Tecnologias para o monitoramento de rejeitos – experiência da Fugro no desastre de Bento Rodrigues e desenvolvimentos recentes
Alessander Kormann
Samarco Project - Locations
Source: www.samarco.com/rompimento-de-fundao/
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Samarco Structures – Germano Mine Complex
Germano Mine
complex before
Fundão dam
failure
Setup of Fundão Dam System, early 2015
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Overview of Germano Complex after Dam Failure, 2016
Sela Dike
Tulipa Dike
Baia 3 Dike
Germano Main Dam
Selinha Dike
Germano Buttress Auxiliary Dike
Design Principle of Fundão Dam System
A) Initial design of Fundao-dam system with separation of course grained sands and fine grained suspensions (slimes)
B) Planned layout of Fundao-dam system following upstream method of construction.
Drainage system within sandy tailings
Source: Fundao Tailings dam Review Panel
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Fundão Drainage System, 2008
Source: Fundao Tailings dam Review Panel
Redesign of Drainage with Blanket Drain, 2009
Installation of
1st Blanket Drain for drainage of tailings above an elevation of 826m
Secondary drainage
galleries not working
properly, detected
2010
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Construction of Setback Crest, 2012
Source: Fundao Tailings dam Review Panel
In 2012 it becames evident that secondary drainage gallery at left abutment is out of function.
A setback crest was con- structed and a second blanket drain installed at Plateau elevation 865
Installation of piezometers
in 2014 showing increasing
saturation of the dam, even
above elevation 865
Fundão Dam: Principle Stress Situation
Pore water pressure [u]
Load [Mean Total Stress]
Source: Fundao Tailings dam Review Panel
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Fundão Dam: Process of Failure at Left Abutment
σ efective = σ total - u
u ≥ σ total → σ efective = 0
Principle Stress States, Drained & Undrained
UNSTABLE
STABLE STEADY STATE
SHEAR STRENGTH
(σ1+σ3)/2 [Mean stress]
CONCEPT OF THE COLLAPSE SURFACE (σ1-σ3)/2 [Shear stress]
5
4
3
2 1
STRESS PATHS INHERENT FROM AN INITIALLY STABLE CONDITION (σ1+σ3)/2 [Mean stress]
(σ1-σ3)/2 [Shear stress]
Adapted from: MARTIN & Mc ROBERTS, 2012
STRESS PATH
BEHAVIOUR ON STRESS
ANALYSIS METHOD
1-2-3 Contractive USA
1-4 Contractive ESA
1-4 Dilative ESA
1-5 Dilative USA
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Technologies for Site Characterization and Monitoring of Tailings
• Geotechnical Investigation (Active):
‒ Drilling (rotary and SPT)
‒ CPT
‒ Vane Tests
‒ Seismic CPT
• Geophysical Survey:
‒ GPR
‒ Electrical Resistivity
‒ Magnetometry
• Geotechnical Instrumentation (Passive):
‒ Casagrande Piezometer
‒ VW Piezometer
‒ Water Level Indicator
‒ Inclinometer
• Laboratory:
‒ Earthworks control
‒ Index tests
‒ Advanced tests
Cone Penetration Testing (CPT)
signal cable
connection piece for rod
water proof casing
O-rings
calibrated steel rod with strain gauges Inclinometer
Friction sleeve As = 150 cm² calibrated steel rod
with strain gauges O-rings
Cone Ac = 10 cm²
Penetration of the CPT cone (hydraulic) into the ground with a constant speed of 2 cm/sec
Simultaneous and
continues measurement of the total penetration resistance, which is divided in cone
resistance (q
c) and local sleeve friction (f
s)
Additional parameters
can be measured with
added tools
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CPT – Lithologic Interpretation
Seismic CPT
t = t
0t = t
1t = t
2Δ s
Calculation shear wave velocity
t
2– t
1= Δ t v
s= Δ s / Δ t
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Degradation of Shear Modulus with Increasing Strain
G
0gemessen mit SCPT
Germano: Main Dike and Germano Buttress – Performed Investigations
Service
Before Fundão
Breach
After Fundão
Breach
Drilling (m) 759.28 1476.52 Water level
indicator (unit)
4 6
VW
piezometer 0 16
Casagrande piezometer (unit)
11 35
Inclinometer
(unit) 0 3
CPT (m) 362.94 134.91
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Cava de Germano – Performed Investigations/Measurements
Case Study: Tailing Characterization for Re-mining
CPT based Technology
Deliveres geotechnical data
XRF technology - provides metal concentrations
High resolution – real time
3D modelingof resources for remining
Old tailing for remining / resource estimation
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Typical XRF-CPT profile at Tailing1
CPT-XRF: How it Works
> 1% Cu
Target Horizon
3D Resource Estimation
Metal Distribution within Tailing Body
Metal bearing zone
> 1% Copper
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Gestão de dados regional (130.000 furos de sondagem, 8.000 poços de
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