Document Actions

IJEGE-11_BS-Rudolf_Miklau-&-Suda

background image
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1083
DOI: 10.4408/IJEGE.2011-03.B-117
TECHNICAL STANDARDS FOR DEBRIS FLOW BARRIERS AND BREAKERS
f. RUDOLF-MIKLAU
(*)
& J. SUDA
(**)
(*)
Federal Ministry for Agriculture, Forestry, Environment and Water Management - Department IV/5
Torrent and Avalanche Control, Marxergasse 2 - 1030 Vienna, Austria - email: florian.rudolf-miklau@die-wildbach.at
(**)
University of Natural Resources and Applied Life Sciences - Institute of Structural Engineering
Peter Jordan Straße 82 - 1190 Wien, Austria - email: juergen.suda@boku.ac.at
flow processes from objects or areas at risk. (b
eRG
-
meisteR
et alii, 2009) Debris floods and debris flow
count among the most hazardous processes in torrents
and frequently cause severe damage and human casu-
alties. (R
udolf
-m
iklau
, 2009).
Since the beginning of systematic torrent control
in Austria 125 years ago barriers are constructed for
protection purposes. Until the end of the 1960s, solid
barriers were built at the exits of depositional areas
to prevent dangerous debris flows from reaching high
consequence areas. The development of solid barriers
with large slots or slits to regulate sediment transport
began with the use of reinforced concrete during the
1970s. In order to dissipate the energy of debris flows
debris flow breakers were designed since the 1980s.
By slowing and depositing the surge front of the de-
bris flow, downstream reaches of the stream channel
and settlement areas should be exposed to consider-
ably lower dynamic impact.
In the past the technological development of these
constructions was only steered by the experiences
of the engineering practice while an institutional-
ized process of standardization comparable to other
engineering branches was not existent. In future all
structures have to be designed and dimensioned ac-
cording to the EUROCODE standards. This was the
reason to establish an interdisciplinary working group
(ON-K 256) at the Austrian Standards Institute (ASI),
which has managed to developed comprehensive new
technical standards for torrent control engineering,
ABSTRACT
Debris flow barriers and breakers protect human
settlements, infrastructure and supply lines from tor-
rential disasters by dissipating the energy of debris
flow (floods), dosing (filtering) coarse solid compo-
nents and deflecting the flows from the areas at risk.
The function and design of these structures has to fol-
low the principles of the EUROCODE standards. In
order to establish a comprehensive “state-of-the-art”
for torrent control engineering an interdisciplinary
working group (ON-K 256) was established at the
Austrian Standards Institute (ASI) in 2006, which
develops new technical standards for load models,
design, dimensioning and life cycle assessment (tech-
nical standard ONR 24800 - series). The paper sum-
marizes the state of development concerning the func-
tion and design of debris flow barriers and breakers.
K
ey
words
: debris flow, torrent control, barriers function,
technical standards, action and impacts on barriers, design
and dimensioning
INTRODUCTION
Torrent control works includes by definition all
kinds of structures, which are realized in a torrent´s
catchment or stream bed, in order to stabilize the
bed and adjacent slopes, to regulate the discharge of
floods, to dose runoff and solid transport, to filter large
components (blocks, drift wood), to dissipate the en-
ergy of debris flow or to deviate (by-pass) hazardous
background image
f. RUDOLF-MIkLAU & J. SUDA
1084
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
Torrents are per definition perennially or intermit-
tently running water courses with steep slope, rapidly
changing discharge and massive solid transport (de-
bris, bedload, drift wood) at times. Extreme torrential
events comprise four definable displacement process-
es (i
veRson
, 1997; H
übl
, 2006; m
aRCo
, 2007):
• floods;
• fluvial solid transport;
• hyper-concentrated solid transport (debris floods) and
• debris flow (stony debris flow or mud-earth flow).
According to m
azzoRana
et alii (2009) the se-
quence of a torrent event corresponds to a process chain
that is triggered by heavy rain or snow thaw, inducing
intensive surface runoff, accretive erosion and slope
failures in the headwater area of the torrent catchment,
transforming into displacement processes downstream
and leading to the deposition of debris and drift wood
on alluvial fans, flood plains or gravel bars. This paper
is focused on the processes of debris floods and debris
flow as well as the corresponding protection structures.
As a rule the design of the torrential barriers has to
follow its function. (k
ettl
, 1984) According to ONR
24800:2008 the functions of torrential barriers can be
divided in the following functional types:
• Stabilisation and Consolidation;
• Retention;
• Dosing and Filtering;
• Energy dissipation.
Modern protection concepts in torrent control are
scenario-oriented and try to optimize different func-
tions in a chain of protections structures (function
chain
). For torrential displacement processes with
high concentration of solids the following types of
structures are applied (s
uda
& R
udolf
-m
iklau
, 2010):
BARRIER TYPES FOR RETENTION
The retention includes barriers that support the
tailback of debris in natural or artificial reservoirs. The
retention of debris is the storage of solids behind dams
or in artificial basins. For retention small slot barriers
are used (Fig. 2).
Retention of solids leads to a more or less per-
manent deposition of sediments. Retained debris regu-
larly has to be excavated or spilled from the reservoir
in order to keep the function effective. This concept is
mainly applied if the torrent downstream has no suf-
ficient transport capacity. This type of barrier function
is inefficient if directly exposed to debris flow.
including load models, design, dimensioning and life
cycle assessment of torrent control works (technical
standard ONR 24800 - series). The technical standard
series consists of the following parts:
• ONR 24800, Protection works for torrent control
- Terms, definitions and classification;
• ONR 24801, Protection works for torrent control -
Actions on structures;
• ONR 24802, Protection works for torrent control -
Design of structures;
• ONR 24803, Protection works for torrent control -
Operation, monitoring, maintenance.
The ONR 24800 and the ONR 24803 were already
published. ONR 24802 and ONR 24801 are available
as drafts and will be finished in 2010 respectively 2011.
These documents are based on and interact with EN
1990 (basic of structural design), EN 1992-1-1 (design
of concrete structures), EN 1997-7 (geotechnical de-
sign) and the related documents for the Austrian nation-
al specifications. The development of these standards
was accompanied by the publication of the first com-
prehensive technical hand-book on torrent control en-
gineering “state of the art” (b
eRGmeisteR
et alii, 2009).
DEBRIS FLOW BARRIERS AND BREA-
KERS: FUNCTION AND DESIGN
FUNCTIONAL CLASSIFICATION
Debris flow dams and breakers count among the
torrent control works. According to the “classical”
principles of torrent control (a
ulitzky
, 1980; k
ettl
,
1984), these structures have to be situated as close to
the source of hazard as possible and should be de-
signed for the predominant displacement process in
order to gain the maximum efficiency.
Fig. 1 - Debris breaker in the Rastetzebach torrent in Bad
Hofgastein (Salzburg)
background image
TECHNICAL STANDARDS FOR DEBRIS FLOW BARRIERS AND BREAKERS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1085
The function of debris breaker (Fig. 4a) is reached
in combination with a retention basin. The debris flow
enters the retention basin and interacts with the dis-
sipation structure. A part of the debris flow is depos-
ited in the basin. Due to the lower inclination of the
basins level and the flow resistance of the breaker the
kinetic energy of the process will be reduced. Debris
flow breakers are built with reinforced concrete and
situated as an upper most structure in a function chain.
A combination of “debris breaker” with other function
at the same barrier should be avoided. If one structure
is not sufficient the function may be distributed among
several consecutive debris breakers.
Crash dams (Fig. 4b) are as a rule situated on the
alluvial fan. If the function of process transformation
BARRIER TYPES FOR DOSING AND FILTERING
The dosing of debris means the temporary reten-
tion of coarse bedload during flood peak and the con-
trolled spilling of sediments with descending flood dis-
charge. The intermediate storage of the accumulated
material is designed to balance hazard mitigation and a
healthy riverine environment.
The filtering includes all kind of barriers that
serve the selective retention of coarse solid compo-
nents like boulders or drift wood from the flow proc-
ess. Filtering structures have to be designed in a way
that fine grained bedload can drift through without
being retained. The filtering should be limited to
those solids that cause the clocking of bridges and
narrows in the lower reach. As dosing/filtering barrier
large slot grill barriers are used. This type of barri-
ers controls the transport and deposition processes of
sediment, boulders and woody debris (Fig. 3).
BARRIER TYPES FOR ENERGY DISSIPATION
Measures with energy dissipation are designed
to reduce debris flow energy of debris flows (k
ettl
,
1984; J
enni
& R
eiteReR
, 2002). By slowing and de-
positing the surge front of the debris flow, downstream
reaches of the stream channel and settlement areas are
exposed to considerably lower dynamic impact.
The function of dissipation of debris flow energy
can either be reached by retarding the flow process
(breaking the surge front) or transforming the displace-
ment process. The purpose is reached either by massive
constructions that directly impact the debris flow proc-
ess (“debris breaker”) or by dams that cause a fall and
energy dissipation in the spilling pool (“crash dam”).
Fig. 3 - Schematic view of a large slot grill barrier for
dosing and filtering
Fig. 4 - Schematic view of (a) a debris flow breaker for en-
ergy dissipation and (b) a cascade of crash dams
for transformation of debris flow process
Fig. 2 - Schematic view of a small slot
barrier for debris retention
background image
f. RUDOLF-MIkLAU & J. SUDA
1086
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
dy debris flows can propagate over slopes of 5%
minimum. In the field muddy debris flows are re-
cognizable by sharp and well delineated limits of
the deposits and randomly distributed boulders
and gravel in a finer grained cohesive matrix.
- granular debris flows show a wide particle size di-
stribution too, but the content of clay-like material
is limited and coarse particles dominate. That is
why flow resistance is mainly due to frictional
and collisional contacts within the coarse frac-
tion. Energy dissipation is usually much larger
than in muddy debris flows, thus granular debris
flows require slopes steeper than 15° to flow. In
the field deposits of a mass of granular material,
from which the fine grained slurry drains easily,
and an irregular, chaotic surface give evidence of
this type of debris flow.
For torrent processes the frequency-intensity-
function shows an emergent behaviour (s
CHRott
&
G
lade
, 2008). That implies a limited predictability
of discharge from extrapolations of hydrological
data in case a certain threshold value is exceeded.
The event disposition of a torrent catchment, defined
as the entirety of all conditions essential for the
emergence of hazardous processes, consists of the
basic disposition comprising all factors immutable
over a long range of time (e.g. geology, soils) and
the variable disposition, which is the sum of all fac-
tors subject to a short-term or seasonal change (e.g.
precipitation, land use). If the variable disposition
of a torrent catchment is altered in the course of an
event (e.g. the water storage capacity of soils is ex-
ceeded), the debris potential is erratically increasing
resulting in a transition of the predominant displace-
ment process (e.g. solid transport is altered to debris
flood) and a non-linear increase of discharge. H
übl
(2010) illustrates this emergent behavior of torren-
tial flows by a multi-stage system status:
• status I comprises fluvial processes (floods, bedload
transport)
• status II includes debris flows and debris floods
• status III represents excessive (extreme) events
The design of debris flow barriers and breakers is
related to status II and III.
DESIGN CRITERIA FOR DEBRIS FLOw DAMS
The torrential event represents the entirety of
these processes occurring in a temporal, spatial and
cannot be reached by one dam only, a sequence of dams
(cascade) may be carried out.
FUNCTIONAL CATEGORY
According to ONR 24803:2009 the functional
category has to be determined for each torrent control
structure. Two categories of structures can be distin-
guished depending on the magnitude of consequences
of a functional or structural failure (e.g. dam break)
for the protection system itself or the area at risk
(ONR 24803:2009):
• standard structures;
• key structures.
This classification follows the principles of the
ÖNORM EN 1990 depending on the extent of poten-
tial damages. Torrential dams can be classified accord-
ing to the functions listed above. In any case, dams
with retaining, dosing, filtering and energy dissipating
function count among the key structures. Hence the
stability and usability of these structures is of major
importance for the safety of a whole protection system.
IMPACT ON BARRIER STRUCTURES BY
DEBRIS FLOW: DESIGN CRITERIA
TORRENTIAL PROCESSES
The characteristic displacement processes of tor-
rential events (floods, fluvial solid transport, debris
floods, debris flow) are definable by physical param-
eters like the rheology (newtonian/non-newtonian),
the volumetric concentration of solids, the density of
the liquid-solid-mixture, the kinematic viscosity, the
flow velocity or the relative discharge (ratio of total
discharge to water discharge).
Debris flows are a wide spread mass wasting proc-
ess in torrential catchments. This term is used for very
rapid to extremely rapid flow of saturated debris in
a steep channel. The components of these flows are
sediments varying from clay to boulder fraction and
water. The volumetric concentration of solids ranges
from 20 up to more than 60 percent, leading to bulk
densities up to 2.5 t/m³ (J
oHnson
, 1970). Depending
on the water to sediment ratio different types of debris
flows can occur. Based on the bulk mechanical behav-
iour of the flowing mixture two types of debris flows
in alpine environments are distinguished:
- muddy debris flow has a wide grain size distribu-
tion with a high content of clay-like material.
Due to the “relative” low shear resistance, mud-
background image
TECHNICAL STANDARDS FOR DEBRIS FLOW BARRIERS AND BREAKERS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1087
culate debris flow impact forces. The model according
to l
iCHtenHaHn
(1973) is based on a triangular load
distribution and a load increase factor (k
deb
). (Fig. 5)
The second approach is based on mechanical
models and rheologic properties of the displacement
process. The impact on the structure is shown a con-
stant load distribution (rectangular load distribution).
Alternative load models (distribution) are shown in
H
übl
& H
olzinGeR
(2003) and s
uda
et alii (2009).
The relevant actions, their quantification and load
models will be arranged in the ONR 24801.
The peak impact load p
deb
[kN/m²] can be defined
by Eq. (3). This formulation according to H
übl
&
H
olzinGeR
(2003) bases on laboratory experiments
compared with field data. This empirical formulation
bases on the peak impact load (p
deb
) [kN/m²] the ve-
locity of the debris flow front (v) [m/s] and the runoff
height (hfl) [m]. This model has a scope for FROUDE-
values from 1 to 15.
P
deb
= 4,5 · p
deb
· v
0,8
· (g · h
fl
)
0,6
· 10
-3
Eq. (3)
For the determination of magnitude (intensity) of
debris flows in recent years some physical (e.g. FLO-
2D, RAMMS) or empirical models (e.g. TopRun)
have been developed, which yield the run-out distance
or deposition area (R
iCkenmann
& s
CHeidl
, 2010).
LOADS ON BARRIER STRUCTURES
Stresses on torrential barriers result from water
(hydrostatic, dynamic), earth and debris flow impact.
In special cases effects from avalanches, falling rocks
and earth-quakes must also be considered. The rel-
evant actions on torrential barriers result from the pre-
dominant displacement process in the torrents.
The impacts on torrent control works according
to ÖNORM EN 1990 are categorized in permanent,
variable and accidental actions
. According to ONR
24802:2010 accidental impacts are either caused by
extreme events exceeding the design event or corre-
lated to processes that are not covered by the system-
causal relationship and corresponds to a specific prob-
ability of recurrence and intensity. The design event
for the dimensioning of torrent control works is usu-
ally determined according to a defined return period
(e.g. flood with return period of 100 years). Due to the
transient behaviour of hyper concentrated flows (de-
bris flood, debris flow) a prediction of discharge based
on hydraulic statistics is practically impossible. Con-
sequently flood events of status II and III can be cor-
related to a certain return period only with restrictions.
For the estimation of peak discharge at debris
flow regime empirical formulas (m
izuyama
et alii,
1992; R
iCkenmann
, 1995) based on a simple correla-
tion to bedload (solid transport) can be applied. Ac-
cording to R
iCkenmann
(2001) the peak discharge (Q)
[m³/sec] of a debris flow can be estimated for granu-
lar debris flows with Eqn. (1) and for muddy debris
flows with Eq. (2):
Q = 0,135 · D
0.78
Eq. (1)
Q = 0,0188 · D
0.79
Eq. (2)
According to ORN 24802:2010 a rough estima-
tion of the design discharge for debris floods can be
done by multiplying the flood discharge with an event
coefficient
(EC). The dimensionless EC is determined
with respect to the relevant process according to Tab.
1. The EC takes into account that in the course of hy-
perconcentrated displacement processes large masses
of debris are transported within a short time. The
application of this simple model presupposes an as-
sessment of the relevant displacement process in the
respective torrent reach.
The characteristic and intensity of the debris dis-
placement has decisive influence on the shape of the
flood hydrograph. Excessive displacement processes
tend to generate hydrographs with extreme peak dis-
charge but very short transit time, debris flows are char-
acterized by multiple consecutive, steep and short “hy-
drographs” (comparable to roll waves). (H
übl
, 2010).
There are two traditional simplified models to cal-
Tab. 1 - Process-related event coefficient (EC) for the
rough estimation of design flood based on the
water discharge
Fig. 5 - Simplified model for debris flow impact on tor-
rential barriers (triangular load distribution
and resulting force)
background image
f. RUDOLF-MIkLAU & J. SUDA
1088
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
atical function of the structure (e.g. earthquakes).
The proof of the hydraulic capacity of a torrent
control work based on the design discharge comprises
the following verifications:
• proof of the capacity of the discharge section
(hydraulic capacity has to exceed the design flood
taking into account a freeboard);
• proof of the capacity of large openings (slits);
• dimensioning of spilling pool (overflow).
ONR 24802:2010 defines the limit states for the
proof the stability and serviceability of the torrent con-
trol works and bearing structures. In order to provide
these proofs the following impacts have to be taken
into account for the design of torrent control works:
• own weight of structure;
• soil pressure;
• water pressure (design water level, water pressure
in tension cracks);
• ground water pressure (water pressure at basis);
• dynamic water pressure of design event (flood,
debris flow);
• dynamic water pressure exceeding the design event
• water pressure due to unplanned backwater;
• traffic loads.
In specific cases additional impacts by slope fail-
ure, rock and snow avalanches, earth quakes or ex-
treme floods have to be taken into account.
RELEVANT STRESS COMBINATIONS
According to ONR 24802:2010 the relevant im-
pacts for the dimensioning of torrent control structures
have to be combined according to the predominant
displacement process (status I or II). These character-
istic combinations of loads are qualified as standard-
ized stress combinations (SC).
In SC A (Fig. 5), the state before backfill, the hy-
drostatic water pressure from the backwater (w
owS
) is
acting on the barrier. The specific gravity of the water,
depending on the content of bed load in the pure wa-
ter, ranging from g
W
= 10 to 20 kN/m³.
If there is a water flow behind the bottom side of
the barriers foundation a reduced hydrostatic water
pressure in the soil body can be used. In this stress
combination the buoyancy force (w
A
) is acting on the
barriers bottom side. This force reduces the external
stability of the barrier. The downstream water pressure
(w
uw
) must not be used as a resistance for the barrier.
The highest load on this kind of construction,
however, occurs when it is hit by a debris flow. If there
is a possibility for such an event stress combinations
SC G to L have to be used:
• SC G (Fig. 6) and H - debris flow action on barrier
at unfilled storage basin, with/without percolating
flow and buoyancy force;
• SC I and J - debris flow action on barrier at partly
filled storage basin, with/without percolating flow
and buoyancy force;
• SC K and L - debris flow action on barrier at to-
tally filled storage basin, with/without percolating
flow and buoyancy force.
Details on the calculation of the specific loads and
their load distribution are given in b
eRGmeisteR
et alii
(2009), detailed standards will be included in ONR
24801:2011.
IMPACT OF EXTREME EVENTS (STATUS III)
Excessive torrential events (status III) as a rule
exceed the design criteria for torrent control works.
The impact by these extreme events can result in the
structural or functional failure of dams although only
few cases of dam break are documented in the history
of torrent control engineering. Excessive torrential
Fig. 6 - Stress combinations for retention, dosing and fil-
tering barriers; according to ONR 24802
Fig. 7 - Tress combinations for energy dissipation barriers
(debris flow breaker); according to ONR 24802
background image
TECHNICAL STANDARDS FOR DEBRIS FLOW BARRIERS AND BREAKERS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1089
ve deformation of the ground (sliding at the base,
toppling, bearing resistance failure of the soil be-
low the base, loss of overall stability);
• UPL: uplift limit state;
• HYD: heave limit state.
Internal stability:
• STR: structural failure, failure or excessive de-
formation of the structure or one of its elements
(bending, shear and stability failure).
For assessments, torrential dams are mostly
treated like retaining structures. For ULS - design
the semi probabilistic assessment concept is used.
The models for assessment and the values of the
partial safety factors for actions and resistances for
GEO, UPL, EQU and HYD limit states are equal to
ÖNORM B 1997-1-1. For reinforced concrete units
assessment in the STR limit states the partial safety
factors for actions are given in Tab. 2.
The values of the partial safety factors for the
building material resistances (e. g. concrete, steel, tim-
ber) depend on the material characteristics, the regard-
ed limit state and the design situation (DS). The partial
safety factors for structures material resistances are
given in EN 1992-1-1 and ÖNORM B 1992-1-1, EN
1993-1-1 and ÖNORM B 1993-1-1 and EN 1995-1-1
and ÖNORM B 1995-1-1.
SERVICEABILITY LIMIT STATE DESIGN (SLS)
For SLS - design the following analyses are
necessary:
• process serviceability design, according to the
functional type;
• limitation of settlements ÖNORM B 1997-1-1;
• limitation of crack widths ÖNORM EN 1992-1-1,
chapter 7.3 for reinforced concrete barriers
The limit values for crack widths w
max
in rein-
forced concrete structures, in dependence of the ex-
position classes which are defined in the ÖNORM B
1992-1-1, Tab. 4, are to be kept. In hydraulic engineer-
ing, the crack widths have to be limited to 0.25 mm for
events have to be taken into account with respect to
dam safety and the residual risk.
For large dams European standards require that an
extreme flood event of a return period of 5.000 (10.000)
years can securely overflow the structure. In Austria
this regulation applies for dams with a height exceed-
ing 15 meters or reservoirs with more than 500.000 m³
(BMLFUW, 2009). Torrent dams have to be dimen-
sioned according to these standards if a longer lasting
tailback of water has to be taken into account. (ONR
24802:2010) The hydraulic effects and consequences
of a dam break can be estimated (calculated) by flash
flood models. The failure of reservoirs upstream of
steep torrential watercourses may trigger debris flows,
which consequently have to be taken into account in a
safety concept for flood retention basins.
For “classical” debris flow dams a longer lasting
tailback of water is improbable due to the permeable
construction and the large openings (slots, slits). The
appropriate design for extreme floods is reached by
constructive measures such as oversized or double-
profiled discharge cross sections.
DESIGN OF DEBRIS BARRIERS (BREAKERS)
For the design of debris barriers (breakers) the
Ultimate Limit States (ULS) and the Serviceability
Limit States (SLS) must be considered. The rules for
assessment and design are related to the EUROCODE
- standards. The ONR 24802 is based on this concept
and gives specific design rules for torrential barriers.
ULTIMATE LIMIT STATE DESIGN
The failure types of torrential barriers are related to
those of retaining structures. On torrential barriers an ex-
ternal and internal failure can appear (s
uda
et alii, 2010).
The following Ultimate Limit States must be considered:
External stability:
• EQU: equilibrium limit state;
• GEO: geotechnical limit state, failure or excessi-
Tab. 2 - Partial safety factors for actions and STR/GEO
assessment, according to ONR 24802
Tab. 3 - Recommended maximum crack width (wmax) for
torrential barriers, according to ONR 24802
background image
f. RUDOLF-MIkLAU & J. SUDA
1090
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
waterproof reinforced concrete construction works.
The maximally permissible crack widths for torrential
barriers are given in Tab. 3.
For durability and serviceability reasons a mini-
mum reinforcement (A
s
min
) near to the surface for all
concrete members (Tab. 4) is requested. This mini-
mum reinforcement is given as fraction of the con-
crete cross section (Ac).
DISCUSSION AND CONCLUDING REMARKS
The technical standards of the ONR 24800-se-
ries constitute a new dimension in torrent control en-
gineering. The application of these regulations will
favour the efficiency and cost-effectiveness of pro-
tection structures and secure a high standard of qual-
ity concerning the functionality, stability and safety
of barrier structures. After the completion of the new
Austrian standards a phase of testing and evaluation
will help to gather experiences with the practical ap-
plication of theses regulations. In addition a process
of international implementation of these standards
was started with Bavaria and Slovenia participation
in the development process.
ACKNOWLEDGEMENTS
The authors thank the Federal Ministry of Agri-
culture, Forestry, Environment and Water Manage-
ment, the Austrian Service for Torrent and Avalanche
Control and the Austrian Standards Institute for the
support of this research and development process.
Tab. 4 - Recommended minimum reinforcement for torren-
tial barriers, according to ONR 24802
REFERENCES
a
ulitzky
H. (1980) - Preliminary Two-fold Classification for torrent cones, Proceedings of Interpraevent Conference, 4: 243-256.
b
eRGmeisteR
k., s
uda
J., H
übl
J. & R
udolf
-m
iklau
f. (2009) - Schutzbauwerke gegen wildbachgefahren. Ernst und Sohn, Berlin.
BMLFUW (2009) - Leitfaden zur Hochwassersicherheit von Stauanlagen. Bundesministerium für Land- und Forstwirtschaft,
Umwelt und wasserwirtschaft; Technische Universität Wien, Institut für Wasserbau und Ingenieurhydrologie (in German).
H
übl
J. (2006) - Vorläufige Erkenntnisse aus 1:1 Murenversuchen: Prozessverständnis und Belastungsannahmen. In: FFIG,
G. R
eiseR
(Hrsg.), Geotechnik und Naturgefahren: Balanceakt zwischen kostendruck und Notwendigkeit. Institut für
Geotechnik, BOKU Wien, Geotechnik und Naturgefahren, 19.10.2006, Wien (in German).
H
übl
J. (2010) - Hochwässer in wildbacheinzugsgebieten. Wiener Mitteilungen (in print).
H
übl
J. & H
olzinGeR
G. (2003) - Entwicklung von Grundlagen zur Dimensionierung kronenoffener Bauwerke für die
Geschiebebewirtschaftung in wildbächen: kleinmaßstäbliche Modellversuche zur wirkung von Murbrechern, WLS Report 50
Band 3. Im Auftrag des BMLFUW VC 7a (unveröffentlicht). Wien: Institut für Alpine Naturgefahren, Universität für Bodenkultur
i
veRson
R.M. (1997) - The physics of debris flows. Reviews of Geophysics 35, American Geophysical Union: 245-296.
J
enni
m. & R
eiteReR
a. (2002) - Debris flow management with crash dam construction. Journal of Torrent, Avalanche, Landslide
and Rock Fall Engineering, 148: 11-19.
J
oHnson
a.m. (1970) - Physical processes in geology. San Franzisco: Freeman and Cooper.
k
ettl
W. (1984) - Vom Verbauungsziel zur Bautypenentwicklung. Wildbachverbauung im Umbruch. Wildbach- und
Lawinenverbau, 48: 61-98.
l
iCHtenHaHn
C. (1973) - Die Berechnung von Sperren in Beton und Eisenbeton. In: Kolloquium über Wildbachsperren,
Mitteilungen der forstlichen Bundesversuchsanstalt Wien, Heft, 102 S.91-127
m
aRCo
F. (2007) - Torrential Processes. In: C
amPus
s, f
oRlati
f., b
aRbeRo
s. & b
ovo
s. (eds.): Evaluation and Prevention of
Natural Risks. Taylor and Francis/Balkema: 169-199.
m
azzoRana
b., f
uCHs
s. & H
übl
J. (2009) - Improving risk assessment by defining consistent and reliable system scenarios. Nat.
Hazards Earth Syst. Sci., 9: 145-159.
m
izuyama
t., k
obasHi
s. & o
u
G. (1992) - Prediction of debris flow peak discharge. Proc. Int. Symp. Interpraevent, Bern,
Switzerland, 4: 99-108.
P
Roske
d., k
aitna
R., s
uda
J. & H
übl
J. (2008) - Abschätzung einer Anprallkraft für murenexponierte Massivbauwerke. Beton
und Stahlbetonbau, 12: 803-811.
background image
TECHNICAL STANDARDS FOR DEBRIS FLOW BARRIERS AND BREAKERS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1091
R
iCkenmann
D. (1995) - Beurteilung von Murgängen. Schweizer Ingenieur und Architekt, 48: 1104- 1108 (in German).
R
iCkenmann
D. (2001) - Estimation of debris-flow impact an flexible wire rope barriers. Swiss Federal Research Institute WSL.
R
iCkenmann
D. (2003) - Methode zur Beurteilung von Murgängen; ETALP - MURGÄNGE V2.2; Universität für Bodenkultur Wien.
R
iCkenmann
d. & s
CHeidl
C. (2010) - Modelle zur Abschätzung des Ablagerungsverhaltens von Murgängen. Wasser Energie
Luft, 102: 17-26 (in German).
R
udolf
-m
iklau
f. (2009) - Naturgefahren-Management in Österreich, Nexis Lexis Orac, Wien.
s
CHRott
l. & G
lade
t. (2008) - Frequenz und Magnitude natürlicher Prozesse. In: f
leGentReff
& G
lade
t. (eds.): Naturrisiken
und Sozialkatastrophen. Spektrum Akademischer Verlag Springer: 134-150 (in German).
s
uda
J., H
übl
J. & b
eRGmeisteR
k. (2010) - Design and Construction of high stressed Concrete Structures as Protection works
for Torrent Control in the Austrian Alps. In: Proc. of the 3
rd
fib international Congress, Washington, USA.
s
uda
J. & R
udolf
-m
iklau
f. (2010) - Standards for design and maintenance of torrential barriers. 8
th
ICOLD European Club
Symbosium, Innsbruck, Austria (in press).
s
uda
J., s
tRauss
a., R
udolf
-m
iklau
f. & H
übl
J. (2009) - Safety Assessment of Barrier Structures. Structure & infrastructure
engineering, 5: 311-324.
Statistics