As urban infrastructure construction in China continues to advance, the number of engineering projects such as subway tunnels, underground utility tunnels, municipal deep foundation pits, and large underground parking garages has increased year by year. Controlling the deformation of surrounding rock and foundation pit sidewalls during deep foundation pit excavation and tunnel boring is a major challenge in project construction. As the core load-bearing component in foundation pit and tunnel support systems, steel struts have become the mainstream choice for underground engineering support due to their advantages of high load-bearing capacity, high stiffness, pre-applied axial force, easy assembly and disassembly, and reusability. Recently, multiple batches of our steel strut products have been shipped to municipal projects across various regions, serving foundation pit support and temporary tunnel support construction, helping underground projects proceed efficiently with stable product performance and flexible supply capacity.
Steel struts are generally manufactured from Q235B or Q355B seamless steel pipes or straight-seam steel pipes. The complete set of components includes fixed sections, adjustable sections, flange joints, jack supports, waler connectors, and other parts. Modular design is its greatest feature. Unlike one-time support materials, steel struts can be freely assembled according to the actual width of the foundation pit and the cross-sectional dimensions of the tunnel, with the total length fine-tuned through adjustable sections to adapt to different support spans. In the foundation pit excavation process, steel struts are used together with crown beams and walers. After installation, pre-applied axial force is applied via jacks to offset lateral earth pressure in advance, actively constraining foundation pit sidewall displacement, reducing soil settlement around the foundation pit, and lowering the risk of disturbance to surrounding roads, pipelines, and buildings from excavation. This is also a prominent advantage of steel struts over other support methods.
In the production process, our company strictly controls three core aspects of steel struts: weld seams, dimensional accuracy, and anti-corrosion treatment. Steel pipe raw materials are verified against material certificates upon arrival, with ultrasonic spot checks on internal defects to ensure the steel pipe body is free of cracks and meets wall thickness requirements. All welding processes are performed by certified welders. Flange-to-main-pipe butt welds are fully welded, and weld seams undergo visual inspection and non-destructive testing to eliminate welding defects such as incomplete fusion, slag inclusion, and porosity. Weld seams are the weak points in steel strut load-bearing; once welding fails to meet standards, cracking is highly likely under load, leading to support failure. After each steel strut is processed, the total length and flange coaxiality are uniformly calibrated to ensure smooth on-site assembly without misalignment or installation failure. Surfaces are uniformly treated with anti-corrosion paint, with primer and topcoat providing double-layer protection. Paint film thickness meets standards, slowing steel corrosion in humid underground environments and muddy foundation pit conditions, and extending product turnover service life.
On the construction site, steel struts demonstrate the characteristics of fast installation and fast removal. After foundation pit excavation reaches the support elevation, lifting, assembly, and pre-applied axial force can be completed in a short time, quickly forming a support system and shortening the exposure time of unsupported foundation pits. This is particularly critical for foundation pits in soft soil areas, where soft soil has strong flowability and the longer the exposure time, the higher the risk of uncontrolled deformation. After the main structure construction is completed and conditions for strut removal are met, force can be released in stages and removal carried out in sections. Components are sorted and recovered, and after inspection and rust removal, can be transferred to the next project for continued use, significantly reducing the client's support material procurement costs and aligning with green construction concepts.
Working conditions vary greatly across different projects, with different foundation pit depths, soil conditions, and surrounding protection requirements. Our company supports customized steel struts, with steel pipe specifications, support lengths, and flange styles adjustable according to design drawings, along with matching connection accessories. Meanwhile, our technical personnel can provide technical coordination with customers and construction units, communicating precautions during installation, pre-applied axial force, and strut removal, reminding construction units to apply axial force strictly according to design values, conduct proper support monitoring, and promptly identify hidden risks of support loosening and deformation.
Underground engineering involves high risks and strict controls, and the support system is a safety barrier. Our company will continue to deepen research and production of steel strut products, optimize processing techniques, stabilize supply cycles, and provide reliable steel strut support solutions for various underground engineering projects such as subways, utility tunnels, and municipal foundation pits, working together with construction units to safeguard the safety bottom line of foundation pit and tunnel construction.
