Sareh Mahmoudi - postgraduate Student of Soil Mechanics and Foundation
Manoochehr Latifi - Assistant professor of Civil Engineering
Abbas Ghalandarzadeh - Assistant professor of Civil Engineering

A state – boundary define a boundary in stress-void – ratio space above which a state for a particular materials is not admissible . Results from previously published demonstrate that any attempt to cross this boundary for a very loose saturated sand by a constant deviator stress path results in collapse and flow liquefaction. An experimental study investigating the existence of the state boundary for Firrozkooh sand is presented. It is shown that post-peak portion of undrained stress paths travels along the state-boundary and the state-boundary can be approximated by a straight line. The slope of this straight line appears to stay constant for very loose sand.

sand , collapse , liquefaction , stress path , state - boundary , triaxial test