Or detonate the explosive on one side of the column to push it in a specific direction
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The fence keeps large pieces of concrete from flying out, while the fabric catches most of the smaller pieces
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-The typical way of high-rise building blasting is as follows: panoramic view before demolition, blasting design, determination of dumping direction, determination of blasting floor, determination of blasting components, determination of which components are to be demolished in advance, which parts are to be demolished by blasting, which parts are to be cut off first, and so on
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If the height of the cut is too small, it may cause the embarrassing situation of blasting backward but not collapse, and if it is too large, it may lead to the dangerous situation of superstructure overturning
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The implosion of a building is not a real implosion
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Implosion method is very suitable for crowded urban space, which is widely used in the United States, but the method is very complex, and there are few domestic cases
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Some groups have applied to the governor’s office to keep the Georgia Dome, but the government thinks that it is not economically feasible to keep a stadium with 70000 people
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It is very suitable for the blasting of steel-concrete structures
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Fence and fabric protection to further reduce flying debris, wrap fence and geotextile around each post
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We understand it as a conventional name
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For large-span spatial structures, there are not many cases of blasting demolition
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In order to ensure that the columns will not be overloaded or underloaded, some columns will be tested before blasting, and the blasting engineer will determine the minimum explosive charge required to demolish the columns according to the test blasting situation
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Therefore, it was finally decided to demolish the Georgia Dome by blasting
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Due to the system innovation, this type of dome is called levy dome
.
02
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-Three blasting methods – 01
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However, the term implosion is often used to describe such demolition
.
03
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It can make the building collapse almost completely in its own area
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Why should such a historic building be demolished? Xiao Bian checked it on the Internet
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For higher buildings, multiple incisions can be arranged to form folding and toppling and shorten the collapse distance
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The surrounding buildings and facilities are safe and sound
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Detonator, delay device
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Implosion method the rule of implosion is to destroy the load-bearing structure inside the building in turn, so that the external components will fall inward, collide and fragment with each other, and then collapse
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The main building is 56m high and the highest point (elevator power room) is 68.4m
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For example, if you extract air from a glass tube, it may implode
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During the blasting process of the Georgia Dome, the distance between the Georgia Dome and the new gymnasium is only 25m
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The amount of explosive used in the test blasting can be calculated according to the drawings of the original structure
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-Emulsion explosive the main component of emulsion explosive is ammonium nitrate, the detonation velocity is about 4000 m / s, the price is low, and it is widely used
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This method is simple in construction and has high success rate, which is the most commonly used method in China
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However, if the strength of the building itself is relatively high, it is possible to blow up the lower floors and sit down completely on the upper floor
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It’s also called directional blasting
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After consulting the relevant information, he found that the construction blasting is quite different from his previous imagination
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Usually, a collapse site larger than 2 / 3 ~ 3 / 4 of the building height should be reserved
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Due to the higher strength of steel than concrete, special explosive material cyclotrimethylenetriamine (RDX) is usually used for buildings with steel support structure
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In fact, instead of smashing the whole steel column, the slices formed by the explosion are directly passed through the steel plate and cut into two halves
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This article is excerpted from: istructureid: istructure2017 at the opening ceremony of the spatial structure conference in mid November 2017, Professor Lantian delivered a speech, sharing his recent experiences and thoughts during his visit to the United States and Canada
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In situ vertical collapse method in situ vertical collapse method is to make the load-bearing structure at a certain height at the bottom of the building blasting instantaneously, so that the vertical collapse impact the ground and disintegrate
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Different explosives are used for different materials, and the quantity of explosives required is determined according to the thickness of the materials
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This explosive material is plugged into a narrow borehole
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By reducing the amount of explosive as much as possible, the splashing debris is minimized and the possibility of damaging nearby buildings is reduced
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For blasting demolition, many people’s first impression may be like this
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Next, I’d like to briefly introduce my study notes to you, mainly related basic knowledge, a demolition case of a high-rise and a long-span concrete dome
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Atmospheric pressure does not pull or push the structure inward, but gravity makes it collapse
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After blasting, the main building tilted 17.1m to the south, and the elevator power house tilted 30.6m
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When a chemical is ignited, it burns rapidly and produces a large amount of hot gas in a short time
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Partition walls are not load-bearing, but they can also prevent the collapse of the structure
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The Georgia Dome may not be implemented for a long time, and there is no relevant information on the Internet.
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Nowadays, there are three main ways of Blasting Demolition: directional dumping method, in-situ vertical collapse method and internal blasting method
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The explosion height is 11.6m
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On February 28, 1999, the 16 storey ward building of Shanghai Changzheng Hospital opened multiple incisions in the same direction and collapsed in the predetermined range according to the design direction
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But actually, it’s an explosion, not a blast
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Generally, only 1 / 3 ~ 1 / 4 of the building height of the collapse site can be reserved
.
02
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And set the blasting time, 0.3s delay ~ 1.75s delay
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The main component of plastic explosive is cyclotrimethylenetriamine
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But most of the time, blasting doesn’t just rely on these data
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The delay of the component near the dumping direction is less than that far away from the dumping direction
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The former Georgia Dome was built in 1992 and designed by levy et al
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As the main stadium of the 1996 Atlanta Olympic Games
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Directional dumping method is to blast a triangle cut in the lower part of the building to make the building fall towards the cut direction, impact the ground and disintegrate
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The preparation work before blasting is to remove the soft equipment and weaken the partition wall in advance
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When the explosive is ignited, the sudden outward pressure will send out a strong shock wave, which will destroy the column at supersonic speed and crush the concrete into tiny blocks
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When it comes to the historic Georgia Dome, which was demolished by blasting on November 20, 2017, we are deeply sorry
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Strictly speaking, implosion is an internal collapse event, because the external atmospheric pressure is greater than the internal pressure
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For concrete column, traditional emulsion explosive can be used
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The core idea of blasting demolition is not to blow up the whole building, but only to destroy the key load-bearing structure, so that the building can collapse in a controlled way and break into small pieces as much as possible under the action of gravity
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It is mainly suitable for brick buildings, single-layer bent workshop and other buildings with low structural strength
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The gas expands rapidly, exerting a huge outward pressure (about 10 GPa) on any surrounding material
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Explosives are just absorbent fillers immersed in highly flammable chemicals or mixtures of chemicals
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And try to reduce the impact on the surrounding environment
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The old and new gymnasiums took a group photo
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How to ensure that the fragments of the building blasting will not affect the new gymnasium? Xiaobian is not an expert in this field
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For example, the surrounding houses and subway lines will put forward higher requirements for blasting demolition
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A new stadium with a retractable roof has been built on the south side of Georgia stadium, which is very close
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The detonation velocity can exceed 8000m / s, which can cut off the steel directly
.
RDX based explosive compounds expand at a very high rate, up to 8230 meters per second
.
