Collapsibility and seismic settlement of loess

Loess collapsibility and seismic settlement have proven to be costly geotechnical hazards in China. Since collapsibility assessment and mitigation are now conventional practices in Chinese design codes, some previous efforts have been made to relate collapsibility and seismic settlement in order to simplify assessment of the latter. However, these works have neglected mechanical difference between the two phenomena. In this study, the similarity and difference between collapsibility and seismic settlement of loess are analyzed, which shows that both are based on the metastable microstructure of loess, but their triggering mechanisms are different. Collapsibility is primarily driven by suction loss, whereas seismic settlement is caused by shear failure of the loess matrix during dynamic loading, though both of them result in collapse of trellis structure pores. Consequently, the lack of a common mechanism demonstrates there is no tenable physical basis to relate collapsibility and seismic settlement.