Tianjin Railway Station Transportation Hub Project Initiates "Zero Transfer" Era
The transportation hub project of Tianjin Railway Station, which is listed as one of the 20 popular projects in Tianjin, highlights the service concept of "zero transfer" in its design scheme. What is zero transfer? How to make a zero turn? Simply put, the transfer between the Beijing-Tianjin intercity express railway and the city subway, as well as the transfer between subway lines 2, 3 and 9, can be completed without leaving the station, which is convenient for passengers to travel to the maximum extent. The Beijing-Tianjin intercity express railway will connect the ground floor and underground floor of the transportation hub of Tianjin Railway Station.
The transportation hub project of Tianjin Railway Station is a large-scale comprehensive project integrating ordinary-speed railway, Beijing-Tianjin intercity railway, urban rail transit, public transportation and surrounding municipal roads. This project takes the front and rear squares of tianjin railway station Railway as the core, with Ligonglou overpass in the east, Wujing Road in the west, Haihe River in the south and Xinkai Road in the north. How on earth did this huge project proceed? Here, we will walk into the first bid section of Tianjin Railway Station Transportation Hub Project and take you on a tour of the "underground wonders" created by Tianjin Sanjian.
The construction site of the first bid section of Tianjin Railway Station Transportation Hub Project is very lively. The construction trucks are constantly transporting engineering soil, but there are few construction workers on the ground. Originally, most workers worked underground, which was obviously different from our common construction sites. This is the result of the "cover-and-dig top-down method" adopted in Tianjin Third Construction Project.
When it comes to engineering projects, it is inevitable to use technical terms. The so-called "cover-and-dig reverse method" is not difficult to understand literally, which runs counter to the traditional construction method. The traditional construction method is to lay a good foundation first, and then build a building step by step. The first bid section of Tianjin Railway Station Transportation Hub Project is the central hub, just like a common "wiring board" in a family. Many rail projects have to move closer to the central hub and finally successfully connect the "wiring board". In order to ensure the smooth implementation of the above-ground intercity railway station building project, the central hub can only adopt the "cover-and-dig top-down method" with complex technology and high safety.
Minister Liu of Tianjin Sanjian Production Planning Department told the reporter that the underground part of the central hub is divided into three floors, one floor is 7 meters high, mainly the underground entrance hall of intercity railway, the second floor is 6.5 meters high, mainly the interchange station between intercity railway and subway or light rail, and the third floor is 6.7 meters high, mainly the interchange station of subway and light rail. Among them, there are three floors underground and four floors locally, which is convenient for docking with other blocks. It is understood that the total construction area of these three floors is 70,000 square meters, and the estimated unearthed amount is 550,000 cubic meters. If converted into 10 ton freight cars, it is conservatively estimated that100000 trains are needed.
Zhao Zong engineer of this project said that the calculation of underground engineering is very rigorous, with the top thickness of 1m, the top thickness of the middle two floors of 0.6m, and the bottom thickness of 1.8m-2.8m, forming a relatively sealed "box" surrounded by a continuous underground continuous wall, which is mainly used to prevent water and collapse and ensure the safety of the project and workers. There are 277 cast-in-place piles in this project, each with a depth of 75 meters, of which 24 meters near the ground is a steel pipe column. Modern mechanical equipment digs underground and then transports the soil out through five excavations. At present, the first basement has begun to take shape, and the second basement is being dug.
Basement 1: the most important underground continuous wall building
The basement level, where we are standing now, is about 10 meters underground.
In the face of such a huge underground project, it is no exaggeration to describe it as "underground wonders". In the spacious hall, the workers are busy, some are combing the lines extending to the second floor underground, some are dismantling the formwork of the lining wall, and some are dismantling the metal casing on the outer layer of the cast-in-place pile.
Let's start with the diaphragm wall. If the whole project is regarded as an underground building, the diaphragm wall can not only prevent groundwater leakage, but also prevent the project from collapsing. There are 750 diaphragm walls in the first bid section of Tianjin Railway Station Transportation Hub Project, each with a depth of 48m, a width of 4m and a thickness of1.2m, which is the best diaphragm wall construction in this city. According to Qi engineer at the construction site, the geological environment in Tianjin has brought great difficulties to the construction of underground continuous wall, which is prone to collapse when it is grooved. Therefore, in the construction, in addition to extra care, we must take some new technical measures, otherwise it will be difficult to ensure the construction quality.
Next, let's look at the "pillars" in the construction site. These pillars have different functions in the project. The thickest piles on the site are 277 piles (48 of which are temporary piles). These 2.2-meter-diameter piles are the support columns of "underground wonders" and are responsible for supporting the whole "box". The buried depth of cast-in-place pile is 75 meters, which is divided into two parts. The lower part is a 5 1 m reinforced concrete pile, and the upper part is a 24-meter steel pipe column. Only the lower "reinforcing cage" weighs 19 tons, and the grouted piles are all huge.
In addition to those cast-in-place piles, there are 65 iron pipes with smaller diameters standing in the construction site. These iron pipes are actually vital "pumping wells". With the deepening of the project, there will be more and more underground water. Once a piping accident occurs, it will not only cause the collapse of the project, but also cause casualties. Engineer Qi told reporters that from the whole country to the whole world, many underground engineering accidents are related to groundwater piping, and these 65 pumping wells are undoubtedly the "life guarantee" of the central hub project.
Reverse thinking, "cover-and-dig reverse method" can ensure that the top and bottom are flat, but it is difficult to ensure that the top and bottom are equally flat. However, we were surprised to find that the top and bottom of the basement were very flat. It turned out that in order to ensure the flatness under the roof, the technicians of Tianjin No.3 Construction Co., Ltd. specially "invited tenders" from several floor factories, and used the composite floor that did not deform after soaking in water as a template to ensure that the concrete on the roof was as flat as the floor. The success of this test has solved the leveling problem of the three-story underground roof.
It is worth noting that this huge project is completed underground, and the workers' bodies will naturally feel overwhelmed. To this end, the person in charge of the company specially placed a large number of drinking water equipment and ventilation equipment on the construction site to ensure that workers can work in a more comfortable environment and will not feel suffocated underground.
Finally, let's look at a very interesting device. Many cast-in-place piles are tied with wires at the top. Don't underestimate these wires, they are the "key" of the project. The technician has an instrument in his hand. No matter which wire is connected to the cast-in-place pile, the instrument can display the vertical and horizontal data timely and accurately.
The second floor underground: the gantry grab can do a lot.
Following the spiral staircase, we arrived at the second underground floor under construction. Because the soil has not been dug to the specified depth, our station is about 15 meters underground.
When people go to the second floor underground, they will feel very breathless immediately. The temperature will suddenly rise by five or six degrees Celsius, and the air humidity will reach about 70%. In the dark environment, heavy moisture will come to their faces, and I don't know whether it is sweat or water droplets that condense on them. The wall clearly reflects the stratification of the soil, and the soil at the foot is wet and soft, so you can catch water by hand.
Several excavators are working in turn, stacking the excavated soil at the excavation mouth, and soon a gantry crane excavator will come to work, which can catch about 2 cubic meters of soil at a time. Minister Liu of Tianjin Sanjian Production Planning Department said that there are five gantry grab cranes in the construction site, all of which are "patented products" developed by Tianjin Sanjian itself, and they have made great contributions to the project neutrality. Not only that, they also developed more than 70 light cranes with rotating arms, specially designed for those 277 cast-in-place piles. It turns out that it is necessary to clean the cement on the surface of the cast-in-place pile when installing the steel pipe column, and the cleaned cement block is difficult to carry. After these light cranes are installed on the sleeve of cast-in-place pile, they can help workers to transport cement blocks out quickly, saving a lot of precious time for the project progress.
In fact, there are many "patented products" similar to gantry grab and light crane in the whole project. These small designs and inventions have played a vital role in the project, which is the result of exploration by many old engineers and small technicians. Minister Liu said excitedly: "This project will certainly become a model for other similar projects. Take those cast-in-place piles as an example. Both depth, volume and accuracy are the first time in the history of Tianjin architecture. The first bid section project will undoubtedly provide a reference for future technical specifications and acceptance criteria. "
The third basement: the most difficult "drama" is left.
Because the second underground floor is still in the construction stage, we can't see the face of the third underground floor for the time being, but what is certain is that the third underground floor will be the most difficult stage of construction. Next, we "swim" the underground three floors from the engineer's mouth and enjoy the wonders of the underground three floors in an abstract way.
According to the on-site personnel, the geological environment in Tianjin is very unfavorable for underground engineering. For example, water can be seen in Tianjin underground 1 meter, while water can be seen in Beijing underground 13 meter. In other words, Beijing's underground engineering can directly let cars drive underground, while Tianjin's underground engineering is absolutely impossible.
The area of the third floor underground will be larger than the above two floors, and there are four floors underground in some areas, which is equivalent to our common "jumping floor" design. These designs improve the difficulty of the project a lot. The deeper the groundwater, the more troubles the project faces and the greater the challenge to the project builders.
Although we can't see the whole picture of the "underground wonders" in the first bid section of Tianjin Railway Station Transportation Hub Project, we have every reason to believe that Tianjin Manufacturing will definitely live up to the expectations and affirmation of Tianjin people from one level and one detail.