The effects of weathering on the physical and mechanical properties of a granitic saprolite

Less research has been carried out on the changes induced by weathering to the mechanical properties of reconstituted and intact soils that originate from chemical decomposition of rocks (saprolites) than has been done for sedimentary soils. One-dimensional compression and triaxial tests were performed on reconstituted and intact specimens along a weathered profile to investigate the changes in their physical and mechanical properties. Some heterogeneity in the weathering tends to cloud the trends observed, but it was still clear that the grading varies the most, while the mineralogy changes less and the particle morphology is nearly unchanged. The gradient of the normal compression line is fairly constant with weathering, but reduces significantly at shallower depths. The gradient of the critical state line in the stress plane reduces with weathering, while its intercept in the volumetric plane has a more complex trend, but generally also reduces with decreasing depth. The value of the specific volume in situ increases with weathering and so the in situ state becomes closer to the critical state line. The effects of structure were quantified using a pseudo strength sensitivity defined by the location of the intact state boundary surface at the critical state. This parameter generally reduces with weathering and increases with depth.