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2011 | Buch

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Introduction to the Physics of Landslides

Lecture notes on the dynamics of mass wasting

verfasst von: Fabio Vittorio de Blasio

Verlag: Springer Netherlands

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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Über dieses Buch

Landslides represent one of the most destructive natural catastrophes. They can reach extremely long distances and velocities, and are capable of wiping out human communities and settlements. Yet landslides have a creative facet as they contribute to the modification of the landscape. They are the consequence of the gravity pull jointly with the tectonic disturbance of our living planet.

Landslides are most often studied within a geotechnical and geomorphological perspective. Engineering calculations are traditionally applied to the stability of terrains. In this book, landslides are viewed as a physical phenomenon. A physical understanding of landslides is a basis for modeling and mitigation and for understanding their flow behavior and dynamics. We still know relatively little about many aspects of landslide physics. It is only recently that the field of landslide dynamics is approaching a more mature stage. This is testified by the release of modelling tools for the simulation of landslides and debris flows. In this book the emphasis is placed on the problems at the frontier of landslide research. Each chapter is self-consistent, with questions and arguments introduced from the beginning.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction and Problems

Abstract

On May 31, 1970, a strong quake shakes the Peruvian Andes, causing the collapse of 50 million cubic meters of rock and ice from the mountain called the Nevados Huascaran. After 500 m of free fall, the material collapses against the glacier 511; disintegrating at once, it generates a shock wave. An ominous black cloud composed of pulverized material develops in the area of the impact, obscuring part of the Nevados. Traveling rapidly across the glacier, the material reaches astounding velocities, perhaps greater than 90 m/s. Huge boulders are cast in the air. Bombarding locations some kilometers away, boulders kill people and cattle and devastate a large area. The intake of water and ice rapidly transforms the solid material in a debris flow, a lethal and rapid river of dense fluid capable of carrying huge boulders with colossal devastating power. The towns of Yungay and Rahnrahirca are shattered and 8,000 of the inhabitants killed. The area is completely covered with a heavy muddy deposit. Reaching the river Rio Santa, the debris flow increases its death toll in the town of Matacoto.

Fabio Vittorio De Blasio

Chapter 2. Friction, Cohesion, and Slope Stability

Abstract

Every solid or liquid mass on Earth is influenced by gravity. A mass of soil or rock remains stable if the gravity force is counterbalanced by the reaction forces exerted by the adjacent bodies and the terrain. Rock masses and soils on the surface of the Earth appear steady at first sight. However, this impression is often deceiving, as the masses may slowly creep, terminating with a sudden collapse. Natural buttressing of a potential landslide may be removed of weakened, causing portions of the mass to fall. Change in stability conditions may be consequent to a variety of causes such as river undercutting or ice melting. Earthquakes can instantly change the local force equilibrium, anticipating the fall. The process of mountain building continuously overloads rock masses with renewed stress throughout time scales of several million years. Newly produced deposits may also become unstable. For example, volcanic eruptions deposit enormous amounts of pyroclastic materials, which may subsequently be mobilized by rain.

Fabio Vittorio De Blasio

Chapter 3. Introduction to Fluid Mechanics

Abstract

Everyone is familiar with matter in the fluid state such as air, water, or oil. The most obvious attribute of a fluid is its capability of flowing. Fluids can travel down slope like water in a river or crude oil flowing along pipes; they give rise to currents in the presence of a pressure gradient, such as wind created by pressure differences in the atmosphere. Fluid mechanics, the science of fluids, is crucial not only in science, but also in engineering problems like the flight of an aircraft and the lubrication of joints in an engine. Fluid mechanics is a complicated and varied subject where new experiments and theoretical calculations are constantly reported by scientists and engineers. This is testified by the numerous (in the number of some hundreds) original papers appearing monthly on specialized journals.

Fabio Vittorio De Blasio

Chapter 4. Non-Newtonian Fluids, Mudflows, and Debris Flows: A Rheological Approach

Abstract

People living in the lowlands around Mount Rainier, a stratovolcano of the Cascade mountains (USA), dwell on top of ancient landslide deposits. These deposits are due to mudflows descended from the top of the volcano in periods when the area was scarcely populated. However, Mount Rainier is still an active volcano; mudflows are certainly a current hazard. There are several other regions in the world at risk for volcanic mudflows, otherwise known as lahars. These flows are composed of a mixture of clay, silt, water, and coarser material like large blocks. They may be very fast and devastating. Wet mixtures of soils with clast size from clay to boulders are known with the generic name of debris flows. They are not necessarily volcanic but can derive from the failure of superficial soil in mountain environment, or even on flat areas in proximity of the sea.

Fabio Vittorio De Blasio

Chapter 5. A Short Introduction to the Physics of Granular Media

Abstract

Granular materials are ubiquitous in many natural and industrial processes. The extraction, storage, grinding, and separation of ores are made with rock in the granular state. Granular media are also common in agricultural, food, and pharmaceutical industry. Practical problems frequently occur when dealing with granular media. Arches form with granular flows through pipes, to the point that the flow is often interrupted. Segregation takes place between granular materials made up of grains of different size.

Fabio Vittorio De Blasio

Chapter 6. Granular Flows and Rock Avalanches

Abstract

“A huge mountain took apart from the others, and traveled through the entire valley to join the other peaks on the opposite side, so blanketing the villages with earth and stones.” So a Polish monk describes the disaster of the Mount Grainer landslide in Savoy, France, 1248. The Alps have been several times the place of deadly large rock failures. Dante Alighieri in his Divine Comedy describes the scar of the Lavini di Marco landslides in Italy, speculating on the possible role of an earthquake or lack of support as a possible cause. Large deposits of much older landslides, historical and pre-historical, remind us that huge rock avalanches are an actual threat for mountain communities.

Fabio Vittorio De Blasio

Chapter 7. Landslides in Peculiar Environments

Abstract

Several disasters have been caused by landslides and rock avalanches falling onto natural or artificial water basins. The most studied case occurred in northern Italy on October 9th, 1963, when a volume of \( 270 \times {10^6}\;{{\hbox{m}}^3} \) of limestone collapsed into the artificially dammed Vaiont lake. The dam survived the impact, but water overtopped the dam by about 200 m; the ensuing water wave took 2,000 lives. Many investigations have been devoted to the Vaiont failure, mostly related to the hydraulic and mechanical history prior to the landslide. Probably the disaster could have been avoided if the danger of landslides falling at high speed in water reservoirs and their capability of displacing the water had been recognized.

Fabio Vittorio De Blasio

Chapter 8. Rockfalls, Talus Formation, and Hillslope Evolution

Abstract

In contrast to a rock avalanche, which involves the flow of a large mass, a rock fall (or rockfall) is the movement of a single block. The product of rockfalls often appers as a rock heap, a talus, at the foot of mountain slopes. Although rock falls exhibit less mobility than a rock avalanche, they are far more common. Rock fall-prone areas are usually steep rock cliffs in mountain areas, especially if subject to frost–thaw activity in the rock joints. Rockfalls are a significant safety problem in mountainous areas, as single falling boulders may kill people, interrupt roads and railways, and demolish buildings. Moreover, the opportunity of building settlements, houses or hotels at the foot of mountains is often limited by rockfalls. It is thus advantageous to be able to predict the extent of these phenomena and the distance from the mountain foot where the terrain can be considered safe.

Fabio Vittorio De Blasio

Chapter 9. Subaqueous Landslides

Abstract

On July 17, 1998 an earthquake shook the north-eastern shores of Papua New Guinea. The earthquake itself was not a particularly powerful one, and did not elicit much concern among the population, used to live on a seismic land. But after some minutes the sea level began to fall rapidly, unveiling the sea bottom along the shore. After short time, a first pulse of a series of three tsunami waves was travelling landward. Water towered 15 m above normal level, killing about 3,000 persons.

Fabio Vittorio De Blasio

Chapter 10. Other Forms of Gravity Mass Flows with Potentially Hazardous Effects

Abstract

It is useful to briefly consider other gravity-driven mass flows, and their differences and similarities with landslides. In this chapter we limit ourselves in illustrating a few basic facts about lava streams, ice avalanches, flash floods due to dam breaks, snow avalanches, and turbidity currents. A brief discussion on slow landslides is also included.

Fabio Vittorio De Blasio

Backmatter

Titel: Introduction to the Physics of Landslides
verfasst von: Fabio Vittorio de Blasio
Verlag: Springer Netherlands
Electronic ISBN: 978-94-007-1122-8
Print ISBN: 978-94-007-1121-1
DOI: https://doi.org/10.1007/978-94-007-1122-8