For diploma students

1. S.T.B.S COLLEGE OF DIPLOMA ENGINEERING,
SURAT
DEMOLITION
AND
DISMANTLING TECHNIQUES
PREPARED BY:- N.J.PATEL

2. DEMOLITION:
“Demolition means dismantling, razing, destroying
or wrecking any building or structure or any part of it by
pre-planned and controlled methods.”

3. NECESSITY OF DEMOLITION:
 When the building structure is very old and not
desirable to take the load any more, it is necessary to
dismantle the structure. A structure should be
dismantled after its design service life is over.
 When the building structure is very old.
 If any part of building has become weak.
 If any internal changes are to be done.
 If design life of a building is over.
 When a building is severely damaged due to earthquake
or any other reason.

4. DEMOLITION SURVEY:
 The demolition survey includes:
1. Building survey:- Drawing records, material survey,
removal of hazardous material, photographs of
building, surrounding building detail, type of building
2. Structural survey:- Drawing records, special structure,
behaviour of structure, structural support system
`

5. DEMOLITION PLAN:-
 Based on demolition survey, a plan is prepared.
 This demolition plan is produced with the application for
approval of demolition to the local authority.
 A demolition plan should include the following:-
• A plan showing the location of building to be
demolished.
• Building height & structural system.
• Extent of damage to the building.
• Existing structures and facilities in the vicinity.
• Layout plan
• Proposed method of demolition.

6. • Proposed shoring and precautionary measures for
adjacent building.
• Safety measures to be taken.
• Proposed sequence of demolition steps.
• Details of equipments used.
• A plan for handling and disposal of debris.
• Proposed arrangement for site supervision.

7. FACTORS AFFECTING SELECTION OF
DEMOLITION METHOD:-
 FACTORS:-
• Type of structure
• Size of structure
• Available time period
• Location of structure
• Limitation of noise, dust and vibration
• Skill of workers
• Safety
• Availability of equipment
• Adjacent structures
• Behaviour of structure

8. DEMOLITION TECHNIQUES:
The various techniques of demolition are as follows:
Demolition techniques:
Non-engineering demolition Engineering demolition
Manual demolition (a) mechanical method
-Wrecking ball method
-Pusher arm technique
-Thermic lance techniques
-Non-explosive demolition
-Concrete sawing method
-Deliberate collapse method
-Pressure jetting method
-Bursting
(b) Implosion techniques
(c) Deconstruction technique

9. 1-MANUAL (HAND) DEMOLITION:
 Suitable for demolition of small building in a densely
populated area.
 Use equipment:-
1. Electrically or pneumatically powered tools like
hammers, wire cutters, welding cutters, hand
driven hydraulic jacks etc.
2. Oxy-acetylene torch
 Sequence of demolition:
o All cantilever structures shall demolished first.
o Before demolishing roof, all water tanks and lift
rooms shall be demolished.
o Demolition of floor slab shall begin at mid span
and proceed towards the supporting beams.

10. o The order of demolition of floor beams shall be as
follows:
• Cantilever beam
• Secondary beam
• Primary beam
o Non load bearing walls and partition walls shall be
removed prior to demolition process.
o Columns and load bearing walls shall be
demolished after removal of beams on top.

12. 2-WRECKING BALL METHOD:
 In this method crawler mounted crane is used.
 A steel ball of 0.5-2 ton is suspended by a crane.
 Repeated hitting by a steel ball can demolish
concrete or masonry.
 There are two techniques in this method:
1. Vertical drop by wrecking ball
2. Swing action by wrecking ball
 This method also demands experienced operators
in order to handle the wrecking ball and control
the demolition.
 This method is widely used in European countries.
It is not suitable for urban areas because it
produces too much noise, vibration and dust.

14. 3-PUSHER ARM TECHNIQUE:
 In this method of progressive demolition a machine
like “hydraulic excavator” is lifted with a steel
pusher arm which exerts a horizontal thrust on to
the building fabric.
 This method is only used only when the machine is
operated from a firm level base with a clear
operating base of atleast 6m.

15. 4-THERMIC LANCE TECHNIQUE:
 Suitable:- other method not employed then used.
 The aluminium alloy or iron alloy wire are enclosed
in a same metal pipe of about 14mm to 18mm in
diameter.
 At first, the metal lance is ignited using acetylene
gas flowing between the wires in pipe. The
acetylene gas is turned to oxygen gas and the
metal lance continues to burn.
 The heat of combustion can melt concrete and
rebar. another lance is available using a metal
powder, which is called a ‘power lance’.

17. 5-CONCRETE SAWING METHOD:
 Suitable:-
 For alteration and additional works in a building.
 To cut concrete slab and wall elements.
 For forming openings into existing structures like a
basement, service tunnel, flyover etc.
 Methods:-
1. Wire saw cutting:-
A loop wire saw with a diamond bit can cut around
the circumference of the concrete section.
(suitable:- Mass & Foundation concrete)

18. 2. Diamond disc cutter:-
It is capable of cutting reinforced concrete. A disc
cutter over 1000mm in diameter is available.
3. Diamond core boring machine:-
This method is capable of drilling holes of 100-
150mm diameter in concrete. When the holes are
drilled side by side, concrete can be easily cut.

20. 6-DELIBRATE COLLAPSE METHOD:
 Suitable:- Used in area of isolated building on
reasonably level site.
 Demolition by deliberate collapse consists of
systematic removal or weakening of the key
structural elements to induce the collapse of the
structure.

21. 7-PRESSURE JETTING METHOD:
 A high pressure water jet of about 250-300Mpa
from a nozzle of about 0.3-0.5mm in diameter can
cut plain concrete by abrasion.
 An abrasive water jet which contains garnet or steel
particles can cut reinforced concrete.
 Suitable:- Demolishing nuclear power plants.

22. 8-BURSTING:
 In this method demolition of building is
accomplished by creating bursting force, and
building collapse itself due to gravity.
This method is classified into two type
static bursting dynamic bursting
-Buster with wedges -water gun
-Chemical expansive -gas cylinder
demolition Agent -cardox
-mild explosives
-explosives

23. Chemical expansive
demolition
Mild explosive

24. water gun
cardox

25. 9-IMPLOSION TECHNIQUE:
 An implosion is an event something collapses
inward , because the external atmospheric pressure
is greater than the internal pressure.
 Suitable:- 20 storey building, Used where site
conditions are not preferable
 Steps of demolition by implosion technology:-
a. Drilling of holes for placing explosives.
b. Quantity of explosive
c. Types of explosive and detonators
d. Test blast
e. Wrapping holes
f. Ballasting
g. Falling of structure

27. SAFETY MEASURES DURING DEMOLITION:
 The following safety measures should be taken
before and during demolition:-
1. Disconnection of utilities
2. General safety
3. Walkways & sidewalks
4. Catch platforms
5. Protective screens
6. Temporary supports
7. Dust and noise

28. Thank You