CN115030132B - Low-carbon all-weather rock-soil stabilization method based on ultra-low swelling hydrogel - Google Patents
Low-carbon all-weather rock-soil stabilization method based on ultra-low swelling hydrogel Download PDFInfo
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Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/12—Consolidating by placing solidifying or pore-filling substances in the soil
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/04—Acids; Metal salts or ammonium salts thereof
- C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A10/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE at coastal zones; at river basins
- Y02A10/23—Dune restoration or creation; Cliff stabilisation
Abstract
A low-carbon all-weather rock-soil stabilization method based on ultra-low swelling hydrogel belongs to the field of composite materials and civil engineering. The method specifically comprises the following steps: respectively dissolving hydrogel monomers with hydrogen bond donor characteristics and hydrogen bond acceptor characteristics in water to prepare hydrogen bond donor monomer stock solution and hydrogen bond acceptor monomer stock solution; mixing hydrogen bond donor monomer stock solution, hydrogen bond acceptor monomer stock solution, cross-linking agent and initiator according to a proper proportion to obtain hydrogel precursor mixed solution; the precursor mixed solution is mixed with the rock soil for reinforcement and stabilization. The volume expansion of the hydrogel after soaking can be as low as 0%, the tensile strength is basically unchanged, and the soil reinforced by the hydrogel still maintains good strength after soaking in water for 72 hours.
Description
Technical Field
The invention relates to a preparation method of ultra-low swelling hydrogel and a technology for reinforcing low-carbon rock soil by using the hydrogel, so that the structural stability of the hydrogel can be greatly improved under various climatic conditions. The invention belongs to the fields of composite materials and civil engineering.
Background
The structural stability of the geotechnical material has great influence on production construction and ecological environment. For example, instability of the rock-soil material as a load-bearing unit may cause landslide, foundation settlement, etc., severely threatening life safety; the instability of the rock-soil surface layer can cause water and soil loss, sand lifting in the presence of strong wind and other environmental problems. Therefore, a technology capable of effectively stabilizing the rock-soil material has been the focus of scientific research.
The conventional rock-soil reinforcement method mainly depends on cement and concrete materials, and is applied to a reinforced system by spraying, pouring and other methods, so that the mechanical properties of the reinforced system are improved after the reinforced system is solidified. Although this type of technology is very popular, it has significant adverse environmental effects. The energy consumption for cement and ready-mixed concrete production is huge. Therefore, it is needed to find a low-carbon geotechnical reinforcing agent capable of replacing cement and concrete, reducing damage to the environment caused by geotechnical reinforcement and promoting benign development of the whole technical chain and industrial chain.
In recent years, hydrogel materials have been increasingly used for soil stabilization. Hydrogels are materials composed of hydrophilic polymer networks that are capable of adsorbing large amounts of water. In practical applications, the hydrogel precursor is usually prepared by using a small molecular monomer or an uncrosslinked polymer, and then added into the soil to be reinforced. The liquid phase hydrogel precursor can be polymerized, crosslinked and cured through in-situ reaction, and plays a role in binding rock and soil particles and filling holes of the material. Previous researches prove that the hydrogel adhesive can effectively improve the soil strength, and the reinforced soil strength can be equivalent to that of portland cement. Meanwhile, the hydrogel can be used for replacing cement, so that carbon emission in raw material production can be effectively reduced, and many hydrogel raw materials can be directly extracted from plants. Although hydrogel adhesives have numerous advantages, their poor strength in water has prevented practical use. When the common hydrogel is soaked in water, a large amount of water is absorbed, the volume is rapidly expanded (generally called swelling), and the mechanical properties are rapidly deteriorated; if the hydrogel is distributed in the soil, the soil structure may be broken through due to volume expansion. The combined action of the two adverse factors makes the hydrogel as a geotechnical hardening agent unable to survive in humid, rainy and water soaking environments, and the application geographical and climate range is greatly limited.
Aiming at the requirements and technical bottlenecks, the inventor of the application develops a novel hydrogel with good mechanical strength and ultra-low swelling rate, and uses the hydrogel to perform rock-soil reinforcement test. The research shows that the volume expansion of the hydrogel after soaking can be as low as 0%, the tensile strength is basically unchanged, and the soil reinforced by the hydrogel still maintains good strength after soaking in water for 72 hours. The hydrogel system can be used as a low-carbon all-weather rock-soil stabilizer, and fills the technical blank at home and abroad.
Disclosure of Invention
The invention provides a method for preparing novel ultra-low swelling hydrogel. The method introduces intermolecular hydrogen bonds into the hydrogel to form covalent-non-covalent double cross-linking, so as to reduce the water absorption capacity of hydrophilic groups. Meanwhile, hydrophobic groups are introduced at the ortho positions of part of hydrophilic groups, so that water molecules are prevented from attacking intermolecular hydrogen bonds and stabilizing the hydrogen bond action; proper spatial arrangement of hydrophobic groups can also induce hydrophobic agglomeration of polymer chains, and micron-sized phase separation and hydrophobic phases are formed inside the hydrogel. The destruction of the hydrophobic phase requires additional energy to provide a phase separation toughening effect, further improving the resistance of the hydrogel to swelling. Here the swelling ratio (S) w ) Defined by the formula:
wherein M is w ，M i The hydrogel full swelling mass and initial mass, respectively. The preparation principle of the ultra-low swelling hydrogel is shown in figure 1.
The low-carbon all-weather rock-soil stabilization method based on the ultra-low swelling hydrogel comprises the following steps:
(1) Preparing hydrogen bond donor and hydrogen bond acceptor monomer stock solution
Respectively dissolving hydrogel monomers with hydrogen bond donor characteristics and hydrogen bond acceptor characteristics in water to prepare hydrogen bond donor monomer stock solution and hydrogen bond acceptor monomer stock solution; wherein the hydrogen bond donor is generally a polymerizable monomer having a carboxylic acid group, the hydrogen bond donor may or may not contain a hydrophobic group, preferably contains a hydrophobic group; hydrogen bond donors that do not contain a hydrophobic group, such as acrylic acid (AAc), hydrogen bond donors that contain a hydrophobic group, such as methacrylic acid (MAAc), crotonic acid, and the like; the hydrogen bond acceptor is typically a polymerizable monomer having an amide group, such as acrylamide (AAm), N-dimethylacrylamide, N-ethylacrylamide, etc.; the mass percentage concentration of the monomer stock solution is 14.3-48.9%, and the higher the concentration of the monomer stock solution is, the higher the mechanical strength of the prepared hydrogel is.
(2) Mixing the reactants according to a certain proportion to prepare the hydrogel precursor
Mixing hydrogen bond donor monomer stock solution, hydrogen bond acceptor monomer stock solution, cross-linking agent and initiator according to a proper proportion to obtain hydrogel precursor mixed solution; the molar ratio of hydrogen bond donor monomer to hydrogen bond acceptor monomer can be adjusted between 9:1 and 1:9, preferably 1:1 wherein the relative molar ratio of hydrogen bond donor to acceptor determines the density of intermolecular hydrogen bonds formed, the closer the ratio is to 1, the better the effect of intermolecular hydrogen bonds formed; the crosslinking agent may be selected from conventional crosslinking agents, preferably N, N' -methylenebisacrylamide (Bis), polyethylene glycol diacrylate, and the like. The cross-linking agent influences the final hardness and the swelling rate of the hydrogel, the higher the concentration of the cross-linking agent is, the higher the final hardness of the hydrogel is, the lower the swelling rate is, and the mass percentage of the cross-linking agent in the hydrogel precursor mixed solution can be adjusted between 0.76% and 14.8%; the initiator is selected from Ammonium Persulfate (APS) and tetramethyl ethylenediamine (TEMED). The mass percentage of the initiator in the hydrogel precursor mixed solution can be 1% -4%.
(3) Mixing the precursor with rock soil for stabilization
In the experiments, the soil environment was simulated with standard sand (GB/T176771-1999 ISO 679:1989). The standard sand was placed in a container, and 15ml of the hydrogel precursor was added to the reaction solution per 75g of standard sand. In practical application, the amount of the precursor can be adjusted according to the requirement, and 10-20ml of the hydrogel precursor mixed solution is preferably added to 75g of standard sand. The mixture is left for a period of time to allow the hydrogel to fully cure. The time required for curing depends on the composition of the hydrogel precursor and the concentration of the individual components, and is generally between 12 and 48 hours. The formed standard sand block was then removed from the container and left to dry naturally in air at room temperature for 7 days or in an oven at 60 ℃ for 1 day to give a hydrogel-stabilized soil sample. An Unconfined Compressive Strength (UCS) was measured thereon to verify the reinforcing effect. To verify the stability of the above samples in water, dried columnar samples were taken, immersed in deionized water for 72 hours, taken out and their UCS was measured immediately. To verify the stability of the samples in a high temperature environment, the dried columnar samples were placed in an oven at 60 ℃ for 7 days, and their UCS was measured immediately after removal.
Drawings
FIG. 1 is a schematic diagram of the principle of ultra-low swelling hydrogel formation.
FIG. 2 shows the tendency of swelling ratio of hydrogels with relative concentration of hydrogen bond donor.
FIG. 3 IR spectrum of poly MAAc-co-AAm gel.
Fig. 4 microscopic and electron microscopic observation of submicron particulate hydrophobic phase.
FIG. 5 shows the variation of the swelling ratio of hydrogels with the concentration of the crosslinking agent.
FIG. 6 variation of intensity of poly MAAc-co-AAm gel before and after soaking.
Fig. 7 is a photograph of a dry sand column.
FIG. 8 is a photograph of a sand column after 72h immersion in water.
FIG. 9 shows the compression curve of the sand column before and after soaking in example 1.
FIG. 10 UCS of the sand column before and after soaking and after heat treatment in example 1.
FIG. 11 shows the compression curve of the sand column before and after soaking in example 2.
FIG. 12 UCS of the sand column before and after soaking and after heat treatment in example 2
FIG. 13 is a photograph of the sand column before and after soaking in comparative example 1.
FIG. 14 is a compression curve of the sand column before and after soaking in comparative example 1.
Detailed Description
The present invention will be further illustrated with reference to the following examples, but the present invention is not limited to the following examples.
Example 1:
preparing MAAc and AAm stock solutions with mass fractions of 32.3% and 28.6% respectively. Mixing the two solutions according to the volume ratio of 10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9 and 0:10 to obtain a series of mixed solutions, wherein the total molar concentration of MAAc and AAm in each mixed solution is the same. To 10mL of each mixture was added 200mg of N, N' -methylenebisacrylamide, 100. Mu.L of TEMED and 1.9mL of deionized water, followed by 1.0mL of 10% APS, followed by mixing and standing to obtain a series of hydrogels. The swelling ratio was measured, and the left graph of FIG. 2 was obtained. Similarly, AAc and AAm stock solutions were formulated at mass fractions of 28.9% and 28.6%, respectively. Mixing the two materials according to the volume ratio of 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9 and 0:10 to obtain series mixed solutions, adding 200mg of N, N' -methylenebisacrylamide into 10mL of each mixed solution, uniformly mixing 100 mu L of TEMED and 1.9mL of deionized water, uniformly mixing the mixed solutions, adding 1.0mL of 10% APS, and standing to obtain the series hydrogel. The swelling ratio was measured, and the right graph of FIG. 2 was obtained. Note that the total molar concentrations of hydrogen bond donor and acceptor in the above two series of hydrogels are the same.
The formation of intermolecular hydrogen bonds can effectively reduce the swelling rate of the hydrogel. If the molar concentration of the monomers in the reaction mixture is kept unchanged and the relative concentrations of the hydrogen bond donor and the acceptor are changed, the swelling ratio of the prepared hydrogel can be observed to be equal to the concentrations of the hydrogen bond donor and the acceptor when the relative concentrations of the hydrogen bond acceptor are increased, and then the swelling ratio is increased after the decrease (figure 2). The existence of hydrophobic groups on the hydrogen bond donor can effectively stabilize intermolecular hydrogen bonds, reduce the possibility of damaging the hydrogen bonds by water molecules, and further reduce the swelling rate of the hydrogel. As the swelling ratio of hydrogels prepared with MAAc and AAm was significantly lower than those prepared with AAc and AAm (fig. 2). The hydrogen bond formed between the carboxyl group and the amide can also be confirmed by fourier transform infrared spectroscopy. As shown in fig. 3, compared with the spectrum obtained by fitting pure polymethacrylic acid and pure polyacrylamide, c=o stretching peaks in the experimentally prepared hydrogel undergo a red shift, verifying the formation of intermolecular hydrogen bonds.
The presence of hydrophobic groups on the hydrogen bond donor may also promote hydrophobic agglomeration of the polymer chains to form a hydrophobic phase (fig. 1). Taking a sample with a volume ratio of MAAc to AAm of 6:4 in FIG. 2, a blue shift in C-H stretching of the hydrogel relative to the fitted spectrum was observed in the IR spectrum, demonstrating the interaction between the methyl groups (FIG. 3). The generation of submicron particulate hydrophobic phase was observed under both microscope and electron microscope (fig. 4). The existence of the hydrophobic phase enables hydrogen bonds among molecules to be accumulated more tightly, and the difficulty of attack of water molecules is increased; meanwhile, the hydrogel is required to overcome additional hydrophobic acting force after swelling, so that the swelling resistance of the hydrogel is further improved.
Example 2:
preparing MAAc and AAm stock solutions with mass fractions of 32.3% and 28.6%, respectively, and mixing the MAAc and the AAm stock solutions according to a volume ratio of 1:1. To 10mL of the mixture, 0, 50, 100, 150, 200, 300, 500mg of N, N' -methylenebisacrylamide was added, 100. Mu.L of TEMED,1.9mL of deionized water, and 1.0mL of 10% APS were added, followed by mixing and standing, and a series of hydrogels with different Bis concentrations were obtained. The swelling ratio was measured to obtain FIG. 5, which demonstrates that increasing the concentration of the crosslinking agent can reduce the swelling ratio of the hydrogel, with the other components in the reaction mixture remaining unchanged. At the appropriate crosslinker concentration, the swelling ratio of the hydrogels can be as low as 100%, i.e., no volume expansion.
The mechanical strength of the samples obtained in this example was almost unchanged after soaking in water for 72h (FIG. 6).
Example 3:
preparing methacrylic acid and acrylamide stock solutions with mass fractions of 48.9% and 44.4% respectively. 7.2mL of methacrylic acid stock solution and 4.8mL of acrylamide stock solution were mixed, 480mg of N, N' -methylenebisacrylamide, 240. Mu.L of TEMED, 960. Mu.L of deionized water were added and mixed, and 2.4mL of 10% APS was added and mixed. Standard sand was filled into a cylindrical container having an inner diameter of 35.4 mm. 15mL of this mixture was added dropwise to 75g of standard sand, gently tapped to remove air bubbles, and allowed to stand for 12h. The formed sand column was taken out and dried at room temperature for 7 days to obtain a dried sample (fig. 7). The soil reinforcement sample with high strength can be obtained by using the formula, UCS can reach 2.9MPa, and fracture energy can reach 177.5kJ/m 3 . After 72h of soaking, the column volume was not significantly changed (FIG. 8), UCS was still maintained at 802kPa, and the breaking energy was 70kJ/m 3 (FIG. 9). The dried sand column was placed in an oven for high temperature stability experiments with little variation in UCS within error before and after baking (fig. 10).
Example 4:
preparing methacrylic acid and acrylamide stock solutions with mass fractions of 19.3% and 16.7% respectively. 4.8mL of methacrylic acid stock solution and 7.2mL of acrylamide stock solution were mixed, 120mg of N, N' -methylenebisacrylamide, 60. Mu.L of TEMED,2.94mL of deionized water were added and mixed well, and 0.6mL of 10% APS was added and mixed well. Standard sand was filled into a cylindrical container having an inner diameter of 35.4 mm. 15mL of this mixture was added dropwise to 75g of standard sand, gently tapped to remove air bubbles, and allowed to stand for 48h. The formed sand column was taken out and dried at room temperature for 7 days to obtain a dried sample. The soil reinforcement sample with medium strength can be obtained by using the formula, UCS can reach 1.1MPa, and the breaking energy can reach 80kJ/m 3 . After 72 hours of soaking, the volume of the sand column has no obvious change, UCS is kept at 150kPa, and the breaking energy is 25kJ/m 3 (FIG. 11) it is notable that the dry weight of the reactants for this formulation is only 3.7% of standard sand, with a high economy. Meanwhile, the soaked sand column can resist 30% compression deformation and has high elasticity. The dried sand column was placed in an oven for high temperature stability experiments with little variation in UCS within error before and after baking (fig. 12).
Comparative example 1:
to verify the advantages of the ultra-low swelling hydrogels, the traditional hydrogel soil-reinforcing agents were taken as a comparison. Preparing an acrylamide stock solution with the mass fraction of 16.7 percent. 12mL of acrylamide stock solution was added with 120mg of N, N' -methylenebisacrylamide, 60. Mu.L of TEMED,2.94mL of deionized water, and then 0.6mL of 10% APS was added and mixed. Standard sand was filled into a cylindrical container having an inner diameter of 35.4 mm. 15mL of this mixture was added dropwise to 75g of standard sand, gently tapped to remove air bubbles, and allowed to stand for 48h. The formed sand column was taken out and dried at room temperature for 7 days to obtain a dried sample. The soil-consolidated sample obtained using this formulation can reach 1.2MPa in dry state, but swells due to the severe water absorption of the hydrogel after 3 hours of soaking (fig. 13), and UCS is 40kPa (fig. 14) after 72 hours of soaking, only 5% in example 1 and 27% in example 2. It follows that the general hydrogels do not achieve the ability to maintain soil strength all the time.
Claims (6)
1. The low-carbon all-weather rock-soil stabilization method based on the ultra-low swelling hydrogel is characterized by comprising the following steps of:
(1) Preparing hydrogen bond donor and hydrogen bond acceptor monomer stock solution
Respectively dissolving hydrogel monomers with hydrogen bond donor characteristics and hydrogen bond acceptor characteristics in water to prepare hydrogen bond donor monomer stock solution and hydrogen bond acceptor monomer stock solution;
(2) Mixing the reactants according to a certain proportion
Mixing hydrogen bond donor monomer stock solution, hydrogen bond acceptor monomer stock solution, cross-linking agent and initiator according to a proper proportion to obtain hydrogel precursor mixed solution; the molar ratio of the hydrogen bond donor monomer to the hydrogen bond acceptor monomer is between 9:1 and 1:9, and the mass percentage of the cross-linking agent in the hydrogel precursor mixed solution is regulated between 0.76 percent and 14.8 percent; the mass percentage of the initiator in the hydrogel precursor mixed solution is 1% -4%;
(3) Mixing the hydrogel precursor mixed solution with rock soil, and standing at room temperature to completely solidify the hydrogel so as to strengthen the rock soil;
intermolecular hydrogen bonds are introduced into the hydrogel to form covalent-non-covalent double cross-links, so that the water absorption capacity of hydrophilic groups is reduced; meanwhile, hydrophobic groups are introduced at the ortho positions of part of hydrophilic groups, so that water molecules are prevented from attacking intermolecular hydrogen bonds and stabilizing the hydrogen bond action; proper spatial arrangement of hydrophobic groups can also induce hydrophobic agglomeration of high molecular chains, and micron-sized phase separation and hydrophobic phases are formed inside the hydrogel; the hydrophobic phase is destroyed, so that extra energy is required to be provided, the split-phase toughening effect is achieved, and the resistance of the hydrogel to swelling is further improved;
the hydrogen bond donor in the step (1) is a polymerizable monomer with a carboxylic acid group, the hydrogen bond donor contains a hydrophobic group or does not contain a hydrophobic group, the hydrogen bond donor contains acrylic acid (AAc) without a hydrophobic group, the hydrogen bond donor contains methacrylic acid (MAAc) with a hydrophobic group and crotonic acid; the hydrogen bond acceptor is acrylamide (AAm), N-dimethylacrylamide, N-ethylacrylamide.
2. The low-carbon all-weather rock-soil stabilization method based on ultra-low swelling hydrogels as claimed in claim 1, wherein the mass percentage concentration of the monomer stock solution in step (1) is 14.3% -48.9%.
3. The ultra-low swelling hydrogel-based low carbon all-weather geotechnical stabilization method according to claim 1, wherein the molar ratio of the hydrogen bond donor monomer to the hydrogen bond acceptor monomer in step (2) is 4:6 to 6:4.
4. The method for low-carbon all-weather geotechnical stabilization based on ultra-low swelling hydrogels according to claim 1, characterized in that the cross-linking agent of step (2) is selected from N, N' methylenebisacrylamide (Bis); the initiator is selected from Ammonium Persulfate (APS) and tetramethyl ethylenediamine (TEMED).
5. The ultra-low swelling hydrogel-based low-carbon all-weather geotechnical stabilization method according to claim 1, wherein 10-20ml of the hydrogel precursor mixture is added per 75-g standard sand in step (3).
6. A rock soil obtainable by the method according to any one of claims 1 to 5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN109535306A (en) * | 2018-11-19 | 2019-03-29 | 山东大学 | A kind of expandable polymeric injecting paste material and preparation method for the prominent Water outburst treatment of high-pressure high-flow karst |
| CN112608495A (en) * | 2020-11-10 | 2021-04-06 | 深圳大学 | Hydrogel composite material, preparation method and application |
| CN113336483A (en) * | 2021-05-20 | 2021-09-03 | 山东高速青岛建设管理有限公司 | High-pressure jet grouting pile repairing particle material and preparation method and application thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109535306A (en) * | 2018-11-19 | 2019-03-29 | 山东大学 | A kind of expandable polymeric injecting paste material and preparation method for the prominent Water outburst treatment of high-pressure high-flow karst |
| CN112608495A (en) * | 2020-11-10 | 2021-04-06 | 深圳大学 | Hydrogel composite material, preparation method and application |
| CN113336483A (en) * | 2021-05-20 | 2021-09-03 | 山东高速青岛建设管理有限公司 | High-pressure jet grouting pile repairing particle material and preparation method and application thereof |
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