A sea water resistant and dispersion resistant fluidized solidified soil, a preparation method and application thereof

Abstract

This invention discloses a seawater-resistant, anti-dispersion fluidized solidified soil, comprising the following components by weight: 100 parts marine silt dry soil, 5-20 parts cement, 40-100 parts seawater, 5-10 parts fly ash, 5-10 parts slag, 5-10 parts silica fume, 0.1-3 parts sodium alginate, 0.05-0.3 parts cellulose ether, 0.1-1 parts polycarboxylate superplasticizer, and 0.3-0.9 parts composite multi-scale fibers; the composite multi-scale fibers include nanoscale fibers, microscale fibers, and macroscale fibers. In this invention, microscale fibers fill microscopic cracks, millimeter-scale fibers bridge and toughen, and macroscale fibers provide the main framework support. The combined effect of these three components significantly improves the flexural strength and bending toughness of the fluidized solidified soil, effectively inhibiting cracking caused by seawater wet-dry cycles and salt crystallization, and extending the service life of underwater protective structures.

Description

Technical Field

[0001] This invention relates to a seawater-resistant anti-dispersion fluidized solidified soil, its preparation method, and its application, belonging to the field of fluidized solidified soil. Background Technology

[0002] my country's offshore wind power, cross-sea bridges, and other marine engineering infrastructure construction have entered a period of rapid development. Projects such as pile foundation scour protection and underwater cavity filling are placing increasingly higher demands on the performance of underwater construction materials. Fluidized solidified soil, a new type of engineering material, possesses excellent fluidity and self-compacting properties and has been widely used in land-based engineering. However, how to improve the performance of traditional fluidized solidified soil in seawater environments is a pressing issue. The large amounts of dredged silt and marine soft soil waste generated in marine engineering also urgently need resource utilization. However, existing solidification technologies rely on large amounts of cement and fresh water, resulting in high environmental burdens and costs, making it difficult to achieve the goals of low-carbon and high-value applications.

[0003] Underwater anti-dispersion fluidized bed solidification technology primarily enhances the cohesiveness of the slurry by adding anti-dispersion agents. However, existing technologies are mostly designed for freshwater environments and ordinary underwater fluidized bed solidification. For marine engineering environments where seawater is used directly for mixing and must withstand high salinity and turbulent water erosion, there is currently no systematic material design solution. Existing underwater anti-dispersion materials often employ single-scale fibers or single anti-dispersion agents, failing to improve the material's overall performance, including crack resistance, toughness, and erosion resistance. While incorporating composite multi-scale fibers for stepwise anchoring can enhance the mechanical and durability properties of fluidized bed solidification, targeted formulation designs based on the synergistic effects of different fiber scales and anti-dispersion agents are lacking in seawater environments. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a fluidized solidified soil for underwater use with anti-dispersion properties, its preparation method, and its application. Combining the synergistic effects of seawater mixing, multi-scale fibers, and a two-component anti-dispersion agent, this invention has significant practical implications and broad application prospects for improving construction quality and reducing costs in underwater engineering, as well as realizing the resource utilization of waste and green and low-carbon development.

[0005] Technical Solution: This invention provides a seawater-resistant, anti-dispersion fluidized solidified soil, comprising the following components by weight: 100 parts soil (dry weight); 5-20 parts cement; 40-100 parts seawater; 5-10 parts fly ash; 5-10 parts slag; 5-10 parts silica fume; 0.1-3 parts sodium alginate; 0.05-0.3 parts cellulose ether; 0.1-1 parts polycarboxylate superplasticizer; and 0.3-0.9 parts composite multi-scale fibers (nanoscale, microscale, millimeter scale).

[0006] Preferably, the seawater-resistant anti-dispersion fluidized solidified soil comprises, by weight, the following components: 100 parts soil (dry weight); 10-20 parts cement; 40-70 parts seawater; 6-10 parts fly ash; 7-10 parts slag; 5-8 parts silica fume; 0.1-2 parts sodium alginate; 0.1-0.3 parts cellulose ether; 0.3-0.8 parts polycarboxylate superplasticizer; and 0.4-0.7 parts composite multi-scale fibers (nanoscale, microscale, millimeter scale).

[0007] More preferably, the seawater-resistant anti-dispersion fluidized solidified soil comprises, by weight, the following components: 100 parts soil (dry weight); 13-17 parts cement; 40-55 parts seawater; 6-8 parts fly ash; 8-9 parts slag; 5-6 parts silica fume; 0.3-0.8 parts sodium alginate; 0.15-0.25 parts cellulose ether; 0.4-0.6 parts polycarboxylate superplasticizer; and 0.5-0.65 parts composite multi-scale fibers (nanoscale, microscale, millimeter scale).

[0008] The seawater includes natural seawater contained in marine silt and supplemented seawater. The natural water content of the marine silt ranges from 20% to 120% depending on the sea area. When the natural seawater content is insufficient, seawater is added to adjust to the required water consumption. When the natural seawater content is too high, the marine silt is partially dehydrated to control the total water consumption.

[0009] Preferably, the cement is selected from either silicate cement or ordinary silicate cement. The core difference between silicate cement and ordinary silicate cement lies in the total content of cement clinker and gypsum: in silicate cement, this content is ≥95%, while in ordinary silicate cement, it is between 80% and 95%. Due to the higher clinker and gypsum content, silicate cement sets and hardens faster and has higher early strength. Therefore, in underwater construction where rapid hardening and early strength are required for the fluidized solidified soil, silicate cement is generally preferred. If there are no such requirements, or if cost and overall performance need to be considered, ordinary silicate cement can also be used. Overall, ordinary silicate cement has a wider range of applications.

[0010] Preferably, the strength grade of the cement is ≥32.5.

[0011] More preferably, the strength grade of the cement is ≥42.5.

[0012] Preferably, the soil has the following particle composition: sand (0.075mm~2mm) accounts for 40%~55%, silt (0.005mm~0.075mm) accounts for 25%~35%, and clay (<0.005mm) accounts for 20%~30%.

[0013] Preferably, the seawater is natural seawater, which has been physically settled and filtered to remove suspended solids, silt, algae and other impurities, so as to avoid interference with other components.

[0014] Preferably, the fly ash is conventionally used Class I fly ash, which can be purchased from the market.

[0015] Preferably, the slag is of grade S95, meaning its 28-day activity index is not less than 95%, and it can be purchased from the market.

[0016] Preferably, the silica fume is SF85 grade, meaning that the amorphous silica content is not less than 85%, and it can be purchased from the market. If there is a requirement for high strength and high performance of the fluidized solidified soil, SF90 grade should be preferred, with an amorphous silica content of not less than 90%.

[0017] Preferably, the cellulose ether and sodium alginate are used as flocculants, and their combined effect can achieve better underwater anti-dispersion and anti-erosion effects. The cellulose ether plays a role in water retention and thickening, significantly increasing the viscosity of cement-based materials and forming stable chemical bonds with cement hydration products; while sodium alginate strengthens the cohesiveness of the slurry and forms a physical gel.

[0018] More preferably, the cellulose ether is selected from at least one of hydroxypropyl methylcellulose ether and hydroxyethyl methylcellulose ether. Unless otherwise specified, hydroxypropyl methylcellulose ether is conventionally used, with an apparent viscosity between 40,000 and 65,000 mPa·s, which achieves a good balance between thickening and flowability. If the ambient temperature is high, hydroxyethyl methylcellulose ether is preferred due to its higher gel temperature and more stable performance at high temperatures.

[0019] More preferably, the sodium alginate is of industrial grade and its apparent viscosity is controlled between 200 and 400 mPa·s, so that it can reduce the impact on flowability while thickening.

[0020] Preferably, the polycarboxylate superplasticizer is a conventionally used polycarboxylate superplasticizer that can be purchased from the market.

[0021] Preferably, the composite multi-scale fibers achieve good performance by controlling their type and length within a certain range. Specifically, the preferred mass ratio of nanoscale fibers, microscale fibers, and macroscale fibers in the composite multi-scale fibers is (0.1~0.3):(0.1~0.3):(0.1~0.3). If the proportion of nanofibers is too low (<0.1), the micro-cracks will not be adequately filled, resulting in a decrease in early strength; if the proportion of macroscale fibers is too high (>0.3), the fluidity of the slurry will be significantly reduced, making construction difficult. The length ranges of each scale of fibers are as follows: nanoscale fibers are 200 nm to 500 nm in length or have a molecular weight of 12 million to 25 million; microscale fibers are 2 mm to 18 mm depending on the type; and macroscale fibers are 8 mm to 18 mm depending on the type. Exceeding these length ranges will affect the crack resistance, erosion resistance, and mechanical strength of the solidified soil. Specifically, excessively long nanofibers will weaken the nano-effect and fail to effectively fill nanoscale pores; microfibers that are too short will have insufficient bridging effect, while those that are too long will be difficult to disperse evenly; macrofibers that are too short will cause a decrease in the support of the framework, while those that are too long will be prone to entanglement and aggregation.

[0022] More preferably, the nanoscale fibers are specifically cellulose nanofibers and polyacrylamide long chains, wherein the length of the cellulose nanofibers is 200 nm to 500 nm, and the molecular weight of the polyacrylamide long chains is between 12 million and 25 million.

[0023] More preferably, the micron-scale fibers are specifically micron-sized basalt fibers, polypropylene fibers, and pulp fibers, and two or three types of fibers can be blended together without any ratio limitation. The basalt fibers have a length of 6mm to 18mm, the polypropylene fibers have a length of 9mm to 12mm, and the pulp fibers have a length of 2mm to 6mm.

[0024] More preferably, the macroscopic fibers are specifically PVA fibers and glass fibers, wherein the PVA fibers have a length of 8mm to 12mm and the glass fibers have a length of 9mm to 18mm.

[0025] The second aspect of the present invention provides a method for preparing a seawater-resistant anti-dispersion fluidized solidified soil, which is obtained by metering and stirring the components according to the weight proportions of the above-mentioned materials.

[0026] Preferably, the method for preparing the seawater-resistant anti-dispersion fluidized solidified soil includes the following steps: 1) Determine the initial moisture content of the soil, calculate the dry mass and initial moisture content of the soil, and mix the soil, cement, fly ash, slag, silica fume, sodium alginate and cellulose ether for the first time according to the weight ratio of the seawater anti-dispersion fluidized solidified soil to obtain a premixed compound. 2) Determine the remaining water amount based on the water amount in the formula and the initial moisture content of the soil. According to the weight ratio of the seawater-resistant anti-dispersion fluidized solidified soil, add the seawater and polycarboxylate superplasticizer to the premix in step 1) for a second stirring. During the second stirring, add the uniformly mixed nano, micro, and macro-scale fibers in batches and stir to obtain the final mixture, which is the required seawater-resistant anti-dispersion fluidized solidified soil material.

[0027] Preferably, in step 1), the cement, fly ash, slag, and silica fume are all in a dry state before use, and the sodium alginate and cellulose ether need to be mixed evenly with the dry powder of the cementing material in advance to avoid clumping when directly exposed to water.

[0028] Preferably, in step 1), the first stirring time is 2 to 5 minutes to ensure that the components are thoroughly and evenly mixed.

[0029] Preferably, in step 2), the seawater is natural seawater, which needs to undergo physical sedimentation and filtration before use to remove suspended solids, coarse particulate impurities, algae and other impurities, so as to avoid interference with other components.

[0030] Preferably, in step 2), the nano, micro, and macro-scale fibers are added uniformly in 2 to 4 batches during the second stirring process, and stirring is continued for more than 30 seconds after each addition to ensure that the fibers are evenly dispersed in the mixed slurry.

[0031] Preferably, in step 2), the mixing time is ≥2 min. More preferably, the mixing time is 3-5 min, until the mixture exhibits a uniform fluid state.

[0032] Preferably, in step 2), the fluidity of the solidified soil mixture is 200mm to 250mm, so that it can meet the construction requirements of pumping and self-leveling.

[0033] Preferably, in step 2), the temperature of the second stirring is 10-35°C to avoid the viscosity of sodium alginate decreasing or solidifying too quickly at high temperatures.

[0034] The present invention also provides the application of seawater-resistant anti-dispersion fluidized solidified soil in underwater engineering such as scour protection of offshore wind power pile foundations or backfilling of cross-sea bridge foundations.

[0035] This invention also provides a construction method for underwater anti-dispersion fluidized solidified soil. The prepared fluidized solidified soil mixture is transported by a pumping device and injected into the underwater construction area using a conduit method or underwater pouring method, so that the mixture self-levels and self-compacts, achieving underwater filling and protection.

[0036] Preferably, the ambient temperature during construction is 5–35°C. More preferably, the ambient temperature during construction is 10–30°C.

[0037] Preferably, the construction area is temporarily protected within 24 hours after construction to prevent direct scouring by high-speed water flow.

[0038] Preferably, after the construction is completed, the fluidized solidified soil should be naturally cured in seawater for no less than 7 days. More preferably, the curing time should be no less than 14 days.

[0039] This invention uses seawater directly as the sole mixing water, combined with local waste, and employs cement, fly ash, slag, and silica fume as composite cementitious materials. Sodium alginate and cellulose ether are incorporated as anti-dispersing agents. Physical thickening is achieved through the two-component compounding of sodium alginate and cellulose ether to achieve anti-dispersing properties. Simultaneously, composite multi-scale fibers are introduced to form a multi-level reinforcement system, enabling the fulfillment of the requirements for high flowability, self-leveling, and strong erosion resistance in underwater construction. This invention solves the problems of traditional underwater filling materials, such as reliance on freshwater mixing, poor anti-dispersing properties, and low waste resource utilization rates. The promotion and application of this invention provides a low-carbon, high-value-added green solution for erosion protection in underwater engineering, capable of disposing of large quantities of coastal dredging silt and industrial waste, demonstrating significant environmental, economic, and social benefits. Therefore, this invention effectively addresses many shortcomings of existing technologies and has high industrial application value.

[0040] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) This invention uses seawater as the only mixing water, combined with local waste such as marine silt and dredged soil, and makes full use of the activating effect of natural electrolytes in seawater on industrial waste such as slag and fly ash. It can improve the early strength and underwater anti-dispersion performance of fluidized solidified soil while saving fresh water resources, fundamentally changing the technical status quo of traditional underwater backfill materials relying on fresh water mixing and construction water supply difficulties.

[0041] (2) This invention combines sodium alginate and cellulose ether as two components to form a stable physical thickening and chemical adsorption synergistic network at the interface between the slurry and seawater, so that the material has both high flowability and self-leveling properties and strong underwater scour resistance. It can solve the problem of difficulty in balancing fluidity and anti-dispersion properties in underwater construction, and is suitable for backfilling applications in complex underwater terrains such as offshore wind power pile foundation scour pits and cross-sea bridge foundations.

[0042] (3) This invention combines micron, millimeter, and macroscopic-scale fibers to construct a multi-scale fiber reinforcement system. Micron-scale fibers fill microscopic cracks, millimeter-scale fibers act as bridges and tougheners, and macroscopic-scale fibers act as the main skeleton support. The combined effect of these three components significantly improves the flexural strength and bending toughness of the fluidized solidified soil, effectively inhibits cracking caused by seawater wet-dry cycles and salt crystallization, extends the service life of underwater protective structures, and ensures safety and durability in marine engineering.

[0043] (4) This invention uses marine silt, dredged soil and other materials as the main raw materials to dispose of industrial solid waste such as fly ash and slag, achieving a high solid waste utilization rate for underwater engineering materials. At the same time, the construction process of pipeline pumping avoids sand and gravel mining and long-distance transportation, greatly reducing carbon emissions and engineering costs, and providing a solution for low-carbon, high-value-added green new materials for my country's marine engineering.

[0044] (5) The preparation process of the present invention is simple, the setting time can be flexibly changed according to the construction conditions, and the underwater compressive strength and scour resistance meet the relevant requirements of the current engineering specifications. Attached Figure Description

[0045] Figure 1 This illustrates the performance differences between the examples and different comparative examples. Detailed Implementation

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0047] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] Unless otherwise specified, the raw materials, reagents, or processing techniques used in the following embodiments and comparative examples are all conventional commercially available products or conventional processing techniques in the art.

[0049] The raw materials used in Examples 1-3 and Comparative Examples 1-7 are as follows: 1. Soil Sample: Marine silt from a coastal engineering project was collected. Before use, only large debris was removed, with the largest particle size not exceeding 5 mm. The natural moisture content (dry basis) of the soil sample was determined to be 40%, meaning 40 parts seawater for every 100 parts dry soil. Sieve analysis revealed the following particle size distribution: sand (0.075~2 mm) 46%, silt (0.005~0.075 mm) 29%, and clay (<0.005 mm) 25%. Examples 1-3 and Comparative Examples 1-7 all used the same batch of soil samples to ensure consistent gradation.

[0050] 2. Cement: Ordinary Portland cement with a strength grade of 42.5, produced by Lanting Cement Plant of Shaoxing Zhaoshan Building Materials Co., Ltd.

[0051] 3. Seawater: Natural seawater with a salinity of 35‰.

[0052] 4. Fly ash: Class F fly ash, grade I selected, loss on ignition ≤ 5.0%, produced by Henan Wuhu Environmental Protection Technology Co., Ltd.

[0053] 5. Slag: S95 grade blast furnace slag, i.e., 28-day activity index ≥95%, produced by Shandong Kangjing New Material Technology Co., Ltd.

[0054] 6. Silica fume: SF85 grade, meaning the content of amorphous silica is not less than 85%, the particle size range is 0.1~0.3μm, and it is produced by Henan Borun Casting Materials Co., Ltd.

[0055] 7. Sodium alginate: The commonly used sodium alginate has an apparent viscosity of 200±20 mPa·s, is produced by Sinopharm Chemical Reagent Co., Ltd., and its CAS number is 9005-38-3.

[0056] 8. Cellulose ether: The commonly used hydroxypropyl methylcellulose ether has an apparent viscosity of 40,000 mPa·s and is produced by Shanghai Chenqi Chemical Technology Co., Ltd.

[0057] 9. Polycarboxylate superplasticizer: This is a high-performance polycarboxylate superplasticizer with a water reduction rate of 30% and a solid content of 25.2%. It is produced by Shanghai Chengzhi Building Materials Co., Ltd.

[0058] 10. Nanoscale fibers: Specifically, cellulose nanofibers and polyacrylamide long chains, in a weight ratio of 1:1. The cellulose nanofibers have a diameter of 4~10nm and a length of 200nm and are produced by Shanghai Maclean Biochemical Technology Co., Ltd.; the polyacrylamide long chains have a molecular weight of 20 million, CAS number 9003-05-8, and are produced by Sinopharm Chemical Reagent Co., Ltd.

[0059] 11. Micron-scale fibers: Specifically, micron-sized basalt fibers, polypropylene fibers, and pulp fibers, with a weight ratio of 1:1:2. The micron-sized basalt fibers have a diameter of 15~21μm and a length of 12mm, and are produced by Shanghai Chenqi Chemical Technology Co., Ltd.; the polypropylene fibers have a diameter of 18~48μm and a length of 9mm, and are produced by Senxiang Building Materials Store in Langli Street, Changsha County; the pulp fibers have a diameter of 20μm and a length of 2.3mm, and are produced by Linyi Senhe Biomaterials Co., Ltd.

[0060] 12. Macroscale fibers: Specifically, PVA fibers and glass fibers are mixed in a 1:1 weight ratio. The PVA fibers have a diameter of 16μm and a length of 12mm and are produced by Shanghai Kaiyuan Chemical Technology Co., Ltd.; the glass fibers have a diameter of 9~13μm and a length of 12mm and are produced by Shandong Yongxing New Materials Co., Ltd.

[0061] Example 1

[0062] A seawater-resistant, anti-dispersion fluidized solidified soil is made from the following raw materials in parts by weight: 140 parts soil sample (including 100 parts dry soil and 40 parts seawater), 15 parts cement, 10 parts added seawater, 7 parts fly ash, 8 parts slag, 6 parts silica fume, 0.8 parts sodium alginate, 0.20 parts cellulose ether, 0.50 parts polycarboxylate superplasticizer, 0.15 parts nanoscale fiber, 0.15 parts microscale fiber, and 0.2 parts macroscale fiber.

[0063] A method for preparing an underwater anti-dispersion fluidized solidified soil includes the following steps: 1) At room temperature, mix the soil sample, cement, fly ash, slag, silica fume, and sodium alginate according to the above-mentioned mass proportions, stir evenly, and obtain a premixed compound. 2) According to the weight ratio, add the supplemented seawater, polycarboxylate superplasticizer, and cellulose ether to the premix in step 1) and stir for a second time. During the stirring process, add the uniformly mixed nanoscale fibers, microscale fibers, and macroscale fibers in 3 batches. After each addition, continue stirring for more than 30 seconds to prevent fiber agglomeration and ensure that all raw materials are mixed evenly. After all the composite multi-scale fibers have been added, stir for another 2 minutes to obtain the final mixture.

[0064] A construction method for an underwater anti-dispersion fluidized solidified soil is as follows: The prepared fluidized solidified soil mixture is pumped and injected into the underwater construction area using a conduit method, allowing the mixture to self-level and self-compact, achieving underwater filling and protection. The ambient temperature during construction is around 20℃. Temporary protection is applied to the construction area for 24 hours after construction to prevent direct erosion by high-speed water flow. After completion, the fluidized solidified soil is naturally cured in seawater for 7 days.

[0065] Example 2 A seawater-resistant, anti-dispersion fluidized solidified soil is made from the following raw materials in parts by weight: 140 parts soil sample (100 parts dry soil and 40 parts seawater), 5 parts cement, 5 parts fly ash, 5 parts slag, 5 parts silica fume, 0.1 parts sodium alginate, 0.05 parts cellulose ether, 0.1 parts polycarboxylate superplasticizer, 0.1 parts nanoscale fiber, 0.1 parts microscale fiber, and 0.1 parts macroscale fiber. The preparation and construction methods are the same as in Example 1.

[0066] Example 3

[0067] A seawater-resistant, anti-dispersion fluidized solidified soil is made from the following raw materials in parts by weight: 140 parts soil sample (100 parts dry soil and 40 parts seawater), 20 parts cement, 60 parts added seawater, 10 parts fly ash, 10 parts slag, 10 parts silica fume, 3 parts sodium alginate, 0.3 parts cellulose ether, 1 part polycarboxylate superplasticizer, 0.3 parts nanoscale fiber, 0.3 parts microscale fiber, and 0.3 parts macroscale fiber. The preparation and construction methods are the same as in Example 1.

[0068] Comparative Example 1 The difference between this comparative example and Example 1 is that the amount of nanoscale fibers used is 0 parts. The remaining components, preparation methods, and application methods are the same as in Example 1.

[0069] Comparative Example 2 The difference between this comparative example and Example 1 is that the amount of micron-scale fiber used is 0 parts. The remaining components, preparation methods, and application methods are the same as in Example 1.

[0070] Comparative Example 3 The difference between this comparative example and Example 1 is that the amount of fiber used on a macroscopic scale is 0 parts. The remaining components, preparation methods, and construction methods are the same as in Example 1.

[0071] Comparative Example 4 The difference between this comparative example and Example 1 is that the seawater in step 2) is replaced with fresh water, i.e., 10 parts of fresh water are added. The remaining components, preparation methods, and construction methods are the same as in Example 1.

[0072] Comparative Example 5 The difference between this comparative example and Example 1 is that the length of the cellulose nanofibers in the nanoscale fibers is changed to 800 nm, and the molecular weight of the polyacrylamide long chain is changed to 30 million. The remaining components, preparation methods, and application methods are the same as in Example 1.

[0073] Comparative Example 6 The difference between this comparative example and Example 1 is that the length of the micron-sized basalt fibers in the micron-scale fibers is changed to 2 mm, the length of the polypropylene fibers is changed to 3 mm, and the length of the pulp fibers is changed to 1 mm. The remaining components, preparation methods, and construction methods are the same as in Example 1.

[0074] Comparative Example 7 The difference between this comparative example and Example 1 is that the length of the PVA fiber in the macroscopic fiber is changed to 20 mm, and the length of the glass fiber is changed to 25 mm. The remaining components, preparation methods, and construction methods are the same as in Example 1.

[0075] Performance Testing and Statistical Analysis All performance tests of the anti-dispersion fluidized solidified soil samples under different seawater conditions were conducted using three parallel groups of specimens, and the results are expressed as mean values. One-way ANOVA was used to compare the performance differences between Example 1 and Examples 2-3, and Comparative Examples 1-7, with Dunnett's post-hoc test used for multiple comparisons. The significance level was set at α=0.05, and p<0.05 was considered statistically significant. All statistical analyses were performed using SPSS 26.0 software.

[0076] Table 1. Comprehensive performance evaluation of fluidized solidified soil samples with different seawater dispersion resistance.

[0077] Table 1 shows that optimizing the ternary gradation of the soil to a reasonable range allows for progressively denser arrangement and filling of particles, improving the overall density and mechanical properties of the fluidized solidified soil. Using sodium alginate and cellulose ether as an anti-dispersant effectively enhances the cohesiveness and erosion resistance of the fluidized solidified soil underwater. Example 1, using a complete multi-scale fiber system mixed with seawater, achieved a 28-day compressive strength of 3.6 MPa, a 28-day flexural strength of 0.78 MPa, a mass loss rate of only 4.5%, and a turbidity ratio of 4.2%, all significantly superior to the comparative examples.

[0078] Compared to Comparative Examples 1-3 (which lacked nano, micro, or macro fibers, respectively), Example 1 showed a 44%-63% increase in 28-day compressive strength, a 50%-105% increase in flexural strength, a 57%-67% reduction in mass loss rate, and a 31%-39% reduction in turbidity ratio. This demonstrates that the three fiber scales form a hierarchical anchoring network, and none can be omitted. Compared to Comparative Examples 5-7 (where fiber sizes exceeded the preferred range, corresponding to excessively long nanofibers, excessively short microfibers, and excessively long macro fibers, respectively), Example 1 showed a 57%-100% increase in 28-day compressive strength, a 73%-105% increase in flexural strength, a 64%-70% reduction in mass loss rate, and a 42%-48% reduction in turbidity ratio. This indicates that the length of fibers at each scale must be strictly controlled within a certain range to fully realize their function. The incorporation of composite multi-scale fibers works by filling micro-scale cracks with micro-scale fibers, bridging and toughening with millimeter-scale fibers, and providing main skeletal support, forming a graded anchoring reinforcement network that significantly improves the flexural strength and bending toughness of the solidified soil. Compared to Comparative Example 4 (mixed with fresh water), Example 1 showed a 29% increase in 28-day compressive strength, a 51% decrease in turbidity ratio, and a 71% decrease in mass loss rate, further confirming that the activating effect of seawater on cementitious materials is a key aspect of this technology.

[0079] Figure 1 The figure shows the performance differences between the embodiments and different comparative examples. It can be seen intuitively that, except for the lower fluidity (which still meets the usage requirements), the mechanical properties, anti-dispersion properties, and anti-erosion properties of the embodiments are significantly better than those of the comparative examples, indicating the rationality of the formulation of the embodiments.

Claims

1. A type of seawater-resistant, anti-dispersion fluidized solidified soil, characterized in that, By weight, it comprises the following components: 100 parts of marine silt dry soil, 5-20 parts of cement, 40-100 parts of seawater, 5-10 parts of fly ash, 5-10 parts of slag, 5-10 parts of silica fume, 0.1-3 parts of sodium alginate, 0.05-0.3 parts of cellulose ether, 0.1-1 parts of polycarboxylate superplasticizer, and 0.3-0.9 parts of composite multi-scale fiber; The composite multi-scale fiber includes nanoscale fiber, microscale fiber and macroscale fiber, and the weight ratio of the nanoscale fiber, microscale fiber and macroscale fiber is (0.1~0.3):(0.1~0.3):(0.1~0.3).

2. The seawater-resistant anti-dispersion fluidized solidified soil according to claim 1, characterized in that, The cellulose ether includes at least one of hydroxypropyl methylcellulose ether or hydroxyethyl methylcellulose ether.

3. The seawater-resistant anti-dispersion fluidized solidified soil according to claim 1, characterized in that, The nanoscale fibers include cellulose nanofibers and / or polyacrylamide long chains, with a weight ratio of cellulose nanofibers and / or polyacrylamide long chains of 0~1:0~1. The length of the cellulose nanofibers is 200nm~500nm, and the molecular weight of the polyacrylamide long chains is 12 million~25 million.

4. The seawater-resistant anti-dispersion fluidized solidified soil according to claim 1, characterized in that, The micron-scale fibers include one or more of micron-sized basalt fibers, polypropylene fibers, or pulp fibers; the length of the micron-sized basalt fibers is 6mm to 18mm, the length of the polypropylene fibers is 9mm to 12mm, and the length of the pulp fibers is 2mm to 6mm.

5. The seawater-resistant anti-dispersion fluidized solidified soil according to claim 1, characterized in that, The macroscopic fibers include PVA fibers and / or glass fibers, with a weight ratio of 0~1:0~1 for PVA fibers and glass fibers; the length of the PVA fibers is 8mm~12mm, and the length of the glass fibers is 9mm~18mm.

6. The seawater-resistant anti-dispersion fluidized solidified soil according to claim 1, characterized in that, By weight, it comprises the following components: 100 parts of marine silt dry soil, 10-20 parts of cement, 30-70 parts of seawater, 6-10 parts of fly ash, 7-10 parts of slag, 5-8 parts of silica fume, 0.1-2 parts of sodium alginate, 0.1-0.3 parts of cellulose ether, 0.3-0.8 parts of polycarboxylate superplasticizer, and 0.4-0.7 parts of composite multi-scale fiber; The composite multi-scale fiber includes nanoscale fiber, microscale fiber and macroscale fiber, and the weight ratio of the nanoscale fiber, microscale fiber and macroscale fiber is (0.1~0.2):(0.1~0.2):(0.2~0.3).

7. The seawater-resistant anti-dispersion fluidized solidified soil according to claim 1, characterized in that, By weight, it comprises the following components: 100 parts of marine silt dry soil, 13-17 parts of cement, 40-55 parts of seawater, 6-8 parts of fly ash, 8-9 parts of slag, 5-6 parts of silica fume, 0.3-0.8 parts of sodium alginate, 0.15-0.25 parts of cellulose ether, 0.4-0.6 parts of polycarboxylate superplasticizer, and 0.5-0.65 parts of composite multi-scale fiber; The composite multi-scale fiber includes nanoscale fiber, microscale fiber and macroscale fiber, and the weight ratio of the nanoscale fiber, microscale fiber and macroscale fiber is (0.1~0.15):(0.15~0.2):(0.25~0.3).

8. A method for preparing the seawater-resistant, anti-dispersion fluidized solidified soil according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Mix marine silt, cement, fly ash, slag, silica fume and sodium alginate according to the weight ratio, stir and obtain a premixed compound; (2) Add seawater and polycarboxylate superplasticizer to the premix in step (1) according to the weight ratio and stir for the second time. During the stirring process, add the uniformly mixed composite multi-scale fibers in batches. Stir after each batch of the mixture is added. After all the composite multi-scale fibers are added, stir again to obtain the final mixture.

9. The application of the seawater-resistant anti-dispersion fluidized solidified soil according to any one of claims 1 to 7 in underwater engineering.

10. The application according to claim 9, characterized in that, The underwater engineering projects include scour protection for offshore wind turbine pile foundations or backfilling for cross-sea bridge foundations.

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