Construction methods for steel supports
Before the excavation of the foundation pit, sufficient quantities of materials such as steel pipe supports, flexible heads, brackets, and steel wire ropes should be prepared on site. After the steel pipe supports arrive, the quality of the pipes should be carefully checked in strict accordance with design requirements and relevant standards. It is strictly prohibited to use unqualified support materials.
Nov 14,2022
1. Construction Preparation Work
Before excavating the foundation pit, sufficient quantities of materials such as steel pipe supports, flexible heads, brackets, and steel wire ropes should be prepared on site. After the steel pipe supports arrive, the quality of the steel pipes should be strictly checked according to design requirements and relevant standards, and the use of unqualified support materials is strictly prohibited.
Steel Pipe Support: Use φ609 welded steel pipes with a wall thickness of 16mm. Both ends are connected with steel flanges with a diameter of 750mm.
Steel Purlins: Steel purlins are made of double-node 40 I-beams.
Steel Wedges: Made of manganese steel, with thicknesses of 2cm, 4cm, 6cm, 8cm, and 10cm.
High-Strength Bolts: Use M24 hexagonal head high-strength bolts, with a screw length of 10cm.
2. Support Installation
1) Steel Pipe Support Assembly
Due to the relatively small construction site, in order to reduce the time the foundation pit is unsupported and shorten the construction time of each support cycle, during the erection of the steel support frame: the steel supports should be pre-assembled outside the foundation pit, checked against the width of the pit, and then the assembled steel supports should be disassembled and hoisted into the pit in sections. After assembly is completed in the pit, they should be erected.
Connection of Support Steel Pipes: Use high-strength bolts to connect the support steel pipes. When using bolts for connection, symmetrical force must be applied to prevent eccentricity of the steel pipe supports.
2) Measurement Line, Support Positioning
When the excavation reaches 30cm below the bottom of the steel support, dedicated personnel should be organized immediately to measure, layout, and position the supports according to the design drawings. The allowable deviation for support positioning is: 2cm (horizontal position deviation), 1.5cm (height deviation). The installation height and horizontal position of the steel supports should be marked with red paint.
3) Chisel Out the Position of the Support Beam Rebar, Weld the Support Beam
After checking the elevation and plane position of the steel supports, in order to facilitate the positioning and fixing of the supports, a shelf device should be installed on the walls of the foundation pit and the walls on both sides. The shelf device is welded with a 2cm thick triangular steel plate on the main rebar of the wall. Each steel support has two support beams at both ends, and the effective welding length of the triangular steel plate to the main rebar of the wall should not be less than 25cm.
4) Secondary Protection and Anti-Fall Reinforcement After Erecting the Steel Support Frame
To prevent the steel supports from falling due to various reasons after installation, secondary protective reinforcement should be added at both ends of the steel supports. Use 20cm long expansion bolts and 1cm thick steel plates to make lifting ears, which are fixed into the wall. The suspension points are set 1 meter above the steel supports. Then, use φ14mm steel wire ropes to secure both ends of the steel supports and connect them to the angle steel lifting ears.
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