Abstract
The use of artificial freezing can change the mechanical properties of marine clay. In the construction of cross passages in metro tunnels in which the artificial ground freezing (AGF) method is applied, freeze–thaw circulation and cyclic loading could weaken the engineering properties of the clay, thus resulting in differential settlement. In this paper, the authors studied the dynamic properties of frozen–thawed soils under cyclic loading, with the help of dynamic triaxial testing. According to the dynamic triaxial test results and the images from scanning electron microscopy (SEM), the authors explained the weakening effect of both the freeze–thaw cycle and dynamic loading on soft soil. After freezing, the number of large pores increased. In addition, after cyclic loading, the pore structure of the soil showed a tendency towards compaction, which led to the large pores breaking into small ones. Subsequently, the potential reasons for the change of macroscopic dynamic characteristics were explained from a micro-scale point of view.
Highlights
The artificial ground freezing (AGF) method is normally used for the construction of tunnels in soft soil areas, especially in coastal regions such as Shanghai in China
A further study on the dynamic properties of frozen–thawed soil is necessary, as this can provide the basis for controlling long-term settlements after AGF-method construction
From the scanning electron microscopy (SEM) images, it is found that the nature of the weakening effect of the dynamic characteristics, such as pore pressure and axial strain before and after the freeze–thaw cycle, came froJm
Summary
The artificial ground freezing (AGF) method is normally used for the construction of tunnels in soft soil areas, especially in coastal regions such as Shanghai in China. A further study on the dynamic properties of frozen–thawed soil is necessary, as this can provide the basis for controlling long-term settlements after AGF-method construction. After the freeze–thaw cycle, the porosity ratio of dense soil increased, while the porosity ratio of loose soil decreased. Several simulation models were developed to explore the mechanism of frozen soil [19] and evaluate the thaw settlement after artificial ground freezing [20]. He et al [21] compared various dynamic responses of thawing soil and undisturbed soil using the numerical simulation method
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