Reinforcing method for MICP-bionic structure interlayer of coral sand soil body

Abstract

The invention relates to the technical field of buildings, in particular to a coral sand soil body MICP-bionic structure interlayer reinforcing method which comprises the following steps: S1, grading original coral sand, taking fine particles as an interlayer material, and taking medium-coarse particles as a main body filling material; s2, laying a 3D printing bionic geosynthetic material in the fine particles, sequentially injecting a sporosarcina pasteurii bacterial solution and a urea-calcium chloride cementing solution, standing, and alternately grouting for multiple times; s3, the composite interlayer and the main body sand layer are stacked and compacted in a layered mode, and a layered composite structure is constructed; and S4, repeating the steps S1 to S3. The ecological reinforcement technology and the reinforcement technology are combined, a collaborative system of layered construction, interlayer construction and overall reinforcement is constructed, and the reinforcement effect and efficiency are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of building technology, in particular to a MICP-bionic structure interlayer reinforcement method for coral sand soil. BACKGROUND

[0002] As a typical carbonate granular soil, coral sand has high porosity, irregular particle morphology and easy breakage, resulting in weak natural foundation bearing capacity and often causing uneven settlement problems. In layered construction, the difference in specific gravity and hydrodynamic force between coral sand and water naturally forms a layered structure with alternating distribution of fine particle interlayers and medium-coarse particle layers, but the fine particle interlayers generally have low strength, slow pore water pressure dissipation and other problems, and are prone to become the inducing factor of settlement and soft surface.

[0003] Traditional foundation reinforcement measures have disadvantages such as high carbon emission, environmental pollution and poor construction adaptability. Although patent CN202510892512.1 proposes a multi-dimensional ecological low-carbon reinforcement method for coral sand soil, it needs to use enzyme-induced calcium carbonate precipitation technology (EICP) to pretreat coral sand single particles by spraying and standing with urease solution and urea-calcium chloride cementing liquid multiple times, which is complicated and increases energy consumption. In addition, the extraction of urease depends on special equipment, which significantly increases the construction complexity and cost. More importantly, this method does not design a targeted reinforcement scheme for the natural layered characteristics of coral sand, and the spraying method is prone to the phenomenon of "hard on the surface and soft below" with better reinforcement effect on the surface than in the deep layer, which is difficult to solve the stability problem of fine particle interlayer and has the risk of fine particle loss and uneven settlement. At the same time, the traditional two-way grid used has only a simple longitudinal and transverse structure, and the stress path is single, which is prone to stress concentration under dynamic load. In addition, compared with the bionic spider web structure, this grid structure lacks a multi-directional and dense embedded structure, which cannot effectively embed fine particles, leading to easy loss of fine particles under load and difficulty in solving the fundamental problem of poor stability of coral sand fine particle interlayer. Therefore, there is an urgent need for a MICP-bionic structure interlayer reinforcement method for coral sand soil. SUMMARY

[0004] The present application aims to overcome the deficiencies in the prior art, and to provide a MICP-bionic structure interlayer reinforcement method for coral sand soil, which addresses the problems of insufficient bearing capacity of coral sand soil, uneven settlement, uneven distribution of MICP solidification, and limited effect of single reinforcing material.

[0005] The object of the present application can be achieved by the following technical solutions: The technical solution of the present application provides a MICP-bionic structure interlayer reinforcement method for coral sand soil, comprising the following steps: S1, the original coral sand is classified and treated, and the fine particle part obtained by screening or sedimentation is used as the interlayer material, and the medium and coarse particle part is used as the main filling material; S2, a 3D printed biomimetic geosynthetic material is laid in the fine particle material obtained in step S1, and pasteur bacillus pasteurii liquid and urea-calcium chloride cementing liquid are injected in turn, and after standing, multiple alternating grouting is performed to form a composite interlayer, the 3D printed biomimetic geosynthetic material is made of polylactic acid or high-density polyethylene material, and is printed into a biomimetic spider web structure grid; S3, the composite interlayer formed in step S2 is layered and stacked with the main sand layer and is moderately compacted, so that the interlayer and the main layer are combined to form a layered composite structure; S4, steps S1-S3 are repeated to form a multi-layer "MICP-biomimetic structure" interlayer system.

[0006] In some embodiments, in step S1, the classification of coral sand can use a multi-layer standard sieve or sedimentation classification method, and the screening time is 10 to 20 minutes to ensure uniform particle distribution. As more preferred, in step S1, the screening time is 15 minutes. The fine particle size range can be 0.075 to 0.6 mm, and the medium and coarse particle size range is 0.6 to 4 mm.

[0007] In some embodiments, in step S2, the OD600 value of the pasteur bacillus pasteurii liquid is 1.2±0.1, and the injection volume is 1 to 3 times the pore volume of the coral sand. The volume ratio of the liquid to the cementing liquid is 1:(1-3). As more preferred, in step S2, the injection volume of the liquid is 2 times the pore volume of the sample. The volume ratio of the liquid to the cementing liquid can be 1:1 or 1:1.5 or 1:2 or 1:2.5 or 1:3.

[0008] In some embodiments, in step S2, the concentration of the urea-calcium chloride cementing liquid is 0.25-2.0 mol / L. As more preferred, in step S2, the urea and calcium chloride solution are configured at the same concentration, and the concentration is 0.5 mol / L. After the configuration is completed, the two are mixed.

[0009] In some embodiments, in step S2, grouting is performed in a bidirectional grouting manner, that is, the liquid is injected once at the top of the interlayer, and the cementing liquid is injected 3-6 times in the first grouting cycle, and the liquid is injected once at the bottom of the interlayer, and the cementing liquid is injected 3-6 times in the second grouting cycle, which are performed alternately, and the grouting rate is controlled at 1-4 mL / min. As more preferred, in step S2, one grouting cycle is to inject the liquid once, and then inject the cementing liquid 3 times, and the grouting rate is 2 mL / min, and a total of 4-6 grouting cycles are completed to ensure uniform diffusion and reaction of the solution in the pores of the sand body.

[0010] In some embodiments, the rib width of the biomimetic spiderweb structure grid is 0.5-1.5 mm, the rib thickness is 1.5-2.5 mm, the spacing between the ribs is 1-3 mm, the tensile modulus is 2400-2700 MPa, the tensile strength is 40-70 MPa, the elongation at break is 8-15%, the bending modulus is 2500-2900 MPa, the impact strength is 20-40 J / m, and the deformation temperature is 50-70℃.

[0011] In some embodiments, in the S2 step, after each grouting cycle is completed, the sample is placed in an environment at 20-35℃ for 12 h to promote the deposition of calcium carbonate crystals and the stabilization of the structure.

[0012] In some embodiments, in the S3 step, the interlayer thickness is 20-40 mm, and the interlayers are arranged at equal intervals.

[0013] In some embodiments, in the S3 step, the compaction is performed by using a light vibration or low-energy compaction method to ensure that the interlayer and the main layer are closely combined without damaging the cementation structure formed by MICP.

[0014] As more preferred, the interlayer thickness and spacing can be flexibly designed according to the stratum conditions, and the composite interlayer can be arranged at a specific location where a local weak layer is detected in the foundation to strengthen the structural stability and deformation coordination ability of the weak layer. Through the superposition construction of the multi-layer “MICP-biomimetic structure” interlayer system, the structure can be implemented synchronously in the layered construction process without changing the original process, realizing the structure layered control and overall reinforcement coordination, and significantly improving the bearing capacity, uniformity and long-term stability of the coral sand foundation.

[0015] The application discloses a MICP-biomimetic structure interlayer reinforcement method for coral sand soil bodies, and the method is used for constructing a composite interlayer system of “microbial induced mineralization (MICP) + biomimetic geosynthetic material” in layers to efficiently reinforce the coral sand foundation. Figure 2 As shown in the figure, the structure is composed of a coarse-grained soil layer in the coral sand (as a main filling material) and a coral sand fine-grained soil layer treated by MICP-biomimetic structure; the 3D-printed biomimetic spiderweb geosynthetic material structure is embedded in the fine-grained soil layer, and the two structures and the MICP mineralization product cooperatively act to strengthen the mechanical properties of the interlayer.

[0016] Compared with the prior art, the application has the following beneficial effects: (1) In the construction process, the coral sand naturally forms a layered structure with fine particle interlayer and medium-coarse particle layer alternating distribution due to the difference in specific gravity and hydrodynamic force; the present application innovatively utilizes this natural characteristic, adopts multi-layer standard sieve or sedimentation classification method for classification treatment of the original coral sand, the obtained fine particle part is used as interlayer material, and the medium-coarse particle part is used as main filling material, the classification method fits the natural layering characteristics of the coral sand, and the fine particle interlayer with weak mechanical properties is directionally reinforced, so that the overall foundation stability is significantly improved.

[0017] (2) The present application directly uses the MICP technology to reinforce the fine particle interlayer, and omits the cumbersome single particle pretreatment, urease solution extraction, multiple spraying and standing steps in the EICP technology; the latter not only depends on special equipment, increases energy consumption, but also significantly prolongs the construction period and increases the cost. In comparison, the present method only needs to configure the bacillus pasteurii bacterial solution and urea-calcium chloride cementing solution, the process flow is greatly simplified, no special equipment is needed, the construction complexity, cost and time are significantly reduced, and the reinforcement effect equivalent to the EICP pretreated single particle can still be achieved, so that the efficiency and site adaptability are significantly improved.

[0018] (3) The bionic spider web structure adopted by the present application provides more abundant microbial attachment interfaces, so that the microbial mineralization reaction is promoted; the ordinary bidirectional grid only has a simple longitudinal and transverse stress structure, the bearing and buffering functions are not clearly distinguished, the stress conduction path is single, and local stress concentration is easy to occur under dynamic load. The bionic spider web structure of the present application is designed to make the stress more uniform, and the overall mechanical properties of the interlayer are significantly improved; in addition, the multi-directional and dense rib network of the spider web structure can effectively embed the fine particles and effectively prevent the loss of fine sand under the action of dynamic water or load.

[0019] (4) Compared with the spraying method which is easy to cause the solution to gather on the surface and form uneven reinforcement with "hard on the surface and soft below", the present application adopts a bidirectional grouting method, so that the bacterial solution and the cementing solution penetrate and mix in the fine particle interlayer, the uniformity of the reaction liquid distribution is significantly improved; at the same time, through multiple rounds of grouting and standing, calcium carbonate is continuously and densely deposited in the entire interlayer thickness range, effectively eliminating local weak areas, and achieving a reinforcement effect with stronger integrity and more complete structure. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Process flow chart of the MICP-bionic structure interlayer reinforcement method for coral sand soil body; Figure 2 Schematic diagram of the MICP-bionic structure interlayer reinforcement method for coral sand soil body; Figure 3 Effect data chart of Example 1 and Comparative Examples 1-4. Detailed Implementation

[0021] like Figure 1 The flowchart shown is a MICP-biomimetic structure sandwich reinforcement method for coral sand provided by the present invention, which includes the following steps: S1, the original coral sand is graded, and the fine particles obtained by sieving or sedimentation are used as sandwich material, and the medium and coarse particles are used as main filling material. The specific method for grading is as follows: Coral sand is graded using multi-layer standard sieves or sedimentation grading methods to distinguish different particle size components. The sieving time is generally 10-20 minutes, preferably 15 minutes, to ensure uniform particle distribution and sufficient grading. The fine particles obtained from sieving are used as interlayer filler, with a particle size range of 0.075-0.6 mm; the medium-coarse particles are used as the main filling material, with a particle size range of 0.6-4.0 mm.

[0022] S2. Lay 3D printed biomimetic geosynthetic material in the fine particulate material obtained in step S1, and inject Bacillus pasteurellus bacterial solution and urea-calcium chloride cement solution in sequence. After standing, grouting is alternately injected multiple times to form a composite interlayer. In the fine-particle material obtained in step S1, 3D-printed biomimetic geosynthetic material is first uniformly laid in the middle position according to the designed interlayer thickness. The biomimetic material can be made of polylactic acid (PLA) or high-density polyethylene (HDPE), and the printed structure is spider web-like, which is used to provide the spatial skeleton of the interlayer and the interface for microbial attachment, thereby enhancing the structural embedding of mineralized products.

[0023] The method for preparing *Bacillus pasteurellii* bacterial suspension is as follows: First, dissolve each component in deionized water according to the ratio of ammonium chloride 10 g / L, yeast extract 20 g / L, manganese sulfate monohydrate 10 mg / L, and nickel chloride hexahydrate 24 mg / L, and bring the volume to 1000 mL to prepare a culture medium for activation and expansion. Inoculate *Bacillus pasteurellii* into the activation medium and culture in a constant temperature shaking incubator at (28–32) ℃ and 120 r / min for 36 h to obtain the first-generation activated bacterial suspension. Subsequently, expand the culture by mixing the activated bacterial suspension with the expansion medium at a volume ratio of 1:100, and culture with shaking at (25–37) ℃ and 120 r / min for 24–36 h to obtain a bacterial suspension suitable for the MIP reaction. The OD of the obtained bacterial suspension... 600 The value is 1.2±0.1. When using it, inject it into the sand body at a ratio of 1 to 3 times the pore volume of the coral sand.

[0024] The preparation method of urea-calcium chloride cementing solution is as follows: urea solution and calcium chloride solution are prepared at equal concentrations (0.5~2.0 mol / L), fully dissolved, and then mixed and stirred until no visible precipitate is observed. The volume ratio of bacterial solution to cementing solution is 1:(1~3).

[0025] The specific method of grouting is as follows: a bidirectional grouting mode is adopted. In the first grouting cycle, the bacteria solution is injected once and the cementing solution is injected 3-6 times at the top of the interlayer; in the second grouting cycle, the bacteria solution is injected once and the cementing solution is injected 3-6 times at the bottom of the interlayer, and the two are alternately performed, and a total of 4-6 cycles are completed. The grouting rate is controlled at 1-4 mL / min to ensure uniform diffusion and reaction of the solution in the sand body pores. After each grouting cycle is completed, it is placed in an environment of (25-35) °C for 8-12 h to promote the full deposition and structure stabilization of the calcium carbonate crystals.

[0026] Through this step, a uniform and continuous calcium carbonate cementing body can be formed in the interlayer, significantly enhancing the bonding and bearing capacity of the fine-grained sand. The 3D printed biomimetic geotechnical material forms a stable support skeleton therein, enabling the biomineralization product to be deposited along the surface and pore interface thereof, thereby realizing a “microbial mineralization-biomimetic support” synergistic enhancement effect and constructing a MICP composite interlayer structure with excellent compressive, shear and durability performance.

[0027] S3, layering and stacking the composite interlayer formed in the step S2 with the main body sand layer and moderately compacting to combine the interlayer with the main layer to form a layered composite structure; Figure 2 For the reinforcement method schematic diagram, after the composite interlayer is formed in the step S2, it is layered and stacked with the main layer material of medium-coarse particles, and in the process of layering and stacking, the interlayer thickness can be 20-40 mm, preferably 30 mm, and arranged at equal intervals. The compaction method adopts light vibration or low-energy compaction to ensure that the interlayer and the main layer are closely combined without damaging the calcium carbonate cementing structure formed by MICP.

[0028] S4, repeating the steps S1-S3 to form a multilayer “MICP-biomimetic structure” interlayer system.

[0029] After the step S3 is completed, layering and stacking and interlayer preparation are continued, and the steps S1-S3 are repeated to build a multilayer “MICP-biomimetic structure” interlayer system layer by layer. The interlayer thickness and spacing can be flexibly designed according to the stratigraphic conditions and engineering requirements. The interlayer can be arranged at the position where a local weak layer or fine particle enrichment zone is detected in the foundation to form a local reinforcement area, thereby improving the overall uniformity and anti-deformation capacity of the foundation.

[0030] According to actual needs, the steps 1-3 can be repeated multiple times.

[0031] The application will be described in detail below in combination with the drawings and specific embodiments.

[0032] The present embodiment is implemented on the basis of the technical solutions of the present application, and gives detailed implementation modes and specific operation processes, but the protection scope of the present application is not limited to the following examples.

[0033] The following examples, unless otherwise specified, the raw materials or processing techniques, which are all conventional commercial raw materials or conventional processing techniques in the art.

[0034] Example 1 The present embodiment takes the preparation of triaxial specimen and reinforcement test as an example, and provides a MICP-bionic structure sandwich reinforcement method for coral sand soil body, which comprises the following steps: Step 1: Grading treatment of coral sand and preparation of main layer. First, the undisturbed coral sand is graded by using a multi-layer standard sieve or a sedimentation grading method, and the screening time is controlled to be 10-20 min, and the more preferred screening time is 15 min. The fine particles (particle size range 0.075-0.6 mm) obtained by screening are collected as sandwich materials, and the medium-coarse particles (particle size range 0.6-4.0 mm) are used as the main filling material. The medium-coarse particles are layered and filled into the triaxial test mold and lightly compacted, so that the overall relative density of the specimen is about 60%, and the predetermined thickness position is left for subsequent sandwich laying (the sandwich thickness in this embodiment is 30 mm).

[0035] Step two: 3D printing of bionic geosynthetic material and preparation of bacterial solution and cementing solution. According to the designed sandwich thickness, the 3D printing bionic geosynthetic material is uniformly laid in the middle position of the specimen, and the material is preferably polylactic acid (PLA) and is printed into a bionic spider web structure to provide a spatial skeleton and an attachment interface.

[0036] The basic physical parameters of the bionic spider web structure grid are: rib width 1 mm, rib thickness 2 mm, and the spacing between each rib is 2 mm; the corresponding physical and mechanical performance indexes are: tensile modulus 2598 MPa, tensile strength 58 MPa, elongation at break 11%, bending modulus 2755 MPa, impact strength 30 J / m, and deformation temperature 65℃.

[0037] The specific method for preparing the Sporolactobacillus pasteurii bacterial solution is as follows: an activation / expansion medium is prepared by dissolving 10 g / L of ammonium chloride, 20 g / L of yeast extract, 10 mg / L of manganese sulfate monohydrate, and 24 mg / L of nickel chloride hexahydrate in deionized water and diluting to 1000 mL to obtain the activation and expansion medium. The Sporolactobacillus pasteurii is inoculated into the activation medium and cultured in a constant-temperature shaking incubator at 30°C and 120 r / min for 36 h to obtain the activated bacterial solution. Then, the activated bacterial solution is expanded in the expansion medium at a volume ratio of 1:100, and the mixture is cultured at 30°C and 120 r / min for 36 h to obtain the bacterial solution for MICP reaction. The OD value of the obtained bacterial solution is 1.2±0.1, and the bacterial solution is injected into the sand body at a volume of 2 times the pore volume of the coral sand. 600

[0038] The preparation method of the urea-calcium chloride cementing solution is as follows: a urea solution and a calcium chloride solution are prepared at an equal concentration of 0.5 mol / L, mixed and stirred until no visible precipitate is formed, and then used. The volume ratio of the bacterial solution to the cementing solution is 1:1.5.

[0039] Step three: constructing the MICP composite interlayer by bidirectional and alternating grouting. The grouting is performed by bidirectional and alternating grouting, that is, one grouting cycle is as follows: the bacterial solution is first injected into the top of the interlayer once, then the cementing solution is injected four times, then the bacterial solution is injected into the bottom of the interlayer once and the cementing solution is injected four times, and the top and bottom are alternated, and a total of six grouting cycles are completed. The injection volume is 2 times the pore volume of the sand body, and the volume ratio of the bacterial solution to the cementing solution is 1:1.5. The grouting rate is controlled at 2 mL / min. After each grouting cycle, the sample is placed in a 30°C environment for 8 h to promote the deposition of calcium carbonate crystals and the stabilization of the structure. Through the above alternating grouting and standing process, a uniform and continuous calcium carbonate cementing body is formed in the interlayer and is embedded with the biomimetic material.

[0040] Step four: layered filling, compaction, and multi-layer construction. After the interlayer is formed, the composite interlayer and the upper and lower coarse-grained body layers are further layered and moderately compacted. The compaction method is light vibration or low-energy compaction to avoid damaging the cementing structure formed by MICP.

[0041] Figure 2 ​Figure 1 is a schematic diagram of a MICP-bionic structure interlayer reinforcement method for a coral sand body. The embodiment adopts a standard triaxial specimen size, with a specimen diameter of 39.1 mm and a height of 80 mm. In combination with the specimen scale, the interlayer thickness is designed to be 30 mm. Due to the difference in specific gravity and hydrodynamic force, the coral sand body naturally forms a layered structure in which fine particle interlayers and medium-coarse particle layers are alternately distributed. In view of this feature, the original coral sand is first subjected to grading treatment: using a multi-layer standard sieve or sedimentation grading method (screening time controlled to 10-20 min, preferably 15 min), the particles are divided into fine particles (0.075-0.6 mm) and medium-coarse particles (0.6-4.0 mm). The fine particles are used as the interlayer material, and the medium-coarse particles are used as the main filling material. The specimen is constructed with a relative density of 60% to simulate the loose and compacted state, and the compaction method adopts light vibration or low-energy compaction. A 3D-printed bionic spider web structure is laid at the target position of the fine particle interlayer, and the “hard on top and soft on the bottom” problem caused by the spraying method is solved by bidirectional grouting (alternately injecting Bacillus pasteurii bacterial solution and urea-calcium chloride cementing fluid at the top and bottom), thereby forming a stable MICP-bionic structure composite interlayer. The final layered structure is: a medium-coarse particle layer is laid at the bottom, a pretreated composite interlayer is placed in the middle, and a medium-coarse particle layer is covered at the top, forming a three-layer structure of “medium-coarse particle-composite interlayer-medium-coarse particle”. This method effectively improves the strength of the fine particle interlayer through the synergistic effect of the bionic spider web framework support and MICP mineralization, solves the problems of fine particle loss and uneven settlement of the foundation, and optimizes the mechanical properties of the layered structure.

[0042] Comparative Example 1 This comparative example is a fine particle interlayer without any treatment.

[0043] Comparative Example 2 This comparative example prepares a MICP-treated fine particle interlayer without using any grid, and the remaining conditions are consistent with Example 1.

[0044] Comparative Example 3 This comparative example prepares a MICP-bidirectional grid-treated fine particle interlayer, which uses a bidirectional grid to replace the bionic spider web structure grid in Example 1, and the remaining conditions are consistent with Example 1.

[0045] Comparative Example 4 This comparative example prepares an EICP pretreated single particle followed by a MICP-bionic spider web-treated fine particle interlayer, which uses the method in Example 1 of CN202510892512.1.

[0046] Figure 3The triaxial test stress-strain curves of Example 1 and Comparative Examples 1-4 are shown in the figure. Under the condition of confining pressure 200 kPa, the deviatoric stress-strain curves of each sample show significant differences: the peak deviatoric stress of the untreated fine interlayer is 988.5 kPa, the strength is the lowest and the curve is flat, indicating that its mechanical properties are the weakest; after MICP treatment alone, the peak deviatoric stress is increased to 2700 kPa, the strength is increased by 173% compared with the untreated state, confirming that the microbially induced calcium carbonate precipitation technology can effectively improve the cementation characteristics and bearing capacity of fine coral sand; MICP-bi-directional grid treatment further increases the peak deviatoric stress to 3115.44 kPa, the strength is increased by 215%, which reflects the auxiliary reinforcing effect of the reinforced structure on the MICP cementation effect; while the MICP-bionic spider web structure synergistic reinforcement method proposed in the application makes the peak deviatoric stress reach 3535.384 kPa, which is increased by 257% compared with the untreated fine interlayer and increased by 30.9% compared with the pure MICP treatment, showing the best strengthening effect; the peak deviatoric stress of the EICP pretreatment single particle layer combined with MICP-bionic spider web treatment is 3518.89 kPa, and the strength is increased by 256%, which is similar to the MICP-bionic spider web treatment, further verifying the synergistic mechanism of bionic structure and microbial mineralization. It is worth noting that although the EICP pretreatment single particle layer + MICP bionic spider web combination technology performs well, it relies on the single particle pretreatment step, relies on special equipment and introduces a complex process flow. In contrast, the method only needs to configure the bacillus pasteurii bacterial solution and urea-calcium chloride cementing liquid, and the process flow is greatly simplified without the need for special equipment, which significantly reduces the construction complexity and cost while still achieving uniform, stable and comparable reinforcement effect to EICP pretreatment single particle, significantly improving efficiency and site adaptability. This "microbial mineralization + bionic structure" synergistic mechanism not only avoids the dependence on chemical additives or complex equipment of traditional reinforcement technology, but also optimizes the spatial distribution and interfacial bonding performance of the cement by biological inspired structure design, providing an efficient, low-carbon and easy-to-promote technical path for coral sand foundation reinforcement.

[0047] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it. The basic principles and main features of the present application have been described in the above specific embodiments, and some modifications or replacements can be made on the basis of the present application, but these modifications or replacements do not make the corresponding technical solutions deviate from the scope of the present application.

Claims

1. A method for reinforcing coral sandstone with a MICP-biomimetic structural interlayer, characterized in that, Includes the following steps: S1. The original coral sand is graded, and the fine particles obtained by screening or sedimentation are used as interlayer material, while the medium and coarse particles are used as the main filling material. S2. Lay 3D printed biomimetic geosynthetic material in the fine particulate material obtained in step S1, and inject Pasteurella multocida bacterial solution and urea-calcium chloride cementitious solution in sequence. After standing, alternate grouting multiple times to form a composite interlayer. The 3D printed biomimetic geosynthetic material is made of polylactic acid or high-density polyethylene material and is printed as a biomimetic spider web structure grid. S3. The composite interlayer formed in step S2 is piled up and compacted in layers with the main sand layer, so that the interlayer and the main layer are combined to form a layered composite structure. S4. Repeat steps S1 to S3 to form a multi-layer "MICP-biomimetic structure" sandwich system.

2. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone as described in claim 1, characterized in that, In step S1, the coral sand is graded using multi-layer standard sieves or sedimentation grading methods, with a sieving time of 10-20 minutes to ensure uniform particle distribution.

3. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone as described in claim 2, characterized in that, In step S1, the fine particles have a particle size range of 0.075~0.6 mm, and the medium and coarse particles have a particle size range of 0.6~4.0 mm.

4. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone as described in claim 1, characterized in that, In step S2, the OD of the *Bacillus pasteurellii* bacterial culture was... 600 The value is 1.2±0.1, the injection volume is 1 to 3 times the pore volume of coral sand, and the volume ratio of bacterial solution to cementing solution is 1:(1 to 3).

5. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone according to claim 1, characterized in that, In step S2, the concentration of the urea-calcium chloride cementing solution is 0.5~2.0 mol / L.

6. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone according to claim 1, characterized in that, In step S2, a two-way grouting method is adopted, namely: the first grouting cycle injects bacterial solution once and cementing solution 3 to 6 times at the top of the interlayer; the second grouting cycle injects bacterial solution once and cementing solution 3 to 6 times at the bottom of the interlayer; and so on, for a total of 4 to 6 grouting cycles.

7. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone according to claim 6, characterized in that, In step S2, after each grouting cycle is completed, the sample is left to stand for 12 hours in an environment of 20~35℃ to promote the deposition of calcium carbonate crystals and structural stabilization.

8. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone according to claim 6, characterized in that, In step S2, the grouting rate is controlled at 1~4 mL / min to ensure uniform diffusion and reaction of the solution in the sand pores.

9. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone according to claim 1, characterized in that, The biomimetic spiderweb-like structure grid has rib widths of 0.5~1.5mm, rib thicknesses of 1.5~2.5mm, and spacing between ribs of 1~3mm. It has a tensile modulus of 2400~2700MPa, a tensile strength of 40~70MPa, an elongation at break of 8~15%, a flexural modulus of 2500~2900MPa, an impact strength of 20~40J / m, and a deformation temperature of 50~70℃.

10. The MICP-biomimetic structural interlayer reinforcement method for coral sandstone according to claim 1, characterized in that, In step S3, the interlayer thickness is 20~40 mm, and the layers are arranged at equal intervals. Compaction is carried out using light vibration or low-energy compaction.

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