An experimental investigation on the secondary compression of unsaturated GMZ01 bentonite

Abstract The secondary compression behavior of compacted GMZ01 bentonite was experimentally investigated by conducting a series of suction-controlled high-pressure oedometer tests. GMZ01 bentonite powder was first exposed to suction controlled conditions at 110 MPa and then statically compacted to a dry density of 1.70 g/cm 3 . Then, the compacted samples were hydrated to designed suctions using the vapor equilibrium technique and finally submitted to multi-staged loading oedometer tests. Corresponding results were presented in terms of stress–strain-time curves. Based on the test results, the incremental compression index C c ∗ and secondary compression index C α were defined. Relationships between C c ∗ , C α , vertical stress and suction were analyzed. It is observed that both C c ∗ and C α increase linearly with increasing vertical stress, which is different from the convex relationship reported by other researchers in saturated soils. Moreover, C c ∗ and C α also increase with decreasing suction. The relationship between C c ∗ and C α is linear in the considered stress range and the slope of this linear relationship ( C α / C c ∗ ) increases with decreasing suction. Finally, a logarithm function is established between C α ∗ / C c ∗ and suction s , which represents the coupling of suction, creep and stress of GMZ01 bentonite.