Vertical barrier material based on marine facies sludge and preparation method of vertical barrier material

Abstract

The invention belongs to the technical field of geotechnical engineering materials and environmental engineering, and discloses a vertical barrier material based on marine silt and a preparation method thereof. The vertical barrier material comprises in-situ marine facies sludge, xanthan gum, sodium alginate and polylactic acid. The construction of a xanthan gum-sodium alginate-polylactic acid ternary compound system utilizes the electrostatic interaction between biopolymers and the skeleton hydrophobic effect of polylactic acid to generate a synergistic enhancement effect, thereby further enhancing the compactness and permeation resistance of the material. A biopolymer aqueous solution is prepared by a wet method and is mixed and stirred with sludge to form homogeneous solidified soil. The material disclosed by the invention has the characteristics of being green, low-carbon, environment-friendly, biodegradable and the like, conforms to the strategic target of double carbon, and is simple in preparation process, low in cost and high in operability. And through resource utilization of the marine mud flat sludge, the engineering cost is effectively reduced, the environmental pollution is reduced, and an innovative technical support path is provided for pollution control and sustainable development of coastal areas.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering materials and environmental engineering technology, specifically a vertical barrier material based on marine silt and its preparation method. Background Technology

[0002] With the continuous advancement of the "dual-carbon" strategy and the construction of ecological civilization, and driven by the concepts of ecological environment governance and resource recycling, the development of new vertical barrier materials that combine low carbon emission characteristics with environmentally friendly performance has become a key technological path for achieving pollution control and sustainable development. Currently, my country primarily uses cement-based, cement-bentonite-based, and soil-cement-bentonite-based vertical barrier materials. However, the extensive use of cement-based materials not only leads to high carbon emissions, but the alkaline hydroxide ions released during hydration react with calcium ions in water to form calcium hydroxide, resulting in water calcification. Furthermore, the low specific heat capacity of cement materials enhances surface heat radiation during the curing process, exacerbating the urban heat island effect and increasing the frequency of local extreme weather events. While bentonite-based materials can improve impermeability through water absorption and expansion, their impermeability deteriorates significantly under long-term wet-dry cycles or in high-salt environments. Meanwhile, high-quality sodium-based bentonite resources are scarce and modification costs are high. Marine tidal flat silt, widely distributed along my country's coast, represents a potential resource, and its efficient utilization has become a crucial issue for pollution control and sustainable land resource development in coastal areas. How to achieve resource utilization of marine tidal flat silt through technological innovation and develop novel vertical barrier materials that combine environmental friendliness and engineering performance is a key research direction.

[0003] Patent CN120664819A discloses a biochar-zero-valent iron reinforced bentonite-based vertical barrier material for complex-contaminated groundwater, its preparation method, and its application. The material is prepared by mixing micron-sized zero-valent iron, sodium alginate, biochar, and sodium-modified calcium-based bentonite. This method utilizes the adhesive and gelling properties of biopolymers to bind soil particles, reducing soil permeability and forming improved soil. However, the lack of hydrophobic polyester materials as a reinforcing skeleton results in insufficient stability of the material under long-term aquatic conditions, leaving room for improvement in its mechanical and impermeability properties. This technology has several drawbacks and cannot be widely used.

[0004] In summary, while biopolymer-based modified soils do have applications in geotechnical engineering materials and environmental engineering technologies, they still suffer from problems such as insufficient stability, poor mechanical properties, and poor impermeability. Therefore, it is of great significance to develop an innovative vertical barrier material that is green, low-carbon, non-toxic, biodegradable, has a low permeability coefficient, strong compressive and crack resistance, and long-term stability and durability. Summary of the Invention

[0005] The purpose of this invention is to provide a vertical barrier material based on marine silt. This vertical barrier material is made by solidifying marine silt using a compound of the biopolymer xanthan gum, sodium alginate, and polylactic acid (PLA). The anionic groups of xanthan gum and the cationic groups of sodium alginate form a cross-linked network through electrostatic attraction, enhancing intermolecular forces. PLA provides hydrophobic segments and skeletal support in the composite system, improving not only the density of the composite structure but also enhancing the material's compressive and crack resistance. Furthermore, xanthan gum, sodium alginate, and clay particle surfaces form a three-dimensional network structure through hydrogen bonding, reducing the permeability coefficient of the vertical barrier material and improving its seepage prevention performance. This forms a "xanthan gum-sodium alginate-PLA compound system" that can replace traditional cement-based materials, reducing carbon emissions by 90%–95% while simultaneously achieving the resource utilization of silt.

[0006] The objective of this invention is achieved through the following solution: A vertical barrier material based on marine silt, the vertical barrier material comprising the following components by mass fraction: 99.0-99.8% in-situ marine silt, 0.1-0.5% xanthan gum, 0.1-0.5% sodium alginate, and 0-0.17% polylactic acid.

[0007] Preferably, the vertical barrier material comprises the following components by mass fraction: marine silt 99.2-99.5%, xanthan gum 0.2-0.3%, sodium alginate 0.2-0.3%, and polylactic acid 0.10-0.15%.

[0008] In-situ marine silt provides a large amount of aluminosilicate clay particles with a large specific surface area and abundant surface hydroxyl groups. Xanthan gum long-chain molecules can quickly combine with water, increasing the viscosity of the silt and effectively encapsulating and stabilizing silt particles to prevent sedimentation and segregation. The anionic carboxyl groups on the side chains can attract positively charged groups, and the hydroxyl groups on the molecular chains can form a hydrogen bond network with the hydroxyl or amino groups of sodium alginate, the hydroxyl groups on the surface of silt clay particles, and water molecules, constructing a three-dimensional network structure. The G blocks of sodium alginate can coordinate with cations in the silt to form ionic cross-linking points, improving gel strength and rigidity, and can generate molecular chain entanglement with xanthan gum to improve thickening ability. The hydrophobic segments of polylactic acid are interspersed in the hydrophilic polysaccharide-silt network, hindering the migration path of water molecules and reducing the permeability coefficient. Polylactic acid has high rigidity and can support the composite material, improving the overall compressive strength and load-bearing capacity.

[0009] Preferably, the in-situ marine silt has a natural water content of 50-55%, a liquid limit of 41.5-42.9, a plastic limit of 22.7-24.1, a plasticity index of 18.0-19.3, and an organic matter content of 1.25-1.40%.

[0010] Xanthan gum and sodium alginate are water-soluble polymers with high natural water content, providing a solvent environment that ensures ion migration. At the same time, the biopolymer chains form a three-dimensional cross-linked gel network with water molecules, achieving low permeability. A high plasticity index indicates that the sludge contains clay minerals with a large specific surface area and high surface energy. The surface of clay particles is rich in silanol and aluminol groups. The hydroxyl and carboxyl groups on the molecular chains of xanthan gum and sodium alginate can form hydrogen bonds and coordination bonds. The higher plasticity index results in finer particles that can effectively fill pores and improve the seepage prevention performance of the barrier material.

[0011] Preferably, the mass ratio of xanthan gum to sodium alginate is 1:1.

[0012] Sodium alginate provides rigid ionic crosslinking points, achieving an optimal 1:1 distribution in the flexible network formed with xanthan gum. Too few rigid points result in a soft crosslinked network with insufficient strength, while too many rigid points make the crosslinked network too brittle and prone to cracking. A 1:1 ratio can simultaneously achieve a balance between strength and toughness.

[0013] Preferably, the xanthan gum is food grade, with a purity of ≥80%, an apparent viscosity of 1400 mPa·s, and a density of 1.54 g / cm³. 3 Sodium alginate is industrial grade, with a purity ≥80%, an apparent viscosity of 900 mPa·s, and a density of 1.35 g / cm³. 3 Polylactic acid (PLA) is industrial grade, with a purity ≥95%, a melting point of 150~160℃, and a density of 1.25 g / cm³. 3 .

[0014] Preferably, the ratio of the sum of the moisture content of the in-situ sludge and the moisture content of the biopolymer in the vertical barrier material to the sum of the dry weight of the sludge and the dry weight of the biopolymer powder is 0.5.

[0015] The natural water content of silt is 50-55%. A water-to-solid ratio of 0.5 maximizes the effective solid content, results in greater theoretical strength, lower permeability, and optimal product volume stability.

[0016] This invention discloses a method for preparing a vertical barrier material based on marine silt, comprising the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, weigh out deionized water, and slowly add it to the powder that is mixed evenly in S1 while stirring. Increase the speed and continue stirring until a homogeneous and transparent composite gel is formed. Stop stirring and let it stand to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed and let stand for 30 seconds, use a scraper to clean the inner wall of the mixing pot and the material adhering to the blades, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a uniform speed and stirred at high speed until it is evenly mixed to obtain a vertical barrier material based on marine silt.

[0017] Preferably, the specific steps in step S2 are as follows: Prepare a biopolymer-polylactic acid aqueous solution using a wet process. Weigh deionized water at a mass ratio of 1:50. First, pour the deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) into a 500 mL glass beaker and fix it in a 25℃ constant-temperature magnetic stirrer. Start the stirrer, setting the initial speed to 300 rpm. While stirring, slowly add the uniformly mixed powder from S1 to avoid clumping. After all the powder has been added, gradually increase the speed to 600 rpm and continue stirring for 30 min until a homogeneous, transparent composite gel is formed. After stopping stirring, let it stand for 20 min to eliminate air bubbles.

[0018] The wet method for preparing the biopolymer-polylactic acid aqueous solution eliminates the premature cross-linking effect of foreign ions on sodium alginate, ensuring that sodium alginate only undergoes hydration and chain extension, forming a homogeneous solution with good fluidity; low-speed stirring ensures that the powder is fully wetted, and high-speed stirring after increasing the speed can completely break down the long polymer chains, allowing its structure to fully extend.

[0019] Preferably, the specific stirring conditions in step S3 are: stirring at a low speed of 200 rpm for 5 minutes.

[0020] Low-speed stirring can break down the original flocculation structure to form a uniform suspension, fully releasing the cations inside the flocs; scraper cleaning and backfilling can reduce material loss and improve mixing efficiency.

[0021] Preferably, the specific stirring conditions in step S4 are: high-speed stirring at 400 rpm for 10 minutes.

[0022] High-speed stirring can effectively break up the viscous composite gel of S2 and the blocky flocs formed by the sludge slurry of S3, increasing the contact area between the gel and the sludge and improving the reaction efficiency.

[0023] The beneficial effects of this invention are as follows: (1) Both xanthan gum and sodium alginate are biopolymers, which have the characteristics of being green, low-carbon, non-toxic and biodegradable, and show good ecological compatibility. (2) Xanthan gum is an anionic polymer with a negative charge on its molecular chain. Sodium alginate is a cationic polymer with a positive charge on its molecular chain. When the two are mixed in solution, electrostatic interaction occurs, which can significantly enhance the intermolecular binding force and form a more stable three-dimensional network structure; (3) Hydrophilic groups on the molecular chains of xanthan gum and sodium alginate form hydrogen bonds with the surface of clay particles, further enhancing the density of the network. This mechanism of synergistic effect of crosslinking and hydrogen bonding can effectively fill the pores in marine silt, hinder the seepage path of water molecules, and thus significantly reduce the permeability coefficient of vertical barrier materials; (4) As a backbone component in the composite system, polylactic acid can improve the material’s impermeability through its hydrophobic segments, while also enhancing the composite system’s compressive strength and crack resistance. In addition, the slow-release degradation characteristics of polylactic acid help improve the material’s long-term stability and durability in complex coastal environments. Detailed Implementation

[0024] Example 1: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 0.8g of xanthan gum, 0.8g of sodium alginate, and 0g of polylactic acid.

[0025] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0026] Example 2: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 1.6g of xanthan gum, 1.6g of sodium alginate, and 0g of polylactic acid.

[0027] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0028] Example 3: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 2.4g of xanthan gum, 2.4g of sodium alginate, and 0g of polylactic acid.

[0029] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0030] Example 4: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 3.2g of xanthan gum, 3.2g of sodium alginate, and 0g of polylactic acid.

[0031] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0032] Example 5: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 4.0g of xanthan gum, 4.0g of sodium alginate, and 0g of polylactic acid.

[0033] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0034] Example 6: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 2.2g of xanthan gum, 2.2g of sodium alginate, and 0.5g of polylactic acid.

[0035] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0036] Example 7: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 1.95g of xanthan gum, 1.95g of sodium alginate, and 1.0g of polylactic acid.

[0037] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0038] Example 8: This embodiment provides a vertical barrier material based on marine silt, specifically comprising the following components by mass: 800g of in-situ marine silt, 1.7g of xanthan gum, 1.7g of sodium alginate, and 1.5g of polylactic acid.

[0039] This embodiment also provides a vertical barrier material based on marine silt, specifically including the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the preset mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the solid color is uniform. S2, a wet process was used to prepare an aqueous solution of the biopolymer-polylactic acid. Deionized water was weighed at a mass ratio of 1:50. The deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) was first poured into a 500 mL glass beaker and fixed in a 25℃ constant temperature magnetic stirrer. The stirrer was started, and the initial speed was set to 300 rpm. While stirring, the powder mixed evenly in S1 was slowly added to avoid clumping. After all the powder was added, the speed was gradually increased to 600 rpm, and stirring was continued for 30 min until a homogeneous transparent composite gel was formed. After stopping stirring, it was allowed to stand for 20 min to eliminate air bubbles. S3, add in-situ sludge to the mud mixing pot, stir at low speed of 200 rpm for 5 min, let stand for 30 s, clean the inner wall of the mixing pot and the material adhering to the blades with a scraper, and backfill to the center of the mixing pot. S4. The homogeneous transparent composite gel pre-prepared in S2 is injected into the mixing pot at a constant speed and stirred at 400 rpm for 10 minutes. After uniform mixing, a vertical barrier material based on marine silt is obtained.

[0040] Experimental Example 1: This experimental example is the permeability coefficient test of the vertical barrier material based on marine silt prepared in Examples 1-8. The results are shown in Table 2 below.

[0041] Sufficient vertical barrier material slurry was prepared for Examples 1-8, with pure in-situ marine silt as the control group. The inner wall of the weighing ring (m1) was weighed, fresh slurry was added, and the total weight (m2) was recorded. The slurry was then wrapped and cured to ensure complete polymer crosslinking. The slurry was submerged in deionized water in a saturator. The saturator was then evacuated under low vacuum, and deionized water was slowly injected to submerge the sample. The vacuum was maintained for 6 hours, and the sample was allowed to stand at normal pressure for 24 hours. After drying, the sample was weighed (m3), and the saturation was calculated to be ≥95%. The saturated sample was pushed into a permeation container, the system was sealed, and deionized water was injected from the bottom inlet. The test was conducted. The time t required for the water head to decrease from h1 to h2 was recorded. Three different water head intervals were selected for measurement three times. The steps were repeated to obtain three sets of data. The permeability coefficient was calculated, and the average value was taken.

[0042] The basic physical properties of the in-situ marine silt are shown in Table 1 below.

[0043] Table 1. Basic physical properties of silt Table 2. Permeability Coefficient Test Results The control group (pure in-situ marine silt) had a permeability coefficient of 2.1×10-9m / s: the silt was formed by the van der Waals forces between clay particles and other weak forces to form a flocculated structure. There were interconnected seepage channels, water could migrate freely, and there was a lack of hydrophobic barriers, resulting in poor seepage prevention performance.

[0044] Example 1 (800g in-situ marine silt, 0.8g xanthan gum, 0.8g sodium alginate, 0g polylactic acid): Permeability coefficient 5.6×10⁻⁶ -10 m / s: The total amount of biopolymers is low. Xanthan gum and sodium alginate form a sparse biopolymer cross-linking network, which cannot penetrate the whole and cannot effectively wrap and bridge most of the silt particles, resulting in seepage channels.

[0045] Example 2 (800g in-situ marine silt, 1.6g xanthan gum, 1.6g sodium alginate, 0g polylactic acid): Permeability coefficient 8.9×10⁻⁶ -10 m / s: The polymer network cannot be densely connected, resulting in particle agglomeration. The polymer encapsulates the sludge particles, forming agglomerates. More unobstructed seepage channels are left between the agglomerates, and the porosity increases.

[0046] Example 3 (800g in-situ marine silt, 2.45g xanthan gum, 2.45g sodium alginate, 0g polylactic acid): Permeability coefficient 3.5×10⁻⁶ -11m / s: The biopolymer network can encapsulate sludge particles through hydrogen bonding and ionic cross-linking, forming a continuous and dense three-dimensional network. The flexible long chains of xanthan gum and the rigid ionic cross-linking points provided by sodium alginate can cross-link to form a cross-linked network with sufficient strength and density, which can fill most of the tiny gaps and reduce the permeability coefficient.

[0047] Example 4 (800g in-situ marine silt, 3.2g xanthan gum, 3.2g sodium alginate, 0g polylactic acid): Permeability coefficient 5.4×10⁻⁶ -11 m / s and the permeability coefficient of Example 5 (800g in-situ marine silt, 4.0g xanthan gum, 4.0g sodium alginate, 0g polylactic acid) was 7.6×10. -11 m / s: Excessive biopolymers generate strong electrostatic attraction or intermolecular interactions such as hydrogen bonding, leading to excessive aggregation of the polymer itself, disrupting the uniformity of the cross-linked network, resulting in excessive cross-linking and phase separation, concentration of shrinkage stress, and easy generation of cracks and larger pores.

[0048] Example 6 (800g in-situ marine silt, 2.2g xanthan gum, 2.2g sodium alginate, 0.5g polylactic acid): Permeability coefficient 2.9×10⁻⁶ -11 m / s: A small number of polylactic acid particles can act as hydrophobic reinforcement points, dispersed in the already formed polymer cross-linked network. The strong hydrophobicity of polylactic acid particles can physically cut off the water film channels of the cross-linked gel network and prevent water molecules from penetrating. As rigid particles, polylactic acid particles can bridge the cracks in the cross-linked network, fill the pores, and improve the stability of the material.

[0049] Example 7 (800g in-situ marine silt, 1.95g xanthan gum, 1.95g sodium alginate, 1.0g polylactic acid): Permeability coefficient 2.6×10⁻⁶ -11 m / s: Polylactic acid, xanthan gum, and sodium alginate work synergistically to reduce permeability, form a continuous hydrophobic barrier pathway, and avoid self-aggregation that could disrupt the continuity of the organic network.

[0050] Example 8 (800g in-situ marine silt, 1.7g xanthan gum, 1.7g sodium alginate, 1.5g polylactic acid) Permeability coefficient 3.0×10 -11 m / s: The high polylactic acid content enhances the hydrophobic tendency, leading to the aggregation of polylactic acid particles. This results in the formation of interfacial channels that disrupt the continuous gel phase surface, thus reducing performance.

[0051] Permeability coefficient is a key indicator for evaluating the impermeability of materials. With increasing biopolymer content, the permeability coefficient initially decreases and then slightly increases. The permeability coefficient of the control group (pure in-situ marine silt) is 2.1 × 10⁻⁶. -9m / s. In the examples where only xanthan gum and sodium alginate were added, the permeability coefficient gradually decreased as the dosage of each xanthan gum and sodium alginate increased from 0.8 g to 2.4 g (Examples 1 to 3). The lowest permeability coefficient was observed in Example 3 (800 g of in-situ marine silt, 2.4 g of xanthan gum, 2.4 g of sodium alginate, and 0 g of polylactic acid), at 3.5 × 10⁻⁶ m / s. -11 The permeability coefficient was approximately two orders of magnitude lower than the control group. However, when the dosages of xanthan gum and sodium alginate were further increased to 3.2 g and 4.0 g respectively (Examples 4 and 5), the permeability coefficient rebounded, reaching 5.4 × 10⁻⁶ m / s. -11 m / s and 7.6×10 -11 m / s.

[0052] With a fixed total biopolymer content of 4.9 g (accounting for 0.6% of the total material mass fraction), polylactic acid was further added (Examples 6 to 8), resulting in a further decrease and stabilization of the permeability coefficient, which was 2.9 × 10⁻⁶. -11 m / s, 2.6×10 -11 m / s and 3.0×10 -11 m / s, among which Example 7 (adding 1.0g, mass fraction of 0.12% polylactic acid) showed the best permeability barrier performance. The main reasons are: (1) At low dosage, the synergistic effect of xanthan gum and sodium alginate forms a stable three-dimensional network structure through electrostatic interaction, and polylactic acid further provides hydrophobic segments and skeleton support, effectively filling the pores in the sludge and hindering the seepage path of water molecules, thereby significantly reducing the permeability coefficient; (2) When the biopolymer dosage exceeds 0.6% (fixed total biopolymer amount is 4.9g), the electrostatic interaction of xanthan gum and sodium alginate may lead to excessive cross-linking or local aggregation, forming an uneven network structure, while polylactic acid may produce local microphase separation in this process, reducing the density of the system, thereby causing the permeability coefficient to rise slightly. In summary, the optimal performance was achieved using 800g of in-situ marine silt, 1.95g of xanthan gum, 1.95g of sodium alginate, and 1.0g of polylactic acid in Example 7, i.e., a mass fraction of 99.4% in-situ marine silt, 0.24% xanthan gum, 0.24% sodium alginate, and 0.12% polylactic acid.

Claims

1. A vertical barrier material based on marine silt, characterized in that, The vertical barrier material comprises the following components by mass fraction: 99.0-99.8% in-situ marine silt, 0.1-0.5% xanthan gum, 0.1-0.5% sodium alginate, and 0-0.17% polylactic acid.

2. The vertical barrier material based on marine silt according to claim 1, characterized in that, The vertical barrier material comprises the following components by mass fraction: 99.2-99.5% in-situ marine silt, 0.2-0.3% xanthan gum, 0.2-0.3% sodium alginate, and 0.10-0.15% polylactic acid.

3. The vertical barrier material based on marine silt according to claim 1 or 2, characterized in that, The in-situ marine silt has a natural water content of 50-55%, a liquid limit of 41.5-42.9, a plastic limit of 22.7-24.1, a plasticity index of 18.0-19.3, and an organic matter content of 1.25-1.40%.

4. The vertical barrier material based on marine silt according to claim 1 or 2, characterized in that, The mass ratio of xanthan gum to sodium alginate is 1:

1.

5. The vertical barrier material based on marine silt according to claim 1 or 2, characterized in that, The xanthan gum is food grade, with a purity of ≥80%, an apparent viscosity of 1400 mPa·s, and a density of 1.54 g / cm³. 3 Sodium alginate is industrial grade, with a purity ≥80%, an apparent viscosity of 900 mPa·s, and a density of 1.35 g / cm³. 3 Polylactic acid (PLA) is industrial grade, with a purity ≥95%, a melting point of 150~160℃, and a density of 1.25 g / cm³. 3 .

6. The vertical barrier material based on marine silt according to claim 1 or 2, characterized in that, The ratio of the sum of the moisture content of the in-situ sludge and the moisture content of the biopolymer in the vertical barrier material to the sum of the dry weight of the sludge and the dry weight of the biopolymer powder is 0.

5.

7. A method for preparing a vertical barrier material based on marine silt as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Weigh out in-situ marine silt, xanthan gum, sodium alginate and polylactic acid powder according to the mass ratio. Mix xanthan gum and sodium alginate powder thoroughly first, and then mix with polylactic acid until the color is uniform. S2, take deionized water and stir it into the powder mixture in S1, increase the stirring speed to form a homogeneous transparent gel, stop stirring and let it stand to defoam; S3, add in-situ sludge to the mud mixing pot, stir at low speed and let stand for 30 seconds, use a scraper to clean the inner wall of the mixing pot and the material adhering to the blades, and backfill to the center of the mixing pot. S4. The homogeneous transparent gel pre-prepared in S2 is injected into the mixing pot at a uniform speed and stirred at high speed until homogeneous to obtain a vertical barrier material based on marine silt.

8. The method for preparing vertical barrier material based on marine silt according to claim 7, characterized in that, The specific steps in step S2 are as follows: Prepare a biopolymer-polylactic acid aqueous solution using a wet method. Weigh deionized water at a mass ratio of 1:

50. First, pour the deionized water (pH=6.9, conductivity 1 µS / cm, temperature 25±2℃) into a 500 mL glass beaker and fix it in a 25℃ constant temperature magnetic stirrer. Start the stirrer and set the initial speed to 300 rpm. While stirring, slowly add the powder that was mixed evenly in S1 to avoid clumping. After all the powder has been added, gradually increase the speed to 600 rpm and continue stirring for 30 min until a homogeneous transparent composite gel is formed. After stopping stirring, let it stand for 20 min to eliminate air bubbles.

9. The method for preparing vertical barrier material based on marine silt according to claim 7, characterized in that, The specific stirring conditions in step S3 are: stirring at a low speed of 200 rpm for 5 minutes.

10. The method for preparing a vertical barrier material based on marine silt according to claim 7, characterized in that, The specific stirring conditions in step S3 are: high-speed stirring at 400 rpm for 10 minutes.

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