Investigation of creep characteristics and microscopic mechanism in cemented-soil subjected to freeze–thaw during artificial ground freezing

Cement reinforcement can effectively mitigate the frost heave and thaw settlement in soft clay during artificial ground freezing. Generally, soft clay has strong creep characteristics, which is also the main factor influencing the construction safety in coastal area. However, the mechanism of freeze–thaw action with cement reinforcement on the creep is really unclear. In this paper, the creep characteristics of cemented-soil after freeze–thaw have been investigated through triaxial creep test, and the micro-mechanism has been explored by Scanning Electron Microscopy (SEM) test and PFC numerical simulation. Three quantitative parameters of porosity, average particle size, and particle roundness have been extracted from SEM pictures. The results showed that creep deformation of cemented-soil is higher after freeze–thaw than before, with an increase as the freezing temperature drops. When combining freezing with cement reinforcement, there is an overall decrease in the creep behavior. It was observed from numerical simulation that the slip deformation of cemented-soil particles is generated from top to bottom and from outside in. Moreover, the porosity of cemented-soil increased from 24.5 to 28.5%, the particle roundness decreased from 2.11 to 1.75, while average particle size decreases from 16.67 to 13.88 μm during creep process. These shifts are explained by particles sliding and disordering, with debris migrating to the interior of pores. The results provide a scientific reference for the development of underground space in the coastal area.