Post on 20-Oct-2018
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Tutorial on QRARockfall hazard risk assessment.
Andorra la Vella, E. Pyrenees
Jordi Corominas
Department of Geotechnical Engineering andGeosciences
Civil Engineering School. BarcelonaUPC
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
What is the problem?
Location of Andorra la Vella (AV) – Santa Coloma
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
What is the problem?
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
For QRA we need answers to the following questions
Where the rockfall will takeplace?
How often?
How far will it travel?
What magnitude (intensity) will it have?
What are the potentialdamages?
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Risk for properties (i.e. buildings)
R(P) = P(L) x P(T:L) x P(S:T) x V(D) X C
R(P): expected annual loss due to landsliding (€/yr)P(L): probability of occurrence of a landslide of a given
magnitudeP(T:L): probability of a landslide reaching the building levelP(S:T): probability of the building being on the landslide pathV(D): vulnerability of the building C: cost of the building
the analysis must consider all landslide magnitudes and all the potentially affected buildings
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Risk for persons (i.e. inside a house)
Individual risk
R(ILOL) = P(R) x P(T:R) x P(S:T) x P(T:P) x P(S:P) x V(D)
R(ILOL): annual probability of loss of lifeP(R): probability of occurrence of a rockfall of a given
magnitudeP(T:R): probability of a rockfall reaching the house levelP(S:T): probability of the house being on the rockfall pathP(T:P): probability of the person being in the houseP(S:P): probability of the person being in the rockfall path V(D): vulnerability of the person
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Identification of rockfall sources
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Definition of basin and associated talus slopes
Spatial unit: basin
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
How often? P(R)
Couloir
ofLuixent
Passader
Couloir
ofC
irera
Couloir
ofR
oquesB
lanques
Couloir
ofPica
Couloirof
Colld'Eres
Couloir of
Couloirof
Boneta
Forat Negre
Alzina
of
Couloir
Basera
wedge
Basora Mateu
rock wall
Jan-1996
1974
Dec-1983
End of 1960-69 decade
May-2001
Jan-1997
Several events before 1974
Jan-19941968, 1984, other events between
these years
Apr-2000
1962
About ten events between 1956 and
1985
250 m
Rockfall of known age
Rockfall with only an approximate age
Plot of tree-ring sampling
Ramenada
Apr-1999
BetweenJul-1998 and
Jan-1999
Roc de
rock wallSant Vicens
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Frequency (PR)
Estimated return period from:
Site
Historical record
Forat Negre 5 Alzina couloir 15 Boneta and Cirera
couloirs 10
Bassera Mateu > 25 Ramenada couloir 50 Coll d'Eres couloir 25 Pica couloir 25
PR = 1/TR
Frequency obtained at the base of thetalus slopes
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Preparing magnitude-frequency relation
Location Percentage of blocks of different volumes
≤1 1-5 >5 m3 Forat Negre 83,5 15,97 0,51 Alzina couloir 83,5 15,97 0,51 Boneta couloir 83,5 15,97 0,51 Basera Mateu 83,5 15,97 0,51 Ramenada c. 83,5 15,97 0,51 Coll d’Eres c. 83,5 15,97 0,51
Location Percentage of block of different volumes 0,5 1 2,5 5 10 m3 Forat Negre 49,6 33,9 14,5 1,47 0,51 Alzina couloir 49,6 33,9 14,5 1,47 0,51 Boneta couloir 49,6 33,9 14,5 1,47 0,51 Cirera couloir 49,6 33,9 14,5 1,47 0,51 Basera Mateu 49,6 33,9 14,5 1,47 0,51 Ramenada c. 49,6 33,9 14,5 1,47 0,51 Coll d’Eres c. 49,6 33,9 14,5 1,47 0,51 Pica couloir 49,6 33,9 14,5 1,47 0,51 Pica talus 49,6 33,9 14,5 1,47 0,51
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Assessment of travel distance (P(T:R))
Frequency obtained at thetalus slope.
Not necessary
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Impact probabillity (P(S:T)) and (P(S:P))
P(S:T)1 = LE/LD
P(S:T)2 = LB/LE
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Impact probability on buildings
Location Impact probability Length
talus (m) LD
Length buildings
(m) LE
Width of exposed
flat (m) LB Forat Negre 180 180 10 Alzina couloir 150 70 10 Boneta couloir 190 140 10 Basera Mateu 310 28 10 Ramenada c. 130 20 10 Coll d’Eres c. 120 120 10
LE
LD
LB
Block size (m3) LR Cubic root (m)
0,5 0.794 1 1
2.5 1.357 5 1.710
10 2.154
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Vulnerability (V)
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Case 2: one line of rockfall fences
Rockfall fences:
6 m height
2000 KJ absorbed kineticenergy
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Preparing magnitude-frequency relationLocation Percentage of block of different volumes 0,5 1 2,5 5 10 m3 Forat Negre 49,6 33,9 14,5 1,47 0,51 Alzina couloir 49,6 33,9 14,5 1,47 0,51 Boneta couloir 49,6 33,9 14,5 1,47 0,51 Cirera couloir 49,6 33,9 14,5 1,47 0,51 Basera Mateu 49,6 33,9 14,5 1,47 0,51 Ramenada c. 49,6 33,9 14,5 1,47 0,51 Coll d’Eres c. 49,6 33,9 14,5 1,47 0,51 Pica couloir 49,6 33,9 14,5 1,47 0,51 Pica talus 49,6 33,9 14,5 1,47 0,51
Case of Forat Negre basin
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Individual risk of lost of life
( )k
(ILOL) (R) (T:R) (S:T) (T:P) (S:P) (D:T)i = 1 i i
P = P × P × P × P × P × V∑
Different block sizes will give different values of P(S:P)
K is the number of block-size classesP(R), P(T:R) and P(S:P) depend on block size
For P(T:P), two scenarios have been considered:
The most exposed person: 20h/24h = 0.83
Average person: 14h/24h = 0.58
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Assessment of travel distance (P(T:R))
Numerical modelling
Inte
nsiv
eC
ours
eon
QR
A –
Bar
celo
na 2
008
Rockfall fence efficiency: new (P(T:R))