Stress-strain and pore pressure behavior of micaceous sand in comparison with pure sand under K0 conditions

Mica particles are platy shaped with numerous intact mica flakes foliated over each other making them weaker along that plane and stronger in perpendicular direction creating inherent material anisotropy. The elastic/resilient property of individual mica particle makes the micaceous soil highly compressible. When sufficiently numerous platy mica particles interact with spherical sand particles, either regular arrangement of sand above mica (ordering) or irregular arrangement of sand below mica (bridging) occurs. These unique geometric arrangements of sand-mica particle orientation lead to larger void space in micaceous sand unlike sand-sand particle orientation leading to closest packing arrangement in pure sand. The resilient/rebound characteristics of mica particle along with bridging and ordering causes low densification of micaceous soil. Micaceous sand with such distinctive particle assemblies would exhibit peculiar shear behavior in comparison to pure sand under restricted lateral deformation. This paper evaluates the stress-strain and pore pressure response along with the stress path behavior of micaceous sand in comparison to pure sand under K<inf>0</inf> conditions. A series of strain controlled K<inf>0</inf> consolidated undrained triaxial compression (CK<inf>0</inf>UC) tests were performed on pure sand (PS) & micaceous sand (MS) specimens. The K<inf>0</inf> consolidated specimens were sheared at strain rate of 0.1% per minute under undrained conditions. Strong influence of mica particles on stress-strain and pore pressure behavior was observed by comparing the response of micaceous sand & pure sand specimens. The failure of soil specimen was observed at larger strain levels for micaceous sand as compared to pure sand. This behavior of micaceous sand could be observed due to the collapsible geometric arrangement of sand particles with larger void space due to bridging and ordering along with platy mica particle.