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.
SummaryThe author and his colleagues believe that the surgical technique used constructing a tracheostomy can have a profound effect on the safety and care of patients in the intensive care unit particularly in the first few days after the operation. The Björk procedure is commended to the surgeons.
The author expresses the doubts that many have with regard to the efficacy of the present methods of describing rock mass weathering. As an alternative to these methods the author recommends the use of a ratings system which classifies weathering in terms of engineering significance. The author also recognizes that all ratings systems which are successful have been developed over the years as a consequence of the experience of many users, but proposes, as a starting point for further discussion, a ratings system developed during engineering geological fieldwork in Spain.
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