Bionic fish reef suitable for coral planting and composite forming method thereof

Abstract

The application provides a kind of bionic fish reef suitable for coral planting and its composite forming method, belonging to the technical field of marine ecological restoration.The bionic fish reef comprises a lower supporting structure and an upper main body structure located above the lower supporting structure.The lower supporting structure comprises a bearing disc and a supporting column, and the bearing disc and the supporting column are integrally casted into a concrete structure.The upper main body structure is a concrete structure printed and formed layer by layer on the bearing disc, comprising an internal spiral bionic inner core fixed to the bearing disc.The internal spiral bionic inner core is vertically spirally raised from the outside to the center, and gaps are reserved between adjacent vertical spiral structures thereof.Coral planting holes for inserting and fixing coral broken branches are formed on the bearing disc.The bionic fish reef can solve the problems of traditional casted artificial fish reefs, such as small attachment surface, and the difficulty of forming a suspended structure by simply 3D printing.The bionic fish reef has sufficient surface area and can adapt to the growth needs of corals, and the whole is easy to manufacture.

Description

Technical Field

[0001] This invention relates to the field of marine ecological restoration technology, and in particular to a biomimetic artificial reef suitable for coral colonization and its composite molding method. Background Technology

[0002] To restore coral reef ecosystems severely degraded by global climate change and human activities, deploying artificial reefs in damaged waters as attachment sites for coral larvae or cultivation beds for coral fragments has become a research hotspot in the field of marine ecological restoration. These artificial reefs not only need to provide a stable and rough substrate for planktonic coral larvae, but also need to create a suspended cultivation environment for transplanted coral fragments, free from sediment burial and predator infestation. Therefore, developing biomimetic reefs with high structural complexity, large specific surface area, and excellent biocompatibility is crucial for improving coral colonization success rates and accelerating reef ecological succession.

[0003] In existing technologies, artificial reefs are mostly constructed by assembling steel templates into molds, which are then demolded after being poured, vibrated, and cured with concrete. This method is mature and suitable for large-scale production. In recent years, concrete 3D printing technology has also been gradually applied to the manufacture of artificial reefs. It uses CNC nozzles to extrude cementitious materials layer by layer, and can directly construct reef structures with internal holes, biomimetic curved surfaces, and complex topological morphology without the need for solid templates.

[0004] However, the single concrete casting process is limited by the disassembly of the mold and the draft angle, making it difficult to form biomimetic reef shapes with extremely high structural complexity, high specific surface area and naturally rough surface. It often requires post-processing or sacrificing additional materials to obtain a slightly rough surface that is conducive to larval attachment, which limits the improvement of biological attachment performance. While concrete 3D printing technology can break through the constraints of the mold on the shape and form a fine porous structure, its layer-by-layer molding method makes it difficult to print composite functional reefs that simultaneously meet the requirements of bottom support stability (such as anti-tipping extended base or counterweight) and suspended support platform (such as a horizontal cultivation bed detached from the seabed) in one go. The suspended parts are prone to collapse and deformation under unsupported conditions. If additional temporary supports are printed or modular assembly is used, the manufacturing difficulty will be significantly increased. Summary of the Invention

[0005] This invention provides a biomimetic artificial reef suitable for coral colonization and its composite molding method, solving the problems of limited attachment surface in traditional cast-in-place artificial reefs and the difficulty of forming suspended structures using only 3D printing. This allows the reef to have sufficient surface area, adapt to the growth needs of corals, and is simple to manufacture overall. The technical solution is as follows: In a first aspect, embodiments of the present invention provide a biomimetic artificial reef suitable for coral colonization, comprising: a lower support structure and an upper main structure located above the lower support structure; The lower support structure includes a bearing disk and a support column connected below the bearing disk, and the bearing disk and the support column are integrally cast concrete structures. The upper main structure is a concrete structure printed layer by layer on the supporting disk and fixed to the supporting disk. It includes an inner spiral bionic core fixed to the supporting disk. The inner spiral bionic core rises vertically from the outside to the center, and there is a gap between adjacent vertical spiral structures. The gap forms a hollow channel that runs vertically through the inner spiral bionic core. The supporting disc has coral planting holes for inserting and fixing coral fragments.

[0006] Optionally, the bottom diameter of the outermost ring of the inner spiral bionic core is 50% to 60% of the diameter of the supporting disk, and the gap between adjacent vertical spiral structures ranges from 10 to 20 mm. Optionally, the upper main structure further includes an inner enclosure structure surrounding the outer side of the inner spiral bionic core, and an outer enclosure structure located outside the inner enclosure structure. Both the inner enclosure structure and the outer enclosure structure are erected on the supporting disk to form a double-layer protective structure, and an annular drainage groove is formed between the inner enclosure structure and the inner spiral bionic core. Optionally, the projection of the outer enclosure structure onto the supporting disk is wavy, and the height of the inner enclosure structure is lower than the height of the outer enclosure structure. Optionally, multiple coral planting holes are evenly spaced around the circumference of the supporting disc, and all are located between the inner enclosure structure and the outer enclosure structure. Optionally, the bearing disc is further provided with permeable holes that penetrate its thickness. Some of the permeable holes are aligned and connected with the hollow channel, and some of the permeable holes are aligned and connected with the annular drainage groove. The diameter of the permeable holes ranges from 8 to 12 mm. Optionally, the bearing disc has a built-in bidirectional steel mesh, the thickness of the bearing disc is in the range of 200 to 300 mm, and the diameter is in the range of 1500 to 2000 mm; multiple supporting columns are provided and are evenly spaced along the edge of the bearing disc. Optionally, the coral planting hole is a blind hole that does not penetrate the supporting disc, and the hole diameter ranges from 8 to 12 mm, and the hole depth is 1 / 3 to 1 / 2 of the thickness of the supporting disc.

[0007] Secondly, embodiments of the present invention provide a composite molding method based on the aforementioned first aspect for realizing a biomimetic artificial reef suitable for coral colonization, comprising: S1. The lower support structure is integrally formed by concrete casting. The lower support structure includes the bearing disc and the support column located below the bearing disc, and the coral planting hole is formed on the bearing disc. S2. The upper surface of the formed support disk is roughened, cleaned, and pre-wetted, and while it remains surface-dry and moist, a low-alkali interface slurry of the same system as the printing material is applied. Before the interface slurry initially sets, a low-alkali 3D printing cement-based material is used, and multi-turn continuous printing is performed on the entire cross-section based on a single-layer height to form the upper main structure layer by layer, and the upper main structure is fixedly connected to the support disk. The upper main structure includes an internal spiral biomimetic core, which extends inward layer by layer along the Archimedean spiral curve, and the starting point of each spiral path moves forward by a displacement S relative to the previous layer along the path direction. The displacement S satisfies S=L / N, where L is the circumference of a single turn of the bottom spiral, N is the total number of printed layers of the internal spiral biomimetic core, and S is not greater than half of the print head linewidth W.

[0008] Optionally, the supporting disc (11) is also formed with permeable holes that penetrate its thickness. The permeable holes and the coral planting holes are formed in different ways: the permeable holes are directly formed by forming protrusions provided on the bottom plate of the casting mold, and the height of the forming protrusions is equal to the casting thickness of the supporting disc; the coral planting holes are formed by independent short rods, that is, before the supporting disc is cast and the concrete is initially set, the independent short rods are vertically inserted into the concrete from the upper surface of the supporting disc, and the independent short rods are pulled out after the concrete is initially set and before it is finally set, thereby forming blind holes that do not penetrate the supporting disc.

[0009] The beneficial effects of the technical solutions provided by the embodiments of the present invention include at least the following: By integrating the lower support structure with the upper main structure through the bonding and consolidation between the cast-in-place and printed structures, the load-bearing and wave-resistant advantages of cast-in-place technology and the biomimetic advantages of 3D printing technology are combined. In this way, the shortcomings of traditional cast-in-place artificial reefs, such as simple shape, smooth surface, few attachment surfaces, and difficulty in forming complex biomimetic topological structures, are overcome. It also solves the problem that it is difficult to form a composite reef with both bottom support stability and upper suspended support platform in one go by 3D printing, and the problem that the suspended part is prone to collapse and deformation. Moreover, the overall production is simple. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a three-dimensional structural schematic diagram of a biomimetic artificial reef suitable for coral colonization provided in an embodiment of the present invention; Figure 2 This is a top view structural diagram of a biomimetic artificial reef suitable for coral colonization provided in an embodiment of the present invention; Figure 3 This is a front view structural diagram of a biomimetic artificial reef suitable for coral colonization provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the lower support structure provided in an embodiment of the present invention; Figure 5 This is a flowchart of the composite molding method provided in the embodiments of the present invention.

[0012] In the diagram: 1-Lower support structure; 2-Upper main structure; 11-Bearing disc; 12-Supporting column; 21-Internal spiral bionic core; 211-Hollowed channel; 22-Inner enclosure structure; 23-Outer enclosure structure; 24-Annular drainage channel; 111-Coral planting hole; 112-Permeable hole; 113-Two-way steel mesh. Detailed Implementation To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0013] refer to Figures 1 to 4This invention provides a biomimetic artificial reef suitable for coral colonization. The reef has a longitudinal vertical structure and employs a partitioned composite molding method with a cast-in-place load-bearing lower section and a 3D-printed biomimetic upper section. It includes a lower support structure 1 and an upper main structure 2 located above the lower support structure 1. The lower support structure 1 is a monolithically cast concrete structure that forms the load-bearing base of the reef. The upper main structure 2 is a concrete structure that is stacked and printed layer by layer on the support disc 11 of the lower support structure 1, forming the biomimetic functional body of the reef and is fixedly connected to the support disc 11. The lower support structure 1 and the upper main structure 2 are integrated by bonding and solidifying the cast-in-place structure and the printed structure, thus combining the load-bearing and wave-resistant advantages of cast-in-place technology with the biomimetic advantages of 3D printing technology. In this way, it not only overcomes the shortcomings of traditional cast-in-place artificial reefs, such as simple shape, smooth surface, few attachment surfaces, and difficulty in forming complex biomimetic topological structures, but also solves the problem that it is difficult to form a composite reef with both bottom support stability and upper suspended support platform in one go by simply using 3D printing, and the problem that the suspended part is prone to collapse and deformation. Moreover, the overall production is simple.

[0014] Specifically, the lower support structure 1 includes a bearing disc 11 and a support column 12 connected below the bearing disc 11, and the bearing disc 11 and the support column 12 are integrally cast concrete structures. The bearing disc 11 is horizontally set as the basic load-bearing platform of the reef, and the support column 12 extends downward from the bottom surface of the bearing disc 11, supporting and lifting the bearing disc 11 above the seabed; the integral casting of the two avoids splicing interfaces, making the lower support structure 1 a continuous and stable integral load-bearing base, fundamentally ensuring the reef's resistance to subsidence and overturning on the seabed.

[0015] Furthermore, the supporting disc 11 incorporates a bidirectional steel mesh 113. The thickness of the supporting disc 11 ranges from 200 to 300 mm, and its diameter ranges from 1500 to 2000 mm. The bidirectional steel mesh 113 is laid crosswise in both longitudinal and transverse directions within the supporting disc 11, significantly improving its flexural and shear strength. This allows it to possess both good structural rigidity and toughness under complex sea conditions, overcoming the drawbacks of traditional cast-in-place artificial reefs with weak wave resistance. Limiting the thickness of the supporting disc 11 to 200 to 300 mm and its diameter to 1500 to 2000 mm ensures the necessary rigidity for the supporting disc 11 as the core supporting platform while also considering the overall quality of the reef, material economy, and ease of deployment. Preferably, the supporting disc 11 is cast-in-place using low-alkalinity concrete with an embedded steel mesh, requiring a smooth, dense surface free of honeycomb pits to ensure reliable bonding of the subsequent upper main structure 2.

[0016] Furthermore, multiple support columns 12 are provided, evenly spaced along the edge of the bearing disc 11. The support columns 12 and the bearing disc 11 are integrally cast and arranged at equal angles around the bottom center of the bearing disc 11, and both share the impact of ocean currents and structural loads. The support columns 12 enhance the base's resistance to settlement and overturning, preventing the reef from shifting under strong ocean currents; on the other hand, they form a water passage space below the bearing disc 11, facilitating the flow of nutrient-rich and dissolved oxygen-rich seawater from the bottom up into the reef's interior. In an optional embodiment of the invention, the number of support columns 12 is four, with a diameter of 40 to 100 mm and a height of 30 to 100 mm. Furthermore, the number and size of the support columns 12 can be adjusted according to the seabed composition and sea conditions of the deployment area. For example, for pure muddy seabeds with weak bearing capacity, the number of support columns 12 can be increased to six to eight, and their diameter and height can be increased accordingly to adapt to the characteristics of different seabed compositions in nearshore areas.

[0017] The upper main structure 2 includes an internal spiral bionic core 21 fixed to a supporting disc 11. The internal spiral bionic core 21 rises vertically from the outside to the center, and its bottom is directly bonded to the upper surface of the supporting disc 11, with its root firmly seated on the supporting disc 11 without being suspended or loose. Gaps are reserved between adjacent vertical spiral structures of the internal spiral bionic core 21, forming a hollow channel 211 that runs vertically through the internal spiral bionic core 21. The hollow channel 211 runs vertically through the core, ensuring smooth flow of seawater and forming a stable circulation within the core, while also significantly increasing the specific surface area of ​​the core, providing an excellent space and flow field environment for coral attachment and three-dimensional growth.

[0018] Furthermore, the outermost diameter of the inner spiral bionic core 21 is 50% to 60% of the diameter of the supporting disk 11, and the gap between adjacent vertical spiral structures ranges from 10 to 20 mm. Limiting the outermost diameter of the inner core to 50% to 60% of the diameter of the supporting disk 11 provides sufficient solid base for the inner core in the middle of the supporting disk 11 to ensure the root consolidation strength, while also retaining sufficient annular space around the inner core to accommodate the annular drainage groove 24 and the inner and outer protective structures. Limiting the gap between adjacent vertical spiral structures to 10 to 20 mm ensures smooth water flow in the hollow channel 211 while avoiding excessively large gaps that would cause the spiral components to lose interlayer constraints and affect molding stability, or excessively small gaps that would cause channel blockage and weaken water circulation efficiency and adhesion space. In an optional embodiment of the present invention, the overall height of the inner spiral biomimetic core 21 is 900 to 1000 mm, and its top is higher than the inner enclosure structure 22 and the outer enclosure structure 23, so that the coral can obtain different lighting and flow field conditions at different heights of the inner core.

[0019] Furthermore, the upper main structure 2 also includes an inner enclosure structure 22 surrounding the inner spiral biomimetic core 21, and an outer enclosure structure 23 located outside the inner enclosure structure 22. Both the inner enclosure structure 22 and the outer enclosure structure 23 are erected on the supporting disc 11, and are arranged radially at intervals to form a double-layer protective structure. This enhances the overall structural stability of the reef and guides and reduces the incoming flow layer by layer, preventing excessive impact of turbulent water on the coral body. An annular drainage channel 24 is formed between the inner enclosure structure 22 and the inner spiral biomimetic core 21. The annular drainage channel 24 is a ring-shaped clear space surrounding the outer side of the inner spiral biomimetic core 21. After molding, it remains absolutely clear and free from printing slurry blockage, serving as a crucial flow field acceleration space to ensure rapid water circulation and enhance the water exchange capacity inside the reef. In an optional embodiment of the invention, the span of the annular drainage channel 24 is 10% to 20% of the diameter of the supporting disc 11.

[0020] Furthermore, the projection of the outer protective structure 23 onto the supporting disk 11 is wavy, and the height of the inner protective structure 22 is lower than that of the outer protective structure 23. The wavy projection profile of the outer protective structure 23 can increase the disturbance and guiding effect on its upstream surface, reducing the impact of the ocean current, providing an energy dissipation shelter for the internal corals, and guiding the water flow to form a circulation. Setting the height of the inner protective structure 22 to be lower than that of the outer protective structure 23 allows the outer protective structure 23 to undertake the main upstream energy dissipation function, while the inner protective structure 22 forms a second-level buffer and guide on its inner side. The two work together to form a flow velocity gradient that gradually decreases from the outside to the inside, further protecting the coral branches from being broken by strong currents. In an optional embodiment of the present invention, the overall height of the outer protective structure 23 is 400 to 500 mm, and the overall height of the inner protective structure 22 is 200 to 250 mm.

[0021] The supporting disc 11 has coral planting holes 111 for inserting and fixing coral fragments. These holes allow for direct insertion and fixing of coral fragments without the need for chemical adhesives such as epoxy resin, thus avoiding water pollution and achieving convenient, pollution-free, and efficient planting. This method is also suitable for the growth and fixation needs of various branched corals. Furthermore, multiple coral planting holes 111 are evenly spaced around the circumference of the supporting disc 11, all located within the disc area between the inner and outer protective structures 22 and 23. Placing the coral planting holes 111 between the inner and outer protective structures 22 places the inserted coral fragments within an energy-dissipating protective zone formed by the double-layered protective structure. The gradual reduction of ocean currents by the inner and outer protective structures lowers the impact of strong currents on the coral fragments, preventing breakage during typhoons.

[0022] Furthermore, the coral planting hole 111 is a blind hole that does not penetrate the supporting disc 11, with a diameter ranging from 8 to 12 mm and a depth of 1 / 3 to 1 / 2 of the thickness of the supporting disc 11. The coral planting hole 111 adopts a blind hole structure that does not penetrate the supporting disc 11, and its bottom is sealed by the cast-in-place concrete of the supporting disc 11. This effectively avoids the localized mechanical weakening caused by the full thickness penetration of the supporting disc 11, while ensuring direct insertion and glue-free fixation of the coral fragment. This achieves a balance between convenient planting and foundation bearing strength. Limiting the hole diameter to 8 to 12 mm and the hole depth to 1 / 3 to 1 / 2 of the thickness of the supporting disc 11 matches the size of common branched coral fragments, ensuring the stability of the coral fragment after insertion.

[0023] Optionally, the supporting disc 11 is also provided with permeable holes 112 that penetrate its thickness. Some of the permeable holes 112 are aligned and connected to the hollow channel 211, and some of the permeable holes 112 are aligned and connected to the annular drainage groove 24. The diameter of the permeable holes 112 ranges from 8 to 12 mm. The permeable holes 112 penetrate the thickness of the supporting disc 11, opening up the water circulation path between the bottom of the reef and the interior: the permeable holes 112 aligned and connected to the hollow channel 211 can introduce the bottom seawater that enters through the lifting space of the supporting column 12 from bottom to top into the hollow channel 211 of the inner spiral bionic core 21; the permeable holes 112 aligned and connected to the annular drainage groove 24 can introduce the bottom seawater into the flow field acceleration space of the annular drainage groove 24. Therefore, the permeable holes 112, in conjunction with the hollowed-out channels 211 and the annular drainage channels 24, form a fully connected vertical water circulation channel inside the reef, ensuring the smooth upward transport of seawater and bottom nutrients, significantly improving the efficiency of dissolved oxygen and nutrients transport to the coral colonization area, and solving the problem of existing artificial reefs lacking a fully connected water circulation structure and insufficient nutrient exchange. Preferably, the permeable holes 112 that are aligned and connected with the hollowed-out channels 211 are aligned with the orthographic projection area of ​​the vertical hollowed-out channels of the inner spiral biomimetic core 21, and their axial alignment error is controlled within 5mm to eliminate the step effect at the edge of the holes and ensure the continuous and smooth flow of water.

[0024] Based on the above structure, the working principle of the biomimetic artificial reef provided in this embodiment of the invention is as follows: After the reef is deployed, the supporting column 12 lifts the bearing disk 11 and supports it stably on the seabed. Seawater rich in nutrients and dissolved oxygen at the bottom enters from below the bearing disk 11 and enters the interior of the reef from bottom to top through the permeable holes 112 that are aligned and connected with the hollow channel 211 and the annular diversion channel 24. The vertical spiral rising structure of the internal spiral biomimetic core 21 guides the upward water flow to form a stable spiral circulation, and the annular diversion channel 24 serves as the flow channel. The field acceleration space further accelerates the water circulation, while the outer protective structure 23 and the inner protective structure 22 gradually reduce the impact of the ocean current on the outside and form an energy dissipation shelter zone. In this way, nutrients and dissolved oxygen are efficiently transported to the coral fragments inserted into the coral planting holes 111. Combined with the rough attachment surface and three-dimensional attachment space provided by the internal spiral biomimetic core 21 and each protective structure, a suitable light, flow field and nutrient environment is created for the attachment of coral planktonic larvae and the branching growth of coral fragments, thereby significantly improving the survival rate of coral planting.

[0025] In this embodiment of the invention, based on the functional differences of each component, low-alkalinity concrete materials with different proportions are selected for the lower support structure 1 and the upper main structure 2, in order to balance the load-bearing durability of the base, the printability of the upper biomimetic components, and the biocompatibility of coral attachment. For a cast-in-place bearing disc 11 and supporting column 12, marine engineering-specific low-alkalinity sulfoaluminate high-performance concrete is used. Its cementitious material is composed of low-alkalinity sulfoaluminate cement L-SAC, refined slag powder, low-calcium fly ash, and silica fume, preferably in a mass percentage of 60:25:10:5. The aggregate is medium sand and continuously graded crushed stone with a particle size of 5 to 10 mm, with a sand ratio controlled at 28% to 34% and a water-cement ratio controlled at 0.33 to 0.36. Polycarboxylate superplasticizer at 0.8% to 1.2% of the cementitious material mass and 0.6 to 0.9 kg / m³ are added. 3 The material is made of polypropylene fiber. This cast-in-place material has low alkali release, early strength, resistance to shrinkage cracking and chloride salt corrosion. The 28-day compressive strength after hardening is not less than 35 MPa. The compressive strength loss rate of the standard specimen with the same mix ratio after immersion in seawater for 6 months is not greater than 5%. It can ensure the bearing stiffness of the support column 12 to the upper structure and the anti-settlement and anti-overturning self-stabilizing ability of the support disk 11 under the complex flow field of the seabed.

[0026] For the 3D-printed internal spiral biomimetic core 21, inner enclosure structure 22 and outer enclosure structure 23, a low-alkalinity 3D printing cement-based material for marine engineering is used. The 3D printing material cementitious system is composed of low-alkalinity sulfoaluminate cement L-SAC, slag powder, low-calcium fly ash, silica fume and calcium carbonate micro powder or washed and crushed shell powder, and fine-grained quartz sand or calcium carbonate sand is used as printing aggregate.

[0027] The cementitious material comprises 55% to 65% of its total mass, low-alkalinity sulfoaluminate cement, 18% to 28% slag powder, 5% to 12% low-calcium fly ash, 4% to 8% silica fume, and 3% to 8% calcium carbonate powder or shell powder. Preferably, the mass ratio of low-alkalinity sulfoaluminate cement, slag powder, low-calcium fly ash, silica fume, and calcium carbonate powder is 60:22:8:5:5. The sand-to-binder ratio of the printing material is controlled at 1.05 to 1.15, and the water-to-binder ratio is controlled at 0.29 to 0.34. It is also used in conjunction with polycarboxylate superplasticizer, thixotropic agent, a small amount of retarder and setting regulator, and 0.1% to 0.2% by volume of chopped basalt fiber or PVA fiber. This ensures the material has continuous extrudability during the pumping stage, rapidly recovers its yield stress after exiting the nozzle, and possesses constructability. The 28-day compressive strength of the printed material is no less than 40 MPa. After 30 days of seawater pre-curing, the pH value of the surface leachate stabilizes at 8.2 to 8.8, thus providing an attachment matrix for coral planktonic larvae and larvae that is closer to the natural seawater environment. The compressive strength loss rate of the standard specimen with the same ratio after immersion in seawater for 6 months is no more than 5%, which can meet the long-term durability requirements of complex biomimetic geometric structures such as the internal spiral biomimetic core 21.

[0028] refer to Figure 5 This invention also provides a composite molding method based on the aforementioned biomimetic artificial reef suitable for coral colonization. This method employs a composite process combining cast-in-place and 3D continuous printing, following the sequence of cast-in-place, interface treatment, trial extrusion calibration, single-layer full-section continuous 3D printing, moisture retention and curing, seawater acclimatization, and deployment. The cast-in-place portion uses concrete pouring equipment, while the 3D printing portion uses a concrete 3D continuous extrusion printer. The printer's core printing parameters are set as follows: nozzle linewidth 20 to 40 mm, printing layer thickness 4.5 to 8 mm, nozzle moving speed 35 to 90 mm / s, and the return time between adjacent layers of the same component is no more than one-third of the material's printable open time, preferably no more than 8 minutes. Furthermore, the equipment control system supports customized Archimedes spiral paths, closed enclosure trajectories, extrusion start / stop compensation, empty-run crossing, and hole avoidance programming. Before formal printing, continuous trial extrusion with a length of no less than 1 m and stacking tests of no less than 6 layers are conducted to confirm that the strips do not segregate, bleed water, or collapse before the upper main structure 2 is formed. The composite molding method specifically includes the following steps.

[0029] S1: The lower support structure 1 is integrally formed by concrete casting. The lower support structure 1 includes a bearing disc 11 and a support column 12 located below the bearing disc 11. Coral planting holes 111 and permeable holes 112 penetrating the bearing disc 11 are formed on the bearing disc 11.

[0030] Specifically, this step uses a special cast-in-place mold with a full-height protrusion integrally machined on the base plate. The vertical height of the full-height protrusion is equal to the total thickness of the cast-in-place bearing disc 11, used to directly form permeable holes 112 that penetrate the thickness of the bearing disc 11. At the same time, the bottom of the mold has a cavity for forming the support column 12. During construction, the bidirectional steel mesh 113 is first precisely placed in the mold, and the positions of the subsequently formed coral planting holes 111 and permeable holes 112 are kept away from the steel mesh skeleton. Then, the aforementioned low-alkalinity sulfoaluminate high-performance concrete is used to cast the support column 12 and the bearing disc 11 with the built-in bidirectional steel mesh 113 as a whole and vibrate it to ensure that there are no cracks and no grout leakage.

[0031] In this step, the permeable holes 112 and the coral planting holes 111 are formed in different ways: the permeable holes 112 are directly formed by the full-height forming protrusions set on the bottom plate of the cast-in-place mold. The height of the forming protrusions is equal to the casting thickness of the supporting disc 11, thus forming a permeable through hole that penetrates the thickness of the supporting disc 11 after demolding; the coral planting holes 111 are formed by independent short rods. That is, after the supporting disc 11 is cast and before the concrete initially sets, the independent short rods are vertically inserted into the concrete from the upper surface of the supporting disc 11 according to the design coordinates. The consistency of the concrete before initial setting is used to naturally position and support the independent short rods, so that the bottom end does not touch the bottom plate of the mold and a layer of concrete is left between the bottom end and the bottom plate of the mold, thus ensuring that the coral planting holes 111 do not penetrate the supporting disc 11; after the concrete reaches initial setting and before final setting, the independent short rods are vertically pulled out, thus forming blind holes on the supporting disc 11 that do not penetrate the supporting disc 11. By using the aforementioned differentiated hole-forming method, the permeable holes 112 that are fully connected and the non-connected coral planting holes 111 are precisely formed separately in the same casting process. This ensures that the permeable holes 112 have a clear and unobstructed cross-section to build a water circulation path, while the coral planting holes 111 form a continuous and dense blind hole at the bottom to take into account both the insertion fixation and the foundation bearing strength. This solves the problem that traditional mold casting is difficult to accurately form both through holes and blind holes on the same component at the same time.

[0032] After the entire cast-in-place base reaches the specified demolding strength, demolding is typically performed 12 to 24 hours after casting, allowing the full-height molding protrusion of the mold base plate to automatically retract. Subsequently, the base with differentiated pores is placed in a standard curing environment, such as a temperature of 20±2℃ and relative humidity ≥95%, for pre-curing. Ideally, the upper 3D printing should be performed 3 to 7 days after casting, when the base's compressive strength is not less than 20MPa, to preserve the wet bonding ability of the new and old material interfaces. If printing is required after 28 days or longer due to construction organization needs, mechanical interlocking measures such as roughening, interface slurry, shallow grooves, or shear keys should be strengthened. Before printing, ensure that the permeable holes 112 are clear and unobstructed across their entire cross-section, and that the coral planting holes 111 form a blind hole structure with a depth of 1 / 3 to 1 / 2 the thickness of the supporting disc 11 and a closed, dense bottom.

[0033] After curing to the required standards and before proceeding with the upper 3D printing, a high-pressure air gun and brush are used to clean the laitance and debris from the top surface of the support disk 11. The upper surface is then lightly roughened or textured to create a uniformly rough interface. The upper surface of the support disk 11 can also be pre-set with annular shallow grooves, radial shallow grooves, or shear keys. The shallow grooves are 5 to 10 mm deep, 20 to 40 mm wide, and spaced 80 to 150 mm apart to allow the first layer of printing material to embed and form a mechanical interlock. Subsequently, the surface is pre-wetted with water until it is surface-dry, and then a 2 to 3 mm thick layer of low-alkali interface slurry from the same system is applied. The interface slurry is composed of printing cementitious material, fine sand, water, and a water-reducing agent, with a water-to-binder ratio slightly higher than that of the printing material to improve the wetting and interlocking effect between the first layer of printing strips and the cast-in-place support disk 11. Based on the design coordinates of the vertical hollow channel 211 of the internal spiral bionic core 21, the positions of the coral planting holes 111 and permeable holes 112 that have been pre-formed in the in-situ casting stage are precisely checked. It is strictly ensured that the boundary of the permeable hole 112 that is aligned and connected with the hollow channel 211 is precisely aligned with the orthographic projection area of ​​the vertical hollow channel of the internal spiral bionic core 21, and the axial alignment error is controlled within 5mm, so as to eliminate the step effect of the hole edge, thereby opening up the whole-area water circulation channel between the bottom of the reef and the interior, and ensuring the smooth upward transport of nutrients from the bottom layer.

[0034] S2: The upper surface of the formed support disk 11 is roughened, cleaned, and pre-wetted. While maintaining a surface-dry, moist state, a low-alkali interface slurry of the same system as the printing material is applied. Before the interface slurry initially sets, a low-alkali 3D printing cement-based material is used, and continuous multi-turn printing is performed across the entire cross-section based on a single-layer height to form the upper main structure 2 layer by layer, and to fix the upper main structure 2 to the support disk 11. The upper main structure 2 includes an internal spiral biomimetic core 21, which extends inward layer by layer along an Archimedean spiral curve. The starting point of each spiral path is shifted forward by a displacement S relative to the previous layer along the path direction, eventually accumulating to form a spiral core 21. Figures 1 to 3 The spiral three-dimensional structure is formed. The displacement S satisfies S=L / N, where L is the circumference of a single turn of the bottom spiral, N is the total number of printed layers of the inner spiral bionic core 21, and S is not greater than half of the print nozzle line width W; during the printing process, the areas corresponding to the coral planting hole 111 and the water permeable hole 112 are avoided.

[0035] Specifically, in this step, the 3D concrete continuous extrusion printer is started, and the nozzle line width, layer thickness, extrusion volume, and movement speed are calibrated to ensure that the actual width error of the printed strip does not exceed ±5% of the set value. While the interface slurry remains wet and bonded, one to two bottom locking layers are printed at a lower speed. The extrusion volume of the bottom locking layer is increased by 5% to 10% compared to the conventional layer. This layer is used to fill the slightly rough grooves on the surface of the bearing disc 11 and enhance mechanical interlocking. The bottom locking layer and subsequent printed layers should avoid the blank areas of the coral planting hole 111, the permeable hole 112, and the annular drainage groove 24.

[0036] Subsequently, a full-section multi-turn continuous printing process based on a single-layer height is used to construct the upper main structure 2. Specifically, within the current i-th layer height, the printhead first executes the i-th layer path printing of the inner spiral bionic core 21, continuously extruding and forming it from the outside to the inside along the Archimedean spiral curve; after completing the single-layer path of the inner core, the printhead performs extrusion stop compensation and performs Z-axis safe micro-lifting and empty-run crossing, crossing the clearance area corresponding to the annular drainage groove 24, reaching the starting coordinates of the inner enclosure structure 22; then, extrusion resumes and continuously completes the closed shell path printing of the inner enclosure structure 22 and the outer enclosure structure 23 in the i-th layer, so that the inner and outer enclosure structures form a wet continuous bonding in the same layer. After the cross-sectional paths of each designed component in the i-th layer are printed, the printer control system drives the printhead to lift the entire printhead by one printing layer thickness H and enters the full-section continuous printing of the (i+1)-th layer.

[0037] During the continuous printing process of a single layer across the entire cross section, the inner enclosure structure 22, the outer enclosure structure 23, and the inner spiral bionic core 21 participate in the printing of their respective layers according to their designed heights: when the Z-axis height does not exceed the designed height of the inner enclosure structure 22, the inner core, inner enclosure structure 22, and outer enclosure structure 23 are printed sequentially on the same layer; when the Z-axis height exceeds the designed height of the inner enclosure structure 22 but not the designed height of the outer enclosure structure 23, the path of the inner enclosure structure 22 is closed, and only the inner core and outer enclosure structure 23 are printed continuously on the same layer; when the Z-axis height exceeds the designed height of the outer enclosure structure 23, only the inner spiral bionic core 21 continues to be printed until the preset total height. This avoids instability caused by the one-time accumulation of height in a single area and allows adjacent layers of the same component to complete wet bonding within the material open time, reducing cold seam defects.

[0038] When printing the inner enclosure structure 22, a continuous annular drainage groove 24 is reserved between the inner enclosure structure 22 and the inner spiral bionic core 21. This annular drainage groove 24, as an independent hydrodynamic channel structure, must be kept completely empty to prevent slurry intrusion or blockage. When printing the outer enclosure structure 23, it is constructed layer by layer according to the designed radial spacing or local connecting rib positions, so that the outer enclosure structure 23 and the inner enclosure structure 22 together form a double-layer energy dissipation and protection system without blocking the annular drainage groove 24. When printing the inner spiral bionic core 21, a uniform gap of 10 to 20 mm is maintained between adjacent vertical spiral components to prevent the components from sticking, contacting, or adhering, thereby forming a full-area vertical hollow channel 211 that runs through the entire inner spiral bionic core 21.

[0039] After completing each closed path or zone switching path, the nozzle performs extrusion start-stop compensation, Z-axis safety lifting, and no-load crossing operations. During no-load crossing, the net distance between the bottom surface of the nozzle and the highest point of the formed part is not less than 20mm, and the outer net clearance trajectory is preferred to pass through, so as to avoid disturbing the internal spiral bionic core 21 and the annular drainage groove 24 area, and to ensure that the annular drainage groove 24 always remains in a net clearance state.

[0040] Throughout the printing process of the upper main structure 2, the nozzle must strictly avoid the blank areas corresponding to the coral planting holes 111 and the water permeable holes 112 on the supporting disc 11. If necessary, removable temporary plugs can be set at the hole openings or software-controlled no-print zones can be used to prevent the slurry from collapsing into the holes. After the adjacent printed layers have initially set, the temporary plugs should be removed, and any small amount of overflow at the hole openings should be cleaned up in a timely manner to ensure that the hole boundaries are regular and the water flow channels are unobstructed.

[0041] After printing to the preset total height, stop the operation and immediately perform misting moisturization and covering maintenance on the upper main structure 2. Avoid strong winds, direct sunlight, and direct water rinsing for the first 24 hours. Then continue to maintain the structure at a temperature of 20±2℃ and a relative humidity of ≥95% until the specified age, so that its 28-day compressive strength is not less than 40MPa. After the maintenance is up to standard, recheck the spatial connection between the permeable holes 112, the upper hollow channel 211, and the annular drainage groove 24. Clean the residual trace amount of overflow material in the holes and check the bonding and curing status between the outer protective structure 23, the inner protective structure 22, the inner spiral bionic core 21, and the cast-in-place lower support structure 1 to ensure that there is no loosening or falling off. Then, allow the structure to be acclimatized with natural seawater or simulated seawater for no less than 30 days to stabilize the pH value of the surface leachate before planting.

[0042] To further illustrate the feasibility of the technical solution of the present invention, two sets of embodiments applicable to different application scenarios are provided below, and all parameters strictly follow the aforementioned core structure and printing process requirements.

[0043] In the first embodiment, it is suitable for pure sandy or muddy seabed, nearshore shallow sea with gentle sea conditions, wave height ≤1.0m, and current velocity ≤0.5m / s. The overall size of the artificial reef is φ1500mm×1160mm, with the internal spiral biomimetic core 21 having a height of 900mm, the supporting disc 11 having a thickness of 200mm, and the supporting column 12 having a height of 60mm. The specific implementation process is strictly carried out in the order of cast-in-place, interface treatment, trial extrusion calibration, single-layer full-section continuous 3D printing, cleaning and inspection, seawater acclimatization, and deployment and application, as detailed below.

[0044] Step 1: Material Preparation. Prepare the cast-in-place materials according to the following mass ratio: low-alkalinity sulfoaluminate cement: slag powder: low-calcium fly ash: silica fume: medium sand: 5-10mm continuously graded crushed stone: water: polycarboxylate superplasticizer = 1:0.42:0.17:0.08:1.40:2.95:0.56:0.014, and additionally add 0.6 kg / m³ of [unspecified additive]. 3 Polypropylene fiber; based on this ratio, the total amount of cementitious material is 1.67, the actual water-cement ratio is 0.56 / 1.67≈0.335, and the sand ratio is 1.40 / (1.40+2.95)≈32.2%. A forced-action concrete mixer is used to first dry-mix the cementitious material, aggregate, and fiber for 2 to 3 minutes, then add approximately 80% of the mixing water and water-reducing agent and mix for 3 minutes. Finally, the remaining mixing water is added according to the slump, and mixing continues for 2 minutes to produce a uniform, lump-free, and segregated cast-in-place concrete. The 3D printing material is prepared according to the following mass ratio: low-alkalinity sulfoaluminate cement: slag powder: low-calcium fly ash: silica fume: calcium carbonate micro powder or washed and crushed shell powder: graded quartz sand or calcium carbonate sand: water: polycarboxylate superplasticizer: thixotropic agent: retarder = 1:0.37:0.13:0.08:0.08:1.75:0.50:0.016:0.004:0.001, with 0.10% by volume of chopped basalt fiber or PVA fiber added. Based on this ratio, the total amount of cementitious material is 1.66, the actual water-cement ratio is 0.50 / 1.66≈0.301, and the sand-cement ratio is 1.75 / 1.66≈1.05. The printing aggregate uses a two-gradation compound of 0.15 to 0.6 mm and 0.6 to 1.2 mm; the thixotropic agent is a composite system of nano-clay and cellulose ether. After being dry-mixed in a forced mixer for 2 minutes, the mixture containing water-reducing agent and setting agent is added and stirred for 4 to 5 minutes. After adding thixotropic agent and short-cut fibers, it is stirred at low speed for 1 to 2 minutes. After standing for 1 minute, a test extrusion is carried out. Once it is confirmed that the strips are continuous, the edges are clear, and the 6 layers do not collapse when stacked, it is ready for use.

[0045] The second step involves the in-situ casting of the base and the shaping of the differentiated inserts. A special in-situ casting mold with permeable holes 112 integrally machined on the base plate, forming a raised section with a height of 210mm and a diameter of 12mm, is used. A two-way steel mesh 113 is precisely laid out inside the mold, ensuring that the hole positions avoid the steel skeleton. Then, the prepared in-situ concrete is poured into the mold as a whole, forming four supporting columns with a diameter of 60mm and a height of 60mm, and a bearing disc 11 with a thickness of 200mm and a diameter of 1500mm. During the pouring and mechanical vibration compaction process, it is ensured that there are no cracks and no grout leakage. After the concrete is poured and before it initially sets, the independent short rods (12mm in diameter and 120mm in length in this embodiment) used to form the coral planting holes 111 are inserted vertically into the concrete from the upper surface of the supporting disc 11 to a depth of 80mm (i.e., 40mm protruding outside for easy removal) according to the design coordinates. The short rods are naturally fixed by the consistency of the slurry before the concrete initially sets, and their bottom ends are suspended in the air, making it strictly forbidden to touch the bottom plate of the mold, and ensuring that they do not penetrate the supporting disc 11. This state is maintained until the concrete reaches the initial setting stage or before the final setting, and then the independent short rods are pulled out vertically. After the base hardens to the demolding strength, the whole unit is lifted and demolded, allowing the integrated molding protrusion of the mold base plate to exit smoothly. The molded base is then placed in a standard curing environment with a temperature of 20±2℃ and a relative humidity of ≥95% for 3 to 7 days for pre-curing until the concrete compressive strength is ≥20MPa before the upper 3D printing is performed. After demolding and pre-curing, check and ensure that all permeable holes 112 are clear and unobstructed. The molding depth of the coral planting hole 111 is strictly controlled to be 80mm, which accounts for about 40% of the thickness of the bearing disc 11, and is within the range of 1 / 3 to 1 / 2. The bottom is closed and dense, without slurry blockage.

[0046] The third step is the reference surface treatment and hole position verification. After the maintenance meets the standards, a high-pressure air gun and a brush are used to clean the laitance and debris on the top surface of the supporting disc 11 to ensure that the surface is flat, dense, and free of any loose attachments. Based on the design coordinates of the vertical hollow channel 211 with a bottom diameter of 50% to 60% of the diameter of the supporting disc 11 and a height of 900mm, the reserved coral planting holes 111 and water permeable holes 112 are precisely verified. It is strictly ensured that the boundary of the water permeable hole 112, which is aligned and connected with the hollow channel 211, is precisely aligned with the orthographic projection area of ​​the vertical hollow channel of the internal spiral bionic core 21, and the axis alignment error is controlled within 5mm, so as to eliminate the step effect at the edge of the hole and open up the water circulation path throughout the reef.

[0047] Step 4: Interface processing and single-layer full-section continuous 3D printing. Start the 3D concrete continuous extrusion printer, adjust the equipment and set the printing parameters: nozzle line width 25mm, printing layer thickness 4.5mm, nozzle movement speed 40 to 65mm / s. Import the preset Archimedes spiral path, enclosure wall closed trajectory, empty-run crossing trajectory, and no-drill zones for holes. This step first roughens, cleans, pre-wets, and coats the upper surface of the supporting disc 11 with interface slurry. Before the interface slurry initially sets, print 1 to 2 bottom locking layers. Then, use a full-section multi-turn continuous printing method based on single-layer height to construct the upper main structure 2. In this embodiment, the inner enclosure structure 22 is 225mm high, corresponding to approximately 50 layers; the outer enclosure structure 23 is 450mm high, corresponding to approximately 100 layers; and the inner spiral bionic core 21 is 900mm high, corresponding to approximately 200 layers. When printing layers 1 to 50, the nozzle sequentially completes the cross-sectional paths of the inner spiral bionic core 21, inner enclosure structure 22, and outer enclosure structure 23 within the same Z-axis height. When printing layers 51 to 100, the path of the inner enclosure structure 22 is closed, and the paths of the inner spiral bionic core 21 and outer enclosure structure 23 are continuously completed within the same Z-axis height. When printing layers 101 to 200, only the inner spiral bionic core 21 continues to be printed to the preset height. The circumference L of a single turn of the bottom spiral of the inner spiral bionic core 21 is approximately 2400 mm. Based on this, the displacement S = L / N is calculated to be approximately 12 mm. The single displacement S is set to 12 mm to satisfy the constraint condition that S ≤ half the nozzle linewidth, i.e., 12.5 mm. During the printing process, the nozzle strictly avoids the blank areas corresponding to the coral planting holes 111 and water permeable holes 112 on the supporting disc 11. If necessary, removable temporary plugs are used to protect the orifices, and no slurry covering is allowed. Simultaneously, maintain a uniform gap of approximately 15mm between the vertical components of the internal spiral bionic core 21, forming a full-area vertical hollow channel 211 that runs through the entire internal spiral bionic core 21. A pre-reserved annular drainage groove 24 is placed between the inner enclosure structure 22 and the internal spiral bionic core 21, serving as a continuous hydrodynamic channel and remaining clear at all times. After printing to a preset height of 900mm for the internal spiral bionic core 21, stop the work and perform atomized moisturizing and standard curing on the entire upper main structure 2, ensuring that the composite reef develops a compressive strength of no less than 40MPa 28 days after casting. After curing, verify the connection between the permeable holes 112, the internal vertical hollow channel 211, and the annular drainage groove 24, clean up any remaining traces of overflow, and check the overall bonding and consolidation status between the internal spiral bionic core 21, the inner enclosure structure 22, the outer enclosure structure 23, and the cast-in-place lower support structure 1, ensuring no loosening or detachment.

[0048] It is important to emphasize that during the printing of the inner enclosure structure 22 and the outer enclosure structure 23, when the nozzle performs extrusion start-stop, Z-axis safety lifting and empty run-through, it must be strictly controlled within the preset clearance running trajectory. The net distance between the bottom surface of the nozzle and the highest point of the formed part should not be less than 20mm. Physical collision between the mechanical outline or the nozzle and the formed central internal spiral bionic core 21 is strictly prohibited. When resuming extrusion, the material accumulation at the end of the path should be controlled by advance compensation and retraction compensation to avoid the formation of slurry tail in the annular diversion groove 24.

[0049] Step 5: Cleaning, Inspection, and Application. After the curing is completed, the connection accuracy between the permeable holes 112 and the upper hollow channel 211 is checked again. Any residual trace amounts of slurry in the holes are cleaned to ensure the continuity of the water circulation path. The adhesion of the outer protective structure 23, the inner protective structure 22, the inner spiral bionic core 21, and the cast-in-place structure is checked to ensure that there is no loosening or detachment. The overall porosity of the reef is tested to ensure that it reaches approximately 30%. Subsequently, the formed reef is placed in natural seawater or simulated seawater for more than 30 days to acclimate. After the pH value of the surface leachate stabilizes at 8.2 to 8.8, the compressive strength of the reef or specimens under the same curing conditions is tested to be ≥40MPa. The compressive strength loss rate of the standard specimens with the same mix ratio after immersion in seawater for 6 months is ≤5% as a durability verification indicator. This is not a process that requires waiting 6 months before deploying a single reef. After the above conditions are met, a lifting device is used to deploy the coral to the target sea area. During deployment, it is ensured that the supporting disc 11 is stably attached to the pure sandy seabed without tilting or shifting. After deployment, the coral fragments are inserted one by one into the reserved coral planting holes 111 to fix them, thus completing the coral planting.

[0050] Another embodiment is suitable for muddy seabeds, nearshore medium-deep sea conditions with wave height ≤3.0m and current velocity ≤1.5m / s, and can withstand medium-intensity wind and wave impacts. The overall dimensions of the artificial reef are φ1800mm×1400mm, including an internal spiral biomimetic core 21 with a height of 1000mm, a supporting disc 11 with a thickness of 300mm, and a supporting column 12 with a height of 100mm. The molding process sequence in this embodiment is the same as that in the first embodiment. The main difference lies in the differentiated adjustments to the structural dimensions, material water consumption, and printing parameters: the number of supporting columns 12 is increased to 6 to 8, and their diameter is increased to 120 to 180 mm and their height is increased to 100 mm to improve the bearing area and anti-settlement capacity on the muddy seabed; the amount of crushed stone in the cast-in-place material is increased, and the mass ratio of low-alkalinity sulfoaluminate cement: slag powder: low-calcium fly ash: silica fume: medium sand: crushed stone: water: polycarboxylate superplasticizer is 1:0.42:0.17:0.08:1.30:3.10:0.56:0.014, with an additional 0.9 kg / m³ of [unspecified ingredient]. 3Polypropylene fiber; based on this ratio, the actual water-cement ratio is approximately 0.335, and the sand ratio is approximately 29.5%, in order to reduce the risk of shrinkage cracking and increase the self-weight and density of the base. The 3D printing material is prepared by mass ratio of low-alkalinity sulfoaluminate cement: slag powder: low-calcium fly ash: silica fume: calcium carbonate micro powder: graded sand: water: polycarboxylate superplasticizer: thixotropic agent: retarder = 1:0.37:0.13:0.08:0.08:1.85:0.56:0.016:0.005:0.001, with 0.15% by volume of chopped basalt fiber or PVA fiber added. Based on this ratio, the actual water-cement ratio is approximately 0.56 / 1.66≈0.337, and the sand-cement ratio is approximately 1.85 / 1.66≈1.11. By appropriately increasing the water content, the continuity of large-linewidth strip pumping is ensured, and the early buildability and resistance to plastic shrinkage are maintained by increasing the thixotropic agent and fiber content. During printing, the nozzle linewidth was adjusted to 40mm, the printing layer thickness to 5mm, and the nozzle movement speed to 45-80mm / s. The gap between the vertical components of the internal spiral bionic core 21 was adjusted to 12mm, and the diameter of the permeable holes 112 was adjusted to 10mm with a quantity of 38. The overall porosity of the artificial reef was tested and found to be approximately 30%. Based on the height of the internal spiral bionic core 21 (1000mm) and the printing layer thickness (5mm), the total number of printing layers N was determined to be approximately 200 layers. When the circumference L of the bottom spiral of the internal spiral bionic core 21 was approximately 2800mm, the displacement S = L / N was approximately 14mm, which is less than half the nozzle linewidth (20mm), ensuring the overall stability and forming accuracy of the spiral structure. The remaining interface treatment, single-layer full-section continuous printing, cleaning and inspection, seawater acclimatization, and deployment and planting processes were consistent with the first embodiment and will not be described again here.

[0051] In summary, the technical solution provided by the embodiments of the present invention, relying on the composite process of cast-in-place and 3D printing and the exclusive structural design, achieves multiple improvements in structural stability, coral adaptability and hydrodynamic control capabilities. The beneficial effects brought about include at least the following aspects, all of which are directly brought about by the core technical features of this technology, and have clear inevitability and practicality.

[0052] Firstly, it enhances the overall structural stability and durability. This invention adopts a composite mode combining cast-in-place load-bearing and 3D printing biomimetic technology. The bottom supporting column 12 and the bearing disk 11 are integrally cast-in-place and have built-in bidirectional steel mesh, which greatly enhances the reef's resistance to bending, shearing, settlement, and overturning, overcoming the shortcomings of traditional cast-in-place artificial reefs, such as their simple shape and weak wave resistance. The upper 3D-printed outer protective structure 23, inner protective structure 22, and internal spiral biomimetic core 21 are all connected to the cast-in-place base through interface slurry, bottom locking layer, rough interface, and optional shallow grooves or shear keys. The high-activity silica fume and short-cut fibers incorporated into the printing material strengthen the interlayer bonding and crack resistance, solving the problems of easy structural loss and poor resistance to ocean current shear force. The compressive strength loss rate of the standard specimen after immersion in seawater for 6 months is no more than 5%, which can adapt to the service requirements of different sea conditions for a long time.

[0053] Secondly, it optimizes the coral growth environment, enabling convenient and pollution-free planting. This invention features pre-drilled coral planting holes 111 on the supporting disc 11, allowing direct insertion and fixation of broken coral branches without the need for epoxy resin or other chemical adhesives. This solves the problems of cumbersome operation and water pollution associated with existing artificial reef coral planting methods, and is suitable for the growth and fixation needs of various branched corals. Simultaneously, the hollowed-out channels 211, permeable holes 112, and annular drainage channels 24 of the internal spiral biomimetic core 21 form a comprehensive water circulation pathway, efficiently transporting bottom nutrients and dissolved oxygen to the coral planting area. Combined with the wave-shaped contour of the outer protective structure 23, this forms an energy-dissipating shelter zone, reducing the impact of strong currents on coral branches and preventing coral breakage during typhoons, thereby significantly improving the survival rate of planted corals.

[0054] Third, precise flow field control improves water circulation efficiency. This invention guides water flow to form a stable circulation through the Archimedes spiral structure of the internal spiral biomimetic core 21, which, together with the acceleration effect of the annular diversion channel 24, optimizes the near-seabed flow field distribution and avoids the impact of water turbulence on corals. The permeable holes 112 and the hollow channels 211 are precisely connected to open up the water circulation path between the bottom and the interior of the reef, greatly improving the transport efficiency of nutrients and dissolved oxygen, and solving the problem of existing artificial reefs lacking a fully connected water circulation structure and insufficient nutrient exchange.

[0055] Fourth, it enhances the biomimetic performance and molding flexibility of the structure, reducing construction difficulty. The application of 3D printing technology breaks through the shaping limitations of traditional mold casting, and can accurately mold complex topological structures such as the internal spiral biomimetic core 21 and the wave-shaped outer protective structure 23, significantly increasing the specific surface area of ​​the reef. At the same time, the low alkalinity of the printing material ensures that the pH value of the surface leachate after seawater acclimation is stable at 8.2 to 8.8, which enhances the adhesion affinity of coral planktonic larvae and overcomes the defects of traditional cast artificial reefs, such as smooth surface, small specific surface area, and incompatibility with coral attachment. The combination of single-layer full-section continuous printing mode and cast-in-place process simplifies the construction process, eliminates the need for complex molds, and reduces construction difficulty and cost while avoiding cold seams between layers. Moreover, the size of the reef and printing parameters can be flexibly adjusted according to the bottom sediment and sea conditions of different sea areas, making it more adaptable.

[0056] Fifth, it possesses both ecological and engineering value. This invention not only solves the core technical problems of insufficient structural stability and poor coral adaptability in existing artificial reefs, but also realizes multiple ecological functions such as reef protection, coral cultivation, and fish habitat, which can effectively promote the restoration of degraded coral reef ecosystems. At the same time, the reef body is made of marine-specific low-alkalinity concrete material, which releases no harmful components and causes no secondary pollution to the marine environment, in line with the concept of green ecological restoration, and has significant engineering application value and ecological benefits.

[0057] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0058] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biomimetic artificial reef suitable for coral colonization, characterized in that, It includes a lower support structure (1) and an upper main structure (2) located above the lower support structure (1). The lower support structure (1) includes a bearing disk (11) and a support column (12) connected below the bearing disk (11), and the bearing disk (11) and the support column (12) are integrally cast concrete structures. The upper main structure (2) is a concrete structure printed layer by layer on the bearing disk (11) and fixed to the bearing disk (11). It includes an inner spiral bionic core (21) fixed to the bearing disk (11). The inner spiral bionic core (21) rises vertically from the outside to the center, and there is a gap between its adjacent vertical spiral structures. The gap forms a hollow channel (211) that runs vertically through the inner spiral bionic core (21). The upper main structure (2) also includes an inner enclosure structure (22) surrounding the outer side of the inner spiral bionic core (21) and an outer enclosure structure (23) located outside the inner enclosure structure (22). The inner enclosure structure (22) and the outer enclosure structure (23) are both erected on the bearing disk (11) to form a double-layer protective structure. An annular drainage groove (24) is formed between the inner enclosure structure (22) and the inner spiral bionic core (21). The supporting disc (11) has a coral planting hole (111) for inserting and fixing coral fragments. The bottom diameter of the outermost ring of the inner spiral bionic core (21) is 50% to 60% of that of the bearing disk (11), and the gap between adjacent vertical spiral structures is 10 to 20 mm. The bearing disc (11) is also provided with permeable holes (112) that penetrate its thickness. Some of the permeable holes (112) are aligned and connected with the hollow channel (211), and some of the permeable holes (112) are aligned and connected with the annular drainage groove (24). The diameter of the permeable holes (112) ranges from 8 to 12 mm, and the specific number can be adjusted according to the actual sea conditions. The bearing disc (11) has a built-in two-way steel mesh (113), the thickness of the bearing disc (11) is 200 to 300 mm and the diameter is 1500 to 2000 mm; the supporting column (12) is provided in multiple pieces and is evenly spaced along the edge of the bearing disc (11). The coral planting hole (111) is a blind hole that does not penetrate the supporting disc (11), and the hole diameter ranges from 8 to 12 mm, and the hole depth is 1 / 3 to 1 / 2 of the thickness of the supporting disc (11).

2. The biomimetic artificial reef suitable for coral colonization according to claim 1, characterized in that, The projection of the outer enclosure structure (23) onto the bearing disk (11) is wavy, and the height of the inner enclosure structure (22) is lower than the height of the outer enclosure structure (23).

3. A biomimetic artificial reef suitable for coral colonization according to claim 1, characterized in that, The coral planting holes (111) are arranged in multiple evenly spaced circumferentially around the supporting disc (11), and are all located between the inner enclosure structure (22) and the outer enclosure structure (23).

4. A composite molding method for a biomimetic artificial reef suitable for coral colonization as described in any one of claims 1 to 3, characterized in that, include: S1. The lower support structure (1) is integrally formed by concrete casting. The lower support structure (1) includes the bearing disc (11) and the support column (12) located below the bearing disc (11), and the coral planting hole (111) is formed on the bearing disc (11). S2. Roughen, clean and pre-wet the upper surface of the formed bearing disk (11), and coat it with a low-alkali interface slurry of the same system as the printing material while keeping it in a surface dry and wet state; before the interface slurry initially sets, use low-alkali 3D printing cement-based material and perform full-section multi-turn continuous printing based on single-layer height to form the upper main structure (2) layer by layer, and fix the upper main structure (2) to the bearing disk (11); the upper main structure (2) includes an internal spiral bionic core (21), the internal spiral bionic core (21) extends inward layer by layer along the Archimedean spiral curve, and the starting point of each spiral path moves forward by a displacement S relative to the previous layer along the path direction; the displacement S satisfies S=L / N, where L is the circumference of a single turn of the bottom spiral, N is the total number of printed layers of the internal spiral bionic core (21), and S is not greater than half of the print nozzle line width W.

5. The composite molding method according to claim 4, characterized in that, The supporting disc (11) is also formed with permeable holes (112) that penetrate its thickness. In S1, the permeable holes (112) and the coral planting holes (111) are formed in different ways: the permeable holes (112) are formed directly by forming protrusions set on the bottom plate of the casting mold, and the height of the forming protrusions is equal to the casting thickness of the supporting disc (11); the coral planting holes (111) are formed by independent short rods. That is, after the supporting disc (11) is cast and before the concrete initially sets, the independent short rods are vertically inserted into the concrete from the upper surface of the supporting disc (11), and after the concrete initially sets but before it sets, the independent short rods are pulled out, thereby forming blind holes that do not penetrate the supporting disc (11).

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