Implosion or 10 Sec demolition: a technique that involves controlled demolition of large urban structures
Chennai’s first iconic demolition
For the first time in Chennai, a building is being demolished using the 'Implosion technique' (use of controlled explosion). As the ill-fated residential tower at Moulivakkam bites the dust today, it is highly interesting to note how the entire crew goes about planning the spectacular demolition or implosion, which has rather become one of the biggest demolitions of the residential structures in the recent times.
This classic controlled technique brings the entire structure down into its footprint causing the structure to break inward from inside to outside and bottom to top. Timing and a detailed structural analysis is highly critical to any successful implosion. It involves numerous small blasts with the use of explosives like gelatin, RDX, detonators and ignitors, and ammonium nitrate. These explosives are planted into the strategic pockets of the critical support columns of the building and at the touch of a button, the detonation happens in a programmed manner. With precise planning, major damages to the surrounding structures could be avoided. It would require at least 30-40 days to pre-weaken the building before implosion. When a building is surrounded by other buildings, an explosive demolition is the preferred method for safely and efficiently demolishing larger structures.
The Inside Story:
In order to carry out the demolition safely, each and every element of the implosion is mapped out ahead of time. As every building is unique, the most important step is to examine the architectural blueprints of the building, to primarily determine how the building is designed and put together. Then the support pillars of the building are analyzed to plan the intensity and configurations of the explosives. In some cases advanced technology is deployed to test out the plan in the virtual world by developing 3-D computer models of the structure.
History: A closer look
The history of building implosion is often linked to the development of explosive technology. One of the earliest documented attempts at building implosion would be the 1773 razing of Holy Trinity Cathedral in Waterford, Ireland with 150 pounds of gunpowder, and a huge amount of explosives at the time. The use of low velocity explosive produced a deafening explosion that instantly reduced the building to rubble. On October 24, 1998, the J. L. Hudson's Department Store and Addition became the tallest, and the largest, building ever imploded. The evolution in the mastery of controlled demolition led to the world record demolition of the Seattle Kingdome on March 26, 2000.