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The Contribution of Controlled Demolition (CD) towards

Disaster Effects Reduction

A T M Mozaffor Hossain *

Abstract

Natural disasters are inevitable, followed by catastrophic effects. The increasing

trends of human induced hazards like infrastructure collapses are witnessed over the

recent past. In this paper, an attempt has been made to analyze the nature of disaster

in Bangladesh. Its effects are identified with the evaluation of damage extent. Their

occurrence may be beyond control, but the aftermath effects could be well managedprovided that high technologies are adopted in time. This paper highlights some

widely practiced examples of applied CD technologies and policy implications to

assess their suitability in the context of Bangladesh.

Keywords: Controlled Demolition, Disaster Effects, Nature of Disaster, Non-

Explosive Demolition, NONEL tube.

Introduction

Bangladesh is a low-lying deltaic country with hundreds of rivers and

tributaries. The geographical location, land characteristics, multiplicity of

rivers, monsoon climate and coastal morphology renders Bangladesh as highly

vulnerable to natural hazards. Human induced hazards add a new dimension to

disaster effects. Climate change has become the root causes of many disasters.

The effects due to disaster are multidimensional, causing death toll of lives,

destruction of property and so on.

Demolition is the tearing-down of buildings and other structures; the opposite

of construction. The concept of using energy produced by explosives came up

with the invention of black powder in 808 AD in Tang Dynasty in China. This

invention and application has led the transferring of chemical energy to

mechanical energy. The development of various destructive explosives namely

Picric Acid (PA), Tri Nitro Toluene (TNT), Hexogen (RDX), Nitroglycerin

(NG) and blasting cap enhanced the destructive applications in different field

engineering works in World War II. Controlled demolition, often known as'Controlled Blasting', is to perform engineering works to a desired extent with

the control of blasting energy released out of an explosive blasting so that

harmful effects are reduced to a tolerable limit.

* Assistant Inspector of Colleges, Bangladesh University of Professionals

Email: [email protected]

BUP JOURNAL, Volume 1, Issue 1, September 2012, ISSN: 2219-4851

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The invention of new demolition theories, technologies, equipments, switching

over to NONEL (Non- Electrical) tube and NONEL detonator from electric

firing system, and overwhelming advantages of CD over manual or mechanical

means have led to an extensive use both in war and peace in differentengineering works in the developed countries.

CD technology can reduce disaster effects, especially aftermath. Simply,

blasting energy used in a controlled way can do and undo many civil

engineering works. Blasting can remove or even build a portion of dam. It can

excavate under water, sand or mud, and remove debris from a drainage outlet.

Safe dismantling of partially collapsed structures, rescue entrapped people and

creating an access to the damaged sites are the remarkable contributions of CD

technology. Even it can fight fires. Most importantly, CD works lead towards

environmental friendly activities.

Objectives of the Study

This study focuses on analyzing the nature of disasters occurring in

Bangladesh with identification of their effects. The concept of CD technology

developed around the world and various examples of its applications are

studied with a view to explore them to reduce disaster effects in the context of

Bangladesh.

Methodology of the Study

This study is based on both primary and secondary data. Primary data includes

the work experiences on demolition works both at home and abroad

(dismantling of high rise building, chimney, rock blasting etc. in China).

Secondary data includes a handbook on CD- Peoples Liberation Army

University of Science and Technology(PLA UST), China; work experiences

of a world leading CD expert-Controlled Demolition Inc. (CDI), U.S.A;different published materials like 'Applied Explosive Technology for

Construction and Mining'; and writings of some other scholars. The nature of

disaster is analyzed followed by an identification of its effects. A ruthless

study is made on the concept of CD technology developed around the world.

And based on the practical experiences and relevant examples from CD

practices, different applications of CD technologies are brought in to reduce

disaster effects in Bangladesh. At last, a model of CD to reduce the disaster

effects and few policy implications are proposed to make CD technology moreeffective in the context of Bangladesh.

The Contribution of Controlled Demolition (CD) towards Disaster Effects Reduction

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Figure 1: Methodology of the Study

The Nature of Disasters with their Effects in Bangladesh: An Overview

The geographical features of our landscape have made Bangladesh vulnerable

to disaster. Natural and human induced hazards such as flood, tornado,

cyclone, storm surges, earthquake, tsunami, land slide, fire, infrastructure

collapse, and various forms of pollution increase the vulnerability of inland

and coastal dwellers. Climate change adds a new dimension to community risk

and vulnerability. Current indications of disaster or calamity include not onlyseverances, but also their occurrences outside the established seasons.

Flood and its Effects

Flood is a part of 'Water Cycle' which is natural. Every year Bangladesh

experiences regular river flood affecting 20% to 68% of the country. The

floods of 1988, 1998 and 2004 were particularly catastrophic, resulting in large

scale destruction and loss of lives.

Flood raises water level and thereby everything goes under water. The extent

of damage depends on the withstanding period of water. The 1998 flood lasted

for 65 days and affected about 67% area of the country.

Workshop on Disaster

Response Exercise &

Exchange (DREE-2011)


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Tornado and its Effects

A tornado is a violent, dangerous, rotating column of air that is in contact with

both the surface of the earth and a cumulonimbus cloud or in rare cases, the

base of a cumulus cloud. They are often referred to as a twister, cyclone or

nor'westers (Kalbaishaki). Tornado characterized by local severe storm, waves

over Bangladesh at different times.

Tornado brings two devastating effects, one is the severe storm and the other is

pre-monsoon rain. The high speed wind damages structures like houses,

buildings, towers, pylons, trees etc. completely or partially. And, the pre-

monsoon rain can also cause flood.

Cyclone, Storm Surges and their Effects

Cyclone refers to as a system of winds rotating around a center of low

atmospheric pressure. Cyclonic circulation and relatively low atmospheric

pressure usually coexist. Tropical cyclones from the Bay of Bengal

accompanied by storm surges are one of the major disasters in Bangladesh.

Bangladesh has experienced numbers of cyclones over the periods. The country

is one of the worst sufferers of all cyclonic casualties in the world.

Cyclone brings high tidal waves (saline water intrusion) with a plummetedwind speed. The energy released by the tidal waves and wind destroys the

structures all through followed by a saline water intrusion and mud or silt

deposition.

Earthquake and its Effects

An earthquake (also known as a quake, tremor or temblor) is the result of a

sudden release of energy in the earth's crust that creates seismic waves.

Bangladesh and the North-Eastern Indian states have long been one of theseismically active regions of the world, and have experienced numerous

earthquakes during the past 200 years.

Earthquake causes collapsing of all types of structures including towering and

large area structures completely or partially. Earthquake disrupts the entire

utility system including supply of gas, electricity, water, sewerage,

communication etc. leading to a heap of debris. The disrupted utility system,

especially the gas or electricity supply line may cause fire. According to recentprediction, some 85,000 buildings of the Dhaka city will suffer medium to

more damage if there is an earthquake in the range of 7.0 to 7.5 in Richter

scale. This was revealed in a study conducted on 326,000 buildings under

Dhaka City Corporation. It will kill 90,000 people (earthquake hits at night) or

70,000 (earthquake hits at day). There will be 30,000 million tons of debris

due to the demolition of the buildings with the loss of US$ 6 billion (2010).


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Tsunami and its Effects

A tsunami is a series of water waves caused by the displacement of a large

volume of a water body, typically in an ocean or a large lake. Underwaterstrong earthquakes, volcanic eruption or other submarine landslide usually

cause tsunamis. The last major Pacific-wide tsunami occurred in 1960. Many

other local and regional destructive tsunamis have occurred with more

localized effects.

Tsunami makes a series of water waves with a height of 30 feet or more (100

feet in extreme cases). They can even move an island several hundred feet

away. It brings water into the land and leaves back mud, silt etc. deposited.

Land Slide and its Effects

A land slide or land slip is a geological phenomenon which includes a wide

range of ground movement such as rock falls, deep failure of slopes and

shallow debris flows. It may occur in offshore, coastal and onshore

environments. In Bangladesh, landslides are mostly triggered by heavy

rainfall. However, underlying causes of landslide include deforestation; hill

cutting, unregulated development works etc. Moreover, poverty and

landlessness force poor people to live in the risky hill slopes.

Land slide disrupts road communication by waving away soil sideways or

underneath. It may deposit soil on neighboring areas. Nearby inhabitants may be

covered by soil, entirely or partially, and people are entrapped in their houses.

Fire and its Effects

Fire hazards occur in Bangladesh causing huge loss of lives and property every

year. Although termed as 'fire accident', most fire incidents are far from being

accidental. Indeed, most fires are preventable. Industrial units, particularlygarments industry, produce deadliest of the fires. There are many such

instances of fire in garments industry. In 2004 alone, a total of 7,140 fire

incident occurred which caused damage to property worth more than 200

crores BDT.

The devastating effects of a blaze are extreme. When a property is stolen, still

something remains; when an area is flooded, it washes away all around and still

leaves it back damaged; but when it is blazed, everything is gutted into ashes.


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Infrastructure Collapse

and its Effects

Infrastructure collapse hasturned into a common

phenomenon in Bangladesh

because of non-adherences

to the standards specified by

Bangladesh National

Building Code (BNBC). A

9-story building housing a

garments factory at

Palashbari, Savar, Dhaka

collapsed on April 11,

2005. It was a total

structural failure. On June

28, 2010, a 5-storey building

at Begunbari in the Tejgaon

area of Dhaka city collapsed

on nearby tin-shed houses

leading to the death of some

20 people. On September

18, 2011, the 6-story

building tilted towards

another building at Saat

Matha area in Bogra after a

6.8 magnitude earthquake

struck the country.

The tilted or partially

collapsed structures

endanger the neighboring

one. People are entrapped

inside the buildings, and the

total utility systems are

damaged which may lead to

a fire. Lack of appropriatemodern equipments and

technologies make it

difficult to rescue victims

alive. Again, existing

equipments are not

accessible to the spot.

Table 1: The Disasters with their Effects

Disasters Effects

Flood Withstanding of waterTornado High speed wind

Pre-monsoon rainCyclone &

Storm Surges High speed wind with tidal

waves

Saline water intrusion Mud or silt deposition

Earthquake Collapsing of structures Entrapping live stocks Endangering surroundings by

partially damaged structures

Disruption of total utility system Blocking the access to the spot Causes fire Leads to a heap of debris

Tsunami Saline water intrusion Mud or silt deposition

Land Slide Disruption of communicationsystems

Soil deposition Entrapping live stocks

Fire Everything is gutted into ashesInfrastructure

Collapse Endangering surroundings by

partially damaged structures

Entrapping live stocks Disruption of total utility system Leads to a fire Blocking the access to the spot

EnvironmentalPollution

Polluting environment in theform of carbon & heat emissionClimate

Change Affects peoples health, crop

production, biodiversity etc.

Rise sea water level Root causes of other disasters


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Environmental Pollution and its Effects

Being a developing country, Bangladesh is going for different development

works which lead to use massive engineering works. These plummeted

development works require extensive uses of machines both mechanical and

electrical.

Extensive uses of machines, both mechanical and electrical, pollute the

environment in the form of carbon and heat emission.

Climate Change and its Effects

Impacts of climate change are visible in Bangladesh in the form of extreme

temperature, erratic rainfall, and increased number of massive flood, drought,cyclone, storm surges, salinity intrusion, permanent inundation, river bank

erosion, prevalence of rough weather in the bay etc. The main causes of

climate change include present trends of moving towards urbanization,

enlarged industrialization, environmental pollution etc.

Climate change is the root cause of many other disasters. Extreme temperature

affects people's health, reduce crop production and raise sea water level.

Biodiversity on Sundarban is highly affected due to climate change. About 18

percent households of the Sundarban's impact zone are dependent onSundarban resources (shrimp fry, honey, golpata, shell/crab and medicinal

plant) and are vulnerable to extreme weather and salinity intrusion.

Application of CD Technology: An Assessment

Concept of CD

CD, often known as "Controlled Blasting" is to perform engineering works

based on the works requirements, extent of destruction, degree offragmentation, desired collapsing direction, ambient environment, size and

type of object itself with the help of energy released out of explosive blasting

so that harmful effects (blasting shock wave, air shock wave, ground

touchdown vibration, flying fragments, noise, dust, diffusing smoke etc.) are

reduced to a tolerable limit.

Distribution of Blasting Energy Released

The energy released out of explosive blasting is used for breaking the object ormedium, throwing the particles of object (flying fragments, dust etc.),

producing earthquake waves, air shock waves and sound waves. Few portion

goes unused too i.e. loss. The exact ranges of blasting energy distribution vary

according to the objects and the ambient environment. However, CD is

designed to make maximum use of energy for breaking the object or achieve

desired extent of destruction, and minimum use for other effects.


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Figure 2: Distribution of blasting energy released

2 643 51

Total Blasting Energy Released

1. Breaking the object or medium2. Throwing the particles of object3. Earthquake waves

4. Air shock waves5. Sound waves6. Loss

G= Gravitational Force, W= Withstanding Force

Figure 3: Achieving safe dismantle (at point D)

How to achieve CD

Structures made of any materials withstand because of its strength. There are

mainly two forces that act on them: one refers to the force due to gravity (dead

load and live load of structure, G), and the other is withstanding force (W).

These two forces act against each other. When, withstanding force exceeds its

gravitational force (GW), it

crosses the critical

point. The structure

loses its stability and

gravitational balance,

and thereby the

structure collapses.CD technology takes

the advantages of this

principle which is

known as "Gravity

Unbalance". Here, the

blasting energy is used

to decrease

withstanding force byreducing load bearing

capacity of structural

members in a

sequence. Beyond the

critical point,


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the desired dismantling is ensured. Again, going too far from critical point

will create excessive harmful effects which are not desirable. So, it is better to

cross the critical point (immediate after the point) which will ensure an

effective and efficient dismantling. The load bearing members are not reducedcompletely; rather they are made incapable of bearing the load by buckling.

This phenomenon is known as "Buckling Principle".

Achieving Desired Collapsing Direction

The entire structure is divided into several segments as situation demands and

CD experts design. Blasting energy is released against load bearing members

in a sequence opposite to the direction to be achieved. The sequence is

achieved with time differences by using millisecond detonators.

Non-explosive Demolition

Non-explosive demolition namely Soundless Cracking Agent (SCA) is a

newly invented cracking material (SO3-4.5%, Al2O3-2.4%, Fe2O3-1.1%, CaO-

81.3%, MgO-0.7%, SiO2-8.5%, Ignition loss-1.5%). It goes under hydration

reaction when water is added into it. Then, it condenses, expands and thereby

creates expansion force to break up the objects like concrete, RC structure,

rock, granite, marble quarrying etc.

Harmful Effects and its Reduction to a Tolerable Limit

Demolition creates harmful effects, but CD reduces them to a tolerable limit. If

these are separated with more blast holes and less charges keeping the total

amount same, desired destruction is achieved and least harmful effects are

produced. Heavy protective materials are used to protect the neighboring

structures or objects against flying fragments due to implosion itself. It createsblasting shock wave (earthquake), air shock wave, ground touchdown

vibration (percussion of collapsing structures on the ground), noise, dust,

diffusing smoke etc. Correct designing of blast hole parameters, blasting parts

and specific charges reduce them to a tolerable limit.

Figure 4: Method of conducting Non-explosive Demolition

Non-

explosive

Demolition

materials

Mixing with

water

Poured into

blast holes

Fragmented due

to the effects of

expansion force


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Table 2: Blasting Effects and its Prevention: Few Examples

Blasting Shock Wave (Earthquake)

Consideration of blasting source, neighboring structure and geological conditions intransmission areas.

Dividing entire structure into small segments (more blast holes, less charges) with

time interval blasting.

Preparing anti vibration trench all around the object.

Air Shock Wave

Explosive quantity for one-off blasting should not exceed 20 kg.

Covering doors, windows, ventilations etc. especially made of glass by bramble(bamboo) basketry.

Ground Touchdown Vibration

Reducing the height of falling by designing a cut as low as possible. Putting loose sand or slack layer on the falling ground. Preparing anti vibration trench all around the object. Increasing disintegration of object.

Diffusing Smoke

Can be ignored in most of the cases.Flying Fragments

Adopting coupling charges. Covering surrounding objects with old conveyer belt, vehicle tyre, braiding

basketry, cushion, bamboo springboard, grass bag, steel mesh or steel plate (1 cm

thick), timber or wood plate( over 2 cm thick) etc.

Noise Avoid using skinned charges. Covering blasting object. Considering meteorological conditions like temperature, wind velocity, wind

direction, humidity etc.

Dust Covering the object with water bag curtain. Spray water (sprinkling) from ground or helicopter. Water seal blasting (10 kg water with 100 gm explosive inside).


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Overwhelming Advantages of CD over other Means

Time and Safety Dismantling of any structures, manually or mechanically,

is being carried out from top to bottom, and the entire process takes a longtime. As the dismantling goes on, it becomes weak and collapses at certain

time. Uncertainty in collapsing time and direction makes it easier to commit

accidents. CD ensures the collapsing time and direction, and thereby provides

utmost safety to the working staffs, structure itself and the ambient

environment.

Cost CD technology reduces the cost about 40% -60% than that of manual or

mechanical means as the demolition time and labor forces are shortened to a

great extent.

Complexity The complicated structures with height, strength, density and

diversification of structural forms (common frame, frame-shear wall, tube

structure, tube bundle, sleeve tube etc.) need high technology, skilled operators

and more spaces to dismantle them efficiently. CD can be an effective

alternative to handle different materials and work in a complex situation; even

under water.

Towering Structure Dismantling of towering structure (great ratio ofheight to sectional breadth) is simply impossible by manual or mechanical

means. A partially damaged chimney, water tower, TV tower, radio tower,

parachute tower etc. endanger surrounding environment, and entail immediate

safe dismantling. Here, CD technology is a very efficient and effective means

to dismantle them in position or at a particular direction.

Effectiveness and Efficiency The short span of time between early warning

and occurrence of cyclone and storm surges will not allow manual ormechanical means to complete the work. CD is very effective and efficient in

this situation.

Environmental Friendly The process of dismantling structure creates

harmful effects and debris out of its fragmented parts. CD can contribute

towards a non-polluted dismantling process by reducing harmful effects and

recycling of wastes produced. Even, if the structures are contaminated with

arsenic, cyanide, lead, asbestos or other regulated materials, CD technology

brings them down safely. Extensive uses of machines in development workspollute the environment in the form of heat and carbon emission. Use of CD in

civil engineering works can reduce them to a great extent.


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The Ways CD Reduces Disaster Effects: An Overview

Removal of Standing Water

Creating Outlets in Water Retaining Structures The basin layout and

outlet capacity of existing traditional water control structures like sluice gate,

spill way etc. may not be sufficient to drain out too much water within a short

time. An out let of a dam or embankment may drain out water quickly, and

save important inhabitants, structures, large tributaries, basin etc. A particular

portion of water retaining structure like dam, embankment etc. is blown off

with explosive, and water is drained out towards a suitable and less important

area. On May 3, 2011, a historic flooding in the Mississippi river, U.S.A was

caused by significant and persistent spring rains combined with winter snow

melt. The river and tributaries continued to rise, reaching record crests.

Portions of Missouri, Illinois, Kentucky, Tennessee, and Arkansas were under

water, with more to come. As a bulge of river water made its way downstream,

levees were stressed and rivers that emptied into the Mississippi had no outlet,

backing up and flooding even more land. The bulge would reach the Delta, and

millions of acres were threatened. Pressure on levees led the U.S.A Army

Corps of Engineers to blast a two-mile hole in a Mississippi river levee to

relieve water pressure that was endangering Cairo, Ill. It inundated 130,000

acres of farmland while saving the town.

Source: Justin Pummell (DREE 2011); Jeff Roberson/AP

Figure 5: (a) Sketch of water control structures on Mississippi river

(Justin Pummell); (b) The Mississippi river basin after flood (Jeff

Roberson/AP); (c) The U.S.A Army Corps of Engineers blasted a two-milehole in a Mississippi river levee to relieve water pressure that was

endangering Cairo, Ill. (Jeff Roberson/AP).


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Table 3: Suggested Model of CD to Reduce Disaster Effects

Ways to Reduce Disaster

Effects

CD Operation

Standing water removal

Creating an outlet in water

retaining structures Blowing off a portion of dam, embankment etc.

Clearance of drainage outlet Fragmentation and removal of debris Removal of sand or silt form drainage outlet

Plummeting water retaining

capacity Excavation of bed level sand or silt

Controlling saline water

intrusion

Blocking of saline water

intrusion Displacement of earth, sand, silt etc. into canal or river

to block the outlets

Construction of a dam all along the coast lineRemoval of saline water

intrusion Freeing all possible outlets as enumerated in case of

Standing water removal

Safe dismantling of

collapsed structures

Safe dismantling of partially collapsed structures. Use of non-explosive demolition as situation permits

Rescue entrapped people Creating few openings (holes) through concrete, earth,bricks, or even rocks

Effective use of non-explosive demolitionRemoval of earth, mud or

silt deposition Removal of deposited mud or silt by blasting Effective use of non-explosive demolition

Debris clearance, access to

incident spot and

reopening the routes

Fragmentation and removal of tree trunk, pylons, debrisetc.

Making diversion of underground routes Effective use of non-explosive demolition

Mass area foundation Removal of mass area foundation Effective use of non-explosive demolition

Environmental friendly

works Extensive use of CD technology instead of mechanical

means in civil engineering works reduces carbon and

heat emission

Fighting Fires Creating a clear line ahead of fire progress by blasting. Blasting can extinguish fire by itself


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Clearance of Drainage Outlet Under water debris at outlet may block

draining out of excess standing water. CD is very effective to remove them and

facilitate quick drain out. Simply, under water blasting in the debris stacked at

outlet will release them, and water flow will take them away. Another reason ofwater logging is the shallow depth at outlet. Removal of sand or silt from bed

level at outlet increases its depth and thereby it drains out more water shortly.

Plummeting Water Retaining Capacity Lowering the bed level of feeder

canal, river or basin increases water retaining capacity. The blasting of ditches

on ground is often resorted to when mechanical excavation is impossible or

impractical i.e. in swamps, forests etc. This method is described as 'Blasting

Ditches' by Stig O Olofsson (1988). Under water CD removes sand or silt veryeffectively, increases the depth and thus water retaining capacity is plummeted.

Saline Water Intrusion

In case of saline water intrusion, CD can contribute in two ways: one is to

block all inlets before the occurrence; and the other is opposite of it (freeing all

possible outlets) immediate after the occurrence.

Blocking of Saline Water Intrusion The span of time between early warning

and occurrence of cyclone and storm surges is very short. Available watercontrol structures are utmost important to block saline water intrusion. Lack of

them may entail the use of CD to block the inlets. CD can displace soil, loose or

hard, into the canal or river and block inlets very shortly. Even, a dam all along

the coast line of likely affected area may be constructed in the same manner.

Removal of Saline Water Intrusion Right after cyclone and storm surges

hit the land, all possible drainage outlets are to be made free to drain the saline

water out along with mud or silt following the methods as enumerated in case

of removal of standing water.

Safe Dismantling of Partially Collapsed Structures

Partially collapsed structures endanger themselves, the occupants and the

property they possess. More importantly, they endanger ambient environment

untill they are dismantled safely. These partially collapsed structures are

dismantled using CD technology. Manual or mechanical dismantling means

are time consuming and impractical, especially in case of the towering

structures. The structures are dismantled at the place where there is no enough

space in and around (In-Place Collapse); in a particular direction where there is

an open space (Directional Collapse); in a particular direction with folding of

entire structure where there is space but not enough to accommodate it

(Folding Collapse); and in one or more directions in case of a large area

structure (Continuous Collapse).


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High Rise On March 28, 2009, Meize Mansion, Tianjin, China was

dismantled safely using CD technology. The length and width of the structure

were 32.7 m and 32.6 m respectively. Its overall floor area was 14916 m2and

its total height was 57.95 m. It was a core tube-frame structure, with 15 storiesabove ground and one basement. The elevator raise, floor, pillars and the shear

walls were constructed in place as integrity. The general blasting environmental

conditions were complicated; the Tiantie Hotel at west (31.9 m away), under

construction tunnel at north (10.6 m away), an open area at south (26.1 m

away) and a crossing of Jianguo road and Minsheng road at east (12.9 m away).

It took 6 seconds only to turn the high rise into a lump. It was a complete

success as CD technology is concerned. The high rise collapsed into a desired

direction without hurting anybody.

Figure 6: (a) Meize Mansion, Tianjin, China; (b) Safe dismantling of

Meize Mansion; (c) & (d) Right after the safe dismantling.

Towering Structures On May 6, 2009, according to the blueprint of

Shanghai Yaopi Glass Co. Ltd., China, two weighing workshops and onechimney were needed to be dismantled. The workshops stood at 2 m away

from each other. One of the workshops was 20.5 m long, 18 m wide and 40 m

high, while the other was 20.5 m long, 12.5 m wide and 36 m high. Five floors

of the southern workshop and 4 floors of the northern one were of RC

structure, while both of their upper structures were of steel. The chimney was

situated to south-east of the workshops, 22 m away, which was RC structure,

90 m high, wall thickness 0.8 m, bottom diameter 6.78 m. These two blasting

went simultaneously. One fell towards east and the other towards west. Itachieved desired direction with utmost safety.


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Figure 7: (a) Yaopi Glass Co. Ltd., Shanghai, China; (b) Yaopi Glass Co.

Ltd. & Chimney; (c) Preparation for dismantling; (d) Right after the safe

dismantling

Bridges Between 1978 and 1988, West Germany demolished hundreds of

bridges applying CD technology. The demolition of the burning oil derrick

'Abkantun 91,' in the Gulf of Mexico, 90 kilometers from the shores of

Campeche, Mexico was beautifully executed by CDI.

Earthquake The 2008 Sichuan earthquake or the Great Sichuan Earthquake

was a deadly earthquake that measured at 8.0 (Richter scale) occurred on May

12, 2008 in Sichuan province of China, killing an estimated 68,000 people. CDexperts went to the spot, dismantled and removed those partially damaged

structures safely. On February 22, 2011, a 6.3 (Richter scale) magnitude

earthquake hit New Zealand. U.S.A provided New Zealand with technical

expertise (CD technology) in the stabilization of heavily damaged mid and

high rise structures in the Christchurch central Business District.

Non-Explosive Demolition Non-explosive demolition may be adopted to

dismantle partially collapsed structure where there are enough spaces availableand directional collapse is not required.

Rescue Entrapped People

People may be entrapped under buildings, tunnels, flyovers, subways etc. due to

collapsing of structures. The dire situation will ask for evacuation of the alive

people underneath or even the dead bodies very urgently. There are hardly any

methods, manual or mechanical, to be effective under this situation.

Experimental methods using layers, micro waves, and high water pressure jetshave been tried. CD is executed with small charges, causing little damage and is

well controlled. The blasting of holes though earth, brick, concrete or even rock

is possible with the use of explosive. Stig O Olofsson (1988) has referred it to

'Pole hole blasting'. On March 4, 1977, Romania experienced an earthquake.

After the earthquake, the blasting operators from Australia carried out controlled

blasting to bring out a buried man under about 40 cm RCC slab, safely.


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Non-explosive demolition can break up brick walls, concrete slabs or rocks

and make openings as needed. It is completely safe as the process does not

produce flying fragments and other hazardous effects to hit the entrapped

people or even dead bodies. It is used only in the occasion when manual,mechanical or even conventional CD methods are not effective and efficient to

handle the situation.

Removal of Earth, Mud or Silt Deposition

Blasting operation may be used in land clearance (mud or silt deposition)

including the removal of debris, reduction of rocky outcrops etc. It is referred

to as 'Agricultural Blasting' as it is used in agricultural field preparation.

Simply, a blasting of earth, mud or silt deposition can displace them as desired.The loosening of earth, especially in hard ground will help the removal work

of heavy earth movers.

Debris Removal, Making an Access to the Incident Spot and Reopening

the Routes

Blasting of concrete is often carried out in connection with the demolition of

buildings in the cleaning up of any collapsed building site where heavy plants

are not accessible. Reopening of routes becomes very important to reach thevictims. A correct quantity of charge with proper placement in the right place

can uproot a tree stump of any size. Concrete, tree trunk, pylon or debris can

be fragmented using explosives followed by manual or mechanical removal.

Applied CD technology along with earth moving equipments can remove earth

or debris from blocked portion of underground route (tunnels, subways etc.);

or construct underground diversion route. Blasting energy helps to loosen the

earth, concrete or rock in a hard ground. Use of non-explosive demolition is

very effective and efficient here as directional collapse is not needed. It canfragment them to a desired extent.

Mass Area Foundation

Earthquake may cause damage to concrete foundations, helipads, landing

strips, air ports, sea ports etc. These large structures may receive numerous

cracks, followed by undulations. And, these situations lead them to cease

operations. CD is very effective in demolishing or dismantling large area

foundation. In 1976, Engineering Corps of China used CD to demolish old RChouse of post office with an area of 12000 m2near Tiananmen Square. Large

workshop of wangling pavilion power plant, one time dismantling area reached

19,400 m2. The use of Non-explosive demolition is suitable here too.


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Moving towards Environmental Friendly Works

Blasting in civil engineering works includes trenching, foundation excavations,

road way cutting, tunneling, pile head excavation, pile head breaking, and soon. Today's world is performing many colossal engineering works by CD

technology. This reduces extensive use of mechanical or electrical machines,

thus reduces carbon and heat emission.

Conclusion

The very geographical location, landscape, and other factors have rendered

Bangladesh a disaster prone country. Human induced activities add a new

dimension. Recent advancement cannot eradicate them; but prediction or

providing early warnings regarding their occurrences is possible. Even, the

developed countries become helpless with the devastating effects of natural

disasters and human induced activities. The extent of effects and degree ofdamages caused due to disasters are quite high. The manual or mechanical

means to handle them may be effective to some extent, but will not be efficient

completely. Again, the complexity of situation and precarious environment

may entail special methods to be adopted to go out of the crisis. There are

many ways and methods to get the engineering works done. Whatever methods

are used, the main driving force is the energy to perform the works. CD is one

of the effective and efficient means where blasting energy released out of

explosion is used. It ensures the completion of works, reduces harmful effectsand takes care of ambient environment. The knowledge on the nature of

disasters with the extents of their effects lead to a physical preparation and

mental set up to mitigate the same. The overwhelming advantages and

examples of widely practiced CD technologies lead towards the adoption of

the same in Bangladesh.

Making a clear line by blasting of

objects ahead of the fire progressed

Densely populated

area

Fighting the Fires

Fires in a

concentrated area or

forest become

unmanageable to the

fire fighters. Blasting

of the objects and

making a clear line

ahead of the fire

progressed, followed by removal of same will obviously discontinue the fire.

CD technology can extinguish the fires by itself.

Figure 8: Fighting a fire with Blasting


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Policy Recommendations

After a ruthless study on the nature of disaster and its effects, the ways to

reduce disaster effects are identified in the context of Bangladesh and a modelof CD is suggested. Following suggestions are made to make the applied CD

technology more efficient and effective:

CD technology should be introduced in "Disaster Management

Institutions in Bangladesh" at all levels for the effective contributions to

the National Plan for Disaster Management.

Advanced training both at home and abroad on CD technology should

be arranged to grow more expertise in regards to disaster effectsreduction.

All necessary materials, machines, equipments etc. which are not

available in Bangladesh right now but very much essential for CD

operation, should be procured.

Disaster management authority should make an effort to allow CD

experts to practice widely on the subject.

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