There are so many high-rise buildings in China's city center, how to demolish them when they reach the end of their useful life? Blasting, toppling? None of them would be feasible and would not only jeopardize the safety of the surrounding buildings, but would also lead to a series of traffic and air problems. And the Japanese demolition method may give us a revelation.
As the saying goes, "success is not good, failure is also failure", human beings may never have imagined that the urbanization they once pursued would now bring negative environmental and cultural impacts, overwhelming a new generation of young people.
However, it is very difficult to solve this problem, because in order to expand the land use rate, the construction of cities has often been developed to a higher place, in short, the buildings need to be built very high, so that they can accommodate more residents or commercial volumes in a fixed area.
Moreover, in order to build more saleable buildings and increase development profits, many developers often choose to reduce the distance between buildings during the design stage.
The combination of these two factors also means that there are few conditions for demolition in places with dense real estate, after all, if a high-rise building starts to be demolished, it will inevitably cause problems such as falling stones, flying debris and noise pollution.
Obviously, no matter which situation happens, it will make the surrounding residents miserable, and in serious cases, it will even cause safety accidents, such as chain collapse, and the consequences will be unimaginable.
In the face of such a dilemma, some people may think that since high-rise buildings are so difficult to demolish, it is better to wait for them to reach the end of their useful life, and then demolish them on a regional basis, at least this can minimize the impact.
First of all, as far as the current urban development situation is concerned, there are differences in the construction time of commercial areas and residential areas in the same area, which means that there are differences in their service life itself, and it is difficult to achieve true unity.
Second, there are differences in the quality of construction between developers, and even if they are built in the same phase, they will not be able to end at the same time, making it almost impossible to achieve regional demolition.
Therefore, the core point of solving the problem is to return to the study of demolition methods.
When it comes to the method of demolition, I believe the first thing that comes to everyone's mind is blasting, in fact, this is indeed the most classic and practical method.
The engineer only needs to place the blasting explosives in the building scale, and set the explosive equivalent, and after the ** sound passes, the blasting and demolition of the building can be completed.
However, all this is just the surface, the real blasting and demolition is actually very complicated, and there are as many as three types of mainstream blasting methods, namely directional dumping method, in-situ vertical collapse method, and implosion method.
Among them, directional dumping is the most traditional and efficient blasting method, which essentially blows a triangular incision in the lower floor of the building, so that the whole building falls in that direction.
This blasting method is relatively simple and has a high success rate, but it needs to reserve a dumping space of three-quarters of the building height, coupled with a safe evacuation range, which makes the dumping method have high requirements for the space scope and is not suitable for dense building complexes.
In contrast, the in-situ vertical collapse method uses slightly less space, after all, this blasting method relies on the destruction of the load-bearing structure to allow the building to collapse in place.
The implosion method is the same, except that it is improved on the basis of the collapse method, so that the direction of collapse becomes from the outside in, which further reduces the required space, ensures the safety of peripheral personnel, and makes this method also available in building complexes.
However, whether it is the traditional directional dumping method, or the improved collapse method and the implosion method, they will inevitably cause double pollution of the environment and noise, which is the disadvantage of blasting and demolition.
However, in this predicament, Japan, as a pioneer of urbanization in Asia, has developed two new demolition methods based on its previous experience in urban reconstruction, and both of these methods are enough to shock the world.
First of all, the first method is called the lever system demolition method (also known as the building demolition method, which is a new, top-down demolition method.
Its essence is similar to that of a hydraulic press, which is to "compress" the building from top to bottom, so that the whole building disappears layer by layer.
According to the information released in Japan, this demolition method requires the construction of a three-storey external structure on the roof of the demolished building, just like the scaffolding used in construction.
At the same time, in order to ensure the beauty of the building when it is demolished, the external structure also needs to be built the same as the original building, for example, the demolished building is a cylinder building, then the outer structure needs to be built into a circle, if it is a square building, the outer structure needs to be made square.
In this way, the Japanese wanted to minimize the impact of the demolition on the surrounding citizens, because the outer structure is located on the top floor and resembles the shape of the original building, so that many unobservant citizens will not be aware of its existence and will not be aware that the building is being demolished.
In addition, the exterior structure also insulates the noise and dust from the construction, which makes it even more difficult for nearby residents to notice, and the only thing they can feel is that the demolished building will gradually become shorter as the demolition progresses.
However, it should be noted that although the external structure is built at a high end, the demolition work within the structure is actually the same as the traditional demolition method, that is, relying on manual and mechanical demolition to carry out the demolition on a floor-by-floor basis.
To put it simply, when the Japanese construction team completes the construction of the outer structure, it will first use a crane to dismantle the top floor of the demolished building, and then the workers will enter the top floor to continue the demolition of other frames, and when the entire floor is removed, the crane will dismantle the lower ceiling again, and the workers will enter the building again, and so on, until the demolition of the entire building is completed.
From this point of view, it is not difficult to find that this kind of demolition method in Japan can be described as extremely delicate, but as the saying goes, "slow work makes careful work", which means that the delicate demolition work is bound to be quite time-consuming.
According to the estimation of Japanese engineers, although this demolition method can reduce the demolition noise by 20 decibels, and can also reduce the demolition dust by 90, but the dismantling of a floor will take five days, if the demolished building is 40 floors high, the whole project will take more than half a year.
For example, the main body of the 100-meter-high Akasaka Prince Hotel, using this dismantling method, its construction period is as long as two years, while the cross-linked cable workshop of the Guotai Road project in Panyu, Guangzhou, which is also 100 meters high, was demolished in only one day in the mode of blasting and demolition.
So, in terms of efficiency, this is not comparable to blasting and demolition.
Some people may put forward the point of view of environmental protection, but we must be clear that the construction period is also very important, although the blasting and demolition has a great impact, but the time limit is only one day, and Japan's demolition mode although the impact is small, but the impact time is very long, so the two are calculated, the pollution problem is not yet known.
However, the Japanese seem to like this new and deviant approach, because in addition to the top-down demolition method, they also have a bottom-up demolition model--- the slow-down demolition method ().
This model is the opposite of the building demolition method mentioned above, which requires the entire building to be held up with a hydraulic jack, and then the construction team to demolish the ground floor of the building, and when the first floor is completely demolished, the hydraulic roof will put the building down as a whole, so that the workers can demolish the new ground floor again.
In this way, the entire construction process can always be maintained on the first floor, which reduces the danger of construction for workers and reduces the amount of dust from high-altitude dismantling.
However, the way in which the construction is kept on the first floor makes the impact of the demolition project on the surrounding area still very large.
Therefore, even though these two methods of demolition in Japan have won numerous international awards, no other country has followed suit, which shows the practicality.