Sulphate attack and ettringite formation in the lime and cement stabilized marine clays

Definitions of weathering are examined and a definition of weathering for geotechnical purposes is proposed. Weathering is achieved by weathering processes, which depend upon the nature of the new environment to which the geological materials are introduced. Weathering processes are reviewed with particular reference to examples from engineering practice. The weathering product, the modified geological material and mass, is a consequence of the interaction of the weathering processes and the geological materials and mass on which the weathering processes act. Modes of weathering of particular rock types are reviewed. The paper concludes with a discussion of classification policy, recommending simplification.

Weathering and weathering processes

Recent studies of weathering in deserts (e.g. Goudie 1989, Cooke et al. 1993) have given detailed reviews of the mechanisms considered to operate and the landforms with which they are generally associated. Invariably such reviews — especially if orientated towards students — deal primarily with the perceived certainties of our knowledge. In reality, however, weathering studies are more characterized by uncertainties and gaps in knowledge. Weathering research is thus not a question of what we know about desert weathering, but what we do not know; those points we secretly hope will not be raised in lectures or paper presentations. This chapter will therefore concentrate upon some of the less certain issues in weathering studies. The aim is not to be exhaustive or comprehensive, but hopefully to question some traditionally held views and stimulate future research.

Weathering Processes and Forms

Expansive characteristics of gypsiferous/anhydritic soil formations

Increasing the utilization of urban soil usage brings along very important problems to be addressed at the international level regarding the use of sulfate bearing soils as construction materials. After briefly exploring current research perspective, this paper captures the current state of the art in the field of sulfate bearing soils used as construction materials through a detailed discussion of different studies that pave the way to the possible treatment of such soils to be used in road construction. Additionally, the purpose of this paper is to acquaint geotechnical and pavement engineers with the present state of the art of the physical and chemical properties of gypsum and hence its effect on the subgrade soil performance. On the other hand, this paper discussed an opposite action in which some researchers have mixed recycled waste gypsum components with soil in order to stabilize it. In other words, a number of open research issues are highlighted with the intension of inspiring new conditions and developments in stabilizing problematic gypsiferous soil as well as adding gypsum to stabilize non gypsiferous soils of weak performance.

Review on the Effect of Gypsum Content on Soil Behavior

Summary The arid and extremely arid areas of the Middle East are outlined, and the past and present climatic regimes within these areas considered and related to the existing rock and soil conditions. A system of classification of the ground into four simple zones based on their desert characteristics and the natural processes operating within the zone is described. The general engineering character of each zone is discussed and particular problems highlighted. Zone I is the mountainous areas, zone II the large gravel fans bounding mountains, zone III the alluvial plains beyond the fans, and zone IV the central base level plains between mountains or adjacent to coasts. The great majority of desert soils are granular and their engineering behaviour is directly related to their grading characteristics. Flooding is an important hazard in the fans and alluvial plains, while in the base level plains high water tables are of major importance. Ground conditions of significance in deserts, which do not generally occur elsewhere include aggressive salty ground, wind blown sands and silts, and hard and soft duricrusts. These and certain other ground conditions are described.

P. G. Fookes

Papers

Middle East—Inherent Ground Problems