ground subsidence: infrastructure impact, …€¦ · 2 subsidence is a consequence of withdrawing...

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Ground Subsidence: Infrastructure Impact, Ground Subsidence: Infrastructure Impact, Investigations, Solutions and MonitoringInvestigations, Solutions and MonitoringMike Rucker, P.E.Mike Rucker, P.E.AMEC Earth & Environmental, IncAMEC Earth & Environmental, IncTempe, AZ [email protected], AZ [email protected]

2010 NACE Western Region 2010 NACE Western Region County Engineers SymposiumCounty Engineers Symposium

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Subsidence is a Consequence of WithdrawingSubsidence is a Consequence of WithdrawingGroundwater Faster than it can be RechargedGroundwater Faster than it can be Recharged

Areas of subsidence attributed to groundwater overdraftGalloway et al, 1999

Subsidence at Mendota, CAUSGS

“Subsidence causes permanent inundation of land, aggravates flooding, changes topographic gradients, ruptures the land surface, and reduces the capacity of aquifers to store water” (T.L. Holzer and D.L. Galloway, 2005)

2010 NACE Western Region County Engineers Symposium

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Ground Subsidence Ground Subsidence –– Infrastructure ImpactsInfrastructure Impacts

Extruded well casing south of Cochise, AZ

Irrigation canal grade change,

west of Glendale,

AZ

Impact infrastructure sensitive to differential elevations & graImpact infrastructure sensitive to differential elevations & gradesdes-- Gravity water conveyanceGravity water conveyance-- sewerssewers-- collapse of deep well casingscollapse of deep well casings

Rail spur grade change south of Cochise, AZ2010 NACE Western Region County Engineers Symposium

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Ground Subsidence Ground Subsidence –– Floodplain ImpactsFloodplain Impacts

Images from ADWR, 2010

Relative ground elevation changes lead to floodplain changes Relative ground elevation changes lead to floodplain changes ––-- Luke AFB closed 3 days in 1992; flooding caused by 18 ft differLuke AFB closed 3 days in 1992; flooding caused by 18 ft differential ential

subsidence & reversal of Dysart Drainsubsidence & reversal of Dysart Drain-- Wenden AZ 2010 flooding influenced by subsidenceWenden AZ 2010 flooding influenced by subsidence


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Basic Subsidence mechanismsBasic Subsidence mechanisms


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Subsidence can lead to another class of problem Subsidence can lead to another class of problem ––Earth FissuresEarth Fissures


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Earth Fissures can Impact Linear Infrastructure suchEarth Fissures can Impact Linear Infrastructure suchas Canals, Highways & Flood Control Structuresas Canals, Highways & Flood Control Structures

I-70, Northern NevadaMcMicken Dam, AZ


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Typical Sequence of Earth Fissuring Typical Sequence of Earth Fissuring Shallow ImpactsShallow Impacts

Adapted from Bell, 19812010 NACE Western Region County Engineers Symposium

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Waterlinebreak -developedovernight

Example Earth Fissure Problem Example Earth Fissure Problem ––Mine Dewatering in Northern NevadaMine Dewatering in Northern Nevada


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Detecting & Monitoring SubsidenceDetecting & Monitoring Subsidence

Repeat GPS & Level Surveys

Satellite-based Interferometry bySynthetic Aperture Radar (InSAR)


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Example Example -- 2010 InSAR Sinkhole Study Quantified2010 InSAR Sinkhole Study Quantified20052005--2006 Underground Mining Subsidence2006 Underground Mining Subsidence

Carlsbad, NM area InSAR 7/2005 to 3/2006InSAR image is ~60 miles (~100 km) across(AMEC, 2010)

StudyArea 2

detail


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Recent InSAR for Willcox AZ

area

Results of GPS monitoring atPower plant ash pond facility1996 – 2008, part of continuingAPP monitoring work

Survey requires Historic & Continuing Effort Survey requires Historic & Continuing Effort ––InSAR can be used to obtain Past History! InSAR can be used to obtain Past History!

Relative Settlements (feet) & Apparent Strains Between GPS Survey Monuments/Benchmarks - October 1996 to December 2008

8400

8600

8800

9000

9200

9400

9600

9800

7000 7200 7400 7600 7800 8000 8200 8400 8600 8800 9000

AZ Coordinate System East, 23xxxx meters

AZ

Coo

rdin

ate

Syst

em N

orth

, 11x

xxx

met

ers

Strain %>0.01

0.008 - 0.01

0.005 - 0.008

-0.01 - 0.005<-0.01

error not addressed

1.541.94

1.74

1.72

1.80

1.09

1.26

1.29

1.621.74

1.54

1.51 2.27 2.041.14 2.13 2.43 1.83

1.291.50 .91 1.72 2.04

1.92

1.15 1.86 1.05 1.39.85 1.76

0.043%

0.033%

0.028%

0.030%

0.021%

0.029% 0.043% 0.050% 0.044%1.5

2

1.5

11.5

2

10/2008 -10/200910/1996 – 12/2008

Where archived data is available, InSAR data exists as far back as 1992.


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2008 – with trash

2003 2004

2006post-flood

Subsidence and Earth Fissuring are Dynamic,Subsidence and Earth Fissuring are Dynamic,TimeTime--related Phenomenarelated Phenomena

Earth fissure gully developmentNorth of Dragoon Rd, Cochise County, AZ


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Meanwhile, at Dragoon Road Meanwhile, at Dragoon Road ––Local Mitigation to Prevent Catastrophic FailureLocal Mitigation to Prevent Catastrophic Failure

Earth fissure crossed Dragoon Road &Cochise Stronghold Road –Crossing reinforced to prevent piping failure(2004)


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In 2004, Subsidence Magnitude was Unknown In 2004, Subsidence Magnitude was Unknown --Maintenance Continues to this DayMaintenance Continues to this Day

Crossing survived massive summer flood events in 2006 without failure

By 2010, multiple leveling patches

Dec 2009 gas line brokenAdjacent to Cochise Stronghold Road:

Oct 2010 Piping holes on shoulder


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Not all Large Cracks are Earth Fissures Not all Large Cracks are Earth Fissures ––Giant Desiccation Cracks may Look SimilarGiant Desiccation Cracks may Look Similar……

Dragoon Road ~1 mile east of earth fissure, 2010

Upstream of Magma Dam near Florence, AZ, 2007

Desiccation crack exposed in deep test trench

East bound I-10 west of San Simon, AZ, 2006

But, cracking mechanisms and engineering implications may be very different

Looking West Looking East


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Soil Cement Core Upstream Soil Cement Apron

Keys to Understanding Subsidence: Geometry, Keys to Understanding Subsidence: Geometry, Material Properties, Pore Pressure ChangeMaterial Properties, Pore Pressure Change

Basin Alluvium Characterization Based on Deep Well Geophysical Results

100200300400500600700800900

10001100120013001400150016001700180019002000

1 10 100 1000 10000 1E+05 1E+06 1E+07 1E+08 1E+09 1E+10 1E+11 1E+12 1E+13 1E+14 1E+15

Short Normal (SN) Resistivity, ohm-mCaliper (cal) and gamma density (G-G) results at SG-6 are relative

Dep

th, f

t

SG-18 Short Normal SG-1 Short Normal SG-2 Short Normal

SG-21 Short Normal SG-4 Short Normal SG-6 caliper

SG-6 relative density SG-10 Short Normal SG-12 Short Normal

Bedrock low-perm clay hi-perm alluvium

approx water table (1978)

SG-18 SG-1,-2 SG-21 SG-4 SG-10 SG-12

2 10 30

SG-6

2 10 30 2 10 30 2 10 30

2 10 30 2 10 30

Northwest SoutheastVineyard FRSPowerlineUS 60

relative scale

East Salt River Valley CAP deep basin well data &

corresponding InSAR 1992-2000

Note extensive InSAR subsidence

signatures correlating to low resistivities

(<10 ohm-m)


CASE STUDY CASE STUDY ––Characterization, Remediation, and Characterization, Remediation, and Monitoring of a SubsidenceMonitoring of a Subsidence--Impacted Dam: Impacted Dam: McMicken Dam, ArizonaMcMicken Dam, Arizona

Subsidence up to ~5 ft at dam from groundwater withdrawal.

Mountain front

Earth fissure zone

Earth fissures were originally identified nearby in 1980 and were found to be threatening the dam in 2002.

Mitigated southern end

~18 ft subsidence1957-1992

earthfissuresInSAR 1996-1999 (ADWR)


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General Subsidence History in West General Subsidence History in West Salt River Valley Salt River Valley --

Period of rapid groundwater decline with associated

Rapid subsidence

Followed by

Period of groundwater stability / rise with associated

Reduced subsidence

Figure 8 - Water Level Data Trends near Sarival Ave. and Northern Ave.With Measured Subsidence along Reems Road at Peoria Ave. and Olive Ave.

500

550

600

650

700

750

800

850

900

950

1000

May-27 May-37 May-47 May-57 May-67 May-77 May-87 Apr-97 Apr-07

Date

Wat

er T

able

Ele

vatio

n (fe

et)

0

2

4

6

8

10

12

14

16

18

20

Mea

sure

d Su

bsid

ence

(fee

t)

B-02-01 06DBB3 water level B-02-01 06DBB2 water level B-03-02 25DBB water level B-03-01 29BCC water levelB-02-02 02BAD water level B-03-01 30NE subsidence Peoria Ave B-03-01 31NE subsidence Olive Ave

InSAR trend

roadway plans & profile 1965

wellelev

1100

elev0

elev-900

0 10 20 ohm-m

(B-3-1)32ddaResistivityWell Log

water conductivity (1986) ~500-600 umho/cmwater resistivity ~2000-1600 ohm-cm (20-16 ohm-m)

UAU

MAU


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General Subsidence History in West General Subsidence History in West Salt River Valley Salt River Valley --

5 Ft

10 Ft

15 Ft

Subsidence 1957 – 1991 (Schumann, 1992))Percent Fines Above 700 ft. and Earth Fissures

Stulik and Twenter, 1964 and AZGS 2010 NACE Western Region County Engineers Symposium

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Earth Fissure Threatening McMicken Dam Earth Fissure Threatening McMicken Dam ––Initial Earth Fissure Tracing Effort (2002)Initial Earth Fissure Tracing Effort (2002)


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Earth Fissure Features Traced Using Earth Fissure Features Traced Using Conventional Seismic RefractionConventional Seismic Refraction


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Gravity Survey(bedrock depth)& InSAR(alluvium lithology)

There were no logged deep wells in the area to provide useful data for depth to bedrock or subsurface characterization

Begin Deep Basin Characterization withBegin Deep Basin Characterization withGravity Survey & InSAR InterpretationGravity Survey & InSAR Interpretation


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Refraction Microtremor (ReMi) for shallower bedrock Refraction Microtremor (ReMi) for shallower bedrock spot depths to calibrate gravity interpretationsspot depths to calibrate gravity interpretations

ReMi uses surface waves (Rayleigh waves) to investigate and interpret a vertical 1-D s-wave profile to depths potentially greater than 100 meters

Equipment here included a 12 channel seismograph, 240-m cable, 4.5 Hertz low frequency geophones

Energy source is typically ambient noise; at quiet site, a vehicle driven alongside or beyond the array was energy source

South End McMicken Dam Dispersion Curve

1000

10000

0 0.1 0.2 0.3 0.4 0.5 0.6

1 / Frequency (Hz)

S-w

ave

Vel

ocit

y, fe

et/s

econ

d

0

50

100

150

200

250

300

Inte

rpre

ted

Dep

ths,

feet

s-wave =2000 f/s

s-wave =6200 f/s

s-wave =8500 f/s


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Resistivity Profile - Wenner MethodMcMicken Dam at INSAR Subsidence Bowl MS-40

100

1000

10000

100000

1 10 100 1000

Spacing, feet

Res

istiv

ity, o

hm-c

m

Measured Rshallow estimatedeep estimateintermediate estimate

Shallow Interpretation:R shallow = 20,000

Interface depth = 4 feetR deep = 12,000

Q2 = -.25

Deep Interpretation:R shallow = 700

Interface depth = 460 feetR deep = 10,000

Q2 = .87

Intermediate Intepretation:R shallow = 12,000

Interface depth = 140 feetR deep = 630

Q2 = -.90

Resistivity Soundings to Resistivity Soundings to Characterize Basin Alluvium Characterize Basin Alluvium

Confirmed presence & approximate depth to extensive localized clay bodies with resistivity < 1,000 ohm-cm (<10 ohm-m), whose presence was inferred by InSAR subsidence bowls

4-point Wenner array method with electrode spacings of 5, 10, 20, 50, 100, 200, 333, 500, 750 and 1000 ft was used.


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Clay Thickness Contour Map from InSAR Data;Clay Thickness Contour Map from InSAR Data;Clay confirmed by Deep ResistivityClay confirmed by Deep Resistivity

Depth to top of clay body could be inferred at an historic well that penetrated into the body, and from approximate interpreted depths to a low resistivity layer from deep resistivity soundings.

For model development purposes, a representative ‘clay body’ with significant time-delay consolidation behavior was assumed to be present and scale in thickness to the magnitude of local subsidence as inferred from InSAR


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Synthesis of Geophysical Results into Coherent Synthesis of Geophysical Results into Coherent Geologic and Finite Element Model Profiles Geologic and Finite Element Model Profiles

ClayeyUAU

Bedrock

Section A-A

x-distance (feet) (x 1000)0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

Ele

vatio

n (fe

et) (

x 1

000)

0.50.70.91.11.31.5


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600

700

800

900

1000

1100

1200

Jan-30 Jan-40 Jan-50 Jan-60 Jan-70 Jan-80 Jan-90 Jan-00 Jan-10 Dec-19 Dec-29

Date

Wat

er L

evel

Ele

vatio

n, fe

et

Model (A-A, C-C, D-D)

Model (B-B)

612984 1000 ft

612978 1000 ft612957 1000 ft

612989 1533 ft

503408 West of Dam!

612958 500 ft WT#3

Ground Elevation @ McMicken Dam ~ 1340 ft

StressStress--Strain ModelStrain Model

Measured Ground Subsidence InSAR Data to Further

Quantify Actual Subsidence Realistic Bedrock Geometry Characterization of Fine

Sediments Actual Well Hydrographs Internal Pore Pressure

Distributions Calibration of Input

Parameters Prediction

A 2-D linked seepage and elastic Finite Element model was developed that incorporated and honored these parameters -

Horizontal Strain

-0.06-0.04-0.020.000.020.040.060.08

0 1000 2000 3000 4000 5000 6000

Distance (feet)

Hor

izon

tal s

train

% 1981 1999

Earth fissure risk


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Based on the results of the full geotechnical investigation, including InSAR and finite element model results, fissure risk zonation was accomplished.

The dam section in the high risk zone was abandoned. A relocated dam section was designed and constructed.

Earth Fissure Risk ZonationEarth Fissure Risk Zonation


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A Dam Well FoundedA Dam Well Founded

New section

Abandoned section

Fissure zone


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Going Forward: MonitoringGoing Forward: Monitoring

•Visual Inspection•Aerial Imagery•InSAR•Groundwater Trends•Vertical Survey•Horizontal (GPS) Survey•Experimental TDR (Time-Domain Reflectometry) abandoned•Tape Extensometer•Experimental Rod Extensometer


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Tape ExtensometerTape Extensometer

90-foot sections located in areas of modeled and anticipated ground strain along new alignment, existing alignment, and within the earth fissure field.


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Recent & Current InSAR Images as Part of Recent & Current InSAR Images as Part of Continuing Monitoring ProgramContinuing Monitoring Program

November 2002 to October 2005 November 2002 to January 2006 October 2003 to September 2007InSAR provided by Arizona Department of Water Resources


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ProtoProto--type Rod Extensometertype Rod Extensometer


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GPS GPS –– Horizontal & Vertical MeasurementHorizontal & Vertical Measurement


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Case Study Case Study -- Some Lessons LearnedSome Lessons Learned

Washes often remove cemented soil horizons that are good for dam foundation Previous investigation disturbs ground, making visual inspection and

any subsequent investigations difficult TDR system is very sensitive – numerous breaks due to curing of

CLSM material it is encased in. Redundancy is necessary All instrumentation requires armor against vandalization Telemetric warning system was a challenge from the start. Sensitivity

of the TDR system rendered it essentially useless Survey costs quickly become unsustainable We still have much to learn – whole system needs to be re-evaluated

for effectiveness


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ClosureClosure

Available Resources in Arizona includeADWR for Subsidence, andAzGS for Earth Fissure Maps

“…public agencies that formerly were trying to stop subsidence are now adopting policies that promote it. Subsidence is returning...”(B.E. Lofgren, 1998)


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Questions?Questions?

Thank You for Thank You for Your Attention!Your Attention!


ground subsidence: infrastructure impact, …€¦ · 2 subsidence is a consequence of withdrawing...

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