i).​Explain the critical height in Clay (Cohesive soils)? Give equations for earth pressure for active and passive conditions for soils with c > 0 and ф > 0 i.e Cohesive soils.(ii)​Explain is it good...

i).​Explain the critical height in Clay (Cohesive soils)? Give equations for earth pressure for active and passive conditions for soils with c > 0 and ф > 0 i.e Cohesive soils. (ii)​Explain is it good or bad to backfill retaining wall with Clay soil Vs Sandy Soil. Support your answer with valid arguments.