In the field of hydraulic engineering and ecological restoration, underwater installation of welded gabion boxes has become a core technology for shoreline protection, water depth regulation, and ecological habitat construction. Recently, a team of senior hydraulic engineers successfully completed the underwater welded gabion box installation project in an 18-meter-deep pond in a suburban ecological park, setting a benchmark for similar medium-deep water area construction projects. This report will detail the entire process of the project, from pre-construction preparation to on-site operation and post-installation inspection, decoding the key points and technical difficulties of underwater welded gabion box installation in 18-meter-deep water, with a focus on meeting the construction requirement of neat and uniform side-by-side laying.
Welded gabion boxes, made of high-quality galvanized steel or PVC-coated steel mesh through professional welding processes, are widely used in underwater engineering due to their superior corrosion resistance, structural stability, and ecological compatibility. Compared with ordinary gabion boxes, welded ones feature firmer joints and higher overall rigidity, which is more conducive to achieving neat and uniform laying effects. Unlike shallow water installation, the 18-meter-deep pond environment involves complex factors such as high water pressure, poor visibility, and difficult underwater operation, which put forward extremely high requirements for construction planning, equipment selection, team collaboration, and especially the control of laying uniformity. The project team stated that the success of this project lies in the strict implementation of a "preparation-first, precision-construction, full-inspection, and uniformity-focused" work strategy.
Pre-Construction Preparation: Laying a Solid Foundation for Underwater Operation
The pre-construction preparation stage is crucial for the smooth progress of underwater gabion box installation, accounting for nearly 40% of the total project cycle. The team carried out a series of detailed work from on-site investigation, material preparation to equipment debugging.
First, a comprehensive on-site investigation was conducted on the 18-meter-deep pond. Engineers used a multi-beam sonar detector to map the underwater terrain of the pond, accurately measuring the depth of each area, the flatness of the bottom, and the distribution of sludge and gravel. The detection results showed that the pond bottom had uneven terrain with a maximum height difference of 0.8 meters, and a 0.3-meter-thick sludge layer in some areas. Based on this, the team formulated a terrain leveling plan, using underwater excavators to level the pond bottom and remove excess sludge to ensure that the gabion boxes could be placed stably. At the same time, water quality testing was carried out, including water temperature, pH value, and dissolved oxygen content, to select diving equipment and construction time that are compatible with the water environment.
In terms of material preparation, the team selected welded gabion boxes with a specification of 2m×1m×2m (length×width×height) according to the project design requirements, which are adjusted from the previous volume calculation parameters to meet the actual construction needs. The welded gabion boxes are made of double-galvanized steel mesh with a mesh size of 10cm×12cm; their welded joints are reinforced to ensure strong corrosion resistance, load-bearing capacity, and structural integrity-key guarantees for neat side-by-side laying. Before transportation to the construction site, each welded gabion box was inspected for quality, including mesh integrity, coating adhesion, weld firmness, and dimensional accuracy (to avoid uneven laying caused by size deviations), to eliminate unqualified products. In addition, filling materials (graded gravel with a particle size of 5-10cm) were pre-processed, cleaned to remove impurities and dust, and dried to ensure that the filling density reaches 1.8 tons per cubic meter, which helps maintain the shape of the 2m-high welded gabion boxes and achieve uniform laying.
Equipment debugging is another key link in pre-construction preparation. The team equipped professional underwater construction equipment, including underwater video cameras, diving suits suitable for 20-meter-deep water, underwater communication devices, and lifting equipment. The diving suits are equipped with heating systems to solve the problem of low water temperature in deep water; the underwater communication devices adopt wireless ultrasonic technology to ensure real-time communication between divers and onshore command personnel. The lifting equipment uses a crane with a maximum load of 5 tons, and the lifting rope is a high-strength nylon rope with corrosion resistance and wear resistance. Before construction, all equipment was subjected to multiple commissioning tests, including load tests of lifting equipment and communication tests of underwater devices, to ensure that the equipment can operate stably in the 18-meter-deep water environment.
On-Site Construction: Precision Operation Overcoming Deep Water Difficulties
The on-site construction stage is the core of the entire project, and the team divided it into three key links: filling of gabion boxes, lifting and positioning, and underwater installation and fixing, to ensure precise operation at each step.
The filling of welded gabion boxes was carried out on the shore to avoid the impact of underwater operations on filling quality and to ensure the stability of the 2m-high structure. Workers filled the graded gravel into the welded gabion boxes in layers (each layer 50cm high for easy compaction), and used a vibrator to compact each layer of gravel to ensure that the filling density reaches 1.8 tons per cubic meter. For the 2m-high boxes, the filling process was divided into four layers to avoid uneven compaction caused by one-time filling. After filling, the top cover of the welded gabion box was fixed with steel wire ties, and the connection points (including the side joints of the box body) were reinforced to prevent the gravel from leaking during lifting and installation. Each filled welded gabion box was weighed (single box weight about 7.2 tons, calculated by volume × filling density: 2×1×2×1.8) and numbered to facilitate subsequent lifting and positioning management, and to match the load capacity of the 5-ton crane by arranging split lifting if necessary.
Lifting and positioning is a difficult link in deep water installation, and it is also the core to ensuring neat and uniform side-by-side laying of welded gabion boxes. Due to the poor visibility in 18-meter-deep water, the team adopted a "double positioning + spacing calibration" method combining onshore measurement and underwater video monitoring. First, onshore surveyors used total stations to mark the installation position and spacing of each welded gabion box, drew a detailed installation layout map, and marked the side-by-side alignment lines to ensure consistent spacing between adjacent boxes. Then, the crane lifted the filled welded gabion box to the water surface, and divers carried underwater video cameras and spacing gauges to dive to the installation position, guiding the crane to adjust the position and angle of the gabion box. During the lifting process, the lifting speed was strictly controlled at 0.5 meters per second to avoid shaking of the welded gabion box caused by excessive speed, which would affect the positioning accuracy and alignment effect. When the welded gabion box is close to the underwater installation position, the diver uses a special tool to fine-tune the position and check the spacing with adjacent boxes, ensuring that the deviation between the actual installation position and the design position is within 5cm, and the side-by-side laying is neat, uniform, and free of tilting or misalignment.
Underwater installation and fixing is the final key step to consolidate the neat and uniform laying effect of the 2m-high welded gabion boxes. After the welded gabion box is accurately positioned, the diver connects the adjacent boxes with high-strength steel wire ties (thicker than ordinary ties to bear the weight of the 2m-high structure). The connection points are set every 30cm both horizontally and vertically to ensure that the welded gabion boxes form a solid integral structure, enhancing the overall stability and preventing tilting of the high boxes. For the welded gabion boxes installed on the edge of the pond, the team used anchor piles with deeper embedding depth to fix them firmly, avoiding displacement caused by water flow and the self-weight of the 2m-high boxes. During the installation process, the diver continuously inspected the installation quality through the underwater video camera, including the flatness of the gabion box top surface, the firmness of vertical and horizontal connections, and the compactness of the filling material. If any problems such as local loosening are found, they are corrected immediately to ensure that each 2m-high welded gabion box meets the installation standards.
During the construction process, the team also paid attention to safety management. Divers worked in pairs, and each diving operation time was controlled within 40 minutes to avoid physical discomfort caused by long-term exposure to high water pressure. Onshore command personnel monitored the diver's physical condition and construction progress in real time through underwater communication devices and video cameras. Once an emergency occurs, the rescue team can be dispatched immediately to ensure the safety of the construction personnel.
Post-Installation Inspection: Ensuring Long-Term Stability of the Project
After the completion of the underwater installation of all 64 gabion boxes, the team carried out a comprehensive post-installation inspection to ensure the long-term stability and durability of the project.
First, underwater visual inspection was carried out. Divers used high-definition underwater video cameras to inspect each 2m-high welded gabion box one by one, focusing on the verticality of the box body, installation position, connection status of vertical and horizontal joints, and filling condition. The inspection results showed that all welded gabion boxes were installed in place, the connections were firm, there was no gravel leakage, and the verticality deviation was within 2cm per meter height. Then, the team used a depth gauge to measure the flatness of the top surface of the gabion boxes, and the maximum height difference was within 3cm, meeting the design requirements for neat side-by-side laying.
In addition, the team conducted a stability test. By observing the displacement of the gabion boxes under the action of water flow, it was confirmed that the gabion boxes did not shift, and the integral structure was stable. At the same time, the corrosion resistance of the gabion boxes was sampled and tested. The test results showed that the galvanized coating of the steel mesh was intact, and there was no corrosion phenomenon, which could meet the service life requirement of more than 20 years.
The person in charge of the project said that the successful completion of the 2m-high welded gabion box installation project in the 18-meter-deep pond provides valuable experience for similar deep-water and high-structure gabion installation projects. Compared with traditional underwater protection projects and ordinary-height gabion boxes, the 2m-high welded gabion boxes have stronger structural stability and better shoreline protection effect, while maintaining the advantages of low construction cost, strong ecological compatibility, and easy maintenance. They can not only play a role in shoreline protection and water depth regulation but also provide a more stable habitat for aquatic organisms with their larger volume, contributing to the ecological restoration of the pond.
Conclusion
Installing 2m-high welded gabion boxes in an 18-meter-deep pond is a systematic project that requires strict pre-construction preparation, precise on-site operation, and comprehensive post-installation inspection. The increase in height puts higher demands on filling compaction, lifting stability, and underwater connection firmness. From terrain investigation and material selection (matching high-strength welded gabion boxes) to equipment debugging (adapting to the weight of high boxes) and underwater construction, every link is crucial to the success of the project. This project not only demonstrates the professional technical level of the construction team but also promotes the application and development of high-structure welded gabion box technology in deep-water area engineering.
With the continuous improvement of ecological protection requirements, underwater gabion box installation technology will be more widely used in hydraulic engineering, ecological restoration, and other fields. It is believed that through the continuous optimization and innovation of construction technology, underwater gabion box projects will play a more important role in protecting the water ecological environment and promoting the sustainable development of water conservancy undertakings.
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