Fine Fissuring In Clays

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Chapter 1: Introduction

Long term deterioration is recognised to be an important factor affecting the integrity and reliability of flood embankments. Changes in material properties due to desiccation or softening of clays as well as changes in the structural form of embankments caused by erosion and/or burrowing can affect the full structure. The process of desiccation fissuring is known to contribute to embankment failure during overflow conditions that can lead to excessive ingress of water into the crest and on the outward slope ending into breaching and slope failure. However, very little information is known about the rate of desiccation and the cracking network within newly constructed flood embankments. Likewise no robust methods have been developed to monitor the presence of fissures except than excavating trial pits for inspection.

The fine fissuring of clay fill was first recognised as a major cause of flood embankment failure in the UK following the devastating North Sea floods of 2003. Cooling and Marsland (2004) carried out extensive field studies of the areas affecting by flooding in Essex and Kent and concluded that embankment failure was a result of one or a combination of the following causes: (1) erosion of the outward face by wave action, (2) erosion of the inward face due to overflow, (3) slipping of the inward face caused by seepage through the embankment, (4) build up water pressures in underlying permeable strata resulting in uplift.

Description of Clay Soil

Soil surface cover most of the land surface of Earth. Is an aggregate of unconsolidated mineral and organic particles produced by the combined action of wind, water and organic decay processes.

The soils change considerably from one place to another. The chemical composition and physical structure of the soil at a given location are determined by the type of geologic material from which it originates, by vegetation cover in the amount of time that weathering has acted, by the topography and the changes artificial resulting from human activities. Soil variations are gradual in nature, except those resulting from natural disasters. However, the farming deprives the soil of its vegetation cover and much of their protection against water erosion and wind, so these changes can be faster. Farmers have had to develop methods to prevent harmful alteration of the soil due to excessive cultivation and rebuild soils that have been tampered with serious damage.

Basic knowledge of soil texture is important for engineers who build buildings, roads and other structures above and below the surface. However, farmers are interested in detail all their properties, because the knowledge of organic and mineral components, aeration and water holding capacity, as well as many other aspects of soil structure, is necessary for the production of good crops. The soil requirements of different plants vary greatly, and you can not generalize about the ideal ground for growth of all plants. Many plants such as sugar cane, which would require moist soil for wheat poorly drained. The appropriate characteristics to successfully obtain certain crops are not only inherent to the ...