Breakage critical state of gravels with different gradings. Part I: Experimental results

Grading and particle breakage have significant influence on mechanical properties of crushing geomaterials. A series of large-scale triaxial compression tests have been carried out to investigate the influence of grading and particle breakage on the stress-strain relationship, grading state index, critical state, and breakage index of coarse grains. The results confirm that the slope of critical state line (CSL) is a constant in the CSL stress plane and independent of initial grading, whereas, the location and slope of the CSL in the CSL deformation plane are strongly dependent on the initial grading. In addition, a hyperbolical function is used to capture the relationship between breakage index and input work for gravels with different initial gradings. A unified critical state surface considering the grading state index is established in three-dimensional CSL space for the gravels used in this study and also validated by the test data on other soils from literatures.