Soil Response during Globally Drained and Undrained Freeze-Thaw Cycles under Deviatoric Loading

摘要

Sediments experience shear and volumetric strains during freeze-thaw cycles. Measurements during globally drained and undrained cycles under constant deviatoric stresses show that the asymptotic shear and volumetric response vary with sediment type and drainage conditions. In particular, the sediment response is intimately related to the ice pore habit that results from effective stress and the ice capillary pressure σ_z~'/Δu_(iw). Pore-invasive ice formation in coarse-grained soils may trigger some contraction during the first freeze-thaw cycle, even in sands denser than the critical state. Grain-displacive ice growth in fine-grained soils causes cryogenic consolidation of the surrounding sediment; subsequent melting of the segregated ice lenses yields a high increase in pore water pressure during undrained thawing, a pronounced volume contraction under drained conditions, and preferential shear deformation along melting ice lenses in either case. Both dilative sand and normally consolidated (NC) clay specimens subjected to deviatoric loading exhibit unceasing vertical strain accumulation (i.e., ratcheting) during freeze-thaw cycles; the void ratio evolves toward asymptotic values in all cases. The freezing rate relative to the pressure diffusion rate Π = D_T/C_v regulates drainage conditions during freeze-thaw cycles; globally drained freezing and thawing are anticipated in coarse-grained sediments.