Dynamic properties of freezing–thawing muddy clay surrounding subway tunnel in Shanghai

Relying on the application of the artificial freezing method on subway tunnel construction, a group of cyclic triaxial tests were carried out to study the dynamic behavior of freezing–thawing saturated muddy clay under step cyclic loading. In terms of practical engineering, the freezing temperature and loading frequency were taken into account to indicate how the influencing factors affect the dynamic elastic modulus. The results indicate that the dynamic elastic modulus displays ladder-type drops with the increasing dynamic step loading amplitude. The dynamic elastic modulus increases with the growth of loading frequency. Freezing temperature has slight influence on dynamic elastic modulus, but the freezing and thawing cycles can lead to rearrangement of the soil structure. The dynamic elastic modulus increases with the growth of loading frequency. The fluctuation of dynamic elastic modulus is the most serious in the first stage and tends to be stable in the following steps. The fluctuation of dynamic elastic modulus of unfrozen soil is greater than freezing–thawing soil in the first stage. Based on a hyperbolic model, the dynamic constitutive behavior of freezing–thawing soil was investigated.