Construction Safety > Chapter - 6 > Topic- Safety In Demolition > Subtopic- Planning & Permit sequence of demolition ,Precautions to be taken for and during demolition

What are the safety measures to be taken during demolition work....Hazards and their control measures related to the demolition.

What is Demolition? 

The word demolition means destruction, breaking down or removal. Demolition of building is the process of dismantling or destroying of a structure after its life of serviceability by pre-planned and controlled methods. 

General reasons for Demolition of the Building or Structures-

1) Design life of building/ structure is over

2) Building /Structure is unsafe for use

3) Replacement of Old structure 

4) Structural Damage or loss of stability of the structure 

5) Demolition of small structure to build bigger one

6) Unsafe for surrounding areas 

What are the types of Demolition? 

There are two types of demolition methods used for buildings and structures - 

1) Non-explosive demolition

2) Explosive demolition 

1) Non Explosive- That means the demolition of a structure done with some equipment without the use of any   explosive. Different equipment’s used for the demolition activity are -

a) Sledge Hammer

b) Excavators and Bulldozers

c) Wrecking Balls

d) High Reach Excavators

2) Explosive demolition-  Implosion is the process of demolition of a building using explosives. If the supports of the building are removed, the structure collapses. Using implosion technique, the main supports of the buildings such as column’s, beams and slab are fixed with explosives. When these explosives are detonated, the column collapse and then structure collapse. 

Steps Involved during Demolition of the Structural Building- 

1) Surveying

2) Removal of hazardous materials

3) Preparation of plan

4) Safety measures

1) Surveying- 

Surveying means study of different parameters of the structure and its surroundings. There are two types of surveying are mainly conducted. They are

A) Building surveying- Material used, use of building , adjacent effect on surrounded area, current drainage system , sensitivity of neighborhood in terms of dust ,noise , pollution ,vibration ,traffic impact.  

B) Structural surveying-  Condition of the building ,basements , column pillars, method of construction , design of the structure 

2) Hazards in Demolition- 

1. Falls From Height Or On The Same Level.
2. Falling Debris
3. Premature Collapse Of The Structure Being Demolished
4. Dust And Fumes
5. The Silting Up Of Drainage Systems By Dust
6. The Problems Arising From Spilt Fuel Oils
7. Manual Handling
8. Presence Of Asbestos And Other Hazardous Substances
9. Noise And Vibration From Heavy Plant And Equipment
10. Electric Shock
11. Fires And Explosions From The Use Of Flammable And Explosive Substances
12. Smoke From Burning Waste Timber And Materials
13. Pneumatic Drills And Power Tools
14. The Existence Of Services, Such As Electricity, Gas, And Water
15. Plant And Vehicles Overturning

3) Preparation of Demolition Plan for Structures-

A detailed demolition plan is made which illustrates the different process involved and they are:

• The location of the building to be demolished.
• The distances from the building to be demolished to its adjacent buildings, streets, structures and significant street furniture.
• The structural support systems of the building.
• A plan showing the procedure for the demolition of the building; detailed sequence of demolishing structural members; and the method of demolition to be adopted.
• A plan showing all precautionary measures for the protection of the public including hoardings, covered walkways, catch platforms, catch fans, scaffolding, protective screens and safety nets.
• Method of handling demolished building debris.
• Time required for the complete demolition process etc. 

As per BOCW Act 1998 Chapter XII Rules 108 to 118 Precautions needs to be taken for demolition activity. 

4) Precautions  for demolition of Building / Structure- 

Safety Measures in demolition of Building :

1) Workers should not be deployed at different levels unless adequate precautions are taken to ensure safety of them. 

2) Demolition work should begin at the top of the structure and proceed downwards. 

3) Masonry concrete and other dismantled materials should not be allowed to

accumulate in quantities which may endanger the stability of any floor or structural support.

4) Part of the structures, where necessary should be adequately shored, braced or otherwise supported.

5) If the structure is to be demolished by explosives, all safety measures pertaining to explosives such as transport, storage, handling, loading firing etc. should be strictly adhered.

6) Foundation walls serving as retaining walls to support of adjoining structures should not be demolish until the adjoining structure have been under pinned or braced or earth supported by sheet pilling. 

7) Stairs with hand railing should be kept in place as long as practicable to provide access and egress.

8) If the work of demolition is continued in night, all passageways, stairs and other parts of the structure where the workers have to pass and also to work should be adequately lit.

9) Workers should wear strictly safety belts, safety belts, safety helmets and hand glove.

10) If the demolition is carried out by machines such as power shovels, bulldozers etc. the safety measures relevant to operation and use of such machines should be adhered to.

 

11) If swinging weight such as ball is used for demolition, a safety zone having a width of

at least 1.50 times the height of the building or structure should be maintained. 

12) Scaffolds used for demolition operations should be independent of the structure to be demolished. 

13) If ladders are used for demolition, only travelling mechanical ladders should be used. 

14) The hoists or chutes, whenever it is practicable, should be used to lower the materials. Materials chutes should have a gate at the bottom with suitable means for regulating the flow of materials. 

Safety measures in demolition of structural steel works:

1) The steel structures should be demolished from top tier by tier.

2) Removing the various members of the steel structures should be done in a planned manner.

3) All precautions should be taken to prevent danger from any sudden twist, spring or collapse of steel parts/work when it is cut or released. 

4)Structural steel parts should be carefully lowered and not dropped from a height.

5) Safety precautions of gas cutting of the steel members should be adhered to. 

Safety measures in demolition of tall chimneys, minars, pylons etc.

1) Tall chimneys, minars, pylons, etc., should not be demolished by overturning or blasting unless a protected area of an adequate dimension in which the chimney or the structure can fall safely.

2) If the demolition of the tall structures are done by , blasting with explosives, it should be done with the services of specialized engineers. The entire operation should be under his supervision and control.

Safety measures in demolition of Industrial Structures:

1)The Safety measures in removing heavy and bulky machinery, plant and equipment should be observed in addition to some of the relevant safety measures already stated. 

2)If the industrial Structure such as a nuclear power station the services of the specialist expert in the field of radio-activity and radiation should be utilized. 

References: 

BOCW Act 1998 

HSEBLOGS.COM 

Fundamentals of Industrial Safety and Health By - K.U.Mistry 

WWW.Gharpedia.com 

AskEHS.com