Effect of Water Content on Shear Strength Behaviour of Micaceous Kutch Soil

Abstract

Micaceous soils are generally known for their high compressibility and low compacted density behavior. Mica flakes in soils are usually small and have fine sand and silt sizes. Mica particles have an influence on the compaction properties of soil due to their platy shape, ability to split into very thin flakes and the inter-space within the thin flakes. The mica flakes also impart resilience to the soil, which makes it difficult to compact. The spring nature of mica flakes helps them to recover their shape, when the stress is removed. In micaceous soils, a mica particle may simply replace an individual granular particle or fill a void, but as the quantity of mica increases, there is a corresponding increase in void spaces. Individual mica particles are capable of spanning over voids instead of filling them. If the mica flakes are sufficiently numerous to interact, the bridging phenomenon is further augmented. If mica content in soil is more than 10%, it has strong impact on compressibility, compressive strength and volume stability of micaceous soil. Some research has been performed on mica-sand mix to evaluate the effect of mica on geotechnical behavior of mix. In the current research, effect of water content on shear strength behavior of naturally available micaceous silty soil (Kutch, Gujarat) has been studied. The resilience behavior of mica particles and the presence of water molecules in the inter-space of their thin flakes were studied to understand the variation in shear strength behavior of micaceous Kutch soil (14% mica) due to the change in its water content.A series of shear strength tests were performed on micaceous Kutch soil at different water content varying from 0% to 23.5%. A series of XRD, SEM and AFM tests were also performed on Kutch soil to determine the mica content and understand the size, shape and geometric arrangement of particles (mica, silt, sand) within the soil mass. Micaceous silty soil samples were collected at 4 m depth near Dhori site, located in Kutch region (Gujarat); which had experienced severe liquefaction during Bhuj Earthquake 2001. The research can be used to understand the effect of mica on liquefaction behavior of micaceous soils.