The Zhaotong Tunnel, which is under construction, is a key control project of the Chongqing-Kunming high-speed railway, and is also a first-class high-risk tunnel. During the National Day holiday, more than 300 construction personnel of Zhaotong Tunnel stuck to their posts to step up construction, stretching under the majestic Wumeng Mountain, a special competition is continuing.
A series of standardized treatment processes, such as rapid evacuation of personnel, increasing tunnel ventilation, and reducing gas concentration, are the experience summed up by tunnel builders in previous similar emergencies, coupled with the help of advanced equipment, and can remotely control the monitoring, ventilation and other equipment in the tunnel in the duty room. After about ten minutes, the gas concentration at the alarm point has dropped to a safe value, and Zhou Jian needs to go to the construction face for on-site inspection. After receiving permission, the reporter also wore the relevant equipment according to the standard and went to the tunnel together.
The Zhaotong Tunnel is 16.2 kilometers long, passing through a variety of strata in the Wumeng Mountains and 4.2 kilometers of coal seams at the same time, resulting in the gas outburst index in the construction area, which is much higher than the standard value, which is the first time encountered in the construction of domestic tunnels, and there is no experience that can be used for reference. After on-site investigation and analysis by a number of scientific research teams, the construction plan of using negative pressure vacuum to extract coal seam gas, reducing the gas concentration and pressure in the coal seam to below the outburst standard, and then continuing to excavate. At the same time, with the increasing experience of mainland tunnel construction, many new tooling processes have been adopted in the construction process, but emergencies like this occasionally occur.
In addition to the problem of high gas in the coal seam, the construction personnel also have to deal with the difficulties and even dangers caused by high geostress and high-pressure karst water at all times.
This is a video recording, occurred on May 6, 2022 a slip collapse danger, after the construction personnel found the abnormal situation, immediately commanded the personnel and equipment to evacuate, in just 3 minutes, the poured slag accompanied by muddy water completely buried a transport vehicle that had not had time to evacuate. On June 23, 2023, this happened again.
Dangerous situations such as slipping and slumping, mud and water gushing have occurred more than 20 times in different construction sections since the start of construction. However, the construction unit took advanced geological early warning measures and strengthened the construction personnel's awareness of prevention, but no casualties were caused.
In the other working face of the tunnel, the workers currently need to work in such an environment at any time, from this water-rich section, the construction unit is equipped with a modern rock drilling trolley, which can work together with manpower and mechanical equipment to reduce the number of personnel and improve construction efficiency. However, processes such as filling explosives still need to be completed manually against the gushing water.
Although wearing waterproof clothing, the reporter was already soaked in less than a minute at the scene, and the workers had to insist on two or three hours to complete the process. After detection, there are many strong water-rich areas in this construction section, which is also extremely rare in the process of domestic tunnel construction.
The construction of the Zhaotong Tunnel started in December 2019, and at present, the excavation of the main tunnel has exceeded 9 kilometers.
Text/Reporter Liu Wenjie Li Jinsong
(CCTV News Client)
Editor/Dynasty