Among all the drilling method, Down The Hole(DTH) drilling is being used more and more widely and has very high efficiency for some cases. Here, we will introduce the specific application for DTH drilling as most import part of whole basic drilling knowledge.

Mining RC – Exploration

− Surface drilling − Exploration

− Underground drilling −Grade control

Quarrying Construction

− Aggregate and limestone − Civil engineering

− Dimension atone industry
Well drilling Oil and gas

− Water well − Shallow drilling

− Energy well − Seismic

Surface Drilling – Mining

Application Demands

−In surface mining productivity is probably the most important factor

−This requires high availability on equipment, good and predictable service life on drilling tools

−Customers usually have good follow up on costs and performance

−Drilling accuracy is an important factor as customers strive to use optimal drill and blast patterns

Three main types of holes aredrilled in surface mining

−Blast holes

Hole diameter 115 – 229 mm (4½ – 9 in)

Hole depth 6 – 20 m (18 – 60 ft)

− Blast holes are production holes and willbe filled with explosives

− Drilling accuracy is important to obtaingood and even distribution of theexplosives in the rock

− This will optimize fragmentation andfacilitate further handling such asmucking, hauling and crushing

−Buffer holes

Hole diameter 115 – 152 mm (4½ – 6 in)

Hole depth 6 – 20 m (18 – 60 ft)

−Perimeter holes (pre-split)

Hole diameter 115 – 152 mm (4½ – 6 in)

Hole depth 6 – 20 m (18 – 60 ft)

− Pre-split and buffer holesare used for wall control

− This method reduces theamount of waist rockexcavation and also the risk ofrock fall from pit walls

− Usually smaller hole diameterthan blast holes to carry lessexplosives

Underground Drilling– Mining

Application Demands

−Underground mining is a verycompetitive industry so productivity is avery important factor

−Drilling accuracy is a must for good orerecovery and to avoid dilution

−Drilling accuracy is also important foroptimal blasting pattern, goodfragmentation and cost effective downstream operations

−This requires high availability onequipment, good and predictable servicelife on drilling tools

Application Cases

−DTH drilling in large scale miningoperations underground such asSub-level stooping and sub-level caving

−DTH is also used for drilling of holes forcables, ventilation or other“communication” needs betweendifferent areas or levels in the mine

Media Holes

−90mm (3 ½”) – 254mm (10”)

− Media holes to connect levels, drifts, areas with each other is common in underground miningoperations. Purpose of these types of holes is to transport backfill paste, connect electric cables and waste water pipes

Quarryingaggregate – limestone

Application demands

−A wide spread of customers in thisapplication, from small quarries servicedby contract drillers to big operationswith own personnel and equipment

−Blast hole drilling

Hole diameter 90 – 205 mm (3½” – 8”)

Hole depth 10 – 30m

− Many quarries are located close to urbanareas and environmental regulations putrestrictions on drilling parameters

−Hole accuracy is important

−Noise restrictions give DTH drilling anadvantage

Product selection criteria

−Price and performance are importantfor quarry/limestone drillers

−The smaller contractor is more priceconscious and the big contractor orquarry owner is more performancefocused

−Product availability, service and supportare essential factors

−Drilling accuracy important for optimaldrilling pattern and good fragmentation

Construction– Civil Engineering

Typical drilling applications

−In civil engineering DTH drilling is used for alot of different applications

−Blast holes at construction sites used forremoval of rock in road and railway projects,construction of HE plants etc

−Foundation drilling methods are used toreinforce or stabilize rock and soil in differentconstruction projects

Geotechnical drilling

−Holes which is part of a structure orprocess created to stabilize andcontrol rock and soil. Often used incombination with overburden drillingsystem.

−Soil Nails

−Earth / Rock Anchors

−Umbrella drilling

−Sinkhole repair

−Compact grouting

Product selection criteria

−Foundation drilling is usually made byspecialized companies

−High demand on product performancein difficult drilling situations

−Trouble free drilling in mixed groundconditions, many times with casingsystems

−Service and support is important

Water Well Drilling

Application demands

−Lots of “one rig” companies in thisapplication

−Geothermal drilling has increased the interestand more performance conscious drillershave entered the field

−Lot of drilling in conditions that requirescasing tube systems

−Product performance essential as drilleddepths sometimes are over 600 m (2250 ft)

−Hole size 115 – 400 mm (4½” – 16”)

Geothermal WellDrilling

−Primarily, these contractors are engagedin energy wells for private houses,hospitals and industry buildings for heating in winter and cooling in summer

− Normally it works together with heat pump to get best efficiency, and it is being developed very well in China due to environmental protection

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