Dear Mr.Pankaj,

The depth of failure surface in slope is mainly depends the properties of soils and its thickness. In case of the slope in homogeneous soil conditions, the depth of failure surface is the height of slope and the bottom soil is stiffer than top soil. In non homogeneous soil, it depends purely on the type of soil and its thickness. ok all the best in your research..

You can follow either Limit Equilibrium Method (LEM) or Finite element method (FEM).

If you use LEM, you can calculate the depth of failure surface for a given factor of safety and soil parameters.

If you use FEM (Griffiths and Lane, 1999), then model the slope in accordance with the field conditions and given soil parameters. If you draw the contour for equivalent plastic strain, you can easily find out the failure surface and its depth from ground level.

Please see this link:

https://www.slideshare.net/samirsinhparmar/stability-of-slopes

Karthigeyan . S , Md. Mahmud Sazzad and Mohannad Husain Al-Sherrawi

Thank you sir for your response.