Experimental study on dynamic cumulative axial-strain performance of freezing-thawing saturated sandy silt

Depending on artificial freezing method adopted in subway tunnel construction, a series of frost heave and stress-controlled cyclic triaxial tests were conducted on saturated freezing-thawing sandy silt to investigate their unconfined frost heave performance and plastic strain behavior. In terms of practical engineering, this study focuses on four significant influencing factors which are freezing temperature, dynamic stress amplitude, cell pressure and loading frequency. The results indicate that the remolding-stripping device provide an effective way for remolding soil sample, particularly dense sand and silt. Besides, the freeze-thaw action can truly has influence on the unconfined frost heave rate, and undisturbed or remolded soil with higher freezing temperature possesses smaller volume frost heave rate. In addition, the value of freezing temperature has significant influence on strain of remolded saturated freezing-thawing sandy silt with higher freezing temperature possesses larger accumulated axial strain, the accumulated plastic strain decreases remarkably with the increasing of dynamic stress amplitude and cell pressure, the loading frequency has considerable effect on accumulated axial strain of soil that is lower frequency can generate larger accumulated plastic strain. Finally, an improved semi-logarithmic empirical formula of cumulated permanent axial strain on freeing-thawing saturated sandy silt is proposed, and verified by experimental data, which could exactly forecasting development trend of dynamic permanent axial strain.