Is there any progress in 202 1 Haidian Shanhou Tunnel?

More than a decade ago, the people of China planned to build a 330-kilometer-long Long Da-Ruili railway from Dali, Yunnan Province to Ruili, a border city between China and Myanmar, with a design speed of 140 km/h. This railway is a national first-class electrified railway, with short length and low specifications, and it is not a high-speed rail line. It wouldn't have received much attention. However, what the global engineering community never expected was that a tunnel with hellish difficulty was born on this railway, which once stumped this "infrastructure madman" and more than 500 tunnel experts around the world. This is the Dazhushan Tunnel. Total length 14.484 km. The initial estimated construction period is five years. From 2008 to 2065,438+09, it has not been completed for eleven years. (1) Why is it difficult for the railway to cross the Hengduan Mountains? Hengduan Mountains, located in the southeast of Qinghai-Tibet Plateau, is one of the youngest mountain groups in the world formed by the mutual extrusion of Indian Ocean Plate and Eurasian Plate. Due to plate compression, there are many fault zones, mountain folds are tight and faults are bound. Many large rivers such as Nujiang River, Lancang River and Dadu River develop along deep faults. As long as you look at the map of Hengduan Mountain, you will know that Hengduan Mountain is called "Hengduan" because it consists of a series of parallel slender mountains, which can't be bypassed. If you want to build a road into these places, you must conquer Hengduan Mountain. Dazhushan Tunnel is located in the south-central Hengduan Mountains, on the western edge of Yunnan Plateau, with overlapping peaks, steep slopes and deep valleys, and cliffs everywhere. The site environment where Dazhushan Tunnel is located is not only complicated in terrain. Due to abundant precipitation and developed water system, some surface water will seep into groundwater along bedrock joints and caves. Because the rock stratum in Hengduan Mountain area is very broken, it is easy to be eroded by the seeping groundwater, forming large and small caves and cavities, and there are many underground rivers sneaking along the broken zone in the rock stratum. The surface of Dazhu Mountain looks complete, but it looks like a big water tank inside. It will be very troublesome to encounter these water storage areas during construction, and it is easy to have water seepage and mud collapse. Due to the compression of plate movement, there are a lot of in-situ stresses in the intact rock strata in the mountain. Once the stress stability of these strata is destroyed by construction, it is easy to cause landslides and even earthquakes. In addition, the stratum of Dazhushan is rich in gas, geothermal and even radioactivity. It is a big problem for tunnel builders to take out any of them separately. Therefore, people here have lived in isolation for a long time. In recent years, with the proposal of the China Belt and Road Initiative, the economic ties between southwest China and Southeast Asian countries are getting closer and closer, and it is necessary to repair the railway crossing the Hengduan Mountains. Darrouy Railway connects Kunming, the southwest center of China, with Kyaukphyu, the southwest of Myanmar, and runs in parallel with China-Myanmar oil and gas pipeline, which will greatly promote China-Myanmar economic and trade ties, greatly reduce freight and personnel exchange costs, and radiate to neighboring countries and regions. Therefore, although the railway crossing the Hengduan Mountains is very difficult and the investment is huge, the return is also considerable. In any case, such infrastructure investment is worthwhile. (2) As short as 156m,15 West Lakes spewed out. In the total length of less than15km, the Dazhushan tunnel will cross 6 fault zones, 5 karst development sections and 3 fold structures. Among these problems, a few hundred meters is really difficult, which has extended the construction period by ten years. Yanziwo fault and Shuizhai fault are the two most dangerous faults in Dazhushan tunnel. During the construction, workers drilled holes and blasted on the fault, and a breach with a diameter of 20 cm suddenly appeared on the tunnel face, and debris flows kept pouring out. After the impact of debris flow, the breach became more and more serious. It took only 1 hour to bury a 4-meter-high engineering vehicle, and a few hours later, a tunnel with a length of more than 400 meters was filled. At first, the workers tried to solve the debris flow according to the traditional method, temporarily retreated, and then poured solidifiable slurry into the rock stratum to fill the cracks to stop the debris flow gushing. But this is far from solving the problem of water inrush and mud outburst in Dazhushan tunnel. Every few meters people dig forward, there will be more serious water inflow than before, and the maximum water inflow will reach 6.5438+0.22 million cubic meters per hour, which is equivalent to a river spewing out of the tunnel. In fact, the groundwater level in Dazhushan is located in the range of 200-400 meters above the tunnel vault, which makes the pressure of groundwater in the tunnel as high as 3 MPa. Such a high water pressure can easily penetrate the surrounding rock of the prismatic fault fracture zone, and then rush the 20-ton excavator 40 meters away. Workers braved the flood to stop the leakage, not to mention the fault with high water pressure. Engineers also tried to bypass from the side, but after bypassing 100 meters, it was found that it was not feasible at all. This fault has no boundary at all. As long as you walk from Dazhu Mountain, you must cross this fault. After repeated exploration and failure, the construction team of Dazhushan Tunnel finally found a construction scheme that can resist this fault. People adopt the schemes of high-pressure dynamic water section drainage, ultra-high pressure polymer grouting and pipe shed grouting to block water, and finally successfully pass through the high-pressure water-rich fault section. Engineers found that fault treatment is mainly to solve the problem of water in faults. Only when the water seal of the excavation section of the fault is blocked 6-8 meters away from the excavation contour line, the water pressure is drained, and the cement slurry is injected to assist the fault consolidation, can the safe passage through the fault be ensured. The construction scheme of ultra-high pressure polymer grouting is adopted, which effectively ensures the effective diffusion and consolidation of slurry. This is a special cementing material, its compressive strength can reach 20 MPa, it is not diluted by water, and it can effectively seal the water out of the excavation contour. At the same time, in order to prevent the occurrence of dangerous situations in the tunnel, the project department has also established a five-stage pumping station to pump water 24 hours a day. Tunnel construction workers, in fact, this method is completely a "stupid method". Because of the complex formation conditions and the irregular distribution of karst caves and karst troughs, it often takes 5~8 holes for a karst cave to complete grouting reinforcement. During grouting, pipes must be laid in each hole, and these pipes cannot be reused, which seriously increases the cost. But for Yanziwo fault, a hard-core project, only this slow and steady stupid method can really be solved, leaving no future trouble. From 2009 to 20 1 1, 156 meters, the Yanziwo fault was dug for 26 months before it was finally dug through. Waterfalls and Yanziwo faults gushing from Dazhushan Tunnel are just a microcosm of the problems in Dazhushan Tunnel. Eleven years after the construction of Dazhushan Tunnel, all the optical pumps were used up 1 16. Even the engineers themselves don't know whether it is a high mountain or an underground river. The water gushing from the tunnel even formed a waterfall, which has flowed here for more than nine years. People who don't know even think that this is a natural landscape that has existed since ancient times. (3) The temperature in the tunnel is as high as 40 degrees Celsius. How to overcome it during construction? Dazhushan Tunnel is rich in geothermal resources. When the mechanical equipment works intensively, the emitted heat makes the ambient temperature in the tunnel as high as 40 degrees Celsius. High temperature and gushing water form a natural sauna, and the humidity is as high as 80% all the year round. Generally speaking, the temperature in the tunnel is above 28 degrees Celsius, and the environment of 40 degrees Celsius obviously has a great impact on the health of workers. In order to reduce the temperature in the cave, the construction team buys a lot of ice cubes from Baoshan every day to reduce the temperature in the cave and ensure the safety and health of the construction workers. Three construction faces need to consume 3 tons of ice every day, but even so, the cooling effect is still not satisfactory. The construction team finally adopted DV400 refrigerator specially designed for tunnel cooling, which effectively cooled the working environment of tunnel face. The principle of DV400 refrigerator is that under working condition, the liquid refrigerant in the compressor is pressed into the spiral coil of the direct evaporator, which expands rapidly and becomes gaseous refrigerant. When the refrigerant vaporizes, it absorbs a lot of heat from the air flow outside the evaporator coil, so that the temperature of the air flow inside the evaporator drops sharply, and then a lot of moisture in the air flow is removed through the condensation of the evaporator, thus achieving the effect of cooling and dehumidification. By this method, the air on the tunnel face can be continuously cooled, and the temperature of 4 1 degree Celsius can be reduced to 32 degrees Celsius. Conclusion: Now, the construction of Dazhushan Tunnel has entered the last fault, and it is still one kilometer short. This once insurmountable myth project will run through. When the Darrouy Railway was opened to traffic in 20021year, it only took seven minutes for the train to pass through the Dazhushan Tunnel, which had been built for thirteen years. The construction workers in Dazhushan exchanged their thirteen years for seven minutes of thousands of passengers in Qian Qian. As the most recognized label in the world, China Manufacturing is seeking strategic upgrade. "Made in Great China" column invites industry authorities and experienced players to express their views on China's road to innovation.