A method for characterizing desiccation-induced consolidation and permeability loss of organic soils

Abstract

A new method was developed to measure soil consolidation by capillary suction in organic soils. This method differs from previous methods of measuring soil consolidation in that no external load is utilized and only the forces generated via capillary suction consolidate the soil matrix. This limits the degree of consolidation that can occur, but gives a more realistic ecological perspective on the response of organic soils to desiccation in the field. This new method combines the principles behind a traditional triaxial cell (for measurements of volume change), a pressure plate apparatus, (to facilitate drainage by capillary suction), and the permeameter, (to measure saturated hydraulic conductivity) and allows for simultaneous desaturation of the soil while monitoring desiccation-induced volume change in the soil. This method also enables detection of historic limit of dryness. The historic limit of dryness is a novel concept that is unique to soils that have never experienced drying since their formation. It is fundamentally equivalent to the precompression stress of externally loaded soils. This method is particularly important for forecasting structural and hydrologic changes that may occur in soils that were formed in very wet regimes (e.g., wet meadows at the foot of persistent snowpacks and permafrost peats) as they respond to a changing climate.

ClimGrassHydro - Ecohydrology of mountain grasslands under global change: mechanisms and consequences - Final project report

“…16 From a soil physical perspective, extreme drying can physically alter the structure of soil material such that flow and storage properties are irreversibly altered. [19][20][21] These changes can be manifested through crack formation, 20 increases in macroporosity, 21 lowered storage capacity, 18 and greater preferential flow. 22 Alternatively, it has been suggested that CO2 enrichment may drive increases in root exudation and mycorrhizae activity which convey greater soil aggregate stability 23 and more water retention in finer pores.…”

Lift up of Lowlands : beneficial use of dredged sediments to reverse land subsidence

“…Shrinkage refers to the loss of volume occupied by the water (through vertical and horizontal drainage and evapotranspiration) and rearrangement of the particles (including compaction) when the water is removed (Arnold & Ghezzehei 2015, Ilnicki 2002, Oleszczuk et al 2003). …”