the frictional forces on Triggering mechanisms are processes or events that a sl
ID: 288122 • Letter: T
Question
the frictional forces on Triggering mechanisms are processes or events that a slope and/or Internal friction or shear strength control the resistance to failure of slopes. Slopes made of . the effect of gravity. (higher or lower) internal friction unconsolidated sediments tend have than slopes composed of solid rock. When planar surfaces (slip planes) become inclined (due to tectonic forces, for example), sliding is likely to occur in the downslope direction. . o What type of slip plane occurs in sediments and sedimentary rocks only? o What type of slip plane occurs in metamorphic rocks only? o What type of slip plane can occur in any rock type? Describe one way slopes can become oversteepened naturally. . Describe one way slopes can become oversteepened due to man-made activity. . Water within pore spaces in unconsolidated sediments can strengthen a slope when only a thin layer of water is present resulting in electrical attraction between water and the mineral grains/sediments. When additional water is added to slope material beyond this small amount, friction between sediments, which contributes to slope failure. Additionally, water adds to slopes, contributing to slope failure. Describe one way, besides rainfall, how climate influences mass wasting. . . How do earthquakes affect the frictional forces within slopes? .Explanation / Answer
1) Triggering mechanism on a slope decreases the frictional forces and increases the effect of gravity.
2) slope made up of unconsolidated sediments tend to have lower internal friction than slopes composed of solid rocks.
3)slip planes in sediments and sedimentary rocks - Bedding planes
slip planes in metamorphic rocks - foliation plane
slip planes in any type of rocks- Inclined beds and fracture planes
4) Natural processes such as excessive stream erosion from a flood or coastal erosion during a storm can oversteepen slopes. hence during heavy rainfall , water discharge increases over the slope and induces erosion.
5)Excavation into a slope (for a road or construction site) creates a flat area at the base of a slope. However, it also oversteepens the slope. Removing the basal support can result in slope failure. This is the example of oversteepening of slope by man-made activities.
6) When additional water is added to slope material beyond the small amount , friction decreases between the sediments , which contributes to slope failure , Water adds Erosion or lubrication to slope , contributing slope failure.
7)Climate can have a dramatic influence on mass wasting events. Areas with a moist temperate climate are subjected to frequent freeze and thaw cycles. Freeze-thaw cycles affect rocks because when water seeps into cracks in a rock and then freezes it expands putting tremendous pressure on the rock, forcing the cracks to expand. Over time this type of physical weathering can cause even the strongest rocks to break apart. Sometimes this process is referred to as frost heaving or freeze thaw action. Thermal expansion and contraction of rock bodies also may occur in areas with extreme temperature variations and this likewise affects the stability of rock. Moisture, in addition to its influence through freeze thaw cycles (physical weathering,) can actually dissolve some of the minerals that rocks are made of. This is called chemical weathering and it also affects the stability of rocks and induces Mass wasting.
8) Earthquakes produce horizontal and vertical accelerations in soil masses. The horizontal accelerations may reach as much as 0.5g (where g is gravitational acceleration), altering the distribution of forces in hillslopes in a manner equivalent to a temporary steepening of the slope. thus earthquakes reduces the frictional force within a slope.
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