Equivalent seismic behaviors of artificial frozen-thawed soft clay with a new reduction factor of shear stress

Abstract

The artificial ground freezing (AGF) technique is widely used in the construction of underground structures, and the deformation of soft clay is more significant after freezing-thawing cycles. Moreover, many earthquake disasters indicate that the engineering in soft soil areas experience huge risks to seismic fortification. In this paper, the inversion formula of seismic acceleration time history for different peak ground accelerations (PGAs) in the frequency domain was derived. The maximum peak acceleration and maximum dynamic shear stress in the undisturbed and frozen-thawed soft clay sites were analyzed by DEEPSOIL. The reduction factor of dynamic shear stress suitable for the clay field was calculated to provide basic parameters for the cyclic triaxial tests considering different confining pressures, dynamic stress amplitudes and loading frequencies. The ground motion acceleration of soft clay sites has an amplification effect, and that of frozen-thawed soft clay sites is more obvious. The reduction factor of shear stress for the clay site is overestimated by the liquefaction resistance shear stress method. The axial strain of the frozen-thawed clay reaching failure is less than that of the undisturbed clay. Under the same seismic shear stress, the development of the excess pore water pressure in frozen-thawed clay is more significant than that in undisturbed clay.