Block Cave Learning Curve and Considerations as Caves Mine
Deeper and Higher.
Sarah Webster a,*
a
Evolution Mining, Australia
Abstract
The risks in caving can be attributed to multiple source mechanisms. For this reason, evaluating a cave's
success and its critical risks cannot be performed with binary rules alone. An understanding of the variables
of geomechanics in all aspects of design, construction, and operation is required to operate a mine safely.
While Laubscher (2000) set the fundamentals of caving knowledge, the mining method evolving into deeper
footprints and stronger rock masses have brought new challenges. This paper discusses industry-published
cases and learnings from evolving risks with the transitions to the increasing size of crusher chambers,
footprint dimensions and heights of draw, along with ground support scheme quantification and caveability.
This multifaceted challenge is why ongoing research and innovation continue to provide leaps in
understanding how caves behave and how to best design and operate them.
Many learnings have been taken from Northparkes Operations, Australia (Northparkes) who continue to
evolve as the industry learns more about block caving. Examples from E26 and E48 are provided, where
challenges were cave forecasting and reserve recovery, capital investment in infrastructure, cave material
properties and distances from caves to major excavations.
Keywords: mudrush, caveability modelling, ground support, monitoring, case studies
1. Introduction
The mining industry is moving towards methods that have less surface impact, lower cost and are deeper as
surface ore sources are exhausted. Block caving is a solution; however, it comes with significant
considerations, particularly at depth. Operations must be prepared to commit to sometimes more than three
years ahead of ore delivery, higher initial capital funds, and a mining strategy that can withstand cave
establishment and reserve delivery risks. For a greenfield mining site, the parameters required to produce a
bankable feasibility study, without applicable empirical data, can sometimes be difficult to defend. However,
brownfield caving sites, like Northparkes Operations (Northparkes), Australia, benefit from learning from
their past cave performance. As a caving industry, we must learn from each other's operations and address
the challenges as mines move from shallow into higher heights of draw and deeper footprints through
informed engineering commitment.
Block-caving knowledge was founded on comprehensive work, initially at mines where rock masses cave and
fragment readily. Laubscher (2000) indicates that as mines move into large, more competent ore bodies,
there is a need to assess parameters of fragmentation, caveability, draw control design, sequence and ground
support. Additionally, when writing A Practical Mining on Block Caving, there was still so much to be learnt
and discovered, and information from mines to be analyzed and shared.
*
Corresponding author
Email address: sarah.webster@evolutionmining.com
1
The caving community has continued to innovate, collaborate and share learnings, resulting in much
collective knowledge and solutions to caving hazards, some of these key knowledge milestones include
hydrofracturing for caveability (van As and Jeffrey 2000) of air blast modelling (Vejrazka 2016), cave flow
markers (Whiteman et al. 2016), mud rush risk controls (Butcher, Stacey, and Joughin 2005), and coupled
caveability and flow models (Beck, Sharrock, and Capes 2011). The learning trajectory from Laubscher's
original graph extended to the year 2000 and as the industry has required, extrapolation of the caving manual
guidelines beyond the limits originally provided is happening, Figure 1.
Figure 1 Evolution of Challenges, research and Technology in block caving (after Laubscher (2000)).
Northparkes has been cave mining for 27 years and has completed three block caves. E26 lift one is 480m
deep, E26 lift two is 830m deep, and E48 lift one is 581m deep (Figure 2). Each of these caves has a cave
extension constructed at a later stage, and cave columns are an average of 500m in height.
Northparkes has all current reserves at less than 500m depth; however, considering future caves in the
resource category, more than 60% of the material is located beneath 500m depth. A second lift option to E48
caves is possible, as is a third lift at E26, taking it to 1000+ m depth in high-stress conditions. Undoubtedly,
learnings from past Northparkes caves will be used for future designs. With the extensive considerations
required to design and manage multiple lifts and draw columns higher than 800m, new techniques gleaned
from other caving sites are equally important. This paper outlines learnings, opportunities and future
considerations Northparkes has for its deeper caves and discusses some of the critical risks of deep caving.
Figure 2 Oblique section of Northparkes looking ESE.
Provided here is an overview of recent technical challenges and learnings from diverse mining operations, as
they mine larger and deeper block caves. The paper does not cover all risks associated with mining in block
caves in high-stress environments however, the focus is on large excavation spans, extraction level design
trends, ground support for deformation, caveability, and high lift heights. Also provided are innovations that
address the risks of these challenges and some emerging technologies that will continue to keep caving on
the continual learning curve.
2. Major Excavation Size
Block and sublevel caves are bulk underground mining methods. High production rates are traditionally
achieved through conveyor transport rather than trucking, which can be constrained by ventilation and traffic
congestion. Conveyor systems require underground crushers to reduce the fragment size. The chamber
excavated to house a primary crusher is termed a 'large excavation' because the spans are far greater than
those required for regular mine development. Mining at depth comes with greater cost, and increasing
production can mitigate this. Productivity from underground can come from not causing delay or congestion
for load haul dumps and cave production. Ways to increase production are larger bucket sizes and reducing
congestion by maximizing the number of tipping points for crushers. The author notes that near vertical
porphyry caves, typical of Northparkes and Cadia, Australia, locate their crushers on the same level as the
cave extraction level. The distance from the level is a focus of the design. More lateral extensive block caves
and panel caves traditionally locate their crushers beneath the extraction level, and this vertical distance is
considered for induced stress levels and magnitudes beneath the cave.
At higher stress, the risks of large excavations change, and the magnitude of problems can increase. Stress
and shear on structures increase, and the magnitude of seismic events tends to increase. The distance from
other openings, such as the extraction level, must increase as pillars between excavations are subject to
increased stress.
E26 lift one was designed in 1992 with two jaw crushers to process all future production from the
Northparkes caves. When designing E26 lift two, a continuous improvement approach lead to a single hybrid
jaw-gyratory crusher being selected due to its ability to accept a larger feed size, produce a finer product at
a higher rate (Duffield 2000). Savings were achieved as only one chamber needed to be excavated. Caves at
Cadia followed a similar path of starting with a jaw crusher and then transitioning to a jaw-gyratory (Cuello
and Newcombe 2018).
While E26 lift one was not considered high stress, the excavation of the E26 lift two chamber was 350m
beneath lift one, 850m below the surface, and in higher stress conditions. The experience is documented by
Nixon and Weston (2005) which notes that major hazards identified with the excavation were seismic events
with the potential for injury to persons and ground loosening around the crusher chamber. The controls for
these hazards included excavation sequence, ground support tailored to the conditions, re-entry procedures
after firing, QAQC and design verification after installations. The chamber roof spanned 38m x 16m and was
approximately 42m from the cave (Figure 3). The 32 MPa principal stress estimated from hydraulic fracturing
was revised following a hollow inclusion cell stress estimate from the undercut level with an estimated
principal stress of 53 MPa, considerably more than initially estimated.
The crusher chamber and associated feeder station development experienced seismic activity with almost
every round, including overbreak and ejection. During the excavation of the hydroset floor, a 10 kg explosive
blast was performed to remove a section that did not break with the rock hammer. Approximately 10 minutes
after the blast, a seismic event occurred in the crusher chamber, resulting in cracking in the floor concrete
and wall deformation detected by extensometers. Investigations and fault tree risk assessment provided
additional controls to enable excavation to recommence. Actions included the installation of additional cable
bolts into the walls, a two-hour re-entry time for future blasting and, continuous monitoring by the seismic
system and measurement of the extensometers (Nixon and Weston 2005).
38m
12.7m
Figure 3 E26 Lift 2 crusher chamber and ore pass (Nixon and Weston 2005)
Oyu Tolgoi (OT) in Mongolia is one of the more recent block caving provinces, and mining is at more than
1000m in depth. The crusher excavation contains two main chambers connected to each other (Figure 4)
with the arched roof spanning 25m x 21m. OT stand-off distance for the crusher is 280m at 1300m depth
(Sharrock, Ooi, and Baasanjav 2022), and it is noted this is 60m in proximity to a major regional fault
intersecting the cave. In Australia, Ernest Henry's crusher chamber is at 1000m depth, with roof dimensions
of 9.5m wide and 35m long, and it is located 180m from the ore body. Geotechnical drilling into the initially
planned location intersected a large fault zone not previously identified. The crusher location was moved to
a more stable location; however, the proximity to the fault and induced mining stress from the sublevel cave
(SLC) indicated extensive ground support would still be required (Campbell et al. 2013).
Figure 4 Oyu Tolgoi Panel Cave two crusher chamber dimensions (Sharrock, Ooi, and Baasanjav 2022)
E26 Lift One North (E26L1N), a cave extension beneath E26 at Northparkes, constructed a crusher in 2019.
The crusher height needed to be reduced to tie into the existing conveyor system. To achieve this, a reevaluation at the plate feeder resulted in a change to a direct feed geometry onto the top shell and spider
cap as shown in Figure 5 (Cunningham, Melloni, and Greenaway 2023). These enabled areas of the chamber
to be reduced in span and overall volume with a height of 27m. Although high stress was not the motivator
for reducing the size of the excavation, this engineering change and chamber reduction is an example of
where engineering can find solutions when required. This approach may benefit future chambers looking to
reduce excavation dimensions in high-stress.
27m
Figure 5 (a) Section through Northparkes E26L1N Primary Crusher with direct tip (b) oblique view of crusher
spider and tip shell design.
The risks associated with mining large chambers in high-stress environments are mitigated through:


Investigation for determining rock mass, structures and stress conditions
Locating the chamber's sufficient distance outside the induced stress zone




Construction using incremental development cuts. Suorineni (2017) notes that mechanized
excavation in several small steps appears more favourable to seismicity management than single
long or large blasts.
Stages of ground support appropriate for each opening of the excavation
Minimizing excavation size
Ground support and QAQC during installation
Cadia East notes a stand-off distance for critical infrastructure of 110 to 130m dependent on the elevation
(Cuello and Newcombe 2018). Cadia and Codelco, Chile, are using hydrofracturing to manage seismicity in
crusher chamber excavations. The technique is expanded upon more in Section 5.1.
3. Extraction level design
3.1. Extraction level design
Block cave layouts are incrementally improved from one cave mine to the next. Extraction-level layouts of El
Teniente or Herringbone shapes are still typical, and dimensions must consider loads for pillar strength and
geometry orientation at high stress. At the same time, fragmentation can be finer due to stress fracturing,
and the risks of isolated draw/chimneying need to be balanced against reserve recovery.
The draw points and extraction level drive spacings have been trending to larger dimensions at Northparkes
and other caves, as shown in Table 1. At the same time, the smaller spacings derived from Laubscher (2000),
fragmentation-based rules are evolving for harder rock with coarser fragmentation. Advancements in flow
monitoring using markers have improved the understanding and mitigation of isolated draw situations.
Table 1 Extraction level drive spacing from Block Caves
Mine
Cave name
Year
constructed
Drawbell
spacing (m)
Footprint
design
Crusher roof
span (m)
Distance
from cave
Northparkes
E26 Lift 2
1993
14 × 28
Herringbone
33 × 13
50 m
Northparkes
E26 Lift 2
2003
18 × 30
Herringbone
38 × 16
42 m
Northparkes
E48
2010
18 × 30
Herringbone
47 × 13
55 m
Northparkes
E26L1N
2019
18 × 30
El Teniente
45 × 10
45 m
Cadia
Ridgeway
Deeps
18 × 30
(Cuello and
Newcombe
2018)
Herringbone
Cadia
PC1 PC2
20 × 32
(Cuello and
Newcombe
2018)
El Teniente
20 × 30
(Brannon et
al. 2020)
El Teniente
Grasberg
Block Cave
3.2. Extraction speed
The excavation rate of block and sub-level caves directly impacts the financial and seismic response. When
commencing block cave construction, the time to the first draw bell firing and cave production is an important
milestone. Development rates and drawbelling rates are drivers to achieve this. The efficiency of extractionlevel construction design can be improved by increasing the spacing between extraction-level drives (major
pillar) and the drawpoints (minor pillar).
At the same time, the faster the excavation rate, that is, the removal of rock and creation of voids, the less
time the rock has to adjust to the new stress conditions. This is investigated by Suorineni (2017) through
laboratory testing, where loading rates and mining volume excavated rates are evaluated. At high loading or
excavation rates, there is less time allowed for stress redistribution and energy dissipation. This can result in
an aseismic rock being seismic. Laubscher (2000) also noted that the rate of caving impacts seismic activity,
as rapid draw places high-induced stress on the cave back. At El Teniente, Chile, the level of seismic activity
is related to the cave's extraction rate or propagation rate.
Drawbelling rate is a balance between turning over the caving front fast enough not to allow induced stress
to sit for too long, loading the extraction level past peak strength and slowing enough to allow a manageable
rate of stress redistribution during excavation. The drawbelling firing rate needs to commence and ramp up
gradually to be achievable for the underground workforce executing this work. The tasks of drilling, charging,
firing and mining bells are highly specialized, and time is needed to allow the tasks to align into an efficient
marching sequence of peak drawbelling rate.
Sequencing of lead and lags between drawbell firings, undercutting rings, sub-level cave levels, and caving
fronts is important for mitigating excessive induced stress from geometry. Sequencing excavations such as
the undercut ahead or behind the extraction in a level is critical at depth. The advance undercutting
technique has been recommended to ensure a minimum amount of development ahead of the cave front
(Laubscher 2000). Additionally, the undercutting direction should be from weak to strong ground to place
the induced stress onto the higher-strength material and induce fractures. However, if the weaker material
caves preferentially, this area may take off and leave the stronger material. Northparkes experiences
preferential caving of the volcanic units over the monzonite units, and examples from E26 Lift two North
show this caving up in the volcanic units, particularly the geological contact with monzonite the (Talu, van
As, Seloka, et al. 2010).
The balance of draw bell level spacings is made by considering in order of importance:
1) Pillar stability (increase size to address instability)
2) Reserve recovery (decrease size to achieve interactive draw)
3) Economics (increase size to reduce capital cost)
The draw belling rate is made by considering:
1) Induced stress onto pillars
2) Shape and length of undercut front to allow sufficient turnover of the undercut
3) Resources available to turn overdraw bell firings
A cave's rate of advance, through undercutting or cave growth, influences the period that the ground is
subject to induced stress. A balance must be established between fast (not enough time to shed stress) and
slow (stress loading the extraction level pillars past peak strength).
4. Ground Support and Redevelopment
Quantifying the rock mass static and dynamic demand from a ground support scheme must consider a block
cave's high extraction ratio, complex geometry, and sequence. The ground support in the block cave needs
to account for damage from static and dynamic loading during excavation. Additionally, the production draw
schedule, then periods of no draw during mine shutdowns, repeatedly cycles the ground through loaded and
unloaded stress states. Deeper block caves require rock support to be substantial enough for uninterrupted
production. At the same time, construction is to be timely and cost-effective (Kaiser and Moss 2022).
The staged construction tasks create opportunities to schedule ground support installations for stages of high
stress, such as undercutting. Caution should be taken if delaying final ground support until later in the
schedule, as when dealing with major projects and the variable nature of the rock, areas can be missed or
loads incorrectly estimated and ground may be undersupported. Laubscher (2000) summarised this as 'A
consideration for extraction level construction is the installation sequence of the complete ground support
as opposed to the attitude of expediency and convenience'.
Laubscher provided guidelines for low and high-stress conditions, as in Figure 6. Advancements through trials,
research, modelling, and ground support design have built on this work to improve safety and efficiency for
block caving. The demand from the ground support in a block cave needs to consider the stages of:

Development

Undercutting

Cave establishment with oversize

Cave breakthrough

Prolonged years of cave draw, including cycles of shutdown and increased draw

Cave footprint closure
A note on the cave breakthrough stage is when stress concentrated on the vertically growing cave back
breaks through to a void. This change can quickly shed stress back down to the extraction level. This cavinginduced stress may invoke significant seismic events at the extraction level sometime after cave
establishment.
The ground support tools suggested by Laubscher (2000) are still relevant and used in many caves. These
include:

Typical bolts, cables, fibre-reinforced shotcrete and mesh

Welded mesh straps

Tendon straps and cable slings (Figure 7)

Steel arches

Reinforced concrete arches

Shotcrete kerbs at sidewall floor protecting bucket undercutting
Chain link mesh is an additional ground support tool used in areas prone to bursting (Louchnikov, Brown, and
Bucher 2011). Northparkes and industry have tested alternatives to steel arches, such as concrete arches
(Shea 2019) and brow beams, to find a less labour-intensive installation as steel sets can be challenging to
repair when damaged. While some of these alternatives to brow support have their place in short-term draw
points, it is difficult to replicate the robustness of a steel arch.
The evolution of ground support in caves is demonstrated at Codelco, having been in operation since 1905
and mining with the effects of stress since 1976. The work by Valdivia, Munoz, and Landeros Córdova (2023)
shows the changing dynamic rock support systems used in the panel caves (Figure 8). These ground and
surface elements are not specific to caving, as other underground mines that are progressively deepening
and encountering rock-bursting conditions would follow a similar path.
The Canadian Rockburst Support Handbook (Kaiser et al. 1996) provided guidelines for rock support in highstress conditions, and since then, many researchers have built on this work as rockburst data sets expanded
to further the understanding of rock burst mechanisms and ground support schemes, including E et al. (2016),
Heal, Potvin, and Hudyma (2006), Potvin and Hadjigeorgiou (2020). Monitoring technology has allowed the
industry to verify the demand the ground is presenting and research the dynamic capacity of the components
of ground support elements to meet this demand. Kaiser and Moss (2022) provide guiding principles for
deformation-based support design. Under this approach, the installed ground support capacity is reduced as
displacements occur during subsequent excavation stages and mining production and the remaining
deformation capacity in the ground support is required to be tracked. The workflow for this support design
consists of:
1. identifying the vulnerability of excavations to all possible failure modes
2. defining and documenting the engineering design assumptions, dominant design parameters and any
rules for selecting the ground support system
3. estimating the demands on the support and safety margins over the life of the excavation using
applicable calculations, empirical methods and numerical models to establish a safety margin;
4. verifying the design's deformation consumption over the excavation's life.
Kaiser and Moss (2022) note that the detailed design steps are complex and involve iterations and
comparisons of alternatives. It is the author's experience that during the block cave study stages, the draw
bell firing, undercutting timing, scheduling of construction tasks, and mining rates are highly fluid. The
geotechnical engineer needs to be aware of these changes and the impact of sequence on the stress
conditions. Including design change controls and sign-off is an important part of ensuring the ground support
and installation timing remain appropriate.
Figure 6 Low-stress and high-stress support techniques from Laubscher (2000).
Figure 7 Plan view of camel back and bull nose restraint from cables wrapped around and grouted inside
the drawpoint Laubscher (2000).
Figure 8 Main changes in rock support elements used to manage rock bursts at El Teniente. Graph includes
annual rockburst numbers and production tonnes per day (Valdivia, Munoz, and Landeros
Córdova 2023).
4.1. Verification of Deformation accounting for ground support
Modern underground displacement monitoring for convergence of underground excavations allows a far
greater number of data points to measure the rock mass response. Traditional extensometers and
convergence point monitoring have provided very accurate measurements until now but at low densities in
the mine. Determining and acting on the response between these point measurements has been done by
making assumptions from the nearest data point or by making visual observations. This was the case for years
with open pit monitoring relying on prisms. The availability of scanning techniques covering the entire
excavation surface gives a far more accurate picture of the response of the ground, highlighting areas
converging and areas not moving. The ability to calibrate numerical models and understand the extent of
failure and its mechanisms is enhanced when based on orders of magnitude greater quantities of data. As
explained by Kaiser and Moss (2022), the deformation-based support design requires tracking of the safety
factor remaining based on the ground support scheme capacity. Using a laser scanning monitoring technique
to monitor the convergence, while not as sub-millimetre accurate as extensometers or convergence points,
allows more informed decisions on managing ground support rehabilitation across the entire monitoring
area. The deformation-based approach is a proactive ground support rehabilitation one as opposed to
reactive rehabilitation, where re-supporting is made on areas once evidence of plates and bolts failing has
occurred.
4.2. Redevelopment
Deeper and longer-life block caves may experience areas with excessive convergence from areas of failed
pillars performing at their post-peak residual strength. Continuing safe mining in these areas requires
increased geotechnical management to monitor deformation, adjust cave draw control to disperse cave
column loads and tailor rehabilitation ground support. This was the case in areas of E48 in regions that had
experienced high convergence and redevelopment to maintain access. Here, the rock surrounding the drive
has converged and bulking consists of slabs and smaller blocks as a failed rock shell. The failed ground is still
safely retained by the bolts and cable ground support tying it back (Figure 9). Pouring cement plugs into drives
with excessive deformation was used at E48 on two occasions. Redevelopment through a plug requires cycles
of shortcuts and support to reestablish the drive profile. Resin injection was used to consolidate the ground
to enable anchor holes to be drilled and remain open (Brenchley et al. 2013). This acted to penetrate the
defects and voids, filling and re-consolidating broken ground. The redeveloped ground is maintained by a
ground support arch through the broken ground, which resembles the 'Gabion panel' concept (Kaiser and
Moss 2022).
(a)
(b)
Figure 9 (a) Deformed rock mass of a pillar with stress-fractured, failed rock and ground control in the walls
tying back the failed rock regions into solid rock (Kaiser and Moss 2022). (b) example of
rehabilitation ground support from Northparkes E48 Mine EDA, March 2015 (Snyman and Webster
2022).
5. Caveability
Caveability from empirical charts indicates mining spans required for a rock mass to cave naturally after
undercutting. The influence of structural features, variations in rock mass quality, stress, adjacent mining,
water, mining geometries and mining sequence all influence caveability and are not possible to quantify from
charts alone. Additionally, the caveability must be estimated through all units of the cave propagation path
and the variable span of the cave back included in the assessments.
Numerical modelling of cave establishment and growth allows an understanding of cave extents and timing.
The introduction of coupled geomechanical and flow models (Beck, Sharrock, and Capes 2011) allowed the
cave draw schedule to be integrated and the two highly related activities, such as an air gap or swell
buttressing the cave back, to be reflected in the model.
Northparkes caves have experienced varying caveability behaviours including cave stall (Ross and van As
2005), arch over (Talu, van As, Seloka, et al. 2010) and fast caving (Snyman and Webster 2022). With
developments in input data collection and monitoring techniques, there are opportunities to improve
subsequent numerical models, and examples are given in Pfitzner et al. (2010) and Kamp et al. (2022). These
examples show how seismic data can further our understanding of cave growth, by supplementing traditional
open hole and extensometer monitoring with new technology to improve the calibration of numerical
models.
5.1.
Preconditioning for caveability and induced seismicity
Preconditioning is treating the ground through blasting or hydraulic fracturing to reduce the rock mass
strength, providing benefits to caveability and managing seismic magnitude. Preconditioned blasting was
performed on a rib pillar at Mt Charlotte, Australia, to promote yielding on blast fractures rather than
dynamic yielding in a large seismic event (Mikula, Lee, and McNabb 1995). Hydrofracturing was first
performed for caveability at Northparkes in the E26 Lift one block cave (van As and Jeffrey 2000).
Subsequently, Northparkes used hydrofracturing and blasting to promote the caving of the eastern side of
the E26 Lift 2 North extension (Talu, van As, Seloka, et al. 2010) and the E48 ore body, then E48 extensions
(Webster, Snyman, and Samosir 2016). During these projects Northparkes hired the CSIRO equipment and
followed the same methodology, as hydrofracturing is not continuously performed at the mine. Other caving
sites have opted to purchase their own pumps and hydrofracturing equipment and have contracted drilling
companies to perform hydrofracturing at the mine using a technique like CSIRO.
A measure of a hydrofracturing program's success is the number of fractures or total water volume and, thus,
damage that can be induced into the rock mass. This relates to the number and speed at which fractures are
performed, driven by minimizing time when the team is not fracturing. The Northparkes program's pump
rate was in the range of 400 litres per minute, and fractures were performed at 2.5m intervals between
inflated packers. Although there can be benefits in mixing gels for more viscous fluids in fractured regions,
this process increased the time between fracturing and thus reduced the number of fractures performed
each shift. It is concluded that more fractures performed in intact rock create more damage to the rock mass
than fewer fractures using gel.
The Cadia East Underground Project is one of the deepest panel caves in the world, with the first panel (PC1)
located 1,200m below the surface and the second (PC2) 1,450m below the surface. The whole footprint of
these caves was intensively preconditioned with blasting up-holes and hydraulic fracturing down-holes
before the initiation of the cave, as shown in Figure 10 (Catalan, Onederra, and Chitombo 2017b). This
treatment increased caving rates, reduced secondary fragmentation, and enhanced cave draw.
Improvements were also observed in the better control of the magnitude of seismicity from caving-induced
stress.
Figure 10 Section through Cadia East block cave levels with a sequence for intensive preconditioning using
blasting and hydrofracturing (Catalan, Onederra, and Chitombo 2017a).
Codelco have a history of testing and applying hydrofracturing to precondition rock masses at El Teniente
Mine to control mining-induced seismicity near the current infrastructure (Ghazvinian et al. 2020). The
methodology used was the packer method. The application of hydrofracturing has demonstrated an increase
in low-magnitude seismicity, enhanced cave propagation rate, and lowered probability of air blast generation
(Navarrete Vallejos et al. 2022)The area treated is the rock column at least 100m above the level and, in the
selected area, the rock mass below the production level. This aims to create seismic protection for
infrastructure and personnel at the production level.
More recently, hydrofracturing has been performed with larger pumps where the amount of water injected
per fracking interval is far greater. Due to the large equipment size, it has been performed on the surface
rather than in underground locations. This technique, termed 'Plug and Perf', is documented at Cadia by
Amorer et al. (2022) and has been used at other Australian caves to promote cave growth successfully. The
fracturing technique stems from the oil and gas industry and involves installing steel casing into a drill hole,
which is then perforated using shaped explosive charges. The openings created form the initial path for fluid
pumped up to 3,000 litres per minute from the surface. After the duration of fracturing is complete, plastic
'bio-balls' are released from the surface and flow into the frac zone, sealing off the holes. This allows the
water pressure to find the next weakest opening and continue to propagate fractures. The faster pumping
rate and ability to fracture longer intervals make this an efficient method of creating damage to the rock
mass.
6. Lift height, fragmentation, flow and fines generation
The lift height is the height of the caved column of material above the extraction level that is included in the
reserves to be recovered. Higher lift heights involve rock travelling greater distances through the cave
column, resulting in higher comminution and more fines generation. The higher columns containing
unconsolidated and potentially water-bearing cave material also have a greater inrush risk.
6.1. Height of draw and flow
The higher the lift height, the less influence the draw has on the cave back and the greater the risk of dilution
to upper reserves. It was noted at E26 lift 2 North that the draw loses influence on the cave back after around
200m (Talu, van As, Seloka, et al. 2010). For these reasons design heights of draw were typically 500m,
although these are growing with Cuello and Newcombe (2018) noting Cadia caves mining between 1200 to
1400m height of draw (Figure 11).
Figure 11 Caving mines depth, block height and footprint production (bubble size) (Cuello and Newcombe 2018).
Sub-level and block cave flow has been further understood through reduced-scale experiments, models and
full-scale installed markers. Marker trials in block caves started using objects such as painted tyres and
various steel shapes. SLC trials at Kiruna and Grängesberg mines in Sweden, then Ridgeway mine in Australia,
incorporated loading uniquely coded steel tube markers into drill fans within the burden of an unfired SLC
ring (Power 2004). The aim was to understand the granular flow mechanisms, assess interactive draw, and
quantify recovery and dilution. The sophistication of markers improved with the introduction of 'smart
markers' from Elexon Electronics that were again installed in boreholes and had improved recovery of data
as they were able to be read electronically when the material was trammed underneath a detector at the
crusher tipple (Talu, van As, Henry, et al. 2010)These allowed higher numbers to be recovered, and analysis
of the rate of movement through the cave, along with lateral rilling rates into areas of the higher draw, was
possible. The markers were upgraded again with the development of the Elexon Mining Cave Tracker system
that emitted a signal, allowing the position of the beacon to be determined as it moved through the cave
(Whiteman et al. 2016). The data from Cave Tracker beacons was the first full-scale data within the cave,
providing insights into the muckpiles' response to draw.
6.2. Fragmentation
Fragmentation describes the distribution of material sizes presenting to the drawpoints throughout the life
of a cave. Predictions for fragmentation require assessments of the contribution from faults and fractures,
veins, and cemented joints. The cemented features can be overlooked as they are not obviously weak planes;
however, work conducted by Codelco (Brzovic and Villaescusa 2007) indicates that their strength modifies
the rock mass ratings, and careful logging is required.
Quantifying the coarse component, the frequency of hangups, and the oversize is important for ensuring
sufficient resources are allocated for secondary breakage. Laubscher (2000) noted, the flow cone dimensions,
particularly the diameter, are described by a percentage passing fragmentation size, where coarse
fragmentation produces larger, more interactive draw cones.
The caving rules of even draw across the level aim to reduce mixing within the cave column and reduce the
detrimental effects of the uneven draw, such as loading on the extraction level, higher generation of fines,
and funnelling of the draw. If a draw point or localized zone is mined harder than surrounding draw points,
the region above becomes less dense while the surrounding material compacts. With the continual isolated
draw, the area becomes a focus for flow that can fast-track material from higher in the cave, preferentially
over adjacent material. In addition, finer material can flow into voids more readily than larger, coarse
material, making the fine material present earlier in the draw sequence.
Fragmentation can be mapped visually at the draw point; however, it is more accurate to quantify
fragmentation through photogrammetry and laser scanning methods.
6.3. Fines and inrush
The generation of fine material in a block cave occurs due to comminution between rock mobile fragments
and rock fragments and the cave edges. The amount of fines generated is related to the mineralogy of the
rock, its strength, microfractures and veins that contribute to breaking up more quickly, or the degree of
chemical disintegration due to water or oxidation during the caving duration. Time in the cave is also a factor,
and examples of fragmentation from E48 are given in Figure 12 where the early material is coarse and fresh
while later years are finer, grained, and then oxidized. Butcher, Stacey, and Joughin (2005) describes the
breakdown of kimberlite and shale, both containing clay minerals, comminuting in the muck pile and creating
a source of fines for mud from South African mines. This was observed from sampling the porphyry rocks of
E26 at Northparkes after 20 years of caving. It was observed that the low-strength material in the muck pile
had the consistency of stiff clays, and the texture indicated it was part fines and part rock textures that had
weathered since mining had ceased (Webster, Samosir, and Wyllie 2020). Fines can also come from dilution
or surface sources of weathered and oxidized rock. In the early years of a cave, water can drain freely through
the fragmented rock however, as the cave matures and the amount of fines increases, the cave can become
less permeable, and water can be retained within the fragmented ore (Ghadirianniari et al. 2024).
The height of a cave column when using standard tools expressed by Laubscher (2000) was based on studies
of low lifts, less than 200m, where dilution factors are provided up to 300m draw and caves are described to
500m. In weaker ground, cave heights of draw are kept to 200m or less (deWolfe and Ross 2016) to manage
reserve loss from isolated draw columns better. Grasberg Block Cave has an average reserve height of 500m
(Brannon et al. 2020). Mining stronger rock caves are trending to higher heights of draw (Figure 11)
Simultaneously, this can generate more fines due to ore spending a longer time in the cave column. Caves
with vertical orebodies mine subsequently deeper lifts, and they can be exposed to fines generated from
previous cave lifts above them.
The presence of sufficient fines within a cave column can create dry fines inrush events. Where the cave has
a point of entry of water, such as an aquifer, or opens into a water catchment area of an extensive subsidence
zone or an open pit, the mechanism of fines with water must be considered. An example is the Grasberg
Block Cave, one of the largest block caves in the world, below one of the largest open pits, the Grasberg Open
Pit in an area that receives greater than 5 m of rain a year (Brannon et al. 2020)
Butcher, Stacey, and Joughin (2005) note four factors required to trigger a wet inrush event: the holding
capacity of water, the presence of fines forming minerals, a disturbance in the ore column and the inrush
discharge capacity at a drawpoint. The combination of these factors with fines generation, either from weak
ore or high heights of draw combined with a water source accumulating in the cave, poses an increased risk
of wet muck rushes as seen at Cullinan, South Africa (Figure 13 a). Mudrush dynamics in underground mining
are especially complex due to the confinement and stress within the muckpile (Jakubec, Clayton, and Guest
2012). Uncontrolled inrush can result in injury, fatality, damage, dilution, production delays, or mine closure.
(a) 2013
(b) 2020
(c) 2023
Figure 12 E48 Fragmentation from years left to right, 2013, 2020, 2023.
Figure 13 (a) example of a fluid type mudrush from Cullinan. (b) Example of very stiff clay protrusion from
drawpoint at Northparkes mine (Jakubec, Clayton, and Guest 2012).
Grasbergs Deep Ore Zone (DOZ) mine in Indonesia has extensive data sets aiding in analyzing wet inrush
hazards. The draw point classification scheme details the percentage of fines and the water contents, and it
also notes contributing factors of isolated draw and height of draw (Edgar, Prasetyo, and Wilkinson 2020).
Here, the height of draw for the upper case is greater than 200m. Statistical analysis performed at DOZ places
weight on the caving rules of even draw. Here, it was found that with draw rates above 150t/d, spills were
16 times more likely in isolated draw areas compared to even draw areas (Ghadirianniari et al. 2024).
Northparkes has a unique scenario where the surface clay stockpile at Northparkes failed into the subsidence
zone of E26 lift one. This resulted in red clay mixed into the ore that preferentially flowed through narrow
draw zones and reported to draw points (Figure 13 b), causing blockages in the material handling system and
flotation issues in the mill (Webster, Samosir, and Wyllie 2020). The areas where fines and wet material
appear are managed using a Trigger Action Response Plan (TARP) involving mapping clay and fines contents
and moisture observations. Should these values exceed the limits defined in the TARP, drawpoints are mined
remotely. While compaction is not currently a problem with short shutdowns, caves that have ceased
operations are not readily restarted due to compaction over longer closure times.
Northparkes is a relatively dry mine compared to DOZ and, thus, less susceptible to fluid mudrushes. The site
has, however, experienced fines generation as the cave matures, particularly at the cave edges. The examples
in Figure 14 are from the E48 cave edges where dry fines entered from one of the draw points, resulting in a
new fragmentation category being developed, referred to as 'superfine' – baby powder-sized material.
Subsequent fines inrushes occurred in the remaining years of E48 as the height of draw moved towards the
final height of 450m and are almost always located along the cave boundary and/or associated with lithology
contacts and/or geological features (Snyman and Webster 2022). A similar observation is made at Cadia East
Operations, where fine inrushes are termed rill swell events and tend to occur at the boundaries of the cave
back. Cadia manages this risk again through statistical analysis and a mathematical model implemented at
the mine (Lett et al. 2022). The analysis aligns with that seen at DOZ, where influencing factors are the height
of draw, previous inrush events, the proximity to the cave back shape, the extraction rate, and isolated draw.
A statistical analysis approach has also been used at El Teniente to rank the probability of mud entry into the
drawpoints. The wet muck entry input model is represented by the variables of the extraction ratio (height
of draw and in situ primary rock height ratio), percentage of material extracted, fragmentation sizing
threshold, and annual precipitation (Salas et al. 2022).
(a)
(b)
Figure 14 (a) First fines inrush from AS6, Northparkes E48 Block Cave, October 2014, (Snyman and Webster
2022), (b) fines in E48 drawpoint 1N4.
The risk of mud rush at a mine can be assessed by noting the amount of fines generated, the sources of water,
and the triggering energy. Mudrush is more likely after a static period when the muck pile is not kept mobile.
Constantly drawing a cave promotes drainage and prevents fines from settling and accumulating in the cave
column. Additionally, areas of a cave mined preferentially result in zones of low-density material that fine
fractions can migrate into (Jakubec, Clayton, and Guest 2012). A triggering event can be vibration from
blasting or mining equipment, excess pressure from rising water levels, or new material collapse onto the
mud.
Considering block caves are mined at increasing heights of draws, exceeding 500m, and from multiple lifts, it
is imperative that risk management continue to understand and manage these risks.
7. Future emerging innovations to address challenges
Reflecting on the foundation work in block caving from Laubscher (2000) and the progress from researchers,
caving operations, suppliers, and collaborative caving studies has continuously provided distinct progress in
understanding caving mechanisms. In this section, emerging technologies are discussed.
7.1. Cave back mapping
The cave back has been defined from drill holes where the back is observed via camera or extensometers
installed as monitoring. The data point from a hole represents a small part of the cave surface, and the surface
needs to be interpreted between data points.
The introduction of optical fibre monitoring of cave backs has allowed higher resolution strain monitoring
within boreholes. The optical fibre installation is no more complex than other hole monitoring installations;
however, a limitation is that an abundance of data has been produced that needs to be stored, postprocessed, and used for decisions and action. Industry will need to adapt to manage these large data sets
and create thresholds for responding to the changes revealed in the data. Examples of this monitoring are
from Silixa (Furlong and Anderson 2022) and an example from monitoring at Carrapateena SLC is available
from Poulter et al. (2022). The ability to measure the cave back and have high-resolution strain values of the
ground from the failed edge through the seismic zone into intact rock provides a great opportunity to
understand the mechanisms and depth of the cave's influence.
Furthering the ability to understand the cave back is Muon tomography technology. This form of monitoring
infers density by measuring the attenuation of cosmic ray muons from the upper atmosphere as they
penetrate the earth. The measurement of the flux arriving at certain directions by the detectors situated
underground are used to reconstruct a 3D model of the underground density (Schouten 2018b). Muon-based
geophysics investigates mineral exploration near existing mines, oil and gas reservoirs, and block cave
monitoring. The creation of cave shape based on density has numerous benefits to cave management,
calibration of numerical models, and reconciliation of reserves. At the time of writing case studies are being
published and current examples are; Schouten (2018a), Hivert et al. (2016) Lechmann et al. (2021).
7.2. Coupled cave flow, caveability, hydrology modelling
The ability to couple the geomechanical and particle flow codes in a caveability numerical model provided a
tool for managing caveability where cave loads are incorporated into the model, which is essential for
forecasting cave behaviour and managing production (Beck, Sharrock, and Capes 2011). Further work has
coupled these models with the hydrological influences to understand the flow paths and the effects of fluid
pressure on the geomechanical model (Flatten and Beck 2016). The coupled nature of the numerical models
allows a better replication of the complex mechanisms influencing block caves.
7.3. Flow modelling with fragmentation monitoring results
The abundant data generated from the technology of ore body knowledge, flow paths and fragmentation
sizings produced through the life of the cave poses a great opportunity for back analysis of caves. This could
provide caving studies with numerous projects to account for the range of caving results we see.
8. Conclusion
Caving is the lowest operating cost underground mining method, provided that draw point spacing, draw
point size and ore handling facilities are designed to suit the caved material and that the draw point horizon
is maintained for the draw life (Laubscher 2000). The mining method depends on the rock mass
characteristics, and as rock mass varies, so does caving success. The multifaceted mechanisms of strength,
stress, structure, geometry, excavation rates, draw strategy, flow, fragmentation, and water make designing
and operating caves safely a complex approach. The caving community has continued to learn from each
other and innovate to understand these variables. Caving continues to provide areas of steep learning
milestones into the future.
9. References
Amorer, Gabriel, Stephen Duffield, Jared De Ross, and Gisela Viegas Fernandes. 2022. "Surface hydraulic
fracturing trial at Cadia East." In Caving 2022: Fifth International Conference on Block and Sublevel
Caving, 1173-88.
Beck, D.A, G. Sharrock, and G Capes. 2011. "A coupled DFE-Newtonian Cellular Automata scheme for
simulation of cave initiation, propagation and induced seismicity." In 45th US Rock Mechanics /
Geomechanics Symposium San Francisco,: US Rock Mechanics / Geomechanics Symposium.
Brannon, Charles, D. Beard, Nicholas Pascoe, and Anton Priatna. 2020. "Development of and production
update for the Grasberg Block Cave mine – PT Freeport Indonesia." In MassMin 2020: Proceedings of
the Eighth International Conference & Exhibition on Mass Mining, 747-60.
Brenchley, Paul, Linda Snyman, Jogi Samosir, and Bonnie Coxon. 2013. "Redevelopment support at
Northparkes Mines." In Proceedings of the Seventh International Symposium on Ground Support in
Mining and Underground Construction, 451-60.
Brzovic, A, and E Villaescusa. 2007. 'Rock mass characterization and assessment of block-forming geological
discontinuities during caving of primary copper ore at the El Teniente mine, Chile', International
Journal of Rock Mechanics and Mining Sciences, 44: 565-83.
Butcher, R, T Stacey, and W Joughin. 2005. 'Mud rushes and methods of combating them', Journal of the
Southern African Institute of Mining and Metallurgy, 105: 817-24.
Campbell, Alexander, Charles Lilley, Samir Waters, and Paul Jones. 2013. "Geotechnical analysis and ground
support selection for the Ernest Henry crusher chamber." In Proceedings of the Seventh International
Symposium on Ground Support in Mining and Underground Construction, 437-50.
Catalan, A, I Onederra, and G Chitombo. 2017a. 'Evaluation of intensive preconditioning in block and panel
caving – Part I, quantifying the effect on intact rock', Mining Technology: 1-12.
———. 2017b. 'Evaluation of intensive preconditioning in block and panel caving – Part II, quantifying the
effect on seismicity and draw rates', Mining Technology: 1-19.
Cuello, David, and Geoffrey Newcombe. 2018. "Key geotechnical knowledge and practical mine planning
guidelines in deep, high-stress, hard rock conditions for block and panel cave mining." In Proceedings
of the Fourth International Symposium on Block and Sublevel Caving, 17-36.
Cunningham, R, S Melloni, and M Greenaway. 2023. "E26 Lift 1 North block cave development and
construction." In Underground Operators Conference AusIMM.
deWolfe, C., and I. Ross. 2016. "Super Caves – Benefits, Considerations and Risks." In Seventh International
Conference and Exhibition on Mass Mining. Sydney: AusIMM.
Duffield, S. 2000. "Design of the second block cave at Northparkes E26 Mine." In Proceedings of MassMin.
AusIMM.
E, Villaescusa, A De Zoysa, J Player, and A Thompson. 2016. "Dynamic Testing of Combined Rock Bolt and
Mesh Schemes." In Seventh International Conference and Exhibition on Mass Mining. Sydney.
Edgar, I., R. Prasetyo, and M. Wilkinson. 2020. "Deep Ore Zone mine wet ore mining empirical learnings,
mining process evolution and development pathway." In MassMin 2020: Proceedings of the Eighth
International Conference & Exhibition on Mass Mining, 385-93.
Flatten, A, and D Beck. 2016. "Applications of hydro-mechanically coupled 3D mine and reservoir scale,
discontinuous, strain-softening dilatant models with damage." In 49th US Rock Mechanics /
Geomechanics Symposium. San Francisco.
Furlong, Jon, and Zara Anderson. 2022. "Distributed acoustic sensing/distributed strain sensing technology
and its applications for block cave progress monitoring, rock mass preconditioning, and imagining."
In Caving 2022: Fifth International Conference on Block and Sublevel Caving, 991-1006.
Ghadirianniari, Sahar, Scott McDougall, Erik Eberhardt, Jovian Varian, Karl Llewelyn, Ryan Campbell, and Allan
Moss. 2024. 'Statistical analysis of the impact of ore draw strategies on wet inrush hazard
susceptibility in a panel cave mine', International Journal of Rock Mechanics and Mining Sciences,
174.
Ghazvinian, Ehsan, Branko Damjanac, Loren Lorig, Patricio Cavieres Rojas, and Antonio Madrid. 2020. "Back
analysis of the effect of hydraulic fracturing preconditioning on mining-induced seismicity at the main
access of New Mine Level project, CODELCO Chile - El Teniente Division." In MassMin 2020:
Proceedings of the Eighth International Conference & Exhibition on Mass Mining, 249-63.
Heal, D, Y Potvin, and M Hudyma. 2006. 'Evaluating Rockburst Damage Potential in Underground Mining',
The 41st U.S. Symposium on Rock Mechanics (USRMS): "50 Years of Rock Mechanics - Landmarks and
Future Challenges.", held in Golden, Colorado, June 17-21, 2006.
Hivert, Fanny, Ignacio Lázaro Roche, Jean‐Baptiste Decitre, Jürgen Brunner, José Busto, and Stéphane Gaffet.
2016. 'Muography sensitivity to hydrogeological rock density perturbation: roles of the absorption
and scattering on the muon flux measurement reliability', Near Surface Geophysics, 15: 121-29.
Jakubec, J., R. Clayton, and A. Guest. 2012. "Mudrush Risk Evaluation." In MassMin 2012 Combined
Proceedings.
Kaiser, P. K., and A. Moss. 2022. 'Deformation-based support design for highly stressed ground with a focus
on rockburst damage mitigation', Journal of Rock Mechanics and Geotechnical Engineering, 14: 5066.
Kaiser, P.K., D.R. McCreath, D.D. Tannant, Université laurentienne de Sudbury. Geomechanics Research
Centre, and Canadian Rockburst Research Program. 1996. Canadian Rockburst Support Handbook
(Geomechanics Research Center).
Kamp, Corey, Amanda Conley, David Collins, Mike Preiksaitis, Tony Butler, and Vladimir Shumila. 2022. "Use
of seismic tomography to aid rock mechanics interpretation at New Afton B3 block cave mine." In
Caving 2022: Fifth International Conference on Block and Sublevel Caving, 461-72.
Laubscher, D. 2000. 'A Practical Manual on Block Caving', International Caving Study (1997-2000).
Lechmann, Alessandro, David Mair, Akitaka Ariga, Tomoko Ariga, Antonio Ereditato, Ryuichi Nishiyama, Ciro
Pistillo, Paola Scampoli, Fritz Schlunegger, and Mykhailo Vladymyrov. 2021. 'Muon tomography in
geoscientific research – A guide to best practice', Earth-Science Reviews, 222.
Lett, James, Raul Castro, M. Pereira, Arvic Osorio, and Pablo Alvarez. 2022. "BCRisk applications for rill swell
hazard analysis in PC1: case study at Cadia East Operations." In Caving 2022: Fifth International
Conference on Block and Sublevel Caving, 561-72.
Louchnikov, V, S Brown, and R Bucher. 2011. "Fast, Safe and Fully Mechanised Installation of High-Tensile
Chain-Link Mesh for Underground Support." In 11th Underground Operators Conference. Canberra:
AusIMM.
Mikula, P., M Lee, and K. McNabb. 1995. 'The preconditioning and yielding of a hard rock pillar at Mt Charlotte
mine', 8th International Society for Rock Mechanics Congress, ISRM 1995.
Navarrete Vallejos, Rodrigo, Cristian Soto Perez, F. Henriquez, and H. Godoy. 2022. "Hydraulic fracturing in
the construction of Andes Norte Project." In Caving 2022: Fifth International Conference on Block and
Sublevel Caving, 1227-40.
Nixon, J, and A Weston. 2005. "Excavation of the Lift 2 Crusher Hydroset Chamber and Orepass in Seismically
Active Conditions at Northparkes Mines." In Ninth Underground Operators’ Conference. AusIMM.
Pfitzner, MJ, E Westman, M Morgan, D Finn, and DA Beck. 2010. "Estimation of rock mass changes induced
by hydraulic fracturing and cave mining by double difference passive tomography." In Second
International Symposium on Block and Sublevel Caving, edited by Y Potvin. Perth: Australian Centre
for Geomechanics.
Potvin, Y, and J Hadjigeorgiou. 2020. Ground support for underground mines (Australian Centre for
Geomechanics).
Poulter, Mollie, Tessa Ormerod, Glen Balog, and David Cox. 2022. "Geotechnical monitoring of the
Carrapateena cave." In Caving 2022: Fifth International Conference on Block and Sublevel Caving,
487-500.
Power, G. 2004. 'Full scale SLC draw trials at Ridgeway Gold Mine', Massmin 2004, Santiago Chile.
Ross, I, and A van As. 2005. 'Northparkes Mines — The Design, Sudden Failure, Air-Blast and Hazard
Management at the E26 Block Cave', Ninth Underground Operators’ Conference.
Salas, O., Raul Castro, Eduardo Viera, K. Basaure, Felipe Hidalgo, and M. Pereira. 2022. "Modelling of wet
muck entry at El Teniente for long-term planning." In Caving 2022: Fifth International Conference on
Block and Sublevel Caving, 545-60.
Schouten, D. 2018a. 'Muon geotomography: selected case studies', Philos Trans A Math Phys Eng Sci, 377.
Schouten, D. 2018b. 'Muon Geotomography: A Novel, Field-Proven 3D Density Imaging Technique for Mineral
Exploration and Resource Monitoring ', Canadian Society of Exploration Geophysics, CSEG Recorder,
43.
Sharrock, Glenn, Jun Ooi, and Baatarzorigt Baasanjav. 2022. "Geotechnical analysis and ground support
selection for the Oyu Tolgoi Crusher Chamber #2." In Caving 2022: Fifth International Conference on
Block and Sublevel Caving, 227-40.
Shea, Neil. 2019. "The evolution and performance of the Henderson Mine’s C-arch shotcrete drawpoint
support." In Proceedings of the Ninth International Symposium on Ground Support in Mining and
Underground Construction, 267-76.
Snyman, Linda, and Sarah Webster. 2022. "Northparkes E48 block cave: the mining history of a successful
block cave." In Caving 2022: Fifth International Conference on Block and Sublevel Caving, 95-108.
Suorineni, Fidelis. 2017. "Myths of deep and high stress mining — reality checks with case histories." In
Proceedings of the Eighth International Conference on Deep and High Stress Mining, 843-60.
Talu, S, A van As, R Henry, J Hilton, and D Whiteman. 2010. 'Installing of Smart Markers to Monitor Lift2NE
Ore Flow Behaviour', Y Potvin (ed.), Caving 2010: Proceedings of the Second International Symposium
on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 623-631.
Talu, S, A van As, W Seloka, and R Henry. 2010. 'Lift 2 North extension cave performance', in Y Potvin (ed.),
Caving 2010: Proceedings of the Second International Symposium on Block and Sublevel Caving,
Australian Centre for Geomechanics, Perth, pp. 407-421,.
Valdivia, Eduardo, Alejandro Munoz, and Pedro Landeros Córdova. 2023. "Evolution of dynamic rock support
systems at the El Teniente mine." In Ground Support 2023: Proceedings of the 10th International
Conference on Ground Support in Mining, 129-40.
van As, A, and R Jeffrey. 2000. 'Hydraulic fracturing as a cave inducement technique at Northparkes Mines',
The Fourth North American Rock Mechanics Symposium.
Vejrazka, C. 2016. "Northparkes Mines’ Current Air Blast Risk Assessment Practices for Block Caving
Operations." In Seventh International Conference and Exhibition on Mass Mining. The Australasian
Institute of Mining and Metallurgy.
Webster, S., L. Snyman, and J. Samosir. 2016. "Preconditioning E48 Cave Extension Adjacent to an Active
Cave." In Seventh International Conference on Mass Mining. Sydney.
Webster, Sarah, Eddy Samosir, and Angus Wyllie. 2020. "Learnings from mining cave extensions at
Northparkes Mines and new technology to improve the value of future cave designs." In MassMin
2020: Proceedings of the Eighth International Conference & Exhibition on Mass Mining, 92-102.
Whiteman, D, S Talu, M Wilson, G Watt, A van As, and P Kuiper. 2016. 'Cave Tracker Flow Monitoring System
Installation at Argyle Diamond Mine', SEVENTH INTERNATIONAL CONFERENCE & EXHIBITION ON
MASS MINING.