Testing device for reinforcing underwater sandy soil based on EICP technology and using method

Abstract

The invention relates to a test device for reinforcing underwater sandy soil based on EICP technology, which comprises an uncovered test box body, the interior of the test box body is divided into a left water storage cavity, a middle grouting cavity and a right water storage cavity along the long edge, the right water storage cavity and the middle grouting cavity are separated by porous steel plates and soil retaining gauze, and the left water storage cavity and the middle grouting cavity are separated by porous steel plates and soil retaining gauze. A grouting pipe, a slurry pumping pipe, an embedded pipe and an ERT measuring line are arranged in the middle grouting cavity. A porous steel plate is adopted in the model to allow water to flow and fully simulate the saturated water environment, and the defect that a traditional model cannot simulate the saturated water environment is overcome. The model can better simulate the real condition of the sandy soil below the underground water level in engineering practice. The ion concentration, pH and conductivity of different parts in the grouting process can be measured through the embedded pipe; and preliminarily judging the generation amount of calcium carbonate at different parts and the reinforcing uniformity through the measured data. The innovation of the model provides an effective test device for the research of reinforcing underwater sandy soil by the EICP technology.

Description

Technical Field

[0001] The invention relates to a test device for reinforcing underwater sand based on EICP technology and a use method thereof. Background Art

[0002] Most of the land in my country needs to be improved and reinforced before it can be used for engineering construction. If the land is not improved and reinforced, it will easily cause various engineering problems under the action of external loads, such as foundation settlement, slope instability, floating of underground pipelines and tunnels, coastal or riverbank erosion and other related engineering disasters.

[0003] At present, common foundation treatment methods include dynamic tamping, replacement cushion method, pile foundation method, grouting method, composite foundation, etc. The replacement method is mostly used in soft foundations, and the treatment depth generally does not exceed 5m; the dynamic tamping method is affected by the regional topography; the compaction method is difficult to pile, and the settlement requires long-term monitoring; the common methods of grouting are pressure grouting, filling and sealing, and surface treatment. Traditional grouting methods have certain disadvantages. This type of chemical cementitious material has poor adhesion with cement-based materials, poor durability, easy aging, complex process, and high repair cost.

[0004] The bio-enzyme-induced calcium carbonate precipitation mineralization technology has been studied by a large number of scholars because of its advantages of green environmental protection, ecology, and sustainability. At present, there are two main technologies for inducing calcium carbonate precipitation through urea hydrolysis, one is microbially induced calcium carbonate precipitation technology (Microbially Induced Calcite Precipitation), referred to as MICP technology; the other is enzyme induced calcium carbonate precipitation technology (Enzyme Induced Calcite Precipitation), referred to as EICP technology. At present, a large number of scholars at home and abroad have conducted research on MICP technology. MICP can be used to enhance the mechanical properties of soil such as strength, stiffness, erosion resistance, impermeability, and liquefaction resistance. MICP technology can also be used for dust prevention, plugging, crack repair, slope reinforcement, etc.

[0005] Although the bio-enzyme-induced calcium carbonate precipitation mineralization technology has made some progress, most of the related research is in the laboratory, and there are relatively few cases of applying this technology to engineering practice. In recent years, relevant scholars at home and abroad have carried out large-scale solidification research. These studies are different from laboratory centimeter-level experiments but are based on meter-level units, providing theoretical support for further application in engineering practice. At present, there are some reports on experimental research on MICP technology to strengthen large-scale, but there are few reports on the use of EICP to strengthen large-scale, especially in saturated water environment. In addition, most of the current MICP reinforcement model equipment has a simple structure and cannot meet the requirements of simulating underwater environment. At the same time, it cannot simulate the diffusion and reaction of ions in underwater environment, and the method of evaluating reinforcement effect is single, which cannot meet the experimental requirements. The lack of model equipment restricts the research on strengthening large-scale soil with bio-enzyme-induced calcium carbonate precipitation mineralization technology.

[0006] In view of the above problems, the present invention designs a test device and a method for using the EICP technology to reinforce underwater sand. The device can fully simulate the underwater environment and control the grouting parameters. During the grouting reaction, the ion concentration in the water environment and the diffusion path of the ions can be detected, so the approximate distribution area of ​​calcium carbonate in the soil can be predicted. The test device is simple and easy to operate, which is of great significance for conducting relevant experimental research on EICP underwater reinforcement of large-size sand. Summary of the invention

[0007] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a test device and a method for using the EICP technology to reinforce underwater sand.

[0008] In order to solve the above technical problems, the technical solution of the present invention is: a test device for reinforcing underwater sand based on EICP technology, comprising an uncovered test box, the interior of the test box is separated into a left water storage chamber, a middle grouting chamber, and a right water storage chamber along the long side, the right water storage chamber and the middle grouting chamber, and the left water storage chamber and the middle grouting chamber are separated by porous steel plates and retaining gauze, and the middle grouting chamber is provided with a grouting pipe, a grouting pipe, an embedded pipe, and an ERT measuring line.

[0009] Preferably, there are four grouting pipes which are vertically arranged around the soil to be reinforced in the middle grouting cavity.

[0010] Preferably, the grouting pipe is vertically arranged in the middle position of the soil to be reinforced in the middle grouting cavity.

[0011] Preferably, the ERT measuring lines are divided into three and arranged on the soil surface of the middle grouting cavity, and each line is arranged with 60 high-density resistance electrodes.

[0012] Preferably, the grouting pipe is connected to the grouting equipment, and the grouting equipment includes a binder liquid barrel and a urease solution barrel, the binder liquid barrel and the urease solution barrel are respectively connected to the two inlets of the tee pipe via a suction hose, and the outlet of the tee pipe is then connected to the grouting pipe via a delivery hose.

[0013] Preferably, the suction hose is provided with a suction pump and a filter, and the delivery hose connected to each grouting pipe is provided with a flow meter and a pressure gauge.

[0014] Preferably, the slurry extraction pipe is connected to a slurry extraction device, and the slurry extraction device comprises a waste liquid barrel, a waste liquid hose is connected between the waste liquid barrel and the slurry extraction pipe, and a suction pump is arranged on the waste liquid hose.

[0015] Preferably, the grouting pipes are composed of an inner grouting pipe and an outer grouting pipe, and a plurality of grouting holes are vertically arranged on the periphery of the inner grouting pipe and the outer grouting pipe, and the inner grouting pipe is coaxially inserted inside the outer grouting pipe, the position of the outer grouting pipe is fixed, and the inner grouting pipe is connected to the grouting equipment.

[0016] Preferably, there are multiple pre-buried pipes, and the horizontal positions and depths of the multiple pre-buried pipes are different.

[0017] A method for using a test device for reinforcing underwater sand based on EICP technology comprises the following steps: S1. Preliminary preparation for the test: including laying of retaining gauze and geotextile, backfilling of sand and soil, laying of grouting pipes, grouting pipes and pre-buried pipes, and arranging of ERT measuring lines; when arranging ERT measuring lines, a total of three ERT measuring lines are arranged on the sand surface, of which the first ERT measuring line is close to the grouting pipe, the second ERT measuring line is between the grouting pipe and the grouting pipe, and the third ERT measuring line is close to the grouting pipe. The three ERT measuring lines reflect the slurry diffusion reaction in the EICP mineralization reaction; S2. Preparation of cementing solution: The cementing solution consists of soybean urease solution and cementing liquid. The single-phase grouting method is adopted during grouting, and the urease solution and the cementing liquid are mixed and then injected; S3, Circulation Grouting: Use a tee pipe to connect the configured soybean urease solution and cementing liquid respectively, mix the two inside the tee pipe, and inject the soybean urease solution and cementing liquid into the middle grouting cavity through the grouting equipment; use four grouting pipes for synchronous grouting, and control the grouting volume of the grouting pipes through four flow meters to ensure that the four grouting pipes are filled with the same EICP solution; turn on the grouting equipment while grouting to expand the slurry diffusion range to ensure the uniformity of reinforcement; to ensure that the EICP solution fully reacts in the box, the interval time of each grouting cycle is 2 days; to ensure the uniformity of reinforcement in the vertical direction, move the inner grouting pipe upward by 10 cm every 2 grouting times to ensure the uniformity of reinforcement in the vertical direction; S4. Determination of overall permeability of the sample: Determine the overall permeability of the sample after the 0th, 2nd, 4th, 6th, 8th and 10th grouting. Fill water to a height of 80 cm through the water inlet of the right water storage chamber, close the water inlet of the left water storage chamber and open the drainage port to form a large head difference, and maintain the head difference for a certain period of time to form a stable seepage volume. Add water continuously to the water inlet of the right water storage chamber to form a stable head as a whole. Record the seepage volume of the drainage hole of the left water storage chamber within 5 minutes. Test three times for each test and take the average value as the final result. S5. Determination of related parameters: In each grouting cycle, the extracted liquid was collected when the grouting liquid was 50L, 100L, 150L, ​​and 200L, and the calcium ion concentration, conductivity, and pH value of the extracted liquid were measured; after the grouting was completed, the liquid inside multiple pre-buried pipes was extracted to measure its calcium ion concentration, conductivity, and pH value; the soil resistivity after grouting was measured using a high-density resistance meter; the conductivity and pH of the solution in the pre-buried pipe can reflect the extent of the EICP reaction and the diffusion law of the slurry to a certain extent; the conductivity and pH value in the slurry can indirectly reflect the diffusion range and reinforcement effect of the slurry in the model; the calcium ion concentration in the slurry can indirectly reflect the decomposition of urea by urease, and then indirectly reflect the amount of calcium carbonate generated inside the model test, so the conductivity, pH and Ca of the slurry pipe can be used to measure the calcium ion concentration, conductivity, and pH of the slurry. 2+ Concentration was used as an evaluation indicator.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The porous steel plate used in the model allows water to flow and fully simulates the saturated water environment, avoiding the disadvantage of traditional models that cannot simulate saturated water environment. The model can better simulate the actual situation of sand below the groundwater level in actual engineering.

[0019] 2. The pre-buried pipe can be used to measure the ion concentration, pH and conductivity of different parts during the grouting process; these measurement data can be used to preliminarily determine the amount of calcium carbonate generated in different parts and the uniformity of reinforcement.

[0020] 3. The structure of the traditional large-volume model equipment is too simple to meet the research on the bio-enzyme-induced calcium carbonate precipitation technology to strengthen underwater soil. The innovation of this model provides an effective test device for the research on the EICP technology to strengthen underwater sand.

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of an embodiment of the present invention.

[0023] Figure 2 This is a top view of the middle grouting cavity.

[0024] Figure 3 This is a three-dimensional view of the middle grouting cavity. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] In order to avoid the problems that the current large-scale model equipment reinforced by enzyme-induced calcium carbonate precipitation mineralization technology cannot simulate the underwater environment, cannot measure the concentration of ions in the soil and evaluate the reinforcement effect in a single way, the present invention designs a model equipment suitable for EICP reinforcement of large-volume underwater sand on the basis of the existing MICP reinforcement large-scale model, so as to fill the gap in model equipment in related fields.

[0029] like Figures 1 to 3 As shown, this embodiment provides a test device for reinforcing underwater sand based on the EICP technology, including an uncovered test box 1, the interior of the test box is divided into a left water storage chamber 2, a middle grouting chamber 3, and a right water storage chamber 4 along the long side, the right water storage chamber and the middle grouting chamber, and the left water storage chamber and the middle grouting chamber are separated by a porous steel plate 5 and a retaining gauze 6, and a grouting pipe 7, a grouting pipe 8, a pre-buried pipe, and an ERT measuring line 9 are arranged inside the middle grouting chamber.

[0030] The porous steel plate is mainly used to simulate the saturated water environment. The geotextile retaining gauze arranged in the middle grouting cavity plays the role of fixing the sand and retaining the soil to prevent the sand to be reinforced from entering the water storage part at both ends of the test box.

[0031] In the embodiment of the present invention, the test box is welded and assembled with 2 mm thick steel, and its length, width and height are 2m×1.6m×1m respectively, and the overall shape is a coverless rectangular parallelepiped.

[0032] In the embodiment of the present invention, the left water storage chamber, the middle grouting chamber, and the right water storage chamber are divided into three sections according to the ratio of 1:8:1 on the long side of the test box. The size of the middle grouting chamber is 1.6m×1.6m×1m, and the sizes of the left and right water storage chambers are 0.2m×1.6m×1m.

[0033] The grouting pipe and the grouting extraction pipe are acrylic flower tubes with a diameter of 3 cm.

[0034] In the embodiment of the present invention, the embedded pipes include embedded pipes A, B, C, D, E, and F. In order to study the horizontal diffusion law of the slurry, four embedded pipes A, C, E, and F (all with a height of 40 mm) are set, wherein the embedded pipes A, C, and E are located on the seepage path from the grouting pipe to the slurry extraction pipe; in order to study the vertical diffusion law of the slurry, three embedded pipes B, C, and D are set (with unchanged horizontal positions), with heights of 20 mm, 40 mm, and 60 mm, respectively.

[0035] In the embodiment of the present invention, in order to increase the diffusion radius of the slurry, the slurry extraction pipe is opened while grouting and closed at other times; and the pre-buried pipe mainly plays a detection role to monitor the mineralization reaction degree of EICP.

[0036] In the embodiment of the present invention, the left and right water storage chambers are both provided with a water inlet 10 and a water outlet 11 .

[0037] In the embodiment of the present invention, there are four grouting pipes which are vertically arranged around the soil to be reinforced in the middle grouting cavity, and are 20 cm away from the edge of the middle grouting cavity.

[0038] In the embodiment of the present invention, the grouting pipe is vertically arranged in the middle of the soil to be reinforced in the middle grouting cavity, 80 cm away from the edge of the soil.

[0039] In the embodiment of the present invention, the ERT measuring lines are divided into three and arranged on the soil surface of the middle grouting cavity, and each line is arranged with 60 high-density resistance electrodes. Each measurement can measure the resistivity value of the soil at different depths in the same section. The calcium ion tester is used to detect the calcium ion concentration in the waste liquid extracted from the grouting pipe at different times to indirectly reflect the diffusion speed of the slurry.

[0040] In an embodiment of the present invention, the grouting pipe is connected to the grouting equipment, and the grouting equipment includes a binder liquid barrel 12 and a urease solution barrel 13. The binder liquid barrel and the urease solution barrel are respectively connected to the two inlets of the tee pipe 15 via a suction hose 14, and the outlet of the tee pipe is then connected to the grouting pipe via a delivery hose 16.

[0041] In the embodiment of the present invention, a suction pump 17 and a filter are provided on the suction hose, and a flow meter 18 and a pressure gauge 19 are provided on the delivery hose connected to each grouting pipe.

[0042] In the embodiment of the present invention, the slurry extraction pipe is connected to the slurry extraction equipment, and the slurry extraction equipment includes a waste liquid barrel 20. A waste liquid hose 21 is connected between the waste liquid barrel and the slurry extraction pipe, and a suction pump is arranged on the waste liquid hose.

[0043] In the embodiment of the present invention, the EICP technology often has a significant uneven reinforcement effect when reinforcing large-sized soil. In order to reduce the unevenness of the EICP reinforcement effect and achieve the gradual consolidation of large-sized sand, the grouting pipes are composed of an inner grouting pipe 22 and an outer grouting pipe 23. The inner and outer grouting pipes are vertically provided with a plurality of grouting holes 24 around them, and the inner grouting pipe is coaxially inserted inside the outer grouting pipe. The position of the outer grouting pipe is fixed, and the inner grouting pipe is connected to the grouting equipment. The inner grouting pipe can move inside the outer grouting pipe to achieve grouting consolidation at different depths.

[0044] In the embodiment of the present invention, there are a plurality of pre-buried pipes, and the horizontal positions and depths of the plurality of pre-buried pipes are different.

[0045] A method for using a test device for reinforcing underwater sand based on EICP technology comprises the following steps: S1. Preliminary preparation for the test: including laying of retaining gauze and geotextile, backfilling with sand and soil, laying of grouting pipes, grouting pipes and pre-buried pipes, and layout of ERT survey lines; retaining gauze and geotextile are laid on the bottom and around the grouting cavity. The purpose of laying geotextile is to facilitate the removal of solidified sand from the box after the EICP reinforcement is completed. The function of gauze is to prevent soil particles from flowing out of the holes of the porous steel plate, while water can freely pass through the gauze to form a saturated water environment. Different types of sand can be selected for the experiment according to the requirements of the experiment. When backfilling with sand and soil, reserve space for the layout of grouting pipes, grouting pipes and pre-buried pipes. When arranging ERT lines, a total of three lines are arranged on the sand surface. The positions of the ERT lines are fixed. The first ERT line is close to the grouting pipe, the second ERT line is between the grouting pipe and the grouting pipe, and the third ERT line is close to the grouting pipe. The three ERT lines reflect the slurry diffusion reaction in the EICP mineralization reaction. S2. Preparation of cementing solution: The cementing solution consists of soybean urease solution and cementing liquid (calcium chloride + urea). The single-phase grouting method is adopted during grouting, and the urease solution and the cementing liquid are mixed and then injected; In the EICP mineralization process, calcium chloride is mainly used to provide calcium ions, while urea provides raw materials for urease hydrolysis and is used to provide calcium carbonate ions. Calcium ions and calcium carbonate ions are combined to form calcium carbonate precipitation. Too high or too low cementing solution concentration will have an adverse effect on the EICP mineralization reaction. When the cementing solution concentration is too low, the calcium ion concentration is low, and not enough calcium carbonate precipitation can be produced to cement the sand particles, thereby affecting the cementation effect. Therefore, it is very important to fully consider various influencing factors to select urease solution and cementing solution with suitable concentrations for the experiment. The extraction of soybean urease is one of the most important steps in the entire experimental link. The obtained soybeans are crushed through a 100-mesh sieve and stored in a dry environment at 4°C; fresh soybean powder is added to clean water and the soybean urease solution is stirred at a speed of 500rpm / min by a mixer for about 20 minutes. After stirring, the soybean urease solution is allowed to stand for 12 hours; after standing for 12 hours, the soybean urease produces stratification, and the upper clear liquid is taken for use.

[0046] S3, Circulation Grouting: Use a three-way pipe to connect the prepared soybean urease solution and the cementing liquid respectively, mix the two inside the three-way pipe, and inject the soybean urease solution and the cementing liquid into the middle grouting cavity through the grouting equipment; The grouting pressure is set to 0.2Mpa. The setting of the grouting pressure needs to take into account that when the pressure is too low, it is difficult to pour the cementing liquid and urease solution into the box and the grouting time is longer. If the grouting pressure is too high, the calcium carbonate generated in the previous grouting may be destroyed in the next grouting process, thereby affecting the cementing effect of the sand inside the box.

[0047] Four grouting pipes are used for synchronous grouting. The grouting volume of the grouting pipes is controlled by four flow meters to ensure that the four grouting pipes are filled with the same EICP solution. The grouting equipment is turned on while grouting to expand the slurry diffusion range to ensure uniform reinforcement. To ensure that the EICP solution fully reacts in the box, the interval between each grouting cycle is 2 days. To ensure uniform reinforcement in the vertical direction, the inner grouting pipe is moved upward by 10 cm every 2 grouting times to ensure uniform reinforcement in the vertical direction. S4. Determination of overall permeability of the sample: Determine the overall permeability of the sample after the 0th, 2nd, 4th, 6th, 8th and 10th grouting. Fill water to a height of 80 cm through the water inlet of the right water storage chamber, close the water inlet of the left water storage chamber and open the drainage port to form a large head difference, and maintain the head difference for a certain period of time to form a stable seepage volume. Add water continuously to the water inlet of the right water storage chamber to form a stable head as a whole. Record the seepage volume of the drainage hole of the left water storage chamber within 5 minutes. Test three times for each test and take the average value as the final result. S5. Determination of related parameters: In each grouting cycle, the extracted liquid was collected when the grouting liquid was 50L, 100L, 150L, ​​and 200L, and the calcium ion concentration, conductivity, and pH value of the extracted liquid were measured; after the grouting was completed, the liquid inside the A, B, C, D, E, and F pre-buried pipes was extracted with a syringe to measure its calcium ion concentration, conductivity, and pH value; the soil resistivity after grouting was measured using a high-density resistance meter; the conductivity and pH of the solution in the pre-buried pipe can reflect the degree of EICP reaction and the diffusion law of the slurry to a certain extent; the conductivity and pH value in the slurry can indirectly reflect the diffusion range and reinforcement effect of the slurry in the model; the calcium ion concentration in the slurry can indirectly reflect the decomposition of urea by urease, and then indirectly reflect the amount of calcium carbonate generated inside the model test, so the conductivity, pH, and Ca of the slurry pipe can be used to measure the calcium ion concentration, conductivity, and pH of the slurry. 2+ Concentration was used as an evaluation indicator.

[0048] The test device can well simulate the actual engineering conditions of EICP technology reinforcement of saturated sand, and the operation difficulty and labor intensity are low during the test.

[0049] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A test device for reinforcing underwater sand based on EICP technology, characterized by: The test box comprises an uncovered test box, wherein the interior of the test box is divided into a left water storage chamber, a middle grouting chamber, and a right water storage chamber along the long side; the right water storage chamber and the middle grouting chamber, and the left water storage chamber and the middle grouting chamber are separated by porous steel plates and retaining gauze; a grouting pipe, a grouting pipe, a pre-buried pipe, and an ERT measuring line are arranged inside the middle grouting chamber.

2. The test device for reinforcing underwater sand based on EICP technology according to claim 1 is characterized in that: There are four grouting pipes which are vertically arranged around the soil to be reinforced in the middle grouting cavity.

3. The test device for reinforcing underwater sand based on EICP technology according to claim 1 is characterized in that: The grouting pipe is vertically arranged in the middle position of the soil body to be reinforced in the middle grouting cavity.

4. The test device for reinforcing underwater sand based on EICP technology according to claim 1 is characterized in that: The ERT measuring lines are divided into three and arranged on the soil surface of the middle grouting cavity, and each line is arranged with 60 high-density resistance electrodes.

5. The test device for reinforcing underwater sand based on EICP technology according to claim 1 is characterized in that: The grouting pipe is connected to the grouting equipment, which includes a binder liquid barrel and a urease solution barrel. The binder liquid barrel and the urease solution barrel are respectively connected to the two inlets of the three-way pipe through a suction hose, and the outlet of the three-way pipe is connected to the grouting pipe through a delivery hose.

6. The test device for reinforcing underwater sand based on the EICP technology according to claim 5 is characterized in that: The suction hose is provided with a suction pump and a filter, and the delivery hose connected to each grouting pipe is provided with a flow meter and a pressure gauge.

7. The test device for reinforcing underwater sand based on EICP technology according to claim 1 is characterized in that: The slurry extraction pipe is connected to the slurry extraction equipment, and the slurry extraction equipment includes a waste liquid bucket. A waste liquid hose is connected between the waste liquid bucket and the slurry extraction pipe, and a suction pump is arranged on the waste liquid hose.

8. The test device for reinforcing underwater sand based on EICP technology according to claim 1 is characterized by: The grouting pipes are composed of an inner grouting pipe and an outer grouting pipe. A plurality of grouting holes are vertically arranged on the periphery of the inner grouting pipe and the outer grouting pipe. The inner grouting pipe is coaxially inserted inside the outer grouting pipe. The position of the outer grouting pipe is fixed, and the inner grouting pipe is connected to the grouting equipment.

9. The test device for reinforcing underwater sand based on EICP technology according to claim 1 is characterized by: There are a plurality of pre-buried pipes, and there are differences in horizontal positions and depths of the plurality of pre-buried pipes.

10. A method for using the test device for reinforcing underwater sand based on the EICP technology according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Preliminary preparation for the test: including laying of retaining gauze and geotextile, backfilling of sand and soil, laying of grouting pipes, grouting pipes and pre-buried pipes, and arranging of ERT measuring lines; when arranging ERT measuring lines, a total of three ERT measuring lines are arranged on the sand surface, of which the first ERT measuring line is close to the grouting pipe, the second ERT measuring line is between the grouting pipe and the grouting pipe, and the third ERT measuring line is close to the grouting pipe. The three ERT measuring lines reflect the slurry diffusion reaction in the EICP mineralization reaction; S2. Preparation of cementing solution: The cementing solution consists of soybean urease solution and cementing liquid. The single-phase grouting method is adopted during grouting, and the urease solution and the cementing liquid are mixed and then injected; S3, Circulation Grouting: Use a tee pipe to connect the configured soybean urease solution and cementing liquid respectively, mix the two inside the tee pipe, and inject the soybean urease solution and cementing liquid into the middle grouting cavity through the grouting equipment; use four grouting pipes for synchronous grouting, and control the grouting volume of the grouting pipes through four flow meters to ensure that the four grouting pipes are filled with the same EICP solution; turn on the grouting equipment while grouting to expand the slurry diffusion range to ensure the uniformity of reinforcement; to ensure that the EICP solution fully reacts in the box, the interval time of each grouting cycle is 2 days; to ensure the uniformity of reinforcement in the vertical direction, move the inner grouting pipe upward by 10 cm every 2 grouting times to ensure the uniformity of reinforcement in the vertical direction; S4. Determination of overall permeability of the sample: Determine the overall permeability of the sample after the 0th, 2nd, 4th, 6th, 8th and 10th grouting. Fill water to a height of 80 cm through the water inlet of the right water storage chamber, close the water inlet of the left water storage chamber and open the drainage port to form a large head difference, and maintain the head difference for a certain period of time to form a stable seepage volume. Add water continuously to the water inlet of the right water storage chamber to form a stable head as a whole. Record the seepage volume of the drainage hole of the left water storage chamber within 5 minutes. Test three times for each test and take the average value as the final result. S5. Determination of related parameters: In each grouting cycle, the extracted liquid was collected when the grouting liquid was 50L, 100L, 150L, ​​and 200L, and the calcium ion concentration, conductivity, and pH value of the extracted liquid were measured; after the grouting was completed, the liquid inside multiple pre-buried pipes was extracted to measure its calcium ion concentration, conductivity, and pH value; the soil resistivity after grouting was measured using a high-density resistance meter; the conductivity and pH of the solution in the pre-buried pipe can reflect the extent of the EICP reaction and the diffusion law of the slurry to a certain extent; the conductivity and pH value in the slurry can indirectly reflect the diffusion range and reinforcement effect of the slurry in the model; the calcium ion concentration in the slurry can indirectly reflect the decomposition of urea by urease, and then indirectly reflect the amount of calcium carbonate generated inside the model test, so the conductivity, pH and Ca of the slurry pipe can be used to measure the calcium ion concentration, conductivity, and pH of the slurry. 2+ Concentration was used as an evaluation indicator.

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