The CNC H/I-beam cold bending machine can realize the cold forming of the I-beam arch. The welding of steel frame processing shall not have false welding, and the surface of the welding seam shall not have defects such as cracks and welds.
Each steel frame of the I-beam cold bending machine is cold-formed and placed on the concrete floor after the completion of the processing. The peripheral assembly tolerance is ±3cm and the plane warpage is less than 2cm. The steel frame is erected in time after excavation or concrete spraying.
H/I-beam steel arch erection requirements
Remove imaginary and debris under the feet before installation. Steel frame installation tolerance: steel frame spacing, lateral position and elevation are not more than ±5cm from the design position, and the verticality error is ±2°.
The steel frame can be assembled outside the excavation surface, and the steel frames are connected by bolts, and the connecting plates are closely attached.
Wedges are made with steel wedges or concrete precast blocks every 2m along the outer edge of the steel frame.
The steel frame feet are placed on a solid foundation. During the construction process, steel plates and sleepers should be laid under the arch to increase the force area to ensure that the steel arch does not sink. The steel frame is placed as close as possible to the surrounding rock and welded firmly to the anchor. The steel frames are connected longitudinally according to the design.
The arch of the steel arch is set with a locking bolt (or Φ42mm locking anchor) with a diameter of Φ25mm. The length of the anchor (tube) is not less than 4m, and the number is 2~4. After the lower half is excavated, the steel frame is grounded in a timely manner and closed into a ring.
The steel frame is integrated with the shotcrete, and the gap between the steel frame and the surrounding rock is filled with sprayed concrete; all forms of steel frame are covered by shotcrete, and the thickness of the protective layer is not less than 20 mm.
The H/I-beam steel arch frame is made of I20a steel with a longitudinal spacing of 560m. It is divided into seven sections according to the design.
2. Construction process
1) On-site production and processing: The steel frame processing site is hardened with C15 concrete, and the large sample is released according to the design. The allowance for welding shrinkage and the machining allowance for cutting are reserved during the lofting, and the cold forming is required to be accurate in size and rounded in shape. After the processing, try to spell, the contour error along the perimeter of the tunnel should not exceed 3cm. The units of the steel frame are bolted, and the error between the center of the bolt holes is not more than ±0.5cm. When the steel frame is laid flat, the plane warpage should be less than ±2cm.
2) Erection process requirements: The steel frame should be placed on a stable foundation. During the construction, the original foundation of 0.15~0.2m is reserved at the footing. When the erection is set, the groove is placed in place. The weak part is provided with channel steel at the footing to increase the base. Carrying capacity. The plane of the steel frame is perpendicular to the center line of the tunnel. During the installation process, there should be a riding pad when there is a large gap between the steel frame and the initial spray layer. The contact distance between the steel frame and the surrounding rock (or the block) should not exceed 50 mm. The steel frame shall be welded with the anchor rod, and the longitudinal connection steel bars of Ф22cm shall be arranged between the steel frames, and the circumferential spacing shall be set at 0.5m. After the steel frame is installed, it is positioned with the lock anchor, and the concrete operation is carried out as soon as possible, and the whole is covered to make the steel frame and the shotcrete work together.
Conctact person:Serena.Xu
2022.3.30