While using PM4 models the effective stress calculation should be based on vu undrained or by using biot effective stress calculations as Pore pressure measurements and liquefaction criteria are the major concern?

if using 'Drained' for Drainage type in General and using PM4Sand in Mechanical tab as user defined, no pore pressures are generated in dynamic phase. Should I use 'undrained A' even for sand type material when using PM4 sand?

On using PM4silt for clay and using Undrained A and for sandy soils (PM4sand) Undrained A.is it correct to use this combination while studying for liquefaction analysis?

Why liquefied points are observed in soil while using advanced constitutive models PM4sand and PM4silts before seismic loading? The liquefied points were observed in static phase only