Flexible Tent Duct

Flexible tunnel structures are primarily composed of steel frame construction, with flexible protective mesh laid as a layer for rockfall protection. This design maximizes the characteristics of the "soft overcoming hard" of the flexible protective mesh, enhancing the light transmittance of the tunnel and reducing the costs of lighting and ventilation during operation.

Overhanging;棚架式

System Type and Features

Overhanging arm

Similar to a masonry shed cave with only an interior wall and no external support.

The passive protection system, installed in a special form on nearly vertical slopes, will move outward to the protected area after the falling rocks impact the flexible net below, either by bouncing or rolling, ensuring the covered area is shielded from falling rock hazards.

Other than the connection relationships between certain components being different from the passive protection system, the constituent elements can be completely the same.

Achieves the same level of protection as passive protection systems.

Ø Usually, there is no need to clean falling rocks.

Only capable of protecting narrow areas at the base of near-vertically inclined slopes.

Tunnel

Similar to a masonry cave with both interior walls and outer supports.

The gate frame is combined with a flexible roof, which can also utilize rock walls as support in special terrain conditions (flexible roofs may also be required on the mountain side). After falling rocks impact the flexible roof, they either bounce off or remain on it, ensuring the covered area is protected from falling rock hazards.

The economically viable portal frame has a lower stiffness and limited protective level.

It is typically suitable for pedestrian pathways threatened by small rockfalls or flying stones.

Tent-style

Similar to masonry cut-and-cover tunnel.

Ø The enclosed structure composed of arch supports and surrounding flexible nets isolates falling or flying rocks outside the closed area, ensuring the safety of pedestrians or facilities within the closed area.

Compared to masonry cut-and-cover tunnels, the structure has a very low self-weight, requiring less load-bearing capacity from the foundation or the structure below it. Construction and installation are quick, and the investment is smaller.

Compared to masonry materials, steel is more expensive per unit. Under the current technological conditions, the economic arches and their connections have lower stiffness, making it difficult to match the impact resistance of flexible meshes, and the protective level is limited.

Ø Rockfalls may remain on the flexible net, leading to irreversible deformation of the net, especially during the moment of impact when significant deformation beyond the limit may occur.

Suitable for protection against smaller rockfalls or flying rocks under various complex conditions, particularly for bridge surface rockfalls or flying rocks, but not suitable for protection on electrified railway lines.

System Evaluation

A flexible protective structure composed of a flexible net and its supporting structure, designed to isolate falling or flying rocks outside of its covered or enclosed area.

The structural form, rockfall protection principle, and applicable conditions are similar to traditional masonry tunnel or open-cut tunnels, but feature a rockfall protection structure with flexible or combined flexibility and rigidity characteristics.

In steep, complex terrain areas where the source and path of falling rocks are extremely difficult to predict, flexible shed tunnels act as a safety umbrella, ensuring the safety of pedestrians and various facilities under their protection.

The inherent defects of the wire rope net are the root cause of numerous limitations in such systems.

The fixed-node interlaced weaving method allows flexibility only from the steel wire rope itself, and the mesh's deformation capability depends on the mechanical deformation of the wire rope material. It lacks the ability to self-adapt to loads, resulting in weak impact resistance. Its economically feasible high protection level is only 750kJ.

The node cross buckle's connection capability is significantly lower than that of wire rope, which may lead to relative movement or separation between the crossed wire ropes in extreme conditions.

Electroplated zinc cross clips have significantly weaker corrosion resistance than steel wire ropes.