The slope is to be checked for drained condition to design the stability for long term and short term in undrained conditions. So, i recommend to you to check the stability of highway slope both for long and short term response and see the FOS is in acceptable limit in both the conditions of slope.

Both drained and undrained cases should be checked for FOS.

The choice of the type of analysis (short term or undrained) or (long-term or drained) depends on the type of soil. If the soil is normally consolidated clay, the short-term (undrained) analysis governs due to development of positive pore water pressure. If the soil is overconsolidated clay, the long-term (drained) analysis governs due to development of negative pore water pressure in the short-term.

Dear all,

Greetings!

I highly appreciate your valuable comments & shall carry out my analysis accordingly.

Once again, Thank you so much.

Regards,

Sumit

Generally, for long term stability of overconsolidated material one should perform analysis with drained post-peak strength parameters (post-rupture strength).

For cut slopes, as opposed to embankments, FoS value in general decreases over time due to pore-pressure equilibration after excavation.

In the case of unsaturated materials the minimal FoS could be reached at some point after excavation.

Regards,

Zoran

Thank you for your comment sir Zoran.

Dear all,

The previous answers clarify the problem. In any case you should check if modifications to the water regime are expected (for example rain), what could also influence your decision.

Regards,

António Topa Gomes

The type of analysis depends on the type of soils, on groundwater flows and hydrogeological conditions.

For granular soils (i.e sand or gravel), the slope must be checked only in drained conditions.

For cohesive soils (i.e.clay and silts), there are two possibility. If the soils are dry the slope must be checked only in drained conditions. If the soils are saturated or with groundwater flow the slope must be checked in both undrained and drained conditions.

Thank you Marco-sir