Influence of load on shrinkage behavior of peat soils

Abstract

The shrinkage of the peat soils that accompanies the soil moisture changes is an important feature of such soils and has strong influence on their physical attributes and soil water management. The relationships between soil moisture and volume are often described using shrinkage characteristic curves by relating void ratio (volume of voids per unit volume of solids) to moisture ratio (volume of water per volume of solids). For conversion of soil volume changes into cracks volume and subsidence, a dimensionless shrinkage geometry factor is used. The paper presents results of volumetric shrinkage behavior and the geometry factor at various loads in sedge and alder peat soils. The measurements were conducted on undisturbed soil samples without applying a load and with loads corresponding to field overburden. The shape of the shrinkage characteristics of such soils were completely different from those of clay soils. The application of loads did not significantly influence the shrinkage characteristics curve. The applied load strongly influenced on relationship between shrinkage geometry factor and the moisture ratio, showing higher values of subsidence and lower values of crack volume in comparison with unloaded conditions.

Shrinkage processes of a drained riparian peatland with subsidence morphology

“…Therefore, the peat layers below the phreatic zone have to bear an increased weight, as the weight of the overlying material is transferred from the liquid to the peat fibres, causing compression (Sauerbrey and Zeitz 1999). Additionally, higher desiccation intensities due to the lowering of the groundwater table and less capillary rise occur, leading to shrinkage processes (Brandyk et al 2002;McLay et al 1992;Oleszczuk et al 2003;Schwärzel et al 2002). (2) Typical mineralisation rates of drained fen peats in Northern Germany reach up to 1 cm year −1 (Göttlich 1990).…”

Subsidence of organic dredged sediments in an upland deposit in Wormer- en Jisperveld: North Holland, the Netherlands

“…Land subsidence in peatlands is a consequence of drainage that results in shrinkage due to the loss of volume occupied by the water and rearrangement of the particles when the water is removed (Oleszczuk et al 2003), and organic matter oxidation (Sanei et al 2005). The oxidation of the organic matter can result in humification or mineralization.…”

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). …”

“…Land subsidence in these areas is, in addition to long term geological effects, mostly a consequence of anthropogenic interference such as drainage which results in shrinkage due to the loss of volume occupied by the water and rearrangement of the particles (Oleszczuk et al 2003), and in organic matter oxidation (Sanei et al 2005). There are studies with contrasting results regarding the individual contribution of shrinkage and organic matter oxidation to the total land subsidence: some report that the high subsidence rates observed in the layer above the groundwater level is mostly oxidation of organic matter (Dawson et al 2010, Hoogland et al 2012, Schothorst 1977; others relate land subsidence mainly with shrinkage (Teatini et al 2011); and other studies concluded that the contribution of oxidation of organic matter and shrinkage is variable in time (Hooijer et al 2012, Pronger et al 2014, van Asselen 2011.…”

“…Land subsidence in these type of peatlands is mainly a consequence of drainage that results in shrinkage due to the loss of volume occupied by the water and rearrangement of the particles when the water is removed (Oleszczuk et al 2003), and organic matter oxidation (Sanei et al 2005). The oxidation of the organic matter can result in humification or mineralization.…”