The dynamic responses of undisturbed loess to seismic excitation: Centrifugal shaking table test

Undisturbed loess is highly sensitive to humidity and vibration. It is prone to serious seismic subsidence disasters under seismic loads. The dynamic responses and failure mechanisms of loess were investigated in centrifugal shaking table tests at different moisture contents and with different excitation amplitudes. The results show a significant acceleration amplification effect, especially at greater peak seismic accelerations and with drier soil. With the increase of excitation amplitude and moisture content, the degree of seismic settlement deformation becomes more significant and the risk of foundation instability increases. The shear action of seismic loading leads to the collapse of the undisturbed loess pore structure and the gradual densification of the skeletal structure, resulting in sudden additional settlement. With the loss of primary structure and the formation of secondary structure, the deformation process of seismic settlement of loess can be divided into four stages: elastic vibration, local shear, yield damage and deformation stabilization. The seismic subsidence damage form of undisturbed loess is dominated by vertical deformation and accompanied by the development of tension cracks caused by uneven settlement. The crushing phenomenon is serious in the local area, and may even trigger penetrating fracture damage.