Collapse behavior of sand

Abstract

Loose cohesionless materials can collapse during either static or dynamic loading, resulting in a rapid buildup of pore pressure and associated reduction in shear resistance. As the cohesionless material collapses, it rapidly looses resistance until the acting shear stress decreases to the available residual or steady-state strength. Specially designed stress-path testing has been performed on sand to investigate this collapse process. Results from this test program and previously published data show that a state boundary can be defined when a cohesionless material moves from peak to steady state along a constant void ratio stress path regardless of whether it is loaded drained or undrained. Further, it is demonstrated that the state boundary represents a surface in the effective mean normal stress–deviator stress–void ratio space. Hence, flow slides and liquefaction can be initiated when the stress path followed during either drained or undrained loading attempts to cross this state boundary surface. Key wordy : sand, collapse, liquefaction, stress path, state boundary, triaxial test.