Steel supports for deep foundation pits in subway projects: the composition of the system

A crown beam is a reinforced concrete continuous beam set on top of the support structure surrounding the foundation pit. One of its functions is to connect all pile foundations (such as bored piles, rotary piles, etc.) to prevent the top edge of the foundation pit (shaft) from collapsing, and secondly to bear the level of the steel support (or reinforced concrete support) through the corbels squeeze force and vertical shear force, and the laitance on the top of the pile must be removed during the construction of the crown beam.

Purlin
The purlin is an important force-bearing component that can coordinate the stress and deformation between the support and the retaining wall structure. It can strengthen the integrity of the retaining wall and transfer the horizontal force it bears to the supporting components. Therefore, it needs to have a better Good self-stiffness and small vertical displacement. The first supporting purlin should be used as the ring beam of the enclosure wall as much as possible, and the top height of the enclosure wall can be reduced if necessary. If the purlin of the first support system cannot be used as a ring beam, a ring beam on top of the retaining wall should be set up. The function of the ring beam can connect discrete bored cast-in-place retaining piles, underground diaphragm walls and other retaining walls. It enhances the integrity of the retaining wall and helps reduce the top displacement of the retaining wall.
horizontal support
The horizontal support is the main component that balances the horizontal force on the outside of the retaining wall. It requires direct force transmission, good plane stiffness and even distribution.
vertical support
The function of steel columns and column piles is to ensure the longitudinal stability of the horizontal support, enhance the spatial rigidity of the support system, and bear the vertical load of the horizontal support, which requires good rigidity and small vertical displacement.

Steel support
Steel support refers to the use of steel pipes, H-shaped steel, angle steel, etc. to enhance the stability of engineering structures. Typically, they are slanted connecting members, most commonly in the herringbone and cross shapes. It is recyclable, economical and environmentally friendly. At present, steel supports are widely used for the protection of subway foundation pits. Support steel pipes with a diameter of 609mm and a wall thickness of 16mm are usually used to support the enclosure structure and prevent foundation pit collapse.
As our country's comprehensive national strength increases, our country's requirements for construction projects will only become higher and higher. From the perspectives of improving quality, reasonably accelerating the construction cycle, environmental protection and energy saving, the new steel support system has unique advantages in formwork reinforcement projects.
This new type of steel support system is a new green formwork reinforcement system. It is a reinforcement system based on liberating labor, reducing costs, and improving construction quality and efficiency. The assembly form breaks the traditional assembly method, and the operation is simpler and more convenient. It is used for the first time. , you can operate it freely after simple guidance.
The entire system can realize the one-time molding of walls and roofs, completely realizing the no-painting process for walls. The new steel support system is suitable for the construction of concrete structural walls, roof slabs, columns, beams, etc.

In addition, because the concrete poured with the new steel support system technology has a good look and feel, it can greatly save the cost of wall plastering, save the raw material consumption of cement and sand, reduce the use of turnover materials, and directly eliminate the common problems of wall plastering hollows and cracks. .