Underwater soil anti-scour enhancement and self-repair treatment agent and preparation method thereof

Abstract

The present invention belongs to the technical field of water and soil engineering materials, and specifically discloses an underwater soil anti-scour enhancement and self-repairing treatment agent and a preparation method thereof. The underwater soil anti-scour enhancement and self-repairing treatment agent includes a hydrogel treatment agent and a polyvinyl alcohol insulating layer, and the polyvinyl alcohol insulating layer is wrapped on the outer surface of the hydrogel treatment agent; the raw material components of the hydrogel treatment agent include polyacrylamide, sodium alginate and calcium chloride. The present invention utilizes the interaction between polyacrylamide, sodium alginate and calcium chloride to improve the ability of the hydrogel protective layer to resist the scouring effect of water flow, and has a certain self-filling and repairing function for low-lying scour pits; at the same time, a water-soluble polyethylene insulating layer is used to wrap the hydrogel, so that the treatment agent can automatically move to the local area with severe scour, achieve targeted treatment effects, reduce the waste of treatment agents, and reduce problems such as inaccurate treatment positions caused by unreasonable selection of treatment material scattering areas.

Description

Technical Field

[0001] The present invention belongs to the technical field of water and soil engineering materials, and particularly relates to an underwater soil anti-scour enhancement and self-repair treatment agent and a preparation method thereof. Background Art

[0002] Scour of underwater foundations of hydraulic structures is a major threat to engineering safety. The driving force behind scour is the erosive shearing effect of water flow. Water scours and carries sediment from structures such as riverbeds, embankments, offshore wind turbine pile foundations, and bridge piers. Scour can be categorized as natural, general, and localized. Localized scour typically occurs when water flow is affected by underwater structures, causing changes in the flow field near the structures and the formation of scour pits around them. Localized scour is common in projects such as offshore wind turbine and bridge pile foundations, seawalls, and submarine pipelines. Pipelines laid on the seabed can experience scour near them due to wave and current action, leading to partial overhangs. Offshore wind turbine and bridge foundations alter the hydrodynamic conditions around the foundations, generating eddies and increasing shearing action. This leads to localized scour of sediment near the structures. This not only reduces the buried depth of the foundation structure, reducing its bearing capacity, but also alters the lateral stress state, adversely affecting the stability of the superstructure.

[0003] Based on the principles of protection, local scour protection measures for underwater structures can be divided into active protection (modifying hydrodynamic conditions to reduce the shear effect of water flow) and passive protection (improving the scour resistance of the foundation soil around the structure). Common examples of the former include sandbag backfill for submarine pipeline span protection, retaining ring protection for pile foundations, and sacrificial pile protection in front of piers. These methods are costly and affect the bearing capacity of the structure. Common passive protection methods include riprap, sand blankets, concrete briquettes, and soil treatment. However, these methods require the preparation of large amounts of treatment materials before implementation, resulting in complex construction processes and difficult on-site implementation. The scattering area is difficult to accurately control, making targeted protection impossible. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes an underwater soil anti-scour enhancement and self-repairing agent and a preparation method thereof. The agent can be moved by water flow to areas experiencing local scour or severe scour for targeted adaptive treatment, achieving active treatment by automatically reducing areas prone to erosion and scour. The hydrogel produced by the water absorption reaction has an adhesive and fixation effect on suspended sediment in the water, and has a self-repairing effect on areas that have already been scoured.

[0005] The inventive concept of the present invention is as follows: Addressing the shortcomings of existing local scour protection measures, the present invention proposes a soil anti-scour and self-repair treatment agent primarily composed of polymers. The raw material components of this treatment agent primarily include polyacrylamide, sodium alginate, calcium chloride, and polyvinyl alcohol. The primary function of polyacrylamide, sodium alginate, and calcium chloride is to form a hydrogel protective layer on the surface of the sand bed and scour pit. With these three substances as the primary reactants, the hydrogel adhesive effect is utilized to enhance the erosion and scour resistance of the surface sand and improve the threshold conditions for soil particle activation in the bed sand. The polyvinyl alcohol primarily serves as an insulating layer to control the release time, encapsulating the internal substances. The polyvinyl alcohol insulating layer ensures that the polyacrylamide, sodium alginate, and calcium chloride mixture remains stable in water for a certain period of time after being immersed in water, preventing water absorption and reaction release. Furthermore, the polyacrylamide, sodium alginate, and calcium chloride are formed into cylindrical granules through powder briquetting and other methods, and then coated with polyvinyl alcohol to form a cylindrical granular treatment agent. The treatment agent can control the timing of the reaction and release of the internal substances by controlling the thickness of the polyvinyl alcohol. After the treatment agent enters the water, it is gathered in the low-lying area where local scouring occurs under the action of water flow. When the release time point is reached, the internal reactants absorb water and react in the scouring pit to release and form hydrogel. The solution-like hydrogel infiltrates into the interior of the bed sand and takes root in the soil below the bed to resist the lateral scouring effect of the water flow. Due to its own strong bonding effect, the hydrogel can bond the suspended sediment carried by the water flow, and form a soil-polymer mixture with the moving sediment and surface soil carried by the water flow, gradually filling the low-lying areas with severe scouring, forming a protective layer on the surface of the sand bed, and curbing the scouring pit. Development, and filling and repairing of the scouring pits, not only overcomes the defects of inaccurate application location of protective materials caused by the difficulty in controlling the scattering area, but also avoids the problems of large amount of waste of scattering treatment materials and low efficiency, large amount of early scattering treatment materials and complicated construction procedures. The bed protection layer formed by this treatment method is a flexible layer with certain flowability, which can adapt to the deformation of the bed surface, and is different from the cement solidified soil treatment method which cannot produce consolidation effect with the surrounding soil after solidification. It remains in a hydrogel state in water and can be bonded and fixed with the surrounding contactable soil.

[0006] To solve the above technical problems, the first aspect of the present invention provides an underwater soil anti-scour enhancement and self-repair treatment agent, comprising a hydrogel treatment agent and a polyvinyl alcohol insulation layer, wherein the polyvinyl alcohol insulation layer is wrapped around the outer surface of the hydrogel treatment agent; the raw material components of the hydrogel treatment agent include polyacrylamide, sodium alginate and calcium chloride.

[0007] Specifically, polyacrylamide, sodium alginate, and calcium chloride serve as the primary components of the hydrogel treatment agent, primarily used to form a hydrogel protective layer on the riverbed surface and to adhere and secure sand carried by the water flow to the surface. The polyacrylamide forms a hydrogel protective layer on the riverbed surface. Due to its smooth surface, the frictional resistance of water flowing through it is reduced, and its viscous properties can slow the movement of sediment particles and stabilize heavier sediment. The ease of sediment movement on the underwater bed affects the development and evolution of local scour pits, leading to rapid scour and sedimentation. The adhesive effect of the polyacrylamide hydrogel can be used to secure a certain thickness of sediment on the surface of areas prone to local scour, effectively alleviating local scour, increasing resistance to the movement of bedload sediment, and maintaining its stability, thereby achieving self-repair and enhancing the anti-scour capacity of local scour pits.

[0008] Sodium alginate and calcium chloride are primarily used to enhance the strength of the polyacrylamide hydrogel, strengthening its resistance to shear and tensile deformation caused by water flow, and making the resulting hydrogel protective layer more stable. After the three solid substances, polyacrylamide, sodium alginate, and calcium chloride, are dissolved in water, the sodium alginate first cross-links with some calcium ions to form a calcium alginate gel. While this calcium alginate gel has high mechanical strength, its poor rheological properties make it difficult for it to penetrate the sand surface and into the sand layer. Furthermore, because the sodium alginate reacts too quickly with some calcium ions, the reaction can be incomplete and insufficient. Polyacrylamide dissolves to form a polyacrylamide aqueous solution, which reacts with another part of the calcium ions. By reducing the electrostatic repulsion between the molecular chains of the polyacrylamide aqueous solution, the molecular chains shrink, resulting in a decrease in the viscosity of the solution, which facilitates the penetration of polyacrylamide into the sand and forms an anti-scour protective layer with the sand on the bed surface to inhibit the movement of sediment and scour development on the bed surface. At the same time, calcium ions and the polyacrylamide aqueous solution will produce a moderate cross-linking structure, which makes the polyacrylamide have a more stable gel network structure. With the complete reaction, part of the polyacrylamide penetrates into the pores of the sand and adheres to the sand particles. The weight of the sand particles increases the weight of the hydrogel wrapped in the mixed sand. The increase in floating weight will also inhibit erosion and scour. Under the action of osmotic pressure, the calcium ions combined with the polyacrylamide solution will diffuse into the external water body, and the viscosity of the polyacrylamide solution will partially recover.

[0009] Polyvinyl alcohol is the key to achieving precise treatment of local scour pits and severely low-lying areas by the treatment agent. The outer layer of polyvinyl alcohol of the present invention is a uniform thin layer, which is used for delayed release and acts as an "ignition fuse". It can keep the treatment agent stable in the water for a period of time, so that the treatment agent has sufficient time to gather in low-lying areas and scour pits.

[0010] In some embodiments of the present invention, the raw material components of the hydrogel treatment agent include, by weight, 60-72 parts of polyacrylamide, 20-28 parts of sodium alginate, and 8-12 parts of calcium chloride.

[0011] In some embodiments of the present invention, the particle sizes of the polyacrylamide, sodium alginate and calcium chloride are less than 0.05 mm.

[0012] In some embodiments of the present invention, the hydrogel treatment agent is cylindrical, and the diameter and height of the cylinder are both 1-1.5 cm. The cylindrical granular treatment agent is conducive to moving to the low-lying scour pit with severe scour under the action of bottom water flow.

[0013] In some embodiments of the present invention, the thickness of the polyvinyl alcohol insulating layer is 0.4-2 mm, preferably 0.8-2 mm. The thickness of the polyvinyl alcohol insulating layer determines the time the treatment agent can be stably present on the surface of the riverbed or seabed.

[0014] The second aspect of the present invention provides a method for preparing the above-mentioned underwater soil anti-scour enhancement and self-repair treatment agent, comprising the following steps:

[0015] acrylamide, sodium alginate and calcium chloride are mixed and pressed into shape to obtain a hydrogel treatment agent;

[0016] Mixing polyvinyl alcohol with water and a defoamer, and heating to dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol hot melt;

[0017] The hydrogel treatment agent is immersed in the polyvinyl alcohol hot melt solution to wrap the polyvinyl alcohol on the outer surface of the hydrogel treatment agent, and then dried to obtain the underwater soil anti-scour enhancement and self-repair treatment agent.

[0018] Specifically, when preparing the underwater soil anti-scour enhancement and self-repair treatment agent of the present invention, acrylamide, sodium alginate and calcium chloride are evenly mixed, and then the dry powder mixture is pressed into cylindrical powder compressed particles of the required size using a powder tableting device to prepare a hydrogel treatment agent. Polyvinyl alcohol and water are prepared according to a certain composition mass fraction to prepare a wrapping insulation layer. Since polyvinyl alcohol is prone to bubbles during the temperature rise and dissolution process, it is necessary to add a defoaming agent to reduce the bubbles in the polyvinyl alcohol hot melt to prepare a polyvinyl alcohol hot melt. Finally, the cylindrical hydrogel treatment agent is placed in the polyvinyl alcohol hot melt, and the compressed particles are fully contacted with the polyvinyl alcohol hot melt by soaking and stirring, so that a thin layer of hot melt polyvinyl alcohol is coated on the surface of the particles. After drying, the treatment agent product is obtained, and the thickness of the polyvinyl alcohol insulation layer is controlled by multiple soaking and drying processes.

[0019] In some embodiments of the present invention, the defoaming agent comprises isooctyl alcohol.

[0020] In some embodiments of the present invention, the mass ratio of the polyvinyl alcohol to water is 1:(1.5-2.5).

[0021] In some embodiments of the present invention, the mass ratio of the polyvinyl alcohol to the defoaming agent is (10-30):1.

[0022] In some embodiments of the present invention, the heating temperature is 90-95°C.

[0023] In some embodiments of the present invention, the heating time is 30-50 minutes.

[0024] In some embodiments of the present invention, the drying temperature is 55-65°C.

[0025] In some embodiments of the present invention, the drying time is 1-3 hours.

[0026] The third aspect of the present invention provides the use of the above-mentioned underwater soil anti-scour enhancement and self-repair treatment agent in underwater local scour protection.

[0027] Specifically, the finished treatment agent is stable in dry conditions. During application, the agent simply needs to be sprinkled onto the treatment area. The cylindrical granules can remain stable on the riverbed or seabed for a period of time, controlled by the thickness of the polyethylene. During this period, the cylindrical granules can be driven by bottom water flow to move toward low-lying scour pits with severe scour. Upon release, the reactants—polyacrylamide, sodium alginate, and calcium chloride—react with water to form a hydrogel, enhancing the underwater soil's resistance to scour and enabling self-repair.

[0028] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:

[0029] (1) The present invention utilizes polyacrylamide to form a hydrogel solution with strong adhesiveness and high viscosity after being dissolved in water. The hydrogel with strong adhesive force protects the surface of the sand bed, and utilizes the ionic interaction between polyacrylamide, sodium alginate and calcium chloride to improve the adhesiveness and tensile strength of the polyacrylamide hydrogel, thereby improving the ability of the hydrogel protective layer to resist the scouring effect of water flow. The hydrogel protective layer can be attached and bonded by the suspended sediment and bed sediment moving near the bed surface, and mixed and wrapped with the sediment carried by the water flow and the sand on the bed surface to form a flexible anti-scouring protective layer on the surface of the bed surface, which has a certain self-filling and repairing function for low-lying scour pits.

[0030] (2) The present invention uses a water-soluble polyethylene insulating layer to wrap the hydrogel, so that the treatment agent can be stably present in the sand bed for a certain period of time. During this period, the treatment agent can automatically move to the area where local scouring is severe, thereby greatly improving the use efficiency of the treatment agent, achieving targeted treatment effects, reducing the waste of the treatment agent, and reducing problems such as inaccurate treatment positions caused by unreasonable selection of treatment material scattering areas. Conventional measures such as riprap, protective layers, and solidified soil for scattering stabilizing materials can achieve backfill processing in scouring areas, but as time goes by, scouring will still occur in scouring locations. The treatment agent of the present invention has the ability to fix and adhere to the mobile sand on the bed surface, and has a certain degree of scouring self-repair, which can effectively curb or delay the development of scouring. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a physical picture of the hydrogel treating agent prepared in Example 1 of the present invention;

[0032] Figure 2 This is a physical picture of the treatment agent prepared in Example 1 of the present invention;

[0033] Figure 3 This is a comparison diagram of the treatment agent prepared in Example 2 of the present invention before and after release in water;

[0034] Figure 4 This is a comparison chart of the jet scour pit depths of the treatment agents prepared in Examples 1-3 of the present invention, Comparative Examples 1-2, and the blank control group. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the examples to facilitate understanding of the present invention by those skilled in the art. It is necessary to point out that the examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned invention should still fall within the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0036] Example 1

[0037] An underwater soil anti-scour enhancement and self-repair treatment agent comprises a hydrogel treatment agent and a polyvinyl alcohol insulation layer, wherein the polyvinyl alcohol insulation layer is wrapped on the outer surface of the hydrogel treatment agent.

[0038] The raw materials of the hydrogel treatment agent include, by weight, 72 parts polyacrylamide, 20 parts sodium alginate, and 8 parts calcium chloride. The particle sizes of the polyacrylamide, sodium alginate, and calcium chloride are all less than 0.05 mm. The thickness of the polyvinyl alcohol insulation layer is 0.4 mm.

[0039] The preparation method of the above-mentioned underwater soil anti-scour enhancement and self-repair treatment agent comprises the following steps:

[0040] (1) Weigh polyacrylamide, sodium alginate and calcium chloride according to the mass ratio, stir them evenly, and then use a powder tableting device to press the powder mixture into cylindrical block powder compressed particles with a diameter of 1-1.5 cm and a height of 1-1.5 cm to obtain a hydrogel treatment agent, such as Figure 1 As shown;

[0041] (2) Polyvinyl alcohol (PVA217) and deionized water were stirred and mixed uniformly at a mass ratio of 1:2, and isooctyl alcohol was added (the mass ratio of polyvinyl alcohol to isooctyl alcohol was 20:1), and heated at 90-95°C for 40 minutes to completely dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol hot melt;

[0042] (3) The hydrogel treatment agent particles prepared in step (1) are placed in the polyvinyl alcohol hot melt solution prepared in step (2), and the surface of the particles is coated with a thin layer of hot melt polyvinyl alcohol by soaking and stirring. The particles soaked and coated with polyvinyl alcohol are then dried in a 60°C dry heat air drying device for 2 hours. The thickness of the outer polyvinyl alcohol insulating layer is controlled by two soaking and drying processes to obtain the underwater soil anti-scour enhancement and self-repair treatment agent of this embodiment, as shown in FIG. Figure 2 shown.

[0043] Example 2

[0044] An underwater soil anti-scour enhancement and self-repair treatment agent comprises a hydrogel treatment agent and a polyvinyl alcohol insulation layer, wherein the polyvinyl alcohol insulation layer is wrapped on the outer surface of the hydrogel treatment agent.

[0045] The raw materials of the hydrogel treatment agent include, by weight, 60 parts polyacrylamide, 28 parts sodium alginate, and 12 parts calcium chloride. The particle sizes of the polyacrylamide, sodium alginate, and calcium chloride are all less than 0.05 mm. The thickness of the polyvinyl alcohol insulation layer is 0.4 mm.

[0046] The preparation method of the underwater soil anti-scour enhancement and self-repair treatment agent of Example 2 is the same as that of Example 1.

[0047] Example 3

[0048] An underwater soil anti-scour enhancement and self-repair treatment agent comprises a hydrogel treatment agent and a polyvinyl alcohol insulation layer, wherein the polyvinyl alcohol insulation layer is wrapped on the outer surface of the hydrogel treatment agent.

[0049] The raw materials of the hydrogel treatment agent include, by weight, 65 parts polyacrylamide, 25 parts sodium alginate, and 10 parts calcium chloride. The particle sizes of the polyacrylamide, sodium alginate, and calcium chloride are all less than 0.05 mm. The thickness of the polyvinyl alcohol insulation layer is 0.4 mm.

[0050] The preparation method of the underwater soil anti-scour enhancement and self-repair treatment agent of Example 3 is the same as that of Example 1.

[0051] Comparative Example 1

[0052] The only difference between Comparative Example 1 and Example 1 is that the raw material components of the hydrogel treating agent are different. The raw material components of the hydrogel treating agent of Comparative Document 1 include, by weight, 15 parts of polyacrylamide, 60 parts of sodium alginate, and 25 parts of calcium chloride.

[0053] Comparative Example 2

[0054] The only difference between Comparative Example 2 and Example 1 is that polyacrylamide, a raw material for preparing the hydrogel treating agent, is replaced by sodium polyacrylate.

[0055] Performance Testing

[0056] 1. Free up time

[0057] The underwater soil anti-scour enhancement and self-repairing agent of Example 2 was used, and the preparation method of the underwater soil anti-scour enhancement and self-repairing agent of Example 2 was referred to, except that the number of wrapping times in the soaking and drying process in step (3) was changed to 2 times, 3 times and 4 times respectively to change the thickness of the outer polyvinyl alcohol insulating layer; then the prepared underwater soil anti-scour enhancement and self-repairing agent was placed in water, and the release time of the polyvinyl alcohol insulating layer was recorded. The results are shown in Table 1.

[0058] Table 1: Relationship between different wrapping times, wrapping layer thickness, and water release time

[0059] Number of packages 1 2 3 4 Wrapping layer thickness (mm) 0.4 0.8 1.3 1.8 Release time (h) 7 10 12.5 14.5

[0060] Figure 3 This is a comparison chart of the treatment agent prepared in Example 2 before and after release in water, Figure 3 As shown in Table 1, the release time of the polyvinyl alcohol insulation layer of the underwater soil anti-scour enhancement and self-repairing agent is positively correlated with the number of wrappings and the thickness of the wrapping layer. During application, the time required for the agent to migrate can be appropriately adjusted based on actual needs, such as different water flow conditions and the rate at which the agent migrates and accumulates underwater in low-lying areas and scour pits.

[0061] 2. Anti-corrosion performance

[0062] The scouring test was carried out by using Fujian sand and the hydrogel treatment agent prepared in the above Examples 1-2 and Comparative Examples 1-2 at a mass ratio of 100:1. The usage amount converted into area was 1.325 kg / m 2 .

[0063] The erosion and scouring test of Fujian sand was carried out using a jet scouring test device. The soil erosion process was described using the excess shear stress model using formula (1). Among them: the critical shear stress of soil and the erosion rate coefficient are characteristic parameters describing the soil's anti-erosion properties. The critical shear stress is the threshold condition for soil scouring under the shear action of water flow. When the soil is pushed by water flow and exceeds the critical shear stress of soil, the surface soil begins to erode. The larger the value of this parameter, the more difficult the soil is to scour. The erosion rate coefficient reflects the speed of soil erosion and scouring. The larger the value, the faster the scouring develops. The effects of different raw material components in the treatment agent on the anti-erosion properties of sand are compared. The results are as follows: Figure 4 and as shown in Table 2.

[0064] ε r =k d (τ-τ c ) (1)

[0065] Where: τ is the shear stress acting on the soil surface, Pa; τ c is the critical shear stress of soil erosion, Pa; k d is the erosion rate coefficient or erodibility coefficient, cm 3 / (N·s).

[0066] Table 2: Fujian sand anti-erosion characteristic parameters

[0067] experimental group Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Blank group Critical shear stress (Pa) 1.86 1.85 1.84 1.72 1.31 1.53 <![CDATA[Erosion rate coefficient cm 3 / (N·s)]]> 0.97 1.06 1.01 1.14 1.47 1.21

[0068] Depend on Figure 4 As shown in Table 2, from the analysis of the size of the scour pit formed by vertical submerged jet scouring, under the same jet velocity, jet nozzle diameter and jet height conditions, different proportions of polyacrylamide, sodium alginate and calcium chloride were used. Examples 1-3 (corresponding to Figure 4 a. Figure 4 b and Figure 4 c) The maximum scour depth of the scour pit is about 9 mm. The diameter of the scour pit of Example 3 is slightly close to that of Example 2. The diameters of the scour pits of Examples 2 and 3 are slightly larger than that of Example 1. Figure 4 d) The maximum scour pit depth is 13 mm, and the comparative example 2 ( Figure 4 e) The maximum scour pit depth was 22 mm, and the blank control group (Fujian sand without hydrogel treatment agent) Figure 4f) The maximum scour pit depth was 20 mm. Compared with the blank test group without the addition of the treatment agent, the scour resistance of the Fujian sand treated with the hydrogel treatment agent containing polyacrylamide was enhanced, and the degree of improvement was closely related to the mass fraction of each component of the treatment agent. When the polyacrylamide in the treatment agent was adjusted to sodium polyacrylate, the size of the scour pit formed increased, and the erosion resistance of the Fujian sand was weakened.

[0069] For those skilled in the art to which the present invention belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present invention, without having to resort to creative work. Therefore, based on the disclosure of the present invention, simple improvements made by those skilled in the art to the present invention should be within the scope of protection of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should fall within the scope of protection of the present invention.

Claims

1. An underwater soil anti-scour enhancement and self-repair treatment agent, characterized in that: It comprises a hydrogel treatment agent and a polyvinyl alcohol insulating layer, wherein the polyvinyl alcohol insulating layer is wrapped around the outer surface of the hydrogel treatment agent; The raw material components of the hydrogel treatment agent include, by weight: 60-72 parts of polyacrylamide, 20-28 parts of sodium alginate and 8-12 parts of calcium chloride; The thickness of the polyvinyl alcohol insulating layer is 0.4-2 mm.

2. The underwater soil anti-scour enhancement and self-repair treatment agent according to claim 1, characterized in that: The hydrogel treatment agent is cylindrical, and the diameter and height of the cylinder are both 1-1.5 cm.

3. A method for preparing the underwater soil anti-scour enhancement and self-repair treatment agent according to any one of claims 1 to 2, characterized in that: The following steps are involved: The polyacrylamide, sodium alginate and calcium chloride are mixed and pressed into shape to obtain a hydrogel treatment agent; Mixing polyvinyl alcohol with water and a defoamer, and heating to dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol hot melt; The hydrogel treatment agent is immersed in the polyvinyl alcohol hot melt solution to wrap the polyvinyl alcohol on the outer surface of the hydrogel treatment agent, and then dried to obtain the underwater soil anti-scour enhancement and self-repair treatment agent.

4. The method for preparing the underwater soil anti-scour enhancement and self-repairing agent according to claim 3, characterized in that: The defoaming agent includes isooctyl alcohol.

5. The method for preparing the underwater soil anti-scour enhancement and self-repairing agent according to claim 3 or 4, characterized in that: The mass ratio of the polyvinyl alcohol to water is 1:(1.5-2.5); and / or the mass ratio of the polyvinyl alcohol to the defoaming agent is (10-30):

1.

6. The method for preparing the underwater soil anti-scour enhancement and self-repair treatment agent according to claim 3, characterized in that: The heating temperature is 90-95° C.; and / or the heating time is 30-50 minutes.

7. The method for preparing the underwater soil anti-scour enhancement and self-repair treatment agent according to claim 3, characterized in that: The drying temperature is 55-65° C.; and / or the drying time is 1-3 hours.

8. Use of the underwater soil anti-scour enhancement and self-repair treatment agent according to any one of claims 1 to 2 in local scour protection of underwater structures.

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