Engineering properties of peat and organic soils - Geotechnics of Organic Soils and Peat - page 45

Figure 3.2 SEM images of fibrous peat (H2-H3) from Malaysia ( after Kazemian et al ., 2011).
or non-woody) or coarse (woody). Organic matter that does not have an identifiable
fibre shape is finer in size than 0.15mm and designated as amorphous-granular matter.
It is also referred as peat humus .
3.4 FABRIC OR STRUCTURE
Fabric or microstructure refers to the morphology and spatial arrangement of the con-
stituent soil elements. Macro fabric or macrostructure refers to those features visible
to the naked eye, whereas micro fabric or microstructure involves much smaller fea-
tures at the particle or fibre level. Radforth, in Muskeg Engineering Handbook (1969)
provides a classification of peat structure based on two structural elements: fibres and
granules. In this system, peat structure is classified into three predominant character-
istics: (1) amorphous granular (dominated by highly disintegrated formless botanical
tissues), (2) fine fibrous (dominated by an open framework of highly preserved fos-
silized plant remnants), and (3) coarse fibrous with 17 categories further subdividing
these characteristics. The fibres of peat consist of cellular structures giving rise to a
two-level structure involving macro and micro pores, i.e. those between and within
fibres, respectively (Dhowian and Edil, 1980).
It is the structure of peat, in its various aspects, that affects the engineering
behaviour ( Muskeg Engineering Handbook , 1969; Dhowian and Edil, 1980). There
has been virtually no research to correlate different structural types and their physical
and engineering properties. However, MacFarlane and Radford ( Muskeg Engineer-
ing Handbook , 1969) suggest that the engineering behaviour of peat can be grouped
broadly into fibrous and amorphous granular. This suggestion is supported by other
investigators (Dhowian and Edil, 1980). The two-level structure described by Adams
(1965) may be used to describe the unusual compression behaviour of fibrous peat.
Scanning Electron Microscopy (SEM) images can be used for a visual appreciation
of the soil microstructure. Figure 3.2 shows typical SEM image of fibrous peat from
Malaysia. Images such as those shown in Figure 3.2 indicate that the peat is extremely