Excavation of the 10-meter tunnel for Yumo Railway breaks through the 10km mark-detection of tunnel lining void

Entrance to the Ma Li Zhai Tunnel

 

The Yumo Railway is an important part of the China-Laos International Railway. It is an important project in the national “Belt and Road” strategy. It is also the largest infrastructure project under construction in Yunnan Province. Building the Yumo Railway has a glorious mission and great responsibility. The company undertook the construction of the first 10 bidding sections of Yumo Railway Station, which is located in Ning'er County, Pu'er City, Yunnan Province. The main line of the section is 22.405 kilometers long. The main projects include 4 tunnels, 4 bridges, 1 station yard and 30.6 km ballastless track bed The tunnel accounted for 92.6%. The most difficult and difficult project is the Dajinshan Tunnel with a total length of 10657 meters, and the controlled project is the exit section of the Shitouzhai Tunnel with 4851 meters.

Dajinshan Tunnel Exit

 

Due to the large changes in the topography and geomorphology in South Yunnan, the geological conditions are extremely complicated, and there are many types of unfavorable geology. The line runs through subtropical rain forests and minority residential areas, and construction faces many challenges. Since the start of construction in May 2016, the project department has adhered to high standards and strict requirements, and further promoted the standardization of railway construction. , Many high-risk tunnels, difficult material support, poor climate and many other difficulties.

 

In the course of construction, of course, it is necessary to consider the problems that occur during the later use of the tunnel. Generally, as the service life of the tunnel increases, the tunnel lining will also age. The main aging phenomena that occur are:

 

① peeling and falling off;

 

② crack;

 

③ hollow inside;

 

④ Concrete strength decreases;

Among them, ① and ② will directly pose a threat to train operation. On June 27, 1999, a tunnel on the Sanyo Shinkansen (Osaka-Fukuoka) in Fukuoka prefecture had a 200 kg of concrete on the side wall hit a high-speed train. The analysis showed that the concrete was peeling (Peeling) may be caused by cold shrinkage. Therefore, the problem of peeling and peeling of tunnel lining has attracted widespread attention, and how to detect it quickly and effectively has become an important issue.

     At present, the main method for detecting internal defects of tunnel lining is radar method. This method has a good detection effect on the voiding behind the lining, and has been widely used. However, in addition to price reasons, this method also has the following problems:

① Not sensitive to cracks and the resulting peeling and peeling;

② Cannot reflect the material of concrete;

 

Based on the above problems, our company has been committed to the research and development of non-destructive testing systems for civil engineering, and has developed a series of non-destructive testing equipment and systems for concrete, filling engineering, prestressed engineering, and piles and columns. These devices are based on shock and elastic waves, forming a relatively complete technical system.

 

Here are two solutions to their problems

 

Thickness detection method and principle The spectrum signal analysis method can be used to calculate the moment (ie period) of the reflected signal on the side of the structure, and the thickness of the object can be measured based on this and the wave velocity.

Figure 4-2 Conceptual diagram of the vacuum test

 

The detection method and principle of voiding continuously excite the elastic wave signal along the surface of the test object, and the signal will reflect when it encounters a loose medium such as a cavity or a voiding surface. By extracting the reflected signal and performing corresponding spectrum and image processing, the presence or absence of the void and the depth position can be identified.

Mohei Fourth Line Bridge under construction

 

Up to now, the project department has completed the construction of 3314 meters of the four auxiliary tunnels of the Dajinshan Tunnel and the Shitouzhai Tunnel, the large-mileage exit of the horizontal tunnel of the Shitouzhai Tunnel, the completion of the substructure of the Mohei Fourth Line Bridge and the Xiubai Double Line Bridge. The mountain tunnel has been completely completed, and the continuous beam of the 4x32m turnout of the Mohei Fourth Line Bridge has been successfully poured. A number of important nodes and breakthroughs have been made, and construction production is being accelerated.