Introduction - Geotechnics of Organic Soils and Peat - page 10

Figure 1.12 Distribution of peat land in Malaysia ( after Leete, 2006).

alluvial geomorphology they are often elongated and irregular, rather than having the
ideal round bog shape. The depth of the peat is generally shallower near the coast
and increases inland, locally exceeding more than 20 m. Water plays a fundamental
role in the development and maintenance of tropical peat. A balance of rainfall and
evapotranspiration is critical to their sustainability. Rainfall and surface topography
regulate the overall hydrological characteristics of peat land. Peat land is also generally
known as wetland or peat swamp because of its water table, which is close to or above
the peat surface throughout the year and fluctuates with the intensity and frequency of
rainfall. Chapter 2 describes in further detail the various types of peat land and their
mode of deposition. The distribution of peat land in Malaysia is shown in Figure 1.12.
Peat or organic soils may also occur as deposits buried underground and covered
with inorganic alluvial soils. These are often difficult to detect, and can be a source
of large differential settlements. Organic deposits may also be mixed with inorganic
soils, such as silt and clay, producing soils not as bad as peat but worse than inorganic
deposits.

1.3 ENGINEERING IN PEAT LAND

Peat has certain characteristics that sets it apart from most mineral soils and requires
special considerations for construction over them. These special characteristics include:

1. High natural moisture content (up to 1500%).
2. High compressibility, including significant secondary and tertiary compression.
3. Low shear strength (typically S u = 5-20 kPa).