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Hazards Associated with Slope Stability & Mass - Impermeable layers which obstruct Landslides tend to occur where here are steep
Movement groundwater flow and provide lubrication sloes, weak underlying rocks or weak
to slip surfaces. structural planes like joints or fault planes.
Steep, loose slopes like screes aren't the only - Occurrence of slipper rocks such as Human activity such as deforestation and
slopes that are unstable. Gentle slopes that are clay, evaporate, anthracite urbanisation often contributes to slope failure in
covered with soil and vegetation may also developed areas.
move, if only a little slowly.
- Down slope dip of potential slip planes
such as bedding joints, faults and In areas which are prone to landslides, risk
Slope Failure: schistosity. assessments are carried out and maps of
The surface soil and rocks break away from the potential dangerous areas are prepared.
main mass and slip or slide to the bottom of the The Causes of Mass Movement:
slope. Deforestation- the roots of the trees holding the Methods that are effective in reducing dangers
This happens because the slope is subjected to soil together are removed. in possible landslide area include;-
stress. There is always some degree of stress on Bad farming techniques- mainly livestock such
as sheep, can cause overgrazing.
- Using planning regulations to control
the rocks from the force of gravity. Stress may be the sitting of the buildings.
increased by the slope becoming saturated with Meandering rivers- erosion producing river cliffs.
Spoil heaps- over steepening of the slopes. - Using building codes to endure that the
rainwater, or tremors caused by earthquakes or slopes are stabilised.
quarrying. Vibration- can be caused by
If this happens, the stress exceeds the natural traffic/mining/earthquake causes shaking so the - Controlling drainage of vulnerable
strength of the slope and failure occurs. side of the slope falls. areas by using lined ditches and
Excess rain- cause's soil/land to liquefy shallow walls.
In many countries, the natural land surface has (saturates) pore water pressure and slope fails. - Reducing the load of overlying material
been extensively modified to suit the needs of Earthquake activity- ground shaking cause the head of unstable slopes.
human communities. Deforestation and farming slippage of surfaces. - Reducing the gradients of slopes
have brought about a change in vegetation, soil Volcanoes- ash and dust causes over prone to slipping.
and drainage since prehistoric times, and civil steepening and collapses.
- Building buttresses at the toes of
engineering and mining works have modified unstable slopes.
coastlines, river systems and landforms on an The Cures for Mass Movement:
Drainage- wells control the drainage. - Planting vegetation with extensive root
even larger scale. systems to stabilise slopes and reduce
Anchor bolts- strengthen the rocks and reduce
risk of slippage. the water content through
In almost all mass movements controlled by evapotranspiration.
gravity, water played a key role by reducing the Wire mesh- catches any scree that falls from the
strength and coherence of unconsolidated slopes. - Treating surface materials with
material or by lubricating potential slip River straightening- stops the erosion of the chemicals which promote reactions that
surfaces. land. stabilise the minerals in slopes.
Other factors that effect instability are the Sea walls/Gabions- stops the slope from - Filling permeable rock formations with
destruction of plant cover, the over steepening slipping. cement to reduce pore-water pressure
of slopes and the effects of vibration due to Terracing- stabilises the slope and reduced and pre-water circulation and thereby
earthquakes and other causes. surface runoff. increases the strength.
Grouting- filling in the gaps underground to - Increasing the insurance policy on
The properties of rock and soil that promote prevent ground collapse. property to discourage people from
mass movement under gravity include;- Reforestation- roots taking up the water and building houses in high risk areas.
- High pore pressure. supports the soil.
Re-profiling- removing spoil heaps and reducing
- Low cohesion in unconsolidated the amount of scree on the slope.
The money saved through this range of methods
material or fracturing planes. is up t 100 times the amount spent, and damage
can also be reduced by 90%.