Download Impacts of climate change on contaminated land and containment

Climate Change Impacts on the
Physical and Mechanical
Performance of Stabilised/Solidified
Contaminated Soil
Sinéad Smith and Abir Al-Tabbaa
Cambridge University
29th – 31st May 2007
Outline of presentation
 Background
 Laboratory
experiments
 Experimental results
 Conclusions
 Background
 Laboratory
experiments
 Experimental results
 Conclusions
Background

SUBR:IM


Containment systems



S/S remediation suitable for highly contaminated sites
Dual physical and chemical process
Climate change predictions



Context of research within larger consortium
UK Climate Impacts Programme (UKCIP 02)
+4°C by 2080, rainfall -60% (summer) and +40% (winter)
Expected impacts

Cyclic wet/dry and freeze/thaw conditions cause deterioration
including strength loss and contaminant leachability increase
 Background
 Laboratory
experiments
 Experimental results
 Conclusions
Laboratory experiments
Summary
 Laboratory
climate scenarios based on
UKCIP 02


Temperature
Rainfall
 Parameters




under investigation
Water content
Physical observations
Permeability
Unconfined compressive strength (UCS)
Laboratory climate scenarios
Temperature
Year
Summer
Winter
20°C
20°C
2050
27°C
-2°C
2080
31°C
0°C
Current climate
(control conditions)
Laboratory climate scenarios
Rainfall
A/B
Scenario
Summer
Winter
Dry summer
Dry with no water
recharge
A: Fully immersed
in water (Flooded)
B: Maintained at its
natural water
content (Saturated)
C/D
Control
Intermittent
summer rainfall
Alternate weeks dry
(40% RH) then
recharged (100% RH)
Constant 100% RH
C: Flooded
D: Saturated
Laboratory soil samples
Systems
S/S systems
Code
Uncontaminated
SSUS
Contaminated
SSCS
Aged, uncontaminated
ASSCS
Aged, contaminated
ASSUS
Laboratory soil samples
Composition

Samples


Soil: Made ground



45% gravel, 15% sand, 20% silt, 20% clay
20% water content
Grout:



Ø 100 mm, h 100 mm or 50 mm
10: 1 OPC: bentonite
1.6: 1 dry grout: water
Contaminants:


Pb 2801 mg/kg
Cu 1264 mg/kg
3.7: 1 soil: grout
Laboratory soil samples
Accelerated ageing

Equivalent age calculated based on ‘activation energy’ concept

Activation energy (Ea ) defines temperature sensitivity of the hydration
process of a particular cementitious mix
t
te   e

Ea  1 1
 
R  T T0
0




t
te
Δt
T
T0
R
Equivalent age
Curing period (10 months)
Curing temperature (60°C)
Ambient temperature (20°C)
Universal gas constant (8.31 J/ mol.K)
Equivalent ages


ASSUS
ASSCS
te = 26 years
te = 14 years
 Background
 Laboratory
experiments
 Experimental results
 Conclusions
Experimental results
Summary
 Physical
observations
 Water content
 Permeability
 Unconfined compressive strength (UCS)
Physical observations

Control


No change
SSCS B (2080)
Dry summer (A/B)

1st summer: SSCS damaged
(2080>2050), SSUS undamaged
1st Summer

1st winter: SSUS A (2050) severely
damaged but negligible damage to A
(2080) and B (2050, 2080); SSCS
damaged further
1st Winter
SSUS A (2050)
1st Winter
Physical observations

Intermittent summer rainfall (C/D)


1st
summer: Fine hairline cracks
appeared
SSUS C (2080)
1st winter: C (2080) severely damaged
but negligible damage to D (2080)
1st Summer

Aged, intermittent summer rainfall
(D)


Similar physical damage as unaged
system
Physical damage to ASSCS identical to
ASSUS
1st Winter
Water content

20%
Dry summer (A/B)
Water content reduces to
3% after 4 to 6 weeks
Water content (%)

SSUS, 2080A
SSUS, 2080B
SSUS, Control
15%
10%
5%
0%
0

Intermittent summer
rainfall (C/D)
Water content fluctuates
between 7% and 19%
10
Time (months)
15
20
SSUS A/B (2080)
20%
Water content (%)

5
SSUS, 2080C
SSUS, 2080D
15%
10%
5%
0%
0
5
SSUS C/D (2080)
10
Time (months)
15
20
Water content

Contaminated, dry
summer (A/B)
SSCS similar to SSUS
20%
Water content (%)

15%
10%
SSCS, 2080B
SSCS, 2050B
SSCS, Control
5%
0%

Aged, intermittent
summer rainfall (D)
0
5
10
Time (months)
15
20
SSCS A/B (2050, 2080)
20%
Higher water content (9% 14%) than unaged system
(7%)
 Contaminants prevent
moisture loss in dry week
Water content (%)

15%
10%
5%
ASSUS, 2080D
ASSCS, 2080D
0%
0
1
2
Time (months)
3
ASSUS & ASSCS D (2080)
4
5
Permeability
Dry summer (A/B)
Permeability (m/s)

1.E-05

SSUS, 2050A
SSUS, 2050B
SSUS, Control
1.E-06
1.E-07
2050: Large increase (2 to
1.E-08
3 orders of magnitude)
1.E-09
after 1st summer
1.E-10
 No visible damage
1.E-11
 Smaller changes thereafter
0
for saturated case
 Higher value for flooded
SSUS
case after 1st winter
5
10
Time (months)
15
A/B (2050)
2080: Similar to 2050,
fluctuations demonstrate
sensitivity to crack patterns
Permeability (m/s)
1.E-05

20
SSUS, 2080A
SSUS, 2080B
SSUS, Control
1.E-06
1.E-07
1.E-08
1.E-09
1.E-10
1.E-11
0
5
SSUS A/B (2080)
10
Time (months)
15
20
Permeability


Intermittent summer
rainfall (C/D)
Similar to dry summer
(A/B), large increase (2 to
3 orders of magnitude)
after 1st summer
No apparent effect of
visible cracks

Small changes thereafter
for saturated case

Highest value for flooded
case after 1st winter
1.E-05
Permeability (m/s)

SSUS, 2080C
SSUS, 2080D
SSUS, Control
1.E-06
1.E-07
1.E-08
1.E-09
1.E-10
1.E-11
0
5
SSUS C/D (2080)
10
Time (months)
15
20
Permeability

Similar trend for SSCS as
SSUS but 1 order of
magnitude higher
 Large increase after 1st
summer (2 orders of
magnitude) then constant


Aged, intermittent
summer rainfall (D)
Both ASSUS and ASSCS
gradually increase 1 order
of magnitude
 Opposite trend –
contaminants reduce
permeability by 1 order of
magnitude
1.E-05
Permeability (m/s)
Contaminated, dry
summer (A/B)
1.E-06
1.E-07
SSCS, Control
SSCS, 2080B
SSCS, 2050B
1.E-08
1.E-09
1.E-10
1.E-11
0
5
10
Time (months)
15
20
SSCS A/B (2050, 2080)
1.E-05
ASSUS, 2080D
ASSCS, 2080D
1.E-06
Permeability (m/s)

1.E-07
1.E-08
1.E-09
1.E-10
1.E-11
0
5
10
Time (months)
ASSUS & ASSCS D (2080)
15
20
Unconfined Compressive Strength
Control

Generally constant but
high variability (crack
patterns?)
10
SSUS, Control
8
UCS (MPa)

6
4
2
Dry summer (B) and
intermittent summer
rainfall (D)

Generally lower than
control
0
5
10
15
20
Time (months)
SSUS Control
10
SSUS, 2080B
SSUS, 2050B
SSUS, 2080D
8
UCS (MPa)

0
6
4
2
0
0
5
10
Time (months)
15
SSUS B (2050, 2080) & D (2080)
20
Unconfined Compressive Strength
Contaminated, dry
summer (A/B) and
control

10
SSCS, Control
SSCS, 2080B
SSCS, 2050B
8
UCS (MPa)

Control similar to
SSUS but half the
value
6
4
2
0
0
5
10
Time (months)
15
20
SSCS B (2050, 2080)
Aged, intermittent
summer rainfall (D)


Higher than SSUS
control
Similar values for both
ASSUS and ASSCS
10
ASSUS, 2080D
8
UCS (MPa)

ASSCS, 2080D
6
4
2
0
0
5
10
Time (months)
ASSUS & ASSCS D (2080)
15
20
 Background
 Laboratory
experiments
 Experimental results
 Conclusions
Conclusions

Without climate effects, properties were constant with
time. Contamination caused permeability to increase by
1 order of magnitude and UCS to decrease by half.
 Climate change scenario causing most damage was
intermittent summer rainfall and flooded winter.
 For unaged systems, permeability generally increased
by 2 to 3 orders of magnitude after 1st summer then
remained constant. Low correlation between visible
damage and permeability. UCS decreased with time.
 Accelerated ageing results indicate that long-term
properties of S/S remediated soils may improve their
resistance to climate change impacts.
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