FACTORS RESPONSIBLE FOR LANDSLIDES

FACTORS RESPONSIBLE FOR LANDSLIDES
Slope instability may be caused by removal of lateral or underlying support mainly by river erosion and road cuts, landfill dumping, faulting, tectonic movement or the creation of artificial slopes by constructional activities.

Weathering involves rock disintegration, causing weak­ening of soil and decreased resistance to shearing. A significant cause of landslide is related to increased water infiltration which causes saturation of soil. It may be due to ploughing or poor organisation of drainage on a sloping area that has undergone modification due to deforestation and urbanisation. Pore water pressure is increased by soil saturation which results in a positive ff on the slope.
Landslides due to slumping may oc due to construction of settlement built filled up land that suffers from poor cc paction or engineering. In forests, tilT harvesting may negatively affect slope
bility. Tractors, in generaL cause imme damage as runoff follows the wheelin
Apart from the above-mentioned for the causes of slope failure may be dis guished as (i) immediate causes suer vibrations, earthquake tremors, heavy] cipitation and freezing and thawing; and long-term causes such as the slow
progressive steepening of the slope.
R.u. Cooke and J.e. Doornkamp (1' suggested a few factors that contribut, landslides.
(i) Factors leading to accelerated sl stress. surcharge i.e., loading of the crest ~f slopes \ an additional load;
. undermining of slope;
. lateral pressure exerted on cracks due to factors
freezing.
(ii) Factors that cause reduced sllear strength .c acteristic of some soil particles like clay to swell and sh alternatively in wet and dry periods;
. rock structure such as faults, joints, bedding E . pore-pressure effects;
. drying and desiccation;
. loss of capillary action;
. crumbling soil structure that leads to reduced csion in soil.

According to Cooke and Doornkamp, the proces movement which follows planes is called shear. ApF forces are called stresses. Slope failure takes place as a CI of sheu stresses operational along straight or curved s planes.
Strain is the deformation caused by movement.It is the result of shear stresses it is called shear strain. amount of resistance offered by the slope to move] is measured by the strength of the slope. The compo of this which is directed against shear stresses is tel the shear strength.