Concept of critical void ratio used in estimating dynamic stability of sands

Some authors use the concept of critical void ratio of sands to describe sand behavior under dynamic load. This paper presents a new procedure of experimental determination of the critical void ratio of sands under consolidated undrained triaxial compression. At present, there is no technical possibility for determining the critical void ratio of sand under dynamic loads, particularly in shear zones. The mechanism of dynamic load is such that both pore pressure and effective stresses (indirect indicators of the change in the void ratio of sand under undrained conditions) change several times, even during one cycle. It is established that, because of dynamic loading, saturated sands of any density tend to the state of zero dynamic dilatancy when shear zones of constant thickness form in sands, where further strain accumulation is localized. The investigation into the state of zero dynamic dilatancy is fundamentally important for the estimation of the dynamic stability of sands.