About Pipe Umbrella in Tunnel, You Need to Know These

by Simone S. sinorockco

In recent years, in the construction of tunnel engineering and mining engineering in my country, the pipe umbrella system has been widely used, and it has become one of the most effective advanced support methods when passing through loose and broken strata in underground engineering construction. The application of this technology not only simplifies the tunnel construction process, and accelerates the construction speed, but also greatly improves the construction safety and economic benefits.

However, in the current tunnel construction, it is also found that there are still unreasonable and inappropriate applications in the pipe umbrella support, which not only affects the supporting effect, but also often buries quality and safety hazards to tunnel construction, and even causes accidents. Although scholars have carried out many studies on the theoretical basis, numerical simulation, design calculation, etc. of the pipe umbrella system technology, and there have been many successful application examples, it has played a positive role in promoting the wide and effective application of the pipe umbrella system technology. , but it should also be noted that it is still urgent and meaningful to improve the advanced support technology of the tube shed to make its performance more effective.

There are various methods of advanced support. The pipe umbrella system has been widely used in tunnel engineering due to its simplicity of construction and timeliness of support effect.

Stress Variation of Pipe Shed in Advance Support

When the tunnel passes through the loose and broken rock layers, the goal of implementing the advanced support of the pipe shed is to limit the large deformation and displacement of the surrounding rock of the tunnel due to the tunnel excavation, to maintain the original state of the surrounding rock as much as possible, to maintain the stability of the tunnel, and to ensure construction safety. , to create good conditions for the excavation construction; at the same time to avoid excessive subsidence of the tunnel roof in the later stage, to ensure the long-term stability of the tunnel. Therefore, in the design and construction of the advanced support of the pipe shed, special attention should be paid to the force of the pipe shed at each construction stage to ensure that the pipe shed is stable at each stage without obvious deformation and displacement.

Pipe Shed Spacing

The advanced support of pipe sheds is mostly used in loose and broken rock formations. If the spacing is too large, it will not only easily cause large rocks to fall, but also the load on the shed pipes is too large, which is not conducive to the stability and safety of the pipe umbrella system. At the same time, large-diameter shed pipes will be used to improve the bearing capacity of the system, which will increase the difficulty of construction; however, if the spacing is too small, it will inevitably increase the workload of pipe shed installation and affect the construction progress. The spacing between the tube sheds can generally be selected between 400 and 800 mm; when the rock is broken and easy to flow, the smaller value is selected.

Inclination

In the pipe shed advanced support system, the shed pipe mainly bears the bending load; therefore, the pipe shed should be laid horizontally. However, due to construction reasons, the horizontal tube shed cannot ensure that the tunneling section remains unchanged when the tunnel is advanced. Therefore, in actual construction, the tube shed is inclined outward at a certain angle.

It should be pointed out that the bottoms of all pipe sheds should be placed on the curve parallel to the tunnel excavation contour line, so as to ensure that each shed pipe in the pipe shed is uniformly loaded at each stage and to avoid large local displacements.

In different stages of tunnel construction, the force of the advanced support of the pipe shed is different. In the design of the pipe shed, it must be adjusted in time according to the changing characteristics of the force of the pipe shed, and the parallel anchor net and spray support can form an effective primary support structure together with the pipe shed, so as to ensure the construction safety.