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21
2025
-
04
Detailed Explanation of Safety Standards and Technological Requirements for Tunnel Construction
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Railway tunnel construction adheres to strict national standards to ensure engineering quality and safety. During the excavation of the tunnel openings, close attention must be paid to the stability of the slopes and the back slopes. If there are signs of slippage, the slope should be appropriately reduced. Support work is crucial; steel supports are used close to the tunnel opening, and advanced pipe sheds or anchor rods are used for reinforcement according to the surrounding rock conditions. The tunnel portal lining must be integrated with the overall internal construction, and the connection measures required by the design ensure structural stability. Backfilling of the open-cut section must be carried out in layers and symmetrically, with each layer not exceeding 0.3 meters in thickness, and the height difference of the soil surface controlled within 0.5 meters. Mechanical backfilling should be carried out after the concrete strength reaches a specific standard.
Rock tunnels use smooth blasting or pre-splitting blasting techniques to improve efficiency and reduce consumption. The full-face method is suitable for surrounding rocks of classes Ⅵ to Ⅳ, using deep-hole blasting; the step method and partial excavation method are suitable for softer or jointed surrounding rocks of classes Ⅳ to Ⅱ, and the circular excavation advance should not exceed 1 meter. Class Ⅰ surrounding rocks require special treatment before excavation, strictly controlling under-excavation to ensure the stability of the lining structure. During construction, the support settlement is adjusted according to the surrounding rock pressure to ensure the design thickness.
The blasting excavation advance depends on the surrounding rock conditions. For weak surrounding rocks, it is limited to 1 to 2 meters; for hard surrounding rocks, it depends on the blasting hole extension angle and over-excavation. The blasting explosive consumption is determined according to the excavation method and rock properties. The anchor rod diameter should be 15 mm larger than the rod body diameter. The sprayed concrete material must be clean, and winter construction should pay attention to temperature and concrete strength. Steel frame sprayed concrete uses specific steel bars and spacing. The arch frame spacing is set according to the tunnel characteristics, and the secondary lining can be demolded only after the strength reaches 2.5 MPa.
The design of the external roadbed of the tunnel should consider drainage and seepage prevention, and internal seepage should use drilling for concentrated drainage. Blind drains are set behind the lining, filled with hard stone chips to ensure smooth drainage. The waterproof strip joints use lap joints or composite methods according to the material, and the waterproof layer is laid in a circular manner. The selection of ventilation facilities and equipment should be determined according to the project conditions to ensure the safety of construction personnel and the working environment.
The slope transportation safety requirements set a stopper, and the vertical shaft loading uses a rock grabber to ensure that safety measures are in place. Tunnel construction uses mechanical ventilation, and suitable pipes are selected according to the length and conditions. During construction, the slope of the support structure and the support pipes must meet the regulations, and attention should be paid to transportation safety and the setting of temporary facilities.
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