Bond Yield Characteristics of Undisturbed Completely Decomposed Granite

To investigate the bond yield characteristics of undisturbed completely decomposed granite (CDG) which is widely distributed in Southern China, a series of conventional drained tests were conducted. From the test data, some insights are obtained as follows: for undisturbed CDG soils, the bond yield point during shearing could be identified on the curve of the normalized tangential stiffness Etan/p′ versus axial strain on log-log scale. The consolidation pressure P0′ has a significant influence on the bond yield characteristics of undisturbed CDG during shearing, the bonds inside undisturbed CDG tend to be damaged relatively more seriously as P0′ is higher, accordingly the initial normalized stiffness Eitan/p′ will be smaller at the beginning of the shearing process, and the axial strain at the bond yield point will also be smaller. Once consolidation pressure P0′ excesses a critical value such as 475 kPa for this studied CDG, the bonds inside soil will be damaged totally at the consolidation compression stage. In this case, there will be no bond yield occurring during shearing and the Etan/p′-εa curves will coincide with the ones of reconstituted CDG soil. For reconstituted soils, no bond yielding was observed during shearing; the Etan/p′-εa curves are tightly consistent with no dependence of the value of P0′