2006 APWA International Congress & Exposition Kansas … · 1 INDEPENDENT ENVIRONMENTAL ENGINEERS,...

T.D. Stark Lecture – 9/13/06 ©

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LANDFILL STABILITY ISSUES

Timothy D. Stark, Ph.D., P.E.University of Illinois at Urbana-Champaign

2006 APWA International Congress & ExpositionKansas City, Missouri


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• Current Situation

• Liner Failure Mechanisms

• Cover Failure Mechanisms

• Emerging Issues

OUTLINE

• Conclusions


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CURRENT SITUATION

• MAJORITY OF LANDFILLS ARE CONSTRUCTEDAND OPERATED SAFELY

• STATE-OF-PRACTICE TESTING, DESIGN,AND ANALYSIS PROCEDURES

• NATURAL MATERIALS - 12

• GEOSYNTHETIC MATERIALS - 32


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Death Toll = 216

(Merry 2005)


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6


7


8


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• Emerging Issues

OUTLINE

• Conclusions


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LINER FAILURE MECHANISMS

• INTERIM SLOPEwith or without toe excavationlateral expansion

• WEAK FOUNDATION SOIL

• WEAK INTERFACE OR SEAM

• LEACHATE RECIRCULATION

• LINER CONSTRUCTION

• RAPID WASTE PLACEMENT OR REGRADING

• WASTE RELOCATION


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• WEAK INTERFACE OR SEAM






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• WEAK SEAM OR INTERFACE






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• Emerging Issues

OUTLINE

• Conclusions


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COVER FAILURE MECHANISMS

• RAINFALL/SEEPAGE-INDUCED• GAS OR LEACHATE-INDUCED • GCLs (?)

Replace woven geotextileFlip GCL over

• WEAK INTERFACE


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• Emerging Issues

OUTLINE

• Conclusions


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EMERGING/TROUBLING ISSUES• LACK OF DESIGN

- Recycling designs- Use of peak instead of residual strength- Not locating critical cross-section


21Critical Cross-Section


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EMERGING/TROUBLING ISSUES

• INADEQUATE TESTING- Soils & geosynthetics- Data recycled from prior site- Full range of normal stress


23Testing Full Range of Normal Stresses


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REGULATIONS

• California, Missouri, Ohio, & Wisconsin, – require extensive stability/geotechnical evaluations

• Michigan Rule 425(8)“Slopes of the final cover shall not exceed thosenecessary to prevent erosion and maintain slopestability. The final slope shall not be more than1 vertical to 4 horizontal at any location…”


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EMERGING DESIGN CONDITIONS

• NEW DESIGN CONDITIONS- Leachate recirculation/bioreactors- Strength of degraded waste- 3D stability analyses- Allowable seismic deformation – 4 to 6 inches


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CONCLUSIONS

• MAJORITY OF LANDFILLS ARE CONSTRUCTEDAND OPERATED SAFELY

• EMERGING ISSUES


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Questions & Comments are

Welcome


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Speaker Information:

• Timothy Stark, Ph.D., P.E.– Professor of Civil and Environmental Engineering– University of Illinois at Urbana-Champaign– 205 N. Mathews Ave.

Urbana, IL 61801– 217-333-7394– [email protected]

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INDEPENDENT ENVIRONMENTAL ENGINEERS, SCIENTISTS AND CONSULTANTS

Steve R. Nesbitt, Senior AssociateMalcolm Pirnie Inc.

701 Town Center Drive, Suite 600Newport News, Virginia

(757) 873-4380

MSW Landfill Stability Issues Case Study

INDEPENDENT ENVIRONMENTAL ENGINEERS, SCIENTISTS AND CONSULTANTS INDEPENDENT ENVIRONMENTAL ENGINEERS, SCIENTISTS AND CONSULTANTS

Group

Columbia Group

Chesapeake Group

Tabb Formation

Yorktown Formation

Interbedded sequence of SAND, SILT, or CLAY (Inert Fill)

Greenish to gray, highly plastic or organic CLAY (Morgarts Beach Member)

Gray to green, very loose to medium density, fine to coarse SAND

(formerly Columbia Aquifer)

Clay Confining Unit

Upper Yorktown Aquifer

Geologic Formation Sediments Hydrogeologic Unit

Simplified Site Geology and Hydrogeology

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Morgarts Beach Confining Unit

CDD Waste

Progression of Site Development



CDD WasteInert Fill Berm Inert Fill Berm



CDD WasteInert Fill Berm Inert Fill Berm



3


Inert Fill Berm Inert Fill Berm

CDD Waste


CDD Waste Filling



CDD Waste


CDD Waste Filling


Inert Fill BermInert Fill Berm

CDD Waste

CDD Waste Filling


4


Inert Fill BermInert Fill Berm

CDD Waste

CDD Waste Filling



CDD Waste Filling



CDD Waste



CDD Waste

CDD Waste Filling


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CDD Waste


CDD Waste Filling




CDD Waste

CDD Waste Filling




CDD Waste

CDD Waste Filling


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INDEPENDENT ENVIRONMENTAL ENGINEERS, SCIENTISTS AND CONSULTANTS INDEPENDENT ENVIRONMENTAL ENGINEERS, SCIENTISTS AND CONSULTANTS INDEPENDENT ENVIRONMENTAL ENGINEERS, SCIENTISTS AND CONSULTANTS INDEPENDENT ENVIRONMENTAL ENGINEERS, SCIENTISTS AND CONSULTANTS

Typical Cross Section

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Inert Fill SPT N-Values

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 3 0 3 5 4 0

SPT N-Value

Dep

th (

ft)


Corrected Inert Fill SPT Data

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

2 0

0 1 2 3 4 5 6 7 8 9 10 11 1 2 13 14 1 5 16 17 1 8 19 2 0 2 1 22 2 3 2 4 25 2 6 27 28 2 9 30 31 3 2 3 3 34 3 5 36 37 3 8 39 40 4 1

Corrected SPT N-Value

Fre

qu

ency

.00%

20.00%

40.00%

60.00%

80.00%

100.00%

120.00%

Frequency Cumulative %

Mode

Median

Average


Wood fragments

Wood fragments


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Mogarts Beach Confining Unit Shear Strength

0

1000

2000

3000

4000

5000

6000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900

Shear Strength (Undrained), psf

Ove

rbu

rden

Str

ess,

psf

B13 (Sur. Elev. 10.3 ft)-UU-Elev. -39 ft Field Vane (Sur. Elev. 10.3)-B13-Elev. -23 ft

Field Vane (Sur. Elev. 10.3 ft)-B13-Elev. -25 ft Field Vane (Sur. Elev. 10.3 ft)-B13-Elev. -28 ft

B12-CU (Sur Elev. 9.75 ft) (Total Stress)-Elev. -35 ft B13 (Sur. Elev. 10.3 ft) Shear Strenghts from Empirical Correlation

B12 (Sur. Elev. 9.75 ft) Shear Strengths from Empirical Correlation B7-UU

B8-UU B4-UU

B7-Correlated B8-Correlated

B4-Correlated B3-CU

B1-A-CU Direct Shear

Segment 1(Stage 1)

Segment 3(Stage 1)

Segment 4(Stage 1)

Segment 2(Stage 1)

Estimated 'trend -line'

0

1000

2000

3000

4000

5000

6000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900

Shear Strength (Undrained), psf

Ove

rbu

rden

Str

ess,

psf

B13 (Sur. Elev. 10.3 ft)-UU-Elev. -39 ft Field Vane (Sur. Elev. 10.3)-B13-Elev. -23 ft

Field Vane (Sur. Elev. 10.3 ft)-B13-Elev. -25 ft Field Vane (Sur. Elev. 10.3 ft)-B13-Elev. -28 ft

B12-CU (Sur Elev. 9.75 ft) (Total Stress)-Elev. -35 ft B13 (Sur. Elev. 10.3 ft) Shear Strenghts from Empirical Correlation

B12 (Sur. Elev. 9.75 ft) Shear Strengths from Empirical Correlation B7-UU

B8-UU B4-UU

B7-Correlated B8-Correlated

B4-Correlated B3-CU

B1-A-CU Direct Shear

Segment 1(Stage 1)

Segment 3(Stage 1)

Segment 4(Stage 1)

Segment 2(Stage 1)

Estimated 'trend -line'


Morgarts Beach Confining Unit Shear Strength

62590012001200

Stage 2(Groundwater Condition 2)

62590012001200

Stage 1(Groundwater Condition 2)

550700825950Stage 1 (Groundwater Condition 1)

Segment 4Segment 3Segment 2Segment 1

Shear Strength (psf)


0.468

CDD

York town Sand

Inert Fill

Layer 3

El. 136El. 140

E l . 2 0

Layer 1

5 %

3 H : 1 V

E l . 1 0E l . 4

El. 120

Layer 2 Layer 4

Pond

Additional

Berm

CDDCDD

Distance (ft) (x 1000)0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Preliminary Slope Stability Analysis

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Staged Development

Stage 1 Pond Filling

Stage 1 Waste Filling

Stage 2 Pond Filling

Stage 2 Waste Filling Existing CDD Waste

Existing Inert Fill

Groundwater Condition 1 (Active Dewatering)

Groundwater Condition 2 (Post-Dewatering)

Morgart ’s Beach Clay


Landfill Stability Factors of Safety

1.7531.5881.3491.201Stage 2 (Groundwater Condition 2)

1.9251.7911.4251.254Stage 2(Groundwater Condition 1)



CircularBlockCircularBlock

Effective Stress AnalysisTotal Stress Analysis

Factor of Safety

Stage and Water Table Level


Mogarts Beach Confining Unit Structure Map

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Mogarts Beach Confining Unit Isopach Map


Pre- and Post-Settlement Cross Section

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700

Pre-settlement Post-settlement

Ele

va

tio

n (f

t am

sl)


Total Settlement of Piggyback Liner

55.0

65.0

75.0

85.0

95.0

105.0

115.0

200 220 240 260 280 300 320

Initial Slope Surcharge Phase 1 Settlement Total Settlement

Ele

va

tio

n (f

t am

sl)

Horizontal Distance (ft.)

Inert FillCDD Waste

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Liner System (Lateral Expansion Area)


Settlement Deflection Mound



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Positive drainage


Summary of Liner System Factors of Safety

1.3400

1.51.5

1.9600

12%12%

6.5%0.02%

II

Differential Settlement:

Piggyback Liner System

Bottom Liner System

FS/FSmin

Minimum Allowable Factor of

Safety

Factor of

SafetyAllowable

ValuePredicted

ValueReference AppendixPhysical Stress

2006 APWA International Congress & Exposition Kansas … · 1 INDEPENDENT ENVIRONMENTAL ENGINEERS,...

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