Hazards Exam😈-Slope Processes

Slope Processes!

human infrastructure

landslide risks+societal impacts increase with

heavy rains resulted in huge mass movement, 158 people dead, 100 missing, 50 hospital

Myanmar jade mine

large rockfall changed induced debris flow, 8 dead and massive damage to Bondo

Bondo Switzerland

heavy rain started landslide which derailed train, 11 injured

St. Moritz railroad

steepness, lack of vegetation, bedding planes, joints/fractures, water, loose soil, sudden shocks

preconditions for slope failure

types, angle, shapes

slope classifications

bedrock or unconsolidated material that has a angle greater than 2 degrees

slope

runoff, erosion, deposition, volcanism, tectonics, orogenesis, anthropogenic activities

slopes are formed by:

tectonic, erosional, of accumulation, artificial

types of slopes

2-15

low-angle slope degrees

15-70

high-angle slope degrees

>70

wall like slope degrees

convex, linear, concave

shapes of slope

rock fall, landslides, catastrophic long run-out landslides, active layer detachment, earth flow, debris flow, mud flow, lahar, avalanches, glacier avalanches, quick clay slides, tsunamis from rockfall or submarine slope failure

types of slope failure

complex slide

combination of two or more types of sliding, flowage, and occasionally falls

rapid slope movement with low water content

falls

bedrock slides on planar surface

translational rock slide (rock slide)

cohesive blocks of earth slide on curved surface

rotational rock slide (rock slump)

rapid slope movement with high water content

flows

earth, debris and lahar

types of flows

earthflow

downslope movement of a wet, partially cohesive, and internally deformed mass of soil and weathered rock

debris flow

fluid mixture of rocks, sand, mud and water that is between a landslide and a water flood

rapid flow with high to low water content

avalanche

debris avalanche

a granular flow of various combinations of snow, ice, debris, loose rocks or soil that moves rapidly downslope

extremely slow movements

soil creep/solifluction

solifluction

gradual movement of wet soil on top of an impermeable frozen zone (permafrost)

soil creep

very slow, downslope movement of sediment and soil

wet/fast, dry/fast, dry/slow

water content/speed for: flow, slide, heave

shear strength is decreased, shear strength is increased, or both

landslides happen when

saturation of soil, snow melt, reduction of vegetation

events that can cause landslides

root systems hold soil in place, removes water from underground

how vegetation increases stability

wildfires burnt areas that then got heavy rainfall, 268 mass movements

Southern California

orientation of weakness (bedding planes)

relative stability of slope is a function of

modulated by competition between shear force and shear strength

stability of a slope

coefficient of friction

quantifies the degree of roughness between two surfaces

force parallel to inclines plane, pulls slope downhill

driving force

w * sin(theta)

driving force equation (Fp)

shrunk by 40 percent in Noway in last two decades

permafrost

permafrost thawing, rain events in spring and fall, freeze thaw, monitored with InSAR, movement started slowly, large rockslide 2019

Mannen rockslide Veslemannen rockslide

Brienz 2023

deep seated landslide, continuous movement with some sudden events, monitored with GPS trackers, threat for village, cows/villagers evacuated, have automatic early warning systems for road closures,

Lovatnet

1905 huge rockfall pushed scree into wave, resulted in 40 m high wave, killed 61 people, destroyed 60 houses, settlements rebuilt, NGU said it was okay, 1936 rockfall resulted in 74 m high waves. 74 people died, 100 houses, did not rebuild, small rockfalls could have been warning signs

larger rockfall events

increasing number and volumes of rockfall are precursory to

high amounts of precip, freeze-thaw cycles, disintergration of permafrost, human constructions

dangers of slope failures in norway (things that amplify)

little ice age (beginning of 19th century)

since when has the climate been warming and permafrost shrinking

mud, debris and hot ashes, one of most destructive

lahar

kvikkleire

salts were leached from clay deposits, load placed on deposits can cause liquefaction