be fully moistened before surface modification.

13. The present invention also provides a construction process for submarine cable protection, comprising the following steps: (1) Construction survey: The construction vessel arrives at the construction site and scans and inspects the relevant areas; (2) Material arrival: transport the raw materials purchased from nearby manufacturers to the construction site according to the construction requirements, and analyze the components of various raw materials; (3) In situ preparation of high-strength stabilized soil: cement, fly ash, slag powder, cellulose, silane coupling agent, modified oyster shell nanofiber, bio-based dispersant, nano-silica, auxiliary reinforcing agent and seawater are mixed, and the mixing should be carried out according to the above-mentioned preparation method; (4) In (3), it is considered that the addition of high-performance composite reinforcement materials will cause secondary erosion of the boundary with the original soil layer on the seabed. Therefore, during the laying of the submarine cable, the submarine cable and soil are integrated and constructed at the same time. After the integrated construction of the submarine cable and the upper covering soil is completed, the pumping and filling device is used again to thicken the sections so that the upper covering soil appears wavy, thereby reducing the flow rate of the seabed water and reducing the erosion of the upper covering soil by the water flow. (5) Post-quality inspection: Scan the solidified soil under underwater maintenance and regularly check the scouring of the solidified soil.

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