Abstract

Tunnel roof support pipes play a crucial role in maintaining the stability and safety of tunnel structures. This paper delves into the characteristics, installation methods, and effectiveness of different types of tunnel roof support pipes in preventing tunnel collapse and other disasters. Furthermore, it explains how the two work together, in conjunction with the application of sonic logging pipes in tunnel engineering, to provide strong and reliable support and monitoring in complex underground environments, ensuring the safe and smooth progress of tunnel construction and operation.

I. Introduction

With the continuous advancement of infrastructure construction in transportation, energy, and other fields, tunnel projects are increasingly common. Whether it's railway tunnels, highway tunnels traversing mountains, or tunnels used for subways, utility tunnels, and other functions in urban areas, their safety and stability are paramount. Tunnel roof support pipes, as key components ensuring the safety of tunnel structures, can withstand the pressure of the soil or rock above the tunnel, preventing deformation and collapse of the tunnel roof and providing a safe space for personnel and equipment inside the tunnel. Sonic logging pipes, on the other hand, are mainly used in tunnel engineering for quality inspection of the surrounding rock and support structure. The two complement each other, working together to safeguard tunnel safety.

 II. Types and Characteristics of Tunnel Roof Support Pipes

(I) Metal Support Pipes

Common metal tunnel roof support pipes include steel pipes and shaped steel pipes. Steel pipe support pipes possess high strength and rigidity, capable of withstanding significant pressure. They can be custom-made according to tunnel design requirements, with adjustable parameters such as length and diameter. In tunnel projects with complex geological conditions and high surrounding rock pressure, steel pipe support pipes can effectively resist roof deformation, providing stable support for the tunnel. For example, in the construction of a highway tunnel crossing a fault zone, large-diameter steel pipes were used as roof support pipes. Through reasonable arrangement and connection, a strong support system was formed, successfully addressing the instability of the surrounding rock in the fault zone.

Shaped steel support pipes, such as I-beams and H-beams, have reasonable cross-sectional shapes and good mechanical properties. I-beam support pipes are widely used in tunnel roof support; their wide flanges and thin webs better disperse the pressure transmitted from the roof. In the construction of a subway tunnel in a certain city, due to the dense buildings above the tunnel and strict requirements for ground settlement, a support method combining I-beam support pipes and shotcrete was adopted. This effectively controlled the deformation of the tunnel roof, ensuring construction safety and the stability of the ground structures.

(II) Composite Material Support Pipes

Composite material support pipes are usually composed of two or more materials, combining the advantages of different materials. For example, fiberglass composite support pipes are lightweight, corrosion-resistant, and have high strength. In some tunnel projects with high corrosion resistance requirements, such as tunnels in coastal areas or tunnels with corrosive underground media, fiberglass composite support pipes can work stably for a long time, reducing the risk of support failure due to corrosion. In addition, there is a carbon fiber reinforced composite material support pipe, which has extremely high strength and good toughness, and can withstand large pressure while adapting to a certain degree of deformation, providing reliable support for the tunnel.

(III) Telescopic Support Pipes

Telescopic support pipes are a uniquely designed support pipe that can automatically adjust according to the deformation of the tunnel roof. These support pipes usually consist of inner and outer parts, and their telescopic function is achieved through hydraulic or mechanical devices. During tunnel construction, as the surrounding rock releases stress and deforms, the telescopic support pipe can adjust its length in a timely manner, maintaining close contact with the roof slab and providing continuous and effective support. For example, in the construction of a long tunnel, telescopic support pipes were used. In the initial stage of tunnel excavation, the support pipes were in a contracted state, facilitating installation and construction; as the tunnel advanced and the surrounding rock deformed, the support pipes gradually extended, tightly fitting the roof slab and effectively preventing roof collapse.

III. Installation Method of Tunnel Roof Support Pipes

(I) Measurement and Positioning

Accurate measurement and positioning are crucial before installing the tunnel roof support pipes. Construction personnel need to use professional surveying instruments, such as total stations and levels, to determine the installation position and spacing of the support pipes according to the tunnel design drawings and construction requirements. During the measurement process, factors such as the tunnel's geological conditions and the deformation characteristics of the surrounding rock must be fully considered to ensure that the support pipes can evenly bear the pressure from the roof slab. For example, during the construction of a railway tunnel, surveyors determined the appropriate spacing of support pipes in different sections through detailed investigation and analysis of the surrounding rock, providing an accurate basis for subsequent installation work.

(II) Drilling and Installation

Based on the surveying and positioning results, drilling equipment is used to drill holes in the tunnel roof for installing the support pipes. The diameter and depth of the holes must be determined according to the specifications of the support pipes and geological conditions to ensure that the support pipes can be firmly installed in the holes. When installing the support pipes, attention must be paid to their direction and verticality to ensure they can accurately withstand the pressure from the roof. For metal support pipes, welding or bolting connections are usually used for fixing; for composite support pipes, special connection methods, such as clamp connections, may be required. For example, in the construction of an underground utility tunnel in a city, fiberglass composite support pipes were used. Construction workers used special clamps to fix the support pipes in the holes in the roof, ensuring the stability and reliability of the support pipes.

(III) Reinforcement and Connection

To enhance the overall stability of the support pipes in the tunnel roof, reinforcement and connection of the support pipes are also necessary. Common reinforcement methods include spraying concrete around the support pipes and installing steel arches. Shotcrete can tightly bond the support pipes to the surrounding rock, forming an integral support structure and improving the load-bearing capacity of the support pipes. Steel arches can cooperate with the support pipes to jointly bear the pressure of the roof slab, enhancing the stability of the tunnel. Regarding connections, for support systems composed of multiple support pipes, reliable connection methods are required, such as welding, bolting, or lap joints, to ensure the support system can work collaboratively. For example, in the construction of a long tunnel, a support method combining steel pipe support pipes and steel arches was adopted. The steel pipes and steel arches were connected together by welding, forming a strong support network that effectively ensured the construction safety of the tunnel.

IV. Application of Sonic Logging Pipes in Tunnel Engineering and Their Synergistic Effect with Roof Support Pipes

(I) Working Principle of Sonic Logging Pipes

Sonic logging pipes are non-destructive testing equipment used to detect internal defects in concrete structures. In tunnel engineering, sonic logging pipes are typically embedded in the surrounding rock or support structure of the tunnel. By emitting acoustic signals into the pipes and receiving the reflected signals, the internal quality of the tunnel structure is analyzed based on parameters such as signal propagation time, amplitude, and frequency. Sonic logging pipes can detect defects such as cracks and cavities in the surrounding rock, as well as whether the thickness and strength of the support structure meet design requirements.

(II) Collaborative Work of Sonic Logging Pipes and Roof Support Pipes

During tunnel construction, sonic logging pipes and roof support pipes can work together, providing dual protection for tunnel safety. On one hand, sonic logging pipes can monitor the quality of the tunnel roof and surrounding rock in real time, promptly identifying potential safety hazards. If the sonic logging pipes detect cracks in the tunnel roof or unstable factors in the surrounding rock, construction personnel can promptly adjust the installation parameters of the roof support pipes or take reinforcement measures to prevent accidents. On the other hand, the roof support pipes provide a stable environment for the installation and normal operation of the sonic logging pipes. When installing sonic logging pipes, they need to be fixed to a stable structure. The roof support pipe provides reliable support for the sonic logging pipes, ensuring they are not damaged during tunnel construction and can accurately acquire detection data. For example, in the construction of a subway tunnel, both roof support pipes and sonic logging pipes were used. During construction, the sonic logging pipes detected minor cracks in a localized area of the tunnel roof. Construction workers immediately inspected and reinforced the corresponding roof support pipes, promptly eliminating the safety hazard and ensuring the safety of tunnel construction.

V. Conclusion

Tunnel roof support pipes play an indispensable role in ensuring tunnel stability and safety. Different types of roof support pipes have their own characteristics and applicable scope. Construction personnel should select the appropriate type of support pipe and adopt the correct installation method based on factors such as the tunnel's geological conditions and construction requirements. Sonic logging pipes, as important detection equipment in tunnel engineering, can work in conjunction with roof support pipes to provide real-time monitoring and assurance for tunnel safety. In actual engineering, the organic combination of the two can effectively cope with various complex geological conditions and construction challenges, ensuring the safe and smooth progress of tunnel construction and operation. In the future, with continuous technological advancements, tunnel roof support pipe and sonic logging pipe technologies will continue to improve and develop, providing more reliable technical support for tunnel engineering construction.