EFFECTS OF TEMPERATURE FLUCTUATION ON STRUCTURAL EVOLU￣TION OF INITIAL LOESS DEPOSITS

The present-day loess structure is gradually formed with the process of initial accumulation of loess particles and the later lossification. The climate is typically dry in the period of loess accumulation and the initial loess deposit(ILD)suffers from daily and seasonal temperature fluctuations,which evidently leads to structural evolution of ILD. However,the mechanism behind is still unclear. In this study,ILD is reconstructed in the laboratory and physical simulation with temperature fluctuation is carried out. Ambient temperature,soil temperature,vertical deformation and structure of top surface of soil sample are monitored with thermocouple temperature sensors,laser displacement sensors and an industrial camera of high-resolution. The results show that both soil temperature and vertical deformation of soil sample fluctuate with the ambient temperature,but lag behind. The vertical deformation exhibits a synchronous fluctuation with the soil temperature. With temperature cycles,the soil sample keeps contraction,and the soil sample experiences elastic-plastic deformation and then elastic deformation. Compared with the effects of water and overlying load,the deformation and structure disturbance of ILD due to temperature fluctuation are minimum(about 0.25%). This indicates that temperature fluctuation plays a noncrucial role in the formation of present-day loess structure.