ibis-l: ibis-l: an innovative solution for remote monitoring of displacements on slopes and...

GeoradarIBIS System

March 2010 All rights reserved to IDS 1

IBIS Image by Interferometric Survey

A comprehensive family of ground-based Radar Interferometers for the measurement of displacements and

vibrations

GeoradarIBIS System


IBIS: ground-based interferometric radars

IDS present the IBIS family:

an innovative range of advanced “geodetic” instrumentsbased on ground-based radar interferometry aimed atproviding accurate measurement of movements over wideareas.

IBIS products have been designed to address the specificneeds of the civil engineering, geotechnical and miningmarkets

This revolutionary approach provides the IBIS users withaccurate remote measurements without requiring anycontact with the target and in almost all weather conditions.

GeoradarIBIS System


LANDSLIDE & DAM MONITORINGIBIS - L

SLOPE STABILITY IN MININGIBIS - M

STRUCTURE MOVEMENTSIBIS - S

IBIS product rangeAPPLICATIONSPRODUCTS

GeoradarIBIS System


IBIS-S: system & application fields

CULTURAL HERITAGES

BRIDGE TESTING

INDUSTRIAL FACILITIES

IBIS-S

GeoradarIBIS System


IBIS-L: system & application fields

GROUND SETTLEMENTS MONITORING

LANDSLIDE MONITORING

DAM MONITORING

IBIS-L

GeoradarIBIS System


IBIS-M: system & application field

IBIS-M

SLOPE MOVEMENT MONITORING WITHIn OPEN PITS MINES

GeoradarIBIS System


Techniques behind the IBIS systems

1. Stepped-Frequency Continuous Wave (SF-CW) technique resolves thescenario in the range direction, detecting the position in range of differenttargets placed along the radar’s line of sight;

2. Synthetic Aperture Radar (SAR) allows to obtain 2D high-resolution radarimages by adding to the range resolution (fro the SF-CW), the cross-rangeangular resolution

3. Interferometric technique, computes the displacement of each pixels bycomparing the phase information of the radar signal collected at differenttimes.

4. Persistent Scatterers algorithm (PSInSAR) selects among the whole imagethe high quality pixels and estimates the atmospheric artefacts in anautomatic and robust way

The IBIS products are based on four well-known radar techniques:

GeoradarIBIS System


The range resolution of 0.5 m, independent from the distance.

Stepped Frequency-Continuous Wave

IBIS

-S

n-th range bin

Range profile

Distance (m)

The SFCW radar detects the position in range of different targets placed along the radar’s line of sight

Ampl

itude

GeoradarIBIS System


IBIS-S installed at the turbine pillar base (height 60m)

Welding lines are good reflective points

Range Profile: one dimensional image with 0.5m range resolution

IBIS-S: 1-dimensional range profiles

GeoradarIBIS System


SAR technique enables the system to provide high cross range resolutionexploiting the movement of the physical antenna along a straight trajectory(linear scanner)

Using 2 m rail IBIS-L system obtains 4.38mrad (=0.25deg)

angle resolution

IBIS-L & IBIS-M: Synthetic Aperture Radar (SAR)

mradL

38.42

=⋅

=Δλϕ

The SAR process of the data, collected during the movement of the sensorhead on the 2 meter track, allows the IBIS-L and M systems to synthesize a2m antenna whose azimuth beam width is:

GeoradarIBIS System


The combination of SAR and SF-CW techniques allows the system toresolve the scenario into two dimensional pixels

IBIS-L & IBIS-M: SAR 2-dimensional images

Optical Image

Power MapPixel dimension:• 0.5m in range;• 1.35m – 4.05m cross range for 300 - 900m range

GeoradarIBIS System


The interferometric analysis provides data on object displacement bycomparing phase information, collected in different time periods, of reflectedwaves from the object, providing a measure of the displacement with anaccuracy of less than 0.01mm (intrinsic radar accuracy in the order of 0.001mm.)

Interferometric capability

TX

RX

TX

RX

d

TX

RX

TX

RX

d

First acquisition

Second acquisition

1ϕ

2ϕ

( )124ϕϕ

πλ

−−=d

GeoradarIBIS System


The displacement is measured in the direction of the line of sight of the system.

Rh

d

dp

α

hRdd p ⋅=

Rh=)sin(α

)sin(αpd

d =

To calculate the real displacement is needed to know the acquisition geometry

The distance Ris measured

by IBIS-S

Interferometric capability

GeoradarIBIS System


IBIS main advantages

obtain information from all the area illuminated by the antenna beam: the radarmeasures the local displacement of the scenario by resolving it into pixels of a fewsquare meters

high displacement measurement accuracy, up to 1/10 mm

day-night continuous operation

completely autonomous operation not requiring human intervention

acquisition frequency of the order minutes for IBIS-L, msec for IBIS-S

The main advantages of the use of IBIS for monitoring are:

possibility to carry out the survey without accessing the land/structure butinstalling the IBIS system in its proximity

GeoradarIBIS System


Landslide monitoring

Active earth slide evolving into an earth flow in the lower part

Very fast movements (m/days) during re-activation periods

GeoradarIBIS System


IBIS-L IBIS-L

IBIS-L

DISTANZA DAL VERSANTE [m] 450-1300

APERTURA ORIZZONTALE ANTENNE [gradi] 38

RISOLUZIONE IN RANGE [m] 0.5

RISOLUZIONE IN CROSS-RANGE [mrad] 4.5

ACQUISIZIONI PER ORA - 9

DURATA SESSIONE [ore] 24

IBIS-L System set-up


GeoradarIBIS System


1

0.5

More than 40.000 measurement points are identified on the quality map

Geocoded quality map Picture taken from the radar location


GeoradarIBIS System


[mm]2

-50

Geocoded Line Of Sight Displacement Map

Geocoded cumulative displacement map (1 h)

GeoradarIBIS System


[mm]2

-50



GeoradarIBIS System


[mm]2

-50


Zona AZona BZona CZona D

Identification of moving portions of the slope

GeoradarIBIS System


Line Of Sight Displacement Time Series

ZONA A - movimento di alcuni punti di misura selezionati

Mappe di spostamento

cumulato dopo 24 ore

Displacement time series

GeoradarIBIS System



ZONE A - displacement of a few points




GeoradarIBIS System





Displacement time seriesZONE B - displacement of a few points

GeoradarIBIS System


Line Of Sight Displacement Time SeriesLine Of Sight Displacement Time Series



ZONE C - displacement of a few points


GeoradarIBIS System

Following a 80,000 ton slipoccurred in late 2009 andthe consequent closure ofoperations, an IBIS-M unitwas deployed in January2010 at the Pipeline pit inCortez, Nevada, owned byBarrick.

The IBIS-M system was aimed at providing early warnings and support forgeotechnical evaluation purposes.

After 7 months of rental of the equipment, in July 2010, the IBIS-M unit waspurchased by Barrick.

IBIS-M for open-pit mines

GeoradarIBIS System

DISTANCE FROM THE SLOPE [m] 800 – 1500

ANTENNA BEAM WIDTH [deg] 68NUMBER OF POINTS - 90.000

RANGE RESOLUTION [m] 0.5

(1.64 ft)

CROSS-RANGE RESOLUTION [mrad] 4.5SCANNING TIME [min] 5

IBIS-M for open-pit mines

GeoradarIBIS System

Dispatch RoomGuardian Software24/7 monitoring for alarmsStatus alarms/emailsGeotechnical alarms/emails

Wireless link+/‐ 200‐300KB every 6‐7 mins

Shelter (pit rim)IBIS‐M basic configuration unitFully enclosed (HVAC, WiFi)Mine grid power supplyBackup power (1 day with genset)IBIS Controller Software24/7 functioning

Engineer’s laptop

VPN, VNC connections

IBIS-M set-up

GeoradarIBIS System

Sensor unit

Linear scanner

Processing unitDedicated laptopPanasonic CF19IP65

Power supply unit(IBIS and laptop)

Base

Shelter

IBIS-M set-up

GeoradarIBIS System

Cumulative displacement from 03/02 to 18/02

GeoradarIBIS System


GeoradarIBIS System

Cumulative displacement from 03/02 to 21/09: time series

GeoradarIBIS System


Cancano Dam view

Dam plan

Dam characteristicsDam Type Gravity archLocation Alpi Retiche - Italy

Dam height (m) 125.5Crowing length (m) 381

Survey performed with the Surveying Dept. of Milan Polytechnic

Dam monitoring

GeoradarIBIS System


IBIS-L configuration• Dam-sensor distance: 400m

• Range resolution: 0.5m

• Angle resolution: 4.7mrad

• Sampling interval: ca. 9 minutes

Dam monitoring

GeoradarIBIS System


dam

rocks

SNR MapZoom on dam areaDam monitoring

GeoradarIBIS System


Dam Power map projected over plan

Dam monitoring

GeoradarIBIS System


Selected pixel L.O.S. displacement – 5 pixel belonging to the dam crown

Dam monitoring

GeoradarIBIS System


Point displacement comparable with dam coordinometer

Dam monitoring

GeoradarIBIS System


IBIS-L sampling interval: 9minPendulum sampling interval: 4hours

Crowining point displacement comparison between IBIS-L and coordinometer measure

Dam monitoring

GeoradarIBIS System

IBIS Guardian

• Real time processing with automatic atmospheric corrections

• Alarm generation with user-defined levels and multiple alarm criteria

• Fully georeferenced outputs• 3D interactive data handling• User defined zones for alarm

generation• Exportability of outputs to GIS and

mine planning software

IBIS Guardian

77

GeoradarIBIS System

March – April 2010

Stable

Moving

Alarm

Displacement Map - in mm for every pixel- negative displacements are in approach

Velocity Map- in mm/h for every pixel

Quality Map- Values between 0-1- Reliability of the pixel for

distance measurements

Hazard Map

-Variable number of levels and thresholds-Automatically updated with the last data-Exclude / Differentiation of areas- Trigger the alarms:

- PC SCREEN- SMS- EMAIL

DEM

GUARDIAN typical output

GeoradarIBIS System


Static monitoring of a new bridge:

Determination of displacement of the bridge during a static load test

Bridge testing: static live load test

Viaducts crossing Forlanini Avenue (Milan, Italy)

Bridge beams are good reflecting points

GeoradarIBIS System


0 10 20 30 40 50 60 7030

40

50

60

70

80

90CB

G

HD

E F

A

SNR

(dB

)

Ground-Range (m)

Range profile of P2-S – P3-S span

IBIS-S installation


GeoradarIBIS System


LVDT

0 200 400 600 800 1000 1200 1400-30

-20

-10

0

10

B D F Hdi

spla

cem

ent (

mm

)

time (s)

LC1


GeoradarIBIS System


LVDT

0 200 400 600 800 1000 1200 1400-30

-20

-10

0

10 IBIS-S LVDT

-20.50-15.62

-8.84

disp

lace

men

t (m

m)

time (s)

LC1


GeoradarIBIS System


0 200 400 600 800 1000 1200 1400-40

-30

-20

-10

0

10 IBIS-S LVDT

-32.76-25.20

-14.28

disp

lace

men

t (m

m)

time (s)

LVDTLC2


GeoradarIBIS System


LC1, P2-S – P3-S span:Deformed elastic curveprovided by IBIS-S


GeoradarIBIS System


Measurement objective: comparison with accelerometers, resonancefrequencies and modal shape retrieval

Central arch length (m): 62.5

Bridge testing: dynamic test of bridge span

GeoradarIBIS System


To make a comparison between theresults of IBIS-S system andaccelerometers system 6 corner reflectorwere installed at the same position ofaccelerometers


GeoradarIBIS System


Bridge photograph and range profile


GeoradarIBIS System


Velocity comparison for Test Point 22

Velo

city

[mm

/sec

]Ve

loci

ty [m

m/s

ec]

Time [sec]

Time [sec]

IBIS-S

accelerometer

Zoom on the first 15 sec – direct comparison

IBIS-Sacc


GeoradarIBIS System


Frequency analysis comparison on

3000sec acquisition duration

IBIS-S

acc

Acc detected frequency

IBIS-S detected frequency

Percentage error

Hz Hz %

2,617 2,595 0,84

3,164 3,182 -0,576,641 6,608 0,50

8,086 8,077 0,11


GeoradarIBIS System


f = 2.617 Hz

f = 6.641 Hz f = 8.086 Hz

f = 3.164 Hz

Modal shape obtained by accelerometer data


GeoradarIBIS System


Modal shapes comparison

0 23 46 69 92 115-1.2

-0.6

0.0

0.6

1.2 Accelerometer IBIS-S sensor

Nor

mal

ized

Mod

e S

hape

Distance along deck (m)

0 23 46 69 92 115-1.2

-0.6

0.0

0.6


Nor

mal

ized

Mod

e S

hape


f=2.617Hz

f=3.164Hz


GeoradarIBIS System


f=6.641Hz

f=8.086Hz

0 23 46 69 92 115-1.2

-0.6

0.0

0.6


Nor

mal

ized

Mod

e S

hape


0 23 46 69 92 115-1.2

-0.6

0.0

0.6


Nor

mal

ized

Mod

e S

hape


Modal shapes comparison


GeoradarIBIS System


Bridge testing: Cable-stayed bridgesApplication goal: dynamic analysis done through ambient vibration testing

(AVT) aimed at:- Identify the amplitude of the cable vibrations;- Identify the natural resonant frequencies and the cable dumping

factors- Evaluate the tension and the operating strain of cables to verify the

correct distribution of loads and the temporal variation of tensions alongthe bridge life

GeoradarIBIS System


Advantages in the use of IBIS-S:

- Provide displacement measurements (useful to evaluate theamplitude of vibrations)

- Very accurate measurement: an order of magnitude higher thanLDV

- No traffic shut-done needed (IBIS can be installed under thebridge or beside the bridge towers)

- Simultaneuous measurement on a large number of cables(potentially all cables of each side at once)

- Rapid installation and measurement set-up

Bridge testing: Cable-stayed bridges

GeoradarIBIS System


Geometrical sketch of IBIS-S set-up:

IBIS on the bridge

IBIS below the bridge


GeoradarIBIS System


Olginate bridge (Italy)


GeoradarIBIS System


IBIS-S set-up

Range ProfileDisplacement graph

0 100 200 300 400 500 600 700 800 900 1000-2,0

-1,6

-1,2

-0,8

-0,4

0,0

0,4

0,8

Interferometro IBIS-SDisp

lace

men

ts (

mm

)

Time (s)

Olginate bridge (Italy)


GeoradarIBIS System


Example: Olginate bridge (Italy)

Comparison with accelerometers

Piezo-electric accel. WR 731A

260 270 280 290 300 310-800-600

-400-200

0200

400600

800

Sensore WR731A Interferometro IBIS

Acc

eler

atio

n (m

m/s

2)

Time (s)

260 270 280 290 300 310-500-400-300-200-100

0100200300400500

Sensore WR731A Interferometro IBIS

Acc

eler

atio

n (m

m/s

2)

Time (s)


GeoradarIBIS System


Example: Olginate bridge (Italy)

Frequency Domain Analysisf = 3.906 n

02

46

8101214161820222426

0 1 2 3 4 5 6 7

n

frequ

enza

[Hz]

0 5 10 15 20 2510-7

10-6

10-5

10-4

10-3

10-2

10-1

Sensore WR731A

ASD

(m

m)2

/Hz

0 5 10 15 20 2510-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Interferometro IBIS

IBIS

Accel.

ASD

(m

m)2

/Hz

Frequency (Hz)

f1 (Hz) f2 (Hz) f3 (Hz) f4 (Hz) f5 (Hz) f6 (Hz)

IBIS-S 3.906 7.764 11.720 15.630 19.510 23.460

Accel. 3.809 7.495 11.470

Resonant frequencies

Cable S09'

IBIS-S Accelerometer

fexp(Hz)

Tension (kN)

fexp(Hz)

Tension (kN)

3.906 1883.1 3.809 1790.7

7.764 1860.0 7.495 1733.3

11.720 1883.7 11.470 1804.2

15.630 1884.5

19.510 1879.2

23.460 1886.9

1880 1776

Tension

Freq

uenc

y (H

z)

n


GeoradarIBIS System


High-rise structures: chimney testingMeasurement objective: measurement of the displacements of the old and newchimney and identification of their resonance frequencies

Old chimney New chimney

Chimney high: 183m

Measurement parameters:maximum range: 300 m

sampling frequency: 50 Hzrange resolution: 0.5 m

distance from the target: ~ 50 m

GeoradarIBIS System


Range profile of the new chimney

0 5 0 1 0 0 1 5 0 2 0 0 2 5 0-1 0

0

1 0

2 0

3 0

4 0

5 0T h e rm a l S N R - S u r v 0 2

R a n g e [m ]

SN

R [

dB]

High-rise structures: chimney testing

GeoradarIBIS System


Point located at the middle of the chimney, at a height of 121 m

Point located at the top of the chimney, at a height of 172 m

Horizontal displacement Frequency AnalysisNew chimney

100 200 300 400 500 600-0.5

0

0.5

1

1.5

2

time [sec]

Pro

ject

ed

Dis

plac

eme

nt [

mm

]

Rbin 266

100 200 300 400 500 600-0.5

0

0.5

1

1.5

2

2.5

3

3.5

time [sec]

Pro

ject

ed

Dis

plac

eme

nt [m

m]

Rbin 362

0 0.5 1 1.5 25

10

15

20

25

30

35

40

45

X: 0.38Y: 20.54

[mm

/Hz]

frequency [Hz]

0 0.2 0.4 0.6 0.8 1 1. 2 1.4 1. 6 1.8 25

10

15

20

25

30

35

40

45

X: 0.38Y : 22.3 8

[mm

/Hz]

frequency [Hz]Identified frequency: 0.38 Hz

High-rise structures: chimney testing

ibis-l: ibis-l: an innovative solution for remote monitoring of displacements on slopes and...

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