According to the company, this method greatly reduces the environmental impact of the demolition, as well as the time. Kajima says that it speeds up the task by 20%, while making it easier to separate materials for recycling, as well as reducing the amount of products released into the air.The process is called daruma-otoshi after a Japanese game that makes players take the bottom parts of a column—using a hammer—without disturbing the rest of the parts above.
For those of you who don't understand how this is faster, you need to remember that in normal demolition, a company needs to place the explosives in the positions where it will do damage, but not damage the surrounding areas. They don't just put a load of TNT inside and hope for the best. Usually it begins with talking to the building planners while trying to get the blueprints for the building. Afterwards, they need to go level by level drilling into walls to get to the support structures that they need to break down. This takes a long time, especially on a buildings that has more than five floors to it.
It's really saving time to remove one floor slowly, depress it, and remove the next. It may sound longer, but most videos of demolitions ignore the planning phase that wastes time.
Thanks to Gemssty for the link.