The effect of weathering on the variation of geotechnical properties of a granitic rock from Chile

The effect of rock weathering on geotechnical parameters can become substantial in geotechnical design. The weathering degree WD has been normally divided in five levels from fresh rock to completely weathered rock. In this study, the above five WDs are adopted to analyse the variation of several regularly used geotechnical properties. To that aim, a series of laboratory tests to a Chilean granitic rock in different stages of weathering was carried out. The results of the tests have been analysed by normalising each geotechnical parameter respect to the value obtained for slightly weathered samples instead of the fresh rock samples, which is usually adopted. In this way, it was found that the results of unconfined compressive strength UCS reduces steadily and considerably with each WD, which has been previously reported. Conversely, the modulus of deformation and P-wave velocity tend to stabilise the rate of reduction for highly and completely weathered rock samples, which does not agree with the trend and higher rate reductions found by other authors. This stabilisation reduction rate with WD was also found for compaction density, friction angle and Poisson's ratio.