Effects of reconsolidation on cyclic deformation behaviours of a kaolin clay

Subgrades may be subjected to intermittent cyclic loads such as traffic loads. Under these loading conditions, excess pore water pressure can accumulate in clayey soils during cyclic loading period and dissipate during resting time. The deformation behaviour of clayey soil after reconsolidation process may be different from that under consecutive cyclic loading. A series of undrained cyclic triaxial tests, including reconsolidation process between cyclic loading stages, were performed on kaolin clay. The axial strain accumulation, excess pore water pressure accumulation, deviatoric stress–strain loop and resilience modulus under different cyclic stress ratios, initial confining pressures and degrees of reconsolidation were discussed and presented. Test results show that the reconsolidation process has significant effects on the deformation characteristics of clayey soil. The coupling effects of change of void ratio and effective mean stress result in a non-monotonic relationship between normalised total axial strain and degree of reconsolidation. In addition, an increase in the degree of reconsolidation leads to an increase in the normalised excess pore water pressure increment during 2nd cyclic loading stage, regardless of cyclic stress ratio and initial confining pressure. Furthermore, the steady resilience modulus at the end of each cyclic loading stage depends on the effective cyclic stress ratio and initial confining pressure, irrespective of reconsolidation process.