Civil Engineering Method of Excavation

1. DRILLING
AND
BLASTING

2. INDEX
 DRILLING :
 DRILLING AND ITS NECESSITY
 TYPES OF DRILLS
 SELECTION OF DRILLING EQUIPMENTS
 BLASTING :
 BLASTING
 EXPLOSIVES USED FOR BLASTING
 EXPLOSION PROCESS

3. DRILLING

4. DRILLING AND ITS NECESSITY
Drilling is the process of making hole in solid
materials like rocks, timber, metal, etc. For blasting rocks,
drilling is necessary to make hole in the rock to place
explosive in the drill hole.
Different tools and methods are used for drilling
depending on the type of material, the size of the hole,
the number of holes and the time to complete the
operation.

5. Necessity of drilling :
 For breaking rocks for the foundation of dam
 For getting stones from quarry
 For making roads in mountains
 For tunneling
 For sinking caissons or well foundations
 For laying pipeline in the rocky strata

6. TYPES OF DRILLS
Drills can be broadly classified into the following two
categories:
1) Abrasion drills
2) Percussion drills
1) Abrasion drills :
In this type of drill, the grinding of rock into small
particles is carried out through the abrasive effect of a bit
which rotates in the hole. Common types of abrasive drills
are as follows :
a) Short drills
b) Diamond drills

7. SHORT DRILL
DIAMOND DRILL

8. 2) Percussion drills :
In this type of drill, the disintegration of rock into small
particles is achieved by the impact from repeated blows.
Common types of percussion drills are as under :
a) Churn drill
b) Drifters
c) Jack-hammer
d) Piston drill
e) Rotary percussion drill OR Rotary hammer drill
f) Wagon drill

9. CHURN DRILL DRIFFTER
JACK-HAMMER PISTON DRILL

10. ROTARY DRILL
WAGON DRILL

11. SELECTION OF DRILLING
EQUIPMENTS
Holes are drilled into the rocks for different
purposes like blasting, grouting, investigations, etc. The
drilling equipment should be so that maximum work can
be done at minimum cost.
The following factors should be considered while selecting
drilling equipments :
 Hardness of rock
 Depth of bore hole
 Nature of terrain
 Texture of rock
 Purpose of hole e.g. blasting, grouting, investigation,
etc.

12.  Availability of water
 Size of project
Guidelines for selection of drilling equipment :
 Jack hammer :-
-for small holes up to 3 m depth
 Diamond drill :-
-for drilling holes up to 8 cm dia.
-for drilling inclined holes, for getting cores up to 75
mm dia.

13.  Shot drill :-
-for obtaining cores of 8-20 cm dia.
 Piston drill :-
-for drilling blast holes of 15 cm dia. up to 90 m
depth
 Rotary drill :-
-for drilling blast holes 15-20 cm dia. Up to 90m
depth

14. BLASTING

15. BLASTING
The term blasting is used to indicate the
discharging of an explosive to loosen the rocks so as to
turn them into small pieces of stones.
Blasting is done to loosen the rock for ease in
excavation. Blasting is performed by discharging the
explosive placed in the hole drilled for the purpose.
Tremendous energy produced by blasting loosens the
rock.

16. EXPLOSIVES USED FOR
BLASTING
Various explosives used for blasting are :
1) Dynamite
2) Ammonium nitrate
3) Slurry
4) ANFO
5) RDX
1. Dynamite :
It is an explosive used for blasting. Dynamite
consist of 25 % of sandy earth saturated with 75 % of
nitro-glycerin. It is in the form of thick paste and it is sold
in cartridge. It is very poisonous in nature and develops
violent headaches through touch with skin.

17. Dynamite cartridge is placed in the bore hole and
tamped with wooden bar. The charge is fired by a fuse.
2. Ammonium Nitrate :
This type of explosive is widely used in
construction projects for surface as well as underground
explosion. It is more safer than dynamite because it is
detonated by special type of primer. It is economical than
dynamite.
3. Slurry :
This is a generic term for both gels and emulsion. A
slurry explosive is mace of ammonium, calcium or sodium
nitrate and a fuel sensitizer along with varying amounts of
water.

18. A slurry explosive mixture of oxidizing salts, fuels,
and sensitizers made water resistant by the cross linking
of gums or waxes is referred to as a water gel.
4. ANFO :
ANFO = Ammonium Nitrate Fuel Oil
This explosive is used extensively for construction
blasting and represents about 80% of all explosives used
in the united states.
It is a mixture of 4.5 kg ammonium nitrate and 5
liter no. 2 diesel fuel oil. This is the optimum mixture. The
mixture is saturated for 24 hours.

19. The mixture is free flowing and can be directly
poured into drill holes. In case of wet holes, the mixture is
kept in plastic bags and placed in holes. This explosive is
detonated by dynamite primer placed at bottom of hole.
5. RDX :
RDX = Rapid Detonating Explosive
Other explosives are :
a) Gun Powder
b) Blasting Gelatine
c) Liquid oxygen

20. RDX
DYNAMITE
SLURRY
ANFO
AMONIUM NITRATE

21. EXPLOSION PROCESS
The explosion process is as follows :
1) The blast hole is cleaned and gun powder or dynamite
charge is filled the bottom of the hole. A priming
needle in the form of copper rod is kept in the center
of hole. Grease is applied to the priming needle so
that it can be easily pulled out.
2) The remaining portion of the hole is filled with inert
material like rock powder or wet clay, known as
stemming. The stemming material is properly
compacted by copper rod.

23. 3) After temping is completed, the priming needle is
pulled out, and the hole so created is filled with gun
powder or dynamite.
4) A fuse is kept in the hole with its end 15-20 cm above
the surface of the rock.
5) The outer end of fuse is detonated by match box or
electric spark.
6) After blast the rock mass is divided into small parts.

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