This paper presents the results of a study of the morphology of weathering profiles of some sandstones of Sunshine Coast, Southeast Queensland, Australia. Several cut slopes were analyzed in order to provide accurate knowledge of its morphological characteristics. From these, five outcrops were selected to a more detailed study focused on physical, geological, structural and geotechnical parameters, including several characteristics of the rock matrix and rock mass. Samples from the upper portion of the profiles, into the transition zone between rock and soil, were collected in order to determine physical indices, preparation and description of thin sections, description of macroscopic characteristics and point load tests. The results show that sandstones weathering profiles are relatively thin and the contacts between different material layers are sharp. A strong structural conditioning of weathering can be noted in all outcrops. A remarkable characteristic of the weathering profiles is the presence of stress relief joints parallel to bedding, which plays an important role in the differentiation of rock mass layers and weathering. Physical parameters, especially apparent porosity and density, have proved to be good indicators of weathering of rock matrix weathering.


The importance of the study of weathering profiles is mainly related to the presence of transitional weathered materials between the rock and the soil, which present different geotechnical parameters and, as a consequence, different geotechnical behavior. The presence of these weathering profiles at a geotechnical work site such as cut slopes, foundations and open and underground excavations, drives geotechnical stability, as weathering produces material with extremely different mechanical parameters [1, 2, 3, 4 and 5]. Add to this scenario is the presence of structural discontinuities that, besides influencing underground water circulation and hence weathering, introduces great variations in mechanical behavior. This context presents an important and complex geotechnical instability mechanism of rock masses that has been responsible for many geotechnical problems under different weathering (climatic) conditions.

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