Steel support construction technology

The foundation pit uses bored piles and internal supports as the foundation pit enclosure structure. The supports at the corners and variable sections of the foundation pit are diagonal supports, and the rest are set as opposite supports, except for the first steel support, which is directly supported on the top crown beam of the pile. In addition, the rest are equipped with shaped steel purlins. For the convenience of construction, the steel pipes are required to avoid the central columns of the main structure while meeting the spacing requirements. At the same time, in order to ensure the stress of the diagonal braces, triangular shear blocks are installed on the steel purlins corresponding to the diagonal braces. , ensure that the stress surface is orthogonal to the diagonal brace.

Support erection process method
Before the steel support enters the site, it is necessary to conduct a comprehensive inspection and acceptance, especially to strengthen the length of the steel pipe, the wall thickness and the quality inspection of the weld of the steel pipe joint.
Construction points for the installation of steel support system
1. The foundation pit is excavated vertically in layers, following the principle of support first and excavation later, and the support installation is closely integrated with the earthwork construction. In the section where the earthwork is excavated to the design elevation, install and apply prestress in time to make it play a supporting role in time.
2. The steel pipe cross brace is divided into sections according to the design length, and part of the length is equipped at the same time. The pipe sections are bolted with flanges and high-strength bolts. At the same time, the two ends of each cross brace are respectively equipped with movable ends and fixed ends.
3. The symmetry of the steel pipe ensures that both ends are synchronized. The diagonal braces must ensure that the angle of the shear block is consistent with the oblique angle, and are orthogonal to the steel purlins. After the steel pipe cross braces are installed, prestress is applied in time.

4. The combined jacks are preloaded symmetrically and synchronously, and loaded in stages. In order to ensure symmetrical loading, external T-shaped valves can be connected to the combined jacks through the same hydraulic pump station.
5. All support connections should be tight, and the steel plates directly bearing pressure should be milled flat, and the bolts should be tightened to prevent eccentric compression of steel pipe supports. In particular, check the steel pipe support wedges, if any looseness, re-wedge in time.
6. The steel pipe supports and steel purlins are steel components, and the welding quality must be ensured. The steel purlins and support heads at the end diagonal braces are processed, welded and installed strictly according to the designed dimensions and angles to ensure that the support is axially stressed.
Support and protective measures
During the excavation of the foundation pit, it is necessary to prevent the multiple lifting operations of the excavation machinery from colliding with the support system. Strengthen monitoring during the construction process. If the axial force of the steel pipe horizontal brace is too large and the deflection deformation of the horizontal brace is close to the allowable value, measures such as adding temporary vertical supports should be taken. Prevent excessive flexural deformation of the horizontal braces, ensure stable stress on the steel supports, and ensure the safety of the foundation pit.
Technical measures to support dismantling
The disassembly process of the support system is actually the "switching" process of the support. In other words, the lateral soil pressure borne by the steel pipe cross braces is transferred to the permanent support structure or other temporary support structures.