Characterization of highly variable rock weathering by using DPR

Abstract

The highly variable nature of the deeply weathered Porto granite has been posing significant challenges in the geotechnical design and some problems in the execution of foundations, deep excavations and tunneling, due to the nature of the rock mass which is extremely difficult to differentiate between the several class qualities. The identification of geotechnical patterns in weathered rock profiles from conventional borehole investigations is common and ideal, but rather time consuming. Drilling Parameter Recording (DPR) has been pointed out as a complementary alternative to this site investigation. A series of boreholes where both classical exploration techniques (including standard penetration tests on soil masses - with sampling to allow some lab tests - and rock quality monitoring by the analysis of coring, as well as some geophysics in both ambient) and drilling with recording systems, have been used to develop protocols between indices coming out from this most practical and efficient technique. This paper presents the preliminary results of the study developed in this geological and geotechnical ambient, by comparing the drilling parameters - both individual and compound, which may magnify specific contributions - with the conventional site investigation measurements This research, in a joint venture with the industry, aims to potentate this technique in order to become a reliable complementary alternative in mapping and characterizing these weathering profiles.