Variable-parameter microorganism circulating grouting device and method based on permeability coefficient

Abstract

The invention relates to the technical field of microbial engineering construction, in particular to a variable-parameter microbial circulating grouting device and method based on permeability coefficients, and the device comprises a grouting rack, a plurality of grouting cylinders, a permeability coefficient measuring device, a slurry recycling device and an auxiliary device; the method comprises the steps of component splicing and mounting, bacterial liquid culture, grouting reinforcement experiment, sample maintenance and mechanical test. According to the grouting device and method, the defects that disturbance is large and grouting materials are wasted in an existing MICP sample preparation technology can be overcome, the sampling disturbance is small, grout can be recycled, and grouting parameters can be adjusted in real time according to the change of the permeability coefficient of a sample. Therefore, the geotechnical sample which is good in uniformity, low in disturbance, high in economic benefit and capable of reasonably reflecting the influence of grouting parameters on the reinforcing strength is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of microbial engineering construction, and in particular to a variable parameter microbial circulation grouting device and method based on permeability coefficient. Background Art

[0002] In infrastructure construction, it is often necessary to modify soil that is not suitable for engineering construction to meet the requirements of modernization. Traditional soil reinforcement technologies include replacement, dynamic compaction, vibration and chemical grouting. These traditional methods are generally characterized by high energy consumption, high disturbance and high pollution, which do not meet the requirements of national ecological civilization construction. MICP (Microbial Induced Calcium Carbonate Precipitation) technology has received extensive attention in geotechnical engineering in recent years due to its advantages of being green, environmentally friendly and easy to operate. MICP technology uses microbial engineering to screen and domesticate urease-producing bacteria in nature (such as Bacillus subtilis, Bacillus licheniformis and Pasteurella sporogenes) as engineering bacteria. The bacteria decompose the added urea in the soil environment to produce carbonate anions that react with the added calcium ions to form calcium carbonate colloidal particles. The calcium carbonate colloidal particles are continuously accumulated in the pores of the soil along with the penetration of the slurry, and finally form a stable cementation between the sand particles, which improves the structure and stability of the soil to be reinforced, and significantly improves the engineering properties of the soil. In order to explore the influencing factors of MICP reinforcement technology and improve its overall effect, the reinforced area is usually sampled under specific grouting parameters.

[0003] However, strong disturbances during sampling may introduce large errors, affecting the objective analysis of the effects of various factors on reinforcement. In addition, the use of a single grouting parameter throughout the grouting process may also lead to significant waste of resources, so improvements are needed. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a variable parameter microbial circulation grouting device and method based on permeability coefficient.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A variable parameter microbial circulation grouting device based on permeability coefficient, comprising a grouting stand, a plurality of grouting cylinders, a permeability coefficient measuring device, a slurry recovery device and an auxiliary device;

[0007] The grouting cylinder is provided with soil;

[0008] The upper surface of the grouting stand is provided with a plurality of circular holes at equal intervals; semicircular clamps are provided on both sides of the upper ends of the circular holes, the semicircular clamps are fixedly connected to the upper surface of the grouting stand, and a plurality of grouting cylinders are respectively arranged in the plurality of circular holes, and the two sides of the grouting cylinders are respectively in conflict with the corresponding two semicircular clamps.

[0009] Compared with the prior art, the present application can effectively ensure the stability of the grouting cylinder after installation and facilitate the addition of soil therein. At the same time, the permeability coefficient measuring device can detect the permeability situation, and the slurry recovery device and auxiliary device can avoid permeation leakage and realize the function of classified recovery, thereby improving the quality and efficiency of the use of the device.

[0010] Preferably, the grouting cylinder is composed of two acrylic semi-cylinders that are in contact with each other, and water-stop tapes are applied to opposite sides of the two acrylic semi-cylinders.

[0011] Furthermore, the firmness of the grouting cylinder assembly can be ensured, and the water-stop tape can avoid leakage and make the connection between the two acrylic semi-cylinders more firmly.

[0012] Preferably, the permeability coefficient measuring device includes two water head sensors installed on the upper part and the middle part of the grouting cylinder, and the two water head sensors are commonly connected to a computer).

[0013] Furthermore, a pipette is used to transfer bacterial liquid of one times the pore volume (Vv) of the soil to be reinforced from the cultured bacterial liquid to the grouting cylinder, and the permeability coefficient measuring device is started. When the liquid level reaches the permeability coefficient device at the upper part (at a height of H1 from the grouting cylinder), the device will record the time (T1) at this time and transmit it to the computer. When the liquid level reaches the permeability coefficient device at the lower part (at a height of H2 from the grouting cylinder), the device will record the time (T2) at this time and transmit it to the computer.

[0014] Preferably, the slurry recovery device includes a plurality of liquid collecting funnels fixed at equal intervals on the bottom of the upper table of the grouting stand, the lower end of the liquid collecting funnel is connected to a guide pipe, the lower ends of the plurality of guide pipes are jointly penetrated by a liquid collecting barrel, and the plurality of liquid collecting funnels are respectively arranged at the lower ends of the plurality of circular holes.

[0015] Furthermore, the bacterial liquid will move downward through the nylon gauze and fall into the liquid collecting funnel, and the falling bacterial liquid can be collected into the liquid collecting bucket through the guide tube.

[0016] Preferably, the auxiliary device includes two annular fasteners sleeved on the upper and lower ends of the grouting cylinder, nylon gauze is laid in the circular hole, the grouting cylinder abuts against the upper end of the nylon gauze, and the soil body abuts against the upper end of the nylon gauze; the upper end of the soil body abuts against a buffer gasket.

[0017] Furthermore, the buffer pad can reduce the scouring effect of the slurry on the soil during grouting, which is helpful to obtain a smooth geotechnical test and reduce the test error of subsequent mechanical tests. At the same time, the nylon dense gauze uses a 100-mesh nylon mesh gauze.

[0018] Preferably, the liquid collecting barrels include a bacteria liquid collecting barrel, a urea liquid collecting barrel, a calcium chloride liquid collecting barrel and a waste liquid barrel.

[0019] Furthermore, the collection of different bacterial liquids can be achieved.

[0020] Preferably, the diameter of the circular hole is 40 mm, the inner diameter of the grouting cylinder is 40 mm, the outer diameter is 45 mm, and the height is 120 mm; the inner wall of the grouting cylinder is affixed with a PVC plastic sheet, and vaseline is provided on the inner wall of the grouting cylinder and both sides of the PVC plastic sheet.

[0021] Furthermore, it is possible to prepare according to the needs to ensure that the components can be used in precise coordination.

[0022] The present invention also proposes a test method for a variable parameter microbial circulation grouting device based on a permeability coefficient, which is applicable to the above-mentioned variable parameter microbial circulation grouting device based on a permeability coefficient, and comprises the following steps:

[0023] Step 1: The two semi-cylinders need to be fixed at the upper and lower ends with circular fasteners, the lower part needs to be sealed with nylon gauze, and waterproof tape is attached to the seams to form a complete grouting cylinder;

[0024] Step 2: Apply vaseline evenly on the inner wall of the grouting cylinder and both sides of the PVC plastic sheet, and place the PVC plastic sheet coated with vaseline in the cylinder in a manner close to the wall of the grouting cylinder;

[0025] Step 3: According to the specified dry density and moisture content, weigh the weight of a sand column of soil to be reinforced and mix it evenly with a certain amount of water. Then divide the soil into four layers and fill it into the grouting cylinder and compact it to the specified height. Then wrap it with plastic wrap and place it in a cool place for 24 hours to evenly distribute the moisture.

[0026] Step 4: Bacterial culture, urea solution preparation and calcium chloride solution preparation:

[0027] Step 4.1, according to different bacteria, different culture media are selected. Taking Pasteurella sporogenes as an example, 15g casein peptone, 5g soy peptone and 5g sodium chloride are weighed using a precision balance and put into a beaker, and 900mL deionized water is added, and the pH value of the solution is adjusted to 7.3. After stirring, the solution is placed in a high-temperature sterilizer for sterilization and dissolution of nutrients. After high-temperature sterilization, it is placed in a UV sterile operating table for irradiation for one hour and cooled to room temperature;

[0028] Step 4.2, weigh 20g of urea and dissolve it in 100mL of water, adjust the pH value of the solution to 7.3, and filter out impurities using a filter in a sterile operating table. After ultraviolet irradiation for one hour, add it to the culture medium and irradiate it for one hour. The liquid culture medium is ready;

[0029] Step 4.3, in a sterile operating table, use a pipette to extract the microbial strains and inoculate them into the prepared liquid culture medium, mix them evenly, seal them with kraft paper, and place them in a constant temperature oscillator for 24 hours; the microbial culture solution is prepared;

[0030] Step 4.4, weigh 60g urea into a beaker and add 1L deionized water, weigh 111g calcium chloride into a beaker and add 1L deionized water, and adjust the pH value of the solution to 7 respectively, and the cementing solution is prepared;

[0031] Step 5: Grouting reinforcement experiment:

[0032] Step 5.1, microbial grouting: before grouting, place the buffer pad on the top of the soil column to be reinforced, then use a pipette to transfer the bacterial solution of one times the pore volume (Vv) of the soil to be reinforced from the cultured bacterial solution to the grouting cylinder, start the permeability coefficient measuring device, when the liquid level reaches the permeability coefficient device at the upper part (at a height of H1 from the grouting cylinder), the device will record the time (T1) at this time and transmit it to the computer, when the liquid level reaches the permeability coefficient device at the lower part (at a height of H2 from the grouting cylinder), the device will record the time (T2) at this time and transmit it to the computer, the permeability coefficient can be calculated as follows:

[0033]

[0034] After the infiltration is completed, the bacterial solution in the liquid collection bucket is transferred back to the grouting cylinder and the permeability coefficient is measured. This process is repeated three times, and the average permeability coefficient of the three times is taken as the permeability coefficient of the bacterial solution. The slurry after three cycles is moved into the waste liquid bucket;

[0035] Step 5.2, urea grouting: pipette 1Vv of urea solution from the prepared urea solution and inject it into the grouting cylinder, repeat the relevant operations in step 5.1, and record the average permeability coefficient of the three times as the permeability coefficient of the urea solution;

[0036] Step 5.3, calcium chloride grouting: pipette 1Vv of calcium chloride solution from the prepared calcium chloride solution and inject it into the grouting cylinder, repeat the relevant operations in step 5.1, and record the average permeability coefficient of the three times as the permeability coefficient of the calcium chloride solution;

[0037] Step 5.4, permeability coefficient calculation: take the average of the permeability coefficient of the bacterial solution, the permeability coefficient of the urea solution and the permeability coefficient of the calcium chloride solution as the average permeability coefficient of this round of grouting;

[0038] Step 5.5, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.75, prepare 0.75 mol / L urea and calcium chloride solution, and use this concentration of urea and calcium chloride solution for grouting;

[0039] Step 5.6, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.5, prepare 0.5 mol / L urea and calcium chloride solution, and use this concentration of urea and calcium chloride solution for grouting;

[0040] Step 5.7, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.25, prepare 0.25 mol / L urea and calcium chloride solution, use the urea and calcium chloride solution of this concentration for grouting until it is impermeable, and the grouting process is completed;

[0041] Step 6, sample curing: remove the grouting cylinder from the grouting stand, put it into a constant temperature drying oven, and cure it at 60°C for 4 days. The sample preparation is completed;

[0042] Step 7: Mechanical test: Take out the cured specimens from the grouting cylinder and conduct unconfined compression test and triaxial compression test.

[0043] Compared with the prior art, the present application clearly describes the method and steps for conducting the experiment, which is convenient for the staff to operate according to the experimental method so as to obtain accurate test values, while also realizing the recovery and secondary utilization of the slurry.

[0044] The beneficial effects of the present invention are:

[0045] 1. Controlling the grouting parameters accordingly through the permeability coefficient helps to improve the uniformity and strength of the reinforced body;

[0046] 2. The three-phase grouting scheme is adopted to help improve the penetration capacity of the slurry in dense sand and fine sand;

[0047] 3. Using a sample cylinder for grouting helps reduce the disturbance to the soil during the sampling process, reduces experimental errors, and makes the analysis of the impact of grouting parameters on the sample more objective;

[0048] 4. Using a liquid collecting device to recycle and re-grout the slurry can help improve the utilization rate of raw materials and reduce waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0050] Figure 2 It is a grouting stand diagram of the present invention;

[0051] Figure 3 It is a diagram of a grouting stand with a clamp of the present invention;

[0052] Figure 4 It is a diagram of a grouting stand with a liquid collecting device of the present invention;

[0053] Figure 5 It is a diagram of a grouting stand with a sample preparation cylinder of the present invention;

[0054] Figure 6 is a flow chart of the implementation method of the present invention;

[0055] In the figure: 1 annular fastener, 2 buffer gasket, 3 nylon dense gauze, 4 grouting stand, 5 liquid collecting funnel, 6 guide pipe, 7 liquid collecting bucket, 8 semicircular clamp, 9 soil, 10 water head sensor, 11 grouting cylinder, 12 computer, 13 round hole. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0057] Reference Figure 1-5 A variable parameter microbial circulation grouting device based on permeability coefficient includes a grouting stand 4, a plurality of grouting cylinders 11, a permeability coefficient measuring device, a slurry recovery device and an auxiliary device.

[0058] Reference Figure 1-5 The grouting cylinder 11 is provided with a soil body 9, through which a permeability test can be carried out, so as to understand its permeability and select materials according to the test results; a plurality of circular holes 13 are evenly spaced on the upper surface of the grouting stand 4, and the diameter of the circular holes 13 is 40 mm; the inner diameter of the grouting cylinder 11 is 40 mm, the outer diameter is 45 mm, and the height is 120 mm; the grouting cylinder 11 is composed of two acrylic semi-cylinders that are in contact with each other, and the two acrylic semi-cylinders are pasted with Waterstop tape can effectively avoid infiltration. At the same time, through precise numerical settings, the inner hole of the grouting cylinder 11 and the circular hole 13 can be accurately aligned to facilitate the infiltration and falling of the bacterial liquid. Semicircular clamps 8 are provided on both sides of the upper end of the circular hole 13. The semicircular clamps 8 are fixedly connected to the upper surface of the grouting stand 4. Multiple grouting cylinders 11 are respectively arranged in multiple circular holes 13, and the two sides of the grouting cylinder 11 are respectively in conflict with the corresponding two semicircular clamps 8.

[0059] Reference Figure 1-5 The inner wall of the grouting cylinder 11 is covered with a PVC plastic sheet, and vaseline is provided on the inner wall of the grouting cylinder 11 and both sides of the PVC plastic sheet, which can fully ensure the tightness of the connection and the sealing effect, so that the bacterial liquid will only penetrate the soil 9, ensuring the accuracy of the penetration result.

[0060] Reference Figure 1-5 The permeability measuring device includes two water head sensors 10 installed at the upper and middle parts of the grouting cylinder 11, and the two water head sensors 10 are connected to a computer 12. A pipette is used to transfer a bacterial liquid with a pore volume (Vv) of one times the pore volume of the soil to be reinforced from the cultured bacterial liquid to the grouting cylinder 11, and the permeability measuring device is started. When the liquid level reaches the permeability device at the upper part (at a height of H1 from the grouting cylinder 11), the device will record the time (T1) at this time and transmit it to the computer 12. When the liquid level reaches the permeability device at the lower part (at a height of H2 from the grouting cylinder 11), the device will record the time (T2) at this time and transmit it to the computer 12.

[0061] Reference Figure 1-5 The slurry recovery device includes a plurality of liquid collecting funnels 5 fixed at equal intervals on the bottom of the upper table of the grouting stand 4. The lower end of the liquid collecting funnel 5 is connected to a guide tube 6. The lower ends of the plurality of guide tubes 6 are penetrated by a liquid collecting barrel 7, which can centrally recover the bacterial liquid. The liquid collecting barrel 7 includes a bacterial liquid collecting barrel, a urea collecting barrel, a calcium chloride collecting barrel and a waste liquid barrel. Through the arrangement of a plurality of collecting barrels, different bacterial liquids can be classified and collected for secondary utilization. The plurality of liquid collecting funnels 5 are respectively arranged at the lower ends of the plurality of circular holes 13, which can accurately recover the fallen infiltrated bacterial liquid.

[0062] Reference Figure 1-5 The auxiliary device includes two annular fasteners 1 sleeved on the upper and lower ends of the grouting cylinder 11, which can ensure the firmness of the grouting cylinder 11. Nylon dense gauze 3 is laid in the circular hole 13, which can facilitate the penetration of the bacterial liquid without causing the soil to penetrate. The grouting cylinder 11 is in contact with the upper end of the nylon dense gauze 3, and the soil 9 is in contact with the upper end of the nylon dense gauze 3; the upper end of the soil 9 is in contact with a buffer gasket 2, which can reduce the scouring effect of the slurry on the soil during grouting, help to obtain a smooth geotechnical test, reduce the test error of the subsequent mechanical test, help to make the soil 9 more solidified, and facilitate the adjustment of the test soil.

[0063] Reference Figure 6 The present invention also proposes a test method for a variable parameter microbial circulation grouting device based on a permeability coefficient, which is applicable to the above-mentioned variable parameter microbial circulation grouting device based on a permeability coefficient, and comprises the following steps:

[0064] Step 1: The two semi-cylinders need to be fixed at the upper and lower ends with circular fasteners 1, the lower part of which needs to be sealed with nylon gauze 3, and waterproof tape is attached to the seams to form a complete grouting cylinder 11;

[0065] Step 2, evenly apply vaseline on the inner wall of the grouting cylinder 11 and both sides of the PVC plastic sheet, and put the PVC plastic sheet coated with vaseline into the cylinder 11 in accordance with the wall of the grouting cylinder 11;

[0066] Step 3: According to the specified dry density and moisture content, weigh the weight of a sand column of the soil to be reinforced and mix it evenly with a certain amount of water, then divide the soil 9 into four layers and fill them into the grouting cylinder 11 and compact them to the specified height, then wrap them with plastic wrap and place them in a cool place for 24 hours to evenly distribute the moisture;

[0067] Step 4: Bacterial culture, urea solution preparation and calcium chloride solution preparation:

[0068] Step 4.1, according to different bacteria, different culture media are selected. Taking Pasteurella sporogenes as an example, 15g casein peptone, 5g soy peptone and 5g sodium chloride are weighed using a precision balance and put into a beaker, and 900mL deionized water is added, and the pH value of the solution is adjusted to 7.3. After stirring, the solution is placed in a high-temperature sterilizer for sterilization and dissolution of nutrients. After high-temperature sterilization, it is placed in a UV sterile operating table for irradiation for one hour and cooled to room temperature;

[0069] Step 4.2, weigh 20g of urea and dissolve it in 100mL of water, adjust the pH value of the solution to 7.3, and filter out impurities using a filter in a sterile operating table. After ultraviolet irradiation for one hour, add it to the culture medium and irradiate it for one hour. The liquid culture medium is ready;

[0070] Step 4.3, in a sterile operating table, use a pipette to extract the microbial strains and inoculate them into the prepared liquid culture medium, mix them evenly, seal them with kraft paper, and place them in a constant temperature oscillator for 24 hours; the microbial culture solution is prepared;

[0071] Step 4.4, weigh 60g urea into a beaker and add 1L deionized water, weigh 111g calcium chloride into a beaker and add 1L deionized water, and adjust the pH value of the solution to 7 respectively, and the cementing solution is prepared;

[0072] Step 5: Grouting reinforcement experiment:

[0073] Step 5.1, microbial grouting: before grouting, place the buffer pad 2 on the top of the soil column to be reinforced, then use a pipette to transfer the bacterial solution of one times the pore volume (Vv) of the soil to be reinforced from the cultured bacterial solution to the grouting cylinder 11, start the permeability coefficient measuring device, when the liquid level reaches the permeability coefficient device at the upper part (at a height of H1 from the grouting cylinder 11), the device will record the time (T1) at this time and transmit it to the computer 12, when the liquid level reaches the permeability coefficient device at the lower part (at a height of H2 from the grouting cylinder 11), the device will record the time T2 at this time and transmit it to the computer 12, the permeability coefficient can be calculated as follows:

[0074]

[0075] After the infiltration is completed, the bacterial liquid in the liquid collection bucket 7 is transferred back to the grouting cylinder 11 and the permeability coefficient is measured. This process is repeated three times in total, and the average permeability coefficient of the three times is taken as the permeability coefficient of the bacterial liquid, and the slurry after three cycles is moved into the waste liquid bucket;

[0076] Step 5.2, urea grouting: pipette 1Vv of urea solution from the prepared urea solution and inject it into the grouting cylinder 11, repeat the relevant operations of step 5.1, and record the average permeability coefficient of three times as the permeability coefficient of the urea solution;

[0077] Step 5.3, calcium chloride grouting: take 1Vv of calcium chloride solution from the prepared calcium chloride solution and inject it into the grouting cylinder 11, repeat the relevant operations of step 5.1, and record the average permeability coefficient of the three times as the permeability coefficient of the calcium chloride solution;

[0078] Step 5.4, permeability coefficient calculation: take the average of the permeability coefficient of the bacterial solution, the permeability coefficient of the urea solution and the permeability coefficient of the calcium chloride solution as the average permeability coefficient of this round of grouting;

[0079] Step 5.5, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.75, prepare 0.75 mol / L urea and calcium chloride solution, and use this concentration of urea and calcium chloride solution for grouting;

[0080] Step 5.6, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.5, prepare 0.5 mol / L urea and calcium chloride solution, and use this concentration of urea and calcium chloride solution for grouting;

[0081] Step 5.7, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.25, prepare 0.25 mol / L urea and calcium chloride solution, use the urea and calcium chloride solution of this concentration for grouting until it is impermeable, and the grouting process is completed;

[0082] Step 6, sample curing: remove the grouting cylinder 11 from the grouting stand 4, put it into a constant temperature drying oven, and cure it at 60° C. for 4 days. The sample preparation is completed;

[0083] Step 7, mechanical test: the cured sample is taken out from the grouting cylinder 11, and an unconfined compression test and a triaxial compression test are performed.

[0084] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A variable parameter microbial circulation grouting device based on permeability coefficient, comprising a grouting stand (4), a plurality of grouting cylinders (11), a permeability coefficient measuring device, a slurry recovery device and an auxiliary device; characterized in that: A soil body (9) is arranged in the grouting cylinder (11); The upper surface of the grouting stand (4) is provided with a plurality of circular holes (13) at equal intervals; semicircular clamps (8) are provided on both sides of the upper ends of the circular holes (13); the semicircular clamps (8) are fixedly connected to the upper surface of the grouting stand (4); a plurality of grouting cylinders (11) are respectively arranged in the plurality of circular holes (13); and the two sides of the grouting cylinders (11) are respectively in contact with the two corresponding semicircular clamps (8).

2. The variable parameter microbial circulation grouting device based on permeability coefficient according to claim 1 is characterized in that: The grouting cylinder (11) is composed of two acrylic semi-cylinders that are in contact with each other, and water-stop tapes are applied to the opposite sides of the two acrylic semi-cylinders.

3. The variable parameter microbial circulation grouting device based on permeability coefficient according to claim 1 is characterized in that: The permeability coefficient measuring device comprises two water head sensors (10) installed at the upper part and the middle part of the grouting cylinder (11), and the two water head sensors (10) are commonly connected to a computer (12).

4. The variable parameter microbial circulation grouting device based on permeability coefficient according to claim 1 is characterized in that: The slurry recovery device comprises a plurality of liquid collecting funnels (5) fixed at equal intervals on the bottom of the upper surface of the grouting stand (4); the lower end of the liquid collecting funnel (5) is connected to a guide tube (6); a liquid collecting bucket (7) is provided through the lower ends of the plurality of guide tubes (6); and the plurality of liquid collecting funnels (5) are respectively arranged at the lower ends of the plurality of circular holes (13).

5. The variable parameter microbial circulation grouting device based on permeability coefficient according to claim 1 is characterized in that: The auxiliary device comprises two annular fasteners (1) sleeved on the upper and lower ends of a grouting cylinder (11); a nylon gauze (3) is laid in the circular hole (13); the grouting cylinder (11) abuts against the upper end of the nylon gauze (3); the soil body (9) abuts against the upper end of the nylon gauze (3); and the upper end of the soil body (9) abuts against a buffer pad (2).

6. The variable parameter microbial circulation grouting device based on permeability coefficient according to claim 4 is characterized in that: The liquid collection barrel (7) comprises a bacterial liquid collection barrel, a urea liquid collection barrel, a calcium chloride liquid collection barrel and a waste liquid barrel.

7. The variable parameter microbial circulation grouting device based on permeability coefficient according to claim 1 is characterized in that: The diameter of the circular hole (13) is 40 mm, the inner diameter of the grouting cylinder (11) is 40 mm, the outer diameter is 45 mm, and the height is 120 mm; the inner wall of the grouting cylinder (11) is affixed with a PVC plastic sheet, and the inner wall of the grouting cylinder (11) and both sides of the PVC plastic sheet are provided with vaseline.

8. A test method for a variable parameter microbial circulation grouting device based on permeability coefficient, applicable to a variable parameter microbial circulation grouting device based on permeability coefficient according to claims 1 to 7, characterized in that: The following steps are involved: Step 1: The two semi-cylinders need to be fixed at the upper and lower ends with circular fasteners (1), the lower part of which needs to be sealed with nylon gauze (3), and waterproof tape is affixed to the joints to form a complete grouting cylinder (11); Step 2, evenly apply vaseline on the inner wall of the grouting cylinder (11) and both sides of the PVC plastic sheet, and place the PVC plastic sheet coated with vaseline in the grouting cylinder (11) in a manner that fits the wall of the grouting cylinder (11); Step 3, weighing the weight of a sand column of soil to be reinforced according to the specified dry density and moisture content and uniformly mixing it with a certain amount of water, then dividing the soil (9) into four layers and filling them into a grouting cylinder (11) and compacting them to a specified height, then wrapping them with plastic wrap and placing them in a cool place for 24 hours to allow the moisture to be evenly distributed; Step 4: Bacterial culture, urea solution preparation and calcium chloride solution preparation: Step 4.1, according to different bacteria, different culture media are selected. Taking Pasteurella sporogenes as an example, 15g casein peptone, 5g soy peptone and 5g sodium chloride are weighed using a precision balance and put into a beaker, and 900mL deionized water is added, and the pH value of the solution is adjusted to 7.

3. After stirring, the solution is placed in a high-temperature sterilizer for sterilization and dissolution of nutrients. After high-temperature sterilization, it is placed in a UV sterile operating table for irradiation for one hour and cooled to room temperature; Step 4.2, weigh 20g of urea and dissolve it in 100mL of water, adjust the pH value of the solution to 7.3, and filter out impurities using a filter in a sterile operating table. After ultraviolet irradiation for one hour, add it to the culture medium and irradiate it for one hour. The liquid culture medium is ready; Step 4.3, in a sterile operating table, use a pipette to extract the microbial strains and inoculate them into the prepared liquid culture medium, mix them evenly, seal them with kraft paper, and place them in a constant temperature oscillator for 24 hours; the microbial culture solution is prepared; Step 4.4, weigh 60g urea into a beaker and add 1L deionized water, weigh 111g calcium chloride into a beaker and add 1L deionized water, and adjust the pH value of the solution to 7 respectively, and the cementing solution is prepared; Step 5: Grouting reinforcement experiment: Step 5.1, microbial grouting: before grouting, place the buffer pad (2) on the top of the soil column to be reinforced, then use a pipette to transfer bacterial liquid of one times the pore volume (Vv) of the soil to be reinforced from the cultured bacterial liquid to the grouting cylinder (11), start the permeability coefficient measuring device, when the liquid level reaches the permeability coefficient device at the upper part (at a height of H1 from the grouting cylinder (11)), the device will record the time (T1) at this time and transmit it to the computer (12), when the liquid level reaches the permeability coefficient device at the lower part (at a height of H2 from the grouting cylinder (11)), the device will record the time (T2) at this time and transmit it to the computer (12), the permeability coefficient can be calculated according to the following formula: After the infiltration is completed, the bacterial liquid in the liquid collection bucket (7) is transferred back to the grouting cylinder (11) and the permeability coefficient is measured. This process is repeated three times in total, and the average permeability coefficient of the three times is taken as the permeability coefficient of the bacterial liquid, and the slurry after three cycles is moved into the waste liquid bucket; Step 5.2, urea grouting: pipette 1Vv of urea solution from the prepared urea solution and inject it into the grouting cylinder (11), repeat the relevant operations of step 5.1, and record the average permeability coefficient of the three times as the permeability coefficient of the urea solution; Step 5.3, calcium chloride grouting: take 1Vv of calcium chloride solution from the prepared calcium chloride solution and inject it into the grouting cylinder (11) and repeat the relevant operations of step 5.

1. The average permeability coefficient of the three times is recorded as the permeability coefficient of the calcium chloride solution; Step 5.4, permeability coefficient calculation: take the average of the permeability coefficient of the bacterial solution, the permeability coefficient of the urea solution and the permeability coefficient of the calcium chloride solution as the average permeability coefficient of this round of grouting; Step 5.5, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.75, prepare 0.75 mol / L urea and calcium chloride solution, and use this concentration of urea and calcium chloride solution for grouting; Step 5.6, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.5, prepare 0.5 mol / L urea and calcium chloride solution, and use this concentration of urea and calcium chloride solution for grouting; Step 5.7, repeat steps 5.1-5.4 until the permeability coefficient is reduced to the original 0.25, prepare 0.25 mol / L urea and calcium chloride solution, use the urea and calcium chloride solution of this concentration for grouting until it is impermeable, and the grouting process is completed; Step 6, sample curing: remove the grouting cylinder (11) from the grouting stand (4), put it into a constant temperature drying oven, and cure it at 60° C. for 4 days. The sample preparation is completed; Step 7, mechanical test: the cured sample is taken out from the grouting cylinder (11) and subjected to an unconfined compression test and a triaxial compression test.

Images