Crystal removal agent for long-term maintenance of crystallization disease of tunnel drainage system, and preparation method and application thereof

Abstract

The application discloses a kind of for tunnel drainage system crystallization disease long-acting maintenance de-crystal and its preparation method and application, belong to tunnel maintenance technical field.The de-crystal includes de-crystal function component (gluconic acid, levulinic acid and polyaspartic acid), degradable slow-release matrix component (PCL, PBAT and modified starch) and external admixture component (including PEG-600 and Span-80).When preparing, first mix acid aqueous solution and starch into slurry, then slowly drop into 95~105 DEG C PCL, PBAT, PEG-600 and Span-80 melt, after stirring evaporation, cooling solidification is obtained.The application constructs hydrophobic degradable slow-release matrix using PCL and PBAT, PEG-600 reduces PBAT melting temperature to guarantee aqueous phase safe processing, and Span-80 realizes uniform wrapping of active ingredient.Product is layer by layer eroded in tunnel water flow, slow-release period is more than 6 months, with de-crystal, scale inhibition, low corrosion and full biodegradation characteristics, can be used to remove and prevent calcium carbonate crystallization in tunnel drainage system, inspection well or sand trap.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering operation and maintenance and drainage system disease prevention and control technology, specifically involving a crystal removal block for long-term maintenance of crystallization disease in tunnel drainage systems, its preparation method and application. Background Technology

[0002] Crystallization blockage in tunnel drainage systems is a common problem affecting the long-term operational safety and structural durability of tunnels. During tunnel operation, groundwater seeps into the surrounding rock and shotcrete layers, dissolving large amounts of calcium and hydroxide ions to form a highly calcium- and alkaline seepage fluid. This seepage fluid enters the drainage pipes and reacts with carbon dioxide in the air, undergoing a carbonation reaction to form calcium carbonate precipitate. Under alternating wet and dry conditions and pressure fluctuations, this precipitate gradually hardens and eventually blocks the pipes. Once crystallization blockage occurs in the drainage system, it leads to increased water pressure behind the lining, causing serious problems such as lining cracking, water leakage, and even structural instability. This poses a significant threat to tunnel operational safety and also substantially increases maintenance costs.

[0003] The prevention and control technologies for crystallization defects in tunnel drainage systems are mainly divided into three categories: mechanical methods, physical removal methods, and chemical cleaning methods. Mechanical methods primarily use high-pressure equipment to generate a powerful water jet, physically scouring or pulverizing the blockages on the pipe walls. Simultaneously, a stirring force suspends and disperses the washed-off scale out of the pipe. While this method can remove existing crystals in a short period, the drainage pipes are usually buried inside the lining, with narrow and winding diameters. High-pressure water jets can easily damage the inner lining, and it is difficult to completely remove stubborn scale, resulting in limited cleaning effectiveness, frequent operation, and high maintenance costs. Physical removal methods mainly refer to the application of electrical, magnetic, and acoustic technologies and corresponding equipment in the drainage pipes to achieve physical anti-scaling, corrosion inhibition, and removal of crystallized blockages. However, physical removal methods cannot change the chemical properties of the water, and crystals will regenerate in a short period. Repeated investment of equipment and manpower is required, and the equipment installation and maintenance are complex, significantly limiting its practical application. Chemical cleaning methods typically involve injecting acidic solutions for dissolution. While this method is effective at dissolving existing calcium carbonate crystals, it presents several drawbacks: Firstly, strong acidic solutions pose varying degrees of corrosion risk to concrete linings and PVC or HDPE drainage pipes. Long-term use may induce pipe rupture or lining deterioration, severely impacting tunnel structural safety. Secondly, traditional chemical cleaning agents are often used only for single injections, resulting in excessively rapid release of active ingredients, uncontrollable reaction processes, and short effective durations, making long-term prevention and control impossible.

[0004] In recent years, researchers have attempted to develop slow-release scale inhibitors or de-crystallizers. Chinese patent application CN114890557B discloses a slow-release solid scale inhibitor using silica aerogel as a carrier. This slow release is achieved through the physical adsorption of the porous carrier. However, the carrier is an inorganic, non-degradable material, and its long-term residue in the drainage system may cause secondary pollution. Furthermore, this product's primary function is scale inhibition, with limited ability to dissolve existing crystals. Chinese patent application CN118772966A discloses a multi-layered, concentrated solid de-crystallizer that releases acid in stages through layer-by-layer peeling. However, its preparation process is complex, and the active ingredient remains in solid acid powder form. During release, the local acid concentration may be too high, posing a risk of corrosion to pipelines. Chinese patent CN118792119A discloses an environmentally friendly liquid de-crystallizer that improves de-crystallization efficiency by synthesizing long-chain compounds with multiple hydroxyl and carboxyl groups. However, it is in liquid form, lacks a slow-release carrier, and is difficult to maintain an effective concentration in dynamically flowing water for extended periods.

[0005] In summary, current technologies lack a solid de-crystallizing product that can adapt to dynamic flowing water environments, possess slow-release capabilities, and be placed in drainage systems for extended periods to continuously soften, disperse, and inhibit crystallization. Therefore, developing a long-lasting, low-corrosion, and fully biodegradable de-crystallizing block is of great significance for achieving preventative maintenance and long-term upkeep of tunnel drainage systems. Summary of the Invention

[0006] To address the current technical limitations of existing de-crystallization products for tunnel drainage systems, which struggle to simultaneously achieve long-lasting slow release, low corrosivity, and full biodegradability, this invention aims to provide a de-crystallization block for long-term maintenance of crystallization damage in tunnel drainage systems, along with its preparation method and application. Through the synergistic effect of de-crystallization functional components, biodegradable slow-release matrix components, and admixture components, the technical problem of existing de-crystallization products for tunnel drainage systems failing to simultaneously achieve long-lasting slow release, low corrosivity, and full biodegradability is solved.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems, comprising the following components by mass percentage: The de-crystallization functional component comprises 55% to 65%, and the de-crystallization functional component includes gluconic acid, levulinic acid, and polyaspartic acid; The sustained-release matrix component comprises 25% to 35%, and the sustained-release matrix component includes polycaprolactone, polybutylene adipate / terephthalate and modified starch; The external admixture component is 7% to 12%, and the external admixture component includes polyethylene glycol 600 and Span-80; In this mixture, gluconic acid, acetylpropionic acid, and polyaspartic acid are all added in the form of a 60% aqueous solution.

[0008] The gluconic acid comprises 25%–35% of the dry weight, the levulinic acid comprises 15%–25% of the dry weight, and the polyaspartic acid comprises 5%–15% of the dry weight. Gluconic acid, as the primary acid, provides a mild and persistent acidic environment; levulinic acid assists in the penetration and dissolution of dense crystals; and polyaspartic acid, as a green scale inhibitor, plays a role in lattice distortion and dispersion. Within this ratio range, the three components achieve optimal synergistic effects, ensuring efficient dissolution of calcium carbonate crystals while avoiding the risk of pipeline corrosion from excessively high local acid concentrations. Simultaneously, it ensures that the descaling block maintains stable and effective descaling activity over a service life of more than 6 months.

[0009] The mass ratio of polycaprolactone, poly(butylene adipate / terephthalate), and modified starch is (2~5):1:1. PCL, as a hydrophobic semi-crystalline polymer, provides a structural framework with its slow degradation rate, while PBAT provides toughness and film-forming properties to prevent the bulk from cracking and disintegrating. Modified starch, as a hydrophilic pore-forming agent, absorbs water and dissolves to form microscopic water permeation channels inside the matrix.

[0010] The polycaprolactone has a weight-average molecular weight of 40,000 to 80,000 and a melting temperature of 55 to 65°C; the poly(butylene adipate / terephthalate) has a weight-average molecular weight of 80,000 to 120,000 and a melting temperature of 110 to 130°C; the modified starch is modified corn starch with a melting temperature of 60 to 90°C, a moisture content of 5% to 10%, and a degree of substitution of 0.02 to 0.15. This ensures that the starch can completely melt into a continuous phase during processing and form a dense coating on the active ingredients. PBAT with a molecular weight of 80,000 to 120,000 and a melting temperature of 110 to 130°C, after modification with PEG-600, softens and melts at around 100°C, providing a mechanical toughening effect. The modified corn starch's moisture content of 5% to 10% and degree of substitution of 0.02 to 0.15 ensure good dispersibility during starch slurry preparation and uniform distribution in the polyester matrix, laying the foundation for the subsequent formation of interconnected microscopic water permeation channels.

[0011] The polyethylene glycol 600 accounts for 5%–7% of the dry basis weight, and the Span-80 accounts for 2%–5% of the dry basis weight. PEG-600, as a melting point regulator, effectively inserts into the PBAT molecular chains to weaken their interactions and increase the free volume of the chain segments, thereby significantly reducing the melting point and processing viscosity of PBAT. This lowers the processing temperature of PBAT from 110–130°C to below 100°C, ensuring that no violent vaporization or boiling occurs during the dropwise addition of the aqueous starch slurry. Span-80, as an emulsifying compatibilizer, significantly reduces the interfacial tension between the hydrophobic polyester melt and the hydrophilic starch slurry, inhibiting aqueous phase aggregation and macroscopic phase separation, allowing the de-crystallizing functional components to be uniformly dispersed in the polyester matrix as micron or nano-sized particles. This overcomes the technical bottlenecks of poor compatibility, difficult molding, and poor sustained-release performance of traditional de-crystallizing block carriers, allowing the de-crystallizing functional components to be uniformly encapsulated and dispersed throughout the entire polyester matrix, achieving uniform sustained-release in later use.

[0012] The crystal removal block is disc-shaped or block-shaped, and the crystal removal functional component is uniformly dispersed in the sustained-release matrix component in the form of micron- or nano-sized particles.

[0013] Secondly, the present invention provides a method for preparing crystal removal blocks for long-term maintenance of crystallization defects in tunnel drainage systems, comprising the following steps: Step 1: Mix gluconic acid aqueous solution, acetylpropionic acid aqueous solution, polyaspartic acid aqueous solution and modified starch, stir evenly to obtain starch slurry; Step 2: Mix polycaprolactone, polybutylene adipate / terephthalate, polyethylene glycol 600 and Span-80, and heat to 95~105℃ to melt, to obtain polymer melt; Step 3: Under stirring conditions, slowly add the starch slurry prepared in Step 1 to the polymer melt prepared in Step 2. After the addition is complete, continue stirring and evaporating until the material is transformed into a uniform viscous paste. Step 4: The viscous paste obtained in Step 3 is shaped, cooled and solidified to obtain a crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems.

[0014] In step 3, the stirring speed is 200~300 r / min, and the stirring and evaporation time after the dripping is completed is 20~30 min; in step 4, the cooling and solidification temperature is 10~15℃, and the time is 30 min.

[0015] In step 3, the slow dripping rate is 1~5 mL / min; the temperature of the polymer melt is maintained at 100℃±2℃.

[0016] Thirdly, the present invention provides the application of the above-mentioned crystal removal block for long-term maintenance of crystallization diseases in tunnel drainage systems, in tunnel drainage systems, inspection wells or sedimentation tanks for removing calcium carbonate crystals and / or preventing crystal formation.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The crystal-removing block provided by this invention for long-term maintenance of crystallization defects in tunnel drainage systems comprises: 55%–65% crystal-removing functional components (gluconic acid + levulinic acid + polyaspartic acid), 25%–35% biodegradable slow-release matrix components (PCL + PBAT + modified starch), and 7%–12% external admixture components (PEG-600 + Span-80). All crystal-removing functional components are added in the form of a 60% aqueous solution. The three organic acids synergistically provide a mild and long-lasting ability to chelate calcium ions, dissolve calcium carbonate crystals, and inhibit the formation of new crystals. The fully biodegradable slow-release matrix constructed from PCL / PBAT / starch achieves long-term stable release for more than 6 months. The addition of PEG-600 and Span-80 solves the compatibility problem between the aqueous solution and the hydrophobic polyester, ensuring processing safety and product homogeneity. This invention addresses the problem of traditional powders easily absorbing moisture and clumping by utilizing hydrophobic polyester materials to form highly moisture-resistant solid granules. Regarding long-lasting effects, controlled release is achieved through microchannels formed by the dissolution of water-soluble components such as starch on the surface, transforming the "instantaneous burst and rapid depletion" of traditional acid solutions into a gradual release lasting several months. In terms of low corrosivity, by maintaining an extremely low and constant effective concentration release, combined with the gentle complexing effect of organic acids and the film-forming protection of polymer scale inhibitors, the severe acute corrosion caused to concrete pipes and polymer materials by the strong dissolution of traditional acid powders is avoided.

[0018] The preparation method provided by this invention involves pre-mixing a 60% high-concentration organic acid aqueous solution with starch to form a slurry, which is then slowly added dropwise to the polymer melt. This effectively avoids boiling and splashing caused by the instantaneous vaporization of water. Under the synergistic effect of PEG-600 lowering the melting temperature and Span-80 improving interfacial compatibility, the aqueous and oil phases form a uniform viscous paste under vigorous stirring, achieving micro / nano-scale uniform encapsulation of the acid solution in the polyester matrix. Finally, the solution is solidified and shaped by low-temperature cooling to obtain a dense, stable de-crystallized block.

[0019] The application provided by this invention involves directly placing the descaling blocks in areas prone to crystallization and scaling, such as tunnel drainage ditches, inspection wells, or sedimentation tanks. No complex dosing equipment is required. Under the long-term action of dynamically flowing water, the blocks undergo overall dissolution, release, and degradation from the outside in, continuously releasing trace amounts of organic acids and scale inhibitors. This dissolves existing calcium carbonate crystals and chelates calcium ions to prevent the formation of new crystals. The slow-release cycle of over 6 months significantly reduces the frequency of manual replacement. The fully biodegradable nature avoids secondary pollution and impacts on groundwater systems. The low-concentration continuous release mode significantly reduces the risk of corrosion to concrete and pipes, achieving preventative maintenance and long-term upkeep of crystallization problems in tunnel drainage systems. Attached Figure Description

[0020] Figure 1 The results for each embodiment under operating condition 1 are excluding the change in crystal mass; Figure 2 The results for each embodiment under operating condition 2 are excluding the change in crystal mass; Figure 3 The diagram shows the apparatus for Condition 1 and Condition 2, where: 1-corrosion resistant glass cup, 2-PVC board, 3-suspension rope, 4-support, 5-small electric fan (used in Condition 2), 6-crystal removal block; Figure 4 This is a diagram of the experimental apparatus used to prepare the crystal block of the present invention; in the diagram: 1-mechanical stirrer, 2-constant pressure dropping funnel, 3-thermometer, 4-fixed support, 5-three-necked flask, 6-oil bath.

[0021] Figure 5 This is a before-and-after comparison of the effect of the crystal removal block of this invention being placed into a circumferential blind pipe of a tunnel. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0025] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications in the art, unless otherwise stated. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, and "ratio" represents weight ratio. Unless otherwise specified, quantitative experiments in the following examples are performed in duplicate, and the results are averaged. I. Specific Implementation Methods Example 1: This embodiment provides a crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems, comprising the following components by mass percentage: 63% crystal removal functional component, 30% biodegradable slow-release matrix component, and 7% admixture component.

[0027] The de-crystallization functional components include gluconic acid (30% by dry weight), levulinic acid (25% by dry weight), and polyaspartic acid (8% by dry weight).

[0028] The biodegradable slow-release matrix components include PCL, PBAT, and bio-starch; the ratio of PCL, PBAT, and bio-starch is in the range of 2:1:1.

[0029] The external admixture components include PEG-600, accounting for 5% by dry weight; and Span-80, accounting for 2% by dry weight.

[0030] The gluconic acid, acetylpropionic acid, and polyaspartic acid were all prepared using a 60% acid aqueous solution as raw materials; PCL and PBAT were both made from micro powder with a particle size of 400 mesh; the bio-starch was made from modified corn starch with a moisture content of 5%, a degree of substitution of 0.1, and a particle size of 400 mesh.

[0031] The method for preparing the crystal block includes the following steps: Step 1, Prepare starch slurry Under room temperature conditions, according to the above mass ratio, weigh out 60% gluconic acid aqueous solution, 60% levulinic acid aqueous solution and 60% polyaspartic acid aqueous solution respectively, add them to beakers in sequence, stir and mix evenly to obtain mixed acid solution.

[0032] Weigh the modified corn starch according to the ratio, slowly add it to the above mixed acid solution, and stir and disperse it at room temperature to form a uniform starch slurry.

[0033] Step 2, preparing polymer melt Add the weighed PCL micro powder, PBAT micro powder, PEG-600 liquid and Span-80 liquid according to the specified ratio to a three-necked flask, place it in an oil bath and heat it to 100°C, turn on the mechanical stirrer and set the stirring speed to 150 r / min.

[0034] Step 3, addition and blending of starch slurry While the polymer melt is vigorously stirred at 100°C and 200 rpm, the starch slurry from step 1 is slowly added dropwise to the polymer melt using a constant-pressure dropping funnel. After the addition is complete, stirring and evaporation continue at 100°C for 25 minutes. Observe the state of the system; the process can be stopped when the material becomes a glossy, uniform, viscous paste.

[0035] Step 4, Molding and Curing After heating is stopped, before the material temperature drops to 70°C, it is quickly scraped out of the three-necked flask and pressed into the molding die. It is then placed in a low-temperature environment of 15°C to cool and solidify for 30 minutes. After complete hardening, it is demolded to obtain a de-crystallized block.

[0036] Example 2 This embodiment provides a de-crystallizing block (PCL:PBAT:starch = 3:1:1) for long-term maintenance of crystallization defects in tunnel drainage systems. By mass percentage, it comprises the following components: 63% de-crystallizing functional component, 30% biodegradable slow-release matrix component, and 7% admixture component.

[0037] The de-crystallization functional components include gluconic acid (30% by dry weight), levulinic acid (25% by dry weight), and polyaspartic acid (8% by dry weight).

[0038] The biodegradable slow-release matrix components include PCL, PBAT, and bio-starch; the ratio of PCL, PBAT, and bio-starch is in the range of 3:1:1.

[0039] The external admixture components include PEG-600, accounting for 5% by dry weight; and Span-80, accounting for 2% by dry weight.

[0040] The gluconic acid, acetylpropionic acid, and polyaspartic acid were all prepared using a 60% acid aqueous solution as raw materials; PCL and PBAT were both made from micro powder with a particle size of 400 mesh; the bio-starch was made from modified corn starch with a moisture content of 5%, a degree of substitution of 0.1, and a particle size of 400 mesh.

[0041] The method for preparing the crystal block includes the following steps: Step 1, Prepare starch slurry Under room temperature conditions, according to the above mass ratio, weigh out 60% gluconic acid aqueous solution, 60% levulinic acid aqueous solution and 60% polyaspartic acid aqueous solution respectively, add them to beakers in sequence, stir and mix evenly to obtain mixed acid solution.

[0042] Weigh the modified corn starch according to the ratio, slowly add it to the above mixed acid solution, and stir and disperse it at room temperature to form a uniform starch slurry.

[0043] Step 2, preparing polymer melt Add the weighed PCL micro powder, PBAT micro powder, PEG-600 liquid and Span-80 to a three-necked flask, place it in an oil bath, heat to 100°C, turn on the mechanical stirrer, and set the stirring speed to 150 r / min.

[0044] Step 3, addition and blending of starch slurry While the polymer melt is vigorously stirred at 100°C and 200 r / min, the starch slurry from step 1 is slowly dripped into the polymer melt using a constant-pressure dropping funnel. After the addition is complete, stirring and evaporation continue at 100°C for 25 min. Observe the state of the system; the process can be stopped when the material becomes a glossy, uniform, viscous paste.

[0045] Step 4, Molding and Curing After heating is stopped, before the material temperature drops to 70°C, it is quickly scraped out of the three-necked flask and pressed into the molding die. It is then placed in a low-temperature environment of 15°C to cool and solidify for 30 minutes. After complete hardening, it is demolded to obtain a de-crystallized block.

[0046] Example 3 This embodiment provides a crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems, comprising the following components by mass percentage: 63% crystal removal functional component, 30% biodegradable slow-release matrix component, and 7% admixture component.

[0047] The de-crystallization functional components include gluconic acid (30% by dry weight), levulinic acid (25% by dry weight), and polyaspartic acid (8% by dry weight).

[0048] The biodegradable slow-release matrix components include PCL, PBAT, and bio-starch; the ratio of PCL, PBAT, and bio-starch is in the range of 4:1:1.

[0049] The external admixture components include PEG-600, accounting for 5% by dry weight; and Span-80, accounting for 2% by dry weight.

[0050] The gluconic acid, acetylpropionic acid, and polyaspartic acid were all prepared using a 60% acid aqueous solution as raw materials; PCL and PBAT were both made from micro powder with a particle size of 400 mesh; the bio-starch was made from modified corn starch with a moisture content of 5%, a degree of substitution of 0.1, and a particle size of 400 mesh.

[0051] The method for preparing the crystal block includes the following steps: Step 1, Prepare starch slurry Under room temperature conditions, according to the above mass ratio, weigh out 60% gluconic acid aqueous solution, 60% levulinic acid aqueous solution and 60% polyaspartic acid aqueous solution respectively, add them to beakers in sequence, stir and mix evenly to obtain mixed acid solution.

[0052] Weigh the modified corn starch according to the ratio, slowly add it to the above mixed acid solution, and stir and disperse it at room temperature to form a uniform starch slurry.

[0053] Step 2, preparing polymer melt Add the weighed PCL micro powder, PBAT micro powder, PEG-600 liquid and Span-80 to a three-necked flask, place it in an oil bath, heat to 100°C, turn on the mechanical stirrer, and set the stirring speed to 150 r / min.

[0054] Step 3, addition and blending of starch slurry While the polymer melt is vigorously stirred at 100°C and 200 rpm, the starch slurry from step 1 is slowly added dropwise to the polymer melt using a constant-pressure dropping funnel. After the addition is complete, stirring and evaporation continue at 100°C for 25 minutes. Observe the state of the system; the process can be stopped when the material becomes a glossy, uniform, viscous paste.

[0055] Step 4, Molding and Curing After heating is stopped, before the material temperature drops to 70°C, it is quickly scraped out of the three-necked flask and pressed into the molding die. It is then placed in a low-temperature environment of 15°C to cool and solidify for 30 minutes. After complete hardening, it is demolded to obtain a de-crystallized block.

[0056] Example 4 This embodiment provides a crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems, comprising the following components by mass percentage: 63% crystal removal functional component, 30% biodegradable slow-release matrix component, and 7% admixture component.

[0057] The de-crystallization functional components include gluconic acid (30% by dry weight), levulinic acid (25% by dry weight), and polyaspartic acid (8% by dry weight).

[0058] The biodegradable slow-release matrix components include PCL, PBAT, and bio-starch; the ratio of PCL, PBAT, and bio-starch is in the range of 5:1:1.

[0059] The external admixture components include PEG-600, accounting for 5% by dry weight; and Span-80, accounting for 2% by dry weight.

[0060] The gluconic acid, acetylpropionic acid, and polyaspartic acid were all prepared using a 60% acid aqueous solution as raw materials; PCL and PBAT were both made from micro powder with a particle size of 400 mesh; the bio-starch was made from modified corn starch with a moisture content of 5%, a degree of substitution of 0.1, and a particle size of 400 mesh.

[0061] The method for preparing the crystal block includes the following steps: Step 1, Prepare starch slurry Under room temperature conditions, according to the above mass ratio, weigh out 60% gluconic acid aqueous solution, 60% levulinic acid aqueous solution and 60% polyaspartic acid aqueous solution respectively, add them to beakers in sequence, stir and mix evenly to obtain mixed acid solution.

[0062] Weigh the modified corn starch according to the ratio, slowly add it to the above mixed acid solution, and stir and disperse it at room temperature to form a uniform starch slurry.

[0063] Step 2, preparing polymer melt Add the weighed PCL micro powder, PBAT micro powder, PEG-600 liquid and Span-80 to a three-necked flask, place it in an oil bath, heat to 100°C, turn on the mechanical stirrer, and set the stirring speed to 150 r / min.

[0064] Step 3, addition and blending of starch slurry While the polymer melt is vigorously stirred at 100°C and 200 rpm, the starch slurry from step 1 is slowly added dropwise to the polymer melt using a constant-pressure dropping funnel. After the addition is complete, stirring and evaporation continue at 100°C for 25 minutes. Observe the state of the system; the process can be stopped when the material becomes a glossy, uniform, viscous paste.

[0065] Step 4, Molding and Curing After heating is stopped, before the material temperature drops to 70°C, it is quickly scraped out of the three-necked flask and pressed into the molding die. It is then placed in a low-temperature environment of 15°C to cool and solidify for 30 minutes. After complete hardening, it is demolded to obtain a de-crystallized block.

[0066] II. Performance Testing Based on the embodiments, the crystal removal blocks used for long-term maintenance of crystallization defects in tunnel drainage systems are subjected to performance testing in accordance with the method described.

[0067] 1. Experimental conditions and solution preparation The aqueous solutions in tunnel drainage pipes that easily crystallize are usually highly concentrated with calcium ions, exhibiting a supersaturated state, and their pH range is generally 9-13. This experiment selected an aqueous solution with a simulated pH of 11 for testing.

[0068] Preparation of crystallization aqueous solution: Add 2 L of deionized water and 0.5 kg of CaCl2 powder to a glass beaker to prepare a high-calcium ion easily crystallizing solution. Due to the high concentration of Ca... 2+ It will quickly react with OH - To prevent precipitation, solid NaOH powder was slowly and gradually added in portions with continuous stirring, and the pH was monitored with a pH meter until the solution pH stabilized at 11.0. At this point, a high-calcium ion, easily crystallizing aqueous solution was prepared. Subsequently, due to the dissolution and crystallization of CO2 from the air, the solution pH gradually decreased. Therefore, the pH value needed to be monitored every 8 hours, and adjusted by adding trace amounts of NaOH powder to maintain the pH within the range of 11.0 ± 0.1.

[0069] 2. Experimental Condition Settings A typical tunnel drainage system consists of circumferential blind pipes, longitudinal blind pipes, transverse blind pipes, and a central inspection well. Groundwater first enters the circumferential blind pipes from the surrounding rock, then flows through the longitudinal and transverse blind pipes. The transverse blind pipes connect to a central drainage ditch arranged along the tunnel centerline, and finally discharge outside the tunnel. These pipes are often accompanied by varying degrees of crystallization blockage. To evaluate the crystal removal efficiency and long-term effectiveness of this invention in different tunnel drainage pipes, two different experimental conditions were set up for verification: (1) Working condition 1: Simulated static water flow at the tunnel inspection well location Adopting such Figure 3 The experimental setup shown consists of the following components: a corrosion-resistant glass cup 1, a rectangular PVC board 2 (5cm × 2cm), a suspension rope 3, a support 4, and the crystal removal block of this invention 5.

[0070] Experimental steps: Assemble the support frame 4, fix one end of the suspension rope 3 to the support frame, and fix the other end to the PVC board 2. The PVC board 2 is completely immersed in the high-calcium solution, which is contained in a corrosion-resistant glass cup 1. After crystallization, it will adhere to the PVC board 2. At the beginning of the experiment, the crystal removal block 5 of this invention is added to the corrosion-resistant glass cup 1. This device is used to simulate the crystallization process of tunnel drainage pipes under static water flow.

[0071] (2) Working condition 2: Simulate the dynamic water flow in the central drainage ditch of the tunnel. Adopting such Figure 3 The experimental setup shown consists of the following components: a corrosion-resistant glass cup 1, a 5cm × 2cm rectangular PVC board 2, a suspension rope 3, a support 4, a small electric fan 5, and the crystal removal block of this invention 6.

[0072] Experimental steps: Assemble the support frame 4, fix one end of the suspension rope 3 to the support frame, and fix the other end to the PVC board 2. The PVC board 2 is completely immersed in the high-calcium solution, which is placed in a corrosion-resistant glass cup 1. Turn on the small electric fan 5 and adjust the speed to 100 r / min to simulate water flow. After crystallization, it will adhere to the PVC board 2. At the beginning of the experiment, the crystal removal block 5 of this invention is added to the corrosion-resistant glass cup 1. This device is used to simulate the low-flow-rate slow-flow crystallization process of a tunnel drainage pipe under continuous flowing water.

[0073] 3. Experimental Methods The specific experimental procedure is as follows: 25g of crystal removal block was placed in the beaker mentioned above. A blank group without the crystal removal block was set up for each of the two operating conditions. Before the experiment, the initial pH and Ca values ​​of the five parallel solutions were measured. 2+ Concentration and initial mass of PVC board After 15 days of reaction, the crystal blocks and PVC boards were removed and dried. The pH and Ca values ​​of each solution were measured again. 2+ Concentration, crystal mass quality, and PVC board quality The mass of the crystal was calculated. The crystal removal blocks and PVC boards were then immersed in the solution again for further testing. This process was repeated every 15 days until all crystal removal blocks were completely consumed under the same conditions. When Ca 2+ When the concentration reaches 80% of the initial concentration, replace with a freshly prepared high-calcium ion easily crystallizing solution and continue the experiment. Record the mass of the crystal block and the mass of the crystals for each group of experiments under both operating conditions. pH values ​​of each group of solutions.

[0074] The experimental results under the two operating conditions are as follows: (1) Sustained-release performance Depend on Figure 1 and Figure 2 As can be seen from the comparison of implementation cases 1-4, the slow-release properties of the decrystallized material are enhanced under both working conditions as the proportion of PCL increases. This indicates that PCL, as a hydrophobic polyester material, has a much lower hydrolytic degradation rate than PBAT in the ambient temperature groundwater environment of the tunnel. With the increase of its proportion, the overall hydrophobicity, structural density, and resistance to water erosion of the composite carrier are simultaneously enhanced, which can significantly slow down the infiltration rate of seepage water into the carrier and significantly prolong the physical cycle of drug release. In Example 4, the slow-release cycle can reach more than 360 days under working condition 1. In addition, the time for the decrystallized material to be consumed to zero under the action of flowing water is shortened, and the water flow impact accelerates the peeling off of the slow-release matrix, verifying that the water flow erosion affects the action time of the present invention. (2) Prevention of crystallization efficiency As shown in Tables 1 and 2, the anti-crystallization effect is immediately activated when the mass of the crystal block decreases. No crystals formed for the first few days in conditions 1 and 2 until the mass of the crystal block decreased to approximately 10g. At this point, the anti-crystallization functional components of the crystal block were nearly exhausted, leaving only a small amount of slow-release matrix components. The anti-crystallization effect weakened at this stage, and crystals began to adhere to the PVC board. Furthermore, the crystal growth rate accelerated over time. In addition, the crystal growth rate under flowing water was faster than that under still water, which is consistent with actual tunnel conditions.

[0075] Table 1: Crystal mass under operating condition 1 (static water flow) (unit: g)

[0076] Table 2: Crystal mass under operating condition 2 (dynamic water flow) (unit: g)

[0077] (3) pH value change characteristics Table 3 shows the minimum pH values ​​of the solution after crystal removal in various implementation cases for long-term maintenance of crystallization defects in tunnel drainage systems under two working conditions. The initial pH value of the easily crystallizing aqueous solution was 11.0 ± 0.1. After the crystal removal blocks of this invention took effect, the ternary organic acids neutralized the alkaline environment in the tunnel drainage system, and the pH value gradually decreased to around 6-7. Except for replacing with freshly prepared easily crystallizing aqueous solution, the pH value of the solution tended to stabilize. This proves that the crystal removal components are weak organic acids such as gluconic acid and levulinic acid. + Low degree of dissociation avoids strong acidity at its source; in addition, the biodegradable matrix forms a controlled-release structure, locking in de-crystallized components to achieve sustained release and maintaining low free H+ levels over the long term. + Concentration and corrosion inhibition further reduce the risk of corrosion.

[0078] Table 3: pH value changes of each embodiment under different operating conditions (minimum value recorded)

[0079] The experimental results above show that the crystal removal block of the present invention can achieve long-term sustained release under both static water flow (condition 1) and dynamic water flow (condition 2) conditions. In Example 4, the sustained release period under condition 1 can reach more than 360 days. During the effective period of the crystal removal block (mass greater than 10g), no crystals adhered to the surface of the PVC board, indicating that the crystal removal block of the present invention has excellent anti-crystallization effect. When the mass of the crystal removal block decreased to about 10g, the crystal removal functional components were nearly exhausted, the anti-crystallization effect weakened, and crystals began to appear on the PVC board. The crystal removal block of the present invention can adjust the pH value of a high-calcium alkaline solution (pH≈11) to a neutral to weakly acidic range of 6-7, and the pH value fluctuation is smooth with no strong acid impact, indicating that the present invention has good low-corrosion characteristics. From Example 1 to Example 4, as the proportion of PCL increases, the sustained release period gradually lengthens, the decrystallization effect lasts longer, and the pH adjustment becomes more moderate. This indicates that those skilled in the art can adjust the proportion of PCL, PBAT, and starch within the range of (2~5):1:1 according to actual needs to obtain decrystallization blocks that meet the requirements of different service cycles.

[0080] III. On-site Implementation Examples This invention relates to a case study of the application of a crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems, specifically for use in cases of blockages in tunnel drainage systems.

[0081] 1. Tunnel Overview A tunnel has been suffering from crystallization blockage for many years. The blockage has paralyzed the tunnel's drainage system, preventing groundwater from draining out of the tunnel. Increased water pressure has caused the invert arch to bulge, and water seeps from the road surface, causing a sudden surge of water and endangering traffic safety inside the tunnel. Traditional mechanical methods (high-pressure water jet cleaning) have been used to treat the blockage, but it recurs shortly afterward, failing to completely cure the crystallization problem.

[0082] 2. Deployment Plan The applicant placed the crystal-removing blocks prepared according to Example 3 of the present invention, used for long-term maintenance of crystallization defects in tunnel drainage systems, into the tunnel drainage system. The specific placement location and placement details are as follows: (1) Central drainage ditch placement At the location of crystallization in the central drainage ditch, depending on the degree of blockage, place 1 to 2 crystal removal blocks.

[0083] (2) Circumferential blind pipe placement Place a crystal removal block at the interface with the longitudinal pipe to ensure that all water flows over the surface of the crystal removal block, thereby achieving full release of the crystal removal functional components.

[0084] (3) Placement of side inspection wells Each well is filled with two crystal removal blocks, which are submerged below the normal water level to ensure that the water flow fully contacts the crystal removal blocks.

[0085] 3. Monitoring methods and indicators To systematically evaluate the field application effect of the crystal removal blocks of this invention, the following monitoring was conducted regularly before and after deployment: no crystal blockage occurred in the tunnel, and water flowed normally out of the pipe. Data on water flow rate, water pH, calcium ion concentration, and crystal removal block consumption were also measured. On the one hand, the crystals originally present in the tunnel softened and peeled off under the action of the crystal removal blocks, and were flushed out of the tunnel by the water flow, thus eliminating crystals. On the other hand, the crystal removal blocks maintained a stable concentration of effective components in the water, inhibiting the precipitation and adhesion of new crystals. Simultaneously, relying on their low-corrosion properties, they avoided corrosion damage to pipe materials, lining concrete, and internal reinforcing steel, ensuring smooth drainage of the longitudinal blind pipes and inhibiting crystal formation.

[0086] 4. Monitoring Results (1) Endoscopic inspection results: The internal crystallization of the circumferential blind pipe was inspected using an endoscope before and after the pipe. The results are as follows: Figure 5 As shown, by Figure 5 It can be seen that after the crystal-removing blocks of this invention have been applied for a period of time, the crystals in the blind tube are dissolved and eliminated. The test results show that the crystals originally present in the tunnel are gradually softened and peeled off under the action of the organic acids released by the crystal-removing blocks, and are discharged from the tunnel in the form of fine particles under the flushing of water, thus eliminating crystals; at the same time, the crystal-removing blocks continuously release effective components, maintain the stable concentration of gluconic acid, levulinic acid and polyaspartic acid in the water, inhibit the precipitation and adhesion of new crystals, thus inhibiting crystallization.

[0087] (2) Recovery status of drainage flow Table 4 shows the monthly drainage flow rate (expressed as a percentage of the design flow rate) measured by a portable ultrasonic flow meter installed at the outlet of the central drainage ditch. The flow monitoring data shows that after the crystal removal block was added, the drainage flow rate recovered month by month. The recovery rate was faster in the first 6 months (from 32% to 83%), and it remained stable between 85% and 90% in the following 6 months. This indicates that the crystal removal block continued to play a role in clearing drainage and inhibiting crystal formation during its effective working period.

[0088] Table 4: Changes in water flow rate at the outlet of the central drainage ditch in the tunnel

[0089] (3) Results of water quality pH monitoring Table 5 shows the pH monitoring results of water samples taken monthly at pH monitoring points set 10m and 100m downstream of the inspection well. The pH monitoring results indicate that after the addition of the de-crystal block, the pH value of the wastewater gradually decreased from the initial strongly alkaline (pH 10.8~11.2) to the neutral to slightly alkaline range (pH 7.3~8.5), meeting the requirements of the National Integrated Wastewater Discharge Standard (GB 8978-1996) (pH 6~9). Throughout the monitoring period, the pH value slowly decreased and then stabilized between 7.3 and 7.8, without any strong acid shock, verifying the low-corrosion characteristics of the de-crystal block of this invention and avoiding corrosion damage to pipes, lining concrete, and internal reinforcing steel.

[0090] Table 5: pH changes in water quality downstream of tunnel inspection wells

[0091] (4) Calcium ion concentration monitoring results Table 6 shows the monthly monitoring results of calcium ion concentration in the water sample taken at 10m and 100m downstream of the inspection well. The monitoring results indicate that after the crystal removal blocks were added, the calcium ion concentration in the water sample first increased sharply and then decreased and stabilized. Solid crystals dissolved under the softening and peeling action of the crystal removal blocks of this invention, releasing calcium into the water body. This calcium ion concentration accumulated until it reached a peak. As the crystals in the pipeline were completely dissolved, and there was no further dissolution or replenishment of solid calcium, the calcium ion concentration gradually decreased due to the continuous inflow of fresh groundwater from the surrounding rock, dilution by flowing water, and continuous discharge of high-calcium wastewater, eventually returning to its natural state. This verifies the crystal removal effect of this invention.

[0092] Table 6: Changes in calcium ion concentration in water downstream of tunnel inspection wells (mg / L)

[0093] (5) Monitoring of crystal consumption Table 7 shows the monthly weighing results of two crystal removal blocks placed in the inspection well (results are expressed as a percentage of the initial mass). The results demonstrate that the crystal removal blocks of this invention have an effective lifespan of over 12 months. In the humid, water-rich environment of tunnel drainage pipes, the crystal removal blocks do not rapidly disintegrate but rather slowly dissolve and gradually degrade with the water environment, releasing effective functional components at a uniform and sustained rate without being lost or dissipated all at once. The system is stable and resistant to water erosion; a single application can maintain the crystal removal and anti-clogging effect of the pipeline for a long time, eliminating the need for frequent replenishment and replacement, and significantly extending the maintenance cycle for clean and unobstructed tunnel drainage systems.

[0094] Table 7: Changes in crystal blocks inside tunnel inspection wells

[0095] Field application cases have verified the effectiveness of this invention for the long-term maintenance of crystallization defects in tunnel drainage systems in real tunnel drainage systems: Crystal removal: The crystals that were originally present in the tunnel are gradually softened and peeled off by the organic acids released by the crystal removal blocks, and are discharged from the tunnel by the water flow. Pipe endoscopy shows that the crystals are basically removed within 3 to 6 months.

[0096] Scale inhibition effect: In addition to the continuous release of effective components from the crystal blocks, it maintains a stable concentration of gluconic acid, levulinic acid and polyaspartic acid in the water, inhibits the precipitation and adhesion of new crystals, and prevents new crystal blockage from occurring within 12 months.

[0097] Water flow restoration: The drainage flow rate was restored from 32% (design flow rate) before the project was launched to 85% to 90%, and remained stable for more than 12 months, ensuring the smooth operation of the tunnel drainage system.

[0098] Low corrosion characteristics: The drainage pH is stable at 7.3~8.5, and no strong acid impact occurs. Relying on its low corrosion characteristics, corrosion damage to pipes, lining concrete and internal steel bars is avoided.

[0099] Long-term effectiveness: A single application can last for more than 12 months, significantly reducing the frequency and cost of manual maintenance, and realizing preventive maintenance and long-term maintenance of crystallization defects in tunnel drainage systems.

[0100] Environmental friendliness: Except for the PCL, PBAT and modified corn starch in the ingots, all are fully biodegradable materials and do not cause secondary pollution to the water environment around the tunnel.

[0101] This field implementation case fully demonstrates the practical value and superiority of the crystal removal block of this invention for long-term maintenance of crystallization diseases in tunnel drainage systems in the field of prevention and control of crystallization diseases in tunnel drainage systems. It solves prominent technical problems such as the inability of traditional mechanical methods to eradicate crystallization diseases, the high risk of corrosion from traditional chemical methods, and the non-degradability or short release cycle of traditional slow-release products.

[0102] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems, characterized in that, By weight percentage, it contains the following components: The de-crystallization functional component comprises 55% to 65%, and the de-crystallization functional component includes gluconic acid, levulinic acid, and polyaspartic acid; The sustained-release matrix component comprises 25% to 35%, and the sustained-release matrix component includes polycaprolactone, polybutylene adipate / terephthalate and modified starch; The external admixture component is 7% to 12%, and the external admixture component includes polyethylene glycol 600 and Span-80; In this mixture, gluconic acid, acetylpropionic acid, and polyaspartic acid are all added in the form of a 60% aqueous solution.

2. The crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems according to claim 1, characterized in that, The gluconic acid accounts for 25% to 35% of the dry weight, the levulinic acid accounts for 15% to 25% of the dry weight, and the polyaspartic acid accounts for 5% to 15% of the dry weight.

3. The de-icing agent for long-term maintenance of crystallization defects in tunnel drainage systems according to claim 2, characterized in that, The mass ratio of polycaprolactone, poly(butylene adipate / terephthalate) to modified starch is (2~5):1:

1.

4. The crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems according to claim 1, characterized in that, The polycaprolactone has a weight-average molecular weight of 40,000 to 80,000 and a melting temperature of 55 to 65°C; the poly(butylene adipate / terephthalate) has a weight-average molecular weight of 80,000 to 120,000 and a melting temperature of 110 to 130°C; the modified starch is modified corn starch with a melting temperature of 60 to 90°C, a moisture content of 5% to 10%, and a degree of substitution of 0.02 to 0.

15.

5. The crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems according to claim 1, characterized in that, The polyethylene glycol 600 accounts for 5% to 7% of the dry weight, and the Span-80 accounts for 2% to 5% of the dry weight.

6. The crystal removal block for long-term maintenance of crystallization defects in tunnel drainage systems according to claim 1, characterized in that, The crystal removal block is disc-shaped or block-shaped, and the crystal removal functional component is uniformly dispersed in the sustained-release matrix component in the form of micron- or nano-sized particles.

7. The method for preparing crystal-removing blocks for long-term maintenance of crystallization defects in tunnel drainage systems according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Mix gluconic acid aqueous solution, acetylpropionic acid aqueous solution, polyaspartic acid aqueous solution and modified starch, stir evenly to obtain starch slurry; Step 2: Mix polycaprolactone, polybutylene adipate / terephthalate, polyethylene glycol 600 and Span-80, heat and melt to obtain polymer melt; Step 3: Under stirring conditions, the starch slurry prepared in step 1 is slowly added dropwise to the polymer melt prepared in step 2, and stirred and evaporated to obtain a viscous paste. Step 4: The viscous paste obtained in Step 3 is shaped, cooled and solidified to obtain the crystal removal block used for long-term maintenance of crystallization defects in tunnel drainage systems.

8. The method for preparing crystal-removing blocks for long-term maintenance of crystallization defects in tunnel drainage systems according to claim 7, characterized in that, In step 2, the melting temperature is 95~105℃; in step 3, the stirring speed is 200~300 r / min; and the time for continued stirring and evaporation after the dripping is completed is 20~30 min; in step 4, the cooling and solidification temperature is 10~15℃, and the time is 30 min.

9. The method for preparing crystal-removing blocks for long-term maintenance of crystallization defects in tunnel drainage systems according to claim 7, characterized in that, In step 3, the slow dripping rate is 1~5 mL / min; the temperature of the polymer melt is maintained at 100℃±2℃.

10. The crystal removal block according to any one of claims 1 to 6 for long-term maintenance of crystallization defects in tunnel drainage systems is used in tunnel drainage systems, inspection wells or sedimentation tanks for removing calcium carbonate crystals and / or preventing crystal formation.

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