Use of Launched Soil Nails toStabilize Landslides in Summit County, Ohio

Use of Launched Soil Nails toUse of Launched Soil Nails toStabilize Landslides in Stabilize Landslides in Summit County, OhioSummit County, Ohio

Mitchell W. Weber, P.G.Mitchell W. Weber, P.G.Gannett Fleming Engineers & Architects, P.C.Gannett Fleming Engineers & Architects, P.C.

Greg Bachman, P.E., P.S.Greg Bachman, P.E., P.S.County of Summit EngineerCounty of Summit Engineer

Robert K. BarrettRobert K. BarrettSoil Nail Launcher, Inc.Soil Nail Launcher, Inc.

Project LocationProject Location

I-77IR-480

IR-80SR-8

IR-271

Geologic SettingGeologic SettingNW part of Summit County lies NW part of Summit County lies within the Glaciated Allegheny within the Glaciated Allegheny Plateau.Plateau.–– Uplands and many slopes composed Uplands and many slopes composed

of End or Ground Moraine. of End or Ground Moraine. 33% Sand, 34% Silt, 32% Clay33% Sand, 34% Silt, 32% Clay

–– Cuyahoga River valley and base of Cuyahoga River valley and base of slopes composed of glacialslopes composed of glacial--lacustrine lacustrine deposits.deposits.

0% Sand, 39% Silt, 60% Clay0% Sand, 39% Silt, 60% Clay

Ohio Landslide AreasOhio Landslide Areas

Ref: ODNR GeoFacts No. 8

Landslides Affecting NW Summit Landslides Affecting NW Summit County RoadwaysCounty Roadways

NNN

Typical Slide CharacteristicsTypical Slide Characteristics

Glacial Till(SM-SC)

Glacial-Lacustrine(ML-CL)

21

± 46 ft.

10 – 12 ft.

OBSERVED SLIDE TYPES

• Earth Slumps

• Earth Flows

• Earth Block Slides

Basal Lacustrine DepositBasal Lacustrine Deposit

Engineering PropertiesEngineering Properties

(Ref: ODNR GB-2, Field Trip 3, Table 2)

Slide TriggersSlide Triggers

Increased Driving Forces (IDF)Increased Driving Forces (IDF)–– Saturation. (Saturation. (above average rainfall in 2003 & 2004above average rainfall in 2003 & 2004))–– Toe undercutting by stream erosion.Toe undercutting by stream erosion.–– Lateral Lateral ‘‘squeezesqueeze’’ of basal lake deposit.of basal lake deposit.

Decreased Resisting Forces (DRF)Decreased Resisting Forces (DRF)–– Softening of basal clay through desiccation and Softening of basal clay through desiccation and

wetting cycles.wetting cycles.

Rain, Rain, Go AwayRain, Rain, Go Away……

The Memorial Day (2004) weekend rains triggered The Memorial Day (2004) weekend rains triggered several landslides within the County, two resulted several landslides within the County, two resulted in immediate road or lane closures.in immediate road or lane closures.By June 2004, Summit County had 9 slides that By June 2004, Summit County had 9 slides that required required ““immediateimmediate”” attentionattentionCounty forces were occupied with other storm County forces were occupied with other storm damage clean up.damage clean up.County Engineer sought a County Engineer sought a ““good, fast, cheapgood, fast, cheap””solution. solution.

Selection of Launched Soil NailsSelection of Launched Soil NailsIn consultation with GF and SNL, nine In consultation with GF and SNL, nine ““emergencyemergency”” landslides site were selected landslides site were selected for remediation with launched soil nails.for remediation with launched soil nails.

Soil NailingSoil Nailing

Consists of reinforcing the ground with closely Consists of reinforcing the ground with closely spaced, passive inclusions (nails), to create inspaced, passive inclusions (nails), to create in--situ situ a coherent gravity structure which results in an a coherent gravity structure which results in an increase of the overall shear strength of the inincrease of the overall shear strength of the in--situ situ soil. soil. Basic design concept Basic design concept -- transfer the resisting transfer the resisting tensile forces generated in the nails into the tensile forces generated in the nails into the ground through the friction mobilized at the ground through the friction mobilized at the interfaces. interfaces.

Ref: FHwA –SA-96-069R

Soil NailsSoil NailsNails typically consist of :Nails typically consist of :–– Steel bars or other metallic elements that Steel bars or other metallic elements that

resist tensile & shear stresses and bending resist tensile & shear stresses and bending moments. moments.

–– Soil nails are not prestressed but are closely Soil nails are not prestressed but are closely spaced (e.g., one driven nail per 2.5 ftspaced (e.g., one driven nail per 2.5 ft²², one , one grouted nail per 10grouted nail per 10--50 ft50 ft²²) to provide an ) to provide an anisotropic apparent cohesion to the native anisotropic apparent cohesion to the native ground. ground.

Ref: FHwA –SA-96-069R

Suitable Ground ConditionsSuitable Ground Conditions

Favorable ConditionsFavorable Conditions–– Clays Clays –– Sandy soilsSandy soils–– Weathered rock; talus slope depositsWeathered rock; talus slope deposits–– Heterogeneous and stratified soils Heterogeneous and stratified soils

Soil nailing is generally not practical in: Soil nailing is generally not practical in: –– Soft, plastic claysSoft, plastic clays–– Organics/PeatOrganics/Peat–– Loose (N<10), low density and/or saturated soils Loose (N<10), low density and/or saturated soils

Launched Soil NailsLaunched Soil Nails

Launched Nail AdvantagesLaunched Nail Advantages

EffectiveEffective–– IncreasesIncreases shear resistance while shear resistance while decreasingdecreasing

shear stresses.shear stresses.Unobtrusive Unobtrusive –– Equipment can reach Equipment can reach ±± 20 20 -- 25 feet downslope.25 feet downslope.–– Articulating head facilitates working around Articulating head facilitates working around

trees and utility poles.trees and utility poles.–– Usually only shoulder or single lane closure Usually only shoulder or single lane closure

required.required.

Launched Nail AdvantagesLaunched Nail Advantages

Fast InstallationFast Installation–– 10 nails/hour, 100 nails/day.10 nails/hour, 100 nails/day.Immediate ResultsImmediate Results–– No waiting for grout set.No waiting for grout set.Single Process with small crew Single Process with small crew –– Performed by a laborer and a operator.Performed by a laborer and a operator.CostCost--effectiveeffective–– Average range of $200 $400/lf of crown length.Average range of $200 $400/lf of crown length.

Launched Soil NailsLaunched Soil Nails

Soil Reinforcing Elements Soil Reinforcing Elements –– 11--inch diameter, hollow steel tubes.inch diameter, hollow steel tubes.–– 2020--foot long.foot long.–– Perforated for drainage.Perforated for drainage.Installed by a Proprietary LauncherInstalled by a Proprietary Launcher–– Launcher mounted on an excavator.Launcher mounted on an excavator.–– Has 360Has 360ºº mobility.mobility.

The LauncherThe Launcher

Typical Launched Soil Nail Typical Launched Soil Nail Application Application

Slide Mass

Failure Surface

Launched Soil Nails3 or 4-foot c-c

2-3 rows

Typical Launched Soil Nail Typical Launched Soil Nail Application Application

Slide Mass

Failure Surface

Launched Soil Nails3 or 4-foot c-c

2-3 rows

Launcher in ActionLauncher in Action

Revere Road Slip Revere Road Slip -- BeforeBefore

Revere Road Slip Revere Road Slip –– AfterAfter

Highland Road Landslip Highland Road Landslip –– BeforeBefore

Highland Road Landslip Highland Road Landslip –– AfterAfter

Boston Mills Road Boston Mills Road -- BeforeBefore

Boston Mills Road Boston Mills Road -- AfterAfter

Columbia Road Columbia Road -- BeforeBefore

Columbia Road Columbia Road -- BeforeBefore

Columbia Road Columbia Road -- AfterAfter

Everett Road Everett Road -- BeforeBefore

Everett Road Everett Road -- AfterAfter

Slide Too LargeSlide Too Large

Summit CountySummit County’’ssLaunched Soil Nail StatisticsLaunched Soil Nail Statistics

11 sites have been nailed, repairing 1,000 lf 11 sites have been nailed, repairing 1,000 lf of roadway .of roadway .About 1,200 launched soil nails installed in About 1,200 launched soil nails installed in less than a 4 week time frame.less than a 4 week time frame.Cost of Cost of ±± $480,000.$480,000.County crews monitor repaired sites on County crews monitor repaired sites on monthly schedule, no renewed movement to monthly schedule, no renewed movement to date.date.

Design ResourcesDesign Resources

FHwAFHwA--SASA--9696--069R069RUSFS EMUSFS EM--71707170--13, Volumes I 13, Volumes I –– III.III.

Q & AQ & AQ & A