Device and method for preparing particle-scale microbial cemented sample

Abstract

The invention discloses a device and a method for preparing a particle-scale microorganism cemented sample, belongs to the technical field of microorganism reinforcement, and aims to solve the technical problems of difficulty in preparing the particle-scale microorganism cemented sample and low success rate in the prior art. The device comprises a mold top cover, a mold base and a plurality of sample preparation units, the sample preparation unit comprises a grouting pipe, a plurality of positioning holes, a plurality of particles respectively arranged on the plurality of positioning holes, and drainage grooves formed among the plurality of positioning holes. According to the device and the method for preparing the particle-scale microorganism cementation sample, the particle-scale microorganism cementation sample can be efficiently prepared, calcium carbonate cementation is formed among particles, and sample support is provided for research on mechanical properties of the particle-scale microorganism cementation sample.

Description

Technical Field

[0001] The invention relates to the technical field of microbial reinforcement, and in particular to a device and a method for preparing a particle-scale microbial cementation sample. Background Art

[0002] Microbial reinforcement technology is an emerging green and environmentally friendly reinforcement technology that has attracted much attention in recent years. Many scholars in the field of geotechnical engineering have conducted research on this technology. Microbial reinforcement technology uses microbial metabolic activities to produce urease. Calcium carbonate ions produced by the hydrolysis of urea under the catalysis of urease combine with added calcium ions to form calcium carbonate, which fills the gaps between rock and soil particles to form an effective cementation effect, improve the mechanical properties of the soil, and meet specific engineering needs. Compared with traditional engineering cementitious materials, such as silicate cement, lime, asphalt and other cementitious materials, microbial reinforcement technology has low carbon emissions and environmentally friendly characteristics, which makes this reinforcement technology have a wide range of application prospects.

[0003] Microbial reinforcement technology has been extensively studied in laboratories and on-site, including unit tests, model specimens and field tests. Tests have shown that microbial reinforcement technology can be used to improve the physical and mechanical properties of soil, such as increasing strength, resistance to liquefaction, resistance to erosion, and reducing particle crushing and compressibility. In addition, the microstructure of microbial cementation was studied using electron scanning microscopy (SEM) and X-ray computed tomography (CT), and it was found that the improvement in the mechanical properties of microbial reinforced soil was mainly caused by effective microbial cementation between particles.

[0004] The study of mechanical properties of microbial cementation at the particle scale explains the intrinsic microscopic mechanism of the macroscopic mechanical response of microbial cemented soil, and is an important part of the study of multi-scale mechanical properties of microbial cemented rock and soil. Moreover, the numerical simulation (discrete element method) and related constitutive theory research of microbial cemented rock and soil require the support of particle-scale microbial cementation tests. However, the preparation of particle-scale microbial cementation samples is difficult and has a low success rate. At present, there is no systematic and effective cementation method and device, which makes the particle-scale microbial cementation tests very rare, limiting the progress of the research on the mechanical properties of particle-scale microbial cementation. Summary of the invention

[0005] The purpose of the present invention is to provide a device and a method for preparing particle-scale microbial cementation samples, so as to solve the technical problems in the prior art of particle-scale microbial cementation sample preparation, sample preparation difficulty and low success rate.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a device for preparing a particle-scale microbial cementation sample, comprising a mold top cover, a mold base and a plurality of sample preparation units;

[0008] The sample preparation unit comprises a grouting pipe, a plurality of positioning holes, a plurality of particles respectively arranged on the plurality of positioning holes, and a drainage groove arranged between the plurality of positioning holes.

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

[0010] A positioning pipe is provided on the mold top cover, and the grouting pipe is passed through the positioning pipe and is located above the middle of the drainage groove.

[0011] Optionally or preferably, the grouting pipe comprises a main pipe and a plurality of branch pipes arranged in an annular array outside the main pipe;

[0012] The end of the branch pipe has an inclined section, and the direction of the inclined section is inclined from the side close to the main pipe to the side 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 material; the main pipe is made of stainless steel; and the branch pipe is made of silicone material.

[0015] A method for preparing a particle-scale microbial cementation sample comprises the following steps:

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

[0017] S2, placing one end of the main pipe and the branch pipe in containers containing bacterial solution and cementing solution respectively, and inserting the other end into the positioning pipe;

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

[0019] S4, after the bacterial solution and the cementing solution are mixed at the lower end of the grouting pipe, they are dripped between two adjacent particles and form calcium carbonate precipitation, thereby cementing the two adjacent particles and forming calcium carbonate cementation between the two particles;

[0020] S5. After the cementation is completed, the preparation device and the cemented particles are placed in deionized water and allowed to stand to solidify the calcium carbonate cementation between the particles and complete the initial solidification;

[0021] S6, taking out the cemented particles from the preparation device, and placing them in deionized water again to stand to further remove residual calcium chloride and other salts;

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

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

[0024] Optionally or preferably, the bacterial solution in S3 is a Bacillus pasteurianus solution, and its optical density value OD 600 =1.563-1.862, pH value of bacterial solution is 8.9-9.5, and urease activity is 1.20urea / min-1.86urea / min.

[0025] Optionally or preferably, the bonding solution described in S3 is a mixed solution of CaCl2 solution and urea solution; wherein the concentration of the CaCl2 solution is 0.5 mol / L, the concentration of the 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 that of the cementing solution is 29.33 μL / min.

[0027] Optionally or preferably, when calculating the bonding strength of the calcium carbonate cementation in S7, the diameter of the calcium carbonate cementation at at least three different positions is measured by a micrometer, and the average value of the three diameter measurements is taken as the equivalent diameter, so as to estimate the cross-sectional area and further calculate the bonding strength of the calcium carbonate cementation.

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

[0029] The device and method for preparing a particle-scale microbial cementation sample provided by the present invention can efficiently prepare a particle-scale microbial cementation sample, form calcium carbonate cementation between particles, and provide sample support for the study of mechanical properties of particle-scale microbial cementation.

[0030] At the same time, the present invention has wide applicability and can be used to study the effects of factors such as particle materials, cementing materials, inter-particle distance and cementing degree on inter-particle microbial cementation, and can simultaneously perform cementation of multiple groups of particle pairs, saving preparation time and improving sample preparation efficiency and success rate;

[0031] In addition, in the device provided by the present invention, the mold top cover is made of a transparent acrylic plate. During operation, the microbial bonding between the particles can be observed in real time, so that sampling, monitoring and adjustment can be carried out simultaneously, thereby ensuring the smooth progress of the test sample preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of a device for preparing a particle-scale microbial cementation sample according to the present invention;

[0033] Figure 2 It is a structural schematic diagram of a single sample preparation unit in the device for preparing a particle-scale microbial cementation sample of the present invention;

[0034] Figure 3 It is a schematic longitudinal section of a single sample preparation unit in the device for preparing a particle-scale microbial cementation sample of the present invention;

[0035] Figure 4 It is a schematic diagram of the structure of the cementing sample in the device for preparing the particle-scale microbial cementing sample of the present invention;

[0036] Figure 5 The present invention is a flow chart of the method for preparing a particle-scale microbial cementation sample.

[0037] In the figure: 1. mold top cover; 2. mold base; 3. grouting pipe; 31. main pipe; 32. branch pipe; 4. positioning hole; 5. drainage groove; 6. particles; 7. positioning pipe; 8. calcium carbonate cementation. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work belong to the scope of protection of the present invention.

[0039] Embodiment 1

[0040] See also Figures 1 to 4 A device for preparing a particle-scale microbial cementation sample includes a mold top cover 1 and a mold base 2, and a plurality of sample preparation units are arranged on the mold top cover 1 and the mold base 2.

[0041] In order to enable the operator to observe the microbial bonding between particles in real time during operation, and to prepare samples, monitor and adjust at the same time, 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 sample preparation unit includes a plurality of positioning holes 4 arranged on the mold base 2, and the plurality of positioning holes 4 are arranged in pairs, on which particles 6 are arranged. It can be understood that the particles 6 are also arranged in pairs, and the paired particles 6 are cemented to obtain a cemented sample; the sample preparation unit also includes a drainage groove 5 and a grouting pipe 3, the drainage groove 5 is arranged between the paired positioning holes 4, and the grouting pipe 3 is arranged above the midpoint of the drainage groove 5; please refer to Figure 2 and Figure 3 The bacterial solution and cementing solution from the grouting pipe 3 can directly act between the paired particles 6, and the solution after the action is discharged through the drainage ditch 5.

[0043] In this embodiment, the grouting pipe 3 is used to provide bacterial solution and cementing solution for cementing to the paired particles 6, and includes a main pipe 31 and two branch pipes 32 arranged on the outside of the main pipe 31; the main pipe 31 is used to transport the bacterial solution, and the branch pipe 32 is used to transport the cementing solution. The bacterial solution and the cementing solution are first mixed and then dripped at the outlet of the lower end of the grouting pipe 3, and act on the paired particles 6, so as to avoid the formation of calcium carbonate precipitation in the pipe and block the pipe.

[0044] In order to allow 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, and the inclination direction of the inclined surface is from the side close to the main pipe 31 to the side 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 rubber.

[0046] Embodiment 2

[0047] This embodiment provides a method for preparing a particle-scale microbial cementation sample based on the first embodiment, comprising the following steps:

[0048] S1, washing the particles 6 with deionized water and drying them, measuring their mass with an analytical balance before bonding, and placing the particles 6 on the corresponding positioning holes 4;

[0049] In this embodiment, the cementing sample is cemented with spherical quartz particles and calcareous particles; the diameter of the particle 6 is 6 mm and is made by grinding natural coral sand; in the cementing sample, the gap between the paired particles 6 is 1 mm-2 mm, and in this embodiment, the gap between the paired particles 6 is 1.5 mm.

[0050] S2, placing one end of the main pipe 31 and the branch pipe 32 into containers containing bacterial solution and cementing solution respectively, and the other end is passed through the positioning pipe 7;

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

[0052] In this embodiment, the bacterial solution introduced into the main pipe 31 is a pasteurian bacterial solution, and its optical density value OD 600 =1.563, the pH value of the bacterial solution was 9.0, and the urease activity was 1.20urea / min.

[0053] The method for preparing the above-mentioned Bacillus pasteurianus bacterial solution is as follows: dissolving the freeze-dried powder of Bacillus pasteurianus into a suspension, and then inoculating the suspension into a liquid culture medium for activation. The activated bacterial solution and the sterilized 80% glycerol aqueous solution are mixed in a mixing ratio of 4:1, and frozen to -80°C for storage. When used, 1mL of the glycerol bacterial solution is inoculated into 500mL of liquid culture medium, and then placed in a constant temperature shock box at 30°C and cultured at a constant shaking rate of 200rpm for 24 hours. The liquid culture medium is composed of yeast extract, NH4Cl, MnSO4·H2O and NiCl2·6H2O. The specific amount is taken as an example of 1L of liquid culture medium: 20g yeast extract, 10gNH4Cl, 10mg MnSO4·H2O and 24mgNiCl2·6H2O. At the same time, 1mol / L NaOH solution is required to adjust the pH of the liquid culture medium to 9.2-9.3.

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

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

[0056] S4, after the bacterial solution and the cementing solution are mixed at the lower end of the grouting pipe 3, they are dripped between two adjacent particles 6 and form calcium carbonate precipitation, thereby cementing the two adjacent particles 6, and forming a calcium carbonate cementation 8 between the two particles 6;

[0057] S5, after the cementation is completed, the preparation device and the cemented particles 6 are placed in deionized water and left to stand for 24 hours to solidify the calcium carbonate cementation 8 between the particles and complete the initial solidification;

[0058] S6, taking out the cemented particles 6 from the preparation device, and placing them in deionized water again for 48 hours to further remove residual calcium chloride and other salts;

[0059] S7, drying, weighing, and calculating the content and bonding 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 positions using a micrometer, and take the average of the three diameter measurement values ​​as the equivalent diameter, thereby estimating the cross-sectional area, and then calculating the bonding strength of the calcium carbonate cement 8.

[0061] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

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

Claims

1. A device for preparing a particle-scale microbial cementation sample, characterized in that: It comprises a mold top cover (1), a mold base (2) and a plurality of sample preparation units; The sample preparation unit comprises a grouting pipe (3), a plurality of positioning holes (4), a plurality of particles (6) respectively arranged on the plurality of positioning holes (4), and a drainage groove (5) arranged between the plurality of positioning holes (4).

2. The device for preparing a particle-scale microbial cementation sample according to claim 1, characterized in that: The positioning holes (4) are arranged in pairs; a drainage groove (5) is arranged between each pair of the positioning holes (4); A positioning pipe (7) is provided on the mold top cover (1), and the grouting pipe (3) is passed through the positioning pipe (7) and is located above the middle of the drainage groove (5).

3. The device for preparing a particle-scale microbial cementation sample according to claim 1, characterized in that: The grouting pipe (3) comprises a main pipe (31) and a plurality of branch pipes (32) arranged outside the main pipe (31); The end of the branch pipe (32) has an inclined section, and the direction of the inclined section is inclined from the side close to the main pipe (31) to the side 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).

4. The device for preparing a particle-scale microbial cementation sample according to claim 3, characterized in that: The mold top cover (1) is made of acrylic material; the main pipe (31) is made of stainless steel; and the branch pipe (32) is made of silicone material.

5. A method for preparing a particle-scale microbial cementation sample, characterized in that: The device for preparing a particle-scale microbial cementation sample according to any one of claims 1 to 4 is used to prepare a cementation sample, comprising the following steps: S1, washing the particles (6) with deionized water and drying them, measuring their mass with an analytical balance before bonding, and placing the particles (6) on the corresponding positioning holes (4); S2, placing one end of the main pipe (31) and the branch pipe (32) in containers containing a bacterial solution and a cementing solution respectively, and inserting the other end into the positioning pipe (7); S3, using a peristaltic pump to pump the bacterial solution and the cementing solution into the main pipe (31) and the branch pipe (32) at a constant rate; S4, the bacterial solution and the cementing solution are mixed at the lower end of the grouting pipe (3), and then dripped between two adjacent particles (6), and calcium carbonate precipitation is formed, thereby cementing the two adjacent particles (6), and calcium carbonate cementation (8) is formed between the two particles (6); S5, after the cementation is completed, the preparation device and the cemented particles (6) are placed in deionized water and allowed to stand to solidify the calcium carbonate cementation between the particles (8) and complete the initial solidification; S6, taking out the cemented particles (6) from the preparation device, and placing them in deionized water again to stand to further remove residual calcium chloride and other salts; S7, drying, weighing, and calculating the content and bonding strength of the generated calcium carbonate cement (8).

6. The method for preparing a particle-scale microbial cementation sample according to claim 5, characterized in that: The diameter of the particles (6) in S1 is 6 mm, and the material is natural coral sand; the distance between adjacent particles (6) is 1 mm-2 mm.

7. The method for preparing a particle-scale microbial cementation sample according to claim 5, characterized in that: The bacterial solution described in S3 is a Bacillus pasteurianus solution, and its optical density value OD 600 =1.563-1.862, pH value of bacterial solution is 8.9-9.5, and urease activity is 1.20urea / min-1.86urea / min.

8. The method for preparing a particle-scale microbial cementation sample according to claim 5, characterized in that: The cementing solution described in S3 is a mixed solution of CaCl2 solution and urea solution; wherein the concentration of the CaCl2 solution is 0.5 mol / L, the concentration of the urea solution is 0.5 mol / L, and the concentration ratio of the two is 1:

1.

9. The method for preparing a particle-scale microbial cementation sample according to claim 5, characterized in that: The ratio of the pumping rate of the bacterial solution and the cementing solution in S3 was 1:4; the pumping rate of the bacterial solution was 7.33 μL / min, and that of the cementing solution was 29.33 μL / min.

10. The method for preparing a particle-scale microbial cementation sample according to claim 5, characterized in that: When calculating the bonding strength of the calcium carbonate cement (8) in S7, the diameter of the calcium carbonate cement (8) at least three different positions is measured by a micrometer, and the average value of the three diameter measurements is used as the equivalent diameter, so as to estimate the cross-sectional area and further calculate the bonding strength of the calcium carbonate cement (8).

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