Some engineering aspects of rock weathering with field examples from Dartmoor and elsewhere

TLDR

Weathering and weatherability have been defined and classified for engineering, with mechanical changes in intact and discontinuous rock examined through field and laboratory tests. The study proposes classification schemes for rock quality to aid mapping and core logging. Fieldwork and laboratory tests on Dartmoor rocks—including granite, dolerite, limestone, and mudstone—were used to classify weathering, measure strength and porosity, and analyze geometrical weathering patterns in folds and faults. Results reveal that strength and fracture spacing decline with weathering, early stages show increased fracture density, later stages exhibit rapid chemical decay, and the climatic implications of weathering remain unclear.

Abstract

Summary Weathering and weatherability have been defined and a general scheme of weathering classification has been developed for engineering. Fundamental mechanical changes in behaviour due to weathering are considered for both intact rock and discontinuous rock, and a brief study is made of available field and laboratory tests to assess weathering and weatherability. From this, suggestions are made for classification schemes designating rock quality for mapping and core logging. The results of fieldwork and laboratory studies on weathered rocks mainly from the Dart-moor area, S.W. England, are given. Several different rock types, including granite, dolerite, limestone and mudstone, have been classified on the weathering scale, tested in the field by point loading and Schmidt hammer, and laboratory determinations of strength and porosity made. The results show clear trends of decreasing strength and fracture spacing with increased weathering and general conclusions and observations on engineering weathering classifications have been drawn. In early stages of weathering it appears that there is a general increase of fractures per unit volume and in later stages of weathering there is a rapid increase in chemical decay. In addition, geometrical distributions of weathering in fold and fault situations have been examined. The full implications of Tertiary warm climate weathering and Quaternary cold climate weathering are not yet clear.