Dynamic Properties of Silt-Based Foamed Concrete as Filler in Subgrade

To investigate the dynamic response of silt-based foamed concrete as filler in subgrade, this paper conducted staged cyclic loading experiments to examine its dynamic properties. Influence factors such as wet density and silt content were also addressed in experiments. The results of tests indicated that the hysteretic curves of silt-based foamed concrete presented obvious elastoplastic characteristics, and the dynamic stress–cumulative strain curves have a strain-hardening phenomenon. Dynamic strength increased a mean level of 65% when density increased by an average of 100 kg/m3 at the range of density 600–800 kg/m3. Meanwhile, the dynamic strength decreased by an average of 14.2% if silt content increased by a mean of 10%. Furthermore, the addition of silt transformed the pore structures from uniformly distributed sphericity into irregular combined bubbles with larger diameters. Besides, during the staged cyclic loading process, it was deduced that dynamic elastic modulus of material has a variation with cycles, but can be basically assumed constant in tests. Thus, the dynamic stress–cumulative strain curves of silt-based foamed concrete subjected to staged cyclic loads were derived based on the Ramberg-Osgood equation. The parameters of the Ramberg-Osgood equation were also analyzed according to the test data. Finally, the damage variable expressions versus plastic strain and cyclic numbers were established respectively. It was found that density and silt content can significantly affect damage evolution.