Underwater soil anti-scouring enhancing and self-repairing treating agent and preparation method thereof

Abstract

The invention belongs to the technical field of water and soil engineering materials, and particularly discloses an underwater soil anti-scouring enhancing and self-repairing treating agent and a preparation method thereof. The underwater soil anti-scouring enhancing and self-repairing treating agent comprises a hydrogel treating agent and a polyvinyl alcohol isolating layer, wherein the outer surface of the hydrogel treating agent is coated with the polyvinyl alcohol isolating layer; the hydrogel treating agent comprises the following raw material components: polyacrylamide, sodium alginate and calcium chloride. According to the invention, interaction among polyacrylamide, sodium alginate and calcium chloride is utilized to improve the capability of the hydrogel protective layer to resist water flow scouring, and the hydrogel protective layer has a certain self-filling and repairing function on low-lying scouring pits; and meanwhile, the hydrogel is wrapped by the water-soluble polyethylene isolation layer, so that the treatment agent can automatically move towards a part which is seriously scoured locally, the targeted treatment effect is realized, the waste of the treatment agent is reduced, and the problems of inaccurate treatment position and the like caused by unreasonable selection of a treatment material throwing area are solved.

Description

Technical Field

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

[0002] The scouring phenomenon of the underwater foundation structure of hydraulic structures is one of the main engineering safety threats. The erosion and shearing effect of water flow is the power source of scouring. Water flow excavates and carries sediment from around structures such as riverbeds, embankments, offshore wind power pile foundations and bridge piers. Scouring can be mainly divided into natural scouring, general scouring and local scouring. Local scouring usually refers to the change of flow field near the structure caused by the influence of underwater structures, and the formation of scouring pits around the structure. The local scouring phenomenon is widely present in projects such as pile foundations, seawalls and submarine pipelines of offshore wind power and bridges. Pipelines laid on the seabed will cause scouring near the pipelines under the action of waves and water flow, causing local overhang of pipelines. Offshore wind power and bridge foundations will change the hydrodynamic conditions around the foundation, generate eddies around the foundation, increase the shearing effect of water flow near the foundation, and cause local scouring of sediment near the structure, which not only reduces the buried depth of the foundation structure and reduces the bearing capacity of the foundation structure, but also changes the lateral force state, which has an adverse effect on the stability of the upper structure.

[0003] According to the difference in protection principles, the local scour protection measures for underwater structures can be divided into active protection that changes the hydrodynamic conditions to reduce the shear effect of water flow and passive protection that improves the anti-scour performance of the foundation soil around the structure. The former are commonly: sandbag backfill for submarine pipeline suspension protection, retaining ring protection for pile foundations and sacrificial pile protection in front of piers. Such methods are costly and have an impact on the bearing capacity of the structure; riprap, sand blankets, concrete briquette, solidified soil treatment, etc. are common methods of passive protection. Before implementation, such methods need to prepare a large amount of treatment materials, the construction process is cumbersome and the on-site construction is difficult. The scattering area is difficult to accurately control and cannot achieve targeted protection. 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-repair treatment agent and a preparation method thereof, which can move to the local scour or severe scour area under the action of water flow for targeted adaptive treatment, and realize the active treatment of automatically reducing the parts prone to erosion and scour; and the hydrogel produced by the water absorption reaction has an adhesive adhesion and fixation effect on the suspended moving sediment in the water, and has a self-repairing effect on the part that has been scoured.

[0005] The inventive concept of the present invention is: in view of the shortcomings of existing local scour protection measures, the present invention proposes a soil anti-scour and self-repair treatment agent mainly composed of polymers. The raw material components of the treatment agent mainly include polyacrylamide, sodium alginate, calcium chloride and polyvinyl alcohol, wherein: the main function of polyacrylamide, sodium alginate and calcium chloride is to form a hydrogel protective layer on the surface of the sand bed and the scour pit. With these three substances as the main reactants, the hydrogel adhesive effect is used to enhance the anti-erosion and scour ability of the surface sand and improve the threshold conditions for the start-up of soil particles of the bed sand. Polyvinyl alcohol is mainly used as an insulating layer to control the release time to wrap the internal substances. The polyvinyl alcohol insulating layer ensures that the mixture of polyacrylamide, sodium alginate and calcium chloride can remain stable in water within a certain period of time after entering the water, and will not absorb water and react to release. At the same time, polyacrylamide, sodium alginate and calcium chloride are made into cylindrical granular particles by powder briquetting and the like, and are wrapped 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 in the scouring pit and react to release to form hydrogel. The solution-like hydrogel infiltrates into the sandy soil on the bed surface and takes root in the soil under the bed surface 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 repair 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 materials used in the early stage 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 consolidate with the surrounding soil after solidification. It remains in a hydrogel state in the water and can be bonded and fixed with the surrounding contactable soil.

[0006] In order 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, including 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; the raw material components of the hydrogel treatment agent include polyacrylamide, sodium alginate and calcium chloride.

[0007] Specifically, polyacrylamide, sodium alginate and calcium chloride are the main components of the hydrogel treatment agent, which are mainly used to generate a hydrogel protective layer on the surface of the riverbed and to adhere the sand and soil carried by the water flow, and to attach and fix it on the surface of the bed. Among them: polyacrylamide forms a hydrogel protective layer on the bed surface. Due to its smooth surface, the friction of the water flowing through its surface is weakened, and its viscous characteristics can slow down the movement of sediment particles and fix heavier sediment. The difficulty of sediment movement on the underwater bed surface will affect the development and evolution of local scour pits, and rapid scouring and silting will occur. By using the adhesive effect of polyacrylamide hydrogel, a certain thickness of sediment can be fixed on the surface of the parts prone to local scour, thereby effectively alleviating local scour, increasing the movement resistance of bed load sediment, keeping it fixed, and realizing the self-repair of local scour pits and enhancing the anti-scour ability.

[0008] Sodium alginate and calcium chloride are mainly used to enhance the strength of polyacrylamide to form hydrogel, enhance its ability to resist water flow shearing and tensile deformation, and make the hydrogel protective layer more stable. After the three solid substances of polyacrylamide, sodium alginate and calcium chloride are dissolved in water, sodium alginate first cross-links with some calcium ions to form calcium alginate gel. Calcium alginate gel has high mechanical strength, but its rheological properties are poor, and it is difficult to penetrate into the sand layer from the sand surface. In addition, because sodium alginate reacts too quickly with some calcium ions first, there is a problem of incomplete and insufficient reaction. 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 are caused to shrink, thereby reducing the viscosity of the solution, making it easier for polyacrylamide to penetrate into the sand and form 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 accurate 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 plays the role of "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 the 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 the 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 for which the treatment agent can stably exist 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-repairing 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-repairing treatment agent.

[0018] Specifically, when preparing the underwater soil anti-scour enhancement and self-repairing 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 obtain a hydrogel treatment agent. Polyvinyl alcohol and water are used to prepare a wrapping insulation layer according to a certain composition mass fraction. Since bubbles are easily generated in the polyvinyl alcohol during the temperature rise and dissolution process, a defoaming agent needs to be added to reduce the bubbles in the polyvinyl alcohol hot melt to obtain 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 immersion 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 immersion 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 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 prepared above is stable in dry conditions. In application, it only needs to be sprinkled on the treatment area. The cylindrical granular treatment agent can stably exist on the surface of the riverbed or seabed for a certain period of time, which is controlled by the thickness of polyethylene. During this stable existence period, the cylindrical treatment agent can move to the low-lying scour pit with severe scour under the action of the bottom water flow. When the release time point is reached, the reactants composed of polyacrylamide, sodium alginate and calcium chloride will react with water to produce hydrogel, realizing the enhancement of underwater soil anti-scour and 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 the hydrogel solution with strong adhesiveness and high viscosity formed by polyacrylamide after being dissolved in water. The hydrogel with strong adhesiveness is used to protect the surface of the sand bed, and the ionic interaction between polyacrylamide, sodium alginate and calcium chloride is used 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 to the suspended sediment and bed load 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 scouring 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 of time, 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 scouring will still occur at scouring locations over time. 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 scouring 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 in conjunction with the examples, so that the technical personnel of the relevant technical field can understand the present invention. It is necessary to point out here that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The non-essential improvements and adjustments made to the present invention by the skilled person in the relevant field according to the above invention content should still belong to 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 insulating layer, wherein the polyvinyl alcohol insulating layer is wrapped on the outer surface of the hydrogel treatment agent.

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

[0039] The method for preparing the underwater soil anti-scour enhancement and self-repairing 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 are stirred and mixed in a mass ratio of 1:2, isooctyl alcohol is added (the mass ratio of polyvinyl alcohol to isooctyl alcohol is 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, and then the particles soaked and coated with polyvinyl alcohol are dried in a 60° C. dry hot 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-repairing treatment agent of this embodiment, such as 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 insulating layer, wherein the polyvinyl alcohol insulating layer is wrapped on the outer surface of the hydrogel treatment agent.

[0045] The raw material components of the hydrogel treatment agent include, by weight, 60 parts of polyacrylamide, 28 parts of sodium alginate and 12 parts of calcium chloride; the particle sizes of polyacrylamide, sodium alginate and calcium chloride are all less than 0.05 mm. The thickness of the polyvinyl alcohol insulating 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 insulating layer, wherein the polyvinyl alcohol insulating layer is wrapped on the outer surface of the hydrogel treatment agent.

[0049] The raw material components of the hydrogel treatment agent include, by weight, 65 parts of polyacrylamide, 25 parts of sodium alginate and 10 parts of calcium chloride; the particle sizes of polyacrylamide, sodium alginate and calcium chloride are all less than 0.05 mm. The thickness of the polyvinyl alcohol insulating 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, only 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, so as 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 diagram 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. When applied, it can be appropriately adjusted according to the actual needs of different water flow conditions, the rate at which the agent moves and gathers underwater to low-lying and scouring areas, and the time required for the agent to move.

[0061] 2. Anti-corrosion performance

[0062] The scouring test was carried out with the Fujian sand and the hydrogel treatment agent prepared in the above Examples 1-2 and Comparative Examples 1-2 in a mass ratio of 100:1. The usage amount converted to 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 excess shear stress model was used to describe the soil erosion process using formula (1). Among them: the critical shear stress of soil and the erosion rate coefficient are characteristic parameters describing the soil erosion resistance. 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 characteristics 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 scouring pit size 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 are used, and Examples 1-3 (corresponding to Figure 4 a. Figure 4 b and Figure 4 c) The maximum scouring depth of the scouring pits is about 9 mm. The diameter of the scouring pits in Example 3 is slightly close to that in Example 2. The diameters of the scouring pits in Examples 2 and 3 are slightly larger than those in Example 1. Figure 4 d) Maximum scour pit depth 13mm, 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 is 20 mm. Compared with the blank test group without adding the treatment agent, the anti-scour ability of the Fujian sand added with the hydrogel treatment agent containing polyacrylamide is enhanced, and the degree of improvement is closely related to the mass fraction of each component of the treatment agent. When the polyacrylamide in the treatment agent is adjusted to sodium polyacrylate, the size of the scour pit formed is increased, and the anti-erosion ability of the Fujian sand is weakened.

[0069] For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, without having to go through creative labor. Therefore, simple improvements made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the protection scope 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 belong to the protection scope of the present invention.

Claims

1. An underwater soil anti-scour enhancement and self-repair treatment agent, characterized in that: The invention comprises a hydrogel treatment agent and a polyvinyl alcohol insulating layer, wherein 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.

2. The underwater soil anti-scour enhancement and self-repairing agent according to claim 1, characterized in that: 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.

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

4. The underwater soil anti-scour enhancement and self-repairing agent according to claim 1, characterized in that: The thickness of the polyvinyl alcohol insulating layer is 0.4-2 mm.

5. A method for preparing the underwater soil anti-scour enhancement and self-repairing agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: acrylamide, 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-repairing treatment agent.

6. The method for preparing the underwater soil anti-scour enhancement and self-repairing agent according to claim 5, characterized in that: The defoaming agent includes isooctyl alcohol.

7. The method for preparing the underwater soil anti-scour enhancement and self-repairing agent according to claim 5 or 6, 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.

8. The method for preparing the underwater soil anti-scour enhancement and self-repairing agent according to claim 5, characterized in that: The heating temperature is 90-95° C.; and / or the heating time is 30-50 minutes.

9. The method for preparing the underwater soil anti-scour enhancement and self-repairing agent according to claim 5, characterized in that: The drying temperature is 55-65° C.; and / or the drying time is 1-3 hours.

10. Use of the underwater soil anti-scour enhancement and self-repair treatment agent according to any one of claims 1 to 4 in local scour protection of underwater structures.

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