Quarry Practices

1
Quarry Practices

• Drills and Drilling

2
Drills Drilling

• Drills for drilling -
• Blast holes
• Sampling rock formations exploration
• Production operations
• Are hammer (percussion) drills, rotary drills
  diamond drills
• Auger drills are used in soft formations for
  sampling blasting (occasionally)
• Reverse circulation RC drilling, an important
  exploration technique.
• Drills used in quarrying are invariably of
  pneumatic or hydraulic type.

3
Drill types

• Hammer drilling-
• Pneumatic percussion tools used in quarrying
  range from jack-hammer machines to long-hole
  drifters mounted on a wide range of carriers,
  down-hole hammers
• Surface Hammers
• Fluid pressure is used to force a piston back
  forth to strike the drill steel, piston
  reciprocates by means of an automatic valve,
  valve action set by the designer.

4
Hydraulic Drill

• Hydraulic top-hammer drills
• Uses hydraulic oil instead of compressed air.
• Higher pressures result in greater penetration
  rates, reduced energy costs greater efficiency

5
Drill Rotation

• Rotation must be provided so that successive
  blows of the bit are moved around the face of the
  drill hole in such a way as to allow the rock to
  break spall into chips that can be flushed from
  the hole.
• Spacing between impacts not to be too great,
  generally more abrasive the rock the slower the
  rotation speed.

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Drill Bits

• The smoothness of rotation dependent on no. of
  pawls teeth on the ratchet ring, the fastest,
  most even rotation achieved with 4 pawls an
  uneven no. of teeth pneumatic drills

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Rockdrill

• Pneumatic Rock Drill
• Lubrication is important in the cold moist
  environment using compressed air flushing water

8
DTH Drill

• Down-Hole Hammers
• More efficient use of compressed air power on
  deeper holes.
• Piston blows direct to the bit, no energy loss to
  drill string.
• Drill string lighter only imparts rotation
  provides air passage to the hammer
• Improved flushing chip removal, more efficient
  use of compressed air

9
DTH Rig

• Down-Hole Hammers

When bit is lifted from hole bottom full air
volume passes without operating the
hammer. .Hammer commences operating as soon
exhaust valve closed by running the bit to hole
bottom
Down-hole hammer drilling
10
Rotary drills

• Rotary Drilling
• Auger Drills
• Used in soft formations sand, clay, coal, soft
  shales sandstone
• Hole diameters range from 50 to 1500 mm depths
  to 90m
• Rotary speeds are slow but torque requirements
  are high
• Main use is for sampling

11
Auger Drill

• Rotary Drilling

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Exploration Drilling

• Reverse Circulation RC Drilling
• Where hole sidewall failure would contaminate the
  drill cuttings
• Rotary drilling with air, water or mud
  circulation involves 4 basic functions
• Rotation of drill bit attached to the drill rods
• Provision for applying adequate weight on the
  drill bit
• Ability to hoist rods from hole add rods as
  necessary
• Pumps to force a suitable fluid around the bit
  carry cuttings to the surface

13
RC Drill Fluids

• Reverse Circulation RC Drilling

Bad standing country or high water table can
preclude the use of air, particularly in
exploration drilling. In these cases water or
mud liquids are used to stabilize the hole, cool
the bit remove cuttings
14
Quarrying

• Rocks Minerals
• 2500 minerals are known, less than 20 are
  commonly found in rocks.
• Most frequent are-

15
Rock Types

• Classification of Rocks
• Three groups of rocks can be defined
• Igneous rocks
• Are emplaced in the molten state as magma either
  at depth or on the surface via volcanoes eg.
  Basalts, Granite Rhyolite.
• Sedimentary rocks
• Are formed through the accumulation of mineral
  particles or sediments. Clays, shales,
  limestones, dolomites quartzites are examples
  of sedimentary rocks which have undergone low
  level metmorphism.

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Rock Types cont

• Classification of Rocks
• Metamorphic rocks
• Form when existing rocks are changed by heat
  and/or pressure to develop new minerals and/or
  textures
• Sedimentary ingneous rocks if involved in major
  earth movements where conditions of temperature
  pressure are drastically changed, new minerals
  are formed other features such as banding are
  imprinted .
• Many are hard and even grained suitable for
  aggregates, others break into thin fragments
  unsuitable for aggregates.

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Geological age

• Classification of Rocks
• By age

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Structures

• Rock structures
• Stress relief processes are expressed by-
• Folds
• Faults
• Joints
• Concerned only with distribution of useful
  deposits, properties of the deposits safety of
  quarry faces

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Processes

• Folds

20
Quarry Examples

• Folds
• Fault

21
Fault Types

• Faults
• Results when deformation is so intense that
  disruption or breakage of a rock mass occurs
• Movement along a fault plane may be horizontal or
  vertical. In many cases the movement is oblique
  giving both strike dip faults

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Hazards of faults

• Faults
• Depending on its dip faults can make quarry faces
  extremely dangerous, particularly so when water,
  entering from above mixes with clay fines
  soften it or increase the hydrostatic pressure
  between fault surfaces separates them

23
Bedding

• Bedding Joints
• Bedding
• Sedimentary rocks are made up of layers of
  particles usually laid down horizontally under
  water. This layering is known as bedding.
• The dip of a bedding plane relative to a quarry
  face can have a major effect on safety
• Widely spaced bedding planes are termed
  massive, where more closely spaced, bedding
  plane weaknesses cause large slabs to flagg
  break off

24
Joints

• Bedding Joints
• Joints
• Most rock faces are broken by smooth faced
  fractures which in sedimentary rocks are not
  parallel to bedding and along which there is no
  evidence of movement. These are referred to as
  joints.
• They are formed by decreases in volume during
  cooling of igneous rocks, folding or faulting, or
  relief of lateral stresses.
• Generally are straight planar but may be
  curved, like faults bedding, they can create
  dangerous conditions in quarry faces.

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Quarry Features

• Bedding Joint
• Features in a
• Quarry face

26
Bench Drilling

• Drill Pattern Design
• Important terms used in bench drilling operations
  are shown in the figure

In addition to rock properties bench is
influenced by Hole diameter. Bench
height Fragmentation Bench stability
requirements Terrain conditions Environmental
restrictions
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Design Basics

• Hole diameter
• Is closely related to bench height burden
  should be between 0.5 - 1 face height
• d 5.10K where d drill hole diameter in mm
• where K bench height in m
• Rock fragmentation size tends to increase when
  ratio H/d lt 60
• Smaller hole diameters therefore smaller
  burdens give better fragmentation less ground
  vibration.

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Bench Features

• Drilling pattern
• The burden spacing together form the drilling
  pattern, are dependent on how much explosive can
  be placed at the bottom of the drill hole

• Bench
• Spacing
• Burden
• Stemming
• Column charge
• Bottom Charge
• Total charge

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Blast Theory

• A larger dia. hole will hold more explosive,
  burden spacing can be greater.
• The relative strength of the explosive is an
  influencing factor
• Theory is -
• Drill hole is charged with a bottom charge,
  density as great as possible
• Above is placed a column charge with explosive
  concentration ½ bottom charge
• Upper part of hole filled with stemming sand

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Hole design

• Length of bottom charge 1.3 burden
• Length of stemming burden
• Length of column charge depends on height of
  bench
• Bench height gt 2 burden
• Burden 0.045d drilling deviation (m)
• d is hole
  dia. in mm
• Spacing is usually 1.25 burden
• Burden spacing is still a matter of
  approximation because of the difficulty of
  predicting properties of rock when blasted.

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Blast Variables

• Variation of design based on rock properties
  hole diameter.

Practical values of burden as a function of drill
hole diameters Spacing between holes
1.25burden Height gt 2burden Benches higher than
20m should be avoided
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Face profiling

• Profiling Blast holes
• Achieves the most efficient combination of
  drilling charging
• Use of a laser instrument which measures face
  profile relative to drill hole

Determines the burden at each point in the hole
33
Blast practice

• Blasting in Rows
• In practically all quarry blasting a number of
  surface holes are fired in each blast, and in
  most production blats the holes are arranged in
  rows.
• Each charge in a blast sets up stresses in the
  rock generates pressures with the gases
  produced
• Firing of adjoining charges puts extra stresses
  on the rock between holes, this coupled with
  rock collisions makes for better fragmentation
• Single row firing is practised at many quarries,
  but where circumstances permit, multi-row firing
  is used
• As a general rule three rows would appear to give
  best fragmentation and heave characteristics.

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Fire order
Delay blasting also enables the total amount of
charge to be increased many times without
increasing ground vibration Using non-electric
and electronic detonators, an unlimited number of
delays can be incorporated in one blast.
Numbers refer to order of detonation
35
Firing Delays

• Examples of unlimited
• Number of delays
• Incorporated in one
• blast