Discussion on the change rule of different characteristic parameters with Depth in expansion soil graben slopes

Expansive soil due to wet expansion and dry contraction of engineering properties, resulting in the stability of the riffle slope, has been one of the key issues in the expansion of soil area earthworks; this paper, through the three representative riffle slope site field visits and indoor tests, respectively, from the dry bulk weight, unconfined compressive strength, three-way expansion force and expansion with the change rule of the Depth of the law to be explored. The three-way expansion force test shows that the extension and proximity direction of the horizontal expansion force are the same. The vertical direction is greater than the horizontal direction, and its ratio is about 0.5. Further analysis of the relationship between the characteristics of the parameters with the Depth can be seen: the surface soil indicators are more varied, between 0.5-1.0 m, the soil layer dry density is small, the expansion of the soil wet expansion and drying shrinkage is significant, and the unconfined compressive strength is close to or has reached the lowest value; expansion force and expansion volume test indicators along the Depth of the graben slope, the expansion force and expansion volume test indicators are more varied. Expansion force and expansion amount test indexes change along the Depth of the riffle slope but remain unchanged after 2.0 m. Therefore, the damage of the expansion soil riffle slope mainly occurs in the soil layer near the Depth of 1.0 m, which is manifested explicitly as a failure to adapt to the change of stress in the soil and the inability to adjust to the atmospheric natural camping force.