Target GATE & ESE 2022 (Geotechnical Engineering)

 Do You Know?

👉Bridge abutments are restrained by deck slab, so earth pressure acting on abutment is earth pressure at-rest.

👉For initial stability ⇒ Undrained test is considered. To be on more safer side saturated clay is taken as unconsolidated.

👉 Unconfined compression test is a special case of triaxial test in which minor principal stress (Cell pressure=0) is zero. Mohr-circle passes through origin.

👉 Consolidated means drainage is allowed in first stage (Cell pressure stage or confining stage) and drained means drainage is allowed in second stage (Deviator stage/shear stage). In CD test drainage is allowed (drainage valve is open) in both the stages hence pore water pressure is zero in both stages.

👉Point above Mohr's envelope indicates that shear stress is more than shear strength of soil which is an imaginary condition.

👉 For Initial Stability(Short term stability) →  UU test

      For Long term stability →CD test

👉Liquefaction is generally associated with sandy soil and not possible in normal clays due to cohesion between particles (shear strength not equal to zero) but highly sensitive clay may undergo liquefaction under vibration.