FRAMEW ORK FOR THE ESTI MATI ON OF MSW UNI T W EI GHT PROFI LE - - PowerPoint PPT Presentation

FRAMEW ORK FOR THE ESTI MATI ON OF MSW UNI T W EI GHT PROFI LE

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

Significant Uncertainty in Current MSW Unit Weight Estimates

Augello et al. 1998

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

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.01 0.1 1 10 Period, sec PSA, g's

Rock mot ion MSW surface- Kavazanjian et al. 1995 MSW surface- const ant 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 Matasovic for OII Landfill

waste waste waste

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

20 40 60 5 10 15 20 25 Total unit weight, kN/ m 3 Depth, m

1 2 3 4 5 6 7 8 9 10 11

(1) Santo Tirso, Portugal (Gom es et al. 2002); (2) OI I , California, USA (Matasovic and Kavazanjian, 1998); (3) Azusa, California, USA (Kavazanjian et al, 1996); (4) Tri-Cities, California, USA (this study); (5) no nam e older landfill (Oweis and Khera, 1998); (6) no nam e 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) Valdem ingom ez, Spain (Pereira et al. 2002); (11) Cherry I sland 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 10 20 30 40 50 60 10 20 30 Depth, m 10 20 30 40 50 60 10 20 30 Azusa 10 20 30 10 20 30 "Younger" "older" 10 20 30 10 20 30 10 20 30 10 20 30 Depth, m Cherry Island 10 20 30 40 50 60 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

200 400 600 800 12 17 22 Unit w eight, kN / m

3

Mean effective stress, kPa

Kavazanjian 1999

Compaction Level (& waste composition) Determines Initial MSW Unit Weight Confining Stress Determines Variation

• f 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 volum e of m aterial (Joule/ cm 3) Total unit weight, kN/ m 3

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=1 0kgr, h=80 cm, t=5 cm W=1 0kgr, h=80 cm, t=7.5 cm

(Tri-Cities Landfill data)

Model calibration against field & lab

z z

i

⋅ + + = β α γ γ

Hyperbolic Relationship

9 10 11 12 13 14 15 16 400 300 200 100

Normal stress, kPa Unit weight, kN/m

3

Looser specimen, γi=10.3 kN/m

3

Denser specimen, γi=12.9 kN/m

3

10 20 30 40 50 60 70 10 11 12 13 Unit weight , kN / m3 Energy to MSW (com paction and/ or confinem ent) L H Depending on initial unit weight, increase in depth produces large

• r small increase in unit weight

Characteristic MSW Unit Weight Profiles

10 20 30 40 50 60 5 10 15 20 Tot al unit weight , kN/ m3 Depth, m low t ypical high OII landfill Azusa landfill "Older" landfill in New Jersey compact ion effort and soil cover increasing compact ion 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 1.2 4 6 8 10 12 14 16 DESIGN CHART 1: ESTIMATION OF β - PARAMETER

I n c r e a s e d c

• m

p a c t i

• n

e f f

• r

t & s

• i

l c

• v

e r ( l a b ) Near surface unit weight, γi , kN / m

3

β - parameter, m

3 / kN

Field data Tri-Cities OII Azusa "Older" "Younger" Cherry Island

2 4 6 8 10 12 0.0 0.2 0.4 0.6 0.8 1.0 1.2

Field data range Laboratory data A3-1L A3-3L A3-7L A3-8L A3-12L Increased compaction effort & soil cover (lab) DESIGN CHART 2: ESTIMATION OF α - PARAMETER β - parameter, m

3 / kN

α - parameter, m

4 / kN

z z

i

⋅ + + = β α γ γ

(C) Design of a new landfill

Use MSW unit weight profiles for low, typical, or high compaction effort and soil cover

10 20 30 40 50 60 5 10 15 20 Tot al unit weight , kN/ m3 Depth, m low t ypical high OII landfill Azusa landfill "Older" landfill in New Jersey compact ion effort and soil cover increasing compact ion 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

z z

i

⋅ + + = β α γ γ

Thank you

Additional information available at the Geoengineer website at: http://www.geoengineer.org