CONTRIBUTION OF D.M.S. MONITORING SYSTEMS IN THE ANALYSIS

OF SLIDE MICRO-MOVEMENTS FOR EARLY WARNING

MANAGEMENT, RISK ASSESMENT AND EVALUATION OF

MITIGATING ACTIONS

D.M.S. IUEAuto Blocking 3D

D.M.S. 3D system (Figure 2) has beenspecifically studied for 3 dimensionmeasurement in drilling holes, so as torecord deformations directly on rocks ors o i l s , a n d t o e x e c u t e m u l t i -p i e z o m e t r i c / m u l t i - p o r e p r e s s u r emeasurements in the same monitoring hole.The system is composed of modules (E.D.80 millimeter, with packers for direct holeanchorage), linked by special 3D flexiblejoints with high traction resistance (up to100 KN) and maximal extension between10 and 140 mm.. The system is particularlyeffective in the analisys of very fracturedrocks and of consolidation and subsidencecases.

D.M.S. IU 2D

D.M.S. IU is composed of a sequence of hard tubular modules(stainless steel elementsAISI 304 diam. 48.3mm), each containing oneor more geotechnical sensors and electronic boards for data control,A.D. conversion and transmission. D.M.S. IU monitoring system(Figure 3) requires a casing with a minimum diameter of 60 mm. Nointrinsic limits exists to the number of measurement modules. The useof a pressure sensor requires a slotted pipe. The modules are linked byflexible joints that allow strong, continuous adaptability to bends andtwists of the casing whilst maintaining rigorously the orientation withrespect to a reference system defined during installation. It is possibleto use different types of joints with traction resistance between 10 and50 KN. The system maintains the correct direction also without theinclinometric casing grooves or with damaged ones, so monitoring ispossible also inside smooth casings (diam > 2”). To protect the system,D.M.S. is equipped with internal special cables for power and signal.

APPLICATIONS:

1) Contextual multi-parametric monitoring on the inside of the same drilling hole2) Possibility to recover the column

4) Forecasting of landslide movements by analysis of micro-movements - Civil protection applications5) Possibility of rehabilitation of strongly deflected inclinometric casings which are no more measurable with traditional inclinometric system6) High space resolution of the measurements7) Modular structure and cost reduction8) Multiparametric monitoring for landslide 2D/3D modelling

3) High adaptability of the monitoring column to deformations

D.M.S. ADVANTAGES

D.M.S. MONITORING EXAMPLES:

Figure 1. D.M.S. System

Figure 3. D.M.S. IU 2D

Figure 2. D.M.S. IUE Auto Blocking 3D

Slope stability, landslides

Dams monitoring

Cuttings

Roads stability Ground and buildingsresponse to tunnelingGround and buildingsresponse to tunneling

0

5

10

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20

25

30

-10 -8 -6 -4 -2 0 2 4 6 8 10

Error - mm

Field Accuracy inclinometer Probe Survey(Total Error) (Mikkelsen)

Inclinometer Probe Survey (Random Error)

(Mikkelsen)

IPI Accuracy Criterion (Dunnicliff,La Fonta;La Fonta & Beth)

DMS Accuracy

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30

-10 -8 -6 -4 -2 0 2 4 6 8 10

Error - mm

Depth

mField Accuracy inclinometer Probe Survey(Total Error) (Mikkelsen)

Inclinometer Probe Survey (Random Error)

(Mikkelsen)

IPI Accuracy Criterion (Dunnicliff,La Fonta;La Fonta & Beth)

DMS Accuracy

Comparison of accuracy and precision of monitoring data

Knowing the accuracy and precision of inclinometric data in landslides and engineering works is very relevant, particularly when even thesmallest indication of displacement is a matter of concern for an early warning in public safety, risk analisys/assestment and evaluation ofmitigating actions in the shortest time .

relevant precision increase, depending on the statistically redundant data collected by sensors, the increase invertical discretization and the good coupling of the modules with the casing (see Figure 4 CMEM 2005, Malta).D.M.S. monitoring data reveal

The results of 'in situ' test performed with D.M.S. I IU columns equipped with inclinometric biaxial sensors, 30 m string length, 30 sensorsevidence an accuracy in equal to ±0.5mm.L.S.T. (long stability tests-3 months)

Albera Landslide

Albera-Vendersi Landslide

Slip surfaces micromovements

0

0.4

0.8

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1.6

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2.4

2.8

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8

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rom

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ts(m

m)

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Slip surface II (Depth 14m)

Cumulative Displacements (g.l.)

D.M.S. Monitoring

Technical Service Trebbia and Nure Basin’sWorkstation

Control UnitGSM - GPRS GSM - GPRS

Photovoltaic cells

Technical service /

Project Engineer /

Monitoring Engineer

Technical Service Trebbia and Nure Basin’sWorkstation

Control UnitGSM - GPRS GSM - GPRS

Photovoltaic cells

Technical service /

Project Engineer /

Monitoring Engineer

D.M.S.( ) is a new multi-parametric in-place instrument for stability control anddifferential monitoring of soils, rocks, engineering works, in casing or borehole (Figure 1), designed mainly to evaluate danger levels ofpotentially instable areas. D.M.S. can be assembled 'in situ' forming an instrumented column, connecting the required number of modules, eachcontaining one or more sensors and the electronic boards for data collection and transmission.The modules are linked by special 2D/3D flexible joints that allow strong, continuous adaptability to bends and twists of the drilling hole, whilstmaintaining rigorously the orientation with respect to a reference system defined during installation.The link between sensors and control unit is realized with the digital mode protocol RS 485, for a maximum of 128 sensors linked to the centralunit basic configuration. The control unit provides for the readings at regular time intervals, according to the requested program (defaultsampling: 1 reading/min/sensor, recording 1 average value/h per sensor).Remote control, download, storage and processing of data are made with a remote control station, equipped with GSM/GPRS integratedtransmission and specific software “GEOMASTER”. The “D.M.S. Report”software enables data processing and the graphic display.

Patent pending and trademark application C.S.G. S.r.l. - ITALY

The Albera landslide (Northern Apennines) is of a complex-composite type involving the

Vendersi village with an intermittent cinematic. The dimensions are relevant: length: 1,370 m,

width: 519 m max, difference in height: 380 m, surface area: 51 x 104

m² and estimated volume:

11 x 106

m³ circa) and concerns the medium slope (Figure 5), crown altitude 950 m. a.s.l., toe

altitude 570 m a s.l.

A DMS IU column was installed in dicember 2005 by means of an helicopter (Figure 6), inside

a 40 m deep drilling hole, rigged with a 3” slotted casing. The continuous monitoring is active

with one reading/min/ per sensor, 1 averaged values each hour, GSM transmission.

This system monitors the displacememt of the landslide body and the water table variations,

making it possible to define and design urgent remediation activities and to compare phenomena

and define critical precipitation thresholds for early warning.

The continuous monitoring shows clearly (Figure 7) depth and velocity of 2 main rupture

surfaces just a few days after installation, due to a rapid snow melting phase in winter season;

this results is not achievable with traditional instrumentation (see Vendersi-Slip Surfaces

Micromovements).

Figure 4. Accuracy comparison

Figure 5. Albera Landslide

Figure 6. Albera D.M.S. installation

Figure 7. D.M.S. Albera, slip surfaces

Figure 8. S.Stefano Displacement - Water level vs Time

The D.M.S. in S.Stefano Belbo (Langhe area) was installed to monitor a sector of a complex-composite landslide in a high risk areathat envolves the unique access to the Belbo Valley during main flood events.In order to start urgently a remediation activity, a continuous monitoring program was started, financed by the National CivilProtection.D.M.S. column has been installed close to the road along the unsafe sector in June 2005, using 11 biaxial inclinometric modules, eachlong 1m, and 1 piezometric module, inside a slotted PVC, 80 mm diameter casing.The reported data refer to january to march 2006 monitoring period along the 9 months of continuous recording, with one reading/min/per sensor, and 1 average values each hour.The column shows a main sliding surface occurring at 7.5 m bgl (Figure 8) with intermittent activity (V2=0.3 mm/d period 31/01-11/01; V4=1.65 mm/d period 22/02-03/03, V5=0.4 mm/d period 03/03-07/03). A main displacement phase starts with a delay time of4.5 days after water table raise during february; triggering factor: snow melting mixed to rain.

S.Stefano Belbo landslide

L. Foglino, (1) M. Lovisolo (1) A. Della Giusta (2)

(1)C.S.G. S.r.l. (2) University of Padova

1/2

/06

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surf

ace

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pla

cem

ent(m

m)

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-4

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-2.5

-2

-1.5

-1

Wate

rta

ble

(mbgl)

Water table

Slip surface displacement

D.M.S. S.STEFANO BELBOLANDSLIDE TRIGGERING- DISPLACEMENT ANALYSISMONITORING PERIOD: JANUARY - MARCH 2006

V1=0 mm/d V2=0.3 mm/d

V3=0 mm/d

V4=1.65 mm/d

V5=0.4 mm/dV6=0 mm/d

4.5 dd

Cumulative Displacement Module

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30.00

0.00 0.20 0.40 0.60 0.80 1.00

Displacement [cm]

D e p t h [ m ]

Report N. 4Date:

17/02/2006

3.11.05

Report N. 3

Date:06/02/2006

3.12.14

Report N. 2

Date:

01/02/2006

3.12.45

Report N. 1

Date:

15/01/2006

3.16.02

Report N. 0

Date:30/12/2005

9.02.54

Surface of rupture 1Surface of rupture 1

Surface of rupture 2Surface of rupture 2

C.S.G. S.r.l.Centro Servizi di GeoingegneriaC.S.G. S.r.l.Centro Servizi di Geoingegneria15011ACQUITERME(AL)viaTogliatti 8 - ITALY- tel. +39144356177 fax +39144350344 web www.csg-geo.it email info@csg-geo.it