An apparatus and method for preparing particulate-scale microbial cemented samples.

Abstract

This invention discloses an apparatus and method for preparing particle-scale microbial cemented samples, belonging to the field of microbial reinforcement technology, to solve the technical problems of difficult sample preparation and low success rate in the preparation of particle-scale microbial cemented samples in the prior art. It includes a mold top cover, a mold base, and multiple sample preparation units; each sample preparation unit includes a grouting pipe, multiple positioning holes, multiple particles respectively disposed on the positioning holes, and drainage channels disposed between the positioning holes. The apparatus and method of this invention for preparing particle-scale microbial cemented samples can efficiently produce particle-scale microbial cemented samples, forming calcium carbonate cement between particles, providing sample support for the study of the mechanical properties of particle-scale microbial cementation.

Description

Technical Field

[0001] This invention relates to the field of microbial reinforcement technology, specifically to an apparatus and method for preparing particle-scale microbial cemented samples. Background Technology

[0002] Microbial reinforcement technology is an emerging green and environmentally friendly reinforcement technology that has attracted much attention in recent years, with many scholars in the field of geotechnical engineering conducting research on it. Microbial reinforcement technology utilizes the urease produced by the metabolic activities of microorganisms. Under the catalysis of urease, urea hydrolyzes, producing calcium carbonate ions that combine with added calcium ions to form calcium carbonate, which fills the gaps between soil particles, forming an effective cementing effect, improving the mechanical properties of the soil, and meeting specific engineering requirements. Compared to traditional engineering cementing materials, such as silicate cement, lime, and asphalt, microbial reinforcement technology has low carbon emissions and environmentally friendly characteristics, making it a promising technology with broad application prospects.

[0003] Extensive research has been conducted in both laboratory and field studies on microbial soil and rock reinforcement technology, including unit tests, model specimens, and field tests. Experiments have shown that microbial reinforcement technology can improve the physical and mechanical properties of soil, such as increasing strength, liquefaction resistance, erosion resistance, and reducing particle fragmentation and compressibility. Furthermore, the microstructure of microbial cementation, studied using scanning electron microscopy (SEM) and X-ray computed tomography (CT), has revealed that the improvement in the mechanical properties of microbially reinforced soil and rock is primarily due to effective microbial cementation between particles.

[0004] The study of the mechanical properties of microbially cemented soils at the particle scale elucidates the intrinsic microscopic mechanism of the macroscopic mechanical response, and is a crucial part of the research on the multi-scale mechanical properties of microbially cemented soils and rocks. Furthermore, numerical simulations (discrete element method) and related constitutive theory studies of microbially cemented soils and rocks require particle-scale microbial cementation experiments as support. However, the preparation of particle-scale microbially cemented samples is difficult and has a low success rate. Currently, there are no systematic and effective cementation methods and apparatus, resulting in a limited number of particle-scale microbial cementation experiments, which restricts the progress of research on the mechanical properties of particle-scale microbially cemented soils. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and method for preparing particle-scale microbial cemented samples, so as to solve the technical problems of difficult sample preparation and low success rate in the preparation of particle-scale microbial cemented samples in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides an apparatus for preparing particulate-scale microbial cemented samples, comprising a mold top cover, a mold base, and multiple sample preparation units;

[0008] The sample preparation unit includes a grouting pipe, multiple positioning holes, multiple particles respectively disposed on the multiple positioning holes, and a drainage groove disposed between the multiple positioning holes.

[0009] Optionally or preferably, the positioning holes are arranged in pairs; a drainage groove is provided between each pair of positioning holes;

[0010] The top cover of the mold is provided with a positioning pipe, and the grouting pipe passes through the positioning pipe and is located above the middle of the drainage groove.

[0011] Optionally or preferably, the grouting pipe includes a main pipe and a plurality of branch pipes arranged in a ring around the outside of the main pipe;

[0012] The end of the branch pipe has an inclined cut surface, which is inclined from the side closer to the main pipe to the side farther away from the main pipe, so that a gap is formed between the end of the branch pipe and the outer wall of the main pipe.

[0013] The diameter of the branch pipe is smaller than that of the main pipe.

[0014] Optionally or preferably, the mold top cover is made of acrylic; the main pipe is made of stainless steel; and the branch pipe is made of silicone.

[0015] A method for preparing particulate-scale microbial cemented samples includes the following steps:

[0016] S1. Wash the particles with deionized water and dry them. Before bonding, measure their mass with an analytical balance and place the particles on the corresponding positioning holes.

[0017] S2. Place one end of the main pipe and one end of the branch pipe into containers containing bacterial solution and cementing solution respectively, and insert the other end into the positioning pipe.

[0018] S3. Use a peristaltic pump to pump the bacterial solution and cementing solution into the main pipe and branch pipes at a constant rate;

[0019] S4. After the bacterial solution and cementing solution are mixed at the lower end of the grouting pipe, they drip between two adjacent particles and form calcium carbonate precipitate, thereby cementing the two adjacent particles and forming calcium carbonate cement between the two particles.

[0020] S5. After the bonding is completed, the preparation device and the bonded particles are placed together in deionized water and left to stand to solidify the calcium carbonate bonding between the particles and complete the initial curing.

[0021] S6. Remove the cemented particles from the preparation device and place them in deionized water again to stand, further removing residual calcium chloride and other salts.

[0022] S7. Dry, weigh, and calculate the content and strength of the generated calcium carbonate cement.

[0023] Optionally or preferably, the diameter of the particles in S1 is 6mm, and the material is natural coral sand; the spacing between adjacent particles is 1mm-2mm.

[0024] Optionally or preferably, the bacterial solution described in S3 is a Bacillus pasteurellium bacterial solution with an optical density value OD. 600 =1.563-1.862, bacterial culture pH value is 8.9-9.5, urease activity is 1.20urea / min-1.86urea / min.

[0025] Optionally or preferably, the cementing solution in S3 is a mixture of CaCl2 solution and urea solution; wherein the concentration of CaCl2 solution is 0.5 mol / L, the concentration of urea solution is 0.5 mol / L, and the concentration ratio of the two is 1:1.

[0026] Optionally or preferably, the ratio of the pumping rates of the bacterial solution and the cementing solution in S3 is 1:4; wherein the pumping rate of the bacterial solution is 7.33 μL / min and the pumping rate of the cementing solution is 29.33 μL / min.

[0027] Optionally or preferably, in S7, when calculating the bonding strength of the calcium carbonate bond, the diameter of the calcium carbonate bond at at least three different locations is measured with a micrometer, and the average of the three diameter measurements is used as the equivalent diameter to estimate the cross-sectional area, and then the bonding strength of the calcium carbonate bond is calculated.

[0028] Based on the above technical solution, the present invention can produce at least the following technical effects:

[0029] The apparatus and method for preparing particle-scale microbial cemented samples provided by this invention can efficiently produce particle-scale microbial cemented samples, forming calcium carbonate cement between particles, and providing sample support for the study of the mechanical properties of particle-scale microbial cementation.

[0030] Meanwhile, the present invention has wide applicability and can be used to study the effects of factors such as particulate materials, cementing materials, interparticle distance and degree of cementation on interparticle microbial cementation. It can also perform cementation of multiple sets of particle pairs at the same time, saving preparation time and improving sample preparation efficiency and success rate.

[0031] Furthermore, in the device provided by this invention, the mold top cover is made of transparent acrylic sheet, which allows for real-time observation of the microbial bonding between particles during operation, enabling simultaneous sample preparation, monitoring, and adjustment, thereby ensuring the smooth progress of the experimental sample preparation. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the apparatus for preparing particle-scale microbial cemented samples according to the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of a single sample preparation unit in the apparatus for preparing particulate-scale microbial cemented samples according to the present invention.

[0034] Figure 3 This is a longitudinal cross-sectional schematic diagram of a single sample preparation unit in the apparatus for preparing particulate-scale microbial cemented samples according to the present invention.

[0035] Figure 4 This is a schematic diagram of the structure of the cemented sample in the apparatus for preparing particle-scale microbial cemented samples according to the present invention.

[0036] Figure 5 This is a flowchart of the method for preparing particle-scale microbial cemented samples according to the present invention.

[0037] In the diagram: 1. Mold top cover; 2. Mold base; 3. Grouting pipe; 31. Main pipe; 32. Branch pipe; 4. Positioning hole; 5. Drainage trough; 6. Granules; 7. Positioning pipe; 8. Calcium carbonate cement. Detailed Implementation

[0038] The technical solutions of the embodiments 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, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] Please see Figures 1 to 4 An apparatus for preparing particulate-scale microbial cemented samples includes a mold top cover 1 and a mold base 2, with multiple sample preparation units disposed on the mold top cover 1 and the mold base 2.

[0041] In order to enable operators to observe the microbial cementation between particles in real time during operation, and to make adjustments while preparing samples, thereby ensuring the smooth progress of the test sample preparation, in this embodiment, the mold top cover 1 is made of transparent acrylic material.

[0042] The aforementioned sample preparation unit includes multiple positioning holes 4 disposed on the mold base 2. These positioning holes 4 are arranged in pairs and are used to hold particles 6. It is understood that the particles 6 are also arranged in pairs. The paired particles 6 are then bonded together to obtain a bonded sample. The sample preparation unit also includes a drainage trough 5 and a grouting pipe 3. The drainage trough 5 is disposed between the paired positioning holes 4, and the grouting pipe 3 is positioned above the midpoint of the drainage trough 5. Please refer to [link to relevant documentation]. Figure 2 and Figure 3 The bacterial solution and cementing solution from the grouting pipe 3 can act directly on the paired particles 6, and the resulting solution is discharged through the drainage trough 5.

[0043] In this embodiment, the grouting pipe 3 is used to provide a bacterial solution and a cementing solution for bonding to the paired particles 6. It includes a main pipe 31 and two branch pipes 32 disposed outside the main pipe 31. The main pipe 31 is used to transport the bacterial solution, and the branch pipes 32 are used to transport the cementing solution. The bacterial solution and the cementing solution are mixed at the lower outlet of the grouting pipe 3 and then drip down, acting on the paired particles 6. This can prevent calcium carbonate from precipitating in the pipe and forming and clogging the pipe.

[0044] In order to enable the bacterial solution and the cementing solution to mix and drip smoothly at the lower end of the grouting pipe 3, in this embodiment, the lower end of the branch pipe 32 has an inclined surface. The inclined surface is inclined from the side closer to the main pipe 31 to the side farther away from the main pipe 31, so that a gap is formed between the end of the branch pipe 32 and the outer wall of the main pipe 31.

[0045] In this embodiment, the diameter of the branch pipe 32 is smaller than that of the main pipe 31; the main pipe 31 is made of stainless steel, and the branch pipe 32 is made of silicone.

[0046] Example 2

[0047] Based on Example 1, this embodiment provides a method for preparing particle-scale microbial cemented samples, including the following steps:

[0048] S1. Wash particles 6 with deionized water and dry them. Before bonding, measure their mass with an analytical balance and place particles 6 on the corresponding positioning holes 4.

[0049] In this embodiment, the cemented sample is cemented using spherical quartz particles and calcium particles; wherein the diameter of particle 6 is 6mm and it is made by polishing natural coral sand; in the cemented sample, the gap between the paired particles 6 is 1mm-2mm, and in this embodiment, the gap between the paired particles 6 is 1.5mm.

[0050] S2. Place one end of the main pipe 31 and the branch pipe 32 into containers containing bacterial solution and cementing solution respectively, and insert the other end into the positioning pipe 7.

[0051] S3. Use a peristaltic pump to pump the bacterial solution and cementing solution into the main pipe 31 and branch pipe 32 at a constant rate;

[0052] In this embodiment, the bacterial solution introduced into the main pipe 31 is a Bacillus pasteurellium bacterial solution, with an optical density value OD. 600 =1.563, bacterial culture pH value is 9.0, urease activity is 1.20urea / min.

[0053] The method for preparing the above-mentioned *Pasteurella multocida* bacterial suspension is as follows: *Pasteurella multocida* lyophilized powder is dissolved into a suspension, and then the suspension is inoculated into a liquid culture medium for activation. The activated bacterial solution and sterilized 80% glycerol aqueous solution are mixed at a ratio of 4:1 and stored at -80℃. When using, 1 mL of the glycerol bacterial solution is inoculated into 500 mL of liquid culture medium, and then placed in a constant temperature shaking incubator at 30℃ and cultured at a constant shaking rate of 200 rpm for 24 hours. The liquid culture medium consists of yeast extract, NH4Cl, MnSO4·H2O, and NiCl2·6H2O. For example, for 1 L of liquid culture medium, the specific dosage is: 20 g yeast extract, 10 g NH4Cl, 10 mg MnSO4·H2O, and 24 mg NiCl2·6H2O. The pH of the liquid culture medium needs to be adjusted to 9.2–9.3 using a 1 mol / L NaOH solution.

[0054] In this embodiment, the ratio of the pumping rates of the bacterial solution and the cementing solution is 1:4; wherein the pumping rate of the bacterial solution is 7.33 μL / min and the pumping rate of the cementing solution is 29.33 μL / min.

[0055] In this embodiment, the cementing solution is a mixture of CaCl2 solution and urea solution; wherein the concentration of CaCl2 solution is 0.5 mol / L, the concentration of urea solution is 0.5 mol / L, and the concentration ratio of the two is 1:1.

[0056] S4. After the bacterial solution and cementing solution are mixed at the lower end of the grouting pipe 3, they drip between two adjacent particles 6 and form calcium carbonate precipitate, thereby cementing the two adjacent particles 6 and forming calcium carbonate cement 8 between the two particles 6.

[0057] S5. After the bonding is completed, the preparation device and the bonded particles 6 are placed in deionized water and left to stand for 24 hours to solidify the interparticle calcium carbonate bonding 8 and complete the initial curing.

[0058] S6. Remove the cemented particles 6 from the preparation device and place them in deionized water again for 48 hours to further remove residual calcium chloride and other salts.

[0059] S7. Dry, weigh, and calculate the content and strength of the generated calcium carbonate cement 8.

[0060] In this embodiment, since the formed calcium carbonate cement 8 is not an ideal cylinder, when calculating the bonding strength of the calcium carbonate cement 8, it is necessary to measure the diameter of the calcium carbonate cement 8 at at least three different locations using a micrometer, and take the average of the three diameter measurements as the equivalent diameter to estimate the cross-sectional area, and then calculate the bonding strength of the calcium carbonate cement 8.

[0061] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An apparatus for preparing particle-scale microbial cemented samples, characterized in that, It includes a mold top cover (1), a mold base (2), and multiple sample preparation units; The sample preparation unit includes a grouting pipe (3), multiple positioning holes (4), multiple particles (6) respectively disposed on the multiple positioning holes (4), and a drainage groove (5) disposed between the multiple positioning holes (4); The positioning holes (4) are arranged in pairs; a drainage groove (5) is provided between each pair of positioning holes (4); The mold top cover (1) is provided with a positioning pipe (7), and the grouting pipe (3) passes through the positioning pipe (7) and is located above the middle part of the drainage trough (5); The grouting pipe (3) includes a main pipe (31) and a plurality of branch pipes (32) disposed outside the main pipe (31); The end of the branch pipe (32) has an inclined cut surface, the direction of which is inclined from the side closer to the main pipe (31) to the side farther away from the main pipe (31), so that a gap is formed between the end of the branch pipe (32) and the outer wall of the main pipe (31). The diameter of the branch pipe (32) is smaller than that of the main pipe (31).

2. The apparatus for preparing particle-scale microbial cemented samples according to claim 1, characterized in that, The mold top cover (1) is made of acrylic; the main pipe (31) is made of stainless steel; and the branch pipe (32) is made of silicone.

3. A method for preparing particle-scale microbial cemented samples, characterized in that, The apparatus for preparing particle-scale microbial cemented samples according to any one of claims 1-2 is used to prepare cemented samples, including the following steps: S1, washing the particles (6) with deionized water and drying them, measuring their mass with an analytical balance before cementation, and placing the particles (6) on the corresponding positioning holes (4). S2. Place one end of the main pipe (31) and the branch pipe (32) into containers containing bacterial solution and cementing solution respectively, and insert the other end into the positioning pipe (7); S3. Use a peristaltic pump to pump the bacterial solution and cementing solution into the main pipe (31) and branch pipe (32) at a constant rate; S4. After the bacterial solution and cementing solution are mixed at the lower end of the grouting pipe (3), they drip between two adjacent particles (6) and form calcium carbonate precipitate, thereby cementing the two adjacent particles (6) and forming calcium carbonate cement (8) between the two particles (6). S5. After the bonding is completed, the preparation device and the bonded particles (6) are placed together in deionized water and left to stand to solidify the calcium carbonate bonding between particles (8) and complete the initial curing. S6. Remove the cemented particles (6) from the preparation device and place them in deionized water again to stand, further removing residual calcium chloride and other salts. S7. Dry, weigh, and calculate the content and strength of the generated calcium carbonate cement (8).

4. The method for preparing particle-scale microbial cemented samples according to claim 3, characterized in that, The diameter of particle (6) in S1 is 6mm, and the material is natural coral sand; the spacing between adjacent particles (6) is 1mm-2mm.

5. The method for preparing particle-scale microbial cemented samples according to claim 3, characterized in that, The bacterial solution described in S3 is a Bacillus pasteurellis bacterial solution with an optical density value of OD600 = 1.563-1.862, a pH value of 8.9-9.5, and a urease activity of 1.20urea / min-1.86urea / min.

6. The method for preparing particle-scale microbial cemented samples according to claim 3, characterized in that, The cementing solution mentioned in S3 is a mixture of CaCl2 solution and urea solution; The concentrations of CaCl2 solution and urea solution are both 0.5 mol / L, with a concentration ratio of 1:

1.

7. The method for preparing particle-scale microbial cemented samples according to claim 3, characterized in that, The pumping rate ratio of the bacterial solution to the cemented solution in S3 is 1:4; the pumping rate of the bacterial solution is 7.33 μL / min, and the pumping rate of the cemented solution is 29.33 μL / min.

8. The method for preparing particle-scale microbial cemented samples according to claim 3, characterized in that, When calculating the bonding strength of calcium carbonate cement (8) in S7, the diameter of calcium carbonate cement (8) at least three different locations is measured by micrometer. The average value of the three diameter measurements is taken as the equivalent diameter to estimate the cross-sectional area and then calculate the bonding strength of calcium carbonate cement (8).

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