Morphological and physical-mechanical characterization of a syenogranite weathering profile developed on tropical climate

Abstract

In regions of tropical climate weathering processes tend to be very active in engineering time in terms of range and effectives, producing alteration mantles that are often deep and well developed when compared to weathering profiles similar rocks developed on temperate climate. In the municipality of Cachoeiro de Itapemirim, Southeastern Brazil there are many syenogranite weathering profiles on ornamental stone quarries, in which it is possible to observe the effects of weathering at different levels. Considering the importance of knowing the behaviour of these different transition materials in civil and mining engineering design, it becomes relevant to characterize their morphology and physical properties. Among the weathering profiles visited, the focus of this study is a weathering profile that presented the higher heterogeneity, with more alteration levels and better accessibility for sample collection, in situ tests and morphology characterization and description. Samples were collected and the following lab tests were performed for the physical-mechanical characterization: physical indexes (apparent dry density, apparent porosity, absorption capacity and void index), P-wave velocity, Schmidt hammer rebound value and point load index. The preliminary results indicate there is a strong structural control in the development of weathering and that shape of the relief contribute to accelerate the processes of alteration and quick dissection of the relief, avoiding the formation of a profile with more gradual transitions between different weathering levels. As for the physical-mechanical characteristics, a considerable maximum loss of resistance, about 99% in point load index, and maximum increase of the porosity, about 97 %, is observed with the increase on the degree of weathering, being these two parameters more sensitive for the studied granite.