Method for making a w-shaped liquid collecting structure at the bottom of a rare earth ore mining pit based on biotechnology

Abstract

The application provides a rare earth ore stope bottom W-shaped liquid collecting structure manufacturing method based on biotechnology, and relates to the field of ion type rare earth ore in-situ leaching liquid collecting technology. The method first arranges double-layer liquid injection holes staggeredly distributed at the stope bottom; then arranges a bacteria liquid pool, a cementing liquid pool and a clean water pool, and the three solution pools are connected to the input end of the liquid injection pipe through the liquid delivery pipe; after the bacteria liquid and the cementing liquid are prepared, the lower layer liquid injection is first performed, and then the upper layer liquid injection is performed, the injected bacteria liquid contacts the cementing liquid to form calcium carbonate precipitation; in the layered liquid injection process, the solution injected in the upper layer contacts the solution existing in the lower layer to occur mineralization reaction again, and finally the liquid collecting layer with continuous concave-convex structure is formed; after the liquid collecting layer is consolidated, the liquid collecting flow guide hole and the liquid collecting roadway are arranged above the liquid collecting layer. The structure can intercept and recover the rare earth mother liquor to the liquid collecting pool, and has important significance for improving the rare earth mother liquor recovery rate and reducing the surrounding environmental pollution.

Description

Technical Field

[0001] This invention relates to the field of in-situ leaching and liquid collection technology for ion-adsorption rare earth minerals, and in particular to a method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology. Background Technology

[0002] Ion-adsorption rare earth elements, as strategically important mineral resources, have been widely applied in high-tech fields due to their unique properties, becoming an indispensable component in important sectors such as new energy vehicles, artificial intelligence, aerospace, and national defense. In recent decades, the mining technology of ion-adsorption rare earth deposits in my country has continuously developed towards green and efficient methods, evolving from the initial pond leaching and heap leaching to today's in-situ leaching process. In-situ leaching offers advantages such as low production costs and no damage to the surface ecological environment, and has been widely applied in the mining of ion-adsorption rare earth deposits in southern my country.

[0003] In-situ leaching involves injecting leaching solution into the ore body at a suitable location on a hilltop with minimal disruption to the surface environment and without excavating topsoil or the ore body. The rare earth mother liquor is then recovered through a collection system at the bottom of the stope or at the foot of the mine. However, in most ion-adsorption rare earth mines, the bedrock at the bottom is deeply buried, making it difficult to prevent the mother liquor from seeping deeper during the collection process at the bottom of the stope. This leads to the loss of valuable resources and pollution of surrounding soil and groundwater. Investigations have revealed that the rare earth element content in groundwater and surface water around rare earth mining areas is far higher than in non-mining areas, resulting in significant resource waste and severe soil acidification near ion-adsorption rare earth mines. Therefore, when the bedrock is not exposed at the surface, it is urgent to research new methods to improve the structure and properties of the soil at the bottom of the stope to increase the recovery rate of the rare earth mother liquor, prevent leaching solution leakage, control the diffusion of leaching solution into the surrounding environment at its source, and reduce pollution.

[0004] Microbial induced calcium carbonate precipitation (MICP) is a novel technique that combines microbial metabolism and chemical reactions to reinforce soil and rock materials. Bacillus pasteurellii, one of the most potent urease-producing bacteria known, has been successfully applied to the consolidation of sandy soils, clays, and silts. MICP reinforcement technology based on urea hydrolysis utilizes urease produced by Bacillus pasteurellii to decompose urea into CO3. 2- and NH4 + CO3 2- and Ca adsorbed on the cell surface 2+The calcium carbonate precipitate, formed by the combination of bacteria and enzymes, fills the pores of the soil and bridges adjacent soil particles, improving the stability and impermeability of the soil. For example, Chinese patent application CN 116769681A discloses a method for consolidating desert aeolian sand using a mixture of bacteria and enzymes. This method uses *Bacillus pasteurellii* and *Bacillus mucilaginosus*, along with urease, to successfully obtain consolidated sand columns. These columns contain a large amount of calcium carbonate, significantly reducing the permeability coefficient and increasing the strength of the sand. MICP technology has achieved significant results in soil and rock reinforcement, slope protection, and the fixation of hazardous metals. However, there are no reports of its application in creating W-shaped liquid-collecting structures at the bottom of rare earth mines. Summary of the Invention

[0005] To address the challenges of low mother liquor recovery and leachate leakage polluting the surrounding environment in in-situ leaching processes for ion-adsorption rare earth ores, this invention provides a biotechnology-based method for constructing a W-shaped liquid collection structure at the bottom of a rare earth mine stope. This method employs staggered double-layer injection holes for stratified injection. First, the lower layer is injected, followed by the upper layer, sequentially injecting bacterial solution, cementing solution, and water into the soil at the bottom of the stope. Urease produced by *Bacillus pasteurellii* is used to decompose urea to obtain CO3. 2- CO3 2- With Ca in the cementing solution 2+ Calcium carbonate precipitates are formed through the combination of various methods. This precipitate adheres to and grows on the surface of soil particles, filling soil pores, enhancing interparticle cohesion, and reducing soil permeability. The bacterial solution injected into the same layer contacts the cementing solution to form calcium carbonate. During layered injection, the solution injected from the upper layer contacts the solution present in the lower layer, undergoing another mineralization reaction to form calcium carbonate. Through a method of staggered double-layer injection holes and layered injection, a liquid-collecting layer with a continuous concave-convex structure is formed. After the liquid-collecting layer is solidified, guide holes and collection tunnels are arranged in the concave areas on the upper surface of the liquid-collecting layer. The W-shaped liquid-collecting structure facilitates the accumulation of rare earth mother liquor in the concave areas, and the guide holes and collection tunnels then recover the mother liquor to the collection pool. The liquid-collecting structure created by this method effectively prevents the leaching solution from leaking into the surrounding area of ​​the mining area, which is of great significance for improving the mother liquor recovery rate and reducing environmental pollution. The technical solution is as follows:

[0006] A method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology, the method comprising:

[0007] S1. Arrange the injection pipe:

[0008] Drilling rigs are used to construct injection holes at the bottom of the mining area. The injection holes are arranged in two layers in a W-shape. The opening of the lower layer injection hole is 0.5-1.5m above the ground. The output end of the injection pipe is inserted into the injection hole. The injection pipes in the same layer are arranged in parallel. After the injection pipes are arranged, the opening of the injection hole is sealed to provide a sealed environment for subsequent pressurized injection.

[0009] S2. Arrange the solution tank:

[0010] A solution tank is arranged at a distance of 30-100m from the injection hole. The solution tank includes a bacterial solution tank, a cementing solution tank, and a clear water tank. The solution tank is connected to the injection pipe through an infusion pipe.

[0011] S3. Inject liquid:

[0012] A layered injection method is used to sequentially inject bacterial solution, cementing solution, and clean water into the soil at the bottom of the mining area under pressure, forming a W-shaped liquid-collecting layer with a continuous concave-convex structure.

[0013] S4. Arrange diversion holes and liquid collection tunnels:

[0014] After the liquid collection layer is solidified, liquid collection guide holes and liquid collection tunnels are arranged in the recessed area on the upper surface of the liquid collection layer, with an interval of 30-40m between two adjacent liquid collection tunnels.

[0015] An infusion switch and a flow meter are installed on the infusion tube. The upper or lower infusion tube switch is opened in time according to the infusion needs to deliver the solution to the infusion tube.

[0016] The injection pipe is equipped with an injection switch, a flow meter, and a pressure booster. During the injection process, the upper or lower injection pipe switch is opened according to the injection requirements. The pressure booster applies sufficient pressure to the solution in the injection pipe to ensure the smooth progress of the injection process.

[0017] Preferably, the same layer of injection pipes is connected to the same infusion pipe, which has three inlets and multiple outlets. The three inlets are respectively located in the bacterial culture tank, the cementing solution tank, and the clear water tank, and the outlets of the infusion pipe are connected to the injection pipes. Each inlet is equipped with a switch and a flow indicator. During the injection process, the corresponding switch is activated according to the injection requirements to deliver the required solution, while the flow indicator displays the total flow rate and the daily flow rate of the infusion pipe in real time.

[0018] The layered injection in step S3 includes lower layer injection and upper layer injection. First, the lower layer injection is performed: the lower infusion pipe and injection pipe switches of the bacterial solution tank are opened, and bacterial solution that has been stored for 24-48 hours is injected under pressure. The pressure is applied to the bacterial solution in the injection pipe using a pressure booster on the injection pipe. After the bacterial solution injection is complete, after an interval of 4-6 hours, the lower infusion pipe switch of the clear water tank is opened, and clear water is injected for 1 hour to flush the infusion pipe and injection pipe. After the clear water injection is complete, after an interval of 1 hour, the lower infusion pipe switch of the cementing solution tank is opened, and cementing solution that has been stored for 24-48 hours is injected under pressure. After the cementing solution injection is complete, clear water is injected for another 1 hour to flush the infusion pipe and injection pipe. After the clear water injection is complete, the lower infusion pipe and injection pipe switches are closed.

[0019] Then proceed with the upper layer injection: Open the upper infusion pipe switch and the injection pipe switch of the cementing solution tank, and inject the cementing solution for 24-48 hours under pressure. After the cementing solution injection is completed, inject clean water for 1 hour after an interval of 4-6 hours. After the clean water injection is completed, open the upper infusion pipe switch of the bacterial solution tank again after an interval of 1 hour, and inject the bacterial solution for 24-48 hours under pressure. After an interval of 72 hours, inject clean water for 1 hour to clean the pipes.

[0020] The injection process is repeated until the liquid collection layer is solidified, at which point the injection operation is stopped and all infusion switches and injection switches are turned off.

[0021] The bacterial solution is a Bacillus pasteurellii bacterial solution with a concentration of OD0.05. 600 =0.6~1.

[0022] The cementing solution is a 1:1 molar mixture of urea and calcium chloride, with the concentrations of calcium chloride and urea being 0.5–1.5 mol / L.

[0023] During the injection process, bacterial solution and cementing solution are injected into the upper and lower injection holes once each in one cycle, and the entire injection process is carried out in 3 to 5 cycles.

[0024] The injection holes are arranged at an upward inclination of 3-8° along the horizontal plane, with a diameter of 10-15 cm. The lower layer of injection holes is 0.5-1.5 m above the ground. The vertical interval between the upper and lower layers of injection holes is 0.8-1.5 m. The horizontal interval between two adjacent injection holes in the same layer is 3-4 m, and the horizontal spacing between the injection holes is equal.

[0025] The guide holes and collection tunnels are arranged in the recessed area on the upper surface of the liquid collection layer. The guide holes are arranged at an angle of 3 to 8 degrees upward along the horizontal plane, with a diameter of 10 to 15 cm. The height of the collection tunnel is 1 to 1.4 m and the width is 0.8 to 1 m.

[0026] Two bacterial solution tanks and two cementing solution tanks are arranged, one clear water tank is arranged, and another solution tank is arranged as a spare tank. Each solution tank is 5m deep and 10m long and wide.

[0027] The solution is injected using a staggered double-layer injection hole and a layered injection method. The bacterial solution injected in the same layer comes into contact with the cementing liquid to form calcium carbonate precipitate. During the layered injection process, the solution injected in the upper layer comes into contact with the solution in the lower layer and undergoes a mineralization reaction, consolidating to form a W-shaped liquid collection layer with a continuous concave-convex structure.

[0028] After the liquid-collecting layer has solidified, guide holes and collection tunnels are arranged in the recessed areas on the upper surface of the liquid-collecting layer. It is particularly important to note that there are continuous recessed areas in the W-shaped liquid-collecting structure. Rare earth mother liquor seeps down from above, and the guiding effect of the liquid-collecting structure promotes the accumulation of rare earth mother liquor in the recessed areas. Then, the guide holes and collection tunnels are used to recover the rare earth mother liquor into the collection pool.

[0029] In this method, as the injection process proceeds, calcium carbonate gradually fills the pores of the particles to form a liquid-collecting layer. As the main component of the W-shaped liquid-collecting structure, the high stability and impermeability of the liquid-collecting layer effectively prevent the leakage of rare earth mother liquor.

[0030] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0031] In the above scheme, a staggered double-layer injection hole and layered injection method are used to inject bacterial solution and cementing solution into the soil at the bottom of the stope. Microbial-induced calcium carbonate precipitation fills the soil pores, reduces the soil permeability coefficient, and consolidates to form a liquid-collecting layer with a continuous concave-convex structure. The liquid-collecting layer consolidated by biotechnology is an important component of the W-shaped liquid-collecting structure at the bottom of the rare earth mine stope. In the process of ion-adsorption rare earth mining, the W-shaped liquid-collecting structure can effectively intercept and recover rare earth mother liquor, effectively preventing the rare earth mother liquor from seeping into the surrounding area of ​​the stope. It is worth mentioning that the microorganisms used in this invention are derived from nature, the remaining urea can be used as nutrients for surrounding plants, and the MIP treatment process hardly changes the soil pH, resulting in minimal environmental impact. After the liquid-collecting layer is consolidated, diversion holes and liquid collection tunnels are arranged in the concave areas on the upper surface of the liquid-collecting layer. Compared to traditional technologies, the method of using biotechnology to create ionic rare earth liquid collection structures is simple to operate, environmentally friendly and low-carbon, and can save significant costs. After mining, there is no need for recovery or reclamation; calcium carbonate can be used to reinforce the mountainside and is more easily decomposed, solving the problem of the difficulty in reclamation when using cementitious materials to create liquid collection layers. The W-shaped liquid collection structure at the bottom of the rare earth mine based on biotechnology can effectively intercept and recover rare earth mother liquor, improving the recovery rate while simultaneously preventing soil acidification, groundwater pollution, and rare earth resource loss caused by leaching solution leakage and heavy metal ion migration. This technology solves the problems of low mother liquor recovery rate, severe environmental pollution, and difficulty in reclamation of liquid collection projects in traditional processes. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 These are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) images of the internal structure of the soil before MICP treatment in this embodiment of the invention.

[0034] Figure 2 These are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) images of the internal structure of soil after MICP treatment in this embodiment of the invention.

[0035] Figure 3 The following are examples of the effects of different MIP treatment methods on the permeability coefficient of the liquid receiving layer in the embodiments of the present invention, wherein (a) is the treatment with different cementing liquid concentrations, and (b) is the treatment with different ratios of bacterial solution to cementing liquid injection times.

[0036] Figure 4 This invention illustrates the effect of different MIP treatment methods on the calcium carbonate content of the liquid receiving layer in various embodiments.

[0037] Figure 5 This is a cross-sectional view showing the layout of the W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology, according to the present invention.

[0038] Figure 6 This is a front view of the distribution of injection holes in an embodiment of the present invention;

[0039] Figure 7 This is a flowchart illustrating the fabrication of the W-shaped liquid-collecting structure in an embodiment of the present invention.

[0040] Wherein: 1-Topsoil; 2-Ore body; 3-Upper injection pipe; 4-Lower injection pipe; 5-Unmineralized soil; 6-Booster; 7-Injection switch; 8-Flow indicator; 9-Lower delivery pipe; 10-Upper delivery pipe; 11-Delivery switch; 12-Solution pool; 13-Cementing liquid; 14-Bacterial liquid; 15-Upper injection hole; 16-Lower injection hole; 17-Guide hole; 18-Collection tunnel; 19-Collection layer; 20-Unconsolidated layer. Detailed Implementation

[0041] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0042] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0043] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0044] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0045] This invention provides a method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology.

[0046] The method includes:

[0047] S1. Arrange the injection pipe:

[0048] Drilling rigs are used to construct injection holes at the bottom of the mining area. The injection holes are arranged in two layers in a W-shape. The opening of the lower layer injection hole is 0.5-1.5m above the ground. The output end of the injection pipe is inserted into the injection hole. The injection pipes in the same layer are arranged in parallel. After the injection pipes are arranged, the opening of the injection hole is sealed to provide a sealed environment for subsequent pressurized injection.

[0049] S2. Arrange the solution tank:

[0050] A solution tank is arranged at a distance of 30-100m from the injection hole. The solution tank includes a bacterial solution tank, a cementing solution tank, and a clear water tank. The solution tank is connected to the injection pipe through an infusion pipe.

[0051] S3. Inject liquid:

[0052] A layered injection method is used to sequentially inject bacterial solution, cementing solution, and clean water into the soil at the bottom of the mining area under pressure, forming a W-shaped liquid-collecting layer with a continuous concave-convex structure.

[0053] S4. Arrange diversion holes and liquid collection tunnels:

[0054] After the liquid collection layer is solidified, liquid collection guide holes and liquid collection tunnels are arranged in the recessed area on the upper surface of the liquid collection layer, with a 30m interval between two adjacent liquid collection tunnels.

[0055] The layered injection in step S3 includes lower layer injection and upper layer injection. First, the lower layer injection is performed: the lower infusion pipe switch of the bacterial solution tank is opened to deliver the bacterial solution to the injection pipe, and the injection pipe switch is opened to pressurize and inject the bacterial solution that has been stored for 24–48 hours. After the bacterial solution is injected, after a certain interval, the lower infusion pipe switch of the clear water tank is opened, and clear water is injected for 1 hour to flush the infusion pipe and injection pipe. Subsequently, the lower infusion pipe switch of the cementing solution tank is opened, and cementing solution that has been stored for 24–48 hours is injected under pressure. After the cementing solution injection is completed, clear water is injected again for 1 hour to flush the lower infusion pipe and lower injection pipe. After the clear water injection is completed, the lower infusion pipe switch and injection pipe switch are closed.

[0056] Then proceed with the upper layer injection: Open the upper infusion pipe switch and the injection pipe switch of the cementing solution tank, pressurize and inject cementing solution for 24-48 hours, and after the cementing solution is injected, after a certain interval, inject clean water for 1 hour; then, open the upper infusion pipe switch of the bacterial solution tank, pressurize and inject bacterial solution for 24-48 hours, and then inject clean water for 1 hour to clean the pipes.

[0057] The injection process is repeated until the liquid collection layer is solidified, at which point the injection operation is stopped and all infusion switches and injection switches are turned off.

[0058] The specific implementation process will be explained below.

[0059] The culture medium used in the embodiments of the present invention includes: tryptone, soybean peptone, NaCl, and urea. The culture medium and related materials used in the injection process, such as injection tubes and flow meters, are all conventional commercially available products. The Bacillus pasteurellii used was purchased from the Beijing Biological Culture Collection Center. The injection tubes and infusion tubes used are all made of PVC material.

[0060] The CASO liquid culture medium used to culture Bacillus pasteurellis consisted of 15 g / L tryptone, 5 g / L soybean peptone, 5 g / L sodium chloride, and deionized water. The pH of the medium was adjusted to approximately 7.3 using 1 mol / L NaOH and 1 mol / L HCl, and then sterilized at 121°C for 30 min. After high-temperature sterilization, 20 g / L urea solution was added to the medium using a filter needle.

[0061] The permeability coefficient of the soil sample was measured using the constant head method, and the permeability coefficient was calculated as follows:

[0062]

[0063] Where k is the permeability coefficient, and Q is the volume of water flowing through the soil per unit time (m³). 3 l is the height of the soil sample (m); A is the cross-sectional area of ​​the soil sample (m²). 2 ); Δh is the head difference (m).

[0064] The calcium carbonate content in the soil after MIP treatment was measured using the acid washing and weighing method. The calcium carbonate content was calculated as follows:

[0065]

[0066] Where C represents the calcium carbonate content (%), m a1 The dried mass (g) of the liquid layer before pickling; m a2 G0 represents the dried mass (g) of the liquid layer after acid washing; G0 represents the calcium carbonate content (%) in the soil that has not undergone MIP treatment.

[0067] The pore volume Vv was calculated from the soil porosity and soil volume measured by the NM-600 nuclear magnetic resonance scanning equipment.

[0068] Example 1: Effect of different cementitious solution concentrations on the preparation of ion-adsorption rare earth liquid collection layers

[0069] S1. Cultivate a bacterial suspension containing Bacillus pasteurellii, prepare a cementing solution, air-dry, crush, and sieve the collected soil sample to remove impurities such as grass roots and debris. Using a sterilized stainless steel spoon, fill the soil sample into a mold in two batches, let it stand for 12 hours, then saturate it with deionized water. Measure the initial permeability and porosity of the soil sample. Specifically, the concentration of the bacterial suspension is OD0. 600=0.7, the cementing solution is a mixture of calcium chloride and urea with equimolar concentrations, the concentrations of calcium chloride and urea being 0.5–1.5 mol / L, and the density of each soil sample is controlled to be 1.55 g / cm³. 3 The total mass of the soil was 77.87g, and the porosity was 35.01%.

[0070] S2. First, inject a 2Vv (pore volume) stable bacterial solution. The injection port is inside the soil, 5mm away from the upper surface. After injecting the bacterial solution, the soil sample is left to stand at room temperature for 6 hours to allow the bacterial solution to be evenly distributed in the soil. The second step is to inject a 1-1.5Vv cementing solution to ensure that the MICP reaction takes place in the soil.

[0071] S3. Repeat the above injection steps, injecting bacterial solution and cementing solution, and circulate the injection for 1 to 3 cycles. After each injection cycle, measure the permeability coefficient and porosity of the soil.

[0072] S4. After the injection is completed, the solidified soil sample is repeatedly rinsed with deionized water. The solidified soil sample is left to stand for 3 days, then placed in an oven at 75℃ to dry for 1 day. Finally, the mold is removed to obtain a complete liquid collection layer, and the average calcium carbonate content in the liquid collection layer is measured.

[0073] After the bacterial solution was injected, Bacillus pasteurellii adsorbed onto the surface of the rare earth particles. After the cementing solution was injected, Ca... 2+ Adsorbed on the surface of bacteria and reacting with CO3 2- Calcium carbonate precipitates form and adhere to the surface of soil particles. As the calcium carbonate continues to grow, it fills the pores of the particles, bridging them together. The microstructure and elemental composition of soil samples before and after MICP treatment are shown below. Figure 1 and Figure 2 As shown; where Figure 1 These are the scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra before processing. Figure 2 The images show the processed SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) images. The SEM results reveal the initial shape of the soil, primarily consisting of irregular flaky and blocky particles. After MICP treatment, a large amount of white precipitate appeared on the soil surface. This precipitate not only filled the gaps between surface soil particles but also encapsulated the particles, forming a hardened calcium carbonate crust. Figure 2 Numerous calcite-shaped calcium carbonate precipitates were observed on the surface and pores of rare earth particles. These calcite particles grew and stacked to form aggregates that blocked the soil pores, and the Ca content increased significantly, proving that the newly formed calcite is calcium carbonate. The changes in the soil sample permeability coefficient are shown in the figure below. Figure 3 As shown in a.

[0074] This invention utilizes the characteristics of MIP (Microbial Infiltration and Propagation) technology, introducing Bacillus pasteurellii, urea, and a calcium source to induce microbial-induced calcium carbonate precipitation, thereby blocking soil pores and successfully reducing the soil's permeability coefficient. As demonstrated in Example 1, the liquid-absorbing layer prepared using the method of this invention exhibits good stability and seepage prevention. Figure 3 As can be seen, with the increase of the injection cycle, the permeability coefficients of the three soil samples (B1-B3 with cementitious solution concentrations of 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L, respectively) decreased significantly. The decrease in permeability coefficient was more pronounced when the cementitious solution concentration increased from 0.5 mol / L to 1.5 mol / L, with the permeability coefficient decreasing from 1.45 × 10⁻⁶ to 1.5 × 10⁻⁶. -5 m / s decreased to 1.27 × 10 -6 m / s, 9.82×10 -8 With speeds of m / s and 0 m / s, the seepage reduction rate reached over 92%. Figure 4 It can be seen that the calcium carbonate content of the three soil samples (B1-B3) after MIP treatment is between 3.54% and 9.84%.

[0075] Following the above-mentioned method for preparing ionic rare earth liquid-absorbing layers based on biotechnology, the filling effect of calcium carbonate in the pores inside the soil was investigated. After each injection cycle, the soil was saturated and its porosity was measured. After MICP treatment, the porosity of the soil sample was reduced to below 29.97%. Except for a small amount of calcium carbonate adsorbed on the soil surface, a large amount of calcium carbonate filled the soil pores.

[0076] Example 2: Effect of different ratios of bacterial solution and cementing solution injection times on the preparation of ion-adsorption rare earth liquid collection layer

[0077] S1. Cultivate a bacterial suspension containing Bacillus pasteurellii, prepare a cementing solution, air-dry, crush, and sieve the collected soil sample to remove impurities such as grass roots and debris. Using a sterilized stainless steel spoon, layer the soil sample into a mold, let it stand for 12 hours, then saturate it with deionized water, and measure the initial permeability and porosity of the soil sample. Specifically, the concentration of the bacterial suspension is OD0. 600 =0.6, the concentration of calcium chloride and urea in the cementing solution is 1.0 mol / L, and the density of each soil sample is controlled at 1.55 g / cm³. 3 The total mass of the soil was 77.87g, and the porosity was 35.01%.

[0078] S2. First, inject 2Vv of stable bacterial solution. The injection port is located in the soil, 5mm away from the top surface. After injecting the bacterial solution, the soil sample is left to stand at room temperature for 6 hours to allow the bacterial solution to be evenly distributed in the soil. Second, inject 1-1.5Vv of cementing solution. Within one cycle, three groups of soil samples (the ratio of bacterial solution to cementing solution injection times for C1-C3 is 1:1, 1:2, and 1:3, respectively, and the cementing solution concentration is 1mol / L) are injected with cementing solution 1, 2, and 3 times respectively. After each cementing solution injection, the second and third cementing solutions are injected 24 hours apart to ensure that the MICP reaction takes place in the soil.

[0079] S3. Repeat the above injection steps. One injection of bacterial solution and several injections of cementing solution is counted as one cycle. Circulate the injection for 1 to 3 cycles. After each injection cycle, measure the permeability coefficient and porosity of the soil.

[0080] S4. After the injection is completed, rinse the solidified soil sample repeatedly with deionized water, let the solidified soil sample stand for 3 days, then dry it in an oven at 75℃ for 1 day, and finally remove the mold to obtain the complete liquid collection layer. Measure the average calcium carbonate content of the liquid collection layer.

[0081] The change in soil permeability coefficient during consolidation is as follows: Figure 3 As shown in Figure b, this invention utilizes the characteristics of MICP technology by introducing Bacillus pasteurellii, urea, and a calcium source. Bacillus pasteurellii induces the formation of calcium carbonate to block the pores of the particles, successfully reducing the permeability coefficient of the soil sample. Example 2 demonstrates that the method proposed in this invention produces a calcium carbonate and rare earth composite liquid-absorbing layer with good stable seepage prevention effect. Figure 3 As can be seen from b, the permeability coefficient decreases significantly with the increase of the injection cycle. The greater the decrease in permeability coefficient, the more the ratio of the number of injections of bacterial solution to cementing solution decreases from 1:1 to 1:3. The three soil samples (C1-C3) showed a decrease in permeability coefficient from 1.45 × 10⁻⁶ to 1.45 × 10⁻⁶. -5 m / s decreased to 1.16 × 10 -6 m / s, 9.82×10 -8 With speeds of m / s and 0 m / s, the seepage reduction rate can reach up to 100%. Figure 4 It can be seen that the overall calcium carbonate content in the three soil samples (C1-C3) after MIP treatment ranged from 4.38% to 9.84%.

[0082] Following the above-mentioned method for preparing ionic rare earth liquid-absorbing layers based on biotechnology, the filling effect of calcium carbonate in the pores inside the soil was investigated. After each injection cycle, the porosity was measured by saturation treatment. After MICP treatment, the porosity of the soil sample was reduced to below 31.16%.

[0083] Example 3

[0084] like Figure 5As shown, this embodiment targets surface mines, constructing an in-situ leaching bottom liquid-collecting structure. The mine surface consists of topsoil 1, the interior is the ore body 2, and the bottom is non-ore soil 5. The consolidation and seepage prevention method employs layered injection. Through equipment such as infusion pipes, boosters, and injection pipes, bacterial solution, cementing solution, and clean water are injected under pressure into the soil at the bottom of the ion-adsorption rare earth mine at predetermined intervals. After the solution is injected, microorganisms adsorbed on the surface of soil particles induce the formation of calcium carbonate precipitate. The calcium carbonate adheres to and grows on the surface of the soil particles, thereby consolidating the soil at the bottom of the mine to form a liquid-collecting layer.

[0085] The specific implementation process is as follows:

[0086] First, based on the distribution characteristics and geological conditions of the ore body, double-layer injection holes were excavated using a kilometer-deep drill at a height of 0.5m above ground level around the foot of the mountain in an area without ore soil (section 5). The upper injection hole 15 and the lower injection hole 16 are distributed in a W-shape, as shown below. Figure 6 As shown. Next, solution tanks 12 (including bacterial solution tank, cementing solution tank, and clear water tank) are arranged at a distance of 10 to 80 meters from the injection port. The output end of the upper infusion tube 10 is connected to the input end of the upper injection tube 3, and the output end of the lower infusion tube 9 is connected to the input end of the lower injection tube 4. The three input ends of the infusion tubes are respectively immersed in the bacterial solution tank, cementing solution tank, and clear water tank. An infusion switch 11 and a flow indicator 8 are installed on the infusion tubes. According to the infusion needs, the upper or lower infusion tube switch is opened in time to deliver the solution to the injection tube. The length of the injection pipes is arranged according to the depth of the injection holes. The input ends of all injection pipes on the same layer are connected to the output end of the same infusion pipe, and the output ends of all injection pipes extend into the injection holes. Multiple injection pipes on the same layer are distributed in parallel. Injection switches 7, flow meters, and pressure boosters 6 are installed on the injection pipes. During the injection process, the injection pipe switches of the upper or lower layer are opened according to the injection requirements. The pressure booster applies sufficient pressure to the solution in the injection pipe to ensure the smooth progress of the injection process. After the injection pipes are arranged, the openings of the injection holes are sealed to provide a sealed environment for subsequent pressurized injection.

[0087] A stratified injection method was adopted, using infusion pipes, injection pipes, and a pressurizer to sequentially inject bacterial solution 14, cementing solution 13, and clean water under pressure into the soil at the bottom of the mining area. The stratified injection process mainly consists of lower-layer injection and upper-layer injection. For example... Figure 7As shown, the lower layer injection is performed first: the lower infusion pipe switch of the bacterial solution tank is opened to deliver bacterial solution 14 to the injection pipe. The injection pipe switch is then opened, and 24 hours of bacterial solution is injected under pressure. Pressure is applied to the bacterial solution in the injection pipe using a booster on the injection pipe. After the bacterial solution injection is completed, the lower infusion pipe switch of the clear water tank is opened after a certain interval, and clear water is injected for 1 hour to flush the infusion pipe and injection pipe. Subsequently, at specific time intervals, the lower infusion pipe switch of the cementing solution tank is opened, and 24 hours of cementing solution 13 is injected under pressure. After the cementing solution injection is completed, clear water is injected for another 1 hour to flush the lower infusion pipe and lower injection pipe. After flushing, the lower infusion pipe switch and injection pipe switch are closed. The upper layer injection is then performed: the upper infusion pipe switch and injection pipe switch of the cementing solution tank are opened, and 24 hours of cementing solution is injected under pressure. After the cementing solution injection is completed, clear water is injected for another 1 hour after a certain interval. Then, at predetermined time intervals, open the upper infusion pipe switch of the bacterial solution tank to inject 24 hours of bacterial solution under pressure, followed by 1 hour of clean water injection after a certain period. After each injection cycle, clean water must be injected to clean all pipes. The above injection process constitutes one injection cycle, which is repeated for 3 to 5 cycles. Once the collected liquid layer has solidified, stop the injection operation and close all infusion and injection switches.

[0088] like Figure 7 As shown, during the stratified injection process, the bacterial solution injected in the same layer comes into contact with the cementing fluid to form calcium carbonate precipitate. After the lower layer injection is completed, the upper layer injection begins. The cementing fluid injected in the upper layer seeps downward and continues to undergo mineralization reaction with the bacterial solution present in the lower soil layer, continuing to form calcium carbonate precipitate in the soil pores. By adopting a stratified injection method with staggered double-layer injection holes and injecting the lower layer first and then the upper layer, a liquid collection layer 19 with a continuous concave-convex structure is finally formed at the bottom of the stope. After the liquid collection layer is consolidated, injection is stopped, and diversion holes 17 and liquid collection tunnels 18 are arranged in the concave area on the upper surface of the liquid collection layer. The height of the liquid collection tunnel is 1m, the width is 0.8m, and the distance between two adjacent liquid collection tunnels is 30m.

[0089] As a key component of the W-shaped liquid collection structure, the liquid collection layer's high stability and impermeability effectively prevent the leachate from leaking into the unconsolidated layer 20. Of particular note is the guiding effect of the W-shaped liquid collection structure, which facilitates the accumulation and centralized recovery of rare earth mother liquor in the depression area, ultimately returning it to the collection tank through the guide holes and collection tunnels.

[0090] In this embodiment, the injection intervals for bacterial solution, cementing solution, and water are as follows: when injecting the lower layer, water is injected 6 hours after the bacterial solution is injected, and cementing solution is injected 1 hour after the water is injected; after an interval of 48 hours, the upper layer injection begins, water is injected 6 hours after the cementing solution is injected, bacterial solution is injected 1 hour after the water is injected, and water is injected 72 hours later.

[0091] The concentration of the bacterial solution injected into the bottom soil was OD600 =0.8, the cementing solution is a mixed solution of urea and calcium chloride with equimolar concentrations, and the concentrations of calcium chloride and urea are both 1.0 mol / L. In one cycle, the upper and lower injection holes are injected with bacterial solution and cementing solution once each. The entire injection process is carried out in 3 to 5 cycles.

[0092] At the foot of the mountain, two bacterial solution pools and two cementing solution pools are set up, one clear water pool is set up, and another solution pool is set up as a backup pool. Each solution pool is 5m deep and 10m long and wide.

[0093] The upper and lower layers use independent infusion tubing, with three input terminals and multiple output terminals at each end. The three input terminals are located in the bacterial culture tank, the cementing solution tank, and the clear water tank, respectively, while the output terminals are connected to the input terminals of the injection tubing on the same layer. A switch and flow indicator are installed near each input terminal. During the injection process, the corresponding switch is activated according to the injection requirements to deliver the required solution, while the flow indicator displays the total flow rate and the daily flow rate in real time.

[0094] The injection holes for creating the liquid collection layer are arranged at a 5° upward angle along the horizontal plane, with a hole diameter of 12cm. The vertical interval between the openings of the injection holes in the upper and lower layers is 1.0m, and the horizontal interval between the openings of two adjacent injection holes in the same layer is 3m. The horizontal spacing between the injection holes is equal, and all injection holes are distributed in a W-shape around the foot of the mountain.

[0095] The injection pipe has a diameter of 10cm and its length is automatically adjusted according to the depth of the injection hole. An outlet with a diameter of 2cm is located at the bottom of the pipe, which extends into the soil. The distance between two adjacent outlets is 4cm. The upper part is a sealed structure. The injection pipe is also equipped with a switch, a flow rate indicator, and a pressure indicator. The switch controls the flow rate of the solution in the injection pipe, the flow rate indicator displays the flow rate and total flow rate of the solution, and the pressure indicator displays the current injection pressure.

[0096] After injecting the bacterial solution, the main purpose of injecting clean water is to effectively flush out any residual bacterial solution in the infusion and injection tubes. At the same time, it avoids the rapid formation of calcium carbonate precipitation near the injection hole due to the large amount of contact between the bacterial solution and the cementing solution, which would lead to uneven distribution of calcium carbonate, block the pores, and affect the injection of subsequent solutions.

[0097] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology, characterized in that, The method includes: S1. Arrange the injection pipe: Drilling rigs are used to construct injection holes at the bottom of the mining area. The injection holes are arranged in two layers in a W-shape. The opening of the lower layer injection hole is 0.5 to 1.5 m above the ground. The output end of the injection pipe is inserted into the injection hole. The injection pipes in the same layer are arranged in parallel. After the injection pipes are arranged, the opening of the injection hole is sealed to provide a sealed environment for subsequent pressurized injection. S2. Arrange the solution tank: A solution pool is arranged at a distance of 30 to 100 m from the injection hole. The solution pool includes a bacterial solution pool, a cementing solution pool, and a clear water pool. The solution pool is connected to the injection pipe through an infusion pipe. S3. Injection: A layered injection method is used to sequentially inject bacterial solution, cementing solution, and clean water into the soil at the bottom of the mining area under pressure, forming a W-shaped liquid-collecting layer with a continuous concave-convex structure. S4. Arrange guide holes and liquid collection tunnels: After the liquid collection layer is solidified, liquid collection guide holes and liquid collection tunnels are arranged in the recessed area on the upper surface of the liquid collection layer, with an interval of 30 to 40 meters between two adjacent liquid collection tunnels. The layered injection in step S3 includes a lower layer injection and an upper layer injection; First, perform the lower-level infusion: Open the lower-level infusion pipe and injection pipe switches of the bacterial solution tank, and inject the bacterial solution that has been stored for 24-48 hours under pressure. Use the pressure booster on the injection pipe to apply pressure to the bacterial solution in the injection pipe. After the bacterial solution is injected, open the lower-level infusion pipe switch of the clear water tank after 4-6 hours, and inject clear water for 1 hour to flush the infusion and injection pipes. After the clear water injection is completed, wait 1 hour, then open the lower-level infusion pipe switch of the cementing solution tank, and inject the cementing solution that has been stored for 24-48 hours under pressure. After the cementing solution is injected, inject clear water for 1 hour to flush the infusion and injection pipes. After the clear water injection is completed, close the lower-level infusion and injection pipe switches. Then proceed with the upper layer injection: Open the upper infusion pipe switch and the injection pipe switch of the cementing solution tank, and inject the cementing solution for 24-48 hours under pressure. After the cementing solution injection is completed, inject clean water for 1 hour after an interval of 4-6 hours. After the clean water injection is completed, wait 1 hour, then open the upper infusion pipe switch of the bacterial solution tank, and inject the bacterial solution for 24-48 hours under pressure. After an interval of 72 hours, inject clean water for 1 hour to clean the pipes. The stratified injection process is repeated until the liquid collection layer has solidified, at which point the injection operation is stopped and all infusion tube switches and injection tube switches are closed.

2. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, An infusion switch and a flow meter are installed on the infusion tube. The upper or lower infusion tube switch is opened in time according to the infusion needs to deliver the solution to the infusion tube.

3. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, The injection pipe is equipped with an injection switch, a flow meter, and a pressure booster. During the injection process, the upper or lower injection pipe switch is opened according to the injection requirements. The pressure booster applies sufficient pressure to the solution in the injection pipe to ensure the smooth progress of the injection process.

4. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, The bacterial solution is a Bacillus pasteurellii bacterial solution with a concentration of OD0.

05. 600 =0.6~1.

5. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, The cementing solution is a 1:1 molar mixture of urea and calcium chloride, with the concentrations of calcium chloride and urea being 0.5–1.5 mol / L.

6. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, During the injection process, bacterial solution and cementing solution are injected into the upper and lower injection holes once each in one cycle, and the entire injection process is carried out in 3 to 5 cycles.

7. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, The injection holes are arranged at an upward inclination of 3 to 8 degrees along the horizontal plane, with a diameter of 10 to 15 cm. The vertical interval between the openings of the upper and lower layers of injection holes is 0.8 to 1.5 m, and the horizontal interval between the openings of two adjacent injection holes in the same layer is 3 to 4 m. The horizontal spacing between the injection holes is equal.

8. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, The guide holes and collection tunnels are arranged in the recessed area on the upper surface of the liquid collection layer. The guide holes are arranged at an angle of 3 to 8 degrees upward along the horizontal plane, with a diameter of 10 to 15 cm. The height of the collection tunnel is 1 to 1.4 m and the width is 0.8 to 1 m.

9. The method for fabricating a W-shaped liquid collection structure at the bottom of a rare earth mine based on biotechnology according to claim 1, characterized in that, Two bacterial solution tanks and two cementing solution tanks are arranged, one clear water tank is arranged, and an additional solution tank is arranged as a spare tank. Each solution tank is 5m deep and 10m long and wide.

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