Jagvir Goyal

Introduction:   Demolition  is  one  area  India  has  never  bothered  to  concentrate  upon.  Ours  being  a  ‘developing  country’,  emphasis  has  rather  been  on  development.  We  develop  cold  feet  when  it  comes  to  demolishing  some  structure.  There  exist  innumerable  old  and  unsafe  buildings;  narrow,  half-a-lane  bridges  that  need  to  be  demolished  to  give  way  to  new  multi-storeyed  buildings;  wide  and  safe  flyovers.  Traffic  is  increasing  day  by  day  and  business  is  on  the  rise  thus  demanding  more  and  more  buildings,  offices,  commercial  buildings,  dwelling  units  and  a  well  connected  and  capable  road-transport-network.  All  this  is  possible  only  if  the old  and  outlived  structures  are  removed  and  land  is  freed  for  the  new  ones  to  come  up. 

The Need: In  India,  demolition  is  avoided  as  if  it  is  something  inauspicious,  involving  wasteful  expenditure.  Another  factor  is  our  crude  method  of  demolition.  If  we  are  asked  to  demolish  an  old  bridge  or  a  building,  we  put  a  large  labour  force  armed  with  chisels  and  hammers  on  it.  Otherwise  we  try  to  ram  a  bull-dozer  into  the  structure.  At  the  most  we  deploy  some  pneumatic  jack-hammers  to  dismantle  the  RCC  or  brick-work.  There  exist  no  planned  methods  to  execute  ‘demolition’.                                                 Now  is  the  time  that  India  develops  demolition equipment and  technology  suitable  to  Indian  conditions.  For  this,  our  structures  are  to  be  categorized  and our  requirements  are  to  be  defined.  A  blind  adoption  of  the  techniques  being  used  in  foreign  countries  may  not  be  conducive  to  Indian  layout and environment. 

Indian  Structures:  On  a  broader  scale  and  from  demolition  point  of  view, the  Indian  structures  can  be  divided  into  following  categories:  1.      Tall  chimneys  of  power  plants,  large  sized  Natural  draught  cooling  towers, high rise industrial structures.2.      Multi-storeyed  buildings.3.      Heavily  reinforced  bridges  and  buildings.4.      Ordinary  buildings, houses,  brick-structures  etc. 

Indian Requirements:  Thinking  of  the  requirements  that  the  demolition  technology  should  fulfill,  the  following  shall  form  an  ideal  list: 1.      Quicker  demolition.2.      Quieter  demolition.3.      Cheaper  demolition.4.      Environment-friendly  demolition.5.      Demolition  causing  least  disturbance  in  the  neighborhood.Therefore,  whenever  a  structure  is  to  be  demolished,  it  must  be  seen  that  the  method  adopted  is  such  that  takes  minimum  time,  produces  least  level  noise,  causes  no  pollution  beyond  permissible  limits,  does  not  disturb  the  activity  or  living  in  the  neighborhood  and  proves  cheaper  also.  In  foreign  countries,  regulations  exist  to  control  dust  and  noise  pollution  during  demolition.  Such  regulations  can  be  devised  for  our  country  also  even  though  most  of  the demolitions in India  will  fall  within  the  ambit  of  Government  departments  only. 

Physical  survey:  It  is  essential  to  survey  the  surroundings of  the  structure  to  be  demolished.  The  surroundings  will  decide  whether  a  structure  is  to  be  toppled  or  made  to  collapse  or  shattered  or  imploded  or  exploded.  The  position  of  the  water-supply  lines,  telephone  cables  and  electricity  wires  is  also  to  be  checked.  It  has  to  be  ensured  that  the  supplies  to  the  adjacent  buildings  are  not  disturbed.  Whenever  explosion-demolition  technology  is  to  be  used,  it  is  to  be  seen  that  the  computers  and  the  equipment  installed  in  the  near-by  buildings  are  not  affected  by  the  vibrations  produced  by  the  explosions.  If  a  demolition  involves  rise  of  clouds  of  dust,  the  ducts  of  AC  systems  in  the  adjacent  buildings  are  to  be  sealed  against  entry  of  dust  in  them.  Overall  approach  has  to  be  to  cause  least  disturbance  to  the  surroundings.                                           The  construction  drawings  of  the  structure  to  be  dismantled  will  not  be  available  as  it  may  be  over  40  to  50  years  since  the  time  that  structure  was  built.  Therefore  core  tests  may  have to be  done  to  have  an  idea  of  the  concrete  strength  and  density  of  reinforcement.  The  position  of  the  expansion  joints  in  the  building  are  also  be  assessed  as  it  will  help  in  planning  the  demolition  of  the  building. 

Technology  abroad:  Explosive  demolition  technology  has  become  most  popular  in  foreign  countries.  High-rise  chimneys  and  massive  cooling  towers  are  made  to  collapse  through  telescopic  technique  by  placing  explosives  in  such  a  manner  that  an  almost  vertical  collapse  occurs.  Under  this  technique,  large  compressive  stresses  are  produced  at  the  base  of  the  structure  and  it  descends  in  a  continuous  manner  like  a  house  of  cards.  While  the  explosives  cause  the  initial  collapse,  further  fragmentation  is  caused  by  gravity  only.  Often  such  demolitions  provide  a  spectacular  show  making  people  wonder  at  the  advance  of  technology.  Technically, this is  just  a  result  of  following  the  laid  set  of  guidelines  and carrying out of demolition under  expert  supervision.                                        Wherever  environmental  regulations  impose  restrictions  over  use  of  explosives,  chemical  techniques  are  being  applied.  These  techniques  also  are  highly  effective.  Alloy  steel  cartridges  filled  with  liquid  carbon  dioxide  and  some  chemical  igniting  agent  are  fixed  in  position  and  then  detonated  from  a  safe  distance.  Expanding  carbon  dioxide  gas  breaks  up  steel  cartridge  and  attacks  the  surrounding  material  with  a  cold  heaving  force.  This  technique  is  capable  of  breaking  very  hard  materials.                                        Water  bursting  and  water  jetting  are  other  techniques  being  used.  Special  methods  are  being  devised  to  dismantle  pre-stressed  concrete  and  post-tensioned  concrete  structures. 

Lessons  for  India:  Indian  conditions  are  not  fully  ripe  to  adopt  explosive  demolition  technology.  Dense  population,  haphazard    growth,  non-existence  of  any  bye-laws  or  regulations  and  our  casual  approach  makes  use  of  explosives  a  risky  affair  for  us. As our country is constantly facing terrorists’ threats, use of explosives for demolition may not be permitted by the authorities. Demolition companies may themselves remain away from using explosives to avoid inviting any law and order problem. The  complex  and  dangerous  business  of  use  of  explosives  needs  a  very  strict  set  of  guidelines  to  be  followed  in  an  explicit  manner,  an  expert  supervision  and  a  comprehensive  planning  exercise  to  determine  the  sequence  of  removal  of  components  of  the  structure  and  the  placement  of  the  charges.  Minutest  details  are  to  be  worked  out.  For  example,  the  rough  end  of  a  steel  bar  exposed  while  making  holes  can  cut  the  detonating  cord  or  detonator  lead  wires.  A  record  of  the  vibrations  and  air blasts  produced  has  to  be  kept  and  instruments  capable  of  making  these  measurements  are to  be  installed.  Private  companies  who  promise  to  develop  fool-proof  methodology  for  explosive  demolition  should in fact  be  extended  full  co-operation  and  assistance  by  the  Government so that India too could adopt this technology on a large scale. 

Hydro-demolition: This  is  another  area  India  should  concentrate  upon.  Heavy  duty  hydraulic  hammers  of  30  to  50  tonne  class  developed  by  Krupp  industries  can  operate  at  250  to  450  blows  per  minute  and  can  work  underwater  also.  Other  leading  companies  of  the  world  such  as  Labounty  of  USA  whose  universal  processor  can  rotate  at  360 degrees  and  can  demolish  concrete  as  well  as  steel  by  fixing  alternative  jaws,  Brokk  of  Sweden  who  is  known  for  noiseless  concrete  demolition,  Conjet  of  Sweden  that  can  cut  concrete  and  asphalt  by  water-jet  system  at  twice  the  speed  of  sound,  NPK  of  Japan  that  provides  world  class  hydraulic  rammers  and  Atlas  Copco  of  Sweden  who  is  master  of  rock-drilling  technology  should  be invited to  collaborate  with  Indian  firms  till  the  time  a  switch-over  of  technology  takes  place.  

The Breakers: Dismantling masonry is easy. Chisel and hammer work there and manual work is productive. Real problem is faced by the engineers when it comes to breaking RCC or even plain concrete. Chisel and hammer give way. No significant progress is achieved after a day’s work. Even sledge hammer doesn’t produce desirable results. Many types of breakers have now been developed and any sort of dismantling problem can be handled without much of manual labour. Weighing as little as 20 kg and as much as 13 tonnes, these breakers can do all types of quarrying, demolition, tunneling, trenching and foundation breaking. The range available is expanding day by day as the competition among the manufacturers gets tougher.

Types of the Breakers: Based on the type of power supply, these breakers are either electricity driven, hydraulic or pneumatic. Depending upon the job to be done, the breaker chosen may be light, medium or heavy. For use, these breakers are to be mounted on some equipment such as backhoes, excavators etc. Here, these equipments are called Carriers. Barring lightweight breakers which can be hand-held, it is not possible to operate these breakers directly as the vibrations transmitted to the operator are very strong and unbearable. There is hardly any manufacturer in the world who makes both breakers as well as carriers. Breakers produced are therefore versatile enough to suit any type of carriers made by different manufacturers. 

                                    Hand held breakers have T-shaped handles and are applied vertically to the structure to be broken. These can offer controlled breaking and chipping action and a particular area of a big structure can be concentrated upon. Their blows to the structure range between 900 to 3000 blows per minute. As the operator has to tolerate their vibrations, the manufacturers are now concentrating most on minimizing these vibrations. Even when mounted on carriers, it is difficult to isolate the operator from the breaker-vibrations. International law has now been enacted to limit and fix the maximum amount of vibrations per day transmitted to operators. Similarly, control limits for noise produced have also been defined.  

Features of the Breakers: A breaker’s weight indicates its power. Heavier the breaker, more powerful it is in demolition. A 30 kg hydraulic breaker can break RCC panels, concrete roads, foundations and even high strength airport runways. Different types of bits and tools can be installed on these breakers. These may be twisting type for drilling holes, flat chisels for breaking or hammer type for demolition. Some desirable features of breakers are as under:

Indian Scene: Though most of these highly versatile breakers of big international companies are available in India, Indian manufacturers have taken up manufacturing of light weight breakers suitable for breaking concrete, roads, rocks, asphalt surfaces, trimming of RCC pile heads etc. A number of such manufacturers provide breakers at highly competitive rates. For larger jobs however, only imported breakers fulfill the requirements.