Effect of Sediment Depth on the Compression Behavior and Collapse Behavior of Intact Loess

Comparative study of the water retention behavior, unsaturated compression behavior and collapse behavior of the sediment depth of 10m and 30m intact loess deposited in the Heifangtai area. To investigate the effect of stress and hydraulic history on the water retention behavior, unsaturated compression behavior and collapse behavior. Mercury intrusion porosimeter (MIP) and scanning electron microscopy (SEM) were used to evaluate the microstructure of two different sediment loess. The result shows that the sample of HFT30 m has a greater air entry value than the sample of HFT10 m, this is because HFT30 m loess has a smaller dominated size for large pores than HFT10 m loess and hence exhibits a larger (air entry value, AEV). For the compression behavior, the HFT30 m loess has larger compression index than the HFT10 m. The yield stress increased with the increase of suction, however, the increased rate of yield stress decreased obviously with the further increase of suction. When the suction was larger than 100kPa, the yield stress of HFT10 m was smaller than that of HFT30 m; however, with the suction decreasing to smaller than 100kPa, an unexpected result is observed that the yield stress of HFT30 m was smaller than that of HFT10 m. Overall, the experiment results from compression tests on the two unsaturated loess samples with different depths demonstrated that the effect of suction, saturation and overburden pressure was of great significance to the compression behaviors of unsaturated intact loess. For the collapse behavior, both the HFT10 m loess and HFT30 m loess exhibit that the collapse volumetric strain increases with the increase of net vertical stress, and then decreases slightly with the increase of net vertical stress. Furthermore, the HFT10 m behaved a larger collapse volumetric strain under the same net vertical stress than HFT30 m loess.