Experimental study on effect of different drainage conditions on dynamic characteristics of soft clay under different degrees of consolidation

The underlying soil, which is disturbed by subway tunneling, will show a different degree of consolidation which is associated with the strain of soil, and thus cause uneven settlement. Hangzhou saturated soft clay is studied using a dynamic triaxial test system to find the effects of drainage conditions, degrees of consolidation and cyclic times on dynamic pore pressure and strain. A new strain-degradation model considering degrees of initial consolidation, cyclic stress ratios and drainage conditions is proposed on the basis of the experiments and the existing research findings. The results show that the higher the degree of consolidation, the slower the increase of the pore pressure. Furthermore, the pore pressure will be stabilized at a lower level with the increment of cyclic times, and the law of pore pressure under drainage conditions may be obtained from undrained tests. The dynamic strain increases with the increase of the cyclic times and decreases with the decrease of the degrees of consolidation. The proposed strain model considers the drainage of the soil during the loading cycles, and it can well simulate dynamic strain changes under different degrees of consolidation.