02 James - Landslide Stabilization Uisng Microplkiles

7/31/2019 02 James - Landslide Stabilization Uisng Microplkiles

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LANDSLIDE STABILIZATION

USING MICROPILESSTATE ROUTE 837

WASHINGTON COUNTY, PENNSYLVANIAJames R. James, Gannett Fleming, Inc., Pittsburgh, PA

5th Annual Technical Forum

Geohazards in Transportation in the Appalachian Region

Charleston, West Virginia August 4, 2005


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STATE ROUTE 837

LANDSLIDE STABILIZATIONWashington County, PA

Presentation Outline Project Background

Slope Movement Diagnosis

Site Reconnaissance

Literature Review

Subsurface Investigation

Design Summary

Construction Overview


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STATE ROUTE 837


PROJECT BACKGROUND


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Project StakeholdersOwner: Commonwealth of Pennsylvania,

Department of Transportation

Designer: Gannett Fleming, Inc.

STATE ROUTE 837



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STATE ROUTE 837


Project Location Union Township, Washington County, PA

20 miles south of Pittsburgh

On the Valley Wall of the Monongahela River


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PROJECT SITE


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PROJECT SITE

REFERENCE: USGS, MONONGAHELA QUADRANGLE


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STATE ROUTE 837


SITE RECONNAISSANCE


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STATE ROUTE 837


Site Reconnaissance Summary

Distressed pavement Patching

Depression/displacements and cracking

Non-functioning roadway drainage systems

Toe bulges in soil below the adjacent RR

Past landslide remediation efforts by the RR

Outcrop of the Pittsburgh coal seam


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HUSTON

RUN

ROCK EMBANKMENT

PLACED BY RR

91

+50

10

6+00

12

0+00

11

6+50

SOUTHERN SLIDE NORTHERN SLIDE

TOE BULGES Monongahela River


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APPROXIMATE STATION 100+50


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HUSTON

RUN

ROCK EMBANKMENT

PLACED BY RR

91

+50

10

6+00

12

0+00

11

6+50

SOUTHERN SLIDE NORTHERN SLIDE

TOE BULGES Monongahela River

SITE OF FORMER COAL TIPPLE


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PITTSBURGH COAL OUTCROP


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MINE SEAL

CLOGGED DRAIN


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STATE ROUTE 837


LITERATURE REVIEW


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STATE ROUTE 837


Geologic Literature Summary

Ancient landslide area

Pittsburgh coal seam mined beneath adjacent areas of land

Near the axis of the Duquesne-Fairmont syncline


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PROJECT

LIMITS

SOIL AND ROCK SUSCEPTIBLE TO LANDSLIDING


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PROJECT

INTERVAL


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PROJECT

LIMITS


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PROJECT LIMITS


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STATE ROUTE 837


DESIGN SUMMARY


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Subsurface Investigation(s)

Limited information available from past studies 8 borings

3 inclinometers

40 additional borings 4 inclinometers

4 piezometers

Laboratory test data

SPT samples: classification and moisture content

Shelby tubes: direct shear strength Bedrock core samples: uniaxial compressive strength

STATE ROUTE 837



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MORE

THAN

7OF

ASPHALT


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STATE ROUTE 837


Analyses

Subsurface model created based upon site survey, boring data,piezometers and laboratory test data

Failure plane identified by inclinometer and boring data in

native soil near the top of bedrock


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C/L SR 837 RR TRACKS

MEASURED GROUNDWATER

FAILURE SURFACE

BEDROCK

FILL


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STATE ROUTE 837


Analyses (continued)

Failure of existing slope modeled by back analysis FS slightly less than 1.0 achieved

Rediscovered some pitfalls of back analysis (i.e., water levels)

Soil Strength Parameters: FILL MATERIALS: = 30; c = 100 psf; = 110 pcf

COLLUVIUM: = 14; c = 100 psf; = 130 pcf

STATE ROUTE 837


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STATE ROUTE 837



Remedial alternatives considered Horizontal drains deemed inappropriate

Excavation and replacement required detour

Anchored soldier pile wall requires ROW acquisition Tangent caisson wall $6-7 million

Ultimately, micropiles were selected

Relatively quick construction No need for additional ROW

Administratively simpler buried reinforcement


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Net load due to landslide mass: 25.7 kips/foot


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STATE ROUTE 837


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STATE ROUTE 837



Concurrent reestablishment/improvement of site drainage

Approximate final cost of $3.5 million

STATE ROUTE 837


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STATE ROUTE 837


CONSTRUCTION OVERVIEW

DRILLING RIG


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PILE DRIVING RIG

DRILLING RIGCRANE


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PILE DRIVING RIG


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PILE DRIVING RIG

REESTABLISHED

DRAINAGE


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INSTALLED

PIPE PILES


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DRILL STRING INSIDE PIPE PILE


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TEMPORARY DRILLING

SUPPORT FRAME


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02 James - Landslide Stabilization Uisng Microplkiles