Permeability and stiffness of sands at very low effective stresses

Abstract

de la rigidité E 0 , et de la perméabilité k avec la tension efficace. On y démontre qu'alors que la perméabilité augmente sensiblement en présence de tensions efficaces extrêmement basses, la diminution simultanée de la rigidité mesurée engendre une réduction du coefficient de consolidation, et, de là, une augmentation du temps pendant lequel le sol reste liquéfié.

Towards a complete model of soil liquefaction: the importance of fluid flow and grain motion

“…After the soil has fully liquefied, we may have significant changes in the fluid dynamics: for example, Darcy's law with a constant permeability will not hold in a fluidized bed. Several authors have pointed out that the permeability required to satisfy Darcy's law changes dramatically when effective stresses drop near zero [17,18].…”

Post-liquefaction reconsolidation of sand

“…In this paper, the proposed method was assessed versus centrifuge experiments performed using Hostun sand. The data presented in [19], recorded during fluidization tests of Hostun sand, show that the increase in hydraulic conductivity is less than 20% and only occurs for effective stresses below 0.1 kPa. In order to factor this dependence on effective stress, equation (3.2) was written as…”

“…A drop occurred even above the solidification front. This behaviour was due to the very high sensitivity of hydraulic conductivity at very low effective stresses [19]. A front related to hydraulic conductivity advanced upwards, faster that the solidification front.…”

“…The assumption of infinite hydraulic conductivity at zero effective stress is common (e.g. [19,21]). However, it is based on extrapolation of power laws developed for higher effective stresses.…”

“…The use of such values is typically justified by claiming that hydraulic conductivity increases due to the loss of contacts between sand grains. However, fluidization tests show that while such an increase is possible, it is not of significance unless effective stress reaches values below 0.1 kPa [19], a tiny fraction of the effective stress range expected for a typical reconsolidation case. An overall increase in hydraulic conductivity is not realistic.…”