Demolition Of Structure Using Implosion Technology 15bk

PROJECT REPORT ON

DEMOLISION OF STRUCTURES USING IMPLOSION TECHNOLOGY

SESSION NO 514 INTEGRATED COURSE IRICEN PUNE

GUIDED BY: SRI. A.K.RAI

(PROFESSOR - WORKS) IRICEN PUNE

PRESENTED BY A. K. ARYA, ADEN (S/E) / PL A.K.SHARMA, ADEN (S) / BRC ARVIND KUMAR, Mgr / IRCON N.K.SHARMA, ADEN (G) / BKN

INDEX Sl.

Description

Page no.

1.

Introduction

1

2.

Methodology

1–3

3.

Demolition of structure using implosion Technology: A case study

3–8

4.

Explosive details

9 – 13

5.

Conclusion

13

ACKNOWLEDGEMENT We are very much grateful to SHRI SHIV KUMAR Director/IRICEN, SHRI A. K. RAI, Course Director and Professor Works for their valuable guidance and consistent encouragement in preparing the project. Finally, we thanks to all faculty and IRICEN staff for offering their valuable assistance and providing a conducive atmosphere to compile these reports in presentable form.

DEMOLITION OF STRUCTURE USING IMPLOSION TECHNOLOGY 1.0 Introduction An implosion is an event where something collapses inward, because the external atmospheric pressure is greater than the internal pressure. For example, if you pumped the air out of a glass tube, it might implode. When a building is surrounded by other buildings, it may be necessary to "implode" the building, that is, make it collapse down into its footprint. You can demolish a stone wall with a sledgehammer, and it's fairly easy to level a fivestory building using excavators and wrecking balls. But when you need to bring down a massive structure, say a 20-story skyscraper you have to haul out the big guns. Explosive demolition is the preferred method for safely and efficiently demolishing larger structures. The basic idea of explosive demolition is quite simple: If you remove the structure of a building at a certain point, the section of the building above that point will fall down on the part of the building below that point. If this upper section is heavy enough, it will collide with the lower part with sufficient force to cause significant damage. The explosives are just the trigger for the demolition. It's gravity that brings the building down. Demolition blasters load explosives on several different levels of the building so that the building structure falls down on itself at multiple points. When everything is planned and executed correctly, the total damage of the explosives and falling building material is sufficient to collapse the structure entirely, so clean-up crews are left with only a pile of rubble.

2.0 Methodology In order to demolish a building safely, blasters must map out each element of the implosion ahead of time. The first step is to examine architectural blueprints of the building, if they can be located, to determine how the building is put together. Next, the blaster crew tours the building (several times), jotting down notes about the structure on each floor. Once

they have gathered all the raw data they need, the blasters hammer out a plan of attack. Drawing from past experiences with similar buildings, they decide what explosives to use, where to position them in the building and how to time their detonations. In some cases, the blasters may develop 3 – D computer model of the structure so they can test out their plan ahead of time in a virtual world. The main challenge in bringing a building down is controlling which way it falls. Ideally, a blasting crew will be able to tumble the building over on one side, into a parking lot or other open area. This sort of blast is the easiest to execute, and it is generally the safest way to go. Tipping a building over is something like felling a tree. To topple the building to the north, the blasters detonate explosives on the north side of the building first, in the same way you would chop into a tree from the north side if you wanted it to fall in that direction. Blasters may also secure steel cables to columns in the building, so that they are pulled a certain way as they crumble. Sometimes, though, a building is surrounded by structures that must be preserved. In this case, the blasters proceed with a true implosion, demolishing the building so that it collapses straight down into its own footprint (the total area at the base of the building). This feat requires such skill that only a handful of demolition companies in the world will attempt it. Blasters approach each project a little differently, but the basic idea is to think of the building as a collection of separate towers. The blasters set the explosives so that each "tower" falls toward the center of the building, in roughly the same way that they would set the explosives to topple a single structure to the side. When the explosives are detonated in the right order, the toppling towers crash against each other, and all of the rubble collects at the center of the building. Another option is to detonate the columns at the center of the building before the other columns so that the building's sides fall inward According to Brent Blanchard, an implosion expert with the demolitionconsulting firm Protec documentation services virtually every building in the world is unique. And for any given building, there are any number of ways a blasting crew might bring it down. Blanchard notes the demolition of the

Hayes Homes, a 10-building housing project in Newark, New Jersey, which was demolished in three separate phases over the course of three years. "A different blasting firm performed each phase," Blanchard says, "and although all of the buildings were identical, each blaster chose a slightly different type of explosive and loaded varying numbers of columns. They even brought the buildings down in different mathematical sequences, with varying amounts of time factored in between each building's collapse." Generally speaking, blasters will explode the major columns on the lower floors first and then a few upper stories. In a 20-story building, for example, the blasters might blow the columns on the first and second floor, as well as the 12th and 15th floors. In most cases, blowing the structures on the lower floors is sufficient for collapsing the building, but loading columns on upper floors helps break the building material into smaller pieces as it falls. This makes for easier clean-up following the blast. Once the blasters have figured out how to set up an implosion, it's time to prepare the building. In the next section, we'll find out what's involved in predetonation prepping and see how blasters rig the explosives for a precisely timed demolition.

3.0 Demolition of structure using Implosion Technology: A case study Introduction An structure which is made by any material is to be demolished after it’s designed age is completed in order to reutilised the valuable land. Demolition was also necessary to remove danger of falling. In western railway, Mumbai division, there was a G+3 storied building numbered as 25/T. It was built in 1924, constructed by BB & CI railway as a first cement concrete residential structure in Mumbai. It was having 80 Nos. (4×20) type I Quarter with total land area about 430 Sq. m. The total height was 13.20 m. above rail level. The structure completed its designed life and existing condition of building was so deteriorated that there was no option but to demolition the same for safety of running trains and ading residents.

Options for Demolition (Conventional Methods) As usual there are two methods for demolition. One by manually and other by mechanical means such as using JCB, Poclains, etc. While planning for the method to be adopted a lot of discussion was held and it was concluded that neither of above method is suitable due to existing constraints around chawl No. 25/T. These were as under. 1.

There were four running lines just ading to structure in east side, the

face of building was just 4.55m away from track centre. 2.

There was a OHE Mast containing portal for five numbers OHE live

conductors at a distance of 5.80 m. from face of building towards north side. 3.

There was stone masonry boundary wall at a distance of 2.80 m. from

face of building. 4.

In addition to above as described railway’s assets, there was a 40 storied

structure about 100 m. away from building to be demolished and one diamond factory exists in the east side having exterior glazed building. Due to above said constraints, manual method was not suitable as it was going to take more time and structure was very near to running track which requires continuous track protection / traffic block. Which would have resulted longer disruptions to running traffic .The mechanical method was not suitable, as there was no space to bring heavy machineries near the structure and to work at a height of 13.50 m. In the context of this project it is advisable and worthy to note that railway context, this method of demolishing would be proved very suitable and useful, most of railway assets i.e. building / structure located nearby running track and in metro cities congested area which already ed their designed life.

Also in the view of Golden Quadrilateral and Freight corridors projects lots of structures will be dismantled during execution of these projects.

Demolition by Implosion When all above-mentioned methods of demolition was not found suitable, the idea of demolition by using implosion technology came to mind as it is being utilizes worldwide. Though it was not tried over Indian Railway till date.’ Implosion’ is a word which derived from word ‘Implode’ which means, make a building collapse down on its footprint. The basic idea of implosion is quite simple, If we remove the of structure of a building at a certain point, the structure of a building above that point will collapse. If the upper section is heavy enough, it will collapse on the lower part of the structure with force to cause significant damage. The explosives are used in these methods are such that the whole structure should fall towards its center of its gravity by just triggering off the explosive in designed manner for demolishing the structures. The true meaning of implosion of structure is to fall on its footprints, but in some cases structures are given desired direction of fall during demolition in order to protect some important existing structures. The advantages of implosion technology method over conventional methods are as under. 1.It is less expensive. 2.There are no ground vibrations 3.ThisMethod is quickest. 4. Suitable for multi-storeyed structures / high piers, cabins, distressed piers etc.

Important Aspect of Implosion Technology Following are important aspects of Implosion Analysis of Existing structure & locating weak points

The approximate strength of left on R.C.C / PSC member worked out by taking the core of concrete, In order to decide quantity /location of explosive to be provided. In our case the structure was very much dilapidated and unsafe, there was no need to carry out such tests as weakening of strength of structure was done by making the vertical columns from ading partition wall, which were of RCC

Drilling of holes for placement of explosive The holes were drilled of about 25 mm to 30 mm dia and about 20 to 30 cm deep depending upon quantity of explosive energy is required to break a particular .

In this case the building was planned to bring down on

its footprint. We provided 20 holes of 25mm dia & 30 cm in depth central column .It was reduced to 4 holes of 25mm dia & 20cm deep

(4x1) at

columns away from centre

Holes drilled in columns for placement

Quantity of Explosive The quantity of explosive to be placed depends upon the size of column and extent up to which it is to be destroyed. Depending on above requirements we placed 250 gm of explosive in central 24 columns. & 125 gm in outer 16 columns, because it was desired to destroy the central column completely. No outer column was weakened so that the building collapsed towards its centre from both side.

Type of explosive & Detonators There are two types of explosive commonly used for implosion RDX & gelatin. In this case we used brand name ‘Power Gel ‘ explosive, which is, ammonium

nitrate based explosive which expand at very high speed and applies at a very high pressure of about 600 T/sq inch. The electronic detonators were used to ignite the explosive.

Ground floor

PLACEMENT OF EXPLOSIVES – CROSS SECTIONAL VIEW

Test Blast Before carrying out the actual blasting; We done a test blast, in ordered to ascertain the efficiency of explosive & detonators and also to develop a level of confidence as this was a specialized work and executed 1st time on in Indian railway. BEFORE

AFTER

Wrapping of holes The wrapping of holes is done to ensure that due to explosion of charges the debris does not fly in air. For this purpose, the holes were covered with gunny bags and iron net after placement of explosive and detonators.

Ballasting Ballasting of Charges / Explosives work are carried out in a controlled manner such that there will be a time gap of 1/100 second between two successive blasts. The trigger of charges is done in such a control manner so that the noise pollution and air pollution should be minimum. The central column is first triggered and then blast proceed towards outside to produce three way action and hence results the fall of existing structure on its footprint.

Falling of structure Once central /column will be destroyed and ading columns will be weakened, due to its gravity the entire mass will come down on its footprints. In this case after blasting within few seconds the entire structure of (g+3) storied came down on its footprint without damaging any ading asset.

4.0 Explosive Explosive, substance that undergoes decomposition or combustion with great rapidity, evolving much heat and producing a large volume of gas. The reaction products fill a much greater volume than that occupied by the original material and exert an enormous pressure, which can be used for blasting and for propelling.

Classification of Explosives Chemical explosives can be classified as low or high explosives. Low (or deflagrating) explosives are used primarily for propelling; they are mixtures of readily combustible substances (e.g., gunpowder) that when set off (by ignition) undergo rapid combustion. High (or detonating) explosives (e.g., TNT) are used mainly for shattering; they are unstable molecules that can undergo explosive decomposition without any external source of oxygen and in which the chemical reaction produces rapid shock waves. Important explosives include trinitrotoluene (TNT), dynamite, nitrocellulose, nitroglycerin, and picric acid. Cyclonite (RDX) was an important explosive in World War II. Ammonium nitrate is of major importance in blasting.

Applications of Explosives (Detonators and Dynamite) In the last section, we saw how blasters plan out a building implosion. Once they have a clear idea of how the structure should fall, it's time to prepare the building. The first step in preparation, which often begins before the blasters have actually surveyed the site, is to clear any debris out of the building. Next, construction crews, or, more accurately, destruction crews, begin taking out non-load-bearing walls within the building. This makes for a cleaner break at each floor: If these walls were left intact, they would stiffen the building, hindering its collapse. Destruction crews may also weaken the ing columns with sledgehammers or steel-cutters, so that they give way more easily. Next, blasters can start loading the columns with explosives. Blasters use different explosives for different materials, and determine the amount of explosives needed based on the thickness of the material. For concrete columns, blasters use traditional dynamite or a similar explosive material. Dynamite is just absorbent stuffing soaked in a highly combustible chemical or

mixture of chemicals. When the chemical is ignited, it burns quickly, producing a large volume of hot gas in a short amount of time. This gas expands rapidly, applying immense outward pressure (up to 600 tons per square inch) on whatever is around it. Blasters cram this explosive material into narrow boreholes drilled in the concrete columns. When the explosives are ignited, the sudden outward pressure sends a powerful shock wave busting through the column at supersonic speed, shattering the concrete into tiny chunks. Demolishing steel columns is a bit more difficult, as the dense material is much stronger. For buildings with a steel structure, blasters typically use the specialized explosive material cyclotrimethylene trinitramine, called RDX for short. RDX-based explosive compounds expand at a very high rate of speed, up to 27,000 feet per second (8,230 meters per second). Instead of disintegrating the entire column, the concentrated, high-velocity pressure slices right through the steel, splitting it in half. Additionally, blasters may ignite dynamite on one side of the column to push it over in a particular direction. To ignite both RDX and dynamite, you must apply a severe shock. In building demolition, blasters accomplish this with a blasting cap, a small amount of explosive material (called the primer charge) connected to some sort of fuse. The traditional fuse design is a long cord with explosive material inside. When you ignite one end of the cord, the explosive material inside it burns at a steady pace, and the flame travels down the cord to the detonator on the other end. When it reaches this point, it sets off the primary charge.

These days, blasters often use an electrical detonator instead of a traditional fuse. An electrical detonator fuse, called a lead line, is just a long length of electrical wire. At the detonator end, the wire is surrounded by a layer of

explosive material. This detonator is attached directly to the primer charge affixed to the main explosives. When you send current through the wire (by hooking it up to a battery, for example), electrical resistance causes the wire to heat up. This heat ignites the flammable substance on the detonator end, which in turn sets off the primer charge, which triggers the main explosives.

To control the explosion sequence, blasters configure the blast caps with simple delay mechanisms, sections of slow-burning material positioned between the fuse and the primer charge. By using a longer or shorter length of delay material, the blasters can adjust how long it takes each explosive to go off. The length of the fuse itself is also a factor, since it will take much longer for the charge to move down a longer fuse than a shorter one. Using these timing devices, the blasters precisely dictate the order of the explosions. Blasters determine how much explosive material to use based largely on their own experience and the information provided by the architects and engineers who originally built the building. But most of the time, they won't rely on this data alone. To make sure they don't overload or under-load the structure, the blasters perform a test blast on a few of the columns, which they wrap in a shield for safety. The blasters try out varying degrees of explosive material, and based on the effectiveness of each explosion, they determine the minimum explosive charge needed to demolish the columns. By using only the necessary amount of explosive material, the blasters minimize flying debris, reducing the likelihood of damaging nearby structures. To further reduce flying debris, blasters may wrap chain-link fencing and geotextile fabric around each column. The fence keeps the large chunks of concrete from flying out, and the fabric catches most of the smaller bits. Blasters may also wrap fabric around the outside of each floor that is rigged with explosives. This acts as an extra net to contain any exploding concrete

that tears through the material around each individual column. Structures surrounding the building may also be covered to protect them from flying debris and the pressure of the explosions. When everything is set up, it's time to get the show underway. In the next section, we'll find out what final steps the blasters must take to prepare for the implosion, and we'll look at the implosion itself. We'll also find out what can go wrong in explosive demolition and see how blasters evaluate the project once the smoke has cleared. In the last couple of sections, we looked at everything blasters do to prepare a building for implosion. In addition to these measures, the blasters must prepare the people in the area for the blast, assuring local authorities and neighbouring businesses that the demolition won't seriously damage nearby structures. The best way blasters can calm down anxious authorities is by demonstrating the firm's success with previous implosions. c uses portable field seismographs to measure ground vibrations and airblasts during an implosion. Brent Blanchard, an operations manager for the company, says that they also inspect surrounding structures prior to the implosion, so that they can help assess any damage claims following the blast. Additionally, Protec's staffs videotape the blast from multiple angles so that there is a record of what actually happened. Using data collected from previous blasts, the company's engineers can predict ahead of time what level of vibration a particular implosion may cause. Once the structure has been pre-weakened and all the explosives have been loaded, it's time to make the final preparations. Blasters perform a last check of the explosives, and make sure the building and the area surrounding it are completely clear. Surprisingly, implosion enthusiasts sometimes try to sneak past barriers for a closer view of the blast, despite the obvious risks. With the level of destruction involved, it is imperative that all spectators be a good distance away. Blasters calculate this safety perimeter based on the size of the building and the amount of explosives used. On occasion, blasters have misjudged the range of flying debris, and onlookers have been seriously injured. Blasters might also overestimate the amount of explosive power needed to break up the structure, and so produce a more powerful blast than is necessary. If they underestimate what explosive power is needed, or some of the explosives fail to ignite, the structure may not

be completely demolished. In this case, the demolition crew brings in excavators and wrecking balls to finish the job. All of these mishaps are extremely rare in the demolition industry. Safety is a blaster's number-one concern, and, for the most part, they can predict very well what will happen in an implosion. Once the area is clear, the blasters retreat to the detonator controls and begin the countdown. The blasters may sound a siren at the 10-minute, five-minute and one-minute mark, to let everyone know when the building will be coming down. If they are using an electrical detonator, the blasters have a detonator controller with two buttons, one labelled "charge" and one labelled "fire." Toward the end of the countdown, a blaster presses and holds the "charge" button until an indicator light comes on. This builds up the intense electrical charge needed to activate the detonators (this is similar to charging a camera flash to build the necessary electrical energy to illuminate a scene). After the detonator-control machine is charged, and the countdown is completed, the blaster presses the "fire" button (while still holding down the charge button), releasing the charge into the wires so it can set off the blasting caps. Typically, the actual implosion only takes a few seconds. To many onlookers, the speed of destruction is the most incredible aspect of an implosion. How can a building that took months and months to build, and stood up to the elements for a hundred years or more, collapse into a pile of rubble as if it were a sand castle? Following the blast, a cloud of dust billows out around the wreckage, enveloping nearby spectators. This cloud can be a nuisance to anyone living near the blast site, but blasters point out that it is actually less intrusive than the dust kicked up by non-explosive demolition. When workers take down buildings using sledgehammers and wrecking balls, the demolition process may take weeks or months. In this time, a significant amount of dust is being kicked up into the air every day. When the building is levelled in one moment, on the other hand, all the dust is concentrated in one cloud, which lingers for a relatively short period of time. Nearby residents with allergies can leave the area for that one-day and avoid the dust entirely. After the cloud has cleared, the blasters survey the scene and review the tapes to see if everything went according to plan. At this stage, it is crucial to confirm that all of the explosives were detonated and to remove any

explosives that did not go off. If a demolition consulting crew was on hand, the blasters review their vibration and air blast data as well. Most of the time, experienced blasters bring buildings down exactly as planned. Damage to nearby structures, even ones immediately adjacent to the blast site, is usually limited to a few broken windows. And if something doesn't work out quite right, the blasters log it in their mental catalogue and make sure it doesn't happen on the next job. In this way, job-by-job, the science and art of implosion continues to evolve.

5.0 Conclusion It is concluded that this methodology of demolishing building / structure will prove very useful, economical and quickest in contest of future planned project in Indian railway i.e. quadrilateral project and freight corridor project, as during these projects lot of buildings/structures will fall in the alignment of new lines located nearby existing running lines.