How Building Implosions Work

How do you knock down a large building in a crowded city? Implode it. Implosion is using explosives and gravity to reduce a structure to debris.

How do you take down an old 20-story building in the middle of a busy city quickly and cost effectively? Well, implode it.

WHAT IS IMPLOSION?

Implosion is the direct opposite of explosion. Everyone has seen an explosion - a charge goes off and something solid is ripped into a lot of little pieces that fly all over the place, making everyone in the vicinity take cover. An implosion is the strategic placement of explosive charges that actually destroy the structural integrity of the building causing it to fall not out, but in upon itself (this is often referred to as falling into its own footprint). Imagine wooden blocks stacked on top of each other; pull out a few of the bottom blocks and the structure falls by gravity.

For many years, the only way to remove a large structure in a busy, crowded city was to take it apart piece by piece which could take months and cause surrounding streets to be shutdown for weeks at a time. This is not acceptable. Enter - Implosion.

Implosion is the removal/destruction of the inner structure of a building which allows gravity to pull the entire building down upon itself. The weight of the upper part of the building usually destroys the lower portion of the building. Explosives are used to start the destruction, but gravity takes over and completes the job.

PLANNING AND PREPARATION IS CRUCIAL

To bring down a building in a controlled manner there must be a great deal of planning. The structural blueprints must be studied to determine how the building was constructed and any additional structural changes (such as reinforcing columns) that may have been made since the initial construction. It is important to know exactly where the key structural supports are for the building.

Demolition experts go through the building to determine the best location for explosive charges. This also where they map out exactly which type of explosive and how much will be used. Often some manual demolition may have to take place to ensure that the building will fall exactly where the planners want it to fall. This may mean sawing through steel girders and reinforced concrete columns or breaking down brick or concrete walls in the bottom portion of the building. If the amount of explosive isn't large enough the building may not come all the way down or may fall in the wrong direction. If the amount of explosive is too much, the building debris can fly far from the blast site causing injury and property damage.

Timing of explosions also has to be planned. Generally, the support structures at the bottom of the building will be blasted first and some smaller explosions in the upper floors next to ensure proper implosion.

The most important aspect of the planning is to make sure that the building falls exactly where they want it to fall. Whether the plan is to have the building fall inside itself or in a safe direction, the planning must be exact or harm can come to other structures or people.

Planning also includes the safety of other buildings surrounding the target to be demolished. Plywood may be used to cover windows in other buildings or padded tarps and sheeting to cover gardens and statuary.



The demolition company will bring in the police for control of the blast area. The police will be required to ensure that no one is within the designated perimeter. Depending on the size of the blast, it could be several city blocks. No one will be allowed to stay in surrounding buildings to watch the action due to safety concerns.

The planning and preparation stage can take a few weeks or months depending on the size of the building and the surrounding area to be protected.

WHAT HAPPENS THE DAY OF THE IMPLOSION

Several hours before the time of the implosion lots of activity is happening.

The police are vacating everyone from the area not involved in the job and from the buildings surrounding the blast site.

Demolition experts are checking all the explosives and charges to make sure they are working well. Connections between the individual blast fuses and the central detonator control are checked and re-checked.

Sirens are sounded at specific times to let everyone in the vicinity of the blast know how when the explosives will be detonated. Sirens may sound at intervals at 20, 15, 10, 5 and 1 minute before the blast.

At the predetermined time the blaster pushes the buttons to charge and fire the explosives. Then, months of planning and work come down to a few seconds of loud bangs, falling bricks, and lots of dust, then a building is reduced to rubble and dust in the middle of its footprint.

The cloud of dust will disperse and the area is checked for any damage to surrounding structures and, more importantly, check to make sure that ALL the explosives detonated. If not, the cleanup team could be harmed when clearing away the debris.

Once it is determined that no explosives have been undetonated and the area is safe, the cleanup company will come in and clear out all the debris from the former building.

Implosion technology is an art. Each time a building is imploded it is analyzed and the best practices are kept and any problems are discussed and solutions to those problems are developed.

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