Abstract: Using self-developed high-pressure oedometer system, we performed one-dimensional consolidation tests (OCT) on reconstituted clay samples at vertical pressures from 0.25 MPa to 12 MPa. In addition, we carried out isotropic consolidation tests (ICT) on the same samples with confining pressures from 0.3 MPa to 2.5 MPa using triaxial apparatus. The test results indicate that all the consolidation curves obtained from OCT have notable secondary consolidation portion, and the secondary consolidation coefficient of remolded clay changes nonlinearly with increasing consolidation pressure. Specifically, when the consolidation pressure is less than 2 MPa, secondary consolidation coefficient decreases significantly with increasing consolidation pressures. but it is almost unchanged for the case of consolidation pressure above 2 MPa. The secondary consolidation coefficients obtained from ICT are much less than those from OCT, and the change of secondary consolidation coefficient with confining pressure obtained from ICT is different from that from OCT. Moreover, the microscopic analyses of the test results show that the physical mechanism underlying secondary consolidation deformation of clay at high pressure is different from that at low pressure. At low pressure, the secondary consolidation deformation mainly results from the relative slip between clay particles while the creep of adsorbed pore water contributes much to the secondary consolidation deformation of clay at high pressure. Moreover, it seems that the deviatoric stress has a dominating influence on the secondary consolidation deformation of clay at low pressure while it has little effect at high pressure.

Key words: clay, high pressure, secondary consolidation coefficient, test, physical mechanism