tailings by sm ajon
TRANSCRIPT
-
8/6/2019 Tailings by SM Ajon
1/35
By Sarah Mae B. Ajon
-
8/6/2019 Tailings by SM Ajon
2/35
consist of ground rock and process effluentsthat are generated in a mine processing plant
mechanical and chemical processes are used
to extract the desired produ
ct from the runof the mine ore and produce a waste stream
waste product that has no financial gain to amineral operator at that particular point intime
The disposal of tailings is commonlyidentified as the single most importantsource of environmental impact for manymining operations
-
8/6/2019 Tailings by SM Ajon
3/35
a final storage area where unrecoverable anduneconomic metals, minerals, chemicals,
organics and process water are discharged
-
8/6/2019 Tailings by SM Ajon
4/35
CONVENTIONALIMPOUNDMENT
BACKFILLOFTAILINGSTOUNDERGROUND
WORKINGS
IN-PITTAILINGSSTORAGE
-
8/6/2019 Tailings by SM Ajon
5/35
surface retaining structure designed to store
both tailings and mine water, with the aim of
reclaiming the water for use in the
processing plant as required two types of surface impoundments:
1. Water Retention Type Dam
2. Raised Embankment
-
8/6/2019 Tailings by SM Ajon
6/35
used for mineral operations that plan to
store high volumes of water
Water storage may be required to keep a
processing plant operational during the dryseason or where surface water inundation
can occur especially if the impoundment is in
a catchment area.
-
8/6/2019 Tailings by SM Ajon
7/35
most common construction technique used
in tailings storage facilities
most common materials used for
embankment raises are waste mine rock,natural borrow soils, underground roadway
development material, cycloned tailings
(coarse fraction) and hydraulically deposited
tailings three principal designs are upstream,
downstream and centreline structures
-
8/6/2019 Tailings by SM Ajon
8/35
-
8/6/2019 Tailings by SM Ajon
9/35
lowest initial cost and most popular design
most common design to fail
key failure mode of upstream embankments
is a static/transient load inducedliquefaction flowslide event
suited to areas where the climate is arid
not suited to areas of seismic activity
Excessive rates of rise (of upstreamembankments) is the underlying cause for
many upstream tailings impoundment
failures
-
8/6/2019 Tailings by SM Ajon
10/35
-
8/6/2019 Tailings by SM Ajon
11/35
developed to reduce the risks associated
with the upstream design, particularly when
subjected to dynamic loading as a result of
earthquake shaking very versatile for a range of site specific
design parameters and behaves similarly to
water retention dams
main advantage is that the downstreamdesign can have unrestricted heights
main disadvantage is the cost of raising theembankment
-
8/6/2019 Tailings by SM Ajon
12/35
-
8/6/2019 Tailings by SM Ajon
13/35
a compromise between both the upstream
and downstream designs
more stable than the upstream method but
does not require as much constructionmaterial as the downstream design
When subsequent raising is required,
material is placed on both the tailings and
the existing embankment cannot be used as a large water retention
facility cannot be used as a large waterretention facility
-
8/6/2019 Tailings by SM Ajon
14/35
-
8/6/2019 Tailings by SM Ajon
15/35
STORED BELOW GROUND IN PREVIOUS WORKED OUTVOIDS
MIXED WITH A BINDER,USUALLY CEMENT,AND THEN
PUMPED UNDERGROUND TO FILL VOIDS AND HELP
SUPPORT AN UNDERGROUND MINE
-
8/6/2019 Tailings by SM Ajon
16/35
-
8/6/2019 Tailings by SM Ajon
17/35
-
8/6/2019 Tailings by SM Ajon
18/35
1. THE TAILINGS ARE STORED UNDERGROUND AND THUSPREVENT SURFACE DISTURBANCE.THIS IS MOREENVIRONMENTALLY FRIENDLY AS AREAS OF LAND
DONT HAVE TO BE USED FOR A SURFACE TAILINGSSTORAGE AREA.
2. ORE RICH PILLARS AND SUPPORTS CAN BE
EXTRACTED.
3. THE BACKFILL HELPS TO SUPPORT THE MINE
-
8/6/2019 Tailings by SM Ajon
19/35
4. BACKFILL REDUCES THE RISK OF ROCK BURSTSOCCURRING AS PRESSURES ARE NOT FOCUSED ON
PILLARS AND SUPPORTS.
5. IMPROVES THE VENTILATION CIRCUIT IN THE MINE.
6. PREVENTS ROOF FALLS FROM BLASTING (AIR OVERPRESSURE (AOP))
7. BINDERS HELP TO MINIMISE GROUNDWATERCONTAMINATION
-
8/6/2019 Tailings by SM Ajon
20/35
1. HIGH COSTS,PARTICULARLY IF BINDERS ARE USED.
2. THE TAILINGS NEED TO BE DEWATERED,
INCREASING COSTS.
3. HOLD UPS IN EXTRACTION STRATEGIES.
4. RISKS OF LIQUEFACTION OF THE TAILINGS IFSATURATION LEVELS ARE HIGH,AND A TRIGGER(SEISMIC VIBRATION)ARE PRESENT.
-
8/6/2019 Tailings by SM Ajon
21/35
5. SEEPAGE OF TAILING EFFLUENT INTOGROUNDWATER,THUS CONTAMINATION.
6. EXTRA MANPOWER AND EQUIPMENT.
7. ORE DILUTION FROM POOR QUALITY FILLS.
-
8/6/2019 Tailings by SM Ajon
22/35
process of backfilling abandoned open pit
surface mines with tailings
worked out voids can be filled at a fraction
of the costs the tailings do not require retaining walls,
thus the risks associated with embankment
instability are eliminated
main disadvantage to in-pit storage oftailings is that the potential for
groundwater contamination below andaround the void can be very significant
-
8/6/2019 Tailings by SM Ajon
23/35
-
8/6/2019 Tailings by SM Ajon
24/35
1. Rapid rates of rise occur particularly in theearly stages of deposition when the pit is at its
deepest and the exposed surface area the
smallest.
2. The stability of underground mines in the
vicinity to an in-pit tailings facility may bejeopardised.
3. Poor consolidation can result in long durations
of surface deformation after a pit has beenfilled.
4. Groundwater bores will have to be installed
around the pit to monitor the seepage plumes.
-
8/6/2019 Tailings by SM Ajon
25/35
Problems arise when accelerated weathering
process generates toxic levels that createshort and long term tailings management
challenges. Example: Acid Mine Drainage/Acid Rock
Drainage - acid generation and metal
mobilisation occur that eventually find their
way into the surrounding environmentthrough runoffor seepage
-
8/6/2019 Tailings by SM Ajon
26/35
The design of a tailings storage facility
should therefore be optimised to preventweathering and the mobilisation of
contaminants, whilst also increase thedegradation rates of reagents stored in the
tailings facility.
It may be more economical to hold water for
longer periods of time to allow naturaldegradation of reagents rather thanpromoting rapid degradation.
-
8/6/2019 Tailings by SM Ajon
27/35
In the Philippines, there is really no detailed
and specific regulatory legislation relatingto tailings management
Each mine has an EnvironmentalCompliance Certificate (ECC) thatessentially reinforces the prevention of
impacts to the environment from a tailings
facility.
-
8/6/2019 Tailings by SM Ajon
28/35
(From: Guidelines for miners: tailings andtailings storage facilities in South Australia)
1. Site and tailings characterisation
2. Identification of potentialimpacts/hazards
3. Development of controls for identifiedimpacts/hazards and estimation of
residual risk4. Documentation
-
8/6/2019 Tailings by SM Ajon
29/35
involves a comprehensive description of theenvironment, location and relevantfeatures of the proposed location
is a progressive process.Information is required in respect of:
the local community
land use
proximity to housing and infrastructure
amenity
noise, dust and air quality
topography and landscape
climate
-
8/6/2019 Tailings by SM Ajon
30/35
geohazards
hydrology
groundwater
vegetation, weeds and plant pathogens
fauna
topsoil and subsoil
heritage proximity to conservation areas
pre-existing site contamination and
disturbance
-
8/6/2019 Tailings by SM Ajon
31/35
Particular attention needs to be paid to:
1. geographic location of the proposed site
2. Chemical, radiological and physicalcomponents of the tailings
3. Where a tailings dam is to hold radioactive
waste, baseline radiological conditions
need to be determined prior toconstruction
-
8/6/2019 Tailings by SM Ajon
32/35
May include impacts on or hazards to:
surface, ground and nearby marine waters
air quality
flora and fauna
humans, such as amenity, public safety,
health and wellbeing
post mining land use including on adjacent
properties
-
8/6/2019 Tailings by SM Ajon
33/35
This stage should include:
optimal tailings management methods
tailings delivery
tailings containment design, construction,operation and decommissioning
management of odour, dust and gasemissions
opportunities for underground or open pit
backfilling
closure and post closure issues
-
8/6/2019 Tailings by SM Ajon
34/35
Site characterisation, the development of
controls for identified impacts/hazards and
estimation of residual risk are to be
documented consistently.
-
8/6/2019 Tailings by SM Ajon
35/35
Thanks for Listening!!