Very deep weathering and related landslides
Published:January 01, 2010
Some huge landslides have occurred in deeply weathered rock, but most geologists and engineers do not appreciate the great depths that weathering can attain. Rocks can be weathered to depths of hundreds of metres, often in a very irregular manner. Fresh rock is converted to weathered rock called saprolite by isometric chemical alteration. Some saprolite is later eroded, and fresh rock appears in the landscape in distinctive landforms. This erosion of an irregularly weathered landscape is called stripping (meaning the stripping of saprolite from fresh rock). The age of the weathering may be measured in geological periods, as can the age of stripping, and may be related to past climate different from that of today. Deep weathering occurs basically by hydrolysis, which requires groundwater. Slope failure in saprolite depends on the engineering property of the material, and its relation to bedrock and corestones, and relationship to degree of weathering of adjacent saprolite. This paper emphasizes the deep weathering phenomenon itself, but a few examples are given to illustrate the variety of landslides in deeply weathered material.
Figures & Tables
Weathering as a Predisposing Factor to Slope Movements
This volume is intended to provide an up-to-date overview of the approaches, methodologies and techniques devoted to better understanding of the weathering conditions of rock masses on slopes. According to the local conditions, a variety of slope movements may take place and involve weathered rock masses. Shallow and rapid soil slips evolving to debris flows are probably the most common type of slope movement. At the same time, deep-seated, intermittent landslides can also affect large volumes of weathered rocks and soils. Despite the high frequency of landslides in weathered materials, and the damage and casualties they repeatedly cause, little is known about the relationship between weathering and slope movements. This book presents worldwide case studies, where a variety of geological and geomorphological settings are discussed. The content is divided into three sections: the first is devoted to broad aspects of the weathering/landslide processes; the second and third sections include papers dealing with igneous/metamorphic and sedimentary weathered rocks, respectively.