An experimental investigation on the secondary compression of unsaturated GMZ01 bentonite

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/cm3. 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 Cc∗ and secondary compression index Cα were defined. Relationships between Cc∗, Cα, vertical stress and suction were analyzed. It is observed that both Cc∗ and Cα increase linearly with increasing vertical stress, which is different from the convex relationship reported by other researchers in saturated soils. Moreover, Cc∗ and Cα also increase with decreasing suction. The relationship between Cc∗ and Cα is linear in the considered stress range and the slope of this linear relationship (Cα/Cc∗) increases with decreasing suction. Finally, a logarithm function is established between Cα∗/Cc∗ and suction s, which represents the coupling of suction, creep and stress of GMZ01 bentonite.