Contractance

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Contractance is the property of a granular medium to increase its density during shear stress . Contractance is thus a material property, analogous to dilatancy .

In soil mechanics , contracting material behavior is observed in loosely deposited sands . The density of the sand increases with shear stress. The density increases up to a critical density dependent on the hydrostatic effective pressure, which then remains constant with the shear travel for large shear deformations.

In the event of very rapid shearing forces, loosely stored and thus water-saturated sands that tend to contract can liquefy ( soil liquefaction ). The incompressible pore water combined with an obstructed outflow prevents the rock density from increasing . In addition, the individual grains lose contact with neighboring grains, which means a loss of strength. Liquefied sand cannot absorb shear stresses, which can cause major damage to structures.

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