WEL COME

DRILLING AND BLASTING

Index  Introduction of Drilling and its Necessity  Terminology use for drilling  Selection of drilling method  Selection of drilling equipments  Introduction of Blasting  Method of blasting  Terms used for blasting  Explosive used for blasting  Precaution in blasting

Introduction Drilling : Before rock is excavated, it is Necessary to loosen it.In the case of hard rocks this loosening is done by drilling the holes, filling these with explosives and discharging the explosives.

Necessity of Drilling Cracking of rocks are requirement for construction of Dam. Take out the tones from the cory. To obtain samples of soil for test. To provide wells for supplies of water or for deep drainage. To locate and evaluate deposites of minerals.

Terminology use for Drilling Bits : The part which directly engages the rock for its disintegration is known as the ‘drill bit’. They can be sharpened as well as replaced and are relatively mexpensive.

Jack Hammers These are hand air operated percussion type drills. They are used for drilling holes, these hammers are also known as ‘Sinkers’.

Drifter : These are similar in operations to jack hammers. They are used deeper holes weigh from 35 kg to 120 kg. Because of higher weight they are mounted for horizontal. Diamond Drills : Diamond drills are used primarily for exploration drilling, where cores are desired for the purpose of studying the rock structure.

Wagon Drills Wagon drills consist of drifters mounted on masts which are mounted on wheels to provide portability. Up to 30 ft or more in depth. They may be used to drill at any angle from down to slightly above horizontal.

Carbide inset bit : The carbide insert bit is a detachable bit whose cutting edge consist of tungsten carbide embedded in a softer steel base. Depth of holes, 12 ft.

Selection of Drilling Method  Hardness of the rock.  Depth of Bore holes.  Nature of terrain.  Texture of rock.  Availability of water.  Size of project.

Selection of Drilling Equipments  For small diameter shallow bore holes, use jack hammers.  For upto 8 cm dia. Bore holes use diamond drills.  Upto 15 cm dia. And 15 m deep hole use track mounted, rotary percussion or piston drills.  For 15 cm to 30 cm dia. Holes for 15 m to 90 m to depth, use blast hole or rotary drills.  For bores upto 8 cm dia. Use diamond drills.  For very large cores, use short drills.

Selection of Drilling Pattern  Type of rock  Quantity of explosive used  Type of drill used  Rapidity of explosive used  Size of drill used  Depth of hole to be drilled  Amount of stemming

Blasting Rock blasting is resorted when rock has to be loosened so that the entire rock or part of the rock may be removed. The geological formation influences the type of equipment and the drilling pattern.

Methods of Blasting  Controlled and uncontrolled.  Primary and secondary.  Single shot and multiple shot.  Electrical and non-electrical.

Terms used for Blasting  Dynamite  Safety fuse  Blasting cap  Prime line  Blast hole  Primer  Stemming  Prime det  Detonator  Trunk line

Explosive used for blasting  Dynamite  Ammonium nitrate  Sturry  ANFO  Rapid detonating explosive (RDX)

Precaution in Blasting Failure of explosion Line of Least Resistance Needle and tamper Notice of blasting Retreat distance Seepage of water Skilled supervision Precautions during transportation Precautions during firing

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