Eicp-based fractured rock reinforcement and filling medium and method

Abstract

The application discloses a kind of fissured rock reinforcing filling medium and method based on EICP, the filling medium includes reinforcing solution, and the filling of mixed reinforcing solution;The reinforcing solution contains urease, carbonate ion and calcium ion;The filling is sandstone particle or polyvinyl alcohol fiber section, or the mixture of two. The method includes steps S1: configuration contains urease, carbonate ion and calcium ion reinforcing solution, step S2: the reinforcing solution of step S1 configuration is mixed with filling, to obtain filling medium;Step S3: using filling medium fills rock fissure;Step S4: using reinforcing solution to soak the rock fissure after filling, reinforcement is carried out.The application promotes calcium carbonate crystallization generation by filling medium as target on the basis of EICP technology, improves the efficiency of EICP technology reinforcing rock body fissure, expands the use prospect and range of EICP technology in rock body reinforcement.

Description

Technical Field

[0001] This invention belongs to the field of rock reinforcement mechanical engineering technology, specifically relating to a fracture rock reinforcement filling medium and method based on EICP. Background Technology

[0002] To improve the strength and stability of rock masses, reinforcement of jointed rock masses is an essential engineering method. Grouting is a widely used reinforcement technology in rock mass engineering fields such as tunnels, water conservancy and hydropower, and mining. Based on the different grouting materials, grouting can be divided into two main categories: cement grouting and chemical grouting. Cement grouting is widely used due to its abundant material sources, convenient grout preparation, low cost, and high bonding strength. However, cement grout has high viscosity and contains large solid particles, making it difficult to penetrate the fine cracks in the rock mass. Chemical grouting, on the other hand, has advantages such as low viscosity, good injectability, and the ability to inject into the fine pores of the rock mass. However, the grout materials used in chemical grouting have a certain degree of toxicity, which can easily pollute the underground environment. It is also more expensive, and the effective lifespan of chemical grouting is only a few decades. In recent years, with the continuous increase in efforts to protect the underground environment, researching a low-cost, injectable, and environmentally friendly grouting material for jointed rock masses has become a key issue that urgently needs to be addressed in rock mass reinforcement engineering.

[0003] Microbial geotechnical technology is an engineering application technique that uses the biochemical reactions of microorganisms to solve geotechnical problems. Based on different principles, microbial geotechnical technology is further subdivided into three categories: microbial mineralization, microbial gas production, and microbial film formation. Due to its wide applicability and strong operability, microbial mineralization has been the most studied among microbial geotechnical technologies. Currently, microbial geotechnical technology has been applied to engineering problems such as foundation treatment, cultural relic protection, concrete self-healing, soil pollution, and soil reinforcement, opening up new avenues for solving engineering problems and proposing new solutions.

[0004] Currently, microbial geotechnical techniques are mainly applied to soil research, but their application to rock fracture reinforcement is still in its early stages. Existing research primarily focuses on using Bacillus buski as the primary producer of urease, combined with a cementing solution containing urea, calcium chloride, and other materials to induce calcium carbonate precipitation. However, urease is not only found in microorganisms like Bacillus buski; its sources in nature are diverse and widespread, including in plant seeds such as sword bean and soybean. Researchers extracted and purified urease from plants, then mixed it with a calcium ion-containing solution, discovering results similar to those induced by Bacillus buski and other microorganisms. This technique is termed the Enzyme-Induced Calcite Precipitation Method (EICP).

[0005] Currently, EICP technology is mostly used in soil and sand reinforcement, such as Chinese patent application number 202210562110.1, which discloses a research method and application of soil reinforcement based on improved EICP technology, and Guo Xin's master's thesis, which records the experimental research on the regulation of calcium carbonate solidification sand induced by plant urease at different temperatures. However, there has been no research on EICP for rock fissure reinforcement. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an EICP-based filling medium and method for reinforcing fractured rocks, thereby optimizing existing rock reinforcement technologies to address issues such as poor grout penetration, severe environmental pollution, and high difficulty in preparation. It also improves upon the previous application of EICP to rock reinforcement, which resulted in slow calcium carbonate crystallization and poor targeting, thus increasing the efficiency of EICP in reinforcing fractured rock masses.

[0007] To achieve the above objectives, the present invention employs the following solution:

[0008] EICP-based fractured rock reinforcement filling media, including reinforcement solutions and fillers mixed with the reinforcement solutions;

[0009] The reinforcement solution contains urease, carbonate ions, and calcium ions;

[0010] The filler is sandstone particles or polyvinyl alcohol fiber segments, or a mixture of the two.

[0011] Further optimization involves the filler being a mixture of sandstone particles and polyvinyl alcohol fiber segments.

[0012] Further optimization resulted in a solid-solution to filler mass ratio of: polyvinyl alcohol fiber segments : sandstone particles : reinforcement solution = 1:3:3. Preliminary tests conducted before the formal experiment confirmed that this filler ratio resulted in the best reinforcement effect. As a fiber material, polyvinyl alcohol fibers have a small mass per unit volume; a small amount of fiber would occupy a large volume, while a large amount of fiber would aggregate, making it difficult to mix evenly with sandstone particles. Furthermore, polyvinyl alcohol fibers are added as an auxiliary material into the small gaps of sandstone particles, providing a targeted guide for calcium carbonate precipitation in the reinforcement solution. Considering that its price and acquisition difficulty are higher than sandstone particles, the mass ratio was set at 1:3. A 1:1 ratio of sandstone particles to reinforcement solution is a result of considering the ease of mixing, flowability, and strength of the filling medium. A 1:1 ratio of sandstone particles to reinforcement solution ensures thorough mixing and allows flow into small pores before cementation, resulting in good integrity of the reinforced sample.

[0013] Further optimization involves a reinforcement solution in which the mass concentration ratio of soybean flour (with equivalent urease activity), carbonate ions, and calcium ions is 5:6:4.

[0014] A method for reinforcing fractured rock, based on the aforementioned EICP-based fractured rock reinforcement filling medium, includes the following steps:

[0015] Step S1: Prepare a consolidation solution containing urease, carbonate ions, and calcium ions, specifically including:

[0016] Step S1.1: Prepare urease solution

[0017] Step S1.2: Determine urease activity and screen out the urease solution with the best urease activity ratio;

[0018] Step S1.3: Mix the CaCl2 solution, urea solution and the optimal ratio of urease solution selected in step S1.2 to obtain the reinforcement solution;

[0019] Step S2: Mix the reinforcing solution prepared in step S1 with the filler to obtain the filling medium;

[0020] Step S3: Fill the rock fissures with a filling medium;

[0021] Step S4: Use a reinforcing solution to impregnate and fill the rock fissures.

[0022] Further optimization involves step S1.1, which involves preparing the urease solution. Specifically, freshly ground soybean flour is divided into n portions, and deionized water is added to each portion to prepare soybean flour solutions of different concentrations. The total mass of the soybean flour solutions is kept constant. All soybean flour solutions are stirred and centrifuged. The supernatant is then filtered through medical gauze to obtain urease solutions of different concentrations. Determining the urease activity in soybean residue is difficult and affects subsequent calcium carbonate formation; therefore, centrifugation to obtain the supernatant is necessary.

[0023] Further optimization includes the following steps in step S1.2:

[0024] Step S1.2.1: Weigh an appropriate amount of urea, dissolve it in deionized water to prepare a urea solution with a concentration of 1.11 mol / L, and divide it into n portions;

[0025] Step S1.2.2: Take an appropriate amount of urease solution of each concentration and add it to the corresponding urea solution to make the urease solution and urea solution mix evenly, and ensure that the initial concentration of urea after mixing is 1 mol / L;

[0026] Step S1.2.3: At room temperature of 25℃, use a conductivity meter to measure the conductivity of the above n mixed solutions every 5 minutes, and record the change in conductivity of each mixed solution within 15 minutes;

[0027] Step S1.2.4: Calculate the average change in conductivity of each mixed solution per minute, in mS*cm-1*min-1. Based on the change in conductivity, quantify the activity of urease hydrolyzing urea per minute.

[0028] Further optimization is achieved by the following steps in step S2 for preparing the filling medium:

[0029] Step S2.1: Knead the polyvinyl alcohol fiber segments to form a clump of cotton wool;

[0030] Step S2.2: Pour the prepared reinforcement solution into the kneaded polyvinyl alcohol fiber bundle to completely wet it;

[0031] Step S2.3: Place the moistened polyvinyl alcohol fiber clumps into the red sandstone particles and stir dry. After the polyvinyl alcohol fiber clumps can no longer adhere to the red sandstone particles, remove them and place them in a container.

[0032] Step S2.3: Add the consolidation solution to the container in small amounts multiple times using a pipette, while stirring with a glass rod to obtain the filling medium.

[0033] Further optimization: In step S3, for rocks with small fissures, the prepared mud-like granular fiber filling medium is filled into the fissures using a small iron rod. After filling, granules are sprinkled on the moist surface of the fissures and the fissures are smoothed.

[0034] For rocks with large fractures, the reinforcement solution is first mixed with neutral gel to obtain a gel solution, and then reinforcement is carried out by a step-by-step filling method, that is, a layer of gel solution is sprayed after each layer of filling medium is filled.

[0035] To further optimize this step, in step S4, the rock fissures are impregnated and filled with a reinforcing solution. The specific operation is as follows:

[0036] For smaller rocks, the rocks that have had their fissures filled in step S3 are immersed in a reinforcing solution, with the solution covering the fissures.

[0037] For larger rocks, a reinforcing solution is poured into the rock fissures after step S3 and then covered with a waterproof membrane.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. Compared to bacteria, urease molecules are smaller, allowing them to infiltrate into finer rock fissures and spread more widely, potentially resulting in better reinforcement effects. Furthermore, because urease is directly exposed to the solution, it catalyzes urea production more quickly under the same conditions, which is beneficial for improving calcium carbonate production efficiency.

[0040] 2. Soybean urease is readily available and does not require prior cultivation, reducing the time and economic costs of solution preparation. On the other hand, conductivity is used to evaluate urease activity, reducing the difficulty of urease activity determination and improving solution preparation efficiency. Third, soybean urease can reinforce rocks, and the urease solution can be naturally degraded, resulting in extremely low environmental pollution and saving environmental remediation costs. Its application scope and applicable conditions are also more extensive.

[0041] 3. Based on EICP technology, the combination of filling medium as a target material promotes the formation of calcium carbonate crystals, improves the efficiency of EICP technology in reinforcing rock fractures, and expands the application prospects and scope of EICP technology in rock reinforcement. Attached Figure Description

[0042] Figure 1 This is a graph showing the change in urease activity with soybean flour concentration.

[0043] Figure 2 The graph shows the change in urease activity per unit mass with the concentration of soybean flour.

[0044] Figure 3 This is a diagram of the particle + fiber filled sample from Example 1;

[0045] Figure 4 This is a diagram showing the sample after filling, soaking, and reinforcement in Example 1;

[0046] Figure 5 This is a sample image of the ground red sandstone particles filled in Example 2;

[0047] Figure 6 This is a diagram of the polyvinyl alcohol fiber-filled sample from Example 3;

[0048] Figure 7 These are the test results of the mechanical properties of the specimens in Examples 1-4 and Comparative Examples 1-4;

[0049] Figure 8 These are original SEM (Scanning Electron Microscope) images;

[0050] Figure 9 These are SEM images of particle-reinforced samples;

[0051] Figure 10 These are SEM images of fiber-reinforced particle samples. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0053] A method for reinforcing fractured rock includes the following steps:

[0054] Step S1: Prepare a consolidation solution containing urease, carbonate ions, and calcium ions, specifically including:

[0055] Step S1.1: Prepare urease solution. Specifically, select dried soybeans and dry them in an oven at 40 ℃ for 5 hours; then weigh 800 g of the dried soybeans and put them into a high-speed blender for grinding. Do not use early-ground soybean powder or its processed products as substitutes, as plant urease will gradually become inactive. Dried soybeans help to preserve and control the content of effective ingredients for a long time. During the grinding process of soybean powder, the internal temperature of the blender will continuously rise due to friction. To ensure that the soybean powder does not become inactive due to excessive friction temperature, the following steps should be taken during the grinding process: grind for one minute, wait for it to cool to room temperature, and then grind for one minute. Repeat this process three times until no large soybean particles appear. Pass the ground soybean powder through a 100-mesh sieve to ensure dryness. Store any excess soybean powder in a low-temperature device for later use. Divide the ground soybean powder into 8 portions, add deionized water to each portion, and prepare soybean powder solutions of different concentrations, keeping the total mass of the soybean powder solutions constant, as shown in Table 1.

[0056] Table 1. Soybean flour solutions of different concentration grades

[0057]

[0058] After thoroughly mixing each portion of soybean flour solution with a magnetic stirrer, let it stand for 2-3 hours, then transfer it to a 500 mL centrifuge bottle and place it in a centrifuge (in this implementation case, a KDC-2046 low-speed refrigerated centrifuge is used). Centrifuge at 4℃ and 3000 r / min for 15 min. Then filter it with double-layer medical gauze, take the supernatant, discard the soybean residue at the bottom, and obtain 8 portions of soybean urease solution with different concentrations.

[0059] Step S1.2: Determine urease activity and screen for the urease solution with the best urease activity ratio. The soybean urease solution obtained in Step S1.1 is subjected to urease activity determination. The internationally standardized method for urease activity determination is titration. Additionally, the pH increment method is widely used by many researchers, but both methods are complex, with strict procedures and instrument requirements, making them difficult to implement for engineering applications of crude urease. The hydrolysis of urea by urease generates carbonate and ammonium ions. The generation of ions in the solution increases the solution conductivity. Higher conductivity indicates a higher concentration of ions in the solution, resulting in stronger urease hydrolysis and higher urease activity. Therefore, the amount of urea hydrolyzed per unit time can be used as an indicator of urease activity. The specific test method is as follows:

[0060] Step S1.2.1: Weigh 1.8 g of urea, dissolve it in 27 mL of deionized water to prepare a urea solution with a concentration of 1.11 mol / L, and divide it into 8 portions;

[0061] Step S1.2.2: Take 3 ml of each concentration of urease solution and add it to the corresponding urea solution to mix the urease solution and urea solution evenly, ensuring that the initial concentration of urea after mixing is 1 mol / L;

[0062] Step S1.2.3: At room temperature of 25℃, use a conductivity meter (in this implementation case, the model is Leici DDB-303A conductivity meter) to measure the conductivity of the above 8 mixed solutions every 5 minutes, and record the change in conductivity of each mixed solution within 15 minutes;

[0063] Step S1.2.4: Calculate the average change in conductivity per minute for each mixed solution, in mS*cm⁻¹*min⁻¹. The change in conductivity corresponding to 1 mS*cm⁻¹*min⁻¹ is 11.1 mM / min. Based on the change in conductivity, quantify the activity of urease in hydrolyzing urea per minute.

[0064] from Figure 1 , 2 It can be seen that, overall, urease activity increases with increasing soybean flour concentration. However, within the concentration range of 20-50 g / L, the urease activity per unit mass generally shows a decreasing trend, but there is no clear pattern and some fluctuation. The urease activity per unit mass decreases at a concentration of 40 g / L and increases slightly at 50 g / L. The urease activity per unit mass represents the extraction efficiency of soybean urease; the higher the value, the higher the soybean urease extraction efficiency per unit mass of soybean flour.

[0065] Therefore, when the soybean flour concentration is greater than 50 g / L, the urease activity still increases with increasing soybean flour concentration, but the urease activity per unit mass gradually decreases with increasing soybean flour concentration, indicating that the extraction efficiency of soybean urease decreases with increasing soybean flour concentration. Therefore, the most suitable soybean flour concentration for extracting soybean urease from the soybeans purchased in this embodiment is 50 g / L.

[0066] Step S1.3: Mix the CaCl2 solution, urea solution, and the urease solution with a soybean flour concentration of 50 g / L selected in Step S1.2 to obtain the reinforcement solution. Specifically, add CaCl2 to deionized water and stir. The completion of the EICP reinforcement process requires not only urease but also the addition of other solutions to provide carbonate and calcium ions. There are various calcium sources that can serve as substrates for calcium ions, such as CaCl2, Ca(OH)2, and Ca(NO)3. In this example, CaCl2 is selected. Because the addition of CaCl2 to water is exothermic and will affect urease activity, the solution is allowed to stand for 15 minutes before being mixed with the urease solution. In this example, a 1 mol / L CaCl2 solution is used. Then, add the above solution to the urea solution and stir to obtain the reinforcement solution. Carbonate ions are produced by the decomposition of urea. In this example, the concentration of the urea solution used is 1 mol / L.

[0067] In the reinforcement solution, the mass concentration ratio of soybean flour (with equivalent urease activity), carbonate ions, and calcium ions is 5:6:4. According to... Figure 1 , Figure 2 As shown, urease activity gradually increases with increasing soybean flour concentration, but the urease activity per unit mass of soybean gradually decreases. This means that increasing soybean flour concentration has a gradually decreasing effect on increasing urease activity. Considering both the urease activity of the experimental solution and economic efficiency, a soybean flour concentration of 50 g / L was chosen. Since the units for urease activity are not consistent with those for carbonate and calcium ion concentrations, an equivalent soybean flour concentration was used to represent urease activity. In the experiment, the effective product, calcium carbonate, consists of a calcium ion and a carbonate ion combined; therefore, both carbonate and calcium ion concentrations were set to 1 mol / L.

[0068] Step S2: Mix the reinforcing solution prepared in step S1 with the filler to obtain the filling medium. Specifically:

[0069] Step S2.1: Knead the polyvinyl alcohol fiber segments to form a clump of cotton wool;

[0070] Step S2.2: Pour the prepared reinforcement solution into the kneaded polyvinyl alcohol fiber bundle to completely wet it;

[0071] Step S2.3: Place the moistened polyvinyl alcohol fiber bundle into the red sandstone particles and stir dry to make the red sandstone particles adhere to the polyvinyl alcohol fiber bundle. After the polyvinyl alcohol fiber bundle can no longer adhere to the red sandstone particles, take it out and put it into a container.

[0072] Step S2.3: Add the consolidation solution to the container in small amounts multiple times using a pipette, while stirring with a glass rod to obtain the filling medium.

[0073] Step S3: Fill the rock fissures with a filling medium.

[0074] In this embodiment, the rock is a pre-fabricated small-volume red sandstone sample with minor cracks. The prepared mud-like granular fiber-filled medium is filled into the cracks using a small iron rod. Figure 3 As shown, after filling, sprinkle granules on the moist surface of the crack and smooth the crack.

[0075] In other embodiments, for rocks with large fractures, the consolidation solution is first mixed with a neutral gel to obtain a gel solution, and then the consolidation is carried out by a step-by-step filling method, that is, a layer of gel solution is sprayed after each layer of filling medium is filled, so as to make full use of the urease effective component in the gel solution.

[0076] Step S4: Reinforce the rock fissures by impregnating them with a reinforcing solution.

[0077] In this embodiment, the rock sample with the fractures filled in step S3 is immersed in a reinforcement solution, with the solution covering the fractures. Because most of the calcium carbonate crystals that form settle downwards under gravity, it's not possible to target and reinforce the pre-fabricated fractures. However, since the pre-fabricated fractures on the sample are located at opposite ends, placing either end upwards could cause uneven reinforcement, leading to weak surfaces and affecting the results of mechanical tests. To ensure a uniform reinforcement environment, the rock sample is placed with the main fractures positioned horizontally as much as possible.

[0078] In this embodiment, two rounds of solution stabilization were performed, each lasting 48 hours. After 24 hours of immersion in the first stabilization, numerous bubbles began to appear on the surface. These bubbles consisted of ammonia and carbon dioxide and had a pungent odor. The solution became clearer than when it was first added, and some white precipitate began to adhere to the sample surface.

[0079] After 48 hours of immersion for reinforcement, the number of bubbles in the upper part of the slurry decreased, and the bubbles became more aggregated. The slurry became clearer, a thin white precipitate appeared at the bottom of the test tank, and a lot of milky white deposits appeared on the surface of the sample. At this point, the slurry reaction was basically completed. The waste liquid in the tank was poured out, and the newly prepared solution from step four was added again, and the immersion continued for another 48 hours.

[0080] After a second round of immersion in water for 24 hours, the sample surface was covered with a white precipitate, such as... Figure 4 As shown, a large number of sugar-shell-like crystals float on the surface of the reinforced solution, and the solution is slightly more turbid than the first round of reinforcement.

[0081] After a second round of immersion for 48 hours, the sample showed little change compared to the second round of 24 hours. The white precipitate had completely coated the sample, indicating that the immersion was complete. Upon removing the sample, the solution in the immersion tank had become significantly clearer, and a groove had appeared where the sample had been placed, with a pale yellow precipitate around the groove.

[0082] In other embodiments, if the rock sample is large or in an outdoor project, a reinforcing solution is poured into the rock fissures after step S3 and covered with a waterproof membrane.

[0083] Example 2:

[0084] In this embodiment, the filler in step S2 is red sandstone particles. When preparing the filling medium, simply mix the red sandstone particles with the reinforcing solution, with a ratio of red sandstone particles:solution of 2g:1g. The filled sample is shown below. Figure 5 As shown.

[0085] The other steps are the same as in Example 1.

[0086] Example 3:

[0087] In this embodiment, the filler in step S2 is polyvinyl alcohol fiber segments. When preparing the filling medium, the filler is polyvinyl alcohol fiber segments; red sandstone particles are not added. The filled sample is as follows: Figure 6 As shown.

[0088] The other steps are the same as in Example 1.

[0089] Comparative Example 1:

[0090] In this embodiment, the sample is a pre-made, small-volume red sandstone sample without cracks, and is not soaked in a consolidation solution, i.e., it is in its original state.

[0091] Comparative Example 2:

[0092] In this embodiment, the sample is a pre-made, small-volume red sandstone sample without cracks, which is immersed in a reinforcement solution for reinforcement, i.e., the original sample is reinforced.

[0093] Comparative Example 3:

[0094] In this embodiment, the sample is a prefabricated small-volume red sandstone sample with cracks, without filling or reinforcement, i.e., a prefabricated cracked sample.

[0095] Comparative Example 4:

[0096] In this embodiment, the sample is a pre-made small-volume red sandstone sample with cracks. It is not filled, but the sample is immersed in a strengthening solution for strengthening. That is, the sample is not filled after strengthening.

[0097] The present invention does not provide a comparative example of filling the precast crack sample without soaking it in the reinforcement liquid because after filling the crack sample with the medium, the red sandstone particles adhered to the polyvinyl alcohol fiber clusters and the adsorbed reinforcement liquid alone cannot fix the filling medium to the sidewall of the crack, and therefore the corresponding mechanical property test cannot be carried out.

[0098] Performance testing:

[0099] The following performance tests were performed on the samples treated in Examples 1-3 and Comparative Examples 1-4.

[0100] 1. Uniaxial compression mechanical test, the test results are shown in Tables 2 and 3.

[0101] Table 2. Maximum values ​​of uniaxial compressive peak stress and maximum values ​​of volumetric strain

[0102]

[0103] Table 3 Uniaxial Compression Test

[0104]

[0105] 2. Triaxial compression mechanical test, the test results are shown in Table 4.

[0106] Table 4 Triaxial Compression Test

[0107]

[0108] The test cases marked with "×" in the table above are those where the specimens were destroyed before the confining pressure was applied to 15 MPa, making it impossible to obtain effective stress-strain data.

[0109] Triaxial compression testing is a rock mechanics testing method relative to uniaxial compression testing. Triaxial compression involves applying a fixed confining pressure around the specimen before conducting the compression test, while uniaxial compression has a confining pressure of 0 MPa.

[0110] As can be seen from Tables 2, 3, and 4, the strength of the reinforced specimens in the uniaxial and triaxial compression tests was significantly higher than that of the unreinforced fractured specimens, with some specimens even exceeding the original strength. The strength of the reinforced specimens essentially recovered to the original rock strength, with a slight increase in strain. During the test, the propagation of cracks along the original pre-fabricated fissures decreased, indicating that the integrity of the reinforced rock was significantly improved.

[0111] As shown in Table 3, taking the most basic peak strength as an example, the strength of the original sample increased by 23.6% after reinforcement, indicating that EICP reinforcement of rocks is feasible. The strength of the granular fiber-reinforced sample increased by 34.8% and 30.1% compared to the fiber-reinforced sample and the granular fiber-reinforced sample, respectively. Considering that polyvinyl alcohol fiber and ground red sandstone particles themselves have almost no strength, the peak strength of the sample with polyvinyl alcohol fiber as the filling medium was only 3.6% lower than that of the sample with ground red sandstone particles as the filling medium after reinforcement. This indicates that polyvinyl alcohol fiber increases the contact area with the solution during soaking, adsorbs more calcium carbonate crystals and precipitates, and plays a role in improving the strength of the reinforced rock sample based on the fiber-calcium carbonate precipitate.

[0112] SEM analysis:

[0113] Figure 8 This is a scanned image of the original specimen using SEM (electron microscopy). Figure 9 Images of particle-reinforced samples obtained by SEM (electron microscopy). Figure 10 Images of the fiber-reinforced particle sample obtained by SEM (electron microscopy). Figure 8 (a), 9(a) and 10(a) are S4800, 15.0KV, 18.6x100SE(M); Figure 8 (b), 9(b), and 10(b) represent S4800, 15.0 kV, and 18.6 x 500 SE (M). The particle-reinforced samples show calcium carbonate crystals forming and adhering to the rock fracture surface, while the particle-fiber-reinforced samples demonstrate the combined effect between fibers and particles, filling small cracks while increasing the contact surface area between the solution and the rock, guiding the effective components in the solution to be generated deep within the fractures.

[0114] In summary, the urease-induced calcium carbonate precipitation (EICP) technology described in this invention utilizes CaCl2 solution to provide calcium ions and urea solution to provide carbonate ions. Urease extracted from soybeans is used as a catalyst to promote urea decomposition. The carbonate ions generated from urea decomposition combine with calcium ions to produce calcium carbonate crystals with a reinforcing effect. By using a combined filling medium, calcium carbonate crystals are more fully formed at the filling fractures. Polyvinyl alcohol fiber segments increase the contact surface area between the rock and the calcium carbonate solution, making it easier for calcium carbonate crystals to adhere to the fracture surface. Compared to traditional cement grouting methods for reinforcing rock masses, the method described in this invention has less environmental pollution, and the solution has good fluidity and permeability, easily penetrating narrow fractures. Compared to existing microbial reinforcement technologies such as bacterial-induced calcium carbonate precipitation (MICP), this method has advantages such as low solution production cost, simple preparation, and simple rock reinforcement conditions, significantly improving both economic efficiency and time cost. Compared with the urease-induced calcium carbonate precipitation technology described in the existing paper "He Jia, Qu Siyuan, Hang Lei, et al. Experimental study on sand reinforcement by bio-enzyme-assisted magnesium oxide carbonization process [J / OL]. Journal of Civil and Environmental Engineering, 1-8 [2023-12-28]", this invention has significant improvements in reinforcement efficiency and economic cost.

[0115] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An EICP-based fractured rock reinforcement filling medium, characterized in that, This includes the reinforcing solution and the filler mixed with the reinforcing solution; The reinforcement solution contains urease, carbonate ions, and calcium ions; The filler is a mixture of red sandstone particles and polyvinyl alcohol fiber segments; The mass ratio of the solid solution to the filler is: polyvinyl alcohol fiber segments: sandstone particles: reinforcement solution = 1:3:3; In the reinforcement solution, the mass concentration ratio of soybean flour, carbonate ions, and calcium ions is 5:6:

4.

2. A method for reinforcing fractured rock, characterized in that, The fractured rock reinforcement and filling medium based on EICP as described in claim 1 includes the following steps: Step S1: Prepare a consolidation solution containing urease, carbonate ions, and calcium ions, specifically including: Step S1.1: Prepare urease solution, specifically: divide freshly ground soybean flour into n portions, add deionized water to each portion, prepare soybean flour solutions of different concentrations, keep the total mass of soybean flour solutions constant, stir all soybean flour solutions and centrifuge, take the supernatant and filter it through medical gauze to obtain urease solutions of different concentrations. Step S1.2: Determine urease activity and screen out the urease solution with the best urease activity ratio; Step S1.3: Mix the CaCl2 solution, urea solution and the optimal ratio of urease solution selected in step S1.2 to obtain the reinforcement solution; Step S2: Mix the reinforcing solution prepared in step S1 with the filler to obtain the filling medium; Step S3: Fill the rock fissures with a filling medium; Step S4: Reinforce the rock fissures by impregnating them with a reinforcing solution.

3. The method for reinforcing fractured rock according to claim 2, characterized in that, Step S1.2 specifically includes the following steps: Step S1.2.1: Weigh an appropriate amount of urea, dissolve it in deionized water to prepare a urea solution with a concentration of 1.11 mol / L, and divide it into n portions; Step S1.2.2: Take an appropriate amount of urease solution of each concentration and add it to the corresponding urea solution to make the urease solution and urea solution mix evenly, and ensure that the initial concentration of urea after mixing is 1 mol / L; Step S1.2.3: At room temperature of 25℃, use a conductivity meter to measure the conductivity of the above n mixed solutions every 5 minutes, and record the change in conductivity of each mixed solution within 15 minutes; Step S1.2.4: Calculate the average change in conductivity per minute for each mixed solution, and quantify the activity of urease hydrolyzing urea per minute based on the change in conductivity.

4. The method for reinforcing fractured rock according to claim 3, characterized in that, In step S2, the specific steps for preparing the filling medium are as follows: Step S2.1: Knead the polyvinyl alcohol fiber segments to form a clump of cotton wool; Step S2.2: Pour the prepared reinforcement solution into the kneaded polyvinyl alcohol fiber bundle to completely wet it; Step S2.3: Place the moistened polyvinyl alcohol fiber clumps into the red sandstone particles and stir dry. After the polyvinyl alcohol fiber clumps can no longer adhere to the red sandstone particles, remove them and place them in a container. Step S2.3: Add the consolidation solution to the container in small amounts multiple times using a pipette, while stirring with a glass rod to obtain the filling medium.

5. The method for reinforcing fractured rock according to claim 4, characterized in that, In step S3, for rocks with small fissures, the prepared mud-like granular fiber filling medium is filled into the fissures. After filling, granules are sprinkled on the wet surface of the fissures and the fissures are smoothed. For rocks with large fractures, the reinforcement solution is first mixed with neutral gel to obtain a gel solution, and then reinforcement is carried out by a step-by-step filling method, that is, a layer of gel solution is sprayed after each layer of filling medium is filled.

6. The method for reinforcing fractured rock according to claim 5, characterized in that, In step S4, the rock fissures are filled with a reinforcing solution, and the specific operation is as follows: For smaller rocks, the rocks that have had their fissures filled in step S3 are immersed in a reinforcing solution, with the solution covering the fissures. For larger rocks, a reinforcing solution is poured into the rock fissures after step S3 and then covered with a waterproof membrane.

Images