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Rock Excavation.

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Presentation on theme: "Rock Excavation."— Presentation transcript:

1 Rock Excavation

2 Rock Characteristics Igneous Rock – granite, basalt
Sedimentary Rock – sandstone, shale, limestone Metamorphic Rock – originated as igneous or sedimentary and then changed by heat, pressure, chemical reaction – slate, marble, schist Hardness – Moh’s scale 1- talc -> 10 diamond

3 Rock Difficulty in excavation due to
Rock type, extent of fractures, other planes of weakness, amount of weathering, predominant grain size, brittleness or hardness

4 Investigation Drilling – core samples, tv dropped down shaft
Test pits – only good for soft rock Seismic measurements

5 Rock Handling 4 phases Loosen – blast or rip Load – shovel or loader
Haul – truck or wagon Compact - roller

6 Tunneling Old days drill and blast Now tunnel boring machines (TBM)
F 8-4 Usually 1 use machine Rotating head with debris handling system and Jumbo – large mobile frame so that you can drill a complete rock face at one time

7 Tunneling Hydraulic jumbo – self propelled machine with hydraulic arms with drills – drills blast holes in entire face F 8-5 Mucking machine – form of shovel used to load fractured rock into haul units

8 Drilling Equip Percussion – jackhammer, drifters, wagon drill, track drill operates by hitting a bit which rotates between blows F 8-6 Rotary drill – diamond tipped cutter head – well drilling machine F8-7 Rotary-percussion T 8-2 Down hole drills F 8-8 Percussion device is mounted directly above drill bit at bottom of hole Less noise, less air required to clear hole, longer drill life higher efficiency

9 Drilling Equip Drill rate depends on rock hardness, drill type, drill energy, bit type Increased air pressure = increased drill production also increases costs Raise boring Drill pilot hole down and then raise rotating reaming head 1,000,000 # upward thrust,400,000# torque

10 Drill Bits F8-10 Tungsten Carbide steel
Drill steel – connects drill bit to percussion machine Drill pipe connects rotary bit to machine

11 Drill Patterns Size of hole, depth, spacing & amount of explosive depends on degree of rock break desired, rock type, soundness, explosive used Usually test blast to determine exact pattern F 8-11 shows patterns

12 Drill Patterns Volume/hole = (S^2*H)/27 S = hole spacing
H = effective hole depth (* usually 90% of hole depth) Rock volume/ft of hole = Volume per ft of hole/ drill hole depth

13 Explosives Dynamite Ammonium nitrate Ammonium nitrate in fuel oil
Has been replaced by next three due to lower cost and easier to handle than dynamite Ammonium nitrate Ammonium nitrate in fuel oil slurries

14 Detonators Electric blasting caps
Instantaneous or time delayed Ignite primers – usually placed at bottom of hole Either primer or primacord Amount of explosive required to produce desired rock fracture = powder factor. Pounds/bcy Blast holes loaded with explosive except for last several feet Stemming is placed on top of explosive – inert material

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