foundation system of burj al arab

Hydroconsolidation of Loess Soil (Part-2)

We were discussing about hydroconsolidation of loess soil and behavior of montmorillonite, relevant to this topics. The montmorillonite swells when it gains water into its lattice structure and reverse when water is removed from it due to seasonal or other causes.

It has low internal friction and high plasticity when it is in moist state. Now a question may arise, under saturation montmorillonite swells, why does loess settle or collapse under saturation?

The answer is swelling behavior is valid when total swell mass has majority portion of clay (montmorillonite). But in loess there have little clay content that just coat silt particles and shows temporary cohesion resulting high strength before getting wet. 
Consolidation of loess soil results entire ground to collapse
When loess soil gains moisture, the bonds provided by clay content and also calcite (low content) becomes weak and dramatically reduce soil strength from its previous dry state.

So a localized collapse or consolidation is observed to undergo with a slight change in

-moisture content

-clay content

Thus, saturation of loess soil results consolidation of it under much lower stresses than that of dry. Thus in hydroconsolidation, loading is not only key factor for consolidation of soil, which is often less important contributor than moisture variation as this soil may collapse only under saturation even application of little or no loading.

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