Abstract:

The characteristics of load–settlement curve of gravel soil and the collapsibility and collapsible mechanism of gravel soil were studied based on the results from plate loading tests under different work conditions, routine soil tests and soluble salt tests. The study shows that when the gravel soil stabilized under the load of 200 kPa, then immersed in the water and loaded to 400 kPa, the load-settlement curve is a broken curve, and can be obviously divided into three phases: compressive deformation phase，collapsible deformation phase and composite deformation phase. The gravel soil with 4m thick has collapsiblity and its collapsibility is uneven. The collapsible mechanism of gravel soil is due to its loose single-grain open structure. There is open pore in the frame grains and some of open pore is filled with sandy grain aggregation; frame grains are linked together with point-to-point contact or mainly connected with cement consisting of clay particle, clay minerals and soluble salt. During the process of ponding and loading, the film water around clay partvicle is becoming thicker, the clay minerals expands itself and soluble salt dissolves, so as to lead the loss of the cement strength and destabilization of the structure; and thus the gravel soil collapses.

Key words: gravel soil, ponding plate loading test, collapsibility, collapsible mechanism