The role of the advance pipe roof support is to strengthen the surrounding rock, prevent the rock from falling and excessive deformation, and ensure the stability of the tunnel and construction safety. This requires not only reasonable tunnel construction methods but also reasonable parameters. Below are five factors that should be considered before pipe roofing construction.
Geological Condition
The advance pipe roof support is suitable for the following special geological conditions:
- When there are buildings on the ground or tunnels close to underground structures.
- In special sections such as extremely broken rock mass, gravel soil, or landslides.
- The groundwater activity is strong, resulting in a large area with high water content.
For tunnel excavation under these special conditions, the advance support of the pipe roof has a good supporting effect, which can control the influence caused by the excavation to the minimum range, and has a good effect on controlling the deformation of the surrounding rock.
Spacing of Pipe Roof
The advanced support of the pipe roof is mostly used in the area of loose gravel. If the spacing is too large, it will not only easily cause rock fall, but also the excessive load on the pipe roof, which is not conducive to the stability and safety of the pipe roof system. However, if the spacing is too small, it will inevitably increase the workload of pipe roof installation and affect the construction progress. The spacing is generally selected between 400 to 800 mm. If in the loose rock formation, it can take a smaller value.
Supporting Length of Pipe Roof
The longer the support length of the pipe roof, the more auxiliary time can be saved and the construction efficiency can be improved. However, due to the limitations of drilling equipment, drilling techniques, and flexible bending of steel pipes, if the length of the pipe roof is too long, it will be difficult to ensure the horizontal angle and alignment of the pipe roof. This will affect the construction quality. Generally, the support length of the pipe roof is range in 10~20m according to different geological conditions.
Pipe Roof Angle of Inclination
Excessive pipe roof camber will inevitably increase the consumption of supporting materials and causes waste. According to the calculation, the camber angle of the pipe roof should be 3° to 8° for the longitudinal spacing of the pipe roof group of 1 to 3 m. Generally, for simplicity, the camber angle of the camber angle can be taken as 5°.
Construction Scope
In order to consider economic factors, the construction length of the pipe roof can be shortened as much as possible without affecting the safety. The common length of construction can reach 80m.
For situations where the geological conditions are expected to be more complicated, test drilling should be carried out along the tunnel axis to obtain more detailed data to determine the length of the construction section of the pipe roof.
Summary
Above is the consideration factors for advance pipe roof. As a new tunnel pipe roofing technique, self drilling pipe roof can replace the traditional pipe roofs in a variety of easily collapsed formations, and solve the construction problems of hole collapse, sticking, and inability to insert ordinary pipe roof. Self drilling pipe roof system plays the role of advanced support, which can effectively reduce surface settlement and prevent collapse of surrounding rock. Sinorock self drilling pipe roof consists of hollow anchor bars and drill bits, has been applied to many tunnel pipe-roofing projects. For any queries or interests, welcome contact at: [email protected].