Drilling and blasting

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: Abrasion drills Percussion drills 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 : Short drills Diamond drills

7. SHORT DRILL DIAMOND DRILL

8. 2) Percussion drills : I n 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 : Churn drill Drifters Jack-hammer Piston drill Rotary percussion drill OR Rotary hammer drill 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 : Dynamite Ammonium nitrate Slurry ANFO RDX 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. 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. 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. 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 b y dynamite primer placed at bottom of hole. RDX : RDX = Rapid Detonating Explosive Other explosives are : Gun Powder Blasting Gelatine Liquid oxygen

20. RDX DYNAMITE SLURRY ANFO AMONIUM NITRATE

21. EXPLOSION PROCESS The explosion process is as follows : The blast hole is cleaned and gun powder or dynamite c harge 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. 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.

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

23. THANK YOU