Chapter 9 Peat hazards: compression and failure

Abstract

Peat is a highly compressible geological material whose time-dependent consolidation and rheological behaviour is determined by peat structure, degree of humification and hydraulic properties. This chapter reviews the engineering background to peat compression, describes the distribution of peat soils in the UK, provides examples of the hazards associated with compressible peat deposits and considers ways these hazards might be mitigated. Although some generalizations can be made about gross differences between broad peat types, no simple relationship exists between the magnitude and rate of compression of peat and loading. Based on examples described here, land failures resulting from peat compression are locally generated, but due to the sensitive nature of peat these can result in runaway failures that pose great risk. Understanding the geological hazards associated with compressible peat soils is challenging because peat is geotechnically highly variable and the mapped extent of peat in the UK is subject to considerable error due to inconsistencies in the definition of peat. Mitigating compression hazards in peat soils is therefore subject to considerable uncertainty; however, a combination of improved understanding of the properties of compressible peat, better mapping and land use zoning, and appropriate construction will help to mitigate risk.

Chapter 1 Introduction to Geological Hazards in the UK: Their Occurrence, Monitoring and Mitigation

“…1.6.4 Chapter 9: peat hazards: compression and failure (Warburton 2020) Peat is a low-density, highly compressible soil that occurs at the surface or may be buried at depth. Peat is essentially an organic, non-mineral soil resulting from the decay of organic matter.…”

Blanket bogs exhibit significant alterations to physical properties as a result of temporary track removal or abandonment

“…At present, there is little data beyond the work of McKendrick‐Smith (2016) on the physical impacts of mesh tracks on peatlands. Peat is known to have complex patterns of consolidation and rheologic behaviour (Kazemian et al, 2011; Mesri & Ajlouni, 2007; Mesri et al, 1997; Warburton, 2020) and can exhibit bilinear stress–strain patterns (Edil et al, 1993). The lack of understanding about responses of peatlands to temporary tracks leaves conservationists, regulators and landowners facing difficult decisions when creating vehicular access routes on ecologically and environmentally important peatland sites, which can lead to tensions and conflicts, including, on occasion, resort to legal process.…”