The pipe roofing method was first applied in the design and construction of the Venice underground station tunnel on the Milan railway link in Italy in the 1980s. At the end of the 1970s, Italy companies developed mechanical equipment that can safely carry out full-section excavation in weak formations and improve its production efficiency. It can maintain the stability of all tunnel vaults and working faces excavated in advance in a long distance. In this process, the pipe roofing method came into being. Because of its good support effect, it has been widely used in tunnel projects in Japan, the United States, and Europe. It solves the difficulties brought by many unfavorable factors to the project, including the super long section of the tunnel; the shallow burial of the tunnel; the existence of the foundation of multi-story buildings; the unconsolidated ground; the existence of groundwater, etc.;

 

The construction principle of the pipe roofing method is closely related to the principle of the NATM, short for NewAustrian TunnellingMethod. NATM was proposed by Miller and Rabschwitz as a new construction method closely related to shotcrete anchor support. Since the 1980s, with the continuous improvement of related technologies and the deepening of the understanding of the NewAustrian TunnellingMethod, some people classify the construction of the pipe roofing method as a kind of expansion of the application scope of NATM.

 

Since the 1980s, in Japan, pipe roofing support has been used in many tunnel openings located under national highways to control ground settlement within the allowable range and successfully ensured the operation of highways. The first pipe roof construction project in the United States is a crossing tunnel project under the Oak Street Expressway in Corona by California VALLEY Engineering Company, using a pipe roof with an outer diameter of 200mm. The Washington Tunnel in the capital of the United States, under the condition that there was no surface passage, used horizontal directional drilling technology to carry out the world's longest large pipe roof advance pre-support for the soil layer around the tunnel. In 1996, South Korea's Incheon Metro adopted the largest pipe roof support structure in Korea with an outer diameter of 815mm and a wall thickness of 16mm near the Pu Pyung exit of the Seoul-Incheon Highway to pass the expressway.

 

With the development of tunnel support technology, new breakthroughs have been made in the pipe roof support technique. At present, as a new method for pipe shed support, the self-drilling pipe roof can replace the conventional pipe roof for the bottom of various easy-to-collapse holes, effectively reducing surface settlement and preventing surrounding rock collapse. The self-drilling pipe roof combines a hollow anchor bar, drill bit.  For urban construction, the development of new technologies can continuously improve engineering safety and construction efficiency, and also provide more possibilities for urban infrastructure.

 

 

Categories

Underground Structures

Keywords

tunnel construction