Mineralogy, fabric properties and classification of weathered granites in Hong Kong

Deeply weathered granitic rocks are encountered in many engineering works in Hong Kong. To date, the engineering properties and behaviour of these granites, and the soils formed from them, have been poorly related to their basic mineralogical and fabric characteristics. In this paper, a model for weathering of granites is established and, based on this, modifications are proposed to the material and mass weathering schemes commonly adopted in Hong Kong for the characterization of weathered granite in engineering uses. A number of chemical indices have been found to be good indicators of chemical weathering whereas the micro-petrographic indices can be used to characterize most fabric elements of weathered granites. Care in the testing and interpretation of test results is required for soils of granitic origin because of specific mineralogy and fabric that is developed.