+ All Categories
Home > Documents > Landslide Basics Section1 Post

Landslide Basics Section1 Post

Date post: 27-May-2017
Category:
Upload: rebecca-buchanan
View: 223 times
Download: 1 times
Share this document with a friend
100
Hazard Risk Mitigation and Emergency Preparedness Project Component C.5 Experimental Studies regarding Landslides and Development of Standard Monitoring Manuals Landslide Hazards, Mitigation, and Risk Management
Transcript

Hazard Risk Mitigation and Emergency Preparedness Project

Component C.5Experimental Studies regarding Landslides and Development of Standard Monitoring

Manuals

Landslide Hazards, Mitigation, and Risk Management

9 March 2009

We’ll discuss:

• Training program approach and objectives

• Landslide basic mechanisms

• Mitigation strategies

• Examples and case studies

Training Program Overview

• The program will train design professionals, stakeholders, decision-makers, educators, students, and the public on landslide hazards and mitigation strategies and tools.

• The program will provide technical and non-technical training on the primary phases of the project, including: methodology, field reconnaissance and data gathering, site investigation, monitoring, data interpretation, stability analysis, modeling, and mitigation measures.

Objectives of the Training - Summary1.Technical knowledge transfer that will enable users to

operate and maintain the landslide monitoring equipment;

2.Technical and non-technical knowledge transfer and capacity building to enable Romanian engineers and scientists to develop and implement similar projects, including the monitoring system;

3.Technical and non-technical knowledge transfer that will increase awareness and understanding among stakeholders and decision makers to mitigate landslide hazards, promote sustainable development, and reduce long-term losses from landslides.

Specific Learning Objectives• Following this comprehensive program, trainees will be able to:

– Operate field monitoring equipment– Establish monitoring program for landslide-prone areas *– Explain the basic causes of landslides*– Identify regions in Romania most susceptible to landslide*– Evaluate the risk and scope of landslide problems throughout Romania* – Identify triggering factors, such as rising ground water levels* – Conduct detailed site investigations*– Perform detailed stability analyses*– Perform detailed numerical analyses– Evaluate mitigation options*– Conduct landslides hazard assessments*– Develop landslide mitigation strategies* – Conduct emergency response & evacuation planning

Methodology and Core Principals• Approach to be used is one of partnership between the project

team and personnel at the national, local, community, academic, and private sectors

• We view training program as a dialogue• We have some expertise, but solutions will come from all of us• Very important to share knowledge and lessons; often new

solutions come from dialogue about share interests or problems• This training and study are a vital part of the development of

sustainable mitigation solutions for landslide hazards in Romania.

• Lessons learned here, and relationships formed, can be used to solve other natural disaster problems, such as earthquakes

• The education and training program is designed to be sustainable, providing benefits that last after the project is over

Methodology and Core Principals• The overarching objective is to provide knowledge and

knowledge and technology to mitigate landslide hazards– training not so much about prevention as it is awareness

• The training program will involve 20 days of training in Romania, and 3 days in Switzerland.

• Training shall be given using:–Workshops and seminars–Regional conference–University & school curricula (this is key, as shown in Turkey,

9 yr. old in 2005 tsunami)→ students are designers of our future

–Informal (e.g. when meeting home owners) –Interactive website and project manual

2004 Indian Ocean EQ & Tsunami

Methodology

• Training for everyone -- key stakeholders, decision-makers, students, etc. -- about the project, landslide hazards, and mitigation strategies.

• We will adjust as necessary for background, language, interests; first day not technical

• We want input from you as to how to make the program most effective

• Hands on demonstration of software, field site visit are two highlights

Questions to be answered:• What are landslides? What are the basic causes?

What are the different types of landslides?• Where do landslides typically occur? What are the

conditions most prone to this activity? How do we recognize these areas?

• What kind of damage is caused by landslides? How big is this problem nationally and globally?

• What can we* all do to mitigate– that is, reduce our losses-- from these hazards?

_____________*“we” means all who impacts or is impacted by the risk

What is a Landslide?

• Landslide: Downslope movements of a earth materials slope (mass of rock, of soil or of debris) controlled by gravity.

• Landslide hazards occur in almost every part of the world where there are are hills or mountains

• Landslides are part of the natural erosion and weathering process of the earth-- a continued re-leveling of the surface, both on the land and under the sea (submarine slides)

Important Terms and Definitions• Hazard – the expected occurrence or likelihood of

damaging future events such as landslides, often expressed in qualitative terms (i.e., high, low) or probability (% chance).

• Vulnerability: the level of population, property, economic activity, including public services, etc., at risk in a given area due to the occurrence of a landslide.

• Risk – the expected consequences of future landslides; expressed in lives or dollars lost; (risk = hazard x vulnerability)

• Disaster - A serious disruption of the functioning of society (local, regional, or national), causing widespread human, material, or environmental losses which exceed the ability of affected society to cope using only its own resources.”

Landslide Hazards • Some landslides are slow and gentle and cause

little damage; some are fast and destructive--- when people are in the way the natural process is termed a “catastrophe” or “disaster”

Disasters by Design?

• Landslide hazards are inevitable, but landslide disasters can be prevented

• Question: Do we “design our own disasters?”

2005 Hurricane Katrina• Four years after 9/11 and with an emphasis on “homeland security”, a long-

anticipated hurricane overwhelms a vulnerable coastline, meets unprepared governments, and inflicts lasting damage on population A superpower fails to meet the most basic needs of its citizens;

• More than 500,000 displaced; worst US human crisis since The Great Depression; we received aid from foreign governments, including Sri Lanka and Bangladesh

• Illustrated the disproportionately higher vulnerability of impoverished citizens

• Signaled clear mandate for change…

Sustainability and Sustainable Development

Sustainability:

“Forms of progress that meet the needs of the present without compromising the ability of future generations to meet their needs”

World Commission on Environment and Development, 1987

Sustainable Development

Sustainable Development Considers:

• Economic Benefits

• Environmental Impacts

• Social Impacts

A Key Question• How can we balance the economic,

social, environmental, and political factors that allow us to make wise, informed, ethical and sustainable development decisions that satisfy the collective interests of all involved?

… we will provide some information and ideas in this training that can be used to begin to address this question

Implementation of Optimal Solutions Requires:

1. Knowledge and Tools (i.e., science, engineering)

2. Guiding principals – (i.e., sustainability)3. Leadership – by anyone

→ Learning from the past, especially failures is vital .. So let’s look and learn with case histories today

Landslides - Basic Mechanisms• Landslides have one feature in common– there is

movement of a large body of soil along more or less definite surface

• In many case the earth remains intact during the first stages of movement, but finally become distorted n broken up as movement progresses.

• Some failures occur suddenly with little or no warning

• Others take place slowly, indicating their intentions by ongoing small settlements or formation of cracks

Landslides - Basic Mechanisms

• Landslides may be sudden and catastrophic, or gradual in movement.

• Landslide activity can be continuous or intermittent. It is common for ancient landslides to be reactivated due to engineering activities or other activities.

• Landslide terrain has a characteristic morphology, commonly described as “hummocky”

Hummocky Terrain

• All landslides have triggering causes or factors. These factors either:

A. Increase the load, or B. Decrease the resistance

→Cutting and removing the toe of a slide is an example of decreasing the resistance;

→Adding fill at the top of a slide is an example of increasing the load.

• This means mitigation steps involve…??

Landslides - Basic Mechanisms

Landslides - Basic Mechanisms• Movement occurs when the shear strength of the

soil is exceeded by the shear stresses over a relatively continuous surface

• Failure at a single point does not necessary mean the entire soil or rock body will be unstable

• Instability results only when shear failure has occurred at enough points to define a surface along which movement can take place

• Therefore, anything that produces a decrease in soil strength or an increase in stresses contributes to instability should be considered in design

Landslides - Basic Mechanisms• Gravity is main driving mechanism.

• The factor of safety against slope failure is defined as the ratio of the shear strength to the shear stress required for equilibrium, along the critical failure plane.

• FS = Shear strength/Shear stress required for equilibrium

Landslides - Shear Strength • The shear strength of a material is typically defined by the

following equation: • S = n’ tan Φ’ + C’ Where: S = shear strength of material (can change w/time)

C = cohesion

n’= normal stress Φ = friction angle of material

• The shear strength is typically estimated by laboratory tests and/or in-situ field measurements.

• This parameter is usually the most uncertain when performing slope stability analyses, especially for natural slopes. The shear stress required for equilibrium can be determined from statics.

Landslides – 3 Main Ingredients

Factors Involved in Stability Increases Driving Stresses: Decreased Strength (Resistance):* External Loads such as buildings, water, or snow

* Swelling of clays or adsorption of water

* Increase in unit weight by increase water content

* Pore water pressure increase (rise in water table, shearing generates pore pressure)

Removal of soil near toe of slope by excavation

* Breakdown of loose structure with shock, vibration, or earthquake

*Undermining , cause by tunneling, collapse of underground caverns or seepage erosion

* Cracking from swelling and shrinking

Shock, caused by earthquake or blasting Strain and progressive failure in sensitive soils and brittle rocks

*Water pressure in tension cracks * Thawing of frozen soils

* Deterioration of cementing agent

* Loss of capillary tension upon drying (loss of cohesion)

* Weathering– chemical or biochemical deterioration (i.e., hard shales can break down into soft clays)

*Note: water is involved with this process.

Additional Causes of slope failure• There is never just one cause of failure, there is always

combination even though one may have been the triggering factor; we are often asked to determine the cause of failure but there is always more than one

• Water is almost always a major factor • Earthquakes and human activities can also induce slope

failures. Ground shaking can increase shear stresses and decrease shear strength (i.e., Romania)

• Vertical slope cuts during some construction projects, especially for highways, can reduce the stability of slopes. If the slope is not supported, it can fail.

• Soil properties can change over time

Examples…

Mud flows - the most dangerous type of landslide

Val Pola Italy, 1987 – 35 million m3

Mud slide - USA

Leyte, Phillipines 2006

Phillipines 2006

Phillipines 2006

Mudslide - USA

Panalau Village- Buzau Subcarpathians 1975

La Conchita, CA – 1995 1.3 million m3 mudslide

Thistle Creek, Utah – 1983 $400 million damage

Panama Canal – landslide costs?

Roadway damage

California, USA

Impact of cleanup on Factor of Safety?

Mudslide - USA

Deep-Seated Slide in U.S.A.

Blidisel Hill in the Buzau Subcarpathians

Earthquake-Induced Landslide (M7.1)

El Salvador 2001 (M7.6 Earthquake)

Japan – Amazing Video

http://www.youtube.com/watch?v=f19Onak6KC0

Overall impact on society?

Evolving Risks, Challenges & Solutions• Will face increasing threats of this type due to global

warming as number and intensity of rain storms will increase

• Increasing population, development

• Increased human activity (i.e., such as causing such as water infiltration)

• Impacts are multidisciplinary (social, economic, environmental) so solutions must be multidisciplinary also

Lessons From Landslides

• We must learn from what we see

• Observational powers very important, especially for natural slopes…how do we use this? Why so important?

• We must share lessons and knowledge, but to do this we must first understand key mechanisms

Landslide Case Histories – Valuable Lessons…

Serpentine rock had degraraded

Lessons Learned

• Deep slides activated by longer periods of rainfall period (months, years)

• Shallow slides activated by heavy rainfall in short time (days, weeks)

• Deep slides can move fast or slow; deep slides will move fast if the soil looses strength as the slide begins to move.

• Shallow mud flow slides generally most deadly

Key Lessons• Difficult for homeowners to get engineering expertise to

help them deal with landslide damage. • Why not? Fees generated from residential work do not

justify the potential legal exposure of geotechnical firms. • The typical residential investigation might generate fees of

a few thousand US dollars, but the firm may be liable for millions of dollars.

• In the previous case, even an engineer who was a neighbor and just an observer was sued

• Result- few quality firms will do residential work, and thus homeowners are really the ones that lose in the end.

• Landslide insurance-- Can’t get landslide insurance unless you’re on flat land and don’t need it

Implementation of Optimal Solutions Requires:

1. Tools – knowledge, maps

2. Guiding principals - sustainability

3. Leadership – by anyone

1. Tools

• Landslide susceptibility maps are important knowledge and communication tools

• Maps lay groundwork for comprehensive holistic management and development plan

• But remember- it’s also the planning not the plan that is critical

2. Guiding Principals Sustainability and Sustainable

DevelopmentSustainability: “Forms of progress that meet the needs of the present

without compromising the ability of future generations to meet their needs”

World Commission on Environment and Development, 1987

Sustainable Development

Sustainable Development Considers:

• Economic Benefits

• Environmental Impacts

• Social Impacts

Sustainable Development Encompasses:

• Efficient management of energy and water resources

• Management of material resources and waste • Restoration and protection of environmental quality • Reinforcement of natural systems • Analysis of the life cycle costs and benefits of

various materials and methods • Integrated decision-making process -- requires

understanding of full context of decisions, including social, economic, etc. impacts

Things That Inhibit Sustainability

•Short-term risk view, such as developers have, or politicians due to election cycles (1992 Hurricane Andrew)– the issue of landslide mitigation in Romania requires long-term view

•Lack of public value and policy- lack of education

•Politics – (i.e. current regional fragmenting of municipalities un-adopting IBC code for seismic design in US)

Things That Promote Sustainability:• True sustainable development will be successful only if

it is integrated into daily activities of everyone who has influence on future losses

• Need cultural shift to that favors and promote greater sustainable development

• We can help lead this shift by promoting greater acceptance of sustainable development and make resource management and sustainability practice consistent with this, and by…

• Education and communication

Education and Communication• Raise awareness of everyone to better understand and

appreciate emerging risks and trends

• Share information and experience worldwide- -provides economy of scope

• Maps and posters are effective communication tools

• Recognize that public actions from risk communication results mainly from hazard “intrusiveness”

• Educational programs should include young people- make new generation aware—they often have better ideas than we do (i.e., 2004 tsunami)

3. Special Issues and Challenges:

• Need for follow up, reassessments- continuous stewardship that maintains continuity over long periods of time (i.e., unlike w/New Orleans levees in Katrina)

• Private efficiency vs. public vulnerability – understand inevitable “conflict”; also tendency to localize profits, globalize risks

• In US for example, Hurricane Katrina experience- private firms provided about 85% of the critical resources; very poor public-private coordination

Increasing Interplay Between Private Sector & Public Vulnerability:• About 85% of the shopping malls, office buildings, theaters,

factories, energy installations, and airlines—all of which are vulnerable to attack or natural disaster—are owned by private business.

• Even though transportation facilities, such as airports, bridges, dams, harbors, and tunnels, are typically owned by municipalities, states, or federal authorities, the planes, trucks, railcars, and ships that use these facilities are privately held .

Dialogue with Stakeholders• Understand the importance of dialogue and

encourage it among all stakeholders- dialogue among public and private stakeholders before problem is critical

• Form local communities of practice, but with private sector also (i.e., AHC in US)

Summary• Need over-arching, long-term holistic view for

sustainable solution

• Maps are key step toward sustainable water solution

• Stewardship of project over time required for maximum return on initial investment and benefits

• Dialogue among all stakeholders is critical

Benefit of Education for Hazard Mitigation


Recommended