Experimental Study On Dynamic Characteristics Of Remolded Clay With Different Consolidation Degree Under Subway Loading

The underlying soil possesses the nature of variation in consolidation degree before subway operation, which will result in the change of dynamic characteristics as well as the differential settlement. Excessive deformation can cause serious traffic congestion or accident. Dynamic characteristics of soil under cyclic loading include:dynamic pore water pressure, dynamic strength, dynamic strain, etc.Hangzhou saturated soft clay is tested in dynamic triaxial tests system to find the effect of degree of consolidation, consolidated stress and cyclic stress ratio on the dynamic properties, trying to find a more practical significance of dynamic model. The main contents of this paper includes: dynamic pore pressure, dynamic stiffness, dynamic deformation and long-term settlement of saturated clay under subway loading. The main innovation and conclusions are as follows:(1) New dynamic models considering the degree of initial consolidation are proposed on the basis of existing research findings, in which the pore pressure lag during the test is considered in pore pressure model. In order to get a more realistic dynamic model, the drained and undrained conditions are compared in the experimental design.(2) The higher the consolidation degree, the slower pore pressure increases. Furthermore, the pore pressure will be stabilized at a lower level with the increment of cyclic times. Under different drainage conditions dynamic pore water pressure will show different trends, taking the drain volume into consideration will lead to more desirable results when predicting the pore pressure and long-term settlement of the tunnel.(3) Under the same consolidation degree the dynamic stiffness will increases with the increasing of cyclic numbers due to compaction of soil particles, as long as the cyclic stress is small enough. The soil stiffness will change from hardening to softening with the cyclic stress ratio increasing gradually, and the higher of the dynamic stress ratio, the greater of the degradation of stiffness. When the cyclic stress ratio under the same level, dynamic stiffness will degrade gradually intensified with the reduction of consolidation degree.(4) The dynamic strain will increases with the increasing of cyclic numbers and decreases with the decreasing of consolidation degree. We can get a more practical model of long-term settlement in predicting long-term settlement of soil under train load, if we consider partially drained during vibration and compared with the measured data to corrected test model.