An Introduction to Landslides and Mass Wasting

by

Robert Font, Ph.D., CPG, PG

Chapter 1 - Weathering, Sediment and Soil Formation

Understanding sediment and soil, how they are created, their composition and properties is essential to predict the behavior of earth materials that may be involved in mass wasting problems.

Chapter 1 covers:

• The concept of the "rock cycle"

• The subject of physical and chemical weathering

• Types and properties of sediment and soil
        The importance of particle size
              Their mineralogy
              Their specific properties
              The importance of "fabric"
        The problems presented by "sensitive soils"
        The concept of "weight-volume relationships" and the definitions of:
              Porosity and water saturation, as well as the concepts of
              pore pressure and effective stress
        The definition of Atterberg limits and indices, and:
              Factors which affect them
              Their practical applications and usage
              Their importance in predicting soil behavior in response to natural geologic hazards
        Problematic "swelling soils"
              Their types, as well as
              Proper methods of mitigation
  

The completion of our review of weathering, sediment and soil formation leads us to our next critical chapter.

Chapter 2 - Strength of Earth Materials

Understanding the strength of earth materials under specific field conditions is crucial to our knowledge of landslide problems and their solution and prevention.

Chapter 2 covers:

• The Coulomb-Mohr fracture criterion
        Basic strength theory
        The concepts of "cohesion" and "internal friction"
        The important strength equations and concept of the Mohr diagram
  

• We will also emphasize types of strength as dictated by field conditions, including:
        The concepts of un-drained, drained and residual strengths
        Factors affecting strength
        Field conditions influencing strength types
        The "problem" of predicting the real field strength
  

Chapter 3 - Mass Wasting

An understanding of the strength of earth materials is basic to address our final chapter.

Chapter 3 covers:

• The importance of controlling mass wasting

• A review of notable historical landslides

• USA statistics concerning annual loss of life and property

• Landslide classification including:
        Flows
              Slow flow (or creep)
              Rapid flows (including earth and mud flows, solifluction and liquefaction), and
              Specific case histories
        Slips
              Slides
              Slumps
              Specific case histories
        Falls
              Specific case histories
  

• Finally, we will address:
        Factors that influence mass wasting
        Control methods in mass wasting
        An introduction to the subject of slope stability analysis. In analyzing slope stability, we will cover:
              General theory and important equations
              Basic assumptions
              Specific methods of analyses, and
              The goal of determining the "factor of safety" for a slope
  

• We will conclude with a discussion of the:
        Limitations of the analyses
        Reviews of particular case histories