4 Functions of Pipe Roof Support of Tunnel Excavation

The fore-piling is a kind of supporting method applied to the tunnel, which plays an important role in the construction of a soft rock tunnel through the broken zone and weak stratum, and lays a solid foundation for the subsequent tunnel excavation. The common supporting materials are ordinary steel pipes and self-drilling anchor bolts. This blog will introduce the function of the tunnel pipe-shed method, and a new technique of tunnel construction development.


Functions of Pipe-shed Support in Tunneling

The pipe-shed method is mainly used in the surrounding rock deformation or the broken soft surrounding rock project with high requirements on the surface drop, such as gravel stratum, soft rock, rock pile, broken zone, and other sections. The steel pipe shed protection arranged in a circular direction along part or all of the tunnel section, at a distance apart, mainly plays the following role in the tunneling.

1.    Work As A Beam Camber

Beam camber refers to the formation of a ring-shell beam composed of dozens of steel pipes around the top of the tunnel, similar to an arch bridge. One end of the steel pipe is supported by the steel arch, and the other end is supported by the rock mass which has not been excavated. It can effectively restrain the surrounding rock from loosening or collapsing.

2.    Reinforcement

The function of the pipe-shed method is mainly reflected in injecting slurry into rock mass through hollow bars, bonding loose rock mass together. This helps strengthen the surrounding rock mass of the tunnel section and enhances the bearing capacity of the surrounding rock.

3.    Ring Groove

A pipe roof can reduce the damage to surrounding rock. In the tunnel excavation, some tunnel faces need to be blasted to break the rock. The self-drilling pipe roof can absorb the shock wave generated in the blasting, reduce the damage degree of the blasting to the surrounding rock and avoid collapse.

4.    More Secure

The pipe roof can provide a buffer if there is a collapse or grave fall during the construction for its better stiffness and supporting and strengthening for the tunnel structure. This method improves the progress of tunnel construction and ensures the safety of construction personnel.


Self-drilling Pipe Roof

The self-drilling hollow anchor bolt has been verified by many tunnel engineering practices, which fully embodies its advantages in broken tunnels which are prone to collapse.

Self-drilling anchor bolts are not always suitable for all terrain and need to be selected according to the actual situation. When the surrounding rock is broken and fully weathered, or in complex geological conditions, it is difficult for ordinary steel pipe drilling, which leads to low construction efficiency and slow construction progress is relatively slow.

However, the self-drilling pipe roof can be used as a temporary support in the tunnel excavation as a leading pipe shed to ensure the safety of construction personnel and construction equipment. After the construction of the main body of the tunnel is completed, the self-drilling anchor bolt can still remain in the rock mass and play a supporting role.


Self-drilling Pipe Roof Construction Process


The above is the introduction to the four functions of the pipe roof method. In a tunnel with complex geological conditions such as hole collapse and stuck drilling, the self-drilling pipe roof can be selected for construction, which is fast in drilling speed, time-saving and labor-saving, and good installation effect. If you have any questions about the use of self-drilling anchor bolts in tunnels, please contact sinorock@sinorockco.com.


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