All About Tunnel Pipe Umbrella Technology Are Here

Before excavating the tunnel, drill a row of slightly upwardly sloping holes on the top of the tunnel face, insert the corresponding supporting materials, and then grout to reinforce the surrounding rock of the tunnel, so that the top of the tunnel can be formed with a certain pressure before excavation. This is called the tunnel pipe umbrella system, and tunnel excavation under the support of this system can be safer and more efficient.

pipe umbrella system

Applicable Geological Conditions of Tunnel Pipe Umbrella Technology

The tunnel pipe umbrella advanced support technology is applied to unfavorable geology, mainly refers to the areas of loose rock mass, weak and broken, expansion, karst, water, eccentric pressure, high ground stress, etc. The excavation and construction of such stratum caverns have great hidden dangers, so they must be supported in advance to ensure the possibility of later construction.

Materials Types of Tunnel Pipe Umbrella System

Advanced Small Catheter

The advanced small catheter is generally made of seamless steel pipe with a diameter of 38~50mm.

The advanced small duct is a basic type of advanced support for the pipe umbrella. It is a method of short-distance advanced pre-support. It is generally suitable for the formation where the face can be stabilized in a short time or the self-stabilizing ability of the surrounding rock is very low and there is little water. The exposed ends are often supported on the steel frame behind the excavation face to form a pre-support system together.

Long Tube Shed

Long tube sheds generally use seamless steel pipes with a diameter of 80-180mm and a wall thickness of 4-8mm.

The long tube shed is another basic type of advanced pre-support in the tunnel support. Compared with the small conduit grouting method, it is a long-distance advanced pre-support method. Due to the long advance distance and high rigidity, it is suitable for Self-stabilizing and water-bearing strata often form a pre-support system together with a steel frame, which has a better effect of controlling surface subsidence, better anti-seepage and water-stopping effect, higher construction technology requirements, and higher cost.

Self-Drilling Hollow Bolt

Self-drilling hollow bolt consists of a hollow bolt, connector, nut, drill bit, plate, and centralizer. It can combine drilling, grouting, and anchoring in one process. Self-drilling hollow bolts are safe, efficient, and convenient. Ideal for broken rocks, loose soils, and difficult-to-drill geology. It helps to ensure the anchoring effect under complex stratum conditions and achieve the best construction effect.

self drilling rock bolt system

Used in the pipe umbrella system, the self-drilling rock bolt has many advantages.

It combines drilling, grouting, and anchoring together, and is suitable for broken rock and conditions which are difficult to drill holes. Casing pipe is omitted in construction, which greatly improves construction efficiency.

The self-drilling rock bolt has a rich variety of drill bits, and the drill bit can be selected according to the properties of rock and soil, which can improve the drilling efficiency.

It can fill cracks, consolidate rock mass and soil layer through pressure grouting, and has good grouting spreading radius and reliable anchoring quality.

The hollow anchor bar can be cut arbitrarily and lengthened by the coupler. Therefore, the self-drilling anchor bolt is suitable for construction in a narrow space that large equipment cannot enter.

Application Scenarios of Tunnel Pipe Umbrella

As an auxiliary method of tunnel construction, the pipe umbrella system has been rapidly developed in the construction of tunnels and underground structures. According to the existing construction cases, the pipe umbrella system is mainly used on the following occasions:

pipe umbrella in tunnel

As a protection for tunnel construction under existing roads and railways;

As a protection for tunnels built in the ground and under important building structures on the ground;

As an auxiliary support method for large-section tunnel construction;

As an auxiliary method for the construction of the tunnel entrance section;

As an auxiliary method for breaking through a river bottom, seabed, fault fracture zone, collapsing surrounding rock, etc.;

Instead of construction beams or retaining plugs, it is used as an auxiliary method for other construction.

Conclusion and Analysis

If the tunnel is excavated with pipe umbrella support, it will be able to effectively control the settlement of the vault. Compared with the support without the pipe umbrella, the settlement of the tunnel vault is reduced by 77%, and the settlement of the tunnel vault with the pipe umbrella has a tendency to converge; During the support, the uplift value of the arch bottom is greatly reduced, which is 22%, indicating that the pipe umbrella in tunnel support can effectively control the deformation of the surrounding rock.

At present, the advanced pipe umbrella system technology has been widely used in underground projects such as highway tunnels, railway tunnels, urban subways, and underground passages as an auxiliary stabilization method for tunnel construction. The transportation and installation are flexible and convenient, so its use in mountain tunnels is more advantageous.

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