___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

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NashvilleKnoxville

Rockwood

UI-40

___Site Location

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Eastern Cumberland Plateau Escarpment separating Valley and Ridge and Cumberland Plateau

City of Rockwood

___April 2017 Aerial Photo looking East at MM342

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WB I-40

EB I-40

Approx. slide limits

Construction Access Road

___Cross-Section through Slide

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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

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___Original Construction-1968

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___Other Slides on Rockwood Mountain

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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

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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

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Roc

kwoo

d Th

rust

Pennington – slide-prone formation in TN & GA

Gizzard Group

Newnan Limestone

___Inclinometer Installation-2010

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___Subsurface & Instrumentation Cross Section A-A

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___Short-Term Remediation - Dewatering

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All water piped and discharged here

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Composite Cumulative Displacement of Inclinometer and Yearly Precipitation

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___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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Thank You