Microbial induced carbonate precipitation test device and method suitable for ct scanning

Abstract

The present application belongs to the technical field of unsaturated soil mechanics, and provides a microbial-induced calcium carbonate precipitation test device and method suitable for CT scanning. By setting a microbial-induced calcium carbonate precipitation sample in a transparent sample mold, CT scanning of the microbial-induced calcium carbonate precipitation can be realized. The microbial-induced calcium carbonate precipitation sample is located in the sample mold, avoiding the cutting of the sand column and improving the test results. Meanwhile, a flow sensor, a vacuum pressure gauge and a vacuum pump are arranged on the liquid outlet pipe. The matrix suction under different saturations can be calculated and controlled by controlling the bacterial solution and cementing fluid in the microbial-induced calcium carbonate precipitation sample. CT images and soil water characteristic curves of the microbial-induced calcium carbonate precipitation sample under different saturation conditions can be obtained, improving the flexibility of the test.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of unsaturated soil mechanics, and particularly relates to a microbial-induced calcium carbonate precipitation test device and method suitable for CT scanning. BACKGROUND

[0002] Microbial-induced calcite precipitation (MICP) is usually achieved by injecting urea bacteria and reagents, i.e., urea and calcium, to cement sand by using biologically active precipitated calcium carbonate; this technology has been used to enhance the mechanical properties of soil by using an energy-saving microbial metabolic process, and compared with other traditional technologies, this technology can significantly reduce carbon emissions; the mass production of cement often causes a series of ecological and environmental problems such as excessive carbon dioxide emissions, greenhouse effect and temperature rise; therefore, it is of great significance to apply biotechnology to the field of geotechnical engineering to reduce carbon emissions and protect the ecological environment.

[0003] The inventor finds that the principle of the traditional MICP technology is not embodied in the CT scanning process; the sand sample mold used in the test process is mostly a PVC pipe, and it is difficult to demold subsequently and cannot be directly used in the strength test; and the size of the sand column of the existing test instrument is too large, so that even if CT scanning can be performed, a clear image cannot be obtained; the experimental sample for CT scanning is cut into small pieces from the whole sand column so that it can be placed in an industrial CT scanning room for scanning; in the process of cutting the sand column, the pressure is unloaded, and structural disturbance of the experimental sample is inevitably caused, thereby affecting the test result and reducing the test accuracy. SUMMARY

[0004] To solve the above problems, the application provides a microbial-induced calcium carbonate precipitation test device suitable for CT scanning; the test device can be placed in an industrial CT scanning room for testing; the saturation and matrix suction of the cemented sand column can be controlled during the test process; CT scanning is performed in real time, and then the CT image of the cemented sand column under different saturation conditions and the soil-water characteristic curve of the cemented sand column are obtained; the cemented sand column can be taken out from the valve without damage, and the mechanical property test of the same sample and the mutual verification of the macroscopic and microscopic mechanisms of the microbial-induced calcite precipitation can be conveniently performed.

[0005] To achieve the above object, in a first aspect, the application provides a microbial-induced calcium carbonate precipitation test device suitable for CT scanning, which adopts the following technical scheme:

[0006] The microbial-induced calcium carbonate precipitation test device suitable for CT scanning comprises a sample mold for containing a microbial-induced calcium carbonate precipitation sample, which is a transparent mold; one end of the sample mold is provided with a liquid inlet pipe, and the other end is provided with a liquid outlet pipe; the liquid outlet pipe is provided with a flow sensor, a vacuum pressure gauge and a vacuum pump.

[0007] Further, a peristaltic pump is arranged on the liquid inlet pipe, and a liquid storage device is communicated with an end of the liquid inlet pipe away from the sample mold, and the liquid storage device contains bacteria liquid and cementing liquid.

[0008] Further, the side wall of the sample mold comprises a plurality of acrylic plates fixed together by a fixing ring.

[0009] Further, a rubber plug is arranged on the mouth of the sample mold, and a water permeable stone is arranged inside the lower end of the rubber plug; and a geomembrane is arranged between the rubber plug and the sample.

[0010] Further, an end of the liquid inlet pipe inside the sample mold extends to the middle of the sample, and a plurality of grouting holes are arranged on the liquid inlet pipe in the middle of the sample.

[0011] Further, a valve is arranged on the liquid outlet pipe.

[0012] Further, a collection bottle is communicated with an end of the liquid outlet pipe away from the sample mold.

[0013] Further, a radiation source, a rotating table and a detection plate are further included, the rotating table is arranged between the radiation source and the detection plate; and the radiation source is a CT scanning device.

[0014] In order to achieve the above-mentioned purpose, in the second aspect, the present application further provides a microbial induced calcium carbonate precipitation test method suitable for CT scanning, which adopts the following technical scheme:

[0015] The microbial induced calcium carbonate precipitation test method suitable for CT scanning adopts the microbial induced calcium carbonate precipitation test device suitable for CT scanning as described in the first aspect; and the method comprises the following steps:

[0016] Placing the sample mold containing the microbial induced calcium carbonate precipitation sample on the rotating table;

[0017] Aligning the irradiation direction of the radiation source with the sample mold; and injecting bacteria liquid and cementing liquid into the microbial induced calcium carbonate precipitation sample through the peristaltic pump;

[0018] Extracting the liquid in the microbial induced calcium carbonate precipitation sample from the bottom of the water permeable stone through the vacuum pump; and calculating the matrix suction force according to the microbial induced calcium carbonate precipitation samples with different saturations;

[0019] Rotating the rotating table to perform scanning at different angles to obtain gray scale images;

[0020] Drawing the soil water characteristic curve according to the matrix suction forces obtained under different saturations;

[0021] Taking out the microbial induced calcium carbonate precipitation sample from the sample mold to perform a macroscopic test.

[0022] Further, the saturation of the cemented sand column is controlled by adjusting the flow of the peristaltic pump and the negative pressure of the vacuum pump, the saturation of the cemented sand column is calculated by the flow of the peristaltic pump and the flow sensor, and the matrix suction of the cemented sand column under the saturation is obtained by reading the reading of the vacuum pressure gauge

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1、The present application can realize CT scanning of the microbial-induced calcium carbonate precipitation by setting the microbial-induced calcium carbonate precipitation sample in the transparent sample mold, and the microbial-induced calcium carbonate precipitation sample is located in the sample mold, avoiding cutting of the sand column and improving the test result; meanwhile, the flow sensor, the vacuum pressure gauge and the vacuum pump are arranged on the liquid outlet pipe, so that the matrix suction under different saturations can be calculated and controlled by controlling the bacteria liquid and the cementing liquid in the microbial-induced calcium carbonate precipitation sample, the CT image under different saturations and the soil water characteristic curve of the microbial-induced calcium carbonate precipitation sample can be obtained, and the test flexibility is improved.

[0025] 2、In the present application, the microbial-induced calcium carbonate precipitation sample can be taken out in the sample mold after the test, which is convenient for subsequent mechanical property test and mutual verification of the macroscopic and microscopic mechanism of the microbial-induced calcium carbonate precipitation; wherein the side wall of the sample mold comprises a plurality of acrylic plates fixed together through a fixing ring, the microbial-induced calcium carbonate precipitation sample is taken out by disassembling the plurality of acrylic plates, the test operation is simplified, and the integrity of the surface structure of the microbial-induced calcium carbonate precipitation sample is reserved.

[0026] 3、In the present application, the shell structure of the sample mold adopts a three-cuff membrane structure, which can be subjected to strength test after industrial CT scanning, and can be disassembled for other tests, such as calcium carbonate content analysis, without the need of loading, cutting and transferring the sample for scanning, so that the accuracy of the whole sample test is improved.

[0027] 4、The test device in the present application has small volume, saves materials, and is easy to assemble and move; and compared with the traditional equipment, the size of the sand sample is reduced, according to the CT scanning principle, the smaller the soil sample, the clearer the scanning image, so that the present application can obtain a clearer image after CT scanning compared with the traditional equipment.

[0028] 5、In the present application, a simple method and principle are adopted for experimental operation, for example, the saturation of the cemented sand column is controlled by adjusting the flow of the peristaltic pump and the negative pressure of the vacuum pump, the saturation of the cemented sand column is calculated by the flow of the peristaltic pump and the flow sensor, the matrix suction of the cemented sand column under the saturation is obtained by reading the reading of the vacuum pressure gauge, and finally the sample image under different saturations under CT scanning and the corresponding soil water characteristic curve are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings constituting a part of this embodiment are used to provide further understanding of the embodiment, the illustrative embodiment of the embodiment and its description are used to explain the embodiment, and do not constitute improper limitation on the embodiment.

[0030] Figure 1 It is a structural schematic diagram of the embodiment 1 of the application;

[0031] Figure 2 It is a CT scan schematic diagram of the embodiment 1 of the application.

[0032] Wherein, 1, liquid inlet pipe; 2, rubber plug; 3, sample mold; 4, fixing ring; 5, sample; 6, water-permeable stone; 7, valve; 8, liquid outlet pipe; 9, collection bottle; 10, vacuum pump; 11, peristaltic pump; 12, liquid inlet pipe; 13, geomembrane; 14, grouting hole; 15, liquid storage device; 16, base; 17, vacuum pressure gauge; 18, flow sensor; 19, ray source; 20, rotary table; 21, detection plate. DETAILED DESCRIPTION

[0033] The application will be further described below in combination with the drawings and embodiments.

[0034] With the development of economy, the demand for cement is also increasing, for a long time, cement as an important cementitious material, is widely used in civil construction, water conservancy and national defense engineering; and the high use of cement brings high carbon emission. At present, biotechnology has been widely used in environmental decontamination, detection and monitoring, which has promoted great progress of soil science; in geotechnical engineering application, most of the traditional soil improvement techniques consume a large amount of energy in production materials and on-site operation, which also causes potential danger to the environment (toxic chemicals, large amount of carbon dioxide emission); production of concrete is the main source of global anthropogenic carbon dioxide emission, about 6%. In order to expand the application range and pay attention to ecological problems, it has begun to find the most carbon footprint of sustainable biological source substitutes for ground improvement.

[0035] Microbial-induced calcite precipitation, usually by injecting urea bacteria and reagents (urea and calcium), uses biologically active precipitated calcium carbonate to cement sand, this technology has been used to enhance the mechanical properties of soil by using energy-saving microbial metabolic processes, compared with other traditional technologies, this technology can significantly reduce carbon emissions; the mass production of cement often brings a series of ecological and environmental problems such as excessive carbon dioxide emission, greenhouse effect, temperature rise, etc., therefore, the application of biotechnology in geotechnical field has important significance for reducing carbon emissions and protecting ecological environment.

[0036] At present, there are few studies on the combination of CT scanning technology and MICP technology. The inventor finds that the principle of traditional MICP technology is not reflected in the CT scanning process. The sand sample mold used in the test process is mostly a PVC pipe, which is difficult to demold and cannot be directly used in strength testing. The size of the sand column of the existing test instrument is too large, so even if CT scanning can be performed, a clear image cannot be obtained. The experimental sample for CT scanning is cut into small pieces from the whole sand column so that it can be placed in the industrial CT scanning room for scanning. This method will inevitably cause structural disturbance to the experimental sample during the cutting process of the sand column, thereby affecting the test results and reducing the test accuracy. In order to obtain better resolution and higher image accuracy, non-saturated granular soil or other granular materials such as sand (the particle size of clay is much smaller, resulting in more complex microstructure and poorer image resolution) are usually studied. In order to take advantage of the non-destructive detection and non-destructive detection of microstructure of CT scanning and promote the research on the cementation process of the MICP technology sand column, the existing test device needs to be improved and innovated.

[0037] Embodiment 1

[0038] As introduced in the background, the size of the sand sample of the existing test instrument is too large, so even if CT scanning can be performed, a clear image cannot be obtained. Moreover, the structure of the sample shell is relatively simple, and the subsequent strength test is difficult to perform. In order to solve the problems of CT scanning of microbial induced calcium carbonate precipitation, non-destructive detection and non-destructive detection of microstructure, the present embodiment provides a microbial induced calcium carbonate precipitation test device suitable for CT scanning, which comprises a liquid inlet pipe 1, a rubber plug 2, a sample mold 3, a fixing ring 4, a sample 5, a water-permeable stone 6, a valve 7, a liquid outlet pipe 8, a collection bottle 9, a vacuum pump 10, a peristaltic pump 11, a liquid inlet pipe 12, a geomembrane 13, a grouting hole 14, a liquid storage device 15, a base 16, a vacuum pressure gauge 17, a flow sensor 18, a radiation source 19, a rotating table 20 and a detection plate 21.

[0039] The sample mold 2 can be a transparent mold to provide the possibility of CT scanning. One end of the sample mold 2 is provided with a liquid inlet pipe 12, and the other end is provided with a liquid outlet pipe 8. It can be understood that the liquid inlet pipe 12 and the liquid outlet pipe 8 are both in communication with the sample mold 2, so as to realize the injection and exclusion of liquid such as bacterial liquid and cementing liquid. The liquid outlet pipe is provided with a flow sensor, a vacuum pressure gauge and a vacuum pump. By controlling the bacterial liquid and cementing liquid in the microbial induced calcium carbonate precipitation sample, the matrix suction under different saturations can be calculated and controlled, and the CT image and the soil water characteristic curve of the microbial induced calcium carbonate precipitation sample under different saturation conditions can be obtained, thereby improving the flexibility of the test.

[0040] The sample 5 is arranged in the sample mold 2; the sample 5 is a microbial-induced calcium carbonate precipitation sample, which can be understood as a cemented sand column; by arranging the microbial-induced calcium carbonate precipitation sample in the transparent sample mold, CT scanning of the microbial-induced calcium carbonate precipitation sample can be realized, and the microbial-induced calcium carbonate precipitation sample is arranged in the sample mold, thereby avoiding cutting of the sand column and improving the test result.

[0041] The sample mold 2 is used for accommodating the microbial-induced calcium carbonate precipitation sample, which can be understood as accepting things in a fixed space or range, and in the embodiment and the application, the microbial-induced calcium carbonate precipitation sample can be placed, arranged or filled in the fixed space in the sample mold 2; the microbial-induced calcium carbonate precipitation sample accommodated in the sample mold 2 can be a semi-finished product or a finished product of the sample.

[0042] The liquid inlet pipe 12 is provided with the peristaltic pump 11, and the liquid inlet pipe 12 is communicated with the liquid storage device 15 away from the sample mold 3; the liquid storage device 15 is filled with bacterial liquid and cementing liquid.

[0043] In the embodiment, the side wall of the sample mold 3 includes a plurality of acrylic plates fixed together through the fixing ring 4; specifically, the wall of the sample mold 3 can include an acrylic three-valve membrane, the inside of the valve membrane is provided with a space for accommodating the cemented sand column to be scanned, the middle part outside the valve membrane is fixed by the transparent acrylic fixing ring 4, and the cemented sand column is placed on the base 16 provided with the water-permeable stone 6; the acrylic three-valve membrane refers to three acrylic plates, the valve membrane means that each acrylic plate is arc-shaped, and the three arc-shaped acrylic plates can form a cylindrical sample mold after splicing; a connecting groove can be arranged at the connecting position of the three acrylic plates, and a sealing strip made of transparent flexible material can be arranged at the connecting groove; the fixing ring 4 can be provided as a ring-shaped buckle composed of two transparent half-round buckles hinged to each other, and a bolt hole can be arranged at the connecting position of the two half-round buckles, and the detachable connection can be realized by a conventional connecting mode such as a bolt; after the CT scanning test is completed, the fixing ring 4 can be disassembled, and the three arc-shaped acrylic plates are disassembled from all the samples 5, so that the samples 5 can be further observed.

[0044] The sample mold 3 can adopt the style of a traditional saturator, and is divided into three separate valve membranes, the height can be 76 mm, the inner diameter can be 38 mm, and the wall thickness can be 1 mm, which is used for storing sand samples, and then the fixing ring is used for fixing, so that subsequent disassembly for other indoor tests is facilitated; the water-permeable stone 6 can have a diameter of 38 mm.

[0045] In this embodiment, a rubber stopper 2 is provided at the opening of the sample mold 3, and a permeable stone 6 is provided at the lower end of the interior. A geomembrane 13 is provided between the rubber stopper 2 and the sample 5. The rubber stopper 2 can be made of flexible material with an opening in the middle. The liquid inlet pipe 12 passes through the middle opening and extends into a pre-set hole in the center of the sample 5. One end of the liquid inlet pipe 12 inside the sample mold 3 extends towards the center of the sample 5, and multiple uniform grouting holes 14 are opened on the liquid inlet pipe 12 located in the center of the sample 5. The permeable stone 6 is provided at the lower end of the interior of the sample mold 3. It can be understood that a liquid outlet pipe 8 is provided on the base 16 to connect to the permeable stone. A placement groove can be opened on the base 16 to place the sample mold 3 in the placement groove. In some other embodiments, the pipe that passes through the middle opening and extends into the pre-set hole in the center of the sample 5 can also be called a grouting pipe 1, and the grouting pipe is connected to the liquid inlet pipe 12.

[0046] The sample 5 can be pure silica sand, with a height of 71 mm and a diameter of 38 mm. The small sample size allows for higher resolution images obtained after CT scanning, clearly displaying the gas-liquid-solid three-phase state, facilitating better study of soil-water characteristic curves and further investigation of its permeability and strength. The sample 5 can have a uniform density of 1.61-1.63 g / L. 3 Made from pure silica sand, the X-ray source for industrial CT scanning can directly pass through to image the test sample. Because pure silica sand has no chemical interference with the bonding process, and using pure silica sand with appropriate porosity can make the bonding effect better, the CT image resolution is higher.

[0047] The outlet pipe 8 is also equipped with a valve 7, which is connected in sequence to the flow sensor 18, the vacuum pressure gauge 17, the vacuum pump 10 and the collection bottle 9.

[0048] The microbial-induced calcium carbonate precipitation test device suitable for CT scanning in this embodiment also includes a radiation source 19, a rotating stage 20, and a detector plate 21. The rotating stage 20 is disposed between the radiation source 19 and the detector plate 21. The radiation source 19 is a CT scanning device.

[0049] The working steps or working principle of this embodiment are as follows:

[0050] Specifically, the process of conducting the test using the morning MICP test apparatus is as follows:

[0051] A dry sand sample, namely the sample 5, is placed in the sample mold 3;

[0052] The sample mold 3 is placed on the base 16 with permeable stones 6 and fixed by the fixing ring 4;

[0053] Put the device into the CT scanning cabin, the pipeline on the device can be moved outside the instrument through the hole on the CT scanner, which is convenient for subsequent test operation;

[0054] Close the valve 7 on the liquid outlet pipe 8, open the peristaltic pump 11, and inject a volume V i of bacteria solution and cementing fluid into the valve through the grouting pipe 1, at this time the saturation S ri of the sample 5 is V i / (V-V s ), where V is the internal volume of the valve, V s is the volume of silica sand, which is determined by the classical experiment of soil mechanics by specific gravity bottle method;

[0055] Open the valve 7, start the vacuum pump 10, calculate the product of inflow rate Q 入 ×t 入 and inflow time of the peristaltic pump a1, and the product of outflow rate Q 出 ×t 出 and outflow time of the flow sensor 18, to obtain the volume V i of the solution in the sample 5, which is Q 入 ×t 入 -Q 出 ×t 出 ;

[0056] Extract the solution of the sand column by the vacuum pump 10 to keep the saturation S ri of the sample 5, read the value P i of the vacuum pressure gauge 17, which is the matrix suction u ai -u wi of the cemented sand column at this saturation;

[0057] Obtain the gray scale image under the saturation S ri by CT scanning, adjust the peristaltic pump 11 and the vacuum pump 10 to change the volume V i of the solution in the sample 5, draw the soil-water characteristic curve of the cemented sand column according to the corresponding matrix suction P i of different saturations S ri , and complete the test.

[0058] The device in the embodiment can be combined with CT scanning technology to better study the application of biotechnology in the field of geotechnical engineering. In view of the shortcomings of the existing device, such as large volume, metal shell, and inability to perform CT scanning, the device in the embodiment adopts a PMMA shell that can be subjected to CT scanning. The device size and sample size are relatively small, and the device can be placed in a CT scanner for scanning. The small sample size can obtain high-definition CT images after scanning. The device in the embodiment combines CT scanning technology to create good conditions for better studying the MICP cementation effect under different saturations and testing the strength and permeability of the sand sample. The indoor test performed by the device can provide a theoretical basis for the application of biotechnology in geotechnical engineering.

[0059] Embodiment 2:

[0060] A microbial-induced calcium carbonate precipitation test method suitable for CT scanning adopts the microbial-induced calcium carbonate precipitation test device suitable for CT scanning as described in the first aspect; the method comprises the following steps:

[0061] Placing the sample mold containing the microbial-induced calcium carbonate precipitation sample on the rotating table;

[0062] Aligning the irradiation direction of the ray source with the sample mold; injecting the bacterial solution and the cementing solution into the microbial-induced calcium carbonate precipitation sample through the peristaltic pump;

[0063] Extracting the liquid in the microbial-induced calcium carbonate precipitation sample from the bottom of the water-permeable stone by the vacuum pump; calculating the matrix suction according to the microbial-induced calcium carbonate precipitation samples with different saturations;

[0064] Rotating the rotating table, which can be rotated by 360 degrees, to obtain grayscale images by scanning at different angles;

[0065] Drawing the soil-water characteristic curve according to the matrix suction obtained under different saturations;

[0066] Removing the microbial-induced calcium carbonate precipitation sample from the sample mold to perform a macroscopic test.

[0067] In other embodiments, the following steps can also be included:

[0068] Placing the PMMA three-limb membrane on the base 16 provided with the water-permeable stone 6, placing the grouting pipe 1 and the sand column to be cemented in the membrane, covering the top with the geomembrane 13 and sealing it with the rubber plug 2 with a conduit, and assembling the MICP test device;

[0069] The part of the cemented sand column to be scanned is fixed on the rotating table 20 in the industrial CT scanning room; the saturation of the cemented sand column is controlled by adjusting the volume of the solution injected by the peristaltic pump 11 and the volume of the solution sucked by the vacuum pump 10, the saturation in the sand sample can be calculated according to the flow readings of the flow sensor 18 and the peristaltic pump 11, the value of the vacuum pressure gauge 17 is read to obtain the matrix suction of the cemented sand column at the saturation; CT scanning is performed at a certain saturation to obtain a sliced gray-scale image; the saturation of the cemented sand column is changed and the above steps are repeated to obtain the CT distribution image of gas-solid-liquid and the microbial reinforcement effect of the sand sample under different saturations, the soil water characteristic curve of the cemented sand column under different saturations is obtained through the corresponding matrix suction, and the cemented sand column can be taken out without damage through the valve after the test;

[0070] The process of obtaining the saturation and suction of the test sample is as follows: the dry sand sample is placed in the device valve, the valve 7 is closed, the peristaltic pump 11 is opened, a certain volume of bacterial solution and cementing solution is injected into the valve, when the saturation of the sand column reaches the predetermined value, the valve 17 is opened, the vacuum pump 10 is started, the excess solution is pumped out to keep the saturation of the sand column unchanged, the solution volume in the sand column is calculated by the flow of the flow sensor 18 and the peristaltic pump 11; the value of the vacuum pressure gauge 17 is read to obtain the matrix suction of the cemented sand column at the saturation.

[0071] The above only describes the preferred embodiments of the present embodiment and is not used to limit the present embodiment, and the present embodiment can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present embodiment shall be included in the protection scope of the present embodiment.

Claims

1. A microbial-induced calcium carbonate precipitation test device suitable for CT scans, characterized in that, The sample mold, which is transparent, is used to contain a microbially induced calcium carbonate precipitation sample. One end of the sample mold is provided with an inlet pipe, and the other end is provided with an outlet pipe. A flow sensor, a vacuum pressure gauge, and a vacuum pump are provided on the outlet pipe. The sidewall of the sample mold includes multiple acrylic plates fixed together by fixing rings. One end of the liquid inlet pipe extends into the middle of the sample mold, and multiple grouting holes are opened on the liquid inlet pipe located in the middle of the sample; bacterial solution and cementing solution are injected into the valve through the grouting pipe. A vacuum pump draws the sand column solution to maintain the saturation level within the sample at S. ri The reading on the vacuum pressure gauge represents the matrix suction of the cemented sand column at that saturation level. By using CT scanning, grayscale images under saturation condition Sri were obtained. The volume of solution in the sample was changed by adjusting the peristaltic pump and vacuum pump. The soil-water characteristic curves of cemented sand columns were plotted based on the matrix suction corresponding to different saturation Sri.

2. The microbial-induced calcium carbonate precipitation test device suitable for CT scanning as described in claim 1, characterized in that, A peristaltic pump is installed on the inlet pipe, and the end of the inlet pipe away from the sample mold is connected to a liquid storage device, which contains bacterial liquid and cementing liquid.

3. The microbial-induced calcium carbonate precipitation test device suitable for CT scanning as described in claim 1, characterized in that, A rubber stopper is provided at the opening of the sample mold, and a permeable stone is provided at the lower end of the interior; a geomembrane is provided between the rubber stopper and the sample.

4. The microbial-induced calcium carbonate precipitation test device suitable for CT scanning as described in claim 1, characterized in that, A valve is installed on the liquid outlet pipe.

5. The microbial-induced calcium carbonate precipitation test device suitable for CT scanning as described in claim 1, characterized in that, The end of the liquid outlet tube furthest from the sample mold is connected to a collection bottle.

6. The microbial-induced calcium carbonate precipitation test apparatus for CT scanning as described in claim 1, characterized in that, It also includes a radiation source, a rotating stage, and a detector plate, with the rotating stage positioned between the radiation source and the detector plate; the radiation source is a CT scanning device.

7. A method for microbial-induced calcium carbonate precipitation assay suitable for CT scans, characterized in that, The device used is a microbial-induced calcium carbonate precipitation test apparatus suitable for CT scanning as described in any one of claims 1-5; comprising: Place the sample mold containing the microbial-induced calcium carbonate precipitation sample on the rotating table; The radiation source is directed at the sample mold; a peristaltic pump is used to inject bacterial solution and cementing solution into the sample to induce calcium carbonate precipitation by microorganisms. A vacuum pump extracts the liquid from the bottom of the permeable stone sample containing microbial-induced calcium carbonate precipitation; the matrix suction is calculated based on microbial-induced calcium carbonate precipitation samples with different saturations. The rotary table rotates to scan at different angles to obtain grayscale images; Soil-water characteristic curves were plotted using the matrix suction obtained at different saturation levels. The microbial-induced calcium carbonate precipitation sample was removed from the sample mold and subjected to macroscopic testing.

8. The method for microbial-induced calcium carbonate precipitation assay suitable for CT scans as described in claim 7, characterized in that, The saturation of the cemented sand column is controlled by adjusting the flow rate of the peristaltic pump and the negative pressure of the vacuum pump. The saturation of the cemented sand column is calculated by the flow rate of the peristaltic pump and the flow sensor. The matrix suction of the cemented sand column at this saturation is obtained by reading the vacuum pressure gauge.

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