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TERRAMIN AUSTRALIA LIMITED
COMMUNITY
TECHNICAL WORKSHOP
Blasting and Geotechnical
8th Dec 2016
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 2
Overview
Introduction
Tunnel Construction Cycle (Joe Ranford, Terramin Australia)
Vibration and Blasting Impacts (SAROS Group, Tony Zoitas)
Geotechnical considerations (MiningOne, Ben Roache)
Seismicity
Subsidence
Question and Answer
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 3
Introduction
Community Technical Workshops
Ground Water Meeting
Blasting and Geotechnical
Visual amenity
Dust and Noise
Other topics of interest
Core concerns related to blasting/geotech:
Contamination inc. mixing aquifers
Impact to bore water quality
Clogging bore with silt
Clogging bore with cement
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 4
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 5
Development Cycle
Drill
Blast/Charge
Bog/Muck
Support
Map
Repeat
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 6
Cut and Fill Mining
Designed Lift 4
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 7
Drilling holes for explosives
Twin boom drills on articulated carrier – Jumbo
~60 holes per face
2.5m – 3.5m depth
45mm diameter
Potential Concerns
Vibration
Fracture propagation
Mitigation Strategies
Proximity
Clay cover – Natural dampening
Geotechnical modelling
Design
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 8
Blasting/Charging
Detonator
Sequential firing
Not all at once
Primer
Explosive (4kg/hole)
ANFO
– Ammonium Nitrate
– Diesel (~5%)
AN Emulsion
Perimeter holes
Decoupled
Limits impact on walls
Limits fracture propagation
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 9
Rock Breakage
Explosion crushes rock
<100mm
Shock wave cracks rock
𝑉 = 𝐾𝑅
𝑄
−𝐵
Expanding gasses spread
cracks
Area of influence <1m
<1m
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 10
Blasting/Charging Cont.
Perimeter holes
Decoupled
Limits impact on walls
Limits fracture propagation
Path of least resistance
Potential Impacts
Ground vibration
Excess damage to rock
Mitigation Strategies
Proximity
Blast designs
Monitoring and reporting
Design
Perimeter
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 12
Bogging/Mucking and Haulage
10 t/bucket
~200t per cut
Loaded directly into trucks
Stockpiled
Potential Concerns
Surface noise
Dust
Mitigation Strategies
Mostly underground
Equipment Selection/modification
Noise barriers (vegetation screens)
Dust suppression
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 13
Ground Support
Ground Support
Rock bolts (2.4m-3m)
Cable bolts (6m)
Surface Support
High Tensile Mesh
Fiber reinforced shotcrete
Potential Concerns
Instability/subsidence
Mitigation Strategies
Appropriate installation/regular audits
MiningOne
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8th December 2016
Discussion of
Proposed Blasting
Activities – Bird in
Hand Project
T Zoitsas
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Copyright © Saros (International) Pty Ltd
Introduction
Tony Zoitsas
• B App Sc (Hons) Geology
• Director of Saros (International) Pty Ltd
• Independent specialists in blasting and vibration
• 20 years experience in blasting and vibration consulting
and instrumentation systems
• Member of the AusIMM
• Member of the IQA
• Vice President of the International Society Explosive
Engineers Australian Chapter
15
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Project Overview
16
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Decline Development
17
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Production Blasting
18
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Production Blasting
19
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Why Blast?
20
Blasting activities are required to facilitate the excavation
of rock in areas where this can not be achieved by
mechanical methods alone
The two phases of the mining operation which require the
utilisation of drill and blast practices include:
• Development of the Decline / Access Drives
• Production of the Ore Body
With the proposed cut and fill method of mining, the
blasting practices will be consistent across both phases of
the development and production activities
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Explosive Reaction
Ammonium
Nitrate
3NH4NO3
21
Fuel
CH2
+
Nitrogen
3N2
Carbon
Dioxide
CO2
Water
7H2O
++
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Detonation
Direction of burning
22
Detonation Front
Expanding gases
and vapour
Unconsumed
product
Shock waves
Typical VoD - ~4,500 to 6,000 m/s
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Scales of Blasting
Blasting activities can be adjusted in
accordance with the specific site requirements
and constraints
23
From small scale
activities in highly
sensitive locations
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Scales of Blasting
Blasting activities can be adjusted in
accordance with the specific site requirements
and constraints
24
To large scale mining
operations
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Blasting Impacts
25
Ground Vibration
Controls
• Rock type
• Explosive quantity
• Explosive type
• Degree of Confinement
• Initiation timing
Air Overpressure
Controls
• Burden to free face
• Uncharged collar length
• Explosive quantity
• Explosive type
• Rock type
• Initiation timing
• Number of holes
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Development Blasting
26
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Development Blasting
27
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Development Blasting
28
Design profile
Final profile
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Compliance Requirements
With respect to blasting activities, the typical compliance
limits that the Bird in Hand Mine would be required to
comply with are as follows:
• Ground Vibration – Not to exceed 5mm/s for 95% of
occasions, with an upper limit of 10mm/s
• Air Overpressure – Not to exceed 115dBL for 95% of
occasions, with an upper limit of 120dBL
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Compliance Requirements
• These limits are in line with the Australian Standards
and are adopted by most state regulatory authorities
• Australian blasting compliance limits are amongst the
most stringent in the world
• Both ground vibration and air overpressure limits are
based on human comfort criteria and are well below
damage thresholds
• The issue of air overpressure will only be relevant in the
early stages of the decline development
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Vibration Impacts
31
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Displacement
32
-5
-3
-1
1
3
5
0 0.5 1 1.5 2 2.5 3
Vibration
Vibration
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0 0.5 1 1.5 2 2.5 3
Displacement
Displacement
14 microns
4.16mm/s
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Displacement
Blast induced displacement in perspective:
• Blast – 14 microns
• Thickness of a human hair – ~30 microns
• Sheet of Paper – 100 microns
• Thermal Effects on Residential Dwelling – up to 2000
microns
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Air Overpressure
34
115dBL @ 20Hz
65dBA
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Air Overpressure
35
Audible frequencies
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Environmental Effects
Peak overpressure levels from wind
36
115dBL blast limit
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Controlled Blasting
Pre-tensioned concrete
• 32,000,000 Lt
• 18 metres high
• 56 metres dia
• 20 metres away
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Controlled Blasting
Concerns related to:
• Horizontal plane within walls
• Vertical wall joints
• Floor joints
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Controlled Blasting
Floor joints were the
main concern
39
Joints were keyed in
and grouted
Hydrophyllic
Seal
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Monitoring Systems
40
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Monitoring Systems
41
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Analysis and Interpretation
42
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Questions
43
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Copyright © Saros (International) Pty Ltd 44
www.saros.com.au
BRISBANE
t: +61 7 3367 3400
3/11 Parkview St
MILTON QLD 4064
Contact Saros for more information:
1300 327 347
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Bird-in-Hand Mine
Geotechnical Engineering
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Introduction
Ben Roache, BAppSci, BEng
Member Engineers Australia
Chartered Engineer, CPEng
Currently the Geotechnical Manager with Mining
One Consultants
About 20 years experience in the mining and civil
industries, covering underground
mining/tunneling, open pit mines and civil
projects
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Geotechnical Engineering - Summary
1. Ground support design
2. Surface subsidence
3. Earthquakes
4. Mine induced seismicity
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Key concepts
Mining method
Ground support
Underground void sizes
Filling of the mine
Subsidence types
Seismicity types
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Ground Support Design
What is ground support?
49
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Ground Support Design
What is ground support?
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Ground Support Design
What do we need it to do?
Maintain a safe work place.
Maintain areas accessible for mining activities.
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Ground Support Design
How do we design it?
Experience – lessons learnt over time.
Understanding the geology and the expected ground
conditions. Every mine location is different.
Empirical techniques. Another experience based
design tool.
Kinematic wedge assessments.
Numerical tools, such as stress assessment computer
programs that can help understand the how the
ground will react around our underground openings.
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Surface Subsidence
There are many causes of ground surface
subsidence, but we will most often experience
change in ground surface level due to:
Excavating a hole and then filling it in, but not
compacting the material.
Seasonal fluctuations in groundwater level.
Sinkholes – always in the news, and usually
associated with geology where materials can wash
away over time with excess water.
Mining induced surface subsidence, such as shaft
collapses or large scale collapse.53
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Old Workings in the Adelaide Hills
There is a significant amount of old mine
workings in the Adelaide Hills.
Old timers didn’t fill many of their mine workings.
Voids were commonly left open.
Shafts were often filled with rubbish or
unconsolidated fill. Often capped poorly with
wooden sleepers.
Can and do fall in naturally.
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Subsidence Examples
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Subsidence Examples
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Subsidence Examples
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Mine Related Subsidence – common types
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Continuous
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Mine Related Subsidence – common types
Discontinuous
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Case Study – Waihi NZ
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Case Study – Waihi NZ
Mining methods – filling as they mine. Corenso
orebody is using a cut and fill mining method,
and has been demonstrated to not cause failure
to surface.
Numerous technical reports available on the
internet on the technical assessment for this
mine.
Mining One acts as a reviewer for the Hauraki
District Council.
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Subsidence - What about BIH?
Mining method is important
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Subsidence - What about BIH?
Extent of void?
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Underground Mining Related Surface
Subsidence at BIH
Key point – there will be only small voids opened
during mining, and left following mining. Fill is
placed as they mine.
The voids left underground with this mining
method will not be able to propagate to surface.
Failed “material bulks and chokes”.
Some of the decline near the surface, following
mining will be rock filled, to avoid the mistakes
made by historical miners. 64
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Natural Earthquakes
We do not expect naturally occurring
earthquakes to impact on the mine, or cause
instability in the mine, or on the surface.
During a 5 year mine life, there is a 10% chance
of exceedance of a 0.0057g earthquake. This is
a minor amount of shaking and not associated
with any damage of structures.
We design the ground support to consider this,
and remain stable.
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Mining Induced Seismicity
The mine is relatively shallow.
The dimensions of the mine are small.
The blast sizes will be small.
The natural energy in the ground around the
mine is not at an intensity for mine induced
seismicity to commence.
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 67
Question and Answers
Presentation on website
Questions to:
Hotline (08) 8536 8010