FRAMEWORK FOR THE ESTIMATION OF MSW UNIT WEIGHT …
Transcript of FRAMEWORK FOR THE ESTIMATION OF MSW UNIT WEIGHT …
FRAMEWORK FOR THE ESTIMATION OF
MSW UNIT WEIGHT PROFILE
Sardinia 2005, Tenth International Waste Management and Landfill Symposium
S. Margherita di Pula, Cagliari, Italy; 3 - 7 October 2005
by
D. ZEKKOS, J. BRAY, E. KAVAZANJIAN, Jr.,
N. MATASOVIC, E. RATHJE, M. RIEMER, & K. STOKOE II
Univ. of California at Berkeley, Arizona State Univ., GeoSyntec Consultants, & Univ. of Texas at Austin
Sponsored by the U.S. National Science Foundation
MSW Unit Weight Is Important• Large range of MSW unit
weight, e.g. 5 - 15 kN/m3”
– Differ by factor of 3!
• Liner interface strength depends on overburden stress
• Landfill capacity estimates depend on MSW unit weight
• Seismic performance depends on MSW unit weight profile
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.01 0.1 1 10
Period, sec
PS
A,
g's
Rock motionMSW surface-Kavazanjian et al. 1995MSW surface-constant unit weight
5% damping
Methods to Evaluate MSW Unit Weight
1. Landfill Records and Post-Placement Surveys
2. Unit Weight Measured from Conventional Geotechnical Sampling
3. In-Situ Large-Scale Test Pits or Large-Diameter Boreholes (mimics sand cone density tests with calibrated gravel)
In-Situ Large-Diameter Borehole Method
Developed by Kavazanjian and Matasovicfor OII Landfill
waste
wastewaste V
W=γ
1. Auger and collect waste 2. Weigh waste collected over interval (Wwaste)
3. Place tremie pipe in borehole 4. Fill with gravel of known unit weight (Vwaste)
Data from reliable in-situ large-scale methods available in Zekkos et al. (2005) Berkeley Geotechnical report
0
20
40
60
0 5 10 15 20 25Total unit weight, kN/m3
Depth
, m
1
2
3
4
5
6
7
8
9
10
11
(1) Santo Tirso, Portugal (Gomes et al. 2002); (2) OII, California, USA (Matasovic and Kavazanjian, 1998); (3) Azusa, California, USA (Kavazanjian et al, 1996); (4) Tri-Cities, California, USA (this study); (5) no name older landfill (Oweis and Khera, 1998); (6) no name younger landfill (Oweis and Khera, 1998); (7) Hong Kong, China (Cowland et al. 1993); (8) Central Mayne landfill, USA (Richardson and Reynolds, 1991); (9) 11 Canadian landfills (Landva & Clark, 1986); (10) Valdemingomez, Spain (Pereira et al. 2002); (11) Cherry Island landfill, Delaware, USA (Geosyntec, 2003);
Kavazanjian et al. (1995)
Large Scatter in Reliable MSW Unit Weight Data
Characteristic MSW Unit Weight Profile Exists
Tri-Cities
0
10
20
30
40
50
60
0 10 20 30
Dep
th, m
0
10
20
30
40
50
60
0 10 20 30
Azusa
0
10
20
30
0 10 20 30
"Younger" "older"
0
10
20
30
0 10 20 30
0
10
20
30
0 10 20 30
Dep
th, m
Cherry Island
0
10
20
30
40
50
60
0 10 20 30
OII
Geosyntec (2003), Matasovic and Kavazanjian (1998), Kavazanjian et al (1996), Oweis and Khera (1998), Zekkos et al (2005)
• Need landfill-specific data
• Model can be developed to capture change with depth
0
200
400
600
800
12 17 22Unit w eight, kN / m3
Mea
n ef
fect
ive
stre
ss, k
Pa
Kavazanjian 1999
Compaction Level (& waste composition) Determines Initial MSW Unit Weight
Confining StressDetermines Variationof MSW Unit Weight with Depth
5.0
10.0
15.0
0.00 0.20 0.40 0.60 0.80
Total energy per target volume of material (Joule/cm3)
Tota
l unit w
eig
ht,
kN
/m3
W=4.5kgr, h=80 cm,t=7.5cm
W=4.5kgr, h=40 cm, t=7.5 cm
W=5.4kgr, h=80 cm, t=5 cm
W=10kgr, h=80 cm, t=5 cm
W=10kgr, h=80 cm, t=7.5 cm
(Tri-Cities Landfill data)
Model calibration against field & lab
zz
i ⋅++=
βαγγ
Hyperbolic Relationship
9 10 11 12 13 14 15 16
400
300
200
100
0
Nor
mal
stre
ss, k
Pa
Unit weight, kN/m3
Looser specimen, γ i=10.3 kN/m3
Denser specimen, γ i=12.9 kN/m3
0
10
20
30
40
50
60
70
10 11 12 13Unit weight, kN / m3
Energ
y t
o M
SW
(co
mpact
ion
and/o
r co
nfinem
ent)
L
H
Depending on initial unit weight,increase in depth produces large or small increase in unit weight
Characteristic MSW Unit Weight Profiles
0
10
20
30
40
50
60
0 5 10 15 20
Total unit weight, kN/m3
Depth
, m
low
typical
high
OII landfill
Azusa landfill
"Older" landfill in New Jersey
compaction effort and soil cover
increasing compaction effort and soil cover
RECOMMENDATIONS FOR PRACTICE
(A) Design based on a comprehensive investigation
Step 1: Measure MSW unit weight near surface using test pits
Step 2: Measure MSW unit weight at greater depths using large-diameter boreholes
Step 3: Develop MSW unit weight profile using hyperbolic model
(B) Estimates based on a limited investigation
• Step 1: Estimate MSW unit weight near the surface using test pits, landfill records, or published values (γi ~ 13 kN/m4)
• Step 2: Use design charts to estimate α and β parameters (β = 0.4 m3/kN and α = 3 m4/kN )
0.0 0.2 0.4 0.6 0.8 1.0 1.24
6
8
10
12
14
16DESIGN CHART 1: ESTIMATION OF β - PARAMETER
Increa
sed c
ompa
ction
effort
& soil c
over
(lab)
Nea
r sur
face
uni
t wei
ght, γ i ,
kN /
m3
β - parameter, m3 / kN
Field data Tri-Cities OII Azusa "Older" "Younger" Cherry Island
0 2 4 6 8 10 120.0
0.2
0.4
0.6
0.8
1.0
1.2 Field data range
Laboratory data A3-1L A3-3L A3-7LA3-8LA3-12L
Increased compaction
effort & soil c
over (lab)
DESIGN CHART 2: ESTIMATION OF α - PARAMETER
β - p
aram
eter
, m3 /
kN
α - parameter, m4 / kN
zz
i ⋅++=
βαγγ
(C) Design of a new landfillUse MSW unit weight profiles for low, typical, or high
compaction effort and soil cover
0
10
20
30
40
50
60
0 5 10 15 20
Total unit weight, kN/m3
Depth
, m
low
typical
high
OII landfill
Azusa landfill
"Older" landfill in New Jersey
compaction effort and soil cover
increasing compaction effort and soil cover
Conclusions• Comprehensive MSW unit weight database has been developed
• A characteristic MSW unit weight profile exists for each landfill
• A hyperbolic model can capture the dependence of MSW unit weight on its composition, compaction effort, and confining stress
• The developed model was calibrated with reliable in-situ landfill unit weight data as well as large-scale laboratory data.
• Landfill-specific data are important for establishing the near surface (initial) unit weight of MSW
• Hyperbolic model can extend near surface data to greater depths
zz
i ⋅++=
βαγγ