Compressibility Characteristics of Fibrous Tropical Peat ... - Ejge.com

Vol. 14, Bund. C 2
was derived; and it is this latter material that is defined as the soil humus have defined soil
organic matter by Russell (1952).
To a geotechnical engineer, all soils with organic content of greater than 20% is known as organic
soil. Peat soil is an organic soil with organic content of more than 75% (Huat, 2004). This classification
is partly the same as ASTM D 2487 classification; a soil with organic content less than
75% (or ash content more than 25%) as muck or organic soil, while a soil with organic content
higher than 75% (or ash content less than 25%) as a peat. For geotechnical purposes, peat degree
of decomposition or humification system of Von Post (1922) is often reduced to 3 classes
(Magnan, 1980; ASTM Standard D 5715): I. Fibric or fibrous (least decomposed). II. Hemic or
semi-fibrous (intermediate decomposed). III. Sapric or amorphous (most decomposed).
The amorphous peat particles, in which the cell structure is still visible, are the product of
biochemical decomposition and breakdown of fibrous peats and other plant remains. Amorphous
peat deposits are more likely to include a significant amount of inorganic matter. As compared to
fibrous peat deposits, the amorphous peat fabric is likely to exist at lower void ratios and to
display lower permeability anisotropy, lower compressibility, lower friction angle, and higher
coefficient of earth pressure at rest (Edil and Wang, 2000).
Fibrous peat is peat with high organic and fiber content with low degree of humification. The
behavior of fibrous peat is different from mineral soil because of different phase properties and
microstructure (Edil, 2003). Landva and Pheeney (1980), Landva and La Rochelle (1983) described
fibrous peat particles consist of fragments of long stems, thin leaves, rootlets, cell walls, and
fibers, often are quite large. Stem diameters of 20 to 500µm, leaf thicknesses of 10 to 15 µm, and
width and length of 100 to 1,200 µm are common. Scanning electron micro-photographs (SEMs)
of James Bay peat in Figure 1(a), (b) illustrate hollow perforated cellular structures and a network
of fibrous elements in vertical and horizontal section (Mesri and Ajlouni, 2007).
a
b
Figure 1: Scanning electron microphotograph of (a) vertical section; (b) horizontal section (Mesri
and Ajlouni, 2007)
Peat is found in all part of the world except in deserts and the arctic regions. The most extensive
areas are located in the northern hemisphere. It is estimated that there are about 1 billion acres of
peat land in the world or about 4.5% of total land areas. In United State; peat is found in 42 states
with a total area of 50 million hectares, Canada has 110 million hectares and former USSR 150
million hectares. In Japan peat is widely distributed throughout Hokkaido, which is the northern