Mass Movements Flashcards
Name and describe the factors influencing slope stability.
Geology and Rock Type: Different types of rock and soil have varying degrees of cohesion and internal strength, affecting their stability on slopes.
Slope Angle and Height: Steeper slopes are generally less stable than gentler slopes, especially when combined with greater height.
Vegetation Cover: Vegetation helps stabilize slopes by reinforcing soil with roots, reducing erosion, and absorbing excess moisture.
Water Content: Excess water can decrease soil cohesion, increase weight, and lubricate surfaces, making slopes more prone to failure.
Climate and Weathering: Climate conditions and weathering processes can weaken rock and soil over time, reducing slope stability.
Human Activities: Construction, mining, deforestation, and other human activities can alter natural slope conditions, increasing the risk of instability.
What is “angle of repose”?
The angle of repose is the maximum angle at which loose material, such as sand, soil, or rock fragments, can remain stable on a slope without collapsing or sliding. It represents the equilibrium angle between the force of gravity pulling the material downhill and the resistance of the material to movement.
Name and describe three different types of mass wasting.
Landslides: Rapid downslope movement of rock, soil, or debris along a discrete surface, often triggered by heavy rainfall, earthquakes, or human activities.
Slumps: Movement of material along a curved surface, typically characterized by rotational movement and internal deformation.
Rockfalls: Sudden detachment and free-fall movement of individual rock fragments or blocks from a steep cliff or slope.
Describe why heavy rains increase the risk of landslides in some areas.
Saturation: Excessive rainfall saturates the soil, reducing its cohesion and increasing pore water pressure, making it more prone to failure.
Increased Weight: The added weight of water can increase the stress on slopes, especially on already unstable or weakened slopes.
Lubrication: Water acts as a lubricant, reducing friction between soil particles and rock surfaces, facilitating slope movement.
Erosion: Heavy rainfall can erode slope materials, undercutting the base of slopes and triggering mass wasting events.
What human activities contribute to slope instability? Explain these activities create instabilities?
Deforestation: Removal of vegetation reduces slope stability by removing root reinforcement and increasing surface runoff, leading to erosion.
Construction and Excavation: Alteration of slopes through excavation, grading, or construction activities can disturb natural slope conditions, leading to instability.
Mining: Excavation and blasting associated with mining operations can weaken slopes, leading to slope failures and landslides.
Poor Land Use Practices: Improper land use practices such as overloading slopes with structures, roads, or landfills can increase stress on slopes and contribute to instability.
Name and describe the methods that humans employ to prevent instabilities.
Vegetation Management: Planting and maintaining vegetation on slopes to stabilize soil with roots, reduce erosion, and absorb excess moisture.
Engineering Structures: Constructing retaining walls, rock buttresses, or soil reinforcement structures to stabilize slopes and prevent erosion.
Drainage Systems: Installing drainage systems such as French drains or surface water diversion channels to reduce excess water infiltration and pore pressure buildup.
Slope Grading and Terracing: Modifying slope angles and creating terraces to reduce slope steepness and redistribute weight, improving stability.
Slope Monitoring and Early Warning Systems: Implementing monitoring techniques such as inclinometers, GPS, and rainfall gauges to detect changes in slope stability and provide early warnings of potential failures.
