20- Landslide Engineering Flashcards
Limit equilibrium analysis
To assess stability of slope, force equilibrium conditions are examines for a static slope equitation
Typical output from L.E.A is “Factor of Safety”
FS= resisting force/driving force = shear strength/shear stress
FS > 1.0 =stable situation
FS< 1.0 = denotes failure
Effective stress
The intergranular stress enabling friction
Cannot be measured, only calculated
High pore pressure and landslides
High pore pressure reduces effective stress, therefore affecting stability of slope
Decreases the frictional strength component along the sliding surface
Trigger- heavy rainfall
Rapid infiltration of rainfall cause a temporary rise in pore-water pressures
Leads to decrease in effective stress and safety factor
Trigger- earthquake shaking
Strong ground shaking during seismic activity is common trigger for landslides
Doubly destructive as both Induce shear stresses and weaken internal structure of slope material
Trigger- anthropogenic /human activity
Mechanisms for occurrence of landslide can be caused by human activity
Ex. Excavation of slope, loading of slope, drawdown of dam reservoir, blasting, etc
mitigation strategies - avoid the problem
Involves relocating facility, structure or route of a planned new road or rail line to avoid areas along which landslide hazards could be a problem
Use landslide hazard map to plan best route
Mitigation strategy- Prevention
Work towards preventing a landslide from occurring. Usually done by reducing the driving force or by increasing the resisting force
Mitigation strategy- protection
Accepts that landslide hazard will occur, but works to minimize any impact it may have. Done by employing protective structures that divert or stop the moving mass before they do any damage
Landslide prevention techniques
Remove source- remove unstable material
Reinforce source- apply a resisting force at toe of landslide(ex, concrete wall)
Reinforce with anchors- anchor unstable rock into deeper stable rocks
Reinforce through drainage- drain water to reduce pore pressure
Landslide protection techniques
Rockfall protection: Let rock falls occurs, but control distance and direction of travel (ex, barrier system, rockfall nets)
Debris flow protection
1. Remove debris from flow mass with barriers
2. Prevent more debris from being entrained (ex, concrete lines channels)
3. Decrease flows velocity and erosive capabilities (boulder embedded channels)
