Multi-dimensional ecological low-carbon reinforcement method for coral sand soil body

Abstract

The invention relates to a coral sand soil multi-dimensional ecological low-carbon reinforcement method which comprises the following steps: S1, a urease solution is sprayed on a coral sand single-particle soil layer, a cementing liquid A is sprayed after standing, the urease solution is extracted from legume plants, and the cementing liquid A is obtained by mixing a urea solution and a calcium chloride solution; s2, on the basis of treatment in the step S1, a sporosarcina pasteurii bacterial solution is firstly sprayed, after standing, a cementing solution B is sprayed, the cementing solution B is alternately and circularly sprayed for multiple times, and the cementing solution B is obtained by mixing a urea solution and a calcium chloride solution; s3, a 3D printing geosynthetic material is laid on the basis treated in the step S2; and S4, laying a coral sand single-particle soil layer on the basis of treatment in the step S3, and repeating the steps S1 to S3. According to the method, a single particle size-foundation unit size-engineering size reinforcing system is constructed, comprehensive reinforcing from a microscopic single particle to a macrostructure can be achieved, and the reinforcing effect and efficiency are effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of building technology, and in particular to a multi-dimensional ecological low-carbon reinforcement method for coral sand bodies. Background Art

[0002] Coral sand, due to its rich porosity, irregular shape, and brittle nature, has a low bearing capacity and is prone to uneven settlement, posing challenges to building stability. Traditional foundation reinforcement measures pose challenges such as high carbon emissions, environmental pollution, and poor construction adaptability. Physical reinforcement methods such as dynamic compaction are noisy and energy-intensive, while chemical grouting, due to the environmentally unfriendly slurry, is restricted to coastal areas.

[0003] Biomineralization technology (EICP / MICP) has garnered widespread attention in the field of soil reinforcement due to its environmentally friendly, low-carbon, and highly efficient properties. However, due to the complex pore structure and particle morphology of coral sand, calcium carbonate precipitation during the solidification process using EICP / MICP biomineralization technology is often unevenly distributed, resulting in significant differences in compressive strength and stability across different regions. Furthermore, simply laying geosynthetics to reinforce soil has a relatively limited effect on improving the soil's overall resistance to compression, settlement, and deformation. Furthermore, geosynthetics are susceptible to environmental factors such as ultraviolet light, temperature, chemical erosion, and mechanical damage. Therefore, a multi-dimensional, low-carbon approach to coral sand foundation reinforcement is urgently needed.

[0004] Patent CN115679939A discloses a method for reinforcing soil foundations by combining pretreatment with microbial mineralization technology. This method involves pre-introducing a cementing agent into the soil and then adding a bacterial solution during mixing to enhance the reinforcement effect. While this method offers some improvements over conventional mixing methods, the pretreatment-microbial mineralization roadbed fill must be transported to the construction site within three hours of mixing. This places high demands on construction conditions and time management, potentially limiting its application in some special environments or emergency projects. Patent CN119800955A discloses a foundation vacuum reinforcement device and reinforcement method based on microbial urease, which uses microbial urease such as Sporosarcina pasteurianus solution and a cementing solution to infiltrate into calcareous sand such as coral sand, and uses a high vacuum pump to provide negative pressure during reinforcement to ensure that the microbial urease solution can quickly penetrate into the deep layer of calcareous sand. It can generate rhombic calcite crystal clusters with high hardness, stable structure and a certain arrangement direction on the surface and pores of calcareous sand particles, which can repair extremely small pores. The reinforced soil has uniform texture and high density.

[0005] Other patents such as application numbers 202010119119.6, 202310624182.9, 2024112536.7, and 202311291071.7 also disclose bioreinforcement methods, but have defects such as being environmentally unfriendly, highly carbon-dependent, having locally different curing effects, complex operations, and high costs. Summary of the Invention

[0006] The purpose of the present invention is to overcome the characteristics of coral sand particles such as high porosity, easy breakage, and weak bonding between particles, which can easily lead to problems such as uneven foundation settlement and fine particle loss, thereby providing a multi-dimensional ecological and low-carbon reinforcement method for coral sand soil.

[0007] The present invention breaks through the high-carbon dependence of traditional solidification measures by constructing a multi-scale composite ecological reinforcement system of "single particle scale-foundation unit scale-engineering scale reinforcement", realizes an ecological and low-carbon reinforcement path, and expands engineering application scenarios.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] The technical solution of the present invention is to provide a multi-dimensional ecological low-carbon reinforcement method for coral sand soil, comprising the following steps:

[0010] S1. Single-grain coral sand reinforcement: Spray urease solution onto the single-grain coral sand layer, let it sit, and then spray binder A, which is extracted from legumes and a mixture of urea solution and calcium chloride solution.

[0011] S2. Unit-scale reinforcement of foundation soil: first spray the soil treated in step S1 with a solution of Bacillus pasteurianus, let it stand, and then spray with a binder B, alternately spraying multiple times, wherein the binder B is a mixture of urea solution and calcium chloride solution;

[0012] S3, engineering scale reinforcement: laying 3D printed geosynthetics on the foundation treated in step S2;

[0013] S4. Laying a coral sand single-grain soil layer on the foundation treated in step S3, and repeating steps S1 to S3 multiple times.

[0014] In some specific embodiments, in step S1, the process for extracting the urease solution from beans is: crushing the beans and then sieving them to obtain bean powder, mixing the bean powder with water, letting it stand, and centrifuging it to obtain a supernatant as the urease solution, and the concentration of the urease solution is (90-110) g / L.

[0015] More preferably, in step S1, the process for extracting urease solution from beans is as follows: the beans are crushed and passed through a 100-120 mesh sieve to obtain bean powder, the bean powder is mixed with water in a solid-liquid mass ratio of 1:10, and magnetic stirring is performed for 0.5h to 1.5h to obtain a homogeneous suspension, which is placed in a 4°C refrigerator and allowed to stand for 24h. The bean powder solution is centrifuged at 4000r / min for 15min to 20min using a centrifuge to obtain a supernatant as the urease solution, and the concentration of the urease solution is (90-110)g / L.

[0016] More preferably, the concentration of the urease solution is 100 g / L.

[0017] More preferably, in step S1, the beans may be soybeans, sword beans, yellow beans, etc.

[0018] In some embodiments, in step S1, the cementing fluid A is prepared from a urea solution and a calcium chloride solution at equal concentrations, with the concentration of the cementing fluid A ranging from 0.4 mol / L to 1 mol / L. The cementing fluid A helps form a uniform calcium carbonate cementing layer on the surface of each coral sand particle, improving inter-particle contact and ensuring a thin and uniform sedimentation layer, thus providing conditions for MICP treatment of unit-scale coral sand foundations.

[0019] More preferably, in step S1, the cementing liquid A is prepared by mixing urea solution and calcium chloride solution with equal concentrations, and the concentration of the cementing liquid A is 0.5 mol / L.

[0020] In some specific embodiments, in step S1, urease solution is first sprayed, and after standing for 2 to 3 hours, the cementing liquid A is sprayed. The amount of urease solution and cementing liquid A is calculated based on 1 times the pore volume of coral sand, and the volume ratio of urease solution to cementing liquid A is 1: (1 to 2.5).

[0021] More preferably, the volume ratio of urease solution to binder A is 1:1 or 1:1.5 or 1:2 or 1:2.5.

[0022] As a more preferred method, the spraying device adopts a fine mist nozzle, the nozzle spacing is set at 1 to 2 meters, and the spray rate is controlled at 0.5 to 2L / (min·m 2 ).

[0023] In some specific embodiments, in step S2, the binder B is prepared by mixing urea solution and calcium chloride solution at equal concentrations, and the concentration of the binder B is 1 mol / L to 2 mol / L.

[0024] More preferably, in step S2, the binder B is prepared by mixing urea solution and calcium chloride solution with equal concentrations, and the concentration of the binder B is 1 mol / L.

[0025] In some specific embodiments, in step S2, the bacterial solution of Bacillus pasteurianus is first sprayed, and after standing for 2 to 3 hours, the binder B is sprayed, and the spraying is alternately cycled 3 to 5 times. The amount of Bacillus pasteurianus bacterial solution is 1.5 L / m 2 The dosage of cementing fluid B is 3L / m 2 .

[0026] In some specific embodiments, in step S2, the interval between the alternate cyclic spraying is 6 to 8 hours, to allow for sufficient reaction and to reach the required cumulative precipitation amount.

[0027] In some embodiments, in step S3, the 3D-printed geosynthetics are made of polylactic acid (PLA), and the 3D printing forms a grid structure. The 3D-printed PLA grid structure is used to embed and connect the EICP- and MICP-treated foundation units, effectively preventing uneven foundation settlement and fine particle loss.

[0028] More preferably, in step S3, sandblasting is performed before laying the 3D printed geosynthetics. Walnut shell powder is used as the sandblasting material. This material is suitable for polylactic acid, a biodegradable material used as a raw material for 3D printing, and will not damage the substrate, which is cost-effective.

[0029] The present invention utilizes enzyme-induced calcium carbonate precipitation (EICP) technology to catalyze the reaction and generate calcium carbonate crystals with smaller particle sizes at the scale of single coral sand particles. The EICP technology can adapt to the size and pore characteristics of single coral sand particles, form a dense calcium carbonate coating on the surface of the single coral sand particles, and achieve reinforcement of the single coral sand particles, overcoming the problems of large pores, easy breakage, and weak adhesion of the coral sand particles themselves, thereby improving the compressive strength of the single particles.

[0030] like Figure 2 As shown, the EICP of the present invention is a urease that is directly extracted from plants such as soybeans and sword beans to catalyze the reaction. Urease participates in the hydrolysis of urea to produce CO3 2- , and the Ca in the surrounding environment 2+ The combination forms a coating of calcium carbonate crystals that covers the surface of the coral sand.

[0031] At the foundation unit scale, the catalytic reaction using microbial induced calcium carbonate precipitation (MICP) usually produces calcium carbonate crystals with relatively large particle size, which are more suitable for precipitation between particles. After EICP treatment of single coral sand particles, the calcium carbonate coating generated on its surface can provide nucleation sites for the attachment of MICP reaction microorganisms and calcium carbonate crystals, promote microbial attachment and subsequent epitaxial growth of CaCO3 crystals, and generate a CaCO3 cementation network between particles, thereby achieving cementation reinforcement between unit soil particles and improving the overall compressive strength and structural stability of the soil.

[0032] like Figure 3As shown, the MICP of the present invention utilizes the widely occurring microorganism Sporosarcina pasteurii, which, through its own metabolism, undergoes a series of biochemical reactions with other substances in the environment. This biological process induces the formation of mineral precipitation such as carbonates and sulfates, which fill the pores between sand particles and act as a bond between sand particles, thereby improving the physical, mechanical, and engineering properties of the soil. The main chemical reaction process is as follows:

[0033]

[0034] Ca 2+ +Cell→Cell-Ca 2+ (2)

[0035]

[0036] On an engineering scale, the stiffness, strength, and elongation of traditional geosynthetics are fixed in production and difficult to adjust to meet different engineering requirements. Moreover, their performance deteriorates after aging, which can easily lead to secondary pollution risks. Figure 4 As shown, the 3D printed geosynthetics of the present invention can be embedded in the coral sand soil reinforced by EICP+MICP through a customized grid structure, overcoming the problem of insufficient reinforcement of EICP / MICP technology when facing large-scale foundations, while enhancing the overall anti-subsidence and anti-deformation capabilities of the project. In addition, the 3D printing raw material uses PLA (polylactic acid) biodegradable material, which meets environmental protection requirements and avoids secondary pollution.

[0037] This invention constructs a multi-dimensional composite ecological coral sand foundation reinforcement system from the single particle scale to the foundation unit scale to the engineering scale. This system can achieve comprehensive reinforcement from the microscopic single particle to the macroscopic structure, effectively improving the reinforcement effect and efficiency, deeply implementing the concept of environmental protection, and effectively overcoming the high energy consumption, high cost, and environmental issues of traditional methods. The entire process does not produce harmful pollutants, which contributes to ecological protection.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) Since the surface of coral sand particles is rough, porous, irregular in shape, and the bonding between particles is weak, when a single EICP or MICP biomineralization technology is used, urease or bacterial solution is easily lost or accumulated locally, and calcium carbonate precipitation is often unevenly distributed during the solidification process, resulting in large differences in the compressive strength and stability of different regions. The present invention utilizes EICP and MICP biomineralization technologies to generate calcium carbonate crystals with different particle sizes, that is, the calcium carbonate crystals generated by the catalytic reaction of EICP technology are smaller, and are coated on the surface of coral sand to form a calcium carbonate coating layer. The calcium carbonate coating layer provides nucleation sites for the attachment of MICP reaction microorganisms and calcium carbonate crystals, promotes the attachment of microorganisms and the subsequent epitaxial growth of CaCO3 crystals, forms relatively large calcium carbonate crystals, and forms a CaCO3 cementation network between the particles, thereby achieving cementation reinforcement between unit soil particles and improving the overall compressive strength and structural stability of the soil. Finally, by laying 3D printed geosynthetics, the problem of low local strength caused by limited permeability and uneven distribution of bacterial liquid in biomineralization can be overcome, the overall mechanical properties under the action of microorganisms can be ensured, and large-volume, multi-level, and overall foundation reinforcement can be achieved. In this way, a multi-dimensional composite ecological reinforcement system of "single particle scale-foundation unit scale-engineering scale" is constructed, and further improving the EICP+MICP biomineralization technology will inevitably fully meet the shear resistance, tensile strength, and overall stability requirements of large-scale foundations.

[0040] (2) The multi-dimensional composite ecological reinforcement system of "single particle scale-foundation unit scale-engineering scale" constructed by the present invention, at the single particle scale, uses enzyme-induced calcium carbonate precipitation technology (EICP) to catalyze the reaction to generate calcium carbonate crystals with smaller particle size, forming a dense coating layer on the surface of coral sand particles, thereby achieving single particle reinforcement, and its compressive strength can reach 13.43MPa, which is 19% higher than the single particle strength of unreinforced coral sand (11.33MPa). At the foundation unit scale, microbial induced calcium carbonate precipitation technology (MICP) is used to produce calcium carbonate crystals with relatively large particle size and calcite structure, which precipitate between particles and form a cementation network, effectively improving the overall stability of the soil. Under the confining pressure of 200Kpa, its peak strength can reach 1.96MPa, which is 63% higher than the strength of unreinforced coral sand (1.2MPa). On an engineering scale, considering the uneven reinforcement that may occur when using EICP or MICP technology alone, the present invention uses 3D printing technology to customize the grid structure of geosynthetics and embeds soil units treated with EICP+MICP to significantly improve the reinforcement effect and efficiency. Under a confining pressure of 200kpa, the strength of the reinforced coral sand can reach 3.5MPa, which is 79% higher than the strength of the soil sample (1.96MPa) without 3D printed geosynthetics.

[0041] (3) The present invention utilizes an organic skeleton constructed from 3D printed geosynthetics, which reduces the impact of construction time and site conditions on reinforcement uniformity and has greater adaptability;

[0042] The present invention relies entirely on biomineralization and physical skeletons, which not only reduces carbon emissions, but also highlights the unique advantages of the synergistic enhancement of microbial cementation and organic skeletons. It shows the characteristics of compatibility with green environmental protection, cost-effectiveness, low carbon, wide application range, and long-term stability. It provides new ideas and new methods for modern green engineering construction and has huge application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of a multi-dimensional ecological low-carbon reinforcement method for coral sand soil of the present invention.

[0044] Figure 2 Schematic diagram of the reaction process of single coral sand particle reinforcement using enzyme-induced calcium carbonate precipitation technology (EICP).

[0045] Figure 3 Schematic diagram of the unit-scale reaction process of microbial induced calcium carbonate precipitation (MICP) technology to strengthen coral sand foundation.

[0046] Figure 4 Schematic diagram of laying a layer of 3D-printed geosynthetics to reinforce the foundation on an engineering scale.

[0047] Figure 5 Schematic diagram of reinforced foundation that repeats “single particle scale-foundation unit scale-engineering scale” multiple times.

[0048] Figure 6 This is an SEM scan of coral sand particles before reinforcement.

[0049] Figure 7 This is a SEM scan of coral sand after being reinforced by enzyme + microbial induced calcium carbonate precipitation (EICP+MICP) technology.

[0050] Figure 8 It is the unconfined compressive strength of single particle reinforced with EICP.

[0051] Figure 9 The stress-strain curve of unreinforced coral sand

[0052] Figure 10 These are the stress-strain curves of the foundation unit soil after EICP pre-reinforcement of single particles and MICP reinforcement.

[0053] Figure 11 Stress-strain curves of foundation soil after EICP+MICP reinforcement and laying of a layer of 3D-printed geosynthetics.

[0054] Figure 12 The stress-strain curves of the foundation soil after two repeated EICP+MICP+3D printing geosynthetics. DETAILED DESCRIPTION

[0055] like Figure 1 FIG. 1 is a flow chart of a multi-dimensional ecological low-carbon reinforcement method for coral sand soil provided by the present invention, comprising the following steps:

[0056] Step 1: Using enzyme-induced calcium carbonate precipitation (EICP) technology, urease solution and cementing solution A are sprayed in sequence on a single-particle scale to crystallize and solidify the pores of single coral sand particles.

[0057] The specific extraction method of urease solution is as follows: ordinary commercially available soybeans are crushed and passed through a 100-120 mesh sieve, the soybean powder is mixed with distilled water, and soybean powder solutions of different concentrations are prepared. The suspension is stirred with a magnetic stirrer for 0.5-1.5 hours to obtain a homogeneous suspension, which is placed in a 4°C refrigerator and allowed to stand for 24 hours. The soybean powder solution is centrifuged at 4000 r / min for 15-20 minutes using a centrifuge. The supernatant obtained is the urease extract. The concentration of the urease solution is (90-110) g / L and is stored at 4°C±0.5°C for later use.

[0058] The specific method for preparing the cementing liquid A is: prepare it with equal concentrations of urea solution and calcium chloride solution, mix and stir them after they are fully dissolved until there is no precipitation, and then obtain the cementing liquid A with a concentration of 0.4mol / L to 1mol / L, and more preferably the cementing liquid A with a concentration of 0.5mol / L.

[0059] The specific method of spraying is: first spray the urease solution, then let it stand for 2 to 3 hours, and then start spraying the cementing liquid A. The spraying device uses a fine mist nozzle, the nozzle spacing is set at 1 to 2 meters, and the spray rate is controlled at 0.5 to 2L / (min·m 2 ), calculated based on 1 times the pore volume of coral sand, the volume ratio of urease solution to cementing fluid A is 1:(1~2.5), which can be 1:1 or 1:1.5 or 1:2 or 1:2.5.

[0060] Step 2: Using microbial induced calcium carbonate technology (MICP), the coral sand foundation unit scale is reinforced by cyclically spraying Bacillus pasteurianus liquid and cementing fluid B on the basis of EICP pre-reinforced coral sand single particles.

[0061] The specific method for preparing a Sporosarcina pasteurianus culture liquid is as follows: the activation medium and expansion medium are composed of 20 g yeast extract, 10 g peptone, 10 g sodium chloride, and 5 g ammonium sulfate, and the volume is adjusted to 1000 mL with distilled water. First, Sporosarcina pasteurianus is inoculated into the activation medium and cultured in a constant temperature shaking incubator at 28°C to 32°C and 120 rpm for 36 hours to obtain a seed liquid. The culture is then expanded at a volume ratio of seed liquid to expansion medium of 1:100, and cultured in a constant temperature shaking incubator at 25°C to 37°C and 120 rpm for 24 to 36 hours to obtain a Sporosarcina pasteurianus culture liquid.

[0062] The specific method for preparing the cementing fluid B is: prepare it with equal concentrations of urea solution and calcium chloride solution, mix and stir them after they are fully dissolved until there is no precipitation, and then obtain a cementing fluid B with a concentration of 1 mol / L to 2 mol / L.

[0063] The specific method of cyclic spraying is: first spray the pasteurian spore octahedral bacteria solution, let it stand for 2 to 3 hours, then spray the cementing liquid B, and repeat the spraying cycle 3 to 5 times. The time interval between each spraying cycle is 6 to 8 hours to allow for sufficient reaction and to reach the required cumulative precipitation amount. The dosage of pasteurian spore octahedral bacteria solution is 1.5L / m 2 The dosage of cementing fluid B is 3L / m 2 The dosage ratio of Bacillus pasteurianus liquid to cementing liquid B is 1:2.

[0064] Step 3: Determine the three-dimensional digital model of the geosynthetics and output it through a 3D printer to obtain the 3D-printed geosynthetics. Based on step 1 (single particle scale reinforcement) and step 2 (foundation soil unit scale reinforcement), lay the green 3D-printed geosynthetics to achieve overall reinforcement of the foundation soil.

[0065] Geosynthetics are made of biodegradable material polylactic acid (PLA) and are 3D printed into a grid structure. Before laying the 3D printed geosynthetics, they need to be sandblasted, and walnut shell powder is used as the sandblasting material.

[0066] Steps 1 to 3 can be repeated multiple times according to project requirements.

[0067] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0068] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0069] Example 1

[0070] This embodiment takes the reinforcement of coral sand foundation soil on a certain island reef as an example. The multi-dimensional ecological low-carbon reinforcement method of coral sand soil includes the following steps:

[0071] Step 1: Determine the basic characteristics of the coral sand foundation by exploring the geological data of the coral sand foundation, select a 1.2m*2.0m coral sand area, and estimate the required volume of each component such as the bacterial solution / urease solution and the cementing solution.

[0072] First, commercially available soybeans were ground and passed through a 100-mesh sieve. The soybean powder was mixed with distilled water and stirred in a magnetic stirrer for 0.5–1.5 hours to obtain a homogeneous suspension. The suspension was then placed in a 4°C refrigerator and allowed to stand for 24 hours. The soybean powder solution was then centrifuged at 4000 rpm for 15–20 minutes to obtain the supernatant, which was the urease extract at a concentration of 100 g / L. Urea solution and calcium chloride solution were then prepared in equal concentrations and stirred until fully dissolved and free of precipitation, yielding a 0.5 mol / L binder A.

[0073] Then, the coral sand particles were processed in batches. First, the urease solution was sprayed, and then the particles were allowed to stand for 2 to 3 hours before the binder A was sprayed. The spraying device used a fine mist nozzle with a nozzle spacing of 1 to 2 meters and a spray rate of 0.5 to 2 L / (min·m 2 ), the dosage of urease extract is 1L / m 2 The dosage of cementing fluid A is 1.5L / m 2 .

[0074] Select a single particle of reinforced coral sand and conduct unconfined compressive strength test, such as Figure 8 As shown in the figure, the unconfined compressive strength increased from 11.33 MPa to 13.43 MPa, which is 19% higher than the single particle strength of unreinforced coral sand.

[0075] Step 2: Prepare the activation medium and expansion medium as follows: Take 20 g of yeast extract, 10 g of peptone, 10 g of sodium chloride, and 5 g of ammonium sulfate, and dilute to 1000 mL with distilled water. First, inoculate Sporosarcina pasteuriana (purchased strain number: BNCC337394) into the activation medium and shake incubate at 28°C to 32°C and 120 rpm for 36 h to obtain a seed solution. Then, expand the medium at a volume ratio of 1:100 for seed solution: expansion medium. Shake incubate in a constant temperature shaking incubator at 25°C to 37°C and 120 rpm for 24-36 h to obtain a Sporosarcina pasteuriana culture solution.

[0076] Urea solution and calcium chloride solution are mixed in equal concentrations, and after they are fully dissolved, they are mixed and stirred until there is no precipitation, thereby obtaining a cementing fluid B with a concentration of 1 mol / L.

[0077] The single particle sample after EICP reinforcement in step 1 was divided into the required unit size and sprayed with the pasteurized spores of the coccus. After standing for 2 to 3 hours, the cementing liquid B was sprayed. The spraying cycle was repeated 3 to 5 times. The interval between each spraying cycle was 6 to 8 hours to allow for sufficient reaction and to achieve the required cumulative precipitation. The amount of pasteurized spores of the coccus was 1.5L / m 2 The dosage of cementing fluid B is 3L / m 2 The dosage ratio of Bacillus pasteurianus liquid to cementing liquid B is 1:2.

[0078] The block sample with the least disturbance was taken in the reinforcement unit area, and the coral sand sample that met the requirements of the triaxial shear test was prepared for triaxial test. Under the confining pressure of 200kPa, the peak deviatoric stress was increased from 1.2MPa ( Figure 9 ) to 1.96MPa (such as Figure 10 ), which is 63% higher than that of unreinforced soil samples.

[0079] Electron microscope scanning tests were conducted on unreinforced coral sand samples and coral sand samples reinforced with EICP+MICP in the area. Figure 6 As shown in the figure, the unreinforced coral sand sample is porous, with weak bonding between particles and a loose accumulation state. Therefore, it is easily affected by external loads and seepage, resulting in particle rearrangement and structural instability. Figure 7 The figure shows the reinforced coral sand sample. As can be seen from the figure, after being reinforced by EICP technology, the pores of the single coral sand particles are filled with calcium carbonate crystals, forming a continuous coating layer, which effectively fills the micropores on the surface of the particles. In addition, based on the EICP pretreatment, the MICP technology further induces the formation of calcium carbonate crystals with larger particle size and clear morphology, which are mainly deposited between particles, playing a cementing role between particles, enhancing the integrity of the overall structure, improving the contact state between particles, and thus improving the peak strength and stiffness of the reinforced unit body.

[0080] Step 3: Design a three-dimensional digital model of the 3D printed geosynthetics as needed, print it with biodegradable material PLA, sandblast the 3D printed geosynthetics with walnut shell powder, and then lay the 3D printed geosynthetics in the foundation soil.

[0081] On the coral sand single particles reinforced by EICP+MICP, 3D printed customized grid structure geosynthetics are laid, and the embedded effect of the customized grid of 3D printed geosynthetics is used to enhance the overall anti-settlement and anti-deformation capabilities of the project. Figure 4 As shown, this is laying a layer of 3D printed geosynthetics. If you are facing deep soil reinforcement, you can repeat steps 1, 2, and 3. Figure 5As shown in the figure, the overall reinforcement of the foundation soil is achieved on an engineering scale.

[0082] Standard coral sand triaxial shear test specimens were taken from the reinforced area, with one layer of 3D printed geosynthetics reinforced (one cycle of steps 1 to 3) and two layers of 3D printed geosynthetics reinforced (two cycles of steps 1 to 3). Under the conditions of 200 kPa confining pressure and one layer of reinforcement, the peak deviatoric stress increased from 1.96 MPa ( Figure 10 ) increased to 2.31MPa( Figure 11 ), the strength of the unreinforced coral sand increased by 18%. Under the conditions of 200Kpa confining pressure and two layers of reinforcement, the peak deviatoric stress increased from 1.96MPa ( Figure 10 ) increased to 3.5MPa( Figure 12 ), compared with the soil sample without 3D printed geosynthetics, the peak deviatoric stress increased by 79%, and compared with the soil sample without 3D printed geosynthetics, the peak deviatoric stress increased by 2.31MPa ( Figure 11 ) increased to 3.5MPa( Figure 12 ), the improvement effect reached 52%. It can be seen that with the increase of the number of reinforcement layers, the stress on the coral sand body becomes more uniform, the strength becomes higher, and the overall stability is significantly improved.

[0083] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A multi-dimensional ecological low-carbon reinforcement method for coral sand soil, characterized in that: The steps include: S1. Single-grain coral sand reinforcement: Spray urease solution onto the single-grain coral sand layer, let it sit, and then spray binder A, which is extracted from legumes and a mixture of urea solution and calcium chloride solution. S2. Unit-scale reinforcement of foundation soil: first spray the soil treated in step S1 with a solution of Bacillus pasteurianus, let it stand, and then spray with a binder B, alternately spraying multiple times, wherein the binder B is a mixture of urea solution and calcium chloride solution; S3, engineering scale reinforcement: laying 3D printed geosynthetics on the foundation treated in step S2; S4. Laying a coral sand single-grain soil layer on the foundation treated in step S3, and repeating steps S1 to S3 multiple times.

2. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 1, characterized in that: In step S1, the process for extracting urease solution from legumes is as follows: the legumes are crushed and sieved to obtain bean powder, the bean powder is mixed with water, allowed to stand, and centrifuged to obtain a supernatant as the urease solution, and the concentration of the urease solution is (90-110) g / L.

3. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 1 is characterized in that: In step S1, the cementing liquid A is prepared by mixing urea solution and calcium chloride solution with equal concentrations, and the concentration of the cementing liquid A is 0.4 mol / L to 1 mol / L.

4. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 1, characterized in that: In step S1, urease solution is first sprayed, and after standing for 2 to 3 hours, cementing liquid A is sprayed. Calculated based on 1 times the pore volume of coral sand, the volume ratio of urease solution to cementing liquid A is 1: (1 to 2.5).

5. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 1, characterized in that: In step S1, the spraying device uses a fine mist nozzle, the nozzle spacing is set at 1 to 2 meters, and the spray rate is controlled at 0.5 to 2L / (min·m 2 ).

6. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 1 is characterized in that: In step S2, the cementing liquid B is prepared by mixing urea solution and calcium chloride solution with equal concentrations, and the concentration of the cementing liquid B is 1 mol / L to 2 mol / L.

7. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 1, characterized in that: In step S2, first spray the pasteurian spore octahedral bacteria liquid, let it stand for 2 to 3 hours, then spray the cementing liquid B, alternately spray 3 to 5 times, and the amount of pasteurian spore octahedral bacteria liquid is 1.5L / m 2 The dosage of cementing fluid B is 3L / m 2 .

8. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 7, characterized in that: In step S2, the interval time of the alternate cycle spraying is 6 to 8 hours.

9. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 1, characterized in that: In step S3, the 3D printed geosynthetics are made of polylactic acid, and 3D printing forms a grid structure.

10. The multi-dimensional ecological low-carbon reinforcement method for coral sand soil according to claim 9, characterized in that: In step S3, sandblasting is performed before laying the 3D printed geosynthetics, and walnut shell powder is used as the sandblasting material.

Images