Methods of Stability analysis of slope(Geotech)

Hi here is a  brief introduction to the stability analysis of the slopes.
There are following methods of stability analysis:

• (A)Slip circle method or Swedish circle method or Method of Slices:

This method assumes the surface of sliding is an arc of a circle. Soil is either purely cohesive or it will be a cohesive and frictional soil. So, analysis can be done separately as below:

• Analysis of purely cohesive soils:

An arc of a circle is assumed as the failure plane and the weight of the circular arc wedge provides a disturbing moment. This disturbing moment is stabilized by the stabilizing moment developed due to the presence of the cohesion along the arc surface.
These two moments are equated to get the limiting values. The ratio of the resisting moment to the stabilizing moment gives us the Factor of safety.

• Cohesive and frictional soils:

In such soil again a circular arc is assumed to be a failure wedge and the weight of the wedge is resolved into tangential and normal directions. The tangential weight will provide us with the disturbing moment about the center of rotation and the normal force will provide us the frictional resistance which along with the cohesion force will produce the stabilizing moment.

• (B) Friction circle method

This method is applicable to cohesive as well as frictional soils and assumes the failure surface as an arc of a circle.  There is a small circle known as friction circle. 

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