University of Saskatchewan

Transcription

1 University of Saskatchewan Geological Engineering GEOE Introduction to Mineral Engineering

2 Lecture 2 Underground Mining Methods Bulk vs. Selective Reasons for Selection (Geotechnical, Geometry, Value, Grade, Dilution Control, Skill of work force, health and safety, etc) Mining Equipment (mobile) Tunneling Methods

3 Underground Mining Methods MINING METHOD Is defined as the manner of extraction of an ore deposit underground and depends on many factors. Different Methods are used for Hardrock and Softrock as well as Bulk and Selective Mining

4 Factors to Consider Geological and Geotechnical Considerations Strength of Ore Strength of host rock Stress field Structural Geology (faults, contacts, joints, folds, etc.) Dimensions of orebody (thickness, strike length, height) Orientation (dip, plunge) Depth

5 Factors to Consider Economic and Logistical Availability of Skilled Labour Availability of Equipment Availability of backfill Legacy issues Health and Safety factors Economics Production Requirements Value of ore Operating Cost Capital cost Processing cost

6 Common Requirements for all Mining Methods Access for equipment, personnel, services (electricity, water, compressed air, ventilation). Arteries for the transport of ore & waste out of the mine and possibly backfill into the mine. Drainage safe working conditions

7 Classification of Mining Methods 7

8 Choice of Mining Method will impact Orebody recovery and Dilution Amount of development needed Capital requirement and operating costs Type of equipments required Cycle time and sequence of operations Production (tonnes per year) Risk

9 Classification of Underground Mining Methods Two main Classes of Underground Mining Methods: Bulk Mining (Caving, Open Stoping, VCR) Selective Mining (Cut and Fill, Room and Pillar, Shrinkage)

10 Sub-Classifications Overhand Stoping Bottom Up Method Underhand Stoping Top Down Method Longitudinal Stoping Long axis of stope is parallel to orebody strike Transverse Stoping Long axis of stope is perpendicular to orebody strike

11 Sub-Classifications Underhand Stoping Stability of the Orebody is very poor or there is no access to the lower part of the orebody Examples: Underhand Cut and Fill used in narrow veins at depth or underhand Blast hole open stoping used for bulk mining. Workers are always standing on solid ore and below supported or filled back. Overhand Stoping Stoping operation start a the bottom of the orebody and proceeds to upward Most popular method of stoping.. Example: Shrinkage stoping,, Cut and Fill stopes,, Room and Pillar, Caving Methods, VCR Method of Mining, Sub Level Stoping

12 Hard Rock Selective Mining Methods Room and Pillar Cut and Fill Shrinkage Alimak Mining Raise bore and Box hole Mining

13 Room and Pillar Applicable to relatively flat orebodies and employ natural support (rock pillars). The orebody is excavated as completely as possible leaving ore/waste as pillars to support the hanging wall (back). Dimensions of the stopes and pillars depend upon factors such as the stability of the back, stability of the ore, thickness of the deposit and rock stresses. Horizontal Mining is the most commonly used room and pillar method. It is applicable to horizontal or near horizontal deposits (< 5 dip) and to inclined deposits of greater thickness, with the floor arranged for a moderate slope that allows for use of mobile equipment. Inclined Mining is for inclined orebodies (20-30 dip). Stoping proceeds upwards along the dip direction. The steep slope precludes use of mobile equipment. Step Mining adapts horizontal stoping to an inclined orebody (20-45 dip). This is a recent development in the industry for mining orebodies that would otherwise be precluded by their steep dip. It requires a special layout of stopes and a sequence of extraction resulting in the use of mobile equipment.

14 Horizontal Room and Pillar

15 Inclined Room and Pillar

16 Step Room and Pillar

17 Room and Pillar

18 Room and Pillar

19 Room and Pillar Features Summary of Applications relatively flat orebodies limited thickness competent hanging wall and ore Advantages... good productivity moderate cost flexible method, amenable to mechanization Selective minimal early development No backfill required Disadvantages... possible ground control problems Medium to low recovery, ore lost in pillars

20

21 Cut and Fill Cut and fill stoping methods excavate ore in horizontal slices or lifts, starting at the bottom of a stope and advancing upwards. The broken ore is removed from the stope after each lift is blasted. After a slice is mucked out, the void is filled with backfill. The fill supports the walls and provides a working platform for mining the next lift. Fill material can consist of waste rock however, it is more common to use tailings from the mill transported to mine in slurry form. When water in the fill is drained off a competent fill with a smooth surface is produced. In some cases the material is mixed with cement to provide a harder and more durable surface with improved support characteristics. Suited to steeply dipping, irregular orebodies,, weak host rock or large tabular steeply dipping irregular orebodies for multiple lifts or cuts

22 Cut and Fill

23 Cut and Fill

24 Cut and Fill

25 Cut and Fill

26 Longitudinal MCF

27 Longitudinal MCF

28 Transverse MCF

29 Cut and Fill

30 Cut and Fill Summary of application orebody width 2m - 30m tabular shape... good for irregular orebodies orebody dip 35 o -90 o good for low strength / high stress regions requires safe, stable back for man entry Expensive, generally high grade ore required for this method to be economic good selectivity minimum dilution

31 Cut and Fill Advantage moderate production and scale good selectivity low development cost adaptable to mechanization flexible method excellent recovery with low dilution tailings can be disposed of as fill Disadvantage high production cost fill complicates cycle requires stope access for mechanized equipment labour intensive ground settlement/instability risk

32

33 Cut and Fill Variations Underhand Cut and Fill or Undercut and Fill Developed to recover pillars or to mine low strength ore bodies Mining top down and placing a cemented/reinforced mat over the working area... enabling mining below. Drift and Fill Used to mine wide, flat, thin (<6m) orebodies with poor hanging wall conditions. Mining involves a series of parallel drifts with an access heading driven along the hanging wall contact. Each mined drift is filled with cemented sand fill... providing back support for the next drift. Post Pillar Hybrid between room and pillar and cut and fill moderately thick, flat, tabular ore bodies moderate to low strength back

34 Underhand Cut and Fill

35 Underhand cut-and-fill Weak, narrow vein orebodies Cemented backfill required

36 Post Pillar Cut and Fill

37 Shrinkage Ore is broken in horizontal slices working upwards. Sufficient ore withdrawn at the bottom after each slice to accommodate swell (30% - 40%) Remainder stays in the stope to provide a working platform... removed at the end. Stopes separated by intermediate (recoverable) pillars

38 Shrinkage orebody width 1.2m - 30m tabular orebody; ; regular boundaries dip >50 stable hanging wall and footwall uniform draw down important dilution generally low Ore must be unaffected by storage in stope Labour intensive method, limited scope for mechanization

39 Shrinkage

40 Shrinkage

41 Shrinkage Summary of Application Shrinkage not a common method... too labour intensive Employed only where mechanization not possible. Maintaining stope full of muck increases possible stope spans and minimizes dilution.. support and development costs reduced. Limited production capacity and bulk of ore tied up for a long time. t Advantages moderate production rate. draw down by gravity conceptually simple (small mine usage) low capital investment minimal support in stope moderate development good recovery, low dilution Disadvantages low productivity moderate to high mining cost. labor-intensive dangerous working conditions ore tied up in stope ore subject to oxidation, packing in stope

42 Shrinkage Variation - Raise or Alimak Mining A variation of shrinkage mining Long hole drill is mounted on an alimak raise climber Mechanized, cost effective method

43 Alimak Mining

44 Alimak Mining

45 Raise or Alimak Mining

46 Alimak Mining

47 Alimak Mining

48 Alimak Mining

49 Alimak Mining

50 Alimak Mining

51 Alimak Mining

52 Raise bore and Box hole Mining Summary of application Raise bore holes are excavated and filled. Can be used to mine tabular narrow steeply dipping deposits or moderately thick flat deposits. Low to high strength ore None entry Requires very high grade ore as method is very expensive Advantages Very safe Low dilution High recovery Miners not exposed to environmental hazzards Disadvantages Very expensive Low production rates

53 Raise Bore Mining

54 Raise Bore Mining Raise Bore Chamber Extraction Chamber

55 Box hole Mining

56 Raise Bore Mining

57 Hard Rock Bulk Mining Methods Sublevel / Blasthole / Long Hole Vertical Crater Retreat (VCR) Avoca Sublevel Caving Block Caving

58 Sublevel Stoping Methods Sublevel stoping is also known as "blasthole" stoping" " or "longhole stoping". vertical or steeply dipping ore bodies with regular boundaries mined from levels at predetermined vertical intervals drilling/blasting from sublevels (overcut( or undercut), mucking from undercut ore pillars between stopes for support, may be recovered later The orebody is divided into sections up to 100 m high and further divided laterally into alternating stopes and pillars. A main haulage drive is created in the footwall at the bottom, with cut-outs for draw-points connected to the stopes. Long hole blasthole and stoping uses longer and larger diameter blastholes than sublevel stoping,, thus requiring less drilling than sublevel stoping.. Greater drilling accuracy is required

59 Sublevel Stoping Methods minimum orebody width 2m tabular or massive shape Can be mined transverse or longitudinal dip >50 large stopes (non-entry) limited selectivity, orebody should be regular No Backfill pillar size considerations similar to room and pillar competent footwall, ore zone and hanging wall dilution a potential problem With Backfill pillar size must be suitable for recovery stress on pillars should be low fill material must allow recovery of pillars with minimum dilution

60 Sublevel Stoping Methods

61 Sublevel Stoping Methods

62 Sublevel Stoping Methods

63 Sublevel Stoping Methods

64 Sublevel Stoping Methods

65 Sublevel Stoping Methods

66 Sublevel Stoping Methods

67 Sublevel Stoping Methods SLOS Primary/Secondary with Transverse Drilling and Extraction 67

68 Sublevel Stoping Methods

69 Sublevel Stoping Methods

70 Sublevel Stoping Methods

71 Block Plan

72

73 Sublevel Stoping Methods Summary of Application method became popular after development of large diesel LHD s in the last 40 years efficient in drilling, blasting and loading high utilization of mechanized equipment limited selectivity with irregular orebodies Advantages good productivity moderate cost amenable to mechanization safe operating conditions good recovery; moderate dilution Disadvantages Expensive initial development inflexible / non-selective

74

75 Avoca Allows mining of narrow ore zones with high recovery. Requires stope development with upper and lower drill drifts, similar to longhole mining. Stope is backfilled with waste rock from the upper drill horizon... no pillars required. Advantages Flexibility no requirement for pillars waste storage with short haulage Disadvantages higher dilution advance limited by backfill availability must have two accesses

76 Avoca 76

77 Avoca

78 Avoca 78

79 Vertical Crater Retreat / VCR Very similar to Sub level stoping. Employs a unique blasting technique called the crater blasting Also resembles Shrinkage stoping as ore is extracted in horizontal slices. The ore is recovered from an undercut drawpoint system resembling that used in sublevel open stoping Can be used in steeply dipping ore bodies under the same conditions as sub level stoping and shrinkage stoping Blasted ore remains in the stope and is used to support the hanging wall

80 Vertical Crater Retreat / VCR

81 Vertical Crater Retreat / VCR Advantages VCR is a bulk, high-capacity mining method with good recoveries; It is an efficient stoping method that is very susceptible to mechanization and can have productivities in excess of 32 tonnes/employee-shift; It offers good wall support during the stoping phase by using shrinkage techniques; It is a safe method with miners working under a fully supported back that can be adequately ventilated. Disadvantages VCR requires extensive diamond drilling, pre-stope planning, and development lead-time for maximum effectiveness; Ore is tied up in the stope until final drawdown... representing lost income; Some ores are mineralogically unstable and may be subject to breakdown, causing problems with benefaction, drawing, etc.. High concentration of explosive and hole deviation may damage walls and may increase dilution problems

82 Sublevel Caving The orebody is divided into closely spaced vertical sublevels. From each sublevel the orebody is developed by a series of drifts from hangingwall to footwall to lateral extremity on strike From the sublevel drifts the ore immediately above is drilled with longholes in a fan shape pattern size should be large enough to allow for sufficient vertical sub-levels for lateral and vertical interaction massive and/or tabular and steep, uniform shape steeply dipping >50 degrees unless massive competent ore with a waste hangingwall that can cave. Stable footwall for development access. high dilution, very sensitive to poor fragmentation limited selectivity surface conditions must allow for subsidence Sublevel caving is usually carried out underneath an open pit when it becomes uneconomic to mine from the pit

83 Sublevel Caving

84 Sublevel Caving

85 Sublevel Cave

86 Sublevel Caving Summary of Application Longhole drilling is performed in a fan shaped pattern that radiates upwards from sublevel drift. Ore is mucked from the sublevel drift, transported and dumped into orepasses by LHD's. Production drilling and loading are carried out on separate levels ls and are independent of each other many work faces result due to the large number of drift faces ore is blasted against a caved face therefore explosive consumption is high Advantages high productivity rate many work faces and efficient highly mechanized safe method as non-entry Disadvantages high dilution surface subsidence results potential for high ore losses - low recovery explosive consumption high (choke blasting) high development costs hi intensity of drill and blast required in order to generate a mobile granular ore within a cave medium

87

88 Block Caving Block caving is applicable to large, deep, low- grade deposits. It is often done to continue mining after open pit mining becomes uneconomic or impossible. However, some mines start as block cave operations. A grid of tunnels is driven under the orebody. The rock mass is then undercut by blasting. Ideally the rock will break under its own weight. Broken ore is then taken from draw points. There may be hundreds of draw points in a large block cave operation (Figure 3).

89 Block Caving orebody and hangingwall must cave therefore the ore must have sufficient plan area to initiate cave through the undercut (>1000m2). Vertical dimension generally greater. massive and/or tabular and steep, uniform shape steeply dipping >50 degrees unless massive which then requires a high vertical dimension orebody and hangingwall must be weak and cavable. Otherwise the undercut area must be large and consequently fragmentation is large. high dilution, very sensitive to poor fragmentation no selectivity surface conditions must allow for subsidence

90 Block Caving

91 Block Caving

92 Block Caving

93 Block Caving

94 Summary of application Block Caving upon completion of the undercut the ore falls down finger raises or cones and is a continuous process as material is removed at the draw levell theoretically no production drilling is required. In practise, long l holes are drilled widely spaced to induce fracturing, secondary drilling of oversize rock is a frequent operation. ore handling in track mining utilizes gravity forces to deliver material to rail cars. However, chutes require small fine fragmentation and grizzly is very labour intensive and is generally a bottleneck in the production cycle. Ore handling in trackless mining is through drawpoint mucking and the development work required is substantially reduced since no grizzly zly level or raises. Rule of thumb: for an orebody to be cavable approximately 50% of the ore fragments should break to 1.5m or less in maximum dimension. One can't have large arches formed since will result in an air blast/or high stresses in the abutments.

95 Advantages Block Caving highest production rate of any underground mining method lowest operating cost of any underground mining method production (not development) is entirely by caving ie.. No drill or blast other than secondary blasting ability to be highly mechanized Disadvantages caving and subsidence occur on large scale high dilution draw control is critical to success of method slow and extensive development requirements high support costs caving and fragmentation is extremely difficult to predict or control inflexible method- no selectivity possible ore oxidation if caving/drawing is slow

96

97 Mining Equipment

98 Drilling

99 Drilling

100 Drilling Equipment - Jackleg

101 Drill Development Jumbo

102 Drill Development Jumbo

103 Drill Development Jumbo

104 Drill longhole ITH

105 Drill Longhole - ITH

106 Drill Longhole - Tophammer

107 Drill Longhole - Tophammer

108 Drill Longhole - Tophammer

109 Drill Raise bore rotary drill

110 Drill Raise bore rotary drill

111 Raisebore Station and Reamer Bit

112 Mucking Equipment - Cavo

113 Mucking Equipment - Cavo

114 Mucking Equipment LHD with 11 m 3 bucket

115 Muching Equipment Remote Control Scoop

116 Mucking Equipment 15 tonne Truck

117 Mucking Equipment 50 tonne Truck

118 Mucking Equipment LHD loading Truck

119 Mucking Equipment 50 tonne Truck

120 Mucking Equipment 50 tonne Truck

121 Mucking Equipment U/G ore train

122 Hardrock Mining Method Selection Nicolas Method Identify key factors that determine mining method Rank each of the factors for different methods Apply all factors to an orebody Orebody with the highest rating is the optimum mining method

123 Hardrock Mining Method Selection

124 Hardrock Mining Method Selection

125 Hardrock Mining Method Selection

126 Hardrock Mining Method Selection

127 Hardrock Mining Method Selection

128 Hardrock Mining Method Selection

129 Hardrock Mining Method Selection

130 Hardrock Mining Method Selection

131 Hardrock Mining Method Selection

132 Hardrock Mining Method Selection

133 Hardrock Mining Method Selection

134 SOFTROCK MINING Potash Coal

135 Potash Mining Long room-and-pillar mining method. Ore is mined from rooms in three passes, separated by pillars supporting the overlying strata. Automated Marietta continuous miners are capable of extracting up to 650t/h of ore. The run-of-mine ore is loaded on to extensible conveyors attached to the continuous miners. These connect to the main haulage conveyors, which move the ore to skip-loading pockets at the shafts, where it is hoisted to surface.

136

137

138 Long Wall Mining Highly mechanized underground mining system for mining coal. A layer of coal is selected and blocked out into an area known as a panel. A typical panel might be 3000 m long by 250 m wide. Passageways areexcavated along the length of the panel to provide access and to place a conveying system to transport material out of the mine. Entry tunnels are constructed from the passageways along the width of the panel. The longwall system mines between entry tunnels. Extraction is an almost continuous operation involving the use of self-advancing hydraulic roof supports sometimes called shields, a shearing machine, and a conveyor which runs parallel to the face being mined.

139 Longwall Mining

140 Long Wall Mining

141 Long Wall Mining

142 Long Wall Mining

143 Long Wall Mining

144 Soft Rock Room and Pillar Equipment

145 Soft Rock Room and Pillar Equipment

146 Soft Rock Room and Pillar Equipment

147 Underground Softrock Mining