Composite protection structure for resisting underwater explosion of gate dam and construction method

Abstract

The underwater explosion resistant composite protection structure for the gate dam mainly comprises a composite protection structure body installed on one side of the upstream face of the gate dam, the composite protection structure body comprises an outer foamed aluminum layer, an ultra-high-performance concrete layer is arranged on the inner side of the foamed aluminum layer, and one side of the ultra-high-performance concrete layer is fixed to the side wall of the gate dam in an adsorption mode through a suction cup. According to the underwater explosion resisting composite protection structure for the gate dam and the construction method, the underwater explosion resisting capacity of the gate dam can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of hydraulic structure protection, and in particular to a composite protective structure for dams and gates resistant to underwater explosions, and its construction method. Background Technology

[0002] Dams and sluices are critical control structures in water conservancy projects, widely used in flood control, water supply, irrigation, and navigation. Their structural safety directly affects the public safety and economic stability of downstream areas. As core facilities responsible for regulating and controlling water flow, dams and sluices are typically exposed to complex hydrological environments for extended periods, making their superstructures more susceptible to water erosion, dynamic loads, and stress concentration. Especially given the increasingly severe non-traditional security threats, dams and sluices face potential threats from extreme conditions such as underwater explosions and terrorist attacks. If structural instability occurs under the combined effects of underwater explosion shockwaves and high-speed water flow, resulting in gate damage or control failure, it could potentially trigger uncontrolled water flow and major secondary disasters, causing casualties and infrastructure damage downstream, with extremely serious consequences.

[0003] Existing blast-resistant protection technologies mainly include steel plate reinforcement, carbon fiber reinforcement, and bubble curtains. Although these methods improve the blast resistance of structures to some extent, they generally suffer from problems such as complex construction, poor adaptability, high cost, or insufficient fatigue resistance. For example, steel plates are prone to buckling and fatigue cracks after repeated blast impacts; carbon fiber materials are difficult to construct in underwater environments and do not have good initial impact energy absorption capacity; bubble curtains have limited and unstable attenuation effects on shock waves. These traditional methods mostly focus on performance improvement in one direction and lack efficient, lightweight, and easy-to-maintain integrated blast-resistant protection solutions, making them particularly difficult to adapt to complex underwater installation and service environments. Summary of the Invention

[0004] The technical problem this invention aims to solve is to provide a composite protective structure and construction method for dams to resist underwater explosions. Without damaging the original dam structure, it employs a double-layer composite explosion-proof protection system consisting of an outer buffer layer and an inner protective layer. This structure is fixed to the dam surface using suction cups with negative pressure. The outer layer uses aluminum foam to initially attenuate the shock wave energy, while the inner layer is ultra-high-performance concrete, providing terminal structural protection and effectively absorbing and dispersing residual explosive loads. The suction cup installation method has the advantages of being non-destructive, detachable, and convenient for underwater construction, solving the problems of complex construction and poor adaptability of traditional reinforcement methods. The overall structural design is reasonable and functionally synergistic, significantly improving the dam's ability to resist underwater explosions, while also possessing good stability and engineering applicability, making it of significant promotional value.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A composite protective structure suitable for underwater explosion protection of dams is installed on the water-facing side of the dam. The composite protective structure includes an outer foam aluminum layer, an inner ultra-high performance concrete layer, and one side of the ultra-high performance concrete layer is attached to the side wall of the dam by suction cups.

[0006] The thickness of the aluminum foam layer is 3cm–5cm, the density of the aluminum foam material is 0.3–0.6g / cm³, the porosity is 75–85%, and the compressive strength is greater than 8MPa.

[0007] The ultra-high performance concrete layer has a thickness of 2cm–3cm, a compressive strength of not less than 120MPa, and a tensile strength of not less than 8MPa.

[0008] The aluminum foam layer is bonded to the ultra-high performance concrete layer.

[0009] The overall elastic modulus of the composite protective structure is distributed in a gradient manner, with the elastic modulus of the outer foam aluminum layer being 2GPa-5GPa and the elastic modulus of the inner ultra-high performance concrete layer being 40GPa-50GPa.

[0010] A method for constructing a composite protective structure suitable for underwater explosion protection of dams includes the following steps: Step 1: Prepare aluminum foam board; Step 2: Fabricate ultra-high performance concrete slabs and combine suction cups with ultra-high performance concrete during the pouring process; Step 3: Adhere the aluminum foam board to the ultra-high performance concrete board with adhesive to form a whole protective module; Step 4: During construction, thoroughly clean the water-facing area of ​​the dam body that needs protection, removing attached materials, silt, and loose surface layers to ensure that the interface of the protective structure is flat and clean in order to achieve effective adhesion. Step 5: Subsequently, install the protective modules in sequence according to the design layout plan. Use suction cups to firmly attach each protective module to the dam surface with the help of water pressure, and check the tightness of the adhesion to ensure that the contact is tight and the force is uniform. Step Six: After the protective modules are installed, water-resistant sealant is used to fill and seal the gaps between the protective modules, so that multiple sets of protective modules form a composite protective structure. The composite protective structure forms a two-layer collaborative system of "outer buffer - inner protection".

[0011] Step one, the preparation process of the aluminum foam board specifically includes: S1. High-purity aluminum powder is selected as the base material, and 0.5%-1.0% by mass of titanium hydride powder is added as a foaming agent; S2. Thoroughly mix the aluminum powder and foaming agent in a planetary ball mill; S3. Subsequently, the mixed powder is pressed into a blank on a press, with a pressing pressure between 50-100 MPa; S4. After pressing, place the billet in a heating furnace and foam it at a temperature of 650–680℃. The foaming time is controlled at 15–25 minutes and the heating rate is controlled at 5–10℃ / min. S5. After foaming is completed, immediately cool the foamed aluminum to room temperature and anodize the surface. S6. After cooling and surface treatment, the aluminum foam is cut into sheets according to the design dimensions and its appearance and pore structure are inspected to ensure that the dimensional accuracy, porosity and mechanical properties of the sheets meet the requirements, and finally aluminum foam sheets that can be used for composite protective structures are obtained.

[0012] Step two, the preparation process of the ultra-high performance concrete slab specifically includes: S1. Use PO52.5 grade Portland cement as the main cementitious material, with silica fume accounting for 20-25% of the total cementitious material content, fly ash accounting for 10-15%, and quartz powder accounting for 15-20%; S2. Fine aggregate is high-quality quartz sand with a fineness modulus of 1.8-2.2, a maximum particle size of no more than 2.5 mm, and a mud content of less than 0.5%; S3. Add high-performance polycarboxylate superplasticizer at a dosage of 1.5-2.5% of the total amount of cementitious materials, and control the water-cement ratio at 0.16-0.20; S4. High-speed mixing process: First, dry mix the cementitious material for 30 seconds, add 70% water and all the water-reducing agent and mix for 2 minutes, then add quartz sand and continue mixing for 3-5 minutes; gradually add steel fibers; finally add the remaining water and mix until uniform. S5. High-frequency vibration is used in conjunction with manual troweling during pouring to ensure a smooth and dense surface; S6. Immediately after molding, cover with plastic film to keep moist. Demold after 24 hours, and then perform standard curing or steam curing to ensure that the compressive strength reaches more than 120MPa. S7. After the UHPC board is formed and cured, the metal flange of the suction cup is fixed to the back of the UHPC board by pre-embedded parts or bolt sleeves, so that the suction cup and the UHPC board form an integral structure, ensuring that it can reliably bear external forces and maintain the sealing and adsorption effect during underwater installation.

[0013] The adhesive used in step three is an epoxy resin-based waterproof structural adhesive.

[0014] In step three, each protective module measures 1m × 1m × 0.08m, and each protective module is equipped with 6 to 9 suction cups.

[0015] This invention provides a composite protective structure and construction method for dams resistant to underwater explosions, which has the following technical advantages: 1) This invention employs a double-layer composite structure, consisting of an outer layer of aluminum foam buffer and an inner layer of ultra-high performance concrete protective layer. Aluminum foam possesses excellent energy absorption and stress dispersion capabilities, rapidly dissipating the energy at the forefront of the shock wave in the initial stages of an underwater explosion, significantly reducing the peak value and rise rate of the shock wave, and effectively preventing localized pressure concentration. Ultra-high performance concrete, with its high strength, high toughness, and excellent crack control capabilities, forms the structural defense line, further weakening residual impact energy and preventing the shock wave from penetrating the dam structure. The two layers work synergistically, giving the overall system superior blast resistance, far exceeding that of single reinforcement methods or traditional thickened concrete structures.

[0016] 2) The outer layer of this invention uses foamed aluminum material, which has the characteristics of low density, high specific strength, and a combination of rigidity and flexibility. Compared with traditional steel plates or large-volume concrete protection measures, it significantly reduces the self-weight and additional load of the protection system, avoiding new structural stress concentration problems in the dam body. This lightweight design is particularly suitable for old dam bodies, thin-walled structures, or load-sensitive parts, ensuring that the original structure can continue to serve safely without strengthening the foundation.

[0017] 3) This invention employs a suction cup attachment system to directly adhere the composite protective structure to the dam surface, eliminating the need for traditional rigid connection methods such as drilling, welding, or pre-embedded anchors. This effectively avoids physical damage and stress disturbance to the original structure. The suction cup attachment system utilizes pressure-resistant rubber suction cups to achieve a firm fit through water pressure difference or mechanical fastening. The installation process requires no complex equipment and is easy to operate, making it particularly suitable for underwater or humid environments where construction conditions are limited. Compared to traditional methods, the suction cup attachment method offers advantages such as rapid deployment, reversible disassembly, and strong structural adaptability. It is not only suitable for the protection needs of new projects but also provides an efficient and safe solution for the rapid reinforcement and protection upgrade of existing hydraulic structures.

[0018] 4) The composite protection structure adopts a modular design, and each module can be independently disassembled and replaced. When part of the system is damaged or degraded, there is no need to dismantle the entire system; only the damaged part needs to be replaced, greatly reducing maintenance costs and downtime. The suction cup fixing structure also facilitates repeated use and replacement, supporting regular maintenance, condition monitoring, and partial upgrades during long-term service, improving the maintainability and lifecycle economy of the entire system.

[0019] 5) This invention utilizes the complementary properties of materials to design a "flexible in front, rigid in the back" response mechanism: aluminum foam provides flexible buffering and delays the impact time of shock waves, while ultra-high performance concrete (UHPC) provides high-strength rigid support, maintaining good structural integrity and ductility even under multiple impacts or high-intensity explosions. Compared to traditional rigid structures, this system has stronger fatigue resistance, damage resistance, and post-disaster recoverability, significantly enhancing the structural toughness and damage resistance of key facilities such as dams and gates under extreme loads.

[0020] 6) The structural form of this invention is highly versatile. Besides being suitable for blast protection of dam superstructures, it can also be widely applied to areas with high water or blast risks, such as pumping stations, sluice gates, water intakes, port revetments, underground passages, important municipal utility tunnels, and hydraulic structure facades. Its modular, lightweight, and detachable characteristics make it highly adaptable and can be promoted as a standardized component in various new construction or reinforcement projects, possessing broad market prospects and engineering application potential.

[0021] 7) Patent application number “202510471529.X”, entitled “A Composite Protective Structure, Preparation and Construction Method for Underwater Seepage Prevention and Blast Resistance of Concrete Gravity Dams” (Prior Document 1), is a patent previously applied for by our company. The difference between this application and the invention patent “A Composite Protective Structure, Preparation and Construction Method for Underwater Seepage Prevention and Blast Resistance of Concrete Gravity Dams” is as follows: 1. Differences in the technical objects (1) Reference document 1 takes a large-volume concrete gravity dam as the research object. Gravity dams resist water pressure with their own weight. They are usually thick and have strong integrity. However, the upstream water-facing side is affected by water erosion and seepage over a long period of time, which can easily become a weak part of the structure. In the event of an underwater explosion, the thinner upper area is most vulnerable to impact damage. Therefore, the gravity dam patent mainly achieves the dual functions of seepage prevention and explosion resistance by adding a reinforced concrete slab to the water-facing side of the dam body and pouring a modified hollow glass microsphere-asphalt concrete composite layer between it and the dam body.

[0022] This application focuses on the protection of sluice gates and dams. Unlike gravity dams, sluice gates and dams primarily function to regulate and control water flow. Their structures are relatively thin and subject to complex local stresses. In the event of an underwater explosion, the gates and their supporting components are highly susceptible to instability or damage, potentially leading to downstream water loss and major secondary disasters. Therefore, this application emphasizes "lightweight design, rapid installation, and non-destructive fixing" in its design. It achieves highly efficient protection for sluice gates and dams through a combination of "outer layer aluminum foam + inner layer UHPC + suction cup attachment".

[0023] 2. Differences in structure and materials Compare with document 1: 1) Outer layer: The outer layer is made of reinforced concrete slab with a strength grade of C30 or above, with a thickness of not less than 10 cm, and is fixed to the dam body by anchor bolts.

[0024] 2) Interlayer filling: Modified hollow glass microspheres-asphalt concrete is used, with a glass microsphere content of more than 15% in the volume. It reflects shock waves through sealed gas and has excellent seepage prevention properties.

[0025] 3) Overall characteristics: Once formed, this composite structure has the advantages of integrity and durability, which can resist seepage damage and weaken the propagation of explosive shock waves within the dam body.

[0026] In this application: 1) Outer layer: Foamed aluminum board, 3–5cm thick, low density (0.3–0.6g / cm³), high porosity (75–85%), with good energy absorption and diffusion capabilities, which can rapidly reduce the impact peak in the early stage of an explosion.

[0027] 2) Inner layer: Ultra-high performance concrete (UHPC) board, 2–3 cm thick, compressive strength ≥120 MPa, tensile strength ≥8 MPa, with extremely high toughness and crack control capabilities, and can withstand residual impact energy.

[0028] 3) Fixing method: The suction cup is used to attach to the dam surface under negative pressure, without the need for drilling, pre-embedded anchors or welding.

[0029] 4) Overall characteristics: The double-layer structure, which is flexible on the outside and rigid on the inside and lightweight, enables it to achieve efficient energy dissipation and structural protection within a limited thickness.

[0030] 3. Differences in construction and maintenance methods Compare with document 1: 1) Construction conditions: It must be carried out during the dry season to ensure that the dam surface is dry before the modified hollow glass microsphere-asphalt concrete can be poured.

[0031] 2) Construction steps: including anchoring and installing reinforced concrete slabs, heating, mixing and pouring asphalt concrete, curing and shaping, etc., the construction period is relatively long.

[0032] 3) Maintenance method: Once formed, the protective layer is firmly bonded to the dam body. Although it is highly durable, if there is any local damage, repair requires excavation and re-pouring, which makes maintenance complex and costly.

[0033] In this application: 1) Construction conditions: It can be installed directly in water or underwater environments without the need for dry seasons or drainage conditions.

[0034] 2) Construction steps: Modular prefabrication is adopted. On-site, only the surface of the dam body needs to be cleaned. Then, the "foam aluminum + UHPC + suction cup" modules are attached to the surface of the dam body one by one. The installation can be completed by filling the gaps between adjacent modules with sealant.

[0035] 3) Maintenance method: The modular structure facilitates partial replacement. If some modules are damaged, there is no need to disassemble the whole structure; only the damaged modules need to be replaced, resulting in a short maintenance cycle and low cost.

[0036] Advantages of this application: 1. Non-destructive installation, protecting the original structure. Traditional protective techniques (such as steel plate reinforcement, anchor bolt fixing, or concrete cladding) typically require drilling holes in the dam surface, embedding anchors, or welding. These construction methods inevitably cause secondary damage to the original structure, introduce new stress concentration points, and may even weaken the integrity of the dam concrete.

[0037] In contrast, this application employs a suction cup negative pressure fixing method, eliminating the need for destructive processing on the dam surface. The suction cups achieve a firm fit through water pressure difference and mechanical fastening, maintaining stability even in complex underwater environments. This method not only avoids damage to the original strength and durability of the dam body but also facilitates later restoration or disassembly, making it a truly "zero-destructive" installation solution. This characteristic is particularly important for dams and sluice gates that have been in service for a long time and where concrete is at risk of deterioration.

[0038] 2. Lightweight design reduces additional load. The protective structure in Comparative Document 1 uses a reinforced concrete slab with an asphalt concrete infill layer, resulting in a significant increase in overall thickness and weight. This would substantially increase the additional load on the upstream side of the dam. For older dams or thin-walled structures, excessive additional loads could cause new cracks or uneven settlement, posing a structural safety hazard.

[0039] This application emphasizes lightweight and high efficiency in its design: the outer layer uses aluminum foam (density only 0.3–0.6 g / cm³), and the inner layer uses thin UHPC panels (2–3 cm thick), with the overall weight of a single module being significantly lower than that of reinforced concrete structures. This lightweight design not only reduces secondary stress on the dam body but also facilitates installation and transportation by manual labor or underwater robots, greatly improving construction efficiency and operability. For large-scale hydraulic engineering facilities, this design reduces construction risks and ensures long-term structural stability.

[0040] 3. Modular design and maintainability reduce total lifecycle costs. Traditional monolithic protective layers (such as asphalt pouring layers or thickened concrete layers) require large-scale excavation and re-pouring once local damage or aging occurs, resulting in high maintenance costs, long construction cycles, and even shutdowns, affecting the normal operation of water conservancy projects.

[0041] This application adopts a modular design: each module is standardized in size (1m×1m×8cm) and consists of an aluminum foam board, a UHPC board, and suction cups for fixation. If a part of the module is damaged, it can be replaced individually without removing the entire protective layer. The suction cup fixing method of the modules also supports repeated disassembly and reassembly, significantly reducing maintenance cycles and costs. Combined with modular mass production, it can also reduce manufacturing costs and transportation difficulties, thereby achieving economic advantages throughout the entire life cycle.

[0042] 4. Dual-layer synergistic protection, a flexible and rigid energy dissipation system Outer layer aluminum foam: Its porous structure can rapidly absorb and diffuse the energy of the shock wave front in the early stage of the explosion, significantly reducing the peak value and rise rate of the shock wave and avoiding local stress concentration.

[0043] Inner UHPC layer: It has extremely high strength and toughness, and can withstand and disperse residual impact energy to prevent shock waves from penetrating the dam body.

[0044] This gradient stiffness distribution (2–5 GPa for the outer layer and 40–50 GPa for the inner layer) causes the shock wave to attenuate gradually during propagation, forming a smoother energy transfer path and greatly improving the blast resistance and toughness of the protective structure. Compared with a single material, this solution can maintain a stable protective effect under multiple impacts or high-explosion conditions.

[0045] 5. Wide range of applications and high promotional value. Although the patent is mainly applied to dams, its modular, lightweight, and detachable features make it well adaptable to a wider range of water-related and explosion-proof projects.

[0046] Applicable scenarios include: Hydraulic structures: dams, pumping stations, water intakes, spillways, etc.

[0047] Port and marine engineering: revetments, breakwaters, wharf pile foundations.

[0048] Municipal infrastructure: underground utility tunnels, subway entrances and exits, and urban flood control gates.

[0049] Military and security facilities: protection of waterborne warehouses, offshore platforms, and ship docks.

[0050] This wide applicability makes the patent not only a solution for dam protection, but also a standardized component that can be promoted to various new construction or reinforcement projects, with good market prospects and engineering value.

[0051] 6. Simple construction, adaptable to complex environments Comparative document 1 requires construction to be carried out during the dry season and involves a large amount of formwork installation, anchor drilling and pouring operations, resulting in a long construction period and complex procedures.

[0052] The construction features of this application are simple and quick: the modules are prefabricated in the factory and can be installed on site after transportation; during construction, only the surface of the dam needs to be cleaned and the modules can be fixed one by one with suction cups; underwater operations can also be carried out directly without the need for drainage or large-scale precipitation.

[0053] Furthermore, adjacent modules are connected by water-resistant sealing strips, ensuring the continuity and sealing of the overall protective layer. The entire construction process is highly mechanized with low reliance on manual labor, enabling rapid deployment even in complex hydrological environments and under limited construction windows, greatly enhancing the project's adaptability and emergency response capabilities. Attached Figure Description

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a cross-sectional schematic diagram of the present invention.

[0055] Figure 2 This is a cross-sectional schematic diagram of the composite protective structure in this invention.

[0056] Figure 3 This is a schematic diagram of the planar layout of the composite protective structure in this invention.

[0057] In the diagram: 1. Composite protection structure; 2. Dam; 3. Explosion source; 4. Foamed aluminum layer; 5. Ultra-high performance concrete layer; 6. Suction cup; 7. Normal water level a. Detailed Implementation

[0058] like Figure 1-3 As shown, a composite protective structure suitable for underwater explosion protection of dams is disclosed. The composite protective structure 1 is installed on the side wall of the dam 2 on the water-facing side. The composite protective structure 1 includes an outer foamed aluminum layer 4, an inner layer of ultra-high performance concrete 5, and one side of the ultra-high performance concrete layer 5 is attached to the side wall of the dam 2 by suction cups 6.

[0059] The thickness of the aluminum foam layer 4 is 3cm–5cm, the density of the aluminum foam material is 0.3g / cm³–0.6g / cm³, the porosity is 75–85%, and the compressive strength is greater than 8MPa. Aluminum foam possesses excellent porous structure and energy dissipation characteristics, enabling it to rapidly absorb and diffuse shock wave energy through its porous structure in the initial stages of an explosion, thus reducing the instantaneous pressure peak.

[0060] The ultra-high performance concrete layer 5 has a thickness of 2cm–3cm. This ultra-high performance concrete is composed of high-strength cement, silica fume, steel fibers, water-reducing agents, and special mineral admixtures. Its 28-day compressive strength is not less than 120MPa, and its tensile strength is not less than 8MPa. This layer material possesses high density and excellent fracture toughness, effectively resisting the residual energy in shock waves and preventing structural damage or the formation of through cracks.

[0061] Because of its high strength and toughness, ultra-high performance concrete has good crack resistance and residual energy absorption capacity, it can provide robust end protection for dam structures.

[0062] Multiple suction cups 6 are arranged on one side of the ultra-high performance concrete layer 5. The suction cups 6 are pressure-resistant rubber suction cups, with a negative pressure value maintained between 0.3MPa and 0.6MPa. The suction cups 6 form a tight seal with the dam surface through negative pressure adsorption. Specifically, they can be fixed to the upper part of the dam or key stress areas, ensuring the stability and sealing of the protective structure in the underwater environment. Simultaneously, they exhibit good gradient energy dissipation characteristics under the action of explosive shock waves. The suction cups 6 can be quickly installed and removed without damaging the dam.

[0063] Preferably, the aluminum foam layer 4 and the ultra-high performance concrete layer 5 are connected by an adhesive layer. Specifically, the surface of the aluminum foam material is specially treated and then bonded to the ultra-high performance concrete using an epoxy resin-based waterproof structural adhesive. This adhesive has excellent adhesion, water resistance, and resistance to explosive impacts, ensuring that the bond between the aluminum foam material and the ultra-high performance concrete does not peel off or shift under underwater explosive impacts.

[0064] Preferably, the suction cup 6 uses a large-size pressure-resistant rubber suction cup with a diameter of 120–150 mm as the fixing unit, which has a self-adhesion function and does not require an external negative pressure pipeline or vacuum pump station. The suction cup is attached to the surface of the underwater substrate by water pressure assistance or mechanical fastening. The water pressure assistance method relies on the ambient water pressure to create a pressure difference inside the suction cup to achieve firm adsorption. The system is densely and reasonably arranged, with 6 to 9 suction cups per square meter to ensure uniform stress and stable and reliable structure.

[0065] Preferably, the overall elastic modulus of the composite protective structure 1 is gradient-distributed, with the elastic modulus of the outer layer of aluminum foam being 2-5 GPa and the elastic modulus of the inner layer of ultra-high performance concrete being 40-50 GPa, thereby achieving an increase in stiffness from the outside to the inside and optimizing shock wave transmission and energy dissipation.

[0066] Preferably, the aluminum foam material in the aluminum foam layer 4 is prepared by the following steps: S1. High-purity aluminum powder (99.5% or higher) is selected as the base material, and 0.5%-1.0% by mass of titanium hydride powder is added as a foaming agent; S2. Mix the aluminum powder and foaming agent in a planetary ball mill for 30 minutes to ensure that the foaming agent is evenly dispersed in the aluminum powder; S3. Subsequently, the mixed powder is pressed into a blank on a press, with a pressing pressure between 50-100 MPa; S4. After pressing, the blank is placed in a heating furnace and foamed at a temperature of 650–680℃. The foaming time is controlled at 15–25 minutes and the heating rate is controlled at 5–10℃ / min to obtain a good pore structure and closed-cell rate. S5. After foaming, the foamed aluminum is immediately and rapidly cooled to room temperature, and then anodized to improve its corrosion resistance and long-term service stability. The resulting foamed aluminum material has good energy absorption capacity and structural uniformity, making it suitable for rapid attenuation and buffering protection against explosive shock waves.

[0067] S6. After cooling and surface treatment, the aluminum foam is cut into sheets according to the design dimensions and its appearance and pore structure are inspected to ensure that the dimensional accuracy, porosity and mechanical properties of the sheets meet the requirements, and finally aluminum foam sheets that can be used for composite protective structures are obtained.

[0068] Finally, after the aluminum foam is foamed, cooled, and surface-treated, it is cut into sheets (aluminum foam sheets).

[0069] The ultra-high performance concrete in the ultra-high performance concrete layer 5 is prepared by the following method and steps: S1. Use PO52.5 grade silicate cement as the main cementitious material, with silica fume accounting for 20-25% (by mass) of the total cementitious material, fly ash accounting for 10-15% (by mass), and quartz powder accounting for 15-20% (by mass); this setting can optimize the density and strength development of the cementitious system.

[0070] S2. The fine aggregate is high-quality quartz sand with a fineness modulus of 1.8-2.2, a maximum particle size of no more than 2.5 mm, and a mud content of less than 0.5%.

[0071] S3. Add high-performance polycarboxylate superplasticizer at a dosage of 1.5-2.5% of the total cementitious material, and control the water-cement ratio at 0.16-0.20; this ensures that the mixture has good workability and self-compacting properties.

[0072] S4. Use a high-speed mixing process: First, dry mix the cementitious material for 30 seconds; then, add 70% water and all the water-reducing agent and mix for 2 minutes; then add quartz sand and continue mixing for 3-5 minutes; subsequently, gradually add steel fiber (volume dosage 2%), sprinkling it in batches (2-3 times) while maintaining mixing to avoid agglomeration; finally, add the remaining water and mix until uniform.

[0073] S5. High-frequency vibration is used in conjunction with manual troweling during pouring to ensure a smooth and dense surface.

[0074] S6. Immediately after molding, cover with plastic film to retain moisture. Demold after 24 hours, and then perform standard curing for 28 days or steam curing: heat to 90-95℃ and maintain constant temperature for 72 hours to ensure that the compressive strength of the ultra-high performance concrete reaches or exceeds 120MPa, meeting the comprehensive requirements of the project for high strength and explosion resistance.

[0075] S7. After the UHPC board is formed and cured, the metal flange of the suction cup is fixed to the back of the UHPC board by pre-embedded parts or bolt sleeves, so that the suction cup and the UHPC board form an integral structure, ensuring that it can reliably bear external forces and maintain the sealing and adsorption effect during underwater installation.

[0076] The process of preparing, pouring, and curing UHPC results in ultra-high performance concrete slabs (UHPC slabs). Yes, silica fume, fly ash, quartz powder, and water-reducing agent are all expressed as a percentage (wt%) of the total mass of the cementitious materials. The steel fiber content is expressed as a volume percentage (vol%). The composite protection structure 1 is manufactured using a modular prefabrication method. Each protection module measures 1m × 1m × 0.08m (total thickness 5-8cm). On-site, each module is installed on the dam surface using suction cups. Adjacent protection modules are connected using special sealing strips to ensure the continuity and sealing of the overall protection layer. After installation, the suction force is tested using a negative pressure system to ensure that it meets the design requirements.

[0077] The construction process of the composite protective structure includes the following steps: A method for constructing a composite protective structure suitable for underwater explosion protection of dams includes the following steps: Step 1: Prepare aluminum foam board; Step 2: Fabricate ultra-high performance concrete slabs and combine suction cup 6 with ultra-high performance concrete during the pouring process; Step 3: Adhere the aluminum foam board to the ultra-high performance concrete board with adhesive to form a whole protective module; Step 4: During construction, thoroughly clean the water-facing area of ​​the dam body that needs protection, removing attached materials, silt, and loose surface layers to ensure that the interface of the protective structure is flat and clean in order to achieve effective adhesion. Step 5: Subsequently, according to the design layout plan, the protective modules are installed in sequence in a water environment. The suction cups are used to firmly attach each protective module to the dam surface with the assistance of water pressure, and the adhesion is tested to ensure tight contact and uniform force. Step Six: After the protective modules are installed, the gaps between the protective modules are filled and sealed with water-resistant sealant. The foam aluminum boards of multiple protective modules form the foam aluminum layer 4, and the ultra-high performance concrete boards of multiple protective modules form the ultra-high performance concrete layer 5. The composite protective structure composed of multiple protective modules forms a two-layer collaborative system of "outer buffer - inner protection".

[0078] Step five, the specific process of installing the protective module in a wet environment, includes: First, ultra-high performance concrete (UHPC) slabs are cast in sections using steel molds, typically 1m × 1m × 2–3cm thick. After curing, individual UHPC slabs are obtained with a flat surface. Following curing, holes are drilled at the designed locations on the back of the slabs, and the metal flanges of the suction cups are fixed to the back of the UHPC slabs using embedded parts or bolt sleeves. This creates an integral structure between the suction cups and the UHPC slabs, ensuring reliable load-bearing capacity and maintaining a sealed suction effect during underwater installation.

[0079] After foaming, cooling, cutting, and surface treatment, aluminum foam is processed into sheets of the same size as UHPC boards. To enhance adhesion, the surface of the aluminum foam sheets needs to be roughened or anodized. Subsequently, epoxy resin-based structural adhesives or polyurethane-modified epoxy adhesives are used to tightly bond the aluminum foam sheets to the UHPC boards, forming a composite structural unit of "outer buffer - inner protection," ensuring a strong interface, water resistance, and impact resistance.

[0080] The suction cup is equipped with a metal flange or bolt interface at the bottom, which is connected to the UHPC board by bolting or welding, thereby realizing the integration of the suction cup and the UHPC board. This method can ensure that the suction cup will not loosen or fall off during long-term service, and ensure the stability of the protection unit under the impact of underwater explosion.

[0081] After the above processes, each UHPC board is bonded to the aluminum foam board, and then, with the fixed suction cups, forms a complete protective module. Each module measures approximately 1m × 1m × 8cm, with a total thickness of 5–8cm. Each module is equipped with 6–9 suction cups to ensure even stress distribution and sufficient tensile strength during installation. The modular design facilitates mass production, transportation, and rapid deployment, while also supporting partial replacement and maintenance.

[0082] During construction, divers or underwater robots first clean the water-facing side of the dam, removing any attached materials and loose layers to ensure a smooth and clean surface. Then, the protective modules are positioned one by one at their designed locations, and suction cups are used to create negative pressure through water pressure difference, firmly adhering them to the dam surface. Water-resistant sealing strips or sealant are then used to fill the gaps between adjacent modules, ultimately forming a continuous, integrated composite protective layer that effectively resists underwater explosive impact loads.

Claims

1. A composite protective structure suitable for underwater explosion protection of dams and sluices, characterized in that: Installed on the water-facing side of the dam (2), the composite protective structure (1) includes an outer layer of aluminum foam (4), an inner layer of ultra-high performance concrete (5), and one side of the ultra-high performance concrete (5) is attached to the side wall of the dam (2) by suction cup (6).

2. The composite protective structure for underwater explosion protection of dams and sluices according to claim 1, characterized in that: The thickness of the aluminum foam layer (4) is 3cm–5cm, the density of the aluminum foam material is 0.3–0.6g / cm³, the porosity is 75–85%, and the compressive strength is greater than 8 MPa.

3. A composite protective structure suitable for underwater explosion protection of dams and sluices according to claim 1, characterized in that: The ultra-high performance concrete layer (5) has a thickness of 2cm–3cm, a compressive strength of not less than 120MPa, and a tensile strength of not less than 8MPa.

4. A composite protective structure suitable for underwater explosion protection of dams and sluices according to claim 1, characterized in that: The foamed aluminum layer (4) is bonded to the ultra-high performance concrete layer (5).

5. A composite protective structure suitable for underwater explosion protection of dams and sluices according to claim 4, characterized in that: The overall elastic modulus of the composite protective structure (1) is distributed in a gradient manner. The elastic modulus of the outer foam aluminum layer (4) is 2GPa-5GPa, and the elastic modulus of the inner ultra-high performance concrete layer (5) is 40GPa-50GPa.

6. A method for constructing a composite protective structure suitable for underwater explosion protection of dams according to claim 5, comprising the following steps: Step 1: Prepare aluminum foam board; Step 2: Fabricate ultra-high performance concrete slabs and combine the suction cup (6) with ultra-high performance concrete during the pouring process; Step 3: Adhere the aluminum foam board to the ultra-high performance concrete board with adhesive to form a whole protective module; Step 4: During construction, thoroughly clean the water-facing area of ​​the dam body that needs protection, removing attached materials, silt, and loose surface layers to ensure that the interface of the protective structure is flat and clean in order to achieve effective adhesion. Step 5: Subsequently, according to the design layout plan, the protective modules are installed in sequence in a water environment. The suction cups are used to firmly attach each protective module to the dam surface with the assistance of water pressure, and the adhesion is tested to ensure tight contact and uniform force. Step 6: After the protective modules are installed, water-resistant sealant is used to fill and seal the gaps between the protective modules, so that multiple sets of protective modules form a composite protective structure (1). The composite protective structure (1) forms a two-layer collaborative system of "outer buffer - inner protection".

7. A method for constructing a composite protective structure suitable for underwater explosion protection of dams according to claim 6, characterized in that: Step one, the preparation process of the aluminum foam board specifically includes: S1. High-purity aluminum powder is selected as the base material, and 0.5%-1.0% by mass of titanium hydride powder is added as a foaming agent; S2. Thoroughly mix the aluminum powder and foaming agent in a planetary ball mill; S3. Subsequently, the mixed powder is pressed into a blank on a press, with a pressing pressure between 50-100 MPa; S4. After pressing, place the billet in a heating furnace and foam it at a temperature of 650–680℃. The foaming time is controlled at 15–25 minutes and the heating rate is controlled at 5–10℃ / min. S5. After foaming is completed, immediately cool the foamed aluminum to room temperature and anodize the surface. S6. After cooling and surface treatment, the aluminum foam is cut into sheets according to the design dimensions and its appearance and pore structure are inspected to ensure that the dimensional accuracy, porosity and mechanical properties of the sheets meet the requirements, and finally aluminum foam sheets that can be used for composite protective structures are obtained.

8. A method for constructing a composite protective structure suitable for underwater explosion protection of dams according to claim 6, characterized in that: Step two, the preparation process of the ultra-high performance concrete slab specifically includes: S1. Use PO52.5 grade Portland cement as the main cementitious material, with silica fume accounting for 20-25% of the total cementitious material content, fly ash accounting for 10-15%, and quartz powder accounting for 15-20%; S2. Fine aggregate is high-quality quartz sand with a fineness modulus of 1.8-2.2, a maximum particle size of no more than 2.5 mm, and a mud content of less than 0.5%; S3. Add high-performance polycarboxylate superplasticizer at a dosage of 1.5-2.5% of the total amount of cementitious materials, and control the water-cement ratio at 0.16-0.20; S4. High-speed mixing process: First, dry mix the cementitious material for 30 seconds, add 70% water and all the water-reducing agent and mix for 2 minutes, then add quartz sand and continue mixing for 3-5 minutes; gradually add steel fibers; finally add the remaining water and mix until uniform. S5. High-frequency vibration is used in conjunction with manual troweling during pouring to ensure a smooth and dense surface; S6. Immediately after molding, cover with plastic film to keep moist. Demold after 24 hours, and then perform standard curing or steam curing to ensure that the compressive strength reaches more than 120MPa. S7. After the ultra-high performance concrete slab is formed and cured, the metal flange of the suction cup is fixed to the back of the ultra-high performance concrete slab through embedded parts or bolt sleeves, so that the suction cup and the ultra-high performance concrete slab form an integral structure, ensuring that it can reliably bear external forces and maintain the sealing and adsorption effect during underwater installation.

9. A method for constructing a composite protective structure suitable for underwater explosion protection of dams according to claim 6, characterized in that: The adhesive used in step three is an epoxy resin-based waterproof structural adhesive.

10. A method for constructing a composite protective structure suitable for underwater explosion protection of dams according to claim 6, characterized in that: In step three, each protective module measures 1m×1m×0.08m, and each protective module is equipped with 6 to 9 suction cups (6).

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