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Urban Habitat Constructions under Catastrophic Events FINAL CONFERENCE. Naples, 16 th - 18 th September 2010 Final report Topic 1.5: Actions due to volcanic eruptions J-P. Muzeau & A. Talon LaMI Blaise Pascal Univ. Clermont-Fd,

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Urban Habitat Constructions under Catastrophic Events

FINAL CONFERENCE. Naples, 16th - 18th September 2010

J-P. Muzeau & A. Talon – LaMI – Blaise Pascal Univ. – Clermont-Fd, FR J-C. Thouret – Magmas & Volcans Lab., B. Pascal Univ. – Clermont-Fd, FR

  • T. Rossetto – Dep. Civil, Environ. & Geomatic Engin, Univ. Col. London, U.K.
  • B. Faggiano & D. De Gregorio – Dep. Struct. Engng, ‘Federico II’ Univ.,

Naples, IT

  • G. Zuccaro – PLINIVS Centre. ‘Federico II’ Univ., Naples, IT
  • M. Indirli – ENEA, Bologna, IT

Final report – Topic 1.5: Actions due to volcanic eruptions

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General Report – Topic 1.5: Actions due to volcanic eruptions

Jean-Pierre Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Introduction

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General Report – Topic 1.5: Actions due to volcanic eruptions

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Introduction

 Today, about 1/2 billion people live at risk from

volcanic hazards: Naples (Vesuvius), Tokyo (Fuji), Mexico City (Popocatepetl), Auckland (Auckland field), Arequipa (El Misti)…

Naples, Vesuvius, Italy

 As the amount of

people populating the area surrounding the active volcanoes increases, the risk also increases.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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Introduction

 Objectives of the COST Action C26: – to provide a methodology to evaluate the

volcanic vulnerability of urban environments towards an eruption.

Arequipa, El Misti, Peru

– to propose simple

and economical mitigation interventions.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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Content of the presentation (Part 1.5)

  • 1. Volcanic hazards
  • 2. Why to study volcanic hazards?
  • 3. Effusive eruption
  • 4. Explosive eruption
  • 5. Secondary events
  • 6. Impacts of ash fall
  • 7. Impacts of pyroclastic flows
  • 8. Mitigation strategy
  • 9. Vulnerability, risk and damage assessment
  • 10. Structural aspects
  • 11. Research activity and/or guidelines
  • 12. Further developments
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  • 1. Volcanic hazards

 Direct hazards:

Fall process

– Tephra falls – Ballistic projectiles

Lava flow Pyroclastic flow Debris flow

– Lahars

Sector collapse

and flank failure

– Debris avalanche

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  • 1. Volcanic hazards
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  • 1. Volcanic hazards

 Indirect hazards:

Earthquakes and ground deformation Tsunami Secondary debris flows Post-eruption erosion and sedimentation Atmospheric effects Air shocks, lightning Post-eruption famine and disease

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 1. Volcanic hazards
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  • 2. Why to study volcanic hazards?

 Today, about 500 million people live within a

distance of 100 km from an active volcano.

 Twice during the 20th century, 2 large towns were

destroyed by eruptions: St Pierre (Martinique) in 1902, Armero (Colombia) in 1985.

 Major population centres lie within 10 to 20 km

from several large volcanoes with a likelihood of eruption during this century.

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  • 2. Why to study volcanic hazards?

 It is needed:

– to minimize the risk of loss life from structure collapse

  • r damage;

– to facilitate appropriate warning and evacuation

systems;

– to protect food-producing areas and other areas of

significant economic activity;

– to improve the expected performance of structures

and lifelines;

– to improve the functional capability of structures and

lifelines and to minimize the risk of damage to hazardous facilities.

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  • 2. Why to study volcanic hazards?

World map showing the main seismic and volcanic zones

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  • 2. Why to study volcanic hazards?

Flow chart

Steps and tasks to be carried out

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  • 3. Effusive eruption

 Lava flow

– A construction invested by a lava front reaches

unavoidable destruction.

– Lava flow produces a

lateral horizontal pressure which can cause the collapse of the buildings.

– Its high temperature

may also affect the material strength.

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  • 3. Effusive eruption

 Lava flow

– Passive protection:

 Proper planning of the territory and of the

emergencies management.

– Active protection:

 Containment and/or deviation of lava flows through

barriers, able to withstand lateral thrust of flow and high temperatures (e.g. barriers of earth).

 Needs to study more efficient and more easily

erectable innovative barriers.

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  • 4. Explosive eruption

 Air fall deposits

– Cover the topography with uniform thickness. – Can be considered as a gravitational distributed load.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 4. Explosive eruption

 Air fall deposits

– Air fall deposits are weather dependant: – The high temperatures (200-400 C) may produce

important thermal degradation of the mechanical properties of the materials. Density & load comparison: 10 cm of snow ↔ 10 cm volcanic ash

Load type Unit weight (kg/m3) Load (kPa) New snow 50-70 0.05-0.07 Settled snow 200-300 0.2-0.3 Dry uncompacted ash 500-1,300 0.5-1.3 Wet compacted ash 1 000-2 000 1.0-2.0

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 4. Explosive eruption

 Air fall deposits

– One of the eruptive phenomena with greater risk for

existing buildings and infrastructure.

– The expected impact involves a very large area

linked:

 to the direction and intensity of the wind,  to the type of eruption, – The are removed from the most steep slopes and

accumulated in the valleys.

– Affect transportation networks.

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  • 4. Explosive eruption

 Pyroclastic flows

– The most dangerous phenomena produced during an

explosive eruption

 Gas-solid dispersions with high or low concentration

  • f particles moving along the surface under gravity

action.

– Characterized by high

  • temperatures. Can be

partly fluidized.

– The modelling of the

phenomenon is very complex.

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  • 4. Explosive eruption

 Pyroclastic flows:

– Can produce high damages to the

built environment in areas near to the vent.

– Effects can be critical because of the

combination of mechanical impact and thermal stress on the vertical surfaces of buildings:

 main damages: impact on

  • penings,

 a fire risk is associated with the

flow passage inside the building.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 4. Explosive eruption

 Pyroclastic flows:

– Action can be expressed by a uniformly distributed

static pressure.

– Temperature ranges: 200 to 350 C. – First elements to reach the collapse: glass windows

and shutters. Can be protected by more resistant panels.

– The lateral resistance of a building depends on the

design criteria applied in ordinary load conditions:

 an earthquake-proof building presents better

strength and stiffness capabilities than a not earthquake-proof one.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 4. Explosive eruption

 Flying fragments: bombs and missiles

– The larger clasts follow pure ballistic trajectories – Cause damage which depends on the kinetic energy

and the vulnerability of the struck object.

 A flying fragment can

impact the roofing or the walls of a building.

 It can hit the most

vulnerable parts, like the openings.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 5. Secondary events

 Lahars

– At the same conditions in terms of gradient,

granulometry, etc, their motion capacity depends on the water content and the ability of the flow to lose or to absorb water on the way.

– Effects on

constructions are comparable to those produced by debris flows.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 5. Secondary events

 Lahars

– Damage to buildings:  Hydrostatic and dynamic effects create lateral

forces bringing to failure and collapse openings and cladding:

– Density and velocity of the flow gives the

magnitude of dynamic forces.

– Hydrostatic forces depend on the height and

composition of the flow.

 Minor mudslides can cause abrasions and damages

to surfaces.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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  • 5. Secondary events

 Lahars

– Damages to buildings: Further damage can be caused to structural parts of

both masonry and reinforced concrete buildings, causing even serious cracks and damages, with structural failure involving foundations, due to erosion and soil liquefaction.

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  • 5. Secondary events

 Tsunami

– High waves can be produced by massive pyroclastic

flows when reaching the sea.

– This kind of hazard for the Gulf of Naples is not frequent,

but not negligible.

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  • 5. Secondary events

 Volcanic earthquakes

– All volcanic eruptions are accompanied by local seismic

activity.

– The seismic events that characterize an eruptive

phenomenon can be considered of low to medium intensity.

– The ash fall creates an overload on the roofs. It

increases the building mass modifying the response to seismic action.

– Seisms related to volcanic activity are volcano-tectonic

earthquakes and long period earthquakes.

– Masonry buildings suffered much more, since its

frequency is close to that of the building.

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  • 6. Impacts of ash fall

 Health  Structures  Agriculture & Environment  Water & Contamination  Electrical Distribution Networks & Computers  Aircraft  Land Transport Infrastructure  Emergency Management  Cost Impact Assessment

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  • 7. Impacts of pyroclastic flows

 Behaviour of buildings shouted by

pyroclastyc flow

– Damage resulting from the impact of pyroclastic

flows on buildings depends on the combination

  • f several factors:

 the duration of the phenomenon,  the temperature of the flow,  the pressure produced by the impact. – The flow infiltration can lead to the destruction of

the building.

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General Report – Topic 1.5: Actions due to volcanic eruptions

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 Building behaviour shouted by

pyroclastyc flow

– 3 different typologies of vulnerability are to be

distinguished:

 vulnerability of the major elements (masonry

walls, frame),

 vulnerability of non-bearing (coverage,

cladding),

 vulnerability as "permeability" to infiltration.

  • 7. Impacts of pyroclastic flows
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General Report – Topic 1.5: Actions due to volcanic eruptions

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Conclusion

 The COST C26 action regarding the Vesuvius

case must allow better understanding of the behaviour of an urban area under volcanic eruption and its consequences.

 The description of volcanic hazards and of their

related actions may been used to propose some technical solutions in order to reduce the impact of such an event on an affected region.

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Urban Habitat Constructions under Catastrophic Events

FINAL CONFERENCE. Naples, 16th - 18th September 2010

Wait a minute, please! The COST C26 action is not fully achieved!

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Urban Habitat Constructions under Catastrophic Events

FINAL CONFERENCE. Naples, 16th - 18th September 2010

Final report – Topic 1.5: Actions due to volcanic eruptions Thank you for your attention