sustainable soil stabilization in geotechnical engineering of china · 2017-11-21 · sustainable...
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Sustainable Soil Stabilization in
Geotechnical Engineering of China
Y.-J. Du
Southeast University, China
Sept. 21st, 2017 Sustainability in Geotechnical Engineering Workshop
• NSFC Funding and industry partners
• Colleagues: Prof. Liu and Cai
• Graduate students
• International partners: Prof.
Horpibulski, Arul, Reddy
ACKOWLDEMENTS
Yan-Jun Du PhD, PE
Expertise:
• Remediation and reuse of contaminated soils and sediments
• Vertical cutoff walls in geoenvironmental applications
• Modelling coupled thermal-hydraulic-stress-chemical responses of
remediated soils at urban areas
• Resilience and sustainability of innovative geomaterials in geotechnical
and geoenvironmental engineering
• Structural response of buried flexible pipelines
Education:
• Bachelor and Master, Nanjing University, 1994, 1997
• PhD, Geotechnical Engineering, Saga University, Japan, 2001
Working Experience
• 2008-: Southeast University
Committee Memberships
• Member, Committee on Geoenvironmental Engineering, American
Society of Civil Engineers/Geo-Institute (2014-Present).
Editorships and Editorial Boards:
• Canadian Geotechnical Journal (EBM)
• ICE Environmental Geotechnics (EBM)
• Lowland Technology International (AE)
Funding and Projects:
• 5 NSFC grants, 1 863 Projects, 2 Jiangsu Province NSF grants.
Awards/Honors:
• Award of Mao Yi-Sheng (茅以升) Science and Technology.
• Second Grade Award of Technology Invention, China Ministry of
Education.
• Second Grade Award, China National Technology Invention.
• Natural Science Foundation for Distinguished Young Researchers of
Jiangsu Province
Yan-Jun Du
Prof. Director
Institute of Geotechnical Engineering
School of Transportation
Southeast University
Can. Geotech. J. Outstanding
Reviewer for 2016
CONTENTS
Research background
Industrial wastes
Case studies
Concluding Remarks
Research background
Stabilization of problematic soils
Relatively High
Cost
Environmental Problems
Cement production
leads to ~1 Gt CO2/yr
Challenges in Problematic Soil
Stabilization
Industrial Wastes
China Statistics Press 1997
and 2003, SEPA 2000
Annual Increase
Soil and
Groundwater
Pollution
Non-renewable Materials
Reuse industrial wastes to
stabilize soils
SOLUTION
Industrial wastes
Industrial wastes Main source Output in China Main component
Calcium carbide residue
(CCR)
By-product of
acetylene
~ 20 million tons
in 2016
CaO (up to ~70%)
Fly ash Coal-fired
power plant
~ 300 million tons
per year
SiO2 (up to ~70%), Al2O3
(up to ~40%), CaO (up to
~20%),
Ground granulated
blastfurnace slag (GGBS)
steel
production
~ 90 million tons
per year
CaO (30% ~ 42%),
SiO2 (35% ~ 38%),
(Al2O3 (10% ~ 18%)
Lignin Waste from
paper industry
Accounting for
20%~30% of total
waste water
Active functional group:
hydroxyl group (-OH),
carbonyl group (-C=O),
carboxyl group (-COOH),
methyl group (-CH3 ), etc.
Industrial wastes frequently used for soil stabilization in China
South China
East China
Pan-Yellow
River area
Case study 1: over-wet clay stabilization using
calcium carbide residue (CCR)
Characteristics:
1. Relatively high water content, clay fraction and compressibility
2. Difficulty in compaction
3. Poor water-soaking durability
Conventional binders: quicklime, cement, quicklime + fly ash
Physical and mechanical properties
compaction degree = 96%
compaction
degree = 96%
0
4000
8000
12000
16000
20000
45%
Mo
du
lus
of
resi
lien
ce,
E0 (
kP
a)
Curing time (d)
Untreated soil
CCR 6%
Lime 6%
7 28
30%
96% Compaction degreecompaction
degree = 96%
8 10 12 14 16 18 201.60
1.65
1.70
1.75
1.80CCR content
4%
6%
8%
Dry
den
sity
(g/c
m3)
Water content (%)
CCR stabilized soils possess superior mechanical and durability
performance than quicklime in terms of qu, water durability, CBR,
and resilient modulus (E0).
Curing time
CCR-stabilized clay shows greater durability under wetting-
drying and freezing - thawing cycles.
FT=0 FT=3 FT=6 FT=9 FT=12 FT=16 FT=20400
800
1200
1600
2000
2400
Number of cycle
qu (
kP
a)
Untreated soil
CCR treated soil (6%)
Lime treated soil (6%)?
CCR (7 d)
CCR (28 d)
Lime (7 d)
Lime (28 d)
CCR-stabilized clay
Number of wetting-drying cycles M
ass
loss
(%
)
CCR-
stabilized
clay
Quicklime-
stabilized
clay
freezing and thawing cycle
Physical and mechanical properties
Quicklime-stabilized clay
0 20 40 60 80 100 12012.3
12.4
12.5
12.6
12.7
12.8
pH
Curing time (d)
6% CCR
6% Lime
Mechanisms
6% Lime
pH
qu(M
Pa)
6% CCR
Ca + 2OH- + SiO2 → CSH
Ca + 2OH- + Al2O3 → CAH
0 100 200 300 400 500 600 700 80092
94
96
98
100
温度(oC)
C
(b)
CAH/CASH
-0.04
-0.02
0.00
0.02
TGA
DTG
DTG
TGA
92
94
96
98
100
(a)
C
-0.04
-0.02
0.00
0.02
dm
/dt
(%/o
C)
质量
m (
%)
CSH
CSH
Ca(OH)2
Ca(OH)2
6% CCR (120 d)
6% Lime (120 d)
Untreated clay (180 d) lime-stabilized clay (180 d) CCR-stabilized clay (180 d)
CCR stabilized clay possesses higher amount of Ca(OH)2 and
CSH/CASH, and therefore denser structure.
Mechanisms
0%
20%
40%
60%
80%
100%
不同大小孔隙百分含量
(a) (b) (c) (d) (e) (f)
35~300μm
0.9~35μm
0.007~0.9μm
0~0.007μm
6%
Lime
(28 d)
6%
CCR
(28 d)
6%
Lime
(60 d)
6%
CCR
(60 d)
6%
Lime
(120 d)
6%
CCR
(120 d)
Pore size
Pro
po
rtio
n (
%)
30 35 40 45 50 55 601.8
1.9
2.0
2.1
2.2
2.3
2.4
35 40 45 50 55 60 65
28 d
28 d
60 d
60 d
60 d
28 d
qu (
MP
a)
Pore size distribution (%)
d < 0.9 m
6% CCR
6% Lime
28 d
120 d
120 d
120 d
120 d
0.9 m < d < 200 m
6% CCR
6% Lime
60 d
Proportion of micropore (d < 0.9 mm) in CCR-stabilized clay is
larger than lime stabilized clay.
CONTENTS
Research background
Industrial wastes
Case studies
Concluding Remarks
Field trials
Shanghai
Nanjing
CBR
DCP
Deflection
Constructions
(1) Spreading soil (2) Paving CCR (3) Paving lime
(4) Mixing by plow (5) Enhanced mixing by dozer (6) Compacting by vibrating roller
Construction duration is 17 days with compaction degree of 94%.
No dust during CCR paving.
Field Trials
CCR-stabilized clay display higher CBR, E0, and light dynamic
cone penetration resistance regardless of curing time
CCR
Quicklime
CCR
Quicklime
CCR
Quicklime Deflection
DCP
Quicklime CCR
CCR
Quicklime
Environmental quality valuation
Metal Lime CCR 4% Lime 6% Lime 6% CCR
Cu 5.8 1.48 25.6 24.1 25.3
Zn 33.2 3.21 81.3 71.9 81.2
Ni 5.68 2.1 34.8 33.1 35.3
Cr 23.9 2 68.1 64.2 69.3
Ba 1078 31 512 440 479
Pb 7.9 <0.2 11.7 13.4 18.5
Cd 1.35 <0.01 0.167 0.076 0.165
Hg 0.018 <0.005 0.025 0.026 0.03
As 84.2 0.4 15.1 11.5 15.7
Se 0.978 <0.04 <0.04 <0.04 <0.04
Metal concentration in raw materials and stabilized clay
(mg/kg)
Metal concentrations of target
metals in CCR- and lime-
stabilized clays are all lower
than limit values of Level III
soil stipulated by Chinese
Environmental Quality
Standard For Soils (GB
15618-1995).
Sample
ID
Leaching
solution
pH Metal concentration in leachate (mg/L)
Cr Cu Ni Pb Zn
6%
CCR
Acid rain 5.05 <0.061 <0.054 <0.15 <0.42 <0.018
DIW 7.0 <0.061 <0.054 <0.15 <0.42 <0.018
6%
Lime
Acid rain 5.05 <0.061 <0.054 <0.15 <0.42 0.02
DIW 7.0 <0.061 <0.054 <0.15 <0.42 <0.018
Metal concentration in leachate from stabilized clay
Testing method: batch-type leaching, USEPA
Metal concentrations in
leachate from CCR- and lime-
stabilized clays are all lower
than limit values stipulated by
RCRA, US.
Case study 2: Silty soil stabilization using lignin
Stabilized silt used for roadway subgrade filling
Dafeng
Nanjing
Yancheng
N
0 100 km
Shanghai
Lianyungang
Location of
Testing Site
Regions with Silt
Construction procedure flow chart of the lignin
stabilized embankment Zhang et al. 2017, Zhang et al. 2016, Liu et al. 2016, etc.
Case study 2: silt stabilized using lignin
The use of lignin as a stabilization chemical mixture for silty soil is
one of the viable answers to the reuse of biobased organic by-
product in civil engineering.
12% lignin stabilized silt
8% quicklime stabilized silt
12% lignin stabilized silt
8% quicklime stabilized silt
blow counts
pen
etra
tion
dep
th (
cm).
12% lignin
stabilized
silt
8%
quicklime
stabilized
silt
12% lignin stabilized silt exhibits
superior mechanical performances
than 8% quicklime stabilized silt
Case study 3: soil stabilized using GGBS + MgO
optimum content
for clayey silt
optimum content
for sand
permeability of
stabilized sand
k range of soil
stabilized with PC
SEM of 10% binder
stabilized sand with PC (28 d)
SEM of 10% binder
stabilized sand with GGBS +
MgO (28 d)
GGBS hydration
activated by MgO
Optimum GGBS:MgO ratio of stabilized soil generally ranges from 19:1 to 4:1.
28-day UCS of soil stabilized with GGBS + MgO is ∼1.3 to 4 times that of PC
stabilized soil. Yi et al. 2016, 2013, 2012, Du et al. 2016, etc.
Challenges in
drying-wetting cycle !
Case study 4: lead contaminated clay stabilized by
GGBS-MgO
UCS of GGBS-MgO stabilized clay is approximately 12%-43% higher than
that of the cement solidified clay.
Effective diffusion coefficient of lead (De) of lead contaminated clay stabilized
by GGBS-MgO is lower than that of cement stabilized clay Bo et al. 2015, etc.
Comparison of UCS between GGBS-MgO and
cement stabilized specimens
UC
S (
kP
a)
De
(m2/s
)
Initial pH of leachate
CONTENTS
Research background
Industrial wastes
Case studies
Concluding Remarks
Concluding Remarks
Industrial wastes (e.g., calcium carbide residue, fly ash,
ground granulated blastfurnace slag, and lignin) have
been successfully applied in soil stabilization in China.
Soil stabilized with industrial wastes generally shows
comparable and even better performances in terms
of strength, modulus of resilience, water soaking and
wetting-drying durability.
Environmental quality evaluation (e.g., leaching test,
acid rainfall infiltration test) and solute transport
modelling are necessary to assess potential impacts to
surrounding environment.
• ResearchGate: https://www.researchgate.net/profile/Yan_Du8/info
• Google Scholar:
https://xues.glgoo.com/citations?user=ykIVrpEAAAAJ&hl=zh-CN&oi=ao
• ORCID: http://orcid.org/0000-0001-9533-8976?lang=en
• Mendeley: https://www.mendeley.com/profiles/yan-jun-du/
• Wechat: dyj2640929283
Thanks for your listening!
• CCR stabilized soils-field trials: Du et al. (2016) Soils Foundations
• CCR stabilized soils-lab scale: Jiang et al. (2016) Can. Geotech. J.
• Activated GGBS stabilized soils: Yu et al. (2016) Du et al. (2017).
ASCE J. Mat. Civil Engrg.
• Solidification/stabilization of heavy metal contaminated soil: Du
et al. (2012, 2014) J. Hazard. Mat.; Du et al. (2014) Can. Geotech.
J.
• Slurry-trench wall: Yang et al. (2017) Can. Geotech., J. ASCE
JGGE (2017); Fan et al. (2017) ASCE JGGE (2017)