avalanche protection

DI Siegfried Sauermoser Trabzon 2012

Siegfried Sauermoser

County Director Tirol

Austrian Service for Torrent and

Avalanche Control

Liebeneggstrasse 11

6020 INNSBRUCK

Avalanche protection

0512-584200-20

0664-5327507

[email protected]

[email protected]

mailto:[email protected]





Federal Ministry of Agriculture, Forestry, Environment and Water

Management (Departement IV)

Forest law 1975: § 102… Protection against Natural Hazards

• Planning and implementation of protection measures,

• Technical and forest biological measures, mainainance etc..

• Hazard mapping

• Expert opinions for the authorities

• Torrent and avalanche cadaster

www.lebensministerium.at

www.naturgefahren.at

Austrian Service in Avalanche and Torrent

Control

http://www.lebensministerium.at/

http://www.naturgefahren.at/

Regional organisation structure of the

Austrian Service of Torrent and Avalanche Control

Section

Tyrol

Section

Vorarlberg

Section

Carinthia

Section

Salzburg

Section

Upper Austria

Section

Vienna,

Lower Austria and

Burgenland

Administrative departments:

Villach

Lienz

ImstBludenz

ReutteWörgl

Schwaz

Zell a. See

Tamsweg

Seewalchen

Bad Ischl

Scheifling

Admont

Stainach

Bruck a. Mur

Melk

Wr.

Neustadt

Kirchdorf

Section

Styria

Wien

Linz

Salzburg

Graz

Innsbruck

Bregenz

7 headquarters

28 regional offices

3 technological staff offices

297 employees &

800 construction workers



AUSTRIA

Avalanche path´s


Avalanche 24.2.1999


6500 Avalanche paths


12 000 torrents



Avalanche history

Strabon (63 v. Chr. – 26 n. Chr.)

Livius ( 59 v. Chr. - 17 n. Chr.)

Isidoris (560 – 636 n. Chr.) Erzbischof of Sevilla

Lavina (labi)

10Jh. Briccius, Heiligenblut

14 Jh. Heinrich von Kempten, Hospitz Arlberg (1385)

16 Jh. Kaiser Maximilian

1689 One of the strongest avalanche winters

1916 Several thousand avalanche victims during the WW 1

1951 135 avalanche victims in Austria (picture Häselgehr)

1954 146 avalanche victims in Vorarlberg

1999 38 avalanche victims in Austria, 69 in the whole alps


Avalanche history

Old farmhouse

protected

against avalaches

by a rock and

avalanche design of

the house;


DI Siegfried Sauermoser Lawinenschutz 15

Concrete breaking wedges,

Arzleralm Lawine,

Innsbruck 1965

Historical permanent measures

First Avalanche shed along the

Reschenbundesstrasse 1854


16

Avalanche rake;

first protection measures in the starting zones

of avalanches along the Arlberg railway;


Stone terraces in the starting zones of

avalanches;

Paznaun - valley 1950 - 1960


Heuberg Häselgehr 1960 – 1970Technical avalanche protection in the avalanche starting zones started in the fifties after

the Avalanche disasters 1951 und 1954; The first guidelines in Swiss were issued in

1955



5 Avalanche protection(McClung/Schärer 2006: Avalanche Handbook)

Intervention

Active Passiv

Du

rati

on

Per

man

ent

Tem

po

rary avalanche control by

explosives

road closures

precautionary evacuation

avalanche forecasting/warning

seasonal occupation

(summer houses)

seasonal road closures

organizational measures

warning signs

supporting structures

snow fences

deviation, retarding and catching

dams

retarding earth mounds

splitting wedges

reinforced construction

snow sheds

reforestation/forest protection

hazard mapping and

land use planning

Integral Avalanche

Protection


Starting area

(30° – 55°)

Avalanche track

confined or unconfined

runout area, deposition

area

(< ca. 10°)

3. Avalanche dynamics

3.2 Avalanche terrain


Most of the big catastrophic avalanches are mixed avalanches;

They consist of a dense flow parta fluidised layer and a suspensionlayer;It depends on the temperature, thevelocity and the longitudinal sectionof the track how much of the snowis transferred to the suspension layer;

Normally the suspension and thefluidised layer are faster than thedense flow and sometimes they takedifferent ways

Mixed snow avalanches:

ONR 24806: Design of Avalanche constructions

Graphik aus SATSIE 2009; mod. Sauermoser


Mixed Snow avalanche

Examples for destruction:

1 kPa broken windows

5 kPa broken doors

30 kPa brig houses and wooden houses

are damaged or destroyed

3 kPa evergreen trees are broken

Avalanche forces:


Wood provides avalanche protection

only if it is situated in the starting

area;

Trees are not able to withstand the

avalanche forces in the avalanche

track;

Avalanche tracks are to recognise by

Larches or leaf trees, they have high

resistance against avalanche

pressure;

The age of the trees gives some

information about the frequency of

avalanches;

Avalanches and protection wood


Defense structures in avalanche starting zones;

Madlein Lawine, Gde Ischgl, Tyrol

Combination of steel and wooden

supporting structures below the

potential and actual

timberline;

(afforestable)

Gramaiser Heuberglawine;

Tyrol, Austria



Steel supporting structures in

combination with afforestation;

It is assumed that only 20 –

30% of all avalanche areas are

situated below the timberline;

Haggener Sonnberg,

Sellrain

Tyrol, Austria



Different statical systems to support the snow packHandbuch – Technischer Lawinenschutz; Rudolf-Miklau, Sauermoser (Hsg)

Verlag Ernst & Söhne,

The first generation of structures have been erected with concret foundations, this was very

expensive because of the heavy loads and sometimes the lack of water in high altitudes.



IPE 220

80°

Sp 640

Bz 220, Sp 8 x 90

10°

110,5

b 460

c 1.100

40°

I o 3.290

60°

42 – 160 knpressure: 42 –160 kN

tension: 70 – 260 kN

direction is variable

axial directionpressure:110-270

kN

Forces and direction

of forces:

S´Q


IPE 220

HE

120 A

80°

Sp 640

Bz 220, Sp 8 x 90

10°

110,5

b 460

c 1.100

40°

I o 3.290

60°

IPE 220H

E 1

20 A

80°

Sp 640

Bz 220, Sp 8 x 90

10°

110,5

b 460

c 1.100

40°

I o 3.290

60°

Mikropiles for

anchoring the support



Technical avalanche protection

anchoring of steel bridges with

hydraulic or pneumatic drill

equipment;

diameter: d = 90 – 110 mm;

anchor: GEWI 30 – 42 mm

coating with > 30 mm anchor

grout;

The anchor must be centered in

the borehole;

geotextil stockings are used in

loose material

special construction in loose

material (tube);

output: 5 – 6 Werke/Tag

costs: 500 – 1000€ / Anker



Foundation of snow bridges with

small excavator;

output 6 – 8 constructions / day

restriction:

legth of anchors < 6 m

costs similar as by hand drilling

no wooden support construction is

Necessary

A comparison has been made by

WALTER G. see. Lit.


Prefabricated foundation for supports

Groundplates 40 x 40 cm in rock

60 x 60 cm in loose soil

80 x 80 cm in very loose soil

The zinc-coated plate is stabilized with

a small anchor to withstand the shear forces;

It is very important to place the groundplate

in natural ground

The hole should be refilled with the excavated

material;

Corrosion protection of the support is not

necessary


Refilled

ecavated

material Ground

plate

Surface

zone

kNUFc

,.2

UN,k

UT,k

2

tan.,

,

EkkN

kT

UU

UN,k = characteristic value of the axial support force

normal to the foundation area Fc. σα specific total

ground resistance in a direction normal to Fc

(σα90° -= 500-1000 kN/m²)

UT,k Characteristic value of the transverse force

at the base of the support parallel to the foundation

area Fc

ϕEk Characteristic angle of friction for transfer of

compressive forces

(assumed constant; tanϕEk = 0.8)

Fc

ONR 24806:

Design of Avalanache protection work


Federal Office of Environment FOEN;

WSL Swiss Federal Institute for Snow and Avalanche Research SLF; 2006



Damages


Project Snow nets, Innsbruck

Flexible support construction:

Snow nets

Material:

Galvanised steel ropes,

swivel posts

rope anchors


Snow nets


Snow nets

Triangular nets

Rectangular nets

Mesh width on the support surface:

without wire mesh ≤ 100 mm,

with wire mesh (≤ 50 mm) 200 to 250 mm is allowed

for the cables

fs = reduction factor for a flexible supporting surface (0,8)

The specific loading of load case 2 must be assumed

over the entire height of the nets

The loading of a snow net depends significantly on the sag.

The sag must correspond to the value specified by the

designer of approx. 15 % of the chord of the net.

The snow presssure component normal th the slope and the

lateral load are neglected


Snow nets


Project Snow nets, Innsbruck

How is the real load under

different condition ?

Behavior of differt types of

nets


Creeping and gliding forces are

existing also between the rows of

steel bridges and additional technical

measures are necessary.

To prevent the plants against snow

mechanical forces we use:

Wooden threepole constructions

array of posts

small terraces

Combination supporting structures – gliding snow measures

afforestetion


afforestetion


afforestetion

Köglenlawine, Gde Elbigenalp;


afforestation


Acitv permanent protectiv measures in the starting area;

Supporting structures


Acitv permanent protectiv measures in the starting area;

Snow creeping and gliding

Piling

Earth teraces

Measures to influence the snow distribution in the

starting area

Often used in combination with supporting structures

Snowdrift fences:

Construction height is 4 – 6 m

L = 5 . H/f (m)

L = deposition area

H = construction height

F = rate of filling (0,5 – 0,7)

There is no significant difference between horizontal or

vertical beams; (wooden beams, steel beams)

Crucial is the location of the fence (perpendicular to the

main wind direction

Snowdrift measures

(Lawinenhandbuch S 109/110)

Snowdrift measures


Windbuffles are situated close to

mountain ridges to influence the

snow distribution;

The building of cornices is interrupted

The density of the snowpack is

different;

Snowdrift measures


Wind nozzles (wind roofs) are situated

in the beginning of the lee-slope;

The wind velocity should be enlarged

and the snow drift leads to interruption

of cornices and the distribution of

snow over the complete slope;

Snowdrift measures



Technical avalanche protection

Organisation of avalanche building sites in the

starting area :

Accessibility

road, cable cran, helicopter

Equipment:

Drilling equipment

Injection pump

Anchor grout

Energie supply

Water supply

CompressorSafety:

Lightning, falls, rockfall, safty equipment,

Container

Deflecting avalanches:

Deflecting dam, deflecting walls

max. deflecting angel =approx. 20°

Height of deflecting dams:

Htot = Hs + Ha + He

Hs = Height of the snow cover (m)

Ha = Flowing height of the avalanche (m)

He = Energy height = v²/2g . sin² (m)

Shape of the dams:

Avalanche side as steep as possible

(stone walls, reinforced earth)

defelecting angleα<20°

Measures in the avalanche track and the

runout area –deflecting, retarding, stopping


Deflecting wall

Hanggerbachlawine






Reinforced earth is beside placed rockfill a proper method to stabilize steep slopes




Mass balance:

Equal masses in excavation and filling leads to

little mass movement and therefore to less

costs; The effect of the dam can be improved

by the excavation of the forefield of the dam;

Further effects are the improvement of

agricultural land, this is important for the

acceptance of dams;

Avalanche deflecting dam Flateyri; Island;



Stopping – retarding dams,

retarding mounds:

Minimum height for catching dams:

Dense flow part:

Htot = Hs + Ha + He

Hs = Height of the snow cover (m)

Ha = Flowing height of the dense flow (m)

He = Energy height= v²/2g . λ (m)

λ = 1 – 2 (Energy loss factor)

Powder part: (recommendation by Issler)

until 100 m downstream of the dam reduced

energy:

Factor 2 uphill dam inclination <= 45°Factor 3 uphill dam inclination > 45°

provided that the total dam height is at least the

half of the flowing height of the avalanche;

2/3 4/5

to stop and deposit the avalanche completely :

dam height

storage capacity




stockibach avalanche

st.anton tyrol

Avalanche catching

dam with opening

for the brook;






Avalanche catching dam

at the Innsbrucker Nordkette;

(Rastlbodenlawine)

An avalanche was deflected

by the dam and the

adjacent wood was destroyed




Avalanche Catching dam in Neskaupstadur, Island

DI Siegfried Sauermoser Technical avalanche protection 74




Diasbachlawine, Paznaun

Tyrol, Austria






Diasbachlawine, Paznaun

Tyrol, Austria





Hakonardottir M., Johanneson T., Tiefenbacher F., Kern M. (2003): A loboratory

study of retarding effect of braking mounds in 3,6 and 9 m long chutes;

Vedurstofa Islands, Report 03024

Velocity reduction is about

20% by the first row

and 10 % by the second row;

Height of the mounds is

2 – 3 times the flowing height;

Ratio H/B = 1

Inclination upstream face = 60°





Breaking mounds

Neskaupstadur, Island



Unresolved issues

Several issues need to be investigated further in order to improve avalanche dam

design criteria

beyond the guidelines proposed here.

•Loss of momentum during the impact with the dam:

• Effect of terrain slope towards the dam on the shock height:

•Effect of entrainment and deposition:

•Effect of the saltation and powder parts:

•The maximum deflecting angle (ϕmax)

The design of avalanche protection dams

Recent practical and theoretical developments

Edited by T. Jóhannesson1, P. Gauer2, P. Issler 2 and K. Lied (EC

2009)

DI Siegfried Sauermoser Trabzon 2012 80





Single protection of hauses


Protection of single houses

Quelle: Richtlinie Objektschutz gegen Naturgefahren, Gebäude

Versicherungsanstalt des Kantons St. Gallen

Protection of single buildings


bodenbach-avalanche

kaunertal tyrol

Direct protection

by a stone masonry wall

(conctrete masrony) 16,0 m

Protection of single buildings


Avalanche shed

Artificial avalanche release

12 cm mortars can be used from a range of 1 to 4 km.

A two-chambered pneumatic

(compressed gas)

cannon used in avalanche

control work.

It is probably the most popular

civilian weapn in use.

The trajectory is varied by altering

the firing angle

and the nitrogen pressure.

It's disadvantages include

a short range and poor

accuracy in strong winds.


Avalancheur Lacroix

Construction and function

The cannon is permanently installed

in centrally accessible and safe place

The 1.8 m long arrow-type projectile

is loaded with 2.2 kg of liquid explosive

Nitrogen is used as a pressure medium

The targets are test-fired at the time of

commissioning.

The alignment of the cannon and adjusting

the necessary gas pressure

ensure that the desired

zones can be unerringly fired even

without vision

The arrow projectile is impelled into

the starting

zone and detonated on impact.


Installation

The Avalanche Guard systems are installed in a safe

location near the avalanche starting zone by means

of foundations or rock anchors. They consist of one

or two protective cabinets holding 10-explosive

charges each. The operating personnel use a flip-up,

lockable platform to insert the charges before

the winter or during favorable periods.

Remote controlled

Launching is released from a safe location by means

of a PC. The commands from the operating

point to the Avalanche Guard are transmitted

by secure radio control. A solar unit supplies the

energy required for the electrical control in the

protective cabinet with safety system, ignition

generator, and automatic door activation.

Launching ranges of 160 to 500 ft (= 50 to 150 m)

are reached thanks to different propellant charges,

so that one Avalanche Guard covers an

avalanche starting zone of 1000 ft (= 300 m).


The Avalanche Pipe, a single-shot launching device,

is the avalanche patroller’s extended arm.

The explosive cartridge holding 6 lbs. (approx. 2.8 kg)

of avalanche blasting explosive can be

launched over a range of maximum 650 ft (=200 m).

The Avalanche Pipe can be rotated by 360° at

three different inclinations. The propelling charge

is ignited by an ignition generator. This launching

device is installed on a foundation or for mobile

operation on a snowcat.

The target points for the permanently installed

single-shot launching devices are firmly established

in test firing. Direction, gradient and size of propellant

charge are determined for each location, so that

blasting at short intervals is also possible from a safe

spot also in poor weather conditions.


The Avalanche Master is installed

with 25° inclination immediately above

the avalanche starting zone. It is accessible

and features all necessary working elements

and assistance for climbing. The main part

consists of platform, launching cabinet,

and control box. The launching cabinet holds

10 explosive charges with propelling charge and 6 lbs.

(approx. 2.8 kg) of avalanche blasting

explosive each. Next to each explosive charge

is the bobbin with the holding rope attached to

the charge. Suspending the charge from the

rope ensures that the target point

below the tower is hit reliably. A second target

point located further away is reached by launching

an unattached explosive charge. The system's

application range is extended decisively in this way.


Temporary measures


(Lawinenhandbuch S 121 – 134)

Temporary measures


(McClung, Schärer, Avalanche Handbook 2006)

Daisy bell

O´bell

T.A.S

blasting

ropeway



Planning of protection work

Making a decision:

1) Define objectives and acceptable risk (hazard map, risk map)

2) Define, evaluate and select optimal protection alternatives,

including costs, benefit and environmental consideration

3) Create a detailed design for the selected alternative

Preliminary risk

Residual risk (hazard)

Cost/benefit

Intangible factors

Politics

Psychology

Environmental and other hazard considerations

Something has changed……

Settelement development

Mobilty

Acceptance of Natural Hazards

Settlement development

In the Paznaun valley from

1950 - 2010


Forest law 1975§ 11; Hazard zones

Hazard zones (Red and Yellow hazard zone)

Avalanches

Debris flows

Areas with rockfall and landslide danger (brown)

Areas that should be reserved for future protective

measures or woods which needs a special treatment to

maintain their protectiv function (blue)

Areas with special morphological function as natural

earthdams above settlements (violett)DI Siegfried Sauermoser Trabzon 2012

Avalanche hazard zones

Problems caused by the change of criterias


Avalanche hazard mapping

applied methods

• Chronicles, interviews (historical method)

• Interpretation of hazard indicators

• collection of datas – geomorphological, geological and

meteorological

• terrain analysis by field work and stereoscopical interpretation

of airealphotos

• calculation, modelling


Hazard

indicators



applied models

Topographical statistical model:

80 extrem avalanche runout distances were analysed

(Lied/Weiler/Hopf/Bakkehoi (1996))

α = 0,946 β - 0,83

AVAL-1D: one dimensional numercal Voellmy based model (dense flow)

ELBA: two dimensional numerical Voellmy based model (dense flow)

SAMOS: numerical cupled dens flow – powder flow model

dense flow calculation is based on the granular flow theorie

of HUTTER/SAVAGE;

powder flow is based on a gasdynamical approach

RAMMS: 2D VOELLMY


Topographical statistical model:

80 extrem avalanche runout distances were analysed

(Lied/Weiler/Hopf/Bakkehoi (1996))

α = 0,946 β - 0,83



applied models

AVAL-1D, Fließlawine Profil 1,

Vergleich Anbruchhöhe Hagen und do 150

Diff = 40 m

SLF: Anfangsbedingungen für Fliesslawinen:

do = do* . F (Neigungsfaktor)

do* = 1.91 + 35 cm (Höhe) + 50 cm Wind = 276 . 0.46 (50°)= 130 cm

do* = 1.91 + 30 cm + 50 cm . 0.81 (32°)= 220 cm

Masse Profil1 = 50 000 t

Masse Profil 1(Hagen) 71 000 t



application of models



Austrian regulation



Avalanche Hazard Zoning in Icland

Avalanche Hazard Zoning in

Icland



Avalanche Hazard Zoning in Norway

Avalanche Hazard Zoning in

Norway - legal regulation

Security class Maximum nominal avalanche

annual probability

Avalanche return period

(years)

Type of construction

1 10-2 100 Garages, smaller storage roms

of one floor, boat houses

2 10-3 1000 Dwelling houses up to two

floors, operational buildings in

agriculture

3 10-3 1000 Hospital, schools, public halls

etc.



Swiss regulation



Experiences

- Hazard maps help to provide objectivity by the distribution of public money (cost – benefit)

- it is a worthfull instrument to direct new settlements in save areas

- The acceptance by the authorities is very high (approx. ¾ of the communities have a hazard map)

- but Hazard mapping has not yet brought a decline of activ protection work



Austrian Standards in Technical Avalanche protection


Technical protection measures – avalanches



Technical protection measures – avalanches

Thank you for your attention


avalanche protection

Documents