Chapter 3 - Rock excavation Flashcards
Classifications of rock
Igneous/ Sedimentary/ Metamorphic
Igneous rock formed?
When earths molten material cooled.
Examples of Igneous rock
Granite & basalt
What rock is most difficult to excavate?
Igneous rock
Sedimentary rock formed?
Precipitation of material from water & air. Highly satisfied & has many planes of weakness. (Sandy granules)
Most easily excavated rock?
Sedimentary rock
Examples of Sedimentary rock
Sandstone/ shale/ limestone
Metamorphic rock formed?
Originated as igneous/ sedimental rock, but been change by heat, pressure or chemical action
Examples of metamorphic rock
slate/ marble
Difficulty in excavating rock depends on?
Number of factors in addition to type
Factors of difficulty in excavation rocks
Extent of fractures (&other plane of weakness)
Whether rock has crystalline structure
Amount of weathering occurred
Predominant grain size
Rock brittleness
Rock hardness
How is relative hardness of rock measured?
Mohs scale from 1 (talc) to 10 (diamond)
Rule about rock investigation
Any rock that can be scratched by knife blade (harness about 5) can easily by excavated by ripping/ other mechanical method.
What is required to evaluate (hard) rock characteristics?
Investigation report - to choose right equipment
What are the principal methods for investigating subsurface conditions?
Drilling
Excavating test pits
Seismic measurements
What are the processes of moveing rocks?
Loosening
Loading
Hauling
Compacting
Loosening
Blasting, chemical or mechanical procedures
What influence choice of equipment for loading/ hauling/ compacting?
Loadability
What is the traditional method for excavating rock?
Drilling blat holes in rock
Loading holes with explosives
Detonating explosives
Loading fractured rock into haul units with power shovels
Hauling rock away in trucks
What is the newer alternative method for excavating rock?
Tractor-mounted rippers to loosen rock
Wheel loaders to load fractured rock into haul units
Reinforced scrapers to load & haul fractured rock
How is tunneling in rock form?
Drilling & blasting to form specialized form of rock excavation
What is recently used for tunneling?
Machines or mechanical moles equipped with multiple cutter heads = capable of excavating full tunnel.
Advantages of hydraulic drills
Penetrate faster
Consume less energy
Produce less noise & dust
Raise boring
A drilling technique in which a large diameter hole is drilled upwards from the bottom.
Procedures of raise boring
- Pilot hole is drilled from surface into mine/ other underground cavity.
- Large reaming head is attached to lower end of raise boring machine drill string which has been lowered into the shaft.
- Large diameter hole is created as the reaming head is rotated and raised by the raise boring machine sitting on the surface.
How is rock drills traditionally been powered?
Compressed air
What type of material is used to manufacture drill bits to drill through diamond.
Polycrystalline diamond (PCD)
How is a PCD drill bit made?
Consists of tiny diamond particles bonded together by a sintering process to create a hard, durable material
Principal explosives used for rock excavations
Dynamite
Ammonium nitrate
Ammonium nitrate in fuel oil (ANFO)
Slurries
Slurries
Mixtures of gels, explosives & water.
May contain powered metals to increase blast energy.
Detonators used to initiate explosion include which type of caps?
Electric & non-electric caps
What type of wires us used to make up electric blasting circuits?
Legwires
Buswires
Connecting wires
Firing lines
How can electric blasting circuits be connected
Series
Parallel
Parallel-series
Legwires
two wires that form integral part of each electric blasting cap
Buswires
are used to connect legwires of caps into parallel of parallel-series circuits
Connecting wires
are used to connect legwires/ buswires to firing line
Firing lines
consist the power source of 2 parallel conductors that connect the power source to remainder of the blasting circuit.
Blasting is controlled by?
Government regulations
Major safety precautions for blasting
- Storage magazines for explosives should be located in isolated areas
- Detonators must be stored in separate containers
- Electric blasting should not be connected to power source
- Permit no radio transmission in electric blasting circuit
- Protect detonators from all physical harm
- Check blast holes before loading (hot rock/ steel = explosion)
- Do not drop/ tamp primed charges.
- Only use non-metallic tools for tamping
- Clear signals for blasting
- Wait at least 1h before investigating a misfire.
Advantages of ripping
Less expensive than drilling/ blasting
Increased production
Fewer safety hazards
Reduced insurance cost
Parallelogram ripper
Maintains constant angle with ground as raised and lowered.
Automatic ripper
Control ripping depth & vary tip angle as raised and lowered.
Upper hydraulic cylinder tip angle
Permits tip angle to be varied as desired to obtain optimum results
Different tip angles
Penetrate surface
Produces optimum rock breakage
Impact rippers
Utilize hydraulic mechanism to impact a hammering action.
Increase ripper production.
What needs to be considered when ripping
Speed & depth
Spacing of ripper passes
Number of shanks to be used to max production
On what depends the number of shanks to be used to max ripped production?
Rock type
Tractor power
Depth of ripping
Number of shanks should be number that yields the desired penetration (without straining tractor)
What needs to be considered to choose rip direction?
Rip downhill - gravity advantage
Rip uphill - ripping laminated material
Why rip uphill when ripping laminated material
To enable ripper teeth to penetrate under layers
How to rip limestone
Use dozer with ripper attachment
Depth of ripping depend on
Number of shanks used & tractor power
Stratified material - match ripping depth with layer thickness
What should be considered with ripping speed?
Speeds needs to be kept low - to reduce wear on ripping teeth & shanks.
Compressed air
Used as a power source for construction tools & equipment.
Used to clean out drill hole.
Hydraulic power
Power source for rock drilling.
Uses for compressed air in construction
Paint spraying
Pneumatic application of concrete (shotcrete)
Conveying cement
Pumping water
Operating pneumatic tools
Pneumatic tools that use compressed air
Spaders (trench diggers)
Concrete vibrators
Drills
Grinders
Hammers
Paving breakers
Sandblasting guns
Saws
Staple guns
Nailers
Tampers
Wrenches
Examples of pumps & water supply systems utilize in construction
Dewatering excavations
Mixing & curing of concrete
Aiding soil compaction
Jetting spiles into place
Supply water
