Collapsibility and microscopic mechanism of intact loess at different depths in Xining area

The collapsibility of the intact loess at different depths in Xining area is studied through the laboratory immersion compression tests. Combined with the scanning electron microscopy (SEM) and the particle and crack image recognition and analysis system (PCAS), the relationship between the collapsibility of intact loess and the internal microstructure under different overburden pressures is analyzed. The results show that the large pores, overhead structure and a large number of direct contact points are the internal conditions of loess with collapsibility in this region. With the increase of the buried depth, the collapsibility tends to decrease gradually under the same overlying pressure and immersion condition. However, at the same buried depth, within a certain range, with the increase of the overlying pressure and the given immersion condition, the collapsibility of loess is obviously improved, which proves that the external load and immersion are the external conditions of collapsibility of loess.