Organic and peat soils engineering

Peat and organic soils are extremely soft and unconsolidated surficial deposits constituting the subsurface of wetland systems. They may also be found stratified in other surficial deposits in areas that have undergone palaeo-environmental changes. These soils are geotechnically problematic due to their very high compressibility and very low shear strength. To compound this they are usually very difficult to access as the water table is often at, near or above the ground surface. Although generally conventional soil mechanics theory may be applied to these soils it, however, is found that important anomalies exist which require special consideration. These anomalies are presented in this book. From the perspective of engineering, the choice of construction method in areas underlain by peat deposits is a matter of finding optimal solutions between the economic and technical factors, available construction time, and the target performance standards. Avoidance of construction of fills over peat layers, replacement of surface peat layers by granular fill materials, stage-construction, use of light-weight fill (weight-credit construction), in situ improvements (preloading, stone and sand columns and vacuum consolidation) and piles are the various methods used in different countries in dealing with construction over peat soils. Geotextile and strip drains (paper or polyester) are often incorporated into construction to improve stability, improve construct ability, and accelerate construction. New developments in construction methods include lightweight geo-materials, thermal precompression, deep in situ chemical stabilization, and preload pier technologies. This book reviews both the currently available methods as well as those under development. Although there have been several books on the mechanics or engineering of soils, this book is believed to be the first for tropical organic soils and peat. It is hoped that this book is not only useful for the engineers, but also to the soils scientists, agriculturalists, environmentalists, as well as planners, essentially all those who are involved in peat land development.