Layered Embedding Method for Reinforcing Calcareous Sand Based on Biomimetic Tortoise Shell Pattern Geomembrane

Abstract

This invention relates to the field of geotechnical engineering, specifically to a method for reinforcing calcareous sand based on a biomimetic tortoise-shell pattern geomembrane using layered embedding. This invention combines the biomimetic principles of tortoise-shell structures with modern geosynthetic material technology to construct a scientifically sound integrated "material-structure-process" solution, which is expected to provide a new technical approach for calcareous sand foundation treatment and promote the progress and development of marine geotechnical engineering technology.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, specifically to a layered embedding method for reinforcing calcareous sand based on a biomimetic tortoise shell pattern geomembrane. It can be widely applied to the treatment of calcareous sand foundations in scenarios such as highway subgrades, port and wharf storage yards, coastal reclamation projects, and wind power plant foundations, and belongs to the field of foundation treatment and reinforcement technology. Background Technology

[0002] Calcareous sand, a special type of soil and rock material widely distributed in tropical and subtropical marine environments, is mainly formed from the long-term deposition and evolution of calcium carbonate materials such as marine organism skeletons, shells, and coral fragments. This unique formation mechanism endows calcareous sand with a series of distinctive physical and mechanical properties: its particle morphology is extremely irregular, mostly angular, flaky, or dendritic, with well-developed internal pores, numerous internal pores, and surface depressions; its particle strength is relatively low, with its main component, calcium carbonate, having a Mohs hardness of only about 3, far lower than that of quartz sand (7); and its interparticle cementation is poor, with a loose structure in its natural state and easily dissolved cementing substances. These special engineering characteristics lead to prominent problems in calcareous sand foundations, such as low bearing capacity, high compressibility, and susceptibility to particle breakage and strain softening. Under dynamic loads, it also exhibits significant particle reorganization and volume compression, severely restricting the construction and safe operation of major projects such as coastal engineering, island and reef construction, and offshore wind power foundations.

[0003] Traditional methods for treating calcareous sand foundations have developed over many years, resulting in several relatively mature technical systems. Vibratory compaction increases the density of sand through mechanical vibration, but it is poorly adapted to the easily breakable nature of calcareous sand. Studies show that when the vibration acceleration exceeds a certain critical value, the particle breakage rate of calcareous sand can reach over 30%, leading to a decrease in long-term stability. Cement mixing pile technology increases bearing capacity through the solidification reaction between cement and soil, but faces severe challenges in marine environments: the alkalinity of cement (pH can reach 12-13) may impact marine ecosystems, and the calcium hydroxide produced during cement hydration easily reacts with chloride and magnesium ions in seawater to generate expansive substances, leading to strength reduction. Reinforced soil technology improves the overall integrity of the soil by introducing reinforcing materials such as geogrids and geotextiles, but conventional reinforcing materials have poor interfacial friction characteristics with calcareous sand. Field tests show that the interfacial friction angle between smooth geomembranes and calcareous sand is typically 5-8 degrees lower than its internal friction angle, and the reinforcing materials are unable to effectively limit the lateral displacement and breakage of particles.

[0004] With the in-depth development of geosynthetics, modern foundation treatment technology is undergoing significant changes. Geomembranes, as an important category of geosynthetics, have evolved from their traditional single function of seepage prevention to multi-functional composites that provide reinforcement, drainage, and protection. From a materials science perspective, geomembranes have evolved from polyvinyl chloride (PVC) and low-density polyethylene (LDPE) to high-density polyethylene (HDPE) and polypropylene (PP) and other high-performance polymers. From a structural design perspective, various structural forms have emerged, including smooth, textured, reinforced, and composite surfaces. In particular, textured geomembranes, which enhance reinforcement by increasing the interfacial friction coefficient, have become a research hotspot in recent years. However, the design of existing textured geomembranes is mostly based on experience, lacking systematic theoretical guidance and optimization methods. Research on the matching of parameters such as texture shape, size, and distribution with soil particle characteristics is insufficient, making it difficult to achieve ideal reinforcement and embedding effects in special media such as calcareous sand.

[0005] Meanwhile, bionics is showing great promise in the application of geotechnical materials and structural design. Through millions of years of evolution and optimization, nature has developed many biological structures with excellent mechanical properties. The tortoise shell, as a typical biological armor structure, possesses a unique hexagonal microstructure system with good mechanical properties and energy dissipation mechanisms. Research shows that the hexagonal plate structure of the tortoise shell can effectively distribute local impact loads throughout the shell, while achieving good deformation coordination through flexible connections between the plates. This structural characteristic is well-suited to the interaction mechanism requirements between geomembranes and soil: on the one hand, sufficient stiffness is needed to limit soil deformation; on the other hand, good deformation coordination is needed to accommodate foundation settlement.

[0006] However, current research on biomimetic geomembranes largely remains at the stage of macroscopic morphological imitation, with several key issues urgently needing to be addressed: First, there is a lack of in-depth optimization of the crushing mechanism and interfacial response characteristics of calcareous sand particles, and insufficient research on the scale matching between existing textured structures and calcareous sand particles; second, the quantitative relationship between the geometric parameters of textured structures (such as depth, side length, and wall thickness) and interfacial mechanical properties is unclear, resulting in a lack of theoretical guidance for design; third, the collaborative working mechanism of multi-layer composite geomembranes in layered embedded structures is still unclear, and parameters such as the optimal spacing and laying direction of each geomembrane layer lack systematic research; fourth, construction technology and quality control standards need to be improved, especially key technologies such as laying accuracy control and interlayer compaction quality control in marine environments, which require further standardization.

[0007] From a materials science perspective, the development of modern geomembranes places higher demands on polymer materials. In addition to basic mechanical properties, long-term durability indicators such as weather resistance, chemical corrosion resistance, and aging resistance must also be considered. In marine environments, environmental factors such as ultraviolet radiation, salt spray corrosion, wet-dry cycles, and temperature changes accelerate the aging and degradation process of polymer materials. While commonly used HDPE materials have good chemical stability, they still undergo molecular chain breakage under long-term ultraviolet radiation; PP materials, although having good UV resistance, are prone to embrittlement at low temperatures; and PET materials, while having high strength, have relatively poor hydrolytic stability. Therefore, developing high-performance geomembrane material systems suitable for marine environments, including the selection of matrix resins, additive formulations, and the design of anti-aging systems, has become an important research direction.

[0008] From a construction technology perspective, the unique geological conditions of calcareous sand areas pose challenges to traditional construction techniques. Calcareous sand foundations are typically located in coastal areas or island / reef regions, where construction sites are narrow and access for large equipment is difficult. The influence of wind and waves in the marine environment limits the construction window. The high compressibility and fragility of calcareous sand place special demands on compaction processes, necessitating the development of specialized lightweight and intelligent construction equipment and quality control systems.

[0009] In summary, developing a method for reinforcing calcareous sandy soil that combines biomimetic structural optimization, material durability, convenient construction, and environmental friendliness requires systematic innovation across three levels: materials, structure, and process. This necessitates addressing fundamental theoretical issues and overcoming key technological bottlenecks, which is precisely the core starting point and innovation of this invention. By combining the biomimetic principles of tortoise shell structures with modern geosynthetic material technology, a scientifically sound integrated solution encompassing materials, structure, and process can be constructed, potentially providing a new technological path for calcareous sandy foundation treatment and promoting the advancement and development of marine geotechnical engineering technology. Summary of the Invention

[0010] The fundamental objective of this invention is to systematically solve the core technical challenges faced by calcareous sand in marine engineering construction, namely, the problems of easily broken particles, poor structural cohesion, low foundation bearing capacity, and insufficient long-term stability. Based on an in-depth analysis of existing calcareous sand reinforcement technologies and a comprehensive consideration of the special needs of marine engineering, this invention aims to establish a complete integrated "materials-structure-process" technology system, with specific objectives including:

[0011] (1) Material-level innovation: Breaking through the technical bottlenecks of traditional geomembranes with single function and insufficient interfacial performance, multi-layer composite geomembranes with tortoise shell texture surface structure are designed through biomimetic principles to achieve synergistic optimization of material mechanical properties and interfacial friction characteristics. In particular, for the durability requirements of marine environments, a polymer composite material system with excellent anti-aging and corrosion resistance has been developed.

[0012] (2) Structural innovation: Construct a layered embedded structure with alternating layers of "geomembrane-calcareous sand". Through the reinforcement effect of the biomimetic geomembrane and the compaction effect of the calcareous sand layer, a synergistic working mechanism is formed to establish a multi-defense system, effectively limiting particle breakage and lateral displacement, and significantly improving the overall stiffness and stability of the soil.

[0013] (3) Optimize the process and develop a layered laying and compaction process suitable for marine environments to solve the problems of complex construction conditions and difficult quality control in calcareous sand areas, form a standardized and replicable construction technology system, and ensure the consistency and reliability of reinforcement effect.

[0014] Specifically, this invention provides a method for reinforcing calcareous sandy soil by layering and embedding based on a biomimetic tortoise-shell pattern geomembrane, which includes the following steps:

[0015] Step 1: Lay the first layer of the biomimetic tortoise shell pattern geomembrane on the calcareous sandy soil base to be reinforced;

[0016] Step 2: Lay a layer of calcareous sand on the geomembrane and compact it initially;

[0017] Step 3: Repeat the above laying and compaction steps, layering the geomembrane and calcareous sand to form a layered embedded structure;

[0018] Step 4: Cover the top layer with calcareous sand and perform final compaction to complete the reinforcement construction; The biomimetic tortoise shell pattern geomembrane surface is provided with periodically repeating biomimetic structural units. The biomimetic structural units adopt hexagonal, quasi-hexagonal, or honeycomb topological configurations to form a continuous and regular concave-convex texture structure on the geomembrane surface; On the unit normal section, the biomimetic structural unit presents a multi-level stepped configuration, consisting of at least two levels, so that the side of the unit presents a multi-level stepped transition in the vertical direction. Adjacent levels are connected by arc-shaped transition surfaces or vertical surfaces, thereby forming a multi-level interlocking interface on the side of the unit.

[0019] As a preferred approach, two adjacent biomimetic structural units are connected by an arc-shaped transition or a planar transition. The unit depth is 0.8-1.5 mm, the side length is 4-5 mm, and the ratio of unit depth to side length is controlled between 0.2 and 0.3. The total thickness of the biomimetic tortoise shell pattern geomembrane is 2-3 mm, of which the tortoise shell pattern structural layer accounts for 45-55% of the total thickness.

[0020] As a preferred embodiment, the biomimetic tortoise shell pattern geomembrane has a reinforced grid or fiber reinforcement layer on its back side; the reinforced grid material is glass fiber, polyester fiber or carbon fiber, the grid size is 11.77 mm × 13.86 mm, the fiber reinforcement layer is bonded to the geomembrane matrix through melt co-extrusion or hot composite process, the peel strength is not less than 6 N / cm, and the tear strength of the reinforced geomembrane is increased by more than 30%.

[0021] As a preferred method, the biomimetic tortoise shell pattern geomembrane is output by a 3D printer or formed by molding or hot pressing processes; the surface uneven structure is precisely formed by mold, the mold material is stainless steel or quenched steel, and the surface finish is not less than Ra 0.8.

[0022] As a preferred embodiment, the biomimetic tortoise shell pattern geomembrane is made of a polymer material selected from one or more of high-density polyethylene (HDPE), polypropylene (PP), or polyester (PET); the formulation of the biomimetic tortoise shell pattern geomembrane contains one or more of ultraviolet stabilizers (such as HALS), antioxidants, and carbon black.

[0023] As a preferred embodiment, the biomimetic tortoise shell pattern geomembrane has a wide tensile strength ≥20 kN / m, an elongation ≥50%, and low-temperature toughness that does not crack at ≤0℃.

[0024] As a preferred method, the laying direction of the multi-layer geomembrane is the same or alternate, and the alternation is a combination of fixed angles or different angles.

[0025] As a preferred method, the thickness of each layer of calcareous sand is 10~30 cm, and the compaction degree is not less than 95%; the maximum particle size of the calcareous sand does not exceed 1 / 3 of the layer thickness, and the mass content of fine particles with a particle size less than 0.075 mm does not exceed 10%; the compaction process adopts a combination of static compaction and vibratory compaction, with low-frequency high-amplitude vibration for initial compaction and high-frequency low-amplitude vibration for final compaction.

[0026] The present invention also provides a calcareous sandy soil structure formed according to the above method, which has alternating layers of geomembrane and calcareous sand.

[0027] The aforementioned applications of calcareous sandy soil structures include reinforcement of marine foundations, island and reef platforms, slope engineering, or railway subgrades.

[0028] Invention Principle: The technical principle of this invention is based on the interdisciplinary integration of bionics, soil mechanics, materials science, and construction technology, and mainly includes the following core principles:

[0029] 1. Bionics principles

[0030] (1) Mechanical Mechanism of Tortoise Shell Structure: Stress Dispersion Principle: The hexagonal unit structure of the tortoise shell can uniformly transfer local loads to the overall structure through the unit boundaries, avoiding stress concentration. This invention uses the tortoise shell texture design to quickly disperse surface loads within the geomembrane plane, reducing local stress peaks; Deformation Coordination Mechanism: The flexible connection between tortoise shell units allows the structure to undergo moderate deformation without compromising its integrity. The tortoise shell texture structure of the geomembrane can coordinate deformation under load, avoiding brittle failure; Energy Absorption Characteristics: The multi-level structure of the tortoise shell can effectively absorb impact energy. This invention absorbs dynamic load energy through the elastic deformation of the textured structure, reducing damage to calcareous sand particles.

[0031] (2) Biological optimization mechanism: The tortoise shell structure optimized by natural selection achieves the best balance between weight and strength. This invention minimizes material usage while ensuring mechanical properties through parameter optimization. The microstructure of the tortoise shell surface provides excellent frictional properties. This invention replicates this property through surface roughness control and texture shape optimization.

[0032] 2. Principles of Soil Mechanics

[0033] (1) Reinforcement mechanism: Friction reinforcement theory: Through the interfacial friction between the geomembrane and the calcareous sand, the tensile stress in the soil is transferred to the reinforcement material, restricting the lateral deformation of the soil. The tortoise shell structure embedded in the calcareous sand significantly increases the interfacial friction coefficient and improves the reinforcement efficiency; Quasi-cohesion theory: The reinforced soil exhibits strength characteristics similar to cohesive soil. This invention forms equivalent cohesion in the calcareous sand through a layered embedding structure, thereby improving the overall strength of the soil.

[0034] (2) Constraint mechanism: Lateral constraint effect: The geomembrane layer forms a continuous lateral constraint on the calcareous sand, increasing the confining pressure of the soil and thus enhancing the shear strength. The tortoise shell pattern structure strengthens this constraint effect through mechanical interlocking; Fracture inhibition mechanism: By restricting particle movement and stress concentration, it effectively reduces the probability of calcareous sand particle fracture and maintains long-term strength.

[0035] 3. Principles of Materials Science

[0036] (1) Interface effect: Mechanical interlocking mechanism, the tortoise shell texture and calcareous sand particles form a three-dimensional interlocking system, which significantly improves the interface anti-slip ability; surface energy regulation, through material surface modification, optimizes the surface energy matching between geomembrane and calcareous sand, and enhances the interface interaction.

[0037] 4. Structural Cooperative Working Principle

[0038] (1) Load transfer path

[0039] Establish a clear load transfer system: vertical load → calcareous sand layer → geomembrane layer → adjacent calcareous sand layer, forming a continuous force transfer path. Stress redistribution mechanism: through stress diffusion in the geomembrane layer, localized concentrated loads are transformed into uniformly distributed loads, improving the bearing capacity of the foundation.

[0040] (2) Deformation coordination mechanism:

[0041] Layered deformation coordination: Each structural layer deforms in a coordinated manner under load to avoid deformation concentration. Progressive failure control: Through multi-layered structural design, a progressive failure mode of the structure is achieved, improving the safety margin.

[0042] Compared with existing methods for reinforcing calcareous sandy soil, this invention has the following advantages and outstanding effects:

[0043] 1. It combines reinforcement and seepage prevention: bearing capacity is increased by more than 30%, and settlement is reduced by more than 40%;

[0044] 2. Material durability: High-polymer geomembranes are corrosion-resistant, anti-aging, and have a long service life;

[0045] 3. Environmentally friendly and economical: No cement or other binding materials are required, reducing carbon emissions and lowering project costs;

[0046] 4. Advantages of biomimetic structure: The tortoise shell pattern design enhances the interface function and improves overall stability. Attached Figure Description

[0047] Figure 1 Top view of the biomimetic tortoise shell pattern geomembrane provided by this invention;

[0048] Figure 2 The three-dimensional image of the biomimetic tortoise shell pattern geomembrane provided by this invention includes: 1-tortoise shell indentation, 2-reinforced grid longitudinal ribs, and 3-reinforced grid transverse ribs.

[0049] Figure 3 The present invention provides a schematic diagram of a biomimetic tortoise shell pattern geomembrane reinforcing calcareous sand, wherein 4-calcareous sand and 5-geomembrane;

[0050] Figure 4 The shear stress-displacement curves of the biomimetic tortoise shell pattern geomembrane and the ordinary geomembrane provided by this invention. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0052] Example 1

[0053] This embodiment provides a method for preparing a biomimetic tortoise shell pattern geomembrane, the steps of which are as follows:

[0054] Step 1: Raw material pretreatment. HDPE resin granules are placed in a hot air drying oven and dried at 80℃ for 4 hours to remove moisture (moisture content ≤0.05%). Glass fiber mesh is preheated at 120℃ for 2 hours to eliminate internal stress.

[0055] Step 2: Mixing the ingredients. Add the dried HDPE resin, UV stabilizer, antioxidant, and carbon black to the high-speed mixer in sequence. First, mix at 600 r / min for 5 minutes, then increase the speed to 1200 r / min and mix for 10 minutes. Control the mixing temperature at 110℃ to ensure that the additives are evenly dispersed in the matrix material to form a mixture.

[0056] Step 3: Extrusion and plasticizing. The mixture is added to a twin-screw extruder. The extrusion process parameters are set as follows: Barrel zone 1 temperature: 160℃, zone 2 temperature: 180℃, zone 3 temperature: 200℃, zone 4 temperature: 210℃. Screw speed: 60 r / min, die pressure: 15 MPa, extrusion rate: 200 kg / h. After plasticizing in the extruder, the material forms a molten geomembrane matrix.

[0057] Step 4: Reinforcing layer composite. The preheated glass fiber mesh (11.77 mm × 13.86 mm) is precisely fed into the lower mold cavity of the molding machine through the guide device. Then, the molten geomembrane matrix material is evenly poured onto the surface of the mesh to ensure that the matrix material completely wets the mesh. The thickness of the composite layer is controlled at 1.3 mm (52% of the total thickness of the geomembrane).

[0058] Step 5: Bionic structure compression molding. Close the compression molding machine and set the molding parameters: molding temperature: 205℃, molding pressure: 25MPa, holding time: 8min. The hexagonal bionic structure texture preset on the mold surface is used to press a periodically repeating embossed texture onto the geomembrane surface.

[0059] Step 6: Cooling and Shaping. After molding, turn on the mold cooling system and cool the geomembrane to below 40°C at a cooling rate of 15°C / min. Keep the mold closed and maintain a constant temperature for 30 minutes to ensure the stability of the biomimetic structure and avoid shrinkage and deformation.

[0060] Example 2

[0061] The biomimetic tortoise-shell pattern geomembrane prepared according to the method provided in Example 1, such as Figure 1-2As shown, the surface of the geomembrane features periodically repeating biomimetic structural units forming anti-tortoise-shell indentations 1. These biomimetic structural units have a hexagonal topological configuration, creating a continuous and regular textured surface. On the normal cross-section of the unit, the biomimetic structural unit exhibits a multi-level stepped configuration, consisting of three layers, resulting in a three-step transition on the unit's side in the vertical direction. Adjacent layers are connected by vertical planes, thus forming a multi-level interlocking interface on the unit's side. The biomimetic structural unit has a depth of 1.2 mm and a side length of 4.5 mm, with a depth-to-side-length ratio of 0.26. Adjacent units are connected by an arc-shaped transition. The tortoise-shell textured layer is 1.2 mm thick (accounting for 48% of the total thickness), and the total geomembrane thickness is precisely controlled to 2.5 mm. The back of the biomimetic tortoise-shell textured geomembrane features intersecting reinforced longitudinal ribs 2 and reinforced transverse ribs 3.

[0062] Example 3

[0063] The method for reinforcing calcareous sandy soil using the biomimetic tortoise shell pattern geomembrane of Example 2 includes the following steps:

[0064] Step 1: Foundation treatment. First, the calcareous sandy soil foundation to be reinforced is leveled and initially compacted to ensure that the foundation is flat and free of sharp objects to prevent damage to the geomembrane.

[0065] Step 2: Lay the first layer of geomembrane. Lay the biomimetic tortoise shell pattern geomembrane on the treated substrate. When laying, the membrane surface must be kept flat and without wrinkles. If necessary, use an automatic membrane laying machine for tension adjustment and centering control.

[0066] Step 3: Lay a layer of calcareous sand. Evenly lay a layer of calcareous sand on the geomembrane, with a thickness controlled between 25 and 30 cm. After laying, perform preliminary compaction, with a compaction degree of not less than 95%.

[0067] Step 4: Repeat the laying and compaction process, alternating between the geomembrane and the calcareous sand layer. The laying direction of each geomembrane layer can be varied (e.g., orthogonal laying) to enhance the isotropy and deformation resistance of the overall structure, with a total of 3 layers laid.

[0068] Step 5: Final compaction treatment. After the top layer of calcareous sand is laid, final compaction treatment is carried out. Equipment such as vibratory rollers are used to ensure that the overall structure density meets the design requirements.

[0069] Step 6: Interface reinforcement treatment. To improve the bonding performance between the geomembrane and the calcareous sand, an interface reinforcement agent can be sprayed during the laying process to further enhance interlayer friction and anti-slip ability. The final result is as follows: Figure 3 The structure shown is an alternating superposition of geomembrane 5 and calcareous sand 4.

[0070] Characterization

[0071] The direct shear mechanical properties of the calcareous sand-bionic tortoise shell pattern geomembrane prepared in Example 2 and an ordinary geomembrane (HDPE geomembrane with a thickness of 2 mm purchased from Shandong Jiantong Engineering Technology Co., Ltd.) were tested, including the following steps:

[0072] Step 1: Shear Box Assembly and Sample Preparation: ① Secure the lower shear box to the bearing plate of the test box track using bolts. ② Lay a biomimetic tortoise-shell patterned geomembrane at the bottom of the upper shear box, securing the material with clamps to ensure no wrinkles and complete coverage of the contact surface. ③ Fill the gap between the upper and lower shear boxes with soil samples. The sample dimensions are length × width × height = 150mm × 150mm × 100mm.

[0073] Step 2: Loading and Data Acquisition: ① Apply normal stress to 100 kPa using a vertical compression bar and maintain it constant. ② Activate the horizontal push-pull bar to apply shear force at a rate of 0.1 mm / min for 30 min. ③ The data acquisition system records stress and displacement data in real time and generates stress-strain coupling curves.

[0074] Step 3: Test the interfacial direct shear mechanical properties of the calcareous sand-ordinary geomembrane using the same experimental procedures. Geomembrane technical specifications: density 0.942 g / cm³. -3 Ultimate tensile strength: 29.3 kN·m -1 Ultimate elongation: 12%.

[0075] Figure 4 The shear stress-displacement curves were automatically output using the TM2101N direct shear pull-out test software V8.71(C). As shown in the figure, the interfacial shear strength of the calcareous sand-bionic tortoise shell pattern geomembrane is 77.94 kPa, while that of the calcareous sand-ordinary geomembrane is 61.27 kPa. The interfacial shear strength of the bionic tortoise shell pattern geomembrane is 27% higher than that of the ordinary geomembrane.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A method for reinforcing calcareous sandy soil by layering and embedding based on a biomimetic tortoise-shell pattern geomembrane, characterized in that, Includes the following steps: Step 1: Lay the first layer of the biomimetic tortoise shell pattern geomembrane on the calcareous sandy soil base to be reinforced; Step 2: Lay a layer of calcareous sand on the geomembrane and compact it initially; Step 3: Repeat the above laying and compaction steps, layering the geomembrane and calcareous sand to form a layered embedded structure; Step 4: Cover the top layer with calcareous sand and perform final compaction to complete the reinforcement construction; The biomimetic tortoise shell pattern geomembrane has periodically repeating biomimetic structural units on its surface. The biomimetic structural units adopt hexagonal, near-hexagonal, or honeycomb topological configurations, forming a continuous and regular concave-convex texture structure on the geomembrane surface; On the unit normal section, the biomimetic structural unit presents a multi-level stepped configuration, consisting of at least two levels, so that the side of the unit presents a multi-level stepped transition in the vertical direction. Adjacent levels are connected by arc-shaped transition surfaces or vertical surfaces, thereby forming a multi-level interlocking interface on the side of the unit; The back of the biomimetic tortoise shell pattern geomembrane is provided with a reinforced grid or fiber reinforcement layer; The laying direction of the multiple geomembranes is the same or alternately varied.

2. The method according to claim 1, characterized in that, Adjacent biomimetic structural units are connected by an arc-shaped transition or a planar transition. The unit depth is 0.8-1.5 mm and the side length is 4-5 mm. The ratio of unit depth to side length is controlled between 0.2 and 0.

3. The total thickness of the biomimetic tortoise shell pattern geomembrane is 2-3 mm, of which the tortoise shell pattern structural layer accounts for 45-55% of the total thickness.

3. The method according to claim 1, characterized in that, The reinforcing mesh material is glass fiber, polyester fiber, or carbon fiber, with a mesh size of 11.77 mm × 13.86 mm. The fiber reinforcement layer is bonded to the geomembrane matrix through melt co-extrusion or hot composite process, with a peel strength of not less than 6 N / cm. The tear strength of the reinforced geomembrane is increased by more than 30%.

4. The method according to claim 1, characterized in that, The biomimetic tortoise shell pattern geomembrane is output by a 3D printer or formed by molding or hot pressing processes; the surface concave and convex structure is formed by precision machining of molds, the mold material is stainless steel or quenched steel, and the surface finish is not less than Ra 0.

8.

5. The method according to claim 1, characterized in that, The biomimetic tortoise shell pattern geomembrane is made of a high molecular polymer material, which is selected from one or more of high-density polyethylene (HDPE), polypropylene (PP), or polyester (PET); the preparation formula of the biomimetic tortoise shell pattern geomembrane contains one or more of ultraviolet stabilizers, antioxidants, and carbon black.

6. The method according to claim 1, characterized in that, The biomimetic tortoise shell pattern geomembrane has a wide tensile strength ≥20 kN / m, an elongation ≥50%, and low-temperature toughness that does not crack at ≤0℃.

7. The method according to claim 1, characterized in that, The alternation can be a fixed angle or a combination of different angles.

8. The method according to claim 1, characterized in that, The thickness of each layer of calcareous sand is 10-30 cm, and the compaction degree is not less than 95%. The maximum particle size of the calcareous sand does not exceed 1 / 3 of the layer thickness, and the mass content of fine particles with a particle size less than 0.075 mm does not exceed 10%. The compaction process adopts a combination of static compaction and vibratory compaction. The initial compaction adopts low-frequency high-amplitude vibration, and the final compaction adopts high-frequency low-amplitude vibration.

9. A calcareous sandy soil structure formed by the method according to claim 1, characterized in that, It has alternating layers of geomembrane and calcareous sand.

10. An application of the calcareous sandy soil structure according to claim 9, characterized in that, The applications include reinforcement of marine foundations, island and reef platforms, slope engineering, or railway subgrades.

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