The three-and-a-half years of the Chengdu-Chongqing Passenger Specialized New Longquanshan Tunnel was completed on April 30, laying a solid foundation for the opening of the entire railway network in 2015. The Chengdu-Chongqing two-land one-hour economic circle is just around the corner. At the same time, as an important part of the Shanghai-Chengdu rapid passenger transportation route, Chengdu-Chongqing Passenger Specialization will also become an important high-speed rail transit channel for Sichuan.

Fight "high gas"

The length of the new Longquanshan Tunnel is 7.3 kilometers, which is the most important control project on the whole line, and it is also the longest high-speed railway double-track tunnel in Sichuan Province. The tunnel straddles the Longquanshan fault and its geology is quite complex. Grade IV surrounding rock is 4.7 kilometers and Grade V surrounding rock is 1.1 kilometers. The tunnel passes through shallow natural gas, fault crushing sections, joints and fissures dense belts and other undesirable geological sections, of which the high gas section is close to 2.7 kilometers. No. 1 inclined well has a slope of 38.2%, and No. 2 inclined well has a slope of 37.9%. It is also rare in domestic tunnels of the same type. During the excavation process, there were problems such as water inrush and mud outburst, and back slope drainage. The maximum amount of water flowing in the face per unit time was 2.2 cubic meters per minute. Because of the poor geological conditions, the New Longquanshan Tunnel has been assessed by the China National Railway Corporation as a very high-risk high-gas tunnel, and it is the hardest part of the Chengdu-Shantou special railway line.

In September 2010, the project department was established to work hard to optimize the construction organization design program, strengthen construction management, vigorously promote the regularization of safety education, implement the responsibility of the system, standardize the on-site construction, refine the construction management, and monitor and measure informationization. The safety of high gas tunnel construction is of the highest priority. The project department has established and strictly implemented the pre-paid safety training system, advanced geological forecasting system, gas monitoring system, surrounding rock measurement system, etc., to do a good job in tunnel ventilation and improve the emergency plan system. To ensure the safety of construction is foolproof. At the same time, it is required to strictly implement the process real-name system, three-member shift system, closed management system, and real-name system in and out of the hole, and actively use new equipment such as Nomte jet manipulators and Yangjiao moving mold frame to apply wet new shotcrete new technology to ensure construction. Quality, safety and progress.

In October 2010, the tunnel was officially started. In the initial stage of construction, due to complicated geological conditions such as loose geological, high gas, high-risk rock, large span, large deformation, shallow depth, etc., the construction was once trapped, especially in the fault fracture zone with the worst geological conditions of nearly 80 meters. After that, the project department continued to produce distortions. The project department organized experts and design units to conduct research on the construction plan and proposed the “three-step, seven-step excavation” method in accordance with the principle of “short excavation, strong support, and early closure”. Pass through complex geological segments quickly and safely. In the process of importation, the CRD method, the method of increasing the arch feet, the reinforcement of the lateral pipe sheds, and the filling of the surface grouting were used to handle and try, and various reinforcement measures were adopted to finally stabilize the surrounding rock.

The gas in the new Longquanshan tunnel is embedded in the crevices of the rock. During the construction, gas accumulates in the tunnel. If the gas concentration exceeds a certain threshold, it will cause burning, explosion or suffocation. The consequences are disastrous. To ensure safety, the project department commissioned professional organizations to take charge of the gas prevention and control technology during construction and formed a gas detection system consisting of a gas monitoring system, full-time inspector inspection, management personnel, and other special types of workers. At the same time, the whole tunnel is divided into four areas. Each area is equipped with a gas monitoring system, equipped with the functions of “wind power blocking and tile blocking”, and the alarm, power off, and recharge threshold gas concentrations of the gas monitoring system are set according to the specifications. Three gas monitoring workers are assigned to each hole and three shifts are carried out to implement a 24-hour on-duty maintenance system.

Wang Yinzhi, executive deputy manager of the project department, said that before entering the tunnel, construction workers must pass through security doors to ensure that there are no lighters, mobile phones or other electronic equipment to eliminate all sources of fire; people entering the tunnel must not wear chemical fiber clothing, because chemical fiber clothing is susceptible to friction. Static electricity is generated and static electricity may cause a gas explosion.

Slag rail transport

As it is a gas tunnel, the slope is too large and the space is small. It is impossible to use conventional trackless transport. The transportation of nearly 400,000 cubic meters of waste slag and nearly 110,000 cubic meters of concrete becomes a headache. The project department brainstormed and held a number of seminars. It finally decided to introduce mining elevators for rail transportation and solved the problem that large-angle inclined shaft gas tunnels could not be tracklessly transported.

After entering the Zhengdong and Pinggui construction, the slag and feed must undergo two conversions and three shipments. Taking slag as an example, we must first transport the slag at the face of the shovel to the bottom of the inclined well through the shuttle truck, load the slag and then load it into the side-turner, and then transport it to the wellhead of the inclined well to automatically slag through rail transportation. Finally, it was sent to the waste disposal site by trackless transport. In order to improve ergonomics and reduce costs, the project department has focused on the integration of processes. A bottom-dumping and slagging platform has been set at the bottom of No. 1 inclined shaft to improve the ability to store slag, reasonably arrange rail transport tracks, rationally configure the number of mine cars, and shorten process cycles. Time, speed up construction progress. At the same time, a special person is required to check, repair and maintain the winch system and the transportation track every day. Problems should be solved in time to ensure that the equipment performance, gauge, line type, turnout, sleeper, and connection position are normal. During each cycle of operation, after the completion of the excavation, the professional track-laying personnel shall also promptly take over the long rails and move the inverted arch trestle bridges to open the transport corridors with fast quality and quantity.

Innovative grid steel processing

During the processing of the grille steel frame, there was no technical equipment for the original machine-made equipment because there was no equipment for processing the four-leg grill steel frame at the time. Most of the construction units have followed the traditional processing methods and can only produce the “eight” type ribs. According to the requirements of the design drawings, the "8" ribs are produced, which not only results in the waste of welding consumables, but also fails to meet the design requirements of drawings. To this end, the project department formed a technical research team to begin the difficult research work, access to data, computer search, consult processing problems to the frontline workers, hold weekly technical meetings for exchanges and summaries, on-site processing experiments ... Finally, fully consider the three-dimensional After the bending, change the size, according to the design of "8" rib size cutting, and then use the bending machine according to the size of a "clip" shape, and then use the self-made plane hydraulic processing equipment processing "clip" into "8" shape, and according to design The welding is required, and the vertical “8”-shaped rib structure is vertically extruded by vertical hydraulic processing equipment and welded to the main ribs in the mold according to the design requirements. The manufacturing method of this processing method is simple in operation, not only improving the processing speed, but also making the processing quality easier to control. At the same time of conserving the welding consumables, the integrity of the steel frame is better than that of the original, and the strength is higher. This innovation has obtained the national patent.

During the construction of the new Longquanshan tunnel, the project department has established a number of on-site scientific and technological research teams, respectively, optimizing the slag dredging platform at the entrance, the safety of cross-track transportation at large angles, the adjustment of the ventilation scheme, and the construction of the inverted arch concrete for the inverted arches. Cantilever crane hoisting operations and other scientific and technological research, not only solve practical problems, improve production efficiency, but also improve the project management personnel's sense of innovation and technical level.