Abstract: To investigate the rate-dependent deformation characteristics of subgrade compacted clay of high-filled embankment, a series of CD triaxial shear tests on the unsaturated compacted clay with different compaction degrees is carried out under different loading rates and confining pressures, and the shear strength parameters under different working conditions are examined. A method is proposed for indirectly measuring the volume change of unsaturated compacted clay, i.e. using the confining pressure controller of GDS saturated static triaxial system to obtain the volume change. The experimental results show that the strength and deformation of compacted clay shows significant time-dependent characteristics. At the greater loading rate, the shear strength is higher and the over-consolidated properties are stronger, and the value of cohesion c increases more quickly but the value of the internal friction angle increases more slowly. Under low confining pressure, compacted clay shows dilatant and softening behavior. As the compacting degree increases, shear dilatancy and strain softening become more and more pronounced, shear strength index c increases quickly, whereas increases slowly. An elastic-viscoplastic constitutive model based on the subloading yield surface is adopted to describe the rate-dependent deformation characteristics of the over-consolidated compacted clay. The predictions of the proposed model are in good agreement with the experimental data, showing that the proposed model is suitable for analyzing the long-term settlement of high-filled embankment.

Key words: compacted clay, rate sensitivity, over-consolidation, shear strength, elastic-viscoplastic, constitutive model