CONTROLLED BLASTING FOR DEMOLITION

PRESENTED BYM.KARY JAKINS ( Reg no:113013413007 )M.E. STRUCTURAL ENGINEERINGVEL TECH HIGH TECH Dr RANGARAJAN Dr SAKUNTALA

ENGINEERING COLLEGE, CHENNAI.

Demolition

• The demolition is an act of destroying the structure

or building due to various reasons, often in order to build

something else in that place.

• In the controlled demolition industry, building

implosion is the strategic placing of explosive material and

timing of its detonation so that a structure collapses on

itself in a matter of seconds.

•  Building implosion also includes the controlled

demolition of other structures, such

as bridges, smokestacks, towers, and tunnels.

• Controlled blasting is also used in mine and ore industry

Necessity of demolition

• The structure has achieved its service life period.

• When the structure has lost its stability. To built new

structure in the existing place.

• Structural changes required & development of city.

• Structural failure where repair methods not possible.

• When the structure has lost its durability.

Different types of demolition.

1. Demolition by hand.

2. Pulling down by rope.

3. Mechanical demolition.

4. Demolition by deliberate collapse.

5. Explosives.

Demolition by hand.

This method is carryout by using:

1. hammers.

2. long chaises.

3. pneumatic drills.

4. hand and power saw. Hand demolition is not a quick method, because only hand

tools are used.

Pulling down by rope

1. Cables and wire ropes are fixed to key structural members, then pulled down by tractors or winches.

2. This method can be used for timber-framed buildings, bridges, brick masonry and steel chimneys.

Mechanical demolition.

1. Demolition with ball (min 0.5 ton).

2. Demolition by pusher arm.(Hydraulically-operated excavators and loaders).

Demolition by deliberate collapse

This method requires engineering expertise to decide which key structural members should be cut or removed to cause a collapse.

This method is best suited for bridges, silos, chimneys and structures on isolated or heavily controlled and secure sites.

Explosives.

This is a method to safely and quickly demolish structures where significant hazards are posed to persons through exposure during the demolition process.

Most structures, except timber-framed and brick structures, can be demolished this way. 

This method can reduce both cost and time to bring dangerous multi-storey structures to ground in comparison to conventional demolition methods.

Cont..

Types of demolition methods depends upon various factors such as site condition, type of structures, age of building,height of building & economy.

Controlled demolition of building is necessary to ensure safety.

So, explosive demolition is the preferable method for safety and efficiently demolishing the larger buildings……….

Precautions to be taken before demolition

Electric supply fully disconnected from building. Plumbing, fitting works, should be removed. Doors ,Glasses in windows and other glass frames

should be removed before demolition. Balconies, cantilever masonry projections should be

cut down. Any metal ladder or staircase should be inspected

before use. Projected nails and screws should be removed. Keep the public at a safe distance - a minimum of

200 meters from the blast site. Plan and inform all employees of the evacuation

plan. Use mats and small charges to stop flying debris

Damage assessment

Precautions Over Break – Damage

Reduce ground vibrations

Prevent contamination of soil, groundwater and air

Reduce noise pollution

Prevent damage to neighbouring structures especially foundations

Procedure for Damage assessment1. Physical inspection of damaged structures.

2. Preparation and documenting the damages.

3. Collection of samples and carryout tests in-situ or in laboratory.

4. Studying the documents including the structural aspects.

5. Estimation of load acting on the structure.

6. Estimation of environmental effects and soil interaction.

7. Diagnosis.

8. Taking preventive steps not to cause further damage.

9. Retrospective analysis to get the diagnosis.

10. Assessment of structural adequacy.

11. Remedial measures to strength and repair the structure

12. Load test to study the behaviour.

13. Choise of course of action.

Physical inspection

Material test

Study of documents

Estimate loads & environmental

effects

diagnosis

Retrospective analysis

Diagnosis confirmed

Assessment of structural adequacy

Estimation of

future useLoad test

Choice of course of action

no