Testing device and method for solidifying sandy soil by inducing calcium carbonate precipitation through microorganisms

Abstract

The invention relates to the technical field of sandy soil solidification, and discloses a test device and method for solidifying sandy soil by inducing calcium carbonate precipitation through microorganisms, and the test device comprises a test mold, a gas conveying module, a vacuumizing module, a liquid adding module, a temperature control module and a monitoring module. Wherein an upper sealing cover and a lower sealing cover are respectively arranged at the upper end and the lower end of the test mold, a sand sample is arranged in the test mold, and a first space and a second space are respectively formed by the upper sealing cover, the lower sealing cover and the upper end and the lower end of the test mold. The activity of microorganisms is inhibited by controlling environmental factors such as temperature and air pressure in the injection process, inlet blockage caused by'first contact and first reaction 'is avoided, and meanwhile, a microorganism mixed liquid injection mode is optimized by adopting a comprehensive contact mode, so that the mixed liquid is in more sufficient contact with a sand sample, the injection time is shortened, and the nonuniformity of calcium carbonate generation is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of sand solidification, and in particular to an experimental device and method for microorganism-induced calcium carbonate precipitation solidification of sand. Background Art

[0002] Microbial soil stabilization is a relatively new research field in environmental geotechnical engineering in recent years. Its core technology is MICP (Microbially Induced Calcite Precipitation). Through the action of microorganisms, calcium sources such as urea are decomposed in a green and environmentally friendly way to form calcium carbonate precipitation between soil particles, thereby achieving the effect of soil stabilization and improving soil stiffness and strength.

[0003] The traditional MICP technology test uses a multi-phase multiple-pass method, and the "first contact, first reaction" makes the test device easy to be blocked at the sand sample entrance, and there are problems such as extremely uneven distribution of generated calcium carbonate, which makes the test results have certain deviations, thus affecting the research conclusions. At present, the difficult-to-control calcium carbonate uniformity problem and the technical application efficiency problem are the main factors limiting the application and promotion of MICP technology.

[0004] CN108761044A discloses an experimental device and method for microbial induced calcium carbonate precipitation and solidification of sand under negative pressure environment; CN108008110A discloses an optimization method for microbial solidification of sand based on temperature conditions. The above two patents mainly control a certain factor in the MICP technology solidification sand test process to solve the problem of calcium carbonate heterogeneity. The purpose is to improve the technical test effect. It does not specifically consider the complexity of the comprehensive effect of temperature, air pressure, and oxygen concentration in the gas environment on the technical effect of MICP technology in the actual engineering application process in different regions, and cannot provide a more intuitive and accurate reference basis for specific projects.

[0005] Therefore, in this relatively new research field of environmental geotechnical science, it is necessary to design an experimental device and method for microbial-induced calcium carbonate precipitation and solidification of sand based on multi-factor control of temperature, air pressure, and oxygen concentration to solve problems such as the uneven formation of calcium carbonate and enhance the scientific nature of the experiment. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an experimental device and method for microbial induced calcium carbonate precipitation and solidification of sand.

[0007] On the one hand, the present invention discloses a test device for microbial induced calcium carbonate precipitation and solidification of sandy soil, comprising:

[0008] A test mold, wherein an upper sealing cover and a lower sealing cover are respectively provided at the upper and lower ends of the test mold, a sand sample is contained in the test mold, and a first space and a second space are respectively formed between the upper sealing cover and the lower sealing cover and the upper and lower ends of the test mold;

[0009] A gas delivery module, the gas delivery module is used to adjust the oxygen concentration in the test mold;

[0010] A vacuum module, the vacuum module is used to adjust the vacuum degree in the test mold;

[0011] A liquid adding module, which is arranged above the test mold and is used to inject a microbial mixture required for the test into the test mold;

[0012] A temperature control module, the temperature control module is used to adjust the temperature of the test mold and the liquid adding module;

[0013] A monitoring module is connected to the gas delivery module, the vacuum module, the liquid adding module and the temperature control module, and is used to monitor the oxygen concentration, vacuum degree, temperature in the test mold and the temperature in the liquid adding module.

[0014] Preferably, the gas delivery module comprises a gas delivery pump and a gas delivery pipe with a valve, one end of the gas delivery pipe is connected to the gas delivery pump, and the other end passes through the upper sealing cover and is connected to the first space.

[0015] Preferably, the vacuum module comprises a vacuum pump and a gas pipe with a valve, one end of the gas pipe is connected to the vacuum pump, and the other end of the gas pipe passes through the lower sealing cover and is connected to the second space.

[0016] Preferably, the liquid adding module includes multiple liquid storage containers, a mixing liquid container with a mechanical stirring structure and a connecting pipe with a valve. The multiple liquid storage containers are connected to the mixing liquid container through branches, and the mixing liquid container is connected to the first space through the connecting pipe with a valve.

[0017] Preferably, each branch pipe is provided with a metering valve.

[0018] Preferably, the temperature control module includes a temperature control switch, a cooling / heating device and a temperature control circuit. The temperature control circuit is connected from the cooling / heating device and is respectively connected to the test mold and the liquid adding module. The temperature control switch is used to control the heating temperature of the cooling / heating device.

[0019] Preferably, the monitoring module includes a monitoring data output display terminal, a transmission line and a monitoring sensing element, the monitoring sensing element is used to monitor the oxygen concentration, vacuum degree, temperature in the test mold and the temperature in the liquid adding module, the monitoring data output display terminal is connected to the monitoring sensing element through the transmission line, and the monitoring data output display terminal is used to display the oxygen concentration data, vacuum degree data, temperature data in the test mold and the temperature data in the liquid adding module.

[0020] Preferably, the sand sample is sealed by geotextile.

[0021] Preferably, a residual liquid recovery hole is provided at the bottom of the lower sealing cover, and a liquid outlet pipe with a valve is connected to the residual liquid recovery hole.

[0022] On the other hand, the present invention also discloses a test method for microbial induced calcium carbonate precipitation and solidification of sandy soil, comprising the following steps:

[0023] S1: Collect enough sand and soil samples on site, and collect the local temperature and oxygen concentration index in the gas environment; by analyzing the mineral components in the sand and soil samples, preliminarily determine the raw material ratio of the injected microbial mixture;

[0024] S2: placing the sand sample into a test mold, and installing an upper sealing cover and a lower sealing cover to seal the test mold;

[0025] S3: Prepare the microbial mixed solution through the liquid adding module according to the test requirements and keep it for use;

[0026] S4: vacuuming the environment of the test mold through the vacuuming module, and adding the microbial mixed liquid to the test mold through the liquid adding module under negative pressure;

[0027] S5: According to the local temperature and the oxygen concentration index in the gas environment, the temperature and oxygen concentration in the test mold are regulated by the temperature control module and the gas delivery module, so that the microorganisms solidify the sand sample;

[0028] S6: Repeat steps S3-S5 to explore the effects of different temperatures, oxygen concentrations, vacuum degrees, and microbial mixtures with different raw material ratios on the solidification of the sand sample.

[0029] The experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil of the present invention has the advantages that:

[0030] (1) The test device and method inhibit the activity of microorganisms by controlling environmental factors such as temperature and air pressure during the injection process, avoiding blockage of the entrance due to "first contact, first reaction", and at the same time optimizing the injection method of the microbial mixture by a comprehensive contact method, so that the mixture can contact the sand sample more fully, shorten the injection time, and reduce the unevenness of calcium carbonate generation; (2) The method embodies the idea of ​​unified regulation of the test environment such as temperature, oxygen concentration, and the ratio of reaction liquid to microorganisms, improves the operability and scientificity of the test process, reduces the test cost, shortens the test cycle, and provides more accurate technical indicators for the engineering application of MICP technology, creating economic benefits; (3) The method provides a standardized control test process for indoor tests of MICP technology before actual engineering applications. By conducting indoor comparisons and repeated tests that simulate the actual environmental conditions of the project, the optimal MICP technology test parameters that match its engineering environment are obtained, promoting the development of MICP technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of an experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil according to the present invention.

[0032] Description of reference numerals:

[0033] 1 test mold, 11 upper sealing cover, 12 lower sealing cover, 121 liquid outlet pipe, 101 first space, 102 second space;

[0034] 2 gas delivery module, 21 gas delivery pump, 22 gas delivery pipe;

[0035] 3 vacuum module, 31 vacuum pump, 32 gas pipe;

[0036] 4 liquid adding module, 41 liquid storage container, 42 liquid mixing container, 43 connecting pipe;

[0037] 5 temperature control modules, 6 monitoring modules. DETAILED DESCRIPTION

[0038] Example 1

[0039] like Figure 1As shown, this embodiment discloses a test device for microbial induced calcium carbonate precipitation and solidification of sand, including a test mold 1, a gas delivery module 2, a vacuum module 3, a liquid adding module 4, a temperature control module 5 and a monitoring module 6. Among them, the upper and lower ends of the test mold 1 are respectively provided with an upper sealing cover 11 and a lower sealing cover 12, and the test mold 1 is filled with a sand sample. The upper sealing cover 11 and the lower sealing cover 12 and the upper and lower ends of the test mold 1 form a first space 101 and a second space 102 respectively. The main function of the first space 101 formed by the upper sealing cover 11 is to enable the mixed liquid to fully and comprehensively contact with the upper surface of the sand sample during the injection of the mixed liquid, accelerate the injection rate of the mixed liquid, and make the mixed liquid more uniformly injected. The second space 102 can judge whether the mixed liquid is injected completely and fully.

[0040] The gas delivery module 2 is used to adjust the oxygen concentration in the test mold 1. Specifically, the gas delivery module 2 provides the test mold 1 with the function of regulating the oxygen concentration during the reaction process, and the temperature of the gas is monitored and regulated by the monitoring module 6 and the temperature control module 5.

[0041] The vacuum module 3 is used to adjust the vacuum degree in the test mold 1. Specifically, the vacuum module 3 provides the test mold 1 with a vacuum degree control function during the process of injecting liquid such as microbial mixture into the sand sample.

[0042] The liquid adding module 4 is arranged above the test mold 1, and is used to inject the microbial mixture required for the test into the test mold 1. Specifically, the liquid adding module 4 is the main preparation container of microbial mixtures such as microbial suspensions and nutrient solutions, and the container has volume measurement and mechanical stirring functions, and its internal temperature is monitored and regulated by the above-mentioned monitoring module 6 and temperature control module 5.

[0043] The temperature control module 5 is used to adjust the temperature in the test mold 1 and the liquid adding module 4. The monitoring module 6 is connected to the gas delivery module 2, the vacuum module 3, the liquid adding module 4 and the temperature control module 5, and is used to monitor the oxygen concentration, vacuum degree, temperature in the test mold 1 and the temperature in the liquid adding module 4.

[0044] In the specific test, the sand sample is loaded into the test mold 1, and then the upper sealing cover 11 and the lower sealing cover 12 are used to seal the test mold 1, and then the microbial mixture required for the test is configured through the liquid adding device 4. The microbial mixture is 5g / L soybean peptone, 3g / L meat peptone, 20.0g / L CO(NH2)2, 20g / L yeast extract, and 10g / L (NH4)2SO4. Then, the vacuum module 3 is started to vacuum the equipment to -0.06MPa~-0.08MPa, and the microbial mixture is injected into the test mold 1 through the liquid adding module 4 under negative pressure conditions. After the injection of the mixture, the temperature and oxygen concentration in the test mold 1 are adjusted according to the test requirements through the gas delivery module 2 and the temperature control module 5, so that the microbial mixture solidifies the sand sample under the conditions of the temperature and oxygen concentration specified in the test. During the entire experimental process, the solidification oxygen concentration and temperature can be changed through the gas delivery module 2 and the temperature control module 5, and repeated comparative tests can be performed. This embodiment suppresses the activity of microorganisms by controlling environmental factors such as temperature and air pressure during the injection process to avoid blockage of the entrance due to "first contact, first reaction". At the same time, a comprehensive contact method is adopted to optimize the injection method of the microbial mixed solution, so that the mixed solution can contact the sand sample more fully, shorten the injection time, and reduce the unevenness of calcium carbonate generation.

[0045] In this embodiment, the test mold 1 is the main container for the test reaction. The container should be convenient for loading and removing sand and soil samples, as well as the injection and extraction of liquids such as microbial mixtures and gases such as oxygen. Its internal temperature, vacuum degree and oxygen concentration are monitored and regulated by the above-mentioned monitoring module 6, temperature control module 5, vacuum module 3 and gas delivery module 2. The specifications and dimensions of the test mold 1 can be customized according to specific test specifications.

[0046] Preferably, the gas delivery module 2 includes a gas delivery pump 21 and a gas delivery pipe 22 with a valve, one end of the gas delivery pipe 22 is connected to the gas delivery pump 21, and the other end passes through the upper sealing cover 11 and is connected to the first space 101. When it is necessary to adjust the oxygen concentration inside the test mold 1, oxygen can be delivered by the gas delivery pump 21, thereby adjusting the oxygen concentration inside the test mold 1. The monitoring module 6 can detect the oxygen concentration in the test mold 1. After the oxygen concentration reaches the test requirement, the valve on the gas delivery pipe 22 is closed, and the valve can be a solenoid valve.

[0047] Preferably, the vacuum module 3 includes a vacuum pump 31 and a gas pipe 32 with a valve, one end of the gas pipe 32 is connected to the vacuum pump 31, and the other end passes through the lower sealing cover 12 and is connected to the second space 102. When the test mold 1 needs to be vacuumed, the space in the test mold 1 is vacuumed by the vacuum pump 31, and the vacuum degree in the test mold 1 is monitored by the monitoring module 6. When the vacuum degree reaches the test requirement, the valve on the gas pipe 32 is closed, and the valve can also be a solenoid valve.

[0048] Preferably, the liquid adding module 4 includes a plurality of liquid storage containers 41, a liquid mixing container 42 with a mechanical stirring structure, and a connecting pipe 43 with a valve. The plurality of liquid storage containers 41 are connected to the liquid mixing container 42 through a branch pipe, and the liquid mixing container 42 is connected to the first space 101 through a connecting pipe 43 with a valve. Each liquid storage container 41 can be equipped with various raw materials required for the microbial mixed liquid, and then injected into the liquid mixing container 42, and the microbial mixed liquid is stirred by the mechanical stirring structure to mix the microbial mixed liquid, and then the microbial mixed liquid is injected into the first space 101 through the connecting pipe 43, and then passes through the sand sample, and then solidifies the sand sample. In addition, a metering valve is provided on each branch pipe, and the metering valve can control the amount of each raw material added in the liquid storage container 41, so as to facilitate different tests.

[0049] Preferably, the temperature control module 5 includes a temperature control switch, a cooling / heating device and a temperature control circuit. The temperature control circuit is connected from the cooling / heating device and is respectively connected to the test mold 1 and the liquid adding module 4. The temperature control switch is used to control the heating temperature of the cooling / heating device. The cooling / heating device heats or cools the test mold 1. The cooling / heating device is specifically connected to the liquid mixing container 42 of the liquid adding module 4 to heat the mixed solution in the liquid mixing container 42, thereby controlling the adding temperature of the mixed solution.

[0050] Preferably, the monitoring module 6 includes a monitoring data output display terminal, a transmission line and a monitoring sensing element. The monitoring sensing element is used to monitor the oxygen concentration, vacuum degree, temperature in the test mold 1 and the temperature in the liquid adding module 4. The monitoring data output display terminal is connected to the monitoring sensing element through the transmission line. The monitoring data output display terminal is used to display the oxygen concentration data, vacuum degree data, temperature data in the test mold 1 and the temperature data in the liquid adding module 4. The monitoring sensing element includes a temperature sensing element, an oxygen concentration detection element and an air pressure detection element. There are multiple temperature sensing elements, one part of which is distributed in the test mold 1 and the other part is distributed in the mixed liquid container 42. The temperature sensing element is connected to the monitoring data output display terminal through the transmission line. The monitoring data output display terminal displays the temperature of the test mold 1 and the microorganism mixed liquid, which is convenient for the test personnel to observe the test data. The oxygen concentration detection element is arranged in the gas delivery module 2 to monitor the oxygen supply, and the air pressure detection element is connected to the vacuum module 3 to monitor the vacuum degree.

[0051] Preferably, the sand sample is sealed by a geotextile, which mainly plays the role of water permeability and air permeability. At the same time, during the air extraction process, the sand particles in the test mold 1 are not drawn out of the mold, thereby enhancing its stability. A residual liquid recovery hole is provided at the bottom of the lower sealing cover 12, and a liquid outlet pipe 121 with a valve is connected to the residual liquid recovery hole to facilitate the recovery of the residual mixed liquid after the reaction.

[0052] Example 2

[0053] On the other hand, this embodiment also discloses an experimental method for microbial induced calcium carbonate precipitation and solidification of sand, comprising the following steps.

[0054] Preparation: Collect enough sand and soil samples on site, and collect the local temperature and oxygen concentration indicators in the gas environment; by analyzing the mineral components in the sand and soil samples, preliminarily determine the raw material ratio of the injected microbial mixture.

[0055] Start the test: Customize a certain number of test molds 1 of corresponding sizes according to the requirements of the subsequent test size, and make sand samples. Put the sand samples into the test mold 1, and install the upper sealing cover 11 and the lower sealing cover 12 to seal the test mold 1.

[0056] According to the test requirements, the microbial mixed solution is prepared by the liquid adding module 4 for standby use. Specifically, the temperature of the liquid adding module is adjusted to 4° C., and the mixed solution is prepared according to the raw material ratio of the microbial mixed solution to be injected preliminarily determined in the preparation work, and mechanically stirred for standby use.

[0057] Under the temperature condition of 4°C, the environment of the test mold 1 is evacuated through the vacuum module 3, and under the negative pressure environment, the microbial mixed liquid is added to the test mold 1 through the liquid adding module 4, and the injection is completed. According to the local temperature and the oxygen concentration index in the gas environment, the temperature and oxygen concentration in the test mold 1 are regulated by the temperature control module 5 and the gas delivery module 2, so that the microorganisms solidify the sand sample. After sufficient reaction, the residual mixed liquid in the test mold 1 is recovered, and all the sand samples are taken out.

[0058] Prepare microbial mixtures with different raw material ratios, repeat steps S4-S5, and explore the effects of different temperatures, oxygen concentrations, microbial mixtures, and vacuum degrees on the solidification of sand samples.

[0059] Specifically, the temperature is changed every 2 degrees Celsius above and below the actual project temperature. If the actual project temperature is 25°C, then 21°C, 23°C, 27°C and 29°C are set for testing. The test group is designed every 1% within the preset oxygen concentration range. If the oxygen concentration is between 19.5% and 23.5%, then 19.5, 20.5, 21.5, 22.5 and 23.5% are set.

[0060] Subsequent testing and analysis: By conducting triaxial compression tests and other tests on sand samples and testing the residual mixed liquid, key information required for engineering construction, such as the uniaxial compressive strength of the sand samples and the test results of the residual mixed liquid, is obtained to analyze whether the engineering application needs are met. If so, the test results data is submitted and the test is successfully completed; if not, the test reaction conditions are adjusted according to the actual situation and the test is repeated, or the construction method is adjusted. The mechanical properties of the solidified sand sample are explored through triaxial compression tests and then uniaxial compressive strength tests. Secondly, the test of the mixture is to analyze the components of the residual mixed liquid and then explore the formation of calcium carbonate.

[0061] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention.

[0062] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A test device for microbial induced calcium carbonate precipitation and solidification of sandy soil, characterized in that: include: A test mold (1), wherein an upper sealing cover (11) and a lower sealing cover (12) are respectively arranged at the upper and lower ends of the test mold (1), a sand sample is contained in the test mold (1), and a first space (101) and a second space (102) are respectively formed between the upper and lower ends of the test mold (1) and the lower sealing cover (12); A gas delivery module (2), the gas delivery module (2) being used to adjust the oxygen concentration in the test mold (1); A vacuum module (3), the vacuum module (3) being used to adjust the vacuum degree in the test mold (1); A liquid adding module (4), the liquid adding module (4) being arranged above the test mold (1) and being used for injecting a microbial mixture required for the test into the test mold (1); A temperature control module (5), the temperature control module (5) being used to adjust the temperature inside the test mold (1) and the liquid adding module (4); A monitoring module (6), wherein the monitoring module (6) is connected to the gas delivery module (2), the vacuum module (3), the liquid adding module (4) and the temperature control module (5), and is used to monitor the oxygen concentration, vacuum degree, temperature in the test mold (1) and the temperature in the liquid adding module (4).

2. The experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil according to claim 1, characterized in that: The gas delivery module (2) comprises a gas delivery pump (21) and a gas delivery pipe (22) with a valve, wherein one end of the gas delivery pipe (22) is connected to the gas delivery pump (21), and the other end passes through the upper sealing cover (11) and is connected to the first space (101).

3. The experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil according to claim 2, characterized in that: The vacuum module (3) comprises a vacuum pump (31) and a gas pipe (32) with a valve, one end of the gas pipe (32) being in communication with the vacuum pump (31), and the other end of the gas pipe (32) passing through the lower sealing cover (12) and in communication with the second space (102).

4. The experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil according to claim 3, characterized in that: The liquid adding module (4) comprises a plurality of liquid storage containers (41), a liquid mixing container (42) with a mechanical stirring structure, and a connecting pipe (43) with a valve. The plurality of liquid storage containers (41) are connected to the liquid mixing container (42) via a branch pipe, and the liquid mixing container (42) is connected to the first space (101) via the connecting pipe (43) with a valve.

5. The experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil according to claim 4, characterized in that: Each branch pipe is provided with a metering valve.

6. The experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil according to claim 4, characterized in that: The temperature control module (5) comprises a temperature control switch, a cooling / heating device and a temperature control circuit. The temperature control circuit is connected from the cooling / heating device and is respectively connected to the test mold (1) and the liquid adding module (4). The temperature control switch is used to control the heating temperature of the cooling / heating device.

7. The experimental device for microbial induced calcium carbonate precipitation and solidification of sandy soil according to claim 6, characterized in that: The monitoring module (6) comprises a monitoring data output display terminal, a transmission line and a monitoring sensing element, wherein the monitoring sensing element is used to monitor the oxygen concentration, vacuum degree and temperature in the test mold (1) and the temperature in the liquid adding module (4), and the monitoring data output display terminal is connected to the monitoring sensing element via the transmission line, and the monitoring data output display terminal is used to display the oxygen concentration data, vacuum degree data and temperature data in the test mold (1) and the temperature data in the liquid adding module (4).

8. The experimental device for microbial induced calcium carbonate precipitation and solidification of sand according to any one of claims 1 to 7, characterized in that: The sand sample was sealed by geotextile.

9. The experimental device for microbial induced calcium carbonate precipitation and solidification of sand according to any one of claims 1 to 7, characterized in that: A residual liquid recovery hole is provided at the bottom of the lower sealing cover (12), and a liquid outlet pipe (121) with a valve is connected to the residual liquid recovery hole.

10. An experimental method for microbial induced calcium carbonate precipitation and solidification of sandy soil, characterized in that: The following steps are involved: S1: Collect enough sand and soil samples on site, and collect the local temperature and oxygen concentration index in the gas environment; by analyzing the mineral components in the sand and soil samples, preliminarily determine the raw material ratio of the injected microbial mixture; S2: placing the sand sample into the test mold (1), and installing an upper sealing cover (11) and a lower sealing cover (12) to seal the test mold (1); S3: preparing a microbial mixed solution through a liquid adding module (4) according to the test requirements for standby use; S4: vacuuming the environment of the test mold (1) through the vacuuming module (3), and adding the microbial mixed liquid into the test mold (1) through the liquid adding module (4) under negative pressure; S5: According to the local temperature and oxygen concentration index in the gas environment, the temperature and oxygen concentration in the test mold (1) are regulated by the temperature control module (5) and the gas delivery module (2) so that the microorganisms solidify the sand sample; S6: preparing microbial mixed solutions with different raw material ratios, repeating steps S4-S5, and exploring the effects of different temperatures, oxygen concentrations, microbial mixed solutions, and vacuum degrees on the solidification of the sand sample.

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