___Randy SullivanGolder Associates Inc.Atlanta, Georgia, USA
May 17, 2017
Effects of Drainage on Landslide Movement at Interstate 40 across the Cumberland
Plateau Escarpment Courtney Vissman, PE – Golder Associates
Randy Sullivan, PE – Golder AssociatesDavid Barker, PE – TDOT
Lori Fiorentino, PE - TDOTRobert Jowers, PE – TDOT
___Site Location
2
NashvilleKnoxville
Rockwood
UI-40
___Site Location
3
Eastern Cumberland Plateau Escarpment separating Valley and Ridge and Cumberland Plateau
City of Rockwood
___April 2017 Aerial Photo looking East at MM342
4
WB I-40
EB I-40
Approx. slide limits
Construction Access Road
___Cross-Section through Slide
5
Pennington Fm.
Newnan Limestone
Gizzard Group
___Outline of Presentation History of slide
Desktop review & subsurface investigation
Short-term remediation in 2010-2011
Key findings & conclusions
Long term options & recommendations
Selected option and the 2018 geotechnical program
6
___Original Construction-1968
3
___Other Slides on Rockwood Mountain
3
Pennington Fm.
___Project History 1974 - 2003 East-bound lanes opened in 1974 Horizontal drains, trench drains and dewatering wells installed in 1968, 1972,
1974, and 1994 Geomembrane-lined ditches installed in 1990’s Slope inclinometers installed 1974 and 2003
9
Horizontal drain fan
___Project History 1976-2009
~0.5 in/yr from 1976-2009
TDOT retained Golder in 2009 for review of files
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___Desk Study and Geologic Mapping Historic headscarps Topographic bulge Colluvial lobes
dissected topographic bulge
___
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Desk Study and Geologic Mapping
___Interpreted Geologic Model
10
Roc
kwoo
d Th
rust
Pennington – slide-prone formation in TN & GA
Gizzard Group
Newnan Limestone
___Inclinometer Installation-2010
14
___Subsurface & Instrumentation Cross Section A-A
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___Short-Term Remediation - Dewatering
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All water piped and discharged here
___
0
10
20
30
40
50
60
70
80
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Annu
al P
reci
pita
tion
(inch
es)
Cum
ulat
ive
Incl
inom
eter
Dis
plac
emen
t (in
ches
)
Year
Composite Cumulative Displacement of Inclinometer and Yearly Precipitation
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Wel
ls c
ompl
eted
Wel
l adj
ustm
ents
st
arte
d
___Key Findings & Conclusions Roadway embankment construction in 1968 exacerbated on-going creep landslide
Sliding is within Pennington Shale at depth of more than 70 ft below embankment toe
Movement has slowed to ~0.1 in/yr since April 2014 (when adjustments to pumps started)
Total movement since 2011 has been about 2 inches
Incremental movement has been larger in years with higher annual rainfall
Movement likely to continue indefinitely
Performance to date suggest catastrophic movement is unlikely
Slide has progressed eastward since 1969 & recently northward near Westbound lanes, and may continue
Slide extends downhill below inclinometers
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___Options - EarthworkRe-alignment of I-40
Construct new westbound lanes
Relocate eastbound lanes onto current westbound lanes
High probability of triggering multiple landslides
Toe berm or buttress
Key imported earth into toe of slide
May require relocating local roads below I-40
Additional investigation needed to delineate extent of slide
Risk of new slide daylighting above or below berm or buttress; thus, not considered feasible
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___Options – Drainage
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___Options – Ground Anchors
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___Options: Reticulated Micropiles
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___Options: Status Quo with Risk Mitigation Measures
Delineate extent of slide
Dewatering system
Inclinometers
Remote monitoring
Emergency action plan
Miscellaneous
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___Summary of Long-Term Options Earthwork
Groundwater drainage
Ground anchors
Reticulated micropiles
Status quo with risk mitigation measures
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___2018 Geotechnical Program
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___2018 Geotechnical Program
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• 14 Boreholes and Inclinometer Casing
• PQ Drilling
• 2.75-inch Casing
• Geologic Mapping
• New Lidar Data Review
• Evaluate Effect of Additional Drains
• Plan for Remote Monitoring
S L I D E D E L I N E AT I O N A N D E VA L U AT I O N
CONTINUED PUMP IMPROVEMENT
CONTINUED INCLINOMETER MONITORING
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275
Thank You