The document summarizes a geotechnical analysis of material from Lake Badana in Italy that is being considered for reuse as inert material in concrete mixtures. Laboratory tests found the material contains no asbestos or harmful substances above legal limits. A stability analysis found the overall risk of landslides on the lakeshore is modest, with possible landslides only on the left flank. The analysis concludes the excavated material is suitable for reuse as inert in concrete after processing.

1. University of Genoa
Faculty of mathematical, physical, natural sciences
Department of environmental studies and natural
resources
 GEOTECHNICAL ANALYSIS OF MATERIAL COMING
FROM LAKE BADANA WITH A VIEW TO A PROSPECTIVE
REUSE AS INERT IN CONCRETE MIXTURES
 Candidate: Lorenzo Rinaldi
Supervisors:
 Prof. Andrea Cevasco
 Doc. Carlo Baracco
 Prof. Laura Crispini

2. Preamble:
 The Badana dam is situated within the Bosio municipality of (AL) ; it cuts the flow of the
namesake torrent –left tributary of Gorzente torrent – and was completed in 1914. It
created a water reservoir of a volume of 4.69 Mm3.
 Due to the events of February 2006 -conspicuous leakages between the bottom of the dam
and the bedrock- it was implemented, as first safety measure, the emptying of the reservoir.
 Additional research regarding the environmental risk, combined with safety regulations, has
highlighted the urgency of carrying out excavations-both in the bedrock and at the bottom
of the dam. In the following table we can see a first estimation of the total volume of the
excavation project.
 Excavation of short tunnels in the dam.
5450m3
 Excavation of a superficial drain system
1500m3
 Excavation of a new temporary road to
access the site 700m3
 Total
7650m3

3. To the abovementioned volume of the excavation project, it should be added
a safety margin of 20%, which will bring the final estimation to a total of
9150 m3
 Concerning the excavation of loose material withing the boundary of the
reservoir-material that seems to present an average thickness of 1,5m- a
first appraisal leads us to believe that the resulting volume may reach
19000 m3
 Given the size of the excavation plan, the Italian law compels the company
responsible for the project –Geotechnics Inc.- to massively reuse the
material, with a view to environmental restoration.
 A thorough geotechincs campaign has been planned to grant the full
fucntionality of the dam after the excavation project.

4. Aims:
1) CLASSIFICATION OF THE BEDROCK THOUGH RMR89 INDEX
2) STABILITY ANALYSIS OF THE FLANKS OF THE MOUNTAINS GIRDING LAKE
BADANA
3) ANALYSIS OF THE GEOTECHNICAL CHARACTERISTICS OF THE DAM
4) LABORATORY ANALYSES TO ENSURE THE SUITABLITY OF THE MATERIAL
COMING FROM THE EXCAVATION PROJECT FOR A PROSPECTIVE REUSE
AS INERT IN CONCRETE MIXTURES.

5. Methods:
 1) GEOTECHNICAL ANALYSIS
 2) DATA PROCESSING THROUGH DIPS AND ROC DATA
 3) LABORATORY ANALYSES

6. Geological background
 The area is mainly characterized by
bedrocks belonging to the northern
part of the geological group named
Gruppo di Voltri . These bedrocks
are partly overlapped by deposits of
more loose material pertaining to the
Bacino Terziario Piemontese.
 Within lake Badana three different
bedrocks can be found:
 Serpentiniti milonitiche ad
antigorite
 Peridotiti lherzolitiche del
MonteTobbio
 Brecce di Costa Cravara
Figura 1 - Carta geologica dell'area circostante la diga e l'invaso di Badana
Unità Erro-Tobbio, Ultramafiti tettonitiche più o meno serpentinizzate associate a filoni
discordanti di gabbri meta gabbri ecologitici
Bacino Terziario Piemontese
Faglie
Peridotiti serpentinizzate
Serpentiniti milonitiche a struttura
scistosa
Brecce di Costa Gravara, brecce grossolane a clasti
prevalentemente lherzolitici

7. BRECCE DI COSTA CRAVARA
SERPENTINITI MILONITICHE
PERIDOTITI LHERZOLITICHE

8. Geomechanical characterization of the bedrocks:
 Samples have been collected and analysed
in 15 different stations along the
lakeshore. For each sample, the following
characteristics have been analysed:
 - Orientation
 - Roughness (I and II order)
 - Alteration
 - Hydraulic conditions
 - Openness
 - Joint wall compressive strenght (JCS)
through sclerometer.
Figura 2 - Ubicazione delle stazioni di rilevamento geomeccanico
1
2
3
8
9
10
4
11
15
7
14
6
13
5
12
Baracco C., Minetti L. (2000)

9.  The information gathered from the analysis enabled us to classify the
bedrock through the RMR89 index
The emptying of the
reservoir allowed us to
thoroughly verify the
stability of the
lakeshore by taking
samples in areas that
normally would be
underneath the water
surface.

10. CLASSIFICAZIONE DELL'AMMASSO ROCCIOSO-SISTEMA RMR89
Località: Diga di Badana ed invaso
Litologia : peridotiti serpentinizzate/sepentiniti milonitiche
N. PARAMETRO VALORI PUNTI FONTE
compressione 25-50MPa 4 mis.sclerom.(1)
1 monoassiale
roccia integra 50-100MPa 7 prove comp.monoas.(2)
25-50% 8 osservazione
2 <25% 3 carote
3 spaziatura dei rilievi su affioramento
giunti osservazione carote
4 condizioni dei vedere
giunti tabella 3bis
condizioni asciutti 15 osservazione
5 idrauliche dei umidi 10 dei giunti in sito
giunti
B orientazione dei
giunti
TOTALE PUNTI 62
RMR 38
CLASSE
AMMASSO
n.c
II - (III) buona / (discreta)
IV - (III) scadente / (discreta)
RQD
200-600mm
60-200mm
10
8
22/13

11. N. PARAMETRO VALORI PUNTI FONTE
1-3m (bassa) 4 rilievi su
3-10m (media) 2 affioramento
<0,1mm (chiusi) 5 rilievi su affioramento e
0,1-1mm (legg.aperti) 4 osservazione carote
rilievi su affioramento e
osservazione carote
assente 6 rilievi su affioramento e
sabbioso <5mm 4 osservazione carote
legg. / mod. alterati 4 rilievi su affioramento e
alterati 2 osservazione carote
TOTALE 22/13
NOTE I valori totali indicati rappresentano in campo di variabilità delle condizioni dei
giunti
CLASSIFICAZIONE DEI GIUNTI - SISTEMA RMR89
E4 riempimento
E5 alterazione
E3 scabrezza
leggermente scabri
lisci
3
1
E1 persistenza
E2 apertura

12. DISCONTINUITY ORIENTATION
 Stability analysis:
 The data gathered from the structural analysis have been processed using DIPS (Hoek
and Diederichs, 1989), to construct the following diagrams:
DENSITY OF THE POLES

13. PREFERENTIAL PATTERNS OF DISCONTINUITY

14.  Although there is a significant dispersion of the discontinuities, four preferential
patterns have emerged:
 F1 dip immersion between 180° and 260°, inclination
between 30° and 50°.
 F2 dip immersion between 320° and 6°, inclination between 65° and
80°.
 F3 dip immersion between 340° and 10°, inclination between 5° and
15°.
 F4 dip immersion between 140° and 170°, inclination between 50° and
almost vertical.
 The presence of random plans of discontinuity could be justified by the
limited number of measures it has been possible to take.

15. Knowing the JRC and the JCS, the shear strength of rock discontinuities can be
calculated by using the Barton-Bandis failure criterion.
The strength of rock discontinuities has been calculated for the following conditions,
which are the most common and representative within the water reservoir:
Condition 1: JRC= 4 JCS=20MPa
Condition 2: JRC= 6 JCS=20MPa
Condition 3: JRC= 8 JCS=20MPa
Condition 4: JRC= 4 JCS=10MPa
Condition 5: JRC= 6 JCS=10MPa
Condition 6: JRC= 8 JCS=10MPa
For each of these conditions we have determined the friction angle by using
ROCDATA.
The data obtained indicate an oscillation in the values of friction angles from a
minimum 27° to a maximum of 32°.

16. Breaking limits for condition 6 (JRC=8 , JCS=10 MPa)

17. Station 1
DIPS has been used to evaluate the stability of the lakeshore. In particular,
it has been analysed which discontinuity plans, combined with a certain
friciton angle, can generate unstable conditions and landslides.

18. Having taken samples all along the lakeshore enables us to construct
an overarching table regarding the risk of landslides within the
reservoir.
1 ALTO J2 MODERATO J1-J3 ALTO
2 NON SUSSISTE LIEVE J1 NON SUSSISTE
3 MODERATO J(random) NON SUSSISTE NON SUSSISTE
4 NON SUSSISTE MODERATO J2 ALTO
5 NON SUSSISTE NON SUSSISTE LIEVE
6 NON SUSSISTE ALTO J4 ALTO
7 NON SUSSISTE MODERATO J(random) NON SUSSISTE
8 NON SUSSISTE NON SUSSISTE NON SUSSISTE
9 NON SUSSISTE ALTO J2 ALTO
10 NON SUSSISTE NON SUSSISTE NON SUSSISTE
11 NON SUSSISTE NON SUSSISTE MODERATO
12 NON SUSSISTE NON SUSSISTE NON SUSSISTE
13 NON SUSSISTE LIEVE J2 MODERATO
14 NON SUSSISTE NON SUSSISTE NON SUSSISTE
15 NON SUSSISTE NON SUSSISTE NON SUSSISTE
pochi dati per valutazioni
attendibili
QUADRO RIASSUNTIVO DEL LIVELLO DI RISCHIO DI INSTABILITA'
MODO DI ROTTURA
OSSERVAZIONI
J1XJ2, J2XJ3
J(random)
J1XJ2, J2XJ3
pochi dati per valutazioni
attendibili
la scistosità non genera
blocchi di dim. sign.
J1XJ3
J(random)
J2XJ3
J2XJ3, J2XJ4, J3XJ4
SCIVOLAMENTO DI
PIANI
SCIVOLAMENTO DI
CUNEI
RIBALTAMENTO
STAZIONE
SET SET SET

19. With a view to a future reuse as inert in concrete mixtures, the material coming
from the excavation at the bottom of the dam has undergone several
laboratory analyses

20. Laboratory analyses:
All the analyses have been carried
out by the laboratory C.S.G.
Palladio of Vicenza.
Eight samples have been
examined to evaluate the possible
presence of Asbetos and.
Furthermore, to verify the
concentration of harmful minerals
in the body of the dam, further
chemical analyses have been
carried out on 3 samples.
Sample Sand Thickness of
the loose
material at
the bottom
of the dam
Parameter Unit of
measure
Value
Crisotilo % p/p <0.1
Crocidolite % p/p <0.1
Amosite % p/p <0.1
Tremolite % p/p <0.1
Antofillite % p/p <0.1
Actinolite % p/p <0.1

21. Conclusions:
 The bedrock surrounding the Badana reservoir presents a RMR89 index
between 38 and 62. Therefore, the quality of the rock varies from below-
average (Class IV) to good quality (Class II).
 From the investigation, carried out using DIPS, it can be asserted
that the global risk of instability of the lakeshore is generally
modest.
 Possible landslides can only concern the left flank (stazions 1-9), while the
right flank does not present conspicuous risk.
 The left flank also presents (stations 4;9) critical conditons for the
detachment of rock wedges.

22.  None of the 8 samples have shown a sufficiently high concentration of
asbestos to create health concerns.
 Moreover, the concentration of potentially harmful substances such as
Nickel, Cadmium, Arsenic in the body of the dam is well within the limits
imposed by the lItalian legislation (as established by the D.Lgs 16 Jan.
2008 n° 4).
 Therefore, the material coming from the excavation project
presents all the required characteristics to be wholly reused-after
the necessary process of chipping- as inert in concrete mixtures.