3D printing concrete composite anti-collision structure for ship lock wall and preparation method thereof

Abstract

This invention belongs to the field of lock wall protection technology, and discloses a 3D-printed concrete composite anti-collision structure for lock walls. It includes a composite material layer disposed on the surface of the lock wall via connecting components. The composite material layer comprises, from the outside to the inside, a UHPC impact-resistant layer, a gradient transition layer, and a foamed concrete energy-absorbing layer. The UHPC impact-resistant layer uses a multi-scale composite reinforcement, and the matrix is ​​ultra-high performance concrete incorporating modified hollow polypropylene microspheres. The reinforcement includes end-hooked steel fibers and modified multi-walled carbon nanotubes. The gradient transition layer uses elastic microspheres combined with steel fibers, combined with a negative Poisson's ratio honeycomb structure. The foamed concrete energy-absorbing layer uses rubber particles, microencapsulated phase change materials, and water-based polyurethane emulsion. The invention also discloses a method for preparing the above-mentioned 3D-printed concrete composite anti-collision structure for lock walls. This invention achieves a unified approach to high impact resistance, intelligent sensing, and damping protection.

Description

Technical Field

[0001] This invention belongs to the field of lock wall protection technology, and in particular relates to a 3D printed concrete composite anti-collision structure for lock walls and its preparation method. Background Technology

[0002] As a key hydraulic structure in shipping hubs, the lock wall structure operates under complex mechanical and environmental conditions for extended periods. During actual navigation, lateral collisions between ships and the lock walls are frequent due to factors such as rapid currents, diverse ship types, and human error. These collisions are characterized by high instantaneous energy, concentrated impact points, and strong destructive force, easily leading to spalling of the concrete surface, crack development, and even corrosion of the internal steel reinforcement, seriously threatening the operational safety of the lock and shortening its service life. Therefore, developing efficient and reliable lock wall anti-collision structures has always been a key research topic in the field of hydraulic engineering.

[0003] Currently, the engineering community focuses on two main aspects of lock wall protection: 1. Collision protection for the gate system: Conventional techniques involve adding hydraulic buffers and flexible fenders to the lock walls to reduce direct damage from ship collisions. Chinese patent CN220789634U discloses a standardized anti-collision fender for a miter gate in a lock, employing a double-layer structure of "rigid fender + flexible fender" to achieve graded absorption of impact energy, extend impact time, and improve navigation safety. Chinese patent CN118774101A discloses an anti-collision device for high-head lock gates. The first method involves using a steel wire rope that is deflected through a buoy and connected to a pulley assembly to convert impact energy into the kinetic energy of a counterweight and hydraulic damping, suitable for the dynamic collision avoidance requirements of high-head locks. Chinese patent CN219450684U discloses a lock anti-collision device that absorbs impact energy through a spring-piston system, combined with an arc-shaped guide plate and an inclined guide section to deflect the ship's course, preventing direct impact to the lock wall. The second method involves strengthening the lock wall itself. Existing technologies for lock wall anti-collision often employ a "cast-in-place high-strength concrete + surface protection" approach. On one hand, this involves increasing the concrete grade to rely on the material's inherent rigidity and strength to withstand impacts; on the other hand, it involves attaching rubber fenders or adding steel structure anti-collision islands to the outside of the lock wall.

[0004] However, with the trend towards larger ships, the limitations of traditional technologies are becoming increasingly apparent, mainly in the following four aspects: 1. Insufficient impact resistance: Ordinary high-strength concrete or conventional ultra-high-performance concrete mainly exhibits the characteristics of brittle materials, with its stress-strain curve dropping rapidly after reaching its peak. When subjected to ship impact, it mainly relies on the material's stiffness and strength to resist external forces, lacking an effective viscoelastic or plastic deformation mechanism to dissipate the enormous impact kinetic energy. This results in low energy absorption efficiency, making it prone to brittle fracture or localized pulverization, and failing to meet the protection requirements under high-energy impacts. 2. Heavy structure and difficult installation and maintenance: Traditional pure concrete crash barriers or heavy steel structure crash barriers have extremely large self-weights, significantly increasing the load on the gate wall foundation and placing higher demands on the foundation's bearing capacity. Moreover, construction often requires large machinery and equipment, resulting in long installation cycles. More importantly, once a part is damaged in a collision, due to the irreversible integrity of the structure, repairs usually require emptying the lock chamber and building a cofferdam, which is not only costly but also severely disrupts navigation, resulting in huge economic losses. 3. Weak Interface Bonding: Existing composite collision protection structures typically employ layered prefabrication and assembly or layered casting processes. For example, rigid high-strength panels are connected to flexible foam energy-absorbing layers using adhesives or ordinary mortar. Due to the significant differences in the elastic modulus of the materials between different layers, stress concentration easily occurs at the interface under strong impact loads, leading to interlayer delamination and voiding, causing premature failure of the composite structure and its inability to work collaboratively. 4. Lack of Active Monitoring and Adaptive Design: Most existing collision protection technologies are "passive defenses," unable to detect the health status of the barrier in real time during navigation, nor can they adaptively adjust the energy-dissipating stiffness according to the magnitude of the impact energy. When the impact force is small, rigid protection may damage the ship; when the impact force is large, insufficient energy dissipation may damage the main body of the barrier. Summary of the Invention

[0005] To address the aforementioned issues, the present invention aims to provide a 3D-printed concrete composite anti-collision structure for lock walls that integrates high impact resistance, intelligent monitoring, and self-repair capabilities, while also disclosing a method for preparing the aforementioned 3D-printed concrete composite anti-collision structure for lock walls.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A 3D-printed concrete composite anti-collision structure for a lock wall includes a composite material layer disposed on the surface of the lock wall via connecting components. The composite material layer comprises, from the outside to the inside, a UHPC impact-resistant layer, a gradient transition layer, and a foamed concrete energy-absorbing layer. The UHPC impact-resistant layer, by weight, comprises: 350-400 parts silicate cement, 60-90 parts silica fume, 70-120 parts quartz powder, 25-45 parts modified hollow polypropylene microspheres, 80-150 parts hook-shaped steel fibers, 1-5 parts modified multi-walled carbon nanotubes, 8-15 parts polycarboxylate superplasticizer, and 90-120 parts water. The gradient transition layer, by weight, comprises: 300-400 parts silicate cement, 50-80 parts silica fume, 40-60 parts fly ash, 20-60 parts elastic microspheres, 20-80 parts steel fiber, 10-30 parts microencapsulated repair agent, and 1-3 parts silane coupling agent. The foamed concrete energy-absorbing layer, by weight, comprises: 150-300 parts of rapid-hardening sulfoaluminate cement, 50-120 parts of fly ash, 50-80 parts of rubber particles, 20-40 parts of microencapsulated phase change material, 2-5 parts of protein-based foaming agent, 5-20 parts of waterborne polyurethane emulsion, 5-15 parts of mixed fibers, and 75-150 parts of water.

[0007] Furthermore, in the aforementioned UHPC impact-resistant layer, the modified hollow polypropylene microspheres are prepared as follows: 50–100 μm hollow polypropylene microspheres are mixed with a 2–6% (w / w) silane coupling agent ethanol solution at a material-to-liquid ratio of 1 mg: 5–8 ml. The mixture is then ultrasonically dispersed in a constant temperature water bath at 40–60 °C for 30–40 min at an ultrasonic power of 300–500 W to obtain a dispersion. After filtration, the dispersion is dried in a vacuum drying oven at 60–80 °C for 4–6 h to obtain modified hollow polypropylene microspheres coated with a silane coupling agent.

[0008] Furthermore, in the above-mentioned UHPC impact-resistant layer, the modified multi-walled carbon nanotubes are prepared by dispersing the acid-treated multi-walled carbon nanotubes in an aqueous solution containing polycarboxylic acid water-reducing agent, adding a graphene oxide dispersion with a solid content of 2-5%, ultrasonically treating at a power of 500-800W for 30-60 minutes, and then spray drying to obtain carbon nanotube-graphene composite reinforced powder.

[0009] Furthermore, in the above-mentioned method for preparing modified multi-walled carbon nanotubes, the mass ratio of multi-walled carbon nanotubes, polycarboxylate superplasticizer, graphene oxide dispersion, and water is 1.5–2.5: 4–6: 0.8–1.2: 100.

[0010] Furthermore, the above-mentioned acidification treatment method for multi-walled carbon nanotubes includes the following steps: S1.1. Mix 95-98% concentrated sulfuric acid and 65-68% concentrated nitric acid at a volume ratio of 2-4:1 to obtain a mixed acid solution, and cool it in an ice-water bath; S1.2. Slowly add multi-walled carbon nanotubes to the cooled mixed acid solution from step S1.1. The ratio of multi-walled carbon nanotubes to the mixed acid solution is 1-3 g : 200 mL. After stirring evenly, a mixture is obtained. The mixture is then ultrasonically treated at a power of 300-500 W for 2-4 hours under ice-water bath cooling and reflux conditions, with the temperature monitored and maintained at 20-40°C throughout the process. After the reaction is complete, the mixture is slowly poured into ice water for dilution. Then, solid-liquid separation is performed by centrifugation or vacuum filtration to obtain a black solid. S1.3. The black solid obtained in step S1.2 is repeatedly washed with deionized water until the pH of the supernatant is neutral. The product that has been washed to neutrality is placed in a vacuum oven and dried at 60-80°C for 12-24 hours to obtain oxygen-functionalized multi-walled carbon nanotubes.

[0011] Furthermore, in the aforementioned gradient transition layer, the microencapsulated repair agent comprises epoxy resin microcapsules with a particle size of 100–200 μm and dicyandiamide latent curing agent with a particle size of 50–80 μm, wherein the mass ratio of epoxy resin microcapsules to dicyandiamide latent curing agent is 5–7:1.

[0012] Furthermore, in the aforementioned microencapsulated repair agents, the epoxy resin microcapsules are prepared by in-situ polymerization with urea-formaldehyde resin as the wall material and epoxy resin as the core material.

[0013] Furthermore, the microencapsulated phase change material of the aforementioned foamed concrete energy-absorbing layer is prepared by in-situ polymerization using paraffin as the core material and melamine resin as the wall material; the particle size of the microencapsulated phase change material is 20-40 μm, and the phase change temperature range is 45-55℃.

[0014] Furthermore, the aforementioned gradient transition layer adopts a three-segment gradient structure consisting of a surface layer, an intermediate layer, and a bottom layer. The surface layer is close to the UHPC impact-resistant layer, and the bottom layer is close to the foamed concrete energy-absorbing layer. From the surface layer to the bottom layer, the volume content of steel fibers decreases sequentially, while the volume content of elastic microspheres increases sequentially.

[0015] Furthermore, in the aforementioned gradient transition layer, the volume content of steel fibers in the surface layer is 2.5–3.5%, and the volume content of elastic microspheres is 5–7%; the volume content of steel fibers in the intermediate layer is 1.2–2.0%, and the volume content of elastic microspheres is 10–14%; and the volume content of steel fibers in the bottom layer is 0.5–1.0%, and the volume content of elastic microspheres is 15–18%.

[0016] Furthermore, the aforementioned foamed concrete energy-absorbing layer is composed of steel fibers and polypropylene fibers in a volume ratio of 1:1 to 2.

[0017] Furthermore, the aforementioned UHPC impact-resistant layer has a thickness of 60–100 mm and a density of 950–1050 kg / m³. 3 .

[0018] Furthermore, the aforementioned gradient transition layer has a thickness of 20–30 mm and a density of 800–900 kg / m³. 3 .

[0019] Furthermore, the aforementioned foamed concrete energy-absorbing layer has a thickness of 100–200 mm and a density of 350–500 kg / m³. 3 .

[0020] Furthermore, an intelligent sensing network composed of fiber optic grating sensors and piezoelectric ceramic arrays is embedded within the aforementioned UHPC impact-resistant layer.

[0021] Furthermore, the aforementioned connecting components include a permanent magnet connecting seat pre-embedded at the bottom of the composite material layer and a damping groove pre-embedded in the lock wall. A permanent magnet is fixed on the permanent magnet connecting seat, and the permanent magnet connecting seat is slidably embedded in the damping groove.

[0022] The above-mentioned method for fabricating a 3D-printed concrete composite anti-collision structure for lock walls includes the following steps: S1. Preparation of UHPC impact-resistant layer Silicate cement, silica fume, quartz powder, and modified hollow polypropylene microspheres are dry-mixed evenly. Then, modified multi-walled carbon nanotubes, hooked steel fibers, polycarboxylate superplasticizer, and water are added and stirred to obtain UHPC slurry. The UHPC slurry is fed into a 3D printer, and the first print head prints at a speed of 80-120 mm / s. During the printing process, a magnetic field of 0.5-1T is applied, and fiber optic grating sensors and piezoelectric ceramic arrays are embedded simultaneously. S2. Preparation of gradient transition layer After the UHPC impact-resistant layer in step S1 is printed to the set height, the second print head and the batching system are started to mix silicate cement, silica fume, fly ash, elastic microspheres, steel fibers and silane coupling agent to form a gradient transition slurry for printing. The flow rate of steel fibers and elastic microspheres is dynamically adjusted according to a three-stage gradient ratio to control the printing path to form a negative Poisson's ratio honeycomb structure. Microencapsulated repair agent is added online before the slurry is extruded and printed to the designed thickness. S3. Preparation of foamed concrete energy-absorbing layer After the gradient transition layer is printed in step S2, the third print head is started to mix and stir the rapid-hardening sulfoaluminate cement, fly ash, rubber particles, microencapsulated phase change material, protein foaming agent and water to make foam concrete slurry for printing; at the same time, during the printing process, waterborne polyurethane emulsion is sprayed into the inner wall of the foam pores through the auxiliary nozzle, and mixed fibers are added in the surface 30-50mm range through the spreading device. S4. Maintenance and Post-treatment Each component printed in steps S1, S2, and S3 is steam-cured, then standard-cured for 28 days. Finally, each component is floated to the installation location and installed on the gate wall surface using connecting components.

[0023] Furthermore, in step S4 above, the steam curing temperature is 55-65℃, the humidity is ≥95%, and the duration is 20-28 hours.

[0024] Due to the adoption of the technical solution described above, the present invention has the following advantages: This invention relates to a 3D-printed concrete composite anti-collision structure for ship lock walls. Its UHPC impact-resistant layer employs a multi-scale composite reinforcement. The matrix is ​​ultra-high performance concrete incorporating modified hollow polypropylene microspheres. The reinforcement includes hook-shaped steel fibers and modified multi-walled carbon nanotubes. The multi-walled carbon nanotubes and hook-shaped steel fibers, through a reasonable ratio, form a "nano-micro" multi-scale reinforcement network, significantly improving the material's fracture toughness and initial impact strength. The carbon nanotubes fill the nanoscale pores of the cement matrix and bridge microcracks, while the steel fibers provide macroscopic crack resistance. The multi-walled carbon nanotubes... The tubes are ultrasonically dispersed and premixed with polycarboxylate superplasticizer, strengthening the interfacial transition zone between the cement matrix and fibers through chemical bonding. Before use, multi-walled carbon nanotubes undergo acidification treatment, introducing oxygen-containing functional groups such as carboxyl and hydroxyl groups onto their surface. This not only improves the dispersibility of multi-walled carbon nanotubes in aqueous slurries and prevents agglomeration, but also allows them to chemically react or physically entangle with cement hydration products, enhancing the interfacial adhesion between the multi-walled carbon nanotubes and the cement matrix. This more effectively transfers stress and prevents the propagation of microcracks. The embedding of intelligent sensors enables full... Lifecycle health monitoring; the rational ratio of elastic microspheres and steel fibers in the gradient transition layer, combined with a negative Poisson's ratio honeycomb structure, enables the composite material layer to generate an "inward contraction" deformation mechanism when impacted, actively compacting the material to dissipate energy, significantly improving peak stress attenuation efficiency, and smoothly transferring stress; microencapsulated repair agents rupture and release the repair agent when microcracks occur, achieving self-repair of the structure and extending its service life; in the foamed concrete energy-absorbing layer, rubber particles utilize viscoelasticity to buffer impacts, and microencapsulated phase change materials utilize the latent heat of phase change to absorb instantaneous heat, preventing performance degradation of the concrete matrix due to temperature rise and improving the thermal stability of the structure under extreme conditions; waterborne polyurethane emulsion further enhances the damping energy dissipation capacity of the pore walls; the connecting components utilize the nonlinear mechanism of magnetic attraction and particle damping to ensure stability under normal conditions and efficient energy dissipation under large displacements, ensuring stability during daily navigation and effectively buffering accidental impacts, significantly reducing impact damage to the gate wall; the connecting components achieve precise control, efficient buffering, and intelligent response through the synergy of magnetic drive and energy absorption.

[0025] This invention relates to a 3D-printed concrete composite anti-collision structure for ship lock walls, which has high impact resistance and high energy absorption efficiency, and can achieve strong bonding between interlayer interfaces, lightweight self-buoyancy characteristics, and integrate intelligent sensing and self-healing functions; it not only significantly reduces its own weight, but also achieves a unity of high impact resistance, intelligent sensing and damping protection.

[0026] This invention discloses a method for preparing a 3D-printed concrete composite anti-collision structure for ship lock walls. It utilizes 3D printing technology to achieve integrated molding of the composite material layers, with smooth control of the interlayer components in the gradient transition layer, significantly enhancing interfacial bonding strength and effectively solving the problem of weak interfaces in traditional layered casting. Magnetic field-assisted printing enables the directional alignment of steel fibers, maximizing fiber reinforcement efficiency. Multi-nozzle collaborative operation achieves precise manufacturing of complex components and topologies. A rationally designed curing process ensures the activity of the cementitious material and the integrity of the microcapsule wall material. Modular floating installation significantly improves construction efficiency. Attached Figure Description

[0027] Figure 1 This is a cross-sectional schematic diagram of the 3D-printed foamed concrete composite anti-collision structure for the lock wall of the present invention. Figure 2 yes Figure 1 A schematic diagram of the negative Poisson's ratio biomimetic honeycomb structure and three-segment gradient distribution in the gradient transition layer; Figure 3 yes Figure 1 A structural cross-sectional view of the connecting components in the diagram; Figure 4 It is an intelligent sensing network in Figure 1 Schematic diagram of the layout within the UHPC impact-resistant layer; In the diagram: 1 – UHPC impact-resistant layer; 2 – gradient transition layer; 3 – foamed concrete energy-absorbing layer; 4 – connecting component; 5 – gate wall; 6 – composite material layer; 7 – fiber optic grating sensor; 8 – piezoelectric ceramic sensor; 21 – surface layer; 22 – intermediate layer; 23 – bottom layer; 41 – permanent magnet connector; 42 – steel shot damping particles; 43 – damping groove; 431 – neoprene rubber pad layer. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] like Figures 1-4 As shown, a 3D-printed concrete composite anti-collision structure for a lock wall includes a composite material layer 6 disposed on the surface of the lock wall 5 via a connecting component 4. The composite material layer comprises, from the outside to the inside, a UHPC impact-resistant layer 1, a gradient transition layer 2, and a foamed concrete energy-absorbing layer 3. The foamed concrete energy-absorbing layer 3 is attached to the surface of the lock wall 5. The UHPC impact-resistant layer, by weight, comprises: 350-400 parts silicate cement, 60-90 parts silica fume, 70-120 parts quartz powder, 25-45 parts modified hollow polypropylene microspheres, 80-150 parts hook-shaped steel fibers, 1-5 parts modified multi-walled carbon nanotubes, 8-15 parts polycarboxylate superplasticizer, and 90-120 parts water. The gradient transition layer, by weight, comprises: 300-400 parts silicate cement, 50-80 parts silica fume, 40-60 parts fly ash, 20-60 parts elastic microspheres, 20-80 parts steel fiber, 10-30 parts microencapsulated repair agent, and 1-3 parts silane coupling agent. The average particle size of the elastic microspheres is 100-300 μm. The gradient transition layer adopts a three-segment gradient structure consisting of a surface layer 21, an intermediate layer 22, and a bottom layer 23. The surface layer is close to the UHPC impact-resistant layer 1, and the bottom layer is close to the foamed concrete energy-absorbing layer 3. From the surface layer to the bottom layer, the volume content of steel fiber decreases sequentially, while the volume content of elastic microspheres increases sequentially. The foamed concrete energy-absorbing layer comprises, by weight: 150-300 parts of rapid-hardening sulfoaluminate cement, 50-120 parts of fly ash, 50-80 parts of rubber particles, 20-40 parts of microencapsulated phase change material, 2-5 parts of protein-based foaming agent, 5-20 parts of waterborne polyurethane emulsion, 5-15 parts of mixed fibers, and 75-150 parts of water, wherein the average particle size of the rubber particles is 1-3 mm. In the aforementioned UHPC impact-resistant layer, the modified hollow polypropylene microspheres are prepared as follows: Polypropylene hollow microspheres with a particle size of 50–100 μm are mixed with a 2–6% (w / w) silane coupling agent ethanol solution at a material-to-liquid ratio of 1 mg: 5–8 ml. The mixture is then ultrasonically dispersed in a constant-temperature water bath at 40–60 °C for 30–40 min at an ultrasonic power of 300–500 W to obtain a dispersion. After filtration, the dispersion is dried in a vacuum drying oven at 60–80 °C for 4–6 h to obtain modified polypropylene hollow microspheres coated with a silane coupling agent. The aforementioned modified hollow polypropylene microspheres exhibit good dispersibility in the cement matrix, and the active functional groups on their surface can chemically bond with the CSH gel generated during cement hydration, significantly improving the interfacial bonding strength.

[0030] The modified multi-walled carbon nanotubes in the aforementioned UHPC impact-resistant layer are prepared as follows: Step 1: Acidification treatment of multi-walled carbon nanotubes, the steps are as follows: S1.1. Mix 95-98% concentrated sulfuric acid and 65-68% concentrated nitric acid at a volume ratio of 2-4:1 to obtain a mixed acid solution, and cool it in an ice-water bath; S1.2. Slowly add multi-walled carbon nanotubes to the cooled mixed acid solution from step S1.1. The ratio of multi-walled carbon nanotubes to the mixed acid solution is 1-3 g : 200 mL. After stirring evenly, a mixture is obtained. Place the mixture in a probe-type ultrasonic instrument and sonicate it at a power of 300-500 W for 2-4 hours under ice-water bath cooling and reflux conditions, monitoring and maintaining the temperature at 20-40°C throughout the process. After the reaction is complete, slowly pour the mixture into ice water to dilute it. Then, perform solid-liquid separation by centrifugation or vacuum filtration to obtain a black solid. S1.3. The black solid obtained in step S1.2 is repeatedly washed with deionized water until the pH of the supernatant is neutral. The product that has been washed to neutrality is placed in a vacuum oven and dried at 60-80°C for 12-24 hours to obtain oxygen-functionalized multi-walled carbon nanotubes. Step 2: Disperse the oxygen-functionalized multi-walled carbon nanotubes obtained in Step 1 in an aqueous solution containing polycarboxylate superplasticizer, add a graphene oxide dispersion with a solid content of 2-5%, ultrasonically treat at 500-800W for 30-60 minutes, and then spray dry to obtain carbon nanotube-graphene composite reinforced powder; wherein, the mass ratio of multi-walled carbon nanotubes, polycarboxylate superplasticizer, graphene oxide dispersion, and water is 1.5-2.5:4-6:0.8-1.2:100; preferably, the mass ratio of the total amount of multi-walled carbon nanotubes and graphene oxide dispersion to the mass ratio of polycarboxylate superplasticizer is 1:2.0-2.5 to ensure a stable and uniform dispersion system.

[0031] By utilizing the huge specific surface area and oxygen-containing functional groups of graphene to form π-π stacking and hydrogen bonding with carbon nanotubes, carbon nanotubes are exfoliated and loaded onto graphene sheets through ultrasonic treatment. The composite reinforcing powder formed by spray drying has excellent dispersibility in concrete. The two-dimensional sheet structure of graphene and the one-dimensional fiber structure of carbon nanotubes form a "point-line-surface" multi-dimensional network skeleton in the cement matrix, which is significantly better than single component or traditional dispersion methods, greatly improving the density and impact resistance of the UHPC impact-resistant layer.

[0032] The aforementioned gradient transition layer has a steel fiber volume content of 2.5–3.5% and an elastic microsphere volume content of 5–7% in the surface layer; a steel fiber volume content of 1.2–2.0% and an elastic microsphere volume content of 10–14% in the intermediate layer; and a steel fiber volume content of 0.5–1.0% and an elastic microsphere volume content of 15–18% in the bottom layer.

[0033] In the aforementioned gradient transition layer, the microencapsulated repair agent comprises epoxy resin microcapsules with a particle size of 100–200 μm and dicyandiamide-based latent curing agents with a particle size of 50–80 μm, wherein the mass ratio of epoxy resin microcapsules to dicyandiamide-based latent curing agents is 5–7:1; the epoxy resin microcapsules are prepared by in-situ polymerization with urea-formaldehyde resin as the wall material and epoxy resin as the core material.

[0034] The aforementioned foamed concrete energy-absorbing layer uses microencapsulated phase change material with paraffin as the core material and melamine resin as the wall material, prepared by in-situ polymerization. The particle size of the microencapsulated phase change material is 20–40 μm, and the phase change temperature range is 45–55 °C.

[0035] The aforementioned foamed concrete energy-absorbing layer comprises a hybrid fiber system consisting of steel fibers and polypropylene fibers in a volume ratio of 1:1 to 2. Steel fibers possess a high elastic modulus, primarily providing tensile strength and toughness; polypropylene fibers exhibit low modulus, high ductility, and chemical resistance. When used in combination, the steel fibers primarily bear the load during the initial impact phase of the foamed concrete; during crack propagation, the polypropylene fibers bridge micro-cracks and prevent their convergence into larger cracks. This orthogonal hybrid reinforcement significantly enhances the impact toughness and crack resistance of the foamed concrete energy-absorbing layer, effectively preventing slab fragmentation.

[0036] The aforementioned UHPC impact-resistant layer has a thickness of 60–100 mm and a density of 950–1050 kg / m³. 3 .

[0037] The aforementioned gradient transition layer has a thickness of 20–30 mm and a density of 800–900 kg / m³. 3 .

[0038] The aforementioned foamed concrete energy-absorbing layer has a thickness of 100–200 mm and a density of 350–500 kg / m³. 3 .

[0039] An intelligent sensing network consisting of a fiber optic grating sensor 7 and a piezoelectric ceramic array 8 is embedded within the aforementioned UHPC impact-resistant layer 1.

[0040] like Figure 4As shown, the connecting component 4 includes a permanent magnet connecting seat 41 embedded in the bottom of the composite material layer and a damping groove 43 embedded in the lock wall. A permanent magnet is fixed on the permanent magnet connecting seat, and the permanent magnet connecting seat is slidably embedded in the damping groove. The internal cavity of the damping groove 43 is used to accommodate steel shot damping particles 42, and a layer of neoprene rubber pad 431 is laid on the inner wall of the groove. The diameter of the steel shot damping particles is 2-5 mm, and the filling rate is 80-90% of the groove volume. The steel shot damping particles form a non-dense packing state in the groove. When the permanent magnet connecting seat is displaced, the steel shot undergoes intense friction, compression, and rolling, converting mechanical energy into heat energy. By controlling the diameter and filling rate of the steel shot, the damping coefficient can be adjusted to ensure high stiffness under small displacement and high damping under large displacement, realizing variable stiffness adaptive energy dissipation. When the composite material layer vibrates or displaces, the permanent magnet connecting seat moves relative to the damping groove. The neoprene rubber pad first absorbs part of the energy through viscoelastic deformation, while providing sealing and shock absorption functions. Subsequently, the steel shot damping particles collide and rub within the cavity to further dissipate the impact energy, thus achieving mechanical damping.

[0041] The aforementioned connection components achieve precise control, efficient buffering, and intelligent response through the synergy of magnetic drive and energy absorption.

[0042] The above-mentioned method for fabricating a 3D-printed concrete composite anti-collision structure for lock walls includes the following steps: S1. Preparation of UHPC impact-resistant layer Silicate cement, silica fume, quartz powder, and modified hollow polypropylene microspheres are dry-mixed evenly. Then, modified multi-walled carbon nanotubes, hooked steel fibers, polycarboxylate superplasticizer, and water are added and stirred to obtain UHPC slurry. The UHPC slurry is fed into a 3D printer, and the first print head prints at a speed of 80-120 mm / s. During the printing process, a magnetic field of 0.5-1T is applied, and fiber optic grating sensors and piezoelectric ceramic arrays are embedded simultaneously. S2. Preparation of gradient transition layer After the UHPC impact-resistant layer in step S1 is printed to the set height, the second print head and the batching system are started to mix silicate cement, silica fume, fly ash, elastic microspheres, steel fibers and silane coupling agent to form a gradient transition slurry for printing. The flow rate of steel fibers and elastic microspheres is dynamically adjusted according to a three-stage gradient ratio to control the printing path to form a negative Poisson's ratio honeycomb structure. Microencapsulated repair agent is added online before the slurry is extruded and printed to the designed thickness. S3. Preparation of foamed concrete energy-absorbing layer After the gradient transition layer is printed in step S2, the third print head is started to mix and stir the rapid-hardening sulfoaluminate cement, fly ash, rubber particles, microencapsulated phase change material, protein foaming agent and water to make foam concrete slurry for printing; at the same time, during the printing process, waterborne polyurethane emulsion is sprayed into the inner wall of the foam pores through the auxiliary nozzle, and mixed fibers are added in the surface 30-50mm range through the spreading device. S4. Maintenance and Post-treatment Each component printed in steps S1, S2, and S3 is steam-cured, then standard-cured for 28 days. Finally, each component is floated to the installation location and installed on the gate wall surface using connecting components.

[0043] In step S4 above, the steam curing temperature is 55-65℃, the humidity is ≥95%, and the duration is 20-28 hours. Example

[0044] A method for fabricating a 3D-printed concrete composite anti-collision structure for a ship lock wall, comprising the following steps: S1. Preparation of UHPC impact-resistant layer (1) Mix 95% concentrated sulfuric acid and 65% concentrated nitric acid at a volume ratio of 2:1 to obtain a mixed acid solution, and cool it in an ice-water bath for later use; weigh and measure the multi-walled carbon nanotubes and the mixed acid solution at a material-liquid ratio of 1g:200mL; slowly add the multi-walled carbon nanotubes to the cooled mixed acid solution, stir evenly to obtain a mixture; place the mixture in a probe-type ultrasonic instrument, and sonicate it at a power of 300W for 4 hours under the conditions of ice-water bath cooling and reflux condensation, and monitor and maintain the temperature at 20°C throughout the process; after the reaction is completed, slowly pour the mixture into ice water to dilute it; then separate the solid and liquid by centrifugation or vacuum filtration to obtain a black solid; repeatedly wash the black solid with deionized water until the pH of the supernatant is neutral; put the product washed to neutral into a vacuum oven and dry it at 60°C for 24 hours to obtain multi-walled carbon nanotubes with oxygen-containing functionalized surfaces; Two parts of oxygen-functionalized multi-walled carbon nanotubes were weighed and added to a mixture containing five parts of polycarboxylate superplasticizer and 100 parts of water. Then, one part of graphene oxide dispersion with a solid content of 2% was added. The mixture was ultrasonically treated at 600W for 45 minutes and then spray-dried to obtain carbon nanotube-graphene composite reinforced powder. (2) Polypropylene hollow microspheres with a particle size of 50 μm were mixed with 2% silane coupling agent ethanol solution at a material-liquid ratio of 1 mg: 5 ml and ultrasonically dispersed in a constant temperature water bath at 40℃ for 40 min with an ultrasonic power of 300 W to obtain a dispersion. After filtration, the dispersion was dried in a vacuum drying oven at 60℃ for 6 h to obtain modified polypropylene hollow microspheres with silane coupling agent on the surface. (3) Weigh 400 parts of silicate cement, 90 parts of silica fume, 120 parts of quartz powder, and 45 parts of modified hollow polypropylene microspheres and dry mix them evenly; then add 1 part of carbon nanotube-graphene composite reinforcing powder, 110 parts of water and 15 parts of polycarboxylate superplasticizer, and stir for 3 minutes; finally add 100 parts of end-hook steel fiber, stir evenly, and prepare UHPC slurry. Integrated 3D printing: Printing is performed using a large concrete 3D printer under ambient temperature of 20℃ and humidity of 60%; the printing speed is controlled at 100mm / s; during the printing process, a parallel magnetic field of 0.8T is applied to tangentially align the steel fibers along the printing path; when the printing reaches a height of 40mm, a smart sensing network is formed by pre-embedded fiber optic grating sensors and piezoelectric ceramic sensors in a robotic arm, and printing continues until the thickness of the UHPC impact-resistant layer reaches 100mm; S2. Preparation of gradient transition layer A gradient transition slurry was prepared by mixing 300 parts silicate cement, 50 parts silica fume, 40 parts fly ash, elastic microspheres, steel fibers, and 1 part silane coupling agent. The gradient batching mode of the multi-nozzle printing system was activated. Printing parameters were as follows: the top layer used a high-fiber formulation with 3.5% steel fiber and 7% elastic microspheres; the middle layer used a transition formulation with 2.0% steel fiber and 14% elastic microspheres; and the bottom layer used a high-elasticity formulation with 1.0% steel fiber and 18% elastic microspheres. Simultaneously, 20 parts by weight of microencapsulated repair agent (a mixture of epoxy resin microcapsules and curing agent particles) were injected via a side-feeding system. The printing path was controlled to obtain a concave hexagonal negative Poisson's ratio honeycomb structure with a printing thickness of 25 mm. S3. Preparation of foamed concrete energy-absorbing layer Weigh out 300 parts of rapid-hardening sulfoaluminate cement, 120 parts of fly ash, 60 parts of rubber granules, 3 parts of protein-based foaming agent, and 150 parts of water. Mix and foam at high speed. Then add 30 parts of microencapsulated phase change material and stir at low speed until homogeneous. Start the third printhead for printing, reduce the printing speed to 80 mm / s, and increase the ambient humidity to 85% RH. During the printing process, spray 20 parts of water-based polyurethane emulsion onto the inner wall of the foam pores through the auxiliary nozzle. When the printing reaches the surface 30 mm, add 8 parts of mixed fiber evenly through the spreading device. The printing thickness of the foamed concrete energy-absorbing layer is 175 mm. S4. Maintenance and Post-treatment Each component printed in steps S1, S2, and S3 is steam-cured for 24 hours at a temperature of 60°C and a humidity of ≥95%, and then naturally cured for 28 days. Example

[0045] A method for fabricating a 3D-printed concrete composite anti-collision structure for a ship lock wall, comprising the following steps: S1. Preparation of UHPC impact-resistant layer (1) Mix 96% concentrated sulfuric acid and 68% concentrated nitric acid at a volume ratio of 3:1 to obtain a mixed acid solution, and cool it in an ice-water bath for later use; weigh and measure the multi-walled carbon nanotubes and the mixed acid solution at a material-liquid ratio of 2g:200mL; slowly add the multi-walled carbon nanotubes to the cooled mixed acid solution, stir evenly to obtain a mixture; place the mixture in a probe-type ultrasonic instrument, and sonicate it at a power of 400W for 3 hours under the conditions of ice-water bath cooling and reflux condensation, and monitor and maintain the temperature at 30°C throughout the process; after the reaction is completed, slowly pour the mixture into ice water to dilute it; then separate the solid and liquid by centrifugation or vacuum filtration to obtain a black solid; repeatedly wash the black solid with deionized water until the pH of the supernatant is neutral; put the product washed to neutral into a vacuum oven and dry it at 70°C for 18 hours to obtain multi-walled carbon nanotubes with oxygen-containing functionalized surfaces; Two parts of oxygen-functionalized multi-walled carbon nanotubes were weighed and added to a mixture containing four parts of polycarboxylate superplasticizer and 100 parts of water. Then, 0.8 parts of graphene oxide dispersion with a solid content of 4% were added. The mixture was ultrasonically treated at 700W for 35 minutes and then spray-dried to obtain carbon nanotube-graphene composite reinforced powder. (2) Polypropylene hollow microspheres with a particle size of 80 μm were mixed with 4% silane coupling agent ethanol solution at a material-liquid ratio of 1 mg: 7 ml and ultrasonically dispersed in a constant temperature water bath at 50 °C for 35 min with an ultrasonic power of 400 W to obtain a dispersion. After filtration, the dispersion was dried in a vacuum drying oven at 70 °C for 5 h to obtain modified polypropylene hollow microspheres with silane coupling agent on the surface. (3) Weigh 350 parts of silicate cement, 80 parts of silica fume, 70 parts of quartz powder, and 25 parts of modified hollow polypropylene microspheres and dry mix them evenly; then add 2 parts of carbon nanotube-graphene composite reinforcing powder, 100 parts of water and 10 parts of polycarboxylate superplasticizer, and stir for 3 minutes; finally add 90 parts of end-hook steel fiber, stir evenly, and prepare UHPC slurry. Integrated 3D printing: Printing is performed using a large concrete 3D printer under ambient temperature of 20℃ and humidity of 60%; the printing speed is controlled at 100mm / s; during the printing process, a parallel magnetic field of 0.5T is applied to tangentially align the steel fibers along the printing path; when the printing reaches a height of 40mm, a smart sensing network is formed by pre-embedded fiber optic grating sensors and piezoelectric ceramic sensors in a robotic arm, and printing continues until the thickness of the UHPC impact-resistant layer reaches 80mm; S2. Preparation of gradient transition layer A gradient transition slurry was prepared by mixing 350 parts silicate cement, 60 parts silica fume, 50 parts fly ash, elastic microspheres, steel fibers, and 2 parts silane coupling agent. The gradient batching mode of the multi-nozzle printing system was activated. Printing parameters were as follows: the top layer used a high-fiber formulation with 3.0% steel fiber and 5% elastic microspheres; the middle layer used a transition formulation with 1.6% steel fiber and 12% elastic microspheres; and the bottom layer used a high-elasticity formulation with 0.7% steel fiber and 16% elastic microspheres. Simultaneously, 15 parts by weight of microencapsulated repair agent (a mixture of epoxy resin microcapsules and curing agent particles) were injected via a side-feeding system. The printing path was controlled to obtain a concave hexagonal negative Poisson's ratio honeycomb structure with a printing thickness of 20 mm. S3. Preparation of foamed concrete energy-absorbing layer Weigh out 150 parts of rapid-hardening sulfoaluminate cement, 50 parts of fly ash, 50 parts of rubber granules, 2 parts of protein-based foaming agent, and 90 parts of water. Mix and stir at high speed to foam. Then add 30 parts of microencapsulated phase change material and stir at low speed until uniform. Start the third print head for printing, reduce the printing speed to 80 mm / s, and increase the ambient humidity to 85% RH. During the printing process, spray 15 parts of water-based polyurethane emulsion into the inner wall of the foam pores through the auxiliary nozzle. When the printing reaches the surface 40 mm range, add 12 parts of mixed fiber evenly through the spreading device. The printing thickness of the foamed concrete energy-absorbing layer is 120 mm. S4. Maintenance and Post-treatment Each component printed in steps S1, S2, and S3 is steam-cured for 20 hours at a temperature of 55°C and a humidity of ≥95%, and then naturally cured for 28 days. Example

[0046] A method for fabricating a 3D-printed concrete composite anti-collision structure for a ship lock wall, comprising the following steps: S1. Preparation of UHPC impact-resistant layer (1) Mix 98% concentrated sulfuric acid and 65% concentrated nitric acid at a volume ratio of 3:1 to obtain a mixed acid solution, and cool it in an ice-water bath for later use; weigh and measure the multi-walled carbon nanotubes and the mixed acid solution at a material-liquid ratio of 3g:200mL; slowly add the multi-walled carbon nanotubes to the cooled mixed acid solution, stir evenly to obtain a mixture; place the mixture in a probe-type ultrasonic instrument, and sonicate it at a power of 500W for 2 hours under the conditions of ice-water bath cooling and reflux condensation, and monitor and maintain the temperature at 40°C throughout the process; after the reaction is completed, slowly pour the mixture into ice water to dilute it; then separate the solid and liquid by centrifugation or vacuum filtration to obtain a black solid; repeatedly wash the black solid with deionized water until the pH of the supernatant is neutral; put the product washed to neutral into a vacuum oven and dry it at 80°C for 12 hours to obtain multi-walled carbon nanotubes with oxygen-containing functionalized surfaces; Weigh 2.5 parts of oxygen-functionalized multi-walled carbon nanotubes and add them to a mixture containing 6 parts of polycarboxylate superplasticizer and 100 parts of water. Then add 1.2 parts of graphene oxide dispersion with a solid content of 5%. Sonicate the mixture at 800W for 30 minutes and then spray dry to obtain carbon nanotube-graphene composite reinforced powder. (2) Polypropylene hollow microspheres with a particle size of 100 μm were mixed with 6% silane coupling agent ethanol solution at a material-liquid ratio of 1 mg: 8 ml and ultrasonically dispersed in a constant temperature water bath at 60℃ for 30 min with an ultrasonic power of 500 W to obtain a dispersion. After filtration, the dispersion was dried in a vacuum drying oven at 80℃ for 4 h to obtain modified polypropylene hollow microspheres with silane coupling agent on the surface. (3) Weigh 400 parts of silicate cement, 60 parts of silica fume, 100 parts of quartz powder, and 30 parts of modified hollow polypropylene microspheres and dry mix them evenly; then add 3 parts of carbon nanotube-graphene composite reinforcing powder, 120 parts of water and 8 parts of polycarboxylate superplasticizer, and stir for 5 minutes; finally add 150 parts of end-hook steel fiber, stir evenly, and prepare UHPC slurry. Integrated 3D printing: Printing is performed using a large concrete 3D printer under ambient temperature of 20℃ and humidity of 60%; the printing speed is controlled at 120mm / s; during the printing process, a 1.0T parallel magnetic field is applied to tangentially align the steel fibers along the printing path; when the printing reaches a height of 50mm, a smart sensing network is formed by pre-embedded fiber optic grating sensors and piezoelectric ceramic sensors in a robotic arm, and printing continues until the thickness of the UHPC impact-resistant layer reaches 100mm; S3. Prepare the gradient transition layer A gradient transition slurry was prepared by mixing 400 parts silicate cement, 80 parts silica fume, 60 parts fly ash, elastic microspheres, steel fibers, and 3 parts silane coupling agent. The gradient batching mode of the multi-nozzle printing system was activated. Printing parameters were as follows: the top layer used a high-fiber formulation with 2.5% steel fiber and 7% elastic microspheres; the middle layer used a transition formulation with 1.2% steel fiber and 10% elastic microspheres; and the bottom layer used a high-elasticity formulation with 0.5% steel fiber and 15% elastic microspheres. Simultaneously, 30 parts by weight of microencapsulated repair agent (a mixture of epoxy resin microcapsules and curing agent particles) were injected via a side-feeding system. The printing path was controlled to obtain a concave hexagonal negative Poisson's ratio honeycomb structure with a printing thickness of 30 mm. S4. Preparation of foamed concrete energy-absorbing layer Weigh out 250 parts of rapid-hardening sulfoaluminate cement, 100 parts of fly ash, 80 parts of rubber granules, 5 parts of protein-based foaming agent, and 120 parts of water. Mix and foam at high speed. Then add 40 parts of microencapsulated phase change material and stir at low speed until homogeneous. Start the third print head for printing, reduce the printing speed to 80 mm / s, and increase the ambient humidity to 85% RH. During the printing process, spray 10 parts of water-based polyurethane emulsion into the inner wall of the foam pores through an auxiliary nozzle. When the printing reaches a surface area of ​​40 mm, add 15 parts of mixed fiber evenly through a spreading device. The printing thickness of the foamed concrete energy-absorbing layer is 200 mm. S5. Maintenance and Post-treatment Each component printed in steps S2, S3, and S4 is steam-cured for 28 hours at a temperature of 65°C and a humidity of ≥95%, and then naturally cured for 28 days. Example

[0047] The specific assembly method of the composite material layer obtained in the above embodiments on the surface of the lock wall and the verification of the intelligent monitoring function are described in detail.

[0048] The aforementioned composite material layer has four embedded permanent magnet connectors (made of NdFeB material, with a surface magnetic strength of 0.5T), arranged in a rectangular pattern. During the construction of the lock wall, stainless steel damping grooves are pre-embedded. The grooves are 100mm wide and 150mm deep, with an 8mm thick neoprene rubber pad adhered to the bottom. Before assembly, the damping grooves are filled with 3mm diameter steel shot damping particles, with the filling rate controlled to be above 80% of the groove volume.

[0049] The components of the prepared composite material layer are transported to the installation position by a floating crane, and their attitude is adjusted so that the permanent magnet connector is aligned with the damping groove. After overcoming the attraction of the permanent magnet, the permanent magnet connector is pushed into the damping groove. Under natural conditions, the composite material layer adheres to the surface of the gate wall.

[0050] Collision protection effect: Impact process: When impact energy is applied to the UHPC impact-resistant layer, the shock wave is first absorbed by the carbon nanotubes and steel fibers; then the stress wave is transmitted to the gradient transition layer, and the negative Poisson's ratio honeycomb structure undergoes inward contraction deformation.

[0051] Damping energy dissipation: The composite material layer shifts backward as a whole, and the permanent magnet connector on the back overcomes the magnetic force to slide in the groove and squeeze the steel shot damping particles; the steel shot undergoes intense friction and rolling, generating a significant hysteresis damping effect, converting the remaining kinetic energy into heat energy, thus reducing the peak force transmitted to the gate wall body.

[0052] Intelligent monitoring and self-repair effects: Monitoring: At the moment of impact, the fiber optic grating sensor embedded in the UHPC impact-resistant layer captures the wavelength drift signal, and the piezoelectric ceramic sensor senses the amplitude and arrival time of the stress wave. The system calculates the impact location and damage level in real time and sends an early warning signal.

[0053] Self-healing effect: After impact, several microcracks appear in the gradient transition layer; under humid conditions, the epoxy resin released by the microcapsule rupture flows into the cracks under capillary action and comes into contact with the latent curing agent; after 7 days of curing, ultrasonic testing can reveal that the cracks are filled with polymer, and the strength of the healed area is restored to at least 50% of the original strength.

[0054] Although the present invention has been specifically shown and described in conjunction with preferred embodiments, there are many methods and approaches to implement this technical solution. The above description is only a preferred embodiment of the present invention. It should be noted that any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without departing from the principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A 3D-printed concrete composite anti-collision structure for lock walls, characterized in that: It includes a composite material layer disposed on the surface of the lock wall via connecting components. The composite material layer comprises, from the outside to the inside, a UHPC impact-resistant layer, a gradient transition layer, and a foamed concrete energy-absorbing layer. The UHPC impact-resistant layer, by weight, comprises: 350-400 parts silicate cement, 60-90 parts silica fume, 70-120 parts quartz powder, 25-45 parts modified hollow polypropylene microspheres, 80-150 parts hook-shaped steel fibers, 1-5 parts modified multi-walled carbon nanotubes, 8-15 parts polycarboxylate superplasticizer, and 90-120 parts water. The gradient transition layer, by weight, comprises: 300-400 parts silicate cement, 50-80 parts silica fume, 40-60 parts fly ash, 20-60 parts elastic microspheres, 20-80 parts steel fiber, 10-30 parts microencapsulated repair agent, and 1-3 parts silane coupling agent. The foamed concrete energy-absorbing layer, by weight, comprises: 150-300 parts of rapid-hardening sulfoaluminate cement, 50-120 parts of fly ash, 50-80 parts of rubber particles, 20-40 parts of microencapsulated phase change material, 2-5 parts of protein-based foaming agent, 5-20 parts of waterborne polyurethane emulsion, 5-15 parts of mixed fibers, and 75-150 parts of water.

2. The 3D-printed concrete composite anti-collision structure for lock walls according to claim 1, characterized in that: The modified hollow polypropylene microspheres in the UHPC impact-resistant layer are prepared as follows: 50-100 μm hollow polypropylene microspheres are mixed with a 2-6% (w / w) silane coupling agent ethanol solution at a material-to-liquid ratio of 1 mg: 5-8 ml. The mixture is ultrasonically dispersed in a constant temperature water bath at 40-60℃ for 30-40 min at an ultrasonic power of 300-500 W to obtain a dispersion. After filtration, the dispersion is dried in a vacuum drying oven at 60-80℃ for 4-6 h to obtain modified hollow polypropylene microspheres coated with a silane coupling agent.

3. The 3D-printed concrete composite anti-collision structure for lock walls according to claim 1, characterized in that: The modified multi-walled carbon nanotubes in the UHPC impact-resistant layer are prepared as follows: acid-treated multi-walled carbon nanotubes are dispersed in an aqueous solution containing polycarboxylate superplasticizer, and a graphene oxide dispersion with a solid content of 2-5% is added. The mixture is ultrasonically treated at 500-800W for 30-60 minutes and then spray-dried to obtain carbon nanotube-graphene composite reinforced powder. The mass ratio of multi-walled carbon nanotubes, polycarboxylate superplasticizer, graphene oxide dispersion, and water is 1.5-2.5:4-6:0.8-1.2:

100.

4. The 3D-printed concrete composite anti-collision structure for lock walls according to claim 3, characterized in that: The acidification treatment method for multi-walled carbon nanotubes includes the following steps: S1.

1. Mix 95-98% concentrated sulfuric acid and 65-68% concentrated nitric acid at a volume ratio of 2-4:1 to obtain a mixed acid solution, and cool it in an ice-water bath; S1.

2. Slowly add multi-walled carbon nanotubes to the cooled mixed acid solution from step S1.

1. The ratio of multi-walled carbon nanotubes to the mixed acid solution is 1-3 g : 200 mL. After stirring evenly, a mixture is obtained. The mixture is then ultrasonically treated at a power of 300-500 W for 2-4 hours under ice-water bath cooling and reflux conditions, with the temperature monitored and maintained at 20-40°C throughout the process. After the reaction is complete, the mixture is slowly poured into ice water for dilution. Then, solid-liquid separation is performed by centrifugation or vacuum filtration to obtain a black solid. S1.

3. The black solid obtained in step S1.2 is repeatedly washed with deionized water until the pH of the supernatant is neutral. The product that has been washed to neutrality is placed in a vacuum oven and dried at 60-80°C for 12-24 hours to obtain oxygen-functionalized multi-walled carbon nanotubes.

5. The 3D-printed concrete composite anti-collision structure for lock walls according to claim 1, characterized in that: In the gradient transition layer, the microencapsulated repair agent includes epoxy resin microcapsules with a particle size of 100-200 μm and dicyandiamide latent curing agent with a particle size of 50-80 μm, with a mass ratio of epoxy resin microcapsules to dicyandiamide latent curing agent of 5-7:

1.

6. The 3D-printed concrete composite anti-collision structure for lock walls according to claim 1, characterized in that: The gradient transition layer adopts a three-segment gradient structure consisting of a surface layer, an intermediate layer, and a bottom layer. The surface layer is close to the UHPC impact-resistant layer, and the bottom layer is close to the foamed concrete energy-absorbing layer. From the surface layer to the bottom layer, the volume content of steel fibers decreases sequentially, while the volume content of elastic microspheres increases sequentially.

7. The 3D-printed concrete composite anti-collision structure for lock walls according to claim 6, characterized in that: In the gradient transition layer, the volume content of steel fibers in the surface layer is 2.5-3.5%, and the volume content of elastic microspheres is 5-7%; the volume content of steel fibers in the intermediate layer is 1.2-2.0%, and the volume content of elastic microspheres is 10-14%; and the volume content of steel fibers in the bottom layer is 0.5-1.0%, and the volume content of elastic microspheres is 15-18%.

8. The 3D-printed concrete composite anti-collision structure for lock walls according to claim 1, characterized in that: It also includes one or more of the following features: (1) The thickness of the UHPC impact-resistant layer is 60-100 mm, and the density is 950-1050 kg / m³. 3 ; (2) The gradient transition layer has a thickness of 20-30 mm and a density of 800-900 kg / m³. 3 ; (3) The foamed concrete energy-absorbing layer has a thickness of 100-200 mm and a density of 350-500 kg / m³. 3 ; (4) An intelligent sensing network composed of fiber optic grating sensors and piezoelectric ceramic arrays is embedded in the UHPC impact-resistant layer; (5) The connecting component includes a permanent magnet connecting seat pre-embedded at the bottom of the composite material layer and a damping groove pre-embedded in the lock wall. A permanent magnet is fixed on the permanent magnet connecting seat and the permanent magnet connecting seat is slidably embedded in the damping groove.

9. A method for preparing a 3D-printed concrete composite anti-collision structure for a lock wall as described in any one of claims 1 to 8, comprising the following steps: S1. Preparation of UHPC impact-resistant layer Silicate cement, silica fume, quartz powder, and modified hollow polypropylene microspheres are dry-mixed evenly. Then, modified multi-walled carbon nanotubes, hooked steel fibers, polycarboxylate superplasticizer, and water are added and stirred to obtain UHPC slurry. The UHPC slurry is fed into a 3D printer, and the first print head prints at a speed of 80-120 mm / s. During the printing process, a magnetic field of 0.5-1T is applied, and fiber optic grating sensors and piezoelectric ceramic arrays are embedded simultaneously. S2. Preparation of gradient transition layer After the UHPC impact-resistant layer in step S1 is printed to the set height, the second print head and the batching system are started to mix silicate cement, silica fume, fly ash, elastic microspheres, steel fibers and silane coupling agent to form a gradient transition slurry for printing. The flow rate of steel fibers and elastic microspheres is dynamically adjusted according to a three-stage gradient ratio to control the printing path to form a negative Poisson's ratio honeycomb structure. Microencapsulated repair agent is added online before the slurry is extruded and printed to the designed thickness. S3. Preparation of foamed concrete energy-absorbing layer After the gradient transition layer is printed in step S2, the third print head is started to mix and stir the rapid-hardening sulfoaluminate cement, fly ash, rubber particles, microencapsulated phase change material, protein foaming agent and water to make foam concrete slurry for printing; at the same time, during the printing process, waterborne polyurethane emulsion is sprayed into the inner wall of the foam pores through the auxiliary nozzle, and mixed fibers are added in the surface 30-50mm range through the spreading device. S4. Maintenance and Post-treatment Each component printed in steps S1, S2, and S3 is steam-cured, then standard-cured for 28 days. Finally, each component is floated to the installation location and installed on the gate wall surface using connecting components.

10. The method for preparing the 3D-printed concrete composite anti-collision structure for the lock wall according to claim 9, characterized in that: In step S4, the steam curing temperature is 55-65℃, the humidity is ≥95%, and the curing time is 20-28 hours.

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